Complementary Safety Assessment for the Nuclear Laboratories at the Joint Research Centre Institute for Reference Materials and Measurements

Report of the evaluation made in the frame of the Belgian Stress Tests

2012

European Commission Joint Research Centre Institute for Reference Materials and Measurements Contact information Andreas Fessler Address: Joint Research Centre, Institute for Reference Materials and Measurements, Retieseweg 111, B-2440 Geel E-mail: [email protected] Tel.: +32 145 71 690 Fax: +32 145 84 273 Pierre Kockerols Address: Joint Research Centre, Square de Méeus 8, 1050 Bruxelles E-mail: [email protected] Tel.: +32 229 84 214 Fax: +32 229 50 146 http://xxxx.jrc.ec.europa.eu/ http://www.jrc.ec.europa.eu/

This publication is a Technical Report by the Joint Research Centre of the European Commission. Legal Notice Neither the European Commission nor any person acting on behalf of the Commission is responsible for the use which might be made of this publication. Europe Direct is a service to help you find answers to your questions about the European Union Freephone number (*): 00 800 6 7 8 9 10 11 (*) Certain mobile telephone operators do not allow access to 00 800 numbers or these calls may be billed.

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Preamble In decision of the European Council after the nuclear accident in Japan, the European nuclear power plants were submitted to "stress tests" in order to check their robustness against extreme events. In Belgium, the coordination was done by the Federal Agency for Nuclear Control (FANC). The reports for the Belgian nuclear power plants have been issued and reviewed by FANC end of 2011 and meanwhile submitted to the EU peer review. In June 2011, the Belgian Parliament has requested that a similar assessment by stress tests would be performed for all major non-power nuclear installations. By letter dd. 4 July 2011 the FANC has introduced this request to all operating class 1 installations. A guideline was issued describing the approach which was expected to be followed. A meeting was organised to provide additional information to the involved parties. The realisation of the study was further subject to regular follow-up. FANC has requested that the final stress test report would be established for 30 June 2012. In order to facilitate the evaluation of the completeness and coherence of the assessments made by the installations, FANC recommended a format for the content of the report. The present report relates to the stress test assessment made by the Institute for Reference Materials and Measurements from the European Commission’s Joint Research Centre (JRC-IRMM). The stress test studies have been coordinated by the ‘‘health physics’’ service of JRCIRMM, with the support of technical, scientific and administrative staff and external contractors (Vinçotte Nuclear Safety and Laborelec). Regular contacts have been established with the other nuclear sites of the region Mol-Dessel-Geel (SCK•CEN, Belgoprocess and FBFC). Advices and support has been provided by NIRAS/ONDRAF, the Royal Observatory of Belgium, the Fire Brigades of the communities of Mol, Geel and Wuustwezel and the COMOPSAIR Ops Support Fire Fighting of the Belgian Air force. The report has been submitted for review to the fire brigades of Geel and Mol.

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Acknowledgements The JRC-IRMM would like to acknowledge all persons who contributed to the elaboration of this assessment. In particular, the JRC-IRMM is grateful for the information and advices provided on a voluntary basis by Cpt. F. Kenis from the fire brigade of Mol; Cpt. E. Goossens and Lt. B. Cools from the fire brigade of Geel, Cpt. E. Janssens from the fire brigade of Wuustwezel, Adj.Ch. M. Eeckhout from COMOPSAIR, Belgian Air Forces, L. Wouters from NIRAS/ONDRAF and K. Vanneste and K. Verbeeck from the Royal Observatory of Belgium. Specific acknowledgement is also made to Cpt. F. Kenis and Cpt. E. Goossens from the fire brigades of Mol and Geel for their multiple advices and support and the review of the report.

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Content Preamble Preamble Acknowledgements Content 0 Introduction 1 General data about site and the installations 1.1 Brief description of the site characteristics 1.2 Main characteristics of the nuclear installations 1.3 Scoping of nuclear installations to be included in the Stress Test 1.4 Relevant safety functions of nuclear installations 1.4.1 Prevention of criticality 1.4.2 Cooling 1.4.3 Confinement of radioactivity 1.5 Scope and main results of Probabilistic Safety Assessments

2 Earthquake 2.1 Design basis 2.2 Evaluation Evaluation of margins 2.2.1 Range of earthquake leading to severe damage to installation 2.2.2 Range of earthquake leading to loss of confinement integrity 2.2.3 Earthquake exceeding the design basis earthquake for the plant and consequent flooding exceeding design design basis flood

3 Flooding 3.1 Design basis 3.2 Evaluation of margins: level of flooding and consequences

4 Other extreme events 4.1 Very bad weather conditions 4.2 Bush or forest fire 4.3 Terrorist attacks (aircraft crash) 4.4 Site specific impacts caused by toxic gases

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4.5 Site specific impacts caused by explosive gases and blast waves 4.6 Site specific impacts caused by external attacks on computercomputer -based controls and systems

5 Loss of electrical power 5.1 Loss of offoff- site power 5.2 Loss of of offoff- site power and of onon- site backback- up power sources 5.3 Loss of offoff- site power and loss of the ordinary back up source, and loss of any other diverse back up source 5.4 Loss of primary ultimate heat sink 5.5 Loss of the primary ultimate heat sink and ‘‘alternate ‘‘ alternate heat sink’’ sink’’ black-- out 5.6 Loss of the primary ultimate heat sink, combined with station black

6 Severe accident management 6.1 Organisation of licensee to manage the accident and possible disturbances 6.1.1 Organisation planned 6.1.2 Po Possible ssible disruption with regard to the measures envisaged to manage accidents and associated management 6.2 Organisation in case of a severe accident 6.2.1 Accident management measures for managing the consequences of a forest fire 6.2.2 Acciden Accidentt management measures and installation design features for protecting confinement integrity 6.2.3 Accident management measures currently in place to mitigate the consequences of loss of containment integrity and to reduce releases to the environment. 6.2.4 6.2. 4 Specific points for each stage 6.2.1, 6.2.2 and 6.2.3

7 Conclusions and proposal for action plan

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0 Introduction The Institute for Reference Materials and Measurements (IRMM) has its address on the community of Geel in the Antwerp Province, Flemish Region, North of Belgium. More precisely, Geel is situated in a typical nature environment called the ‘‘Kempen’’. The IRMM belongs to the Joint Research Centre (JRC) of the European Commission, which mission is to provide an independent scientific and technical support for the European policies. The IRMM was founded in 1957 under the Treaty of Rome (The treaty establishing the European Atomic Energy Community, article 8) and started operation in 1960 under the name of the ‘‘Central Bureau for Nuclear Measurements (CBNM)’’. In 1993 it was renamed to reflect the new mission of the institute, covering a wider range of scientific domains including non nuclear fields like food safety and environmental protection. Presently, about one third of the IRMM research is dedicated to nuclear domains, two third to non nuclear. IRMM’s management system is certified according to ISO 9001, ISO 14001 and OHSAS 18001. Over the more than fifty years of its existence, the number facilities on the IRMM site have expanded to host new non nuclear and nuclear activities. Older facilities and the infrastructure have been gradually renewed with the same objective. Currently there are 23 buildings of various dimensions on the site. In order to plan the future developments with the horizon 2020, a site master plan was established. According to this plan, it is foreseen to design and construct new buildings. More particularly, in relation to the present report, a new entrance building and a new nuclear facility in replacement of existing nuclear laboratories are envisaged. Safety assessments of the nuclear facilities have been performed at the licensing of the different buildings and since then on a continuous basis, in agreement with the nuclear inspection body (Corapro, later Controlatom) and nowadays the Federal Agency for Nuclear Control (FANC). More recently, the IRMM has been requested by Royal Decree of 8 February 2010 (FANC 8677/AM-12-131) to perform a consolidated ‘‘ten yearly assessment’’ of the nuclear safety for all its nuclear installations. The requirement is in line with the approach put in place for the other main nuclear installations in Belgium and the assessment follows a standardised methodology (IAEA Safety Guide NS-G-2.10). A final report for IRMM must be issued by 1 December 2012. The ‘‘stress tests’’ which are the object of the present report have been requested later, in complement to the on-going ten-yearly assessment, as a consequence of the accident in Japan in 2011. The report is structured according to the format prescribed by FANC and covers the study of the possible consequences of all types of severe external events, from natural and human origin, including also malevolent actions: Section 2: earthquake Section 3: flooding Section 4: other extreme events, including: 4.1 extreme weather conditions

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4.2 bush and forest fire 4.3 terrorist attack 4.4 impacts of toxic gases 4.5 impacts of explosive gases and blast waves 4.6 impacts of attacks on computer-based control systems Section 5: loss of electrical power Section 1 provides descriptive information about the IRMM site and the installations. Section 6 deals with severe accident management and section 7 concludes on the remedial measures that can be envisaged and proposes a dedicated action plan. For practical reasons, these envisaged remedial measures will be categorised as follows: -

short term and medium term measures on the existing infrastructure

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organisational measures

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long term measures to be considered at the design of the new installations.

As agreed with FANC, the sensitive information and the details of the assessments in relation to possible malevolent actions are integrated in a classified addendum to this report.

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1 General data about site and the installations 1.1 Brief description of the site characteristics characteristics Location IRMM site The IRMM is situated in the Antwerp Province, North of the city of Geel, in the vicinity of the N118 main road between Geel and Retie. The access street and the address is on the community Geel, but the site area is fully located on the community of Mol.

Figure 1.1: location of the IRMM site at the North of the Geel city

Figure 1.2: IRMM site, main access street and surroundings The site was initially installed in a forest area consisting of mainly pine trees. The ground belongs to the SCK•CEN and is rented under a long term lease contract.

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The main surrounding installations are the ‘‘site 2’’ from VITO (‘‘Vlaams Instituut voor Technologisch Onderzoek’’) including also the Innotek environmental technology building (‘‘Technologiehuis voor Milieu en Energie Mol’’). The domain of the European school borders the site perimeter as well. In the Southern part of the IRMM site the district called ‘‘Europawijk’’ gradually expanded since the creation of the institute. Few houses and apartment buildings were also built on the Northwest area close to the site.

lay--out and buildings Site lay The fenced area of the site has a total surface of 38 ha. Part of the surface is occupied by building constructions and connecting roads in between. There are in total 23 buildings of variable dimensions: -

Research laboratories, accelerators and facilities for production reference materials: -

-

Storage buildings: -

-

060 Infrastructure and site management building 120 Infrastructure and site management building, annexes 090 Medium voltage building and (outside) the transformers 091 Generators building 140 Safety building with fire brigade garage 170 Pumping station for effluents and sewage 180 Heating building1

Administrative and site logistics buildings: -

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190 Certified Reference Materials storage 072 Chemical storage 071 Hazardous waste store 070 Radioactive waste store

Buildings for infrastructure and technical support: -

-

010 Main building 020 Van de Graaff accelerator 040 Mass Spectrometry building 050 Linear accelerator 110 Food and Feed Analysis building 130 Certified Reference Materials building 200 Reference Materials Processing building

030 ‘‘Acomal’’ offices building 080 Entrance building 081 Cafeteria 100 Conference building

The 180 Heating building, although located in the centre of the site, is owned and managed by VITO; the heating installations provide hot water to the VITO site 2 buildings and part of the IRMM buildings.

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Figure 1.3: map of the IRMM site with with buildings

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The IRMM master plan (‘‘site development plan’’) established in 2011 outlines the future of the site and the new installations to be constructed or refurbished with the perspective of horizon 2020. Following this plan, two new buildings are currently in the design phase: -

210 Administration building

-

222 Safety, health environment and security (‘‘SHES’’) building.

The construction of the administration building should start in 2012. The construction of the 222 SHES building is planned for 2013-2014. The old 030 Acomal and later the 140 Safety building and 080 Entrance building will be demolished, as their functionalities will be integrated in the new buildings. The 222 SHES building will host the future Alarm Centre for the surveillance of the site. In the longer term, a new nuclear building is planned to replace the nuclear installations of the 040 Mass spectrometry building and 010 Main building. Most of the buildings are surrounded by parking places and garden areas. But on most of the site area, the vegetation has been kept unchanged, mainly dominated by pine trees. In 2009 a ‘‘forest management plan’’ was established, as requested by the Flemish environmental regulation. The plan foresees in a gradual removal of pine trees to allow the original vegetation (oaks and birches) to expand again. This is in line with the common environmental development approach pursued by the Flemish region.

Staffing and Organisation There are about 320 staff working on the IRMM site (core staff and visiting staff) and approximately 50 contractors from external companies. The IRMM organisation is structured in four scientific units for the management of the research activities: -

the Nuclear Physics unit

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the Reference Materials unit

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the Food Safety and Quality unit

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the Knowledge Transfer and Standards for Security unit.

The Site Management unit provides the technical support. The staff of the Resource Management unit for the administrative support and the staff of the ICT unit who are working on the site are directly linked to the JRC headquarters in Brussels. The legal tasks of the ‘‘Internal Service for Prevention and Protection’’ (Belgian labour safety regulation, Codex) and ‘‘Health Physics service’’ (Belgian nuclear regulation, ARBIS/RGPRI), as well as all tasks related to the regulations and obligations on safety, environmental protection, security, safeguards, transports, fire protection, radioactive waste and nuclear decommissioning are managed by the Safety, Health, Environment and Security (‘‘SHES’’) sector, directly linked to the Institute Director. An integrated management system ISO9001-ISO14001-OHSAS18001 has been introduced at IRMM and certified by the German authorised body TÜV Nord in 2007. The system developed at IRMM integrates both nuclear and non nuclear aspects and allows maximising the synergies between quality, safety and environmental management.

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1.2 Main characteristics of the nuclear installations Nuclear laboratories of the 040 Mass Spectrometry building The Mass Spectrometry building (‘‘MS1’’) has been in use as a laboratory for the preparation and measurement of radioactive reference materials since the start of operations of the IRMM (1960). Part of the controlled area laboratories (rooms 201 to 212) have been denuclearised in the 1980’s.

Figure 1.4: MS building

Currently, the main laboratories of MS1 host four mass spectrometers for the measurement of uranium and plutonium samples. In some laboratories equipment is installed for the preparations of the reference material spikes. Most of the activities are performed in glove boxes or in fume hoods, depending on the contamination risk. Currently there are 32 glove boxes installed in MS1. The mass of the handled samples varies usually from a few micrograms to less than one gram.

In 1976 the building was expanded with a new wing (‘‘MS2’’) for the preparation of samples and targets for the accelerators. These activities are also performed in glove boxes or in fume hoods; currently there are 33 glove boxes installed in MS2. In 2000 two rooms of MS2 were transformed in a secured area for the storage in safes of material in reserve. In 1977 an additional room (‘‘room 101’’) was commissioned for the storage of radioactive waste and later transformed in a buffer storage space for transport containers mainly for the dispatch of radioactive reference materials. The room doesn’t contain specific equipment.

Figure 1.5: map of the MS building with controlled areas MS2, MS1 and room 101

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Other nuclear Installations on the IRMM site Radio-metrology installations of the 010 Main building: Since 1960 activities with radioactive substances have been carried out in the 010 Main building. These activities are now restricted to a small controlled area. In the two laboratory rooms of this area, radioactive reference sources are prepared with alpha and beta-emitting nuclides. Besides, there is a storage room for the sources, a weighing room and a store for waste. The activity of the manipulated sources is commonly in the range of 1 Bq to 1 MBq. In a number of annexed laboratories small sources can be measured and for this reason the rooms are classified as ‘‘supervised area’’.

050 LINAC building and linear accelerator: The ‘‘GELINA’’ (‘‘Geel Linear Accelerator’’) is a pulsed-beam linear electron accelerator (LINAC) in combination with a metallic uranium target, serving as a neutron source. The accelerator produces electron beams and operates in a pulsed mode. Both moderated neutron beams and fast neutron beams can be generated. The first experiments with GELINA started in 1965. In 1977 the accelerator was reconfigured with an increase of its energy. Over the years, adaptations have been made to improve the performances and renew the components. The accelerator and ion source are located in a gallery; the target room contains magnets for the optimisation of the beam and the target. The rooms are shielded by thick walls of 2.5 m width (gallery) to 3.5 m (target room). Besides, the modulator hall for the generation of the pulsed electron beam and part of the rooms for the technical infrastructure are also included in the controlled area. The experimental equipment is set up in 25 ‘‘flight path’’ cabins, spread in a radius at a distance of 10 m to 400 m from the target room. Several flight path tubes connect the holes in the shielding of the target room with the cabins and allow neutrons escaping the shielding to reach the experiment. Since 2010 a programme is on-going to renew systematically all cabins. In 2010-2011, eight cabins were already fully renewed. The 050 LINAC building hosts also a small radiation protection laboratory, which was totally refurbished in 2009. It is managed partially as controlled area, partially as supervised area.

020 VDG building and Van de Graaff accelerator: The installation of the first Van de Graaff accelerator took place in 1960 and in 1963 the accelerator was adapted for a maximum energy of 3,7 MV. In 1977 a second Van de Graaff accelerator of 7 MV was installed in the same building. In 2001 the initially installed 3,7 MV accelerator was dismantled. The Van de Graaff produces proton or deuteron beams interacting with small deuterium or tritium targets to produce neutrons. The 7MV accelerator is vertically mounted in a tower and the beam is further directed by magnets horizontally to the target hall. Experimental set-ups are possible on two distinct levels in the hall.

070 Radioactive waste storage: In 1976 a small building has been constructed for the storage of packed radioactive waste. The storage is a buffer awaiting the dispatch of the waste to Belgoprocess (under coordination of NIRAS/ONDRAF). The building was totally refurbished in 2003.

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Calibration room in the 140 safety building: The 140 Safety building hosts a calibration room which is managed as supervised area with restricted access. Few sealed calibration sources are stored in a safe when not in use.

170 Central waste water pipe system: The IRMM buildings with controlled areas have effluent collection tanks which are all connected to a central waste water pipe system. The system has been used since the IRMM started operating. Until 1997 the waste water was pumped directly to the site of the SCK•CEN in Mol, but in 1997 the line was dismantled and a new central waste water collection pit was laid on the IRMM site. Since then the waste water is periodically pumped in batches from the central pit to a specific tank truck and transported to Belgoprocess for treatment.

Nuclear Licenses and Classifications For the start of the earliest facility in 1960, a class 2 license was granted. This license covered the controlled areas of the 010 Main building, the 040 Mass Spectrometry building (MS1), the 020 Van de Graaff building and the 050 Linac building. Following the evolution of the research activities and the resulting increase of nuclear materials stored in the 040 Mass spectrometry building, the class 2 license was upgraded in 1971 to a class 1 license (S.3.299). This class 1 license was further amended at the extension of the building (MS2) and the later adaptations to the controlled areas on the site. The Royal Decree of 20 July 2001 fixes in article 3.1 the criteria for the classification of the installations (‘‘installaties’’) belonging to a facility (‘‘inrichting’’). Following criteria are applicable on the IRMM site: -

the nuclear laboratories of the 040 Mass spectrometry building are class 1 facility according article 3.1.a.2 (fissile materials above half the critical mass present in the facility)

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the 050 LINAC building and linear accelerator and the 020 VDG building and Van de Graaff accelerator are class 2 installations according to article 3.1.b.2

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the radio-metrology installations of the 010 Main building, the 070 Radioactive waste storage, the calibration room in the 140 Safety building and 170 Central waste water pipe system are class 2 installations according to article 3.1.b.3.e and g.

1.3 Scoping of nuclear installations to be included in the Stress Test The scope of the study is restricted to the nuclear laboratories of the 040 Mass Spectrometry building (or shorter: ‘‘MS building’’), which is the only class 1 facility on the IRMM site. The study includes the controlled areas MS1 and MS2, the supporting infrastructure (ventilation, fire protection systems, electricity supply and monitoring equipment) and the applicable procedures for the management of normal, abnormal and accidental conditions. As mentioned above, the on-going ‘‘ten-yearly assessment’’ of the nuclear safety is performed in parallel to the stress test study. It has a larger scope as it covers basically all nuclear safety issues and it includes also the lower-level nuclear installations of class 2 on the site. The evaluations and lessons learnt from the current stress test will

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be transposed where applicable to the class 2 installations and integrated in the related ten-yearly assessment report which will be issued end of 2012.

1.4 Relevant safety functions of nuclear installations According to the guidance document established by FANC, the three fundamental safety functions have to be addressed in the stress test assessment: -

prevention of criticality

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cooling

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confinement of radioactivity.

The applicability of these safety functions to the MS building and the related infrastructure and control means are described here below. 1.4.1 Prevention of criticality For the realisation of experimental measurements and the production of reference samples, IRMM uses nuclear materials of various physical, chemical and isotopic compositions: -

depleted and natural uranium (U308, UO2)

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uranium enriched in 235U (UO2 powder and pellets, U metal, U solutions)

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uranium enriched in 233U

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plutonium (PuO2, Pu metal, Pu solutions).

More than 90% of the nuclear materials (uranium, plutonium) present in the MS building are stored in a series of secured metallic cupboards (safes) in the storage rooms of MS2. The rest of the material is in use in glove boxes or stored provisionally in specific safes close to the experimental laboratories. For criticality safety, the fissile isotopes of uranium (235U and 233U) and the plutonium (239Pu and 241Pu) have to be considered. Criticality depends on the total mass of fissile isotopes, the presence of neutron absorbing and neutron moderating material, the geometry, density and the presence of neutron reflectors. Considering the most pessimistic assumptions that can be imagined, i.e.: -

the most unfavorable geometry: all the material in a sphere;

-

reflection of escaping neutrons by a water moderator

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only fissile isotopes, no matrix of absorbing material;

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all material diluted in water in the most unfavorable moderation ratio,

the minimal critical masses are approximately: -

for 235U: 800g

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for 233U: 500g

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for 239Pu: 500g.

In operational conditions, the critical masses are significantly higher as the geometry and reflection are less optimal for criticality; most of the material is also in solid state

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without moderator, with a few exceptions, and the fissile isotopes are included in a matrix of non fissile absorbing isotopes. As the total quantity of fissile material which is present in the controlled area of the MS building is higher than the minimal imaginable critical masses mentioned above, criticality control measures are implemented to assure that sub-criticality is maintained, even in hypothetic incidental circumstances. Prevention of criticality is basically ensured by mass control and geometry control:

Geometry control The nuclear material is stored in the storage rooms in safes. The rooms are geographically split in zones of one or two safes, which are physically separated, with a distance of minimally 2 m. This distance guarantees that there is no neutron interaction between the storage zones. The rooms and laboratories outside the storage are considered as two physically separated zones.

Mass control The masses of nuclear materials are accounted in the IRMM safeguards bookkeeping. This bookkeeping also keeps track of: - the masses of fissile isotopes of uranium (235U and 233U) and plutonium (pessimistically all plutonium is accounted as fissile 239Pu); - the state of the material: solid or in solution. The total mass registered in each zone in the storage rooms, depending on whether the material in solid state or in solution, may not exceed half the minimal critical mass calculated in the most pessimistic circumstances. The observation of a limit corresponding to maximum the half of the critical mass guarantees that criticality cannot occur, even in the case of an incidental ‘‘double batching’’. For the other rooms and laboratories outside the storage, the amount of material in use in the laboratories is kept at a minimum level. The total mass present in the area may not exceed half the minimum imaginable critical mass, independently of its state (solid or liquid). As a result there is no criticality concern in this area, even if all material present would be totally diluted in the most pessimistic moderation ratio. The calculations and implementation of the criticality safety measures is based on a generic assessment for the MS controlled areas. With respect to the relatively high margins considered, these operational measures guarantee the prevention of any type of normal and incidental configuration that could lead to criticality. 1.4.2 Cooling In the MS controlled area there is no equipment similar to a reactor requiring continuous cooling of the decay heat even after shutdown. Few experimental devices need cooling with water or liquid nitrogen, but any interruption of the power supply and the cooling will not induce any risk for potential releases. For this reason the assessments related to the operability of cooling systems and the ‘‘loss of ultimate heat sink’’ requested by the stress test methodology are not relevant for the present study and are not further addressed in the report.

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1.4.3 Confinement of radioactivity As already mentioned, the radioactive (nuclear) material is handled in glove boxes. The material which is not in use is stored in safes. Occasionally some material can also be present packed in transport containers. Radioactive waste is packed in drums or bottles if liquid. Basically, the prevention of radioactive releases relies on: -

the static confinement

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the dynamic confinement

The static confinement is ensured by the glove boxes, the packing of the radioactive substances and the building structure. The dynamic confinement is ensured by the ventilation systems. The related means and infrastructure for the MS building are described here below. In addition, following complementary infrastructure can play a key role in exceptional circumstances and will for this reason also be addressed in the present section: -

infrastructure to ensure the protection of the confinement in case of fire (fire detection, fire extinguishing system and fire resistant compartmentalisation)

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infrastructure to ensure continuity of the electrical power supply (for the ventilation and part of the fire protection infrastructure).

Static confinement The glove boxes ensure the primary confinement barrier: the glove box structure, panels, gloves and bags are basically airtight. The tightness is systematically tested before the commissioning of each glove box. On the glove box inlet and outlet penetrations for the ventilation, double HEPA2 filter cartridges are mounted (one cartridge inside and one outside the glove box) guaranteeing that basically no particles can escape. All operations on the glove boxes like the removal of gloves, bagging in and out of material, etc. are done in such a way that the static confinement is permanently maintained. An incidental loss of confinement during operation (e.g. damage on a glove) is normally quickly detected by the increased external contamination level and immediately remediated. Any material stored outside the glove boxes is confined in an at least double-sealed plastic bag and disposed in an outer container or in a drum. Depending of the type of material and the process, additional packing can be foreseen. Besides this primary confinement, the structure of the controlled area ensures a second static confinement barrier. Walls, ceiling and floor of the controlled areas form a closed entity. Access is possible through at least two doors in series: from the rooms or laboratories to a central corridor and from the corridor to outside.

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HEPA filters or “High-Efficiency Particulate Arresting” filters remove at least 99.95% of airborne particles 0,3 µm in diameter.

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Dynamic confinement Glove box ventilation In surplus of the static confinement, the glove boxes are kept in continuous underpressure, between -300 Pa and -700 Pa (-30 mm and -70 mm water column). The main reason for this additional measure is to limit the spread of contamination outside the glove box in case of an incident, e.g. in case of damage to a glove that could create a leakage. There is a central glove box ventilation line for MS1 and one for MS2. The glove box extractions are connected to central air exhaust ducts and linked outside the controlled area to a filter battery (pre-filter and HEPA filter) and further to ventilators, outside the controlled area (room 780 for MS1 and basement for MS2). There are two ventilators per extraction line, both continuously in operation. Each ventilator is driven by two continuously running motors: one motor is powered by the normal electricity supply circuit, one by the vital electricity supply.

Figure 1.6: glove box extraction ventilators MS2

The ventilator exhausts are further connected to the chimneys on the roof of the controlled areas. There is one chimney for the MS1 controlled area and one for MS2.

The under-pressure in the glove boxes doesn’t fluctuate drastically in normal circumstance. In the case the under-pressure of a glove box exceeds the acceptable range, an alarm is generated in the alarm centre. The under-pressure can be manually adjusted by valves on the inlet and on the outlet filters of the glove box. The more recently commissioned glove boxes are equipped with a selfregulating valve on the extraction.

Room ventilation The rooms and corridors of the controlled areas are kept in a continuous under-pressure cascade towards the outside atmosphere. The underpressure is at least below -60 Pa (6 mm water column) in the rooms and below -30 Pa (- 3 mm water column) in the corridors. The underpressure avoids that an incidental air contamination in a working area would spread outside. There are two separated extraction ventilation systems for MS1 and MS2. In each room of the controlled area there is at least one extraction point. Each extraction point has locally a filter battery (pre-filter and HEPA filter). The extraction ducts are further connected to the central air exhaust and linked to sets of additional filter batteries outside the controlled area. The batteries are located in the same rooms as the glove box ventilation.

Figure 1.7: room extraction ventilators MS1 powered by 3 x 2 motors

The systems for MS1 and MS2 have both three extraction ventilators: two ventilators (2/3) are continuously running for MS1, three ventilators (3/3) are continuously running for MS2. They are located in the

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basement. Each ventilator is again driven by two continuously running motors; one motor powered by the normal electricity supply, one by the vital electricity supply. The ventilator exhausts are connected together with the glove box extraction to the chimneys on the roof of the controlled areas. The described extraction systems have the fundamental safety function to ensure the underpressure. Their speed is not regulated. Besides, the air supply systems consist of air handling units with ventilators to condition the air at the requested temperature and ensure sufficient air renewals in the rooms (i.e. at least 10 renewals per hour). Speed control on these ventilators allows regulating the under-pressure at the desired level. The pulsation-extraction room ventilation circuits are open systems, which means that no air is re-circulated. The MS1 room ventilation is equipped with a heat exchanger allowing for a pre-heating or pre-cooling of the inlet air by the exhaust flow.

Protection in case of fire Fire safety requires a particular attention as there is a probability, in case of an extended fire in a laboratory, that the primary static confinement barrier (glove boxes, packages of radioactive material) will be damaged. In addition, the soot and dust generated by the fire can at least partially clog the filters on the extraction systems or create disturbances of the ventilation. This means that the static and dynamic confinement can in some cases not be fully guaranteed. For this reason, a fire detection and extinguishing system is installed which allows both the early detection of a starting fire and the mitigation of its consequences. In addition, the compartmentalisation retards the spread of fire in the building.

Fire detection and extinguishing All rooms and areas of the MS building are monitored by fire detectors, connected in a closed loop circuit to the building monitoring station. The monitoring station is linked to the central site fire management system, with displays in the fire brigade office and in the IRMM Alarm Centre, where there is 24/7 surveillance. The controlled areas MS1 and MS2 and the room 101 are protected with fire extinguishing systems. The main system is based on mist generation. In case of activation, a series of pumps installed in the basement inject water at 60 to 100 bar through injectors in the affected room and create a mist cloud that will contain the fire. In comparison with the more classical water spray system, the mist system has the advantage to generate much less effluents (which can be contaminated and difficult to evacuate). The fire extinguishing system dedicated to the two storage rooms is separated and not

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Figure 1.8: mist fire extinguishing extinguishing system MS

based on mist (water) but on extinguishing gas, ‘‘FM200®3’’. Three FM200® bottles are installed in the basement. If triggered by the fire detection, they will inject 150 kg of gas in the rooms. The extinguishing systems as described here can be activated by: -

the automatic detection by at least two detectors from a different detection loop in the affected room;

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a manual activation of push buttons located at the room entrances;

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a manual activation of switches at the entrance of the controlled areas;

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a manual switch on the FM200® gas bottles.

For conventional safety reasons, the automatic activation is disabled during the main working hours (Monday-Friday between 8 am and 5 pm). It is indeed assumed that there is sufficient competent staff available at that moment to proceed with the manual activation in case of fire detection.

Fire compartmentalisation The perimeter of the controlled areas MS1 and MS2 are both compartmentalised (including the walls, ceiling, floor and access doors) with a fire resistance of one hour. Passages for technical circuits are sealed accordingly. On the ventilation ducts, dampers will close automatically in case of high temperature (in MS1) or fire detection (in MS2). In addition, there is inside the controlled areas of MS1 and MS2 a supplementary compartmentalisation between the laboratory areas and the corridors, with a resistance of also one hour. The room 101 outside the controlled areas MS1/MS2 is compartmentalised in the same way.

Continuity of the electrical power supply The electrical power requires attention as it ensures following safety functions which are directly or indirectly linked with the confinement of the radioactivity: -

the operation of the ventilators as described above; the dynamic confinement has a back-up function in the case of an incidental failure of the static confinement; the operation of the monitoring, surveillance and communication systems; in case of fire, the operation of the pumps and control devices of the mist extinguishing system.

Main electricity supply The main electricity power supply to the site is provided by an incoming 15 kV line. Two main transformers reduce the voltage to 10 kV which is distributed to the major buildings on the site. In the electrical cabins of these buildings the voltage is further reduced to 400V and 230 V.

3

FM200® is a usual replacing gas for Halon. It extinguishes fires through a combination of chemical and physical mechanisms.

21

Since 2003 a second 15 kV supply line has been installed as back-up in case of an interruption of the normal supply line. The switch to the second line is not automatic but has to be done in a planned way by contacting the off-site dispatch service. In case of an incidental interruption of the off-site power, the dispatch of the electricity distribution company has to be called and the switch to the back-up line is done within maximum 15 minutes. The two main transformers of 2500 kVA are normally both in operation, as currently one individual transformer is not sufficient to provide the full power for the whole site. Two transformers will be replaced in 2013 by two transformers of 3500 kVA each, which will allow the operation of a single transformer with the second fully as back-up.

Back-up electricity supply systems Two diesel-generators (‘‘G1’’ and ‘‘G2’’) ensure the ‘‘vital’’ electricity supply in the case of total loss of off-site power. Each diesel-generator can provide 1000 kVA, which is largely sufficient for the maximum demand of the vital supply grid (estimated approximately at 400 kW). The two diesel-generators have been commissioned recently in 2011, in replacement of the old generator groups (3 x 250 kVA). In case of a loss of off-site power, the start of both diesel-generators will be triggered and they will be both ready-to-connect in about 5 s. One generator will connect to the vital supply grid of the site. This is done in following sequence: Priority

Building distribution board

Time (s)

1

090 High Voltage building

2

100 Conference building4

5

3

040 MS building vital 1

7

4

040 MS building vital 2

8

5

010 Main building

10

6

050 Linac building

11

7

020 VDG building vital 1

12

8

020 VDG building vital 2

12

9

130 CRM Building

14

10

110 FFA Building

15

11

200 RMP building

17

12

060 ISM building

20

13

190 CRM Storage Building

Table 1.1: sequence and timing of the connections to the vital supply grid If the connection of the first generator is not successful, the second generator will automatically connect. Once the connection is realised, the not connected generator will stop automatically and will remain in standby. 4

Priority 2 is given to the 100 Conference building, as the respective electrical distribution board includes the supply to the alarm centre

22

Two ‘‘day-tanks’’ of fuel (2 x 2400L) are located close to the diesel engines as immediate reserve. Two underground tanks (2 x 4900 L) provide an additional reserve. A complementary diesel-generator (‘‘D4’’) of 400 kVA is connected to a separate grid, dedicated to the cooling units of the storages of biological reference materials. The generator will also start in case of loss of off-site power. This generator is not relevant for nuclear safety. In addition to the main generators, two ‘‘small’’ diesel-generators (D11 and D12) of 50 kVA are dedicated to the extraction ventilation of the MS1 and MS2 controlled areas. One of them is running continuously, independently of the situation of the off-site power. These generators have to be considered as an extra back-up in case of electricity interruption and failure of the two main generators: would this be the case, the small generators will take over the two glove box ventilators and one room extraction ventilator per controlled area. In several buildings on the site ‘‘uninterruptable power supply (UPS)’’ units are installed. Their main function is to ensure continuity of the supply in case of a ‘‘tension dip’’ and to provide electricity in the time between a loss of off-site power and restoration of the power by the dieselgenerators. Part of the monitoring and surveillance devices of the alarm centre are connected to such an UPS unit. Some devices with batteries like the fire monitoring have certain autonomy even if the electrical supply is totally lost during a longer period of time.

1.5 Scope and main results of probabilistic safety saf ety assessments Considering the relatively simple lay-out of the installations and safety systems of the MS building, no comprehensive probabilistic safety assessment has been performed at the licensing or in later stages, like it is done for nuclear power plants or more complex nuclear installations. However, more specifically, the operations in the controlled areas are submitted in a systematic way to risk assessments. The dedicated risk assessments follow a generic procedure for the whole institute. All type of risks are considered (nuclear and non nuclear). A corresponding risk level is attributed in function of the probability of occurrence and seriousness of possible consequences. Dedicated safety measures are defined. These measures are transposed in the operational working instructions. As these risk assessments are rather detailed and have a broad range of applications, they will not be further addressed here.

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2 Earthquake 2.1 Design basis No major earthquakes have been ever experienced over the recent history of the Kempen region and this explains that, at the phased design and licensing of the MS building in the 1960’s and 1970’s, no calculations were performed to demonstrate its resistance to ground accelerations due to earthquakes. For the design of the buildings, consideration was however given to strengthen the structure sufficiently to allow following static charges: -

surcharge on floors of laboratories and corridors: 5 kN/m2 (500 kg/m2);

-

surcharge on roof: 2 kN/m2 (200 kg/m2);

-

surcharge on floors of basement: 10 kN/m2 (1.000 kg/m2).

These specifications do not guarantee the resistance to seismic accelerations but illustrate that certain robustness was pursued at the design.

2.2 Evaluation of margins 2.2.1 Range of earthquake leading to severe se vere damage to installation

Review level earthquake In absence of a ‘‘design basis earthquake’’, a ‘‘review level earthquake’’ is selected as hypothesis in order to perform the seismic assessment in the frame of this study. The selection was done in a common approach with the other nuclear sites of the region. It is based on the study performed by NIRAS/ONDRAF with the Royal Observatory of Belgium in view of the design and licensing of the low level radioactive waste disposal site in Dessel (‘‘cAt’’ project). The study is probably the most in-depth assessment of this kind ever performed in Belgium and covers: -

the redefinition of seismo-tectonic zones in Belgium and around;

-

the historical catalogue of earthquakes, complemented with a specific historic study for the Kempen region;

-

the determination of a bedrock response spectrum in function of three return periods (1.225 years, 8.575 years and 20.000 years);

-

the determination of the transfer function and calculation of the surface response spectrum.

The details of the assessment will not be repeated in this report as the study has been presented to FANC previously. For the determination of the review level earthquake of the nuclear installations on the region, the response spectrum determined in the study for a return period of 8.575 years is adopted. The corresponding peak ground acceleration is 0,24 g (or 2,4 m/s2). The approach can be considered as very conservative as it means that an earthquake of this intensity can be expected approximately every 10.000 years and that there is a probability of about 0,5% that the level is exceeded in a 50 years lifetime of an installation.

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The corresponding surface response spectra have been calculated, as illustrated in figure 2.1.

Figure 2.1 Surface response spectra for earthquake with return period of 8587 years By way of comparison, it can be assumed that these accelerations correspond to earthquakes with intensity between VII and VIII on the ‘‘modified Mercalli scale’’. Although there is no one-to-one relationship, it can be roughly estimated that intensities between VII to VIII would be perceived at the epicenter of an earthquake of ‘‘magnitude’’ of 6 to 7 on the Richter scale5.

Seismic assessment Based on the earthquake review level as selected above, an investigation is done to what extent such an event could lead to significant damages to: -

the building structure of MS1 and MS2;

-

more specifically the storage of nuclear materials in MS2;

-

the safety infrastructure.

The related assessment has been outsourced to external experts from Vinçotte Nuclear Safety, who proceeded by: -

visual inspection of the building, equipment and storage;

-

analysis of the construction plans of the building;

-

structural calculations of the seismic resistance.

5

The magnitude on the Richter scale is a rate for the energy released by the earthquake. The intensity on the modified Mercalli scale is based upon what people in the affected area feel and their observations of damage to structures around them.

25

Based on these assessments, the possible consequences on the safety functions are evaluated and measures which can be envisaged to increase the robustness of the installations are presented.

Assessment of the building structure resistance Calculations have been performed for three possible ‘‘failure modes’’: in-plane shear6, out of plane bending7 and foundation sliding8. The original building drawings provide information on the characteristics and lay-out of the building structures, including masonry walls, supporting columns, slabs, expansion joint and foundations. As the two areas MS1 and MS2 were not designed and constructed in the same way, separate calculations and assessments were needed. The results of the seismic calculations are expressed in terms of ‘‘factors of safety’’. The factor of safety for a given mode and with respect to a specified design surface response spectrum is defined as the ratio of the building resistance capacity to the applied seismic loading. A factor of safety less than one for a given failure mode and with respect to a specified design surface response spectrum means that the building will ‘‘fail’’ under the applied seismic loading characterized by the considered design surface response spectrum. It can be also said that for a given mode the building will ‘‘fail’’ under an applied seismic loading characterized by the considered design surface response spectrum multiplied by the factor of safety. The calculated factors of safety are summarised on table 2.1. For all the failure modes, at the exception of the sliding failure mode for MS1, the factor of safety is greater than 1. Mode of failure

MS1

MS2

First floor masonry: in-plane shear, E/W direction

5,7

5,7

First floor masonry: in-plane shear, N/S direction

2,8

2,8

First floor masonry: out of plane bending

1,2

1,2

Basement masonry: shear+bending, E/W direction

1,5

1,9

Basement masonry: shear+bending, N/S direction

7,5

1,1

Foundation sliding

0,8

1,6

Table 2.1: summary of safety factors for earthquake for buildings MS1 and MS2

6

A masonry wall is rigid when subjected to horizontal loads within its plane; when these loads exceed the “in-plan shear” capacity of the masonry, diagonal cracks form in the wall. The wall loses its rigidity and strength. The reinforced concrete columns in the wall subjected to the horizontal loads loose rigidity or strength. The whole structure is liable to collapse. 7

The failure mode of masonry by “out of plane bending” involves the collapse of an entire wall panel as a result of horizontal pressure acting on the wall. This can occur as a result of inertial forces under horizontal loads acting perpendicular to the wall face. 8

“Foundation sliding” involves relative displacement of the structure’s foundation (concrete poured on ground) and the ground it is supported on. This is technically a failure mode, in that the load capacity of the concrete / ground interface is exceeded by the applied horizontal load. However, it has no consequence on the stability of the building because the small displacements do not affect the resistance of the superstructure

26

The assessment shows that, under the stress of the accelerations caused by a review level earthquake and considering the stiffness of the building, no failures of the structure are expected. The integrity of the buildings and the confinement is therefore ensured. For each of the failure modes, the factor of safety gives the available margin. For the sliding failure mode of MS1, the coefficient of safety is found to be less than 1, which means that the foundation is expected to slide under the review level earthquake. This involves a possible relative displacement of the structure’s foundation but has no consequence on the stability of the building.

Assessment of the storage of nuclear materials Most of the nuclear materials are stored in safes in two rooms of the controlled area MS2. The safes are heavily secured metallic cupboards. They are not anchored on the floor or the walls. In three cases, a storage cupboard does not rest on the floor but is piled on another cupboard. The nuclear materials are packed in containers on the shelves or in the drawers of the cupboards. The integrity of the packages has to be maintained under earthquake conditions. A dedicated inspection of the storages has shown that loss of confinement was not credible in the case where the containers happened to overturn on the shelves or in the drawers during an earthquake but also that loss of confinement appeared to be unlikely if the cupboards themselves happened to overturn. The only potential cause of loss of containment would be the impact of a heavy component on the cupboards. It has been verified that no such components that could fall are present in the rooms where the cupboards are installed. However, in order to increase the conservatism of the evaluation, the seismic response of the cupboards under earthquake has been assessed; the risk for initiation of rocking and the risk of overturning. The analysis was performed for the most critical cupboard. The results of that seismic assessment are summarized in table 2.2 below, showing the factors of safety. It comes out that the analysed cupboard will initiate a stable rocking response without overturning. Mode of failure

Factor of safety

Initiation of rocking

1

Overturning

2

Table 2.2: estimated safety factors for cupboards resting on the floor

Assessment of the safety infrastructure resistance The ventilation and fire protection systems and the electricity supply systems will be also impacted by the earthquake loads. The site inspection has shown that some infrastructure components, in particular the electrical cupboards, are only lightly anchored to the masonry. It can therefore not be excluded that in case of earthquake part of the electricity supply will be damaged and cannot be further ensured, until back-up supply is provided.

27

functions Consequences on the safety funct ions Prevention of criticality It has been demonstrated that the review level earthquake will not affect significantly the safe storage. Masses and geometries will remain unchanged. In conclusion, the criticality risk will not be increased.

Confinement of the radioactivity The assessment has shown that the static confinement provided by building structure and storage cupboards will remain unaffected under the conditions of the reference earthquake. As mentioned, damages could occur to the electrical cupboards and there is a possibility that at least a part of the extraction ventilation will be inoperable. In that case, the dynamic confinement will not be ensured anymore. The electrical cupboard of the mist extinguishing system could also be damaged. Besides, it can be expected that, due to the earthquake accelerations, various non-fixed but not necessarily safety-related components in the laboratories will fall on the ground or be damaged. Some connections to glove boxes could be affected, creating locally some contamination which will remain confined in the laboratories. As a result of the earthquake and related damages, the controlled area will have to be evacuated in a controlled way. This will eliminate the risk for a spread of contamination to outside. The inoperability of the automatic fire extinguishing system will have to be compensated by organisational measures and the supply of transportable fire extinguishing means to be standby in case of fire. The controlled areas will have to be re-entered for checks on potential damages or local contaminations. In the short term and as long as the ventilation is not operational, this has to be done by accessing the controlled areas with the necessary and available personal protection equipment: full-face masks, overall, gloves, overshoes. More comprehensive contamination checks and repair of damages will be possible once the ventilation is working again.

It can be concluded that the review level earthquake will not lead to release of radioactive substances. However, would the extraction ventilation be partially or totally interrupted, it is preferable that the situation is remediated without delay, in order to allow normal access to the controlled areas for the necessary verifications and repairs. which hich can be envisaged to increase the robustness of the plant Measures w Measure on existing infrastructure -

Installation on the extraction ventilator motors of a connection allowing to plug them to an alternative electricity supply In the situation that the electrical cupboards of the ventilators are damaged, a temporary alternative electricity supply to the ventilator motors should be installed. A ready-for-use connection will limit the delay.

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-

Improvement of the fixation of the safety-related electrical cupboards The improvement of the anchoring of the safety-related electrical cupboards, where possible and necessary, will decrease the damage risk.

Organisational measure -

Adaptation of the emergency instructions to deal with earthquake The sequence of the appropriate measures to be taken, once an earthquake of whatever intensity is observed, could be integrated in the emergency procedures. Appropriate training of the involved technical staff is to be foreseen.

Measure at the design of new installations -

Consider the review level earthquake as design basis for the new nuclear facility The building and the infrastructure should be designed in order to resist the review level earthquake as defined in the current assessment.

2.2.2 Range of earthquake leading to loss of confinement integrity

Range of extreme earthquake The summary of the calculations for the review level earthquake on table 2.1 shows that the lowest margin to a severe damage of the building structure can be expected for the shear and bending of the basement masonry of MS2 in the N/S direction. Using a proportionality rule, it can be concluded that failure of a wall is in principle possible for an earthquake with peak ground accelerations of 0,26 g (0,24 g x 1,1). Depending on the damages, loss of the static confinement cannot be excluded in that case. According to table 2.2, this extreme earthquake could also cause the rocking of some storage cupboards but no overturning.

Consequences of the loss of confinement in the case of an extreme earthquake A calculation has been performed to estimate the magnitude of the releases that can be expected in the case the confinement is lost. The calculation is based on the inventory of nuclear materials presently stored in the main storage rooms. Following assumptions are made: -

ventilation out-of-service

-

walls of the storage rooms completely damaged

-

storage cupboards are chocked but remain closed

-

1% of the bags (packages) containing the nuclear materials are damaged

-

airborne release ratios as prescribed by US DOE (DOE HDBK 3010-94).

The calculation shows that this hypothetic situation would lead to a release in the air outside the building of about 1 kBq of alpha activity. As basis for comparison, the

29

license of the MS controlled areas authorises an airborne release of up to 74 kBq per week9.

It can be concluded that even an extreme earthquake causing structural damages to the building structure will not lead to a significant release of radioactive substances. The measures on the existing infrastructure as defined in section 2.2.1 will only facilitate and accelerate the recovery, would a severe earthquake occur.

2.2.3 Earthquake exceeding the design basis earthquake for the plant and consequent flooding exceeding design basis flood As the IRMM site is not located along a major river or a water reservoir, no immediate wave can be expected as a result of an earthquake. The canal Bocholt-Herentals is at about 1,5 km distance from the site. The possible consequences of a rupture of a lock or dike on the canal, which could be the result of an earthquake, is assessed in section 3.2 and will for this reason not be addressed here.

9

The license of the MS2 controlled area mentions explicitly the maximum permissible activity release of 74 kBq (2 µCi) per week. In normal circumstances, the atmospheric releases from the MS buildings are at the background level, i.e. about 3 decades below the maximum level.

30

3

Flooding

3.1 Design basis Flooding was not explicitly taken into consideration at the licensing of the MS building. However, the floor of the lower stage of the MS building and the controlled areas is constructed at +1,2 m above ground level. On the other hand, the basement containing the heating, cooling and ventilation equipment and other support infrastructure is at -1,5 m. The floor of the 090 medium voltage building and the 091 diesel-generator building is about +0,5 m from the level of the nearby road.

3.2 Evaluation of margins: level of flooding and consequences Topography and hydrogeology of the site As there was no evaluation of the flooding risk done at the design, an investigation is done on the topography and hydrology of the site as basis to evaluate possible scenario’s that could lead to flooding. The topographic map of the region shows that the whole site is at an elevation of 25 m (elevation above mean sea level). This is more elevated than most of the surrounding areas: the site is located at the edge between the basin of the ‘‘Kleine Nete ’’ on the North and the basin of the ‘‘Molse Nete’’ and ‘‘Grote Nete’’ on the South: -

The area at the North and West of the site, in direction of the canal BocholtHerentals, is almost lower everywhere. The steepest slope is observed in the NorthWest direction; the fishing pools ‘‘Dekshoevevijver’’ at a distance of about 1,5 km from the site are 5 meters lower (elevation 20 m). Further at the North of the channel, in the direction of Retie, the declination continues till the ‘‘Kleine Nete’’ river, flowing at about 5 km from the site (elevation 18 m).

-

At the South of the site the elevation decreases in the direction of Geel and the ‘‘Molse Nete’’, located at 3 km (elevation 20 m). The ‘‘Molse Nete’’ belongs to the basin of the ‘‘Grote Nete’’.

-

East of the site the elevation stays at the same level and, further on, tends to increase in the direction of Mol, to an elevation of about 30 m at 6 km of the site.

On the site there are some ditches and an artificial pool. The pool collects the rain water, the water of the cooling towers. The ground water potentially leaking in the basements is also pumped to the pool. The surplus water of the ditches on the site and the pool is evacuated gravitationally to a network of ditches at the North of the site and further to the ‘‘Blekenloop’’ flowing in the ‘‘Daelmansloop’’. The ‘‘Daelmansloop’’ flows to the West, reaching the ‘‘Kleine Nete’’ at about 10 km of the site. Figure 3.1: pool on the site The current soil map of the site area shows that the sandy soils have a rather low permeability. The low permeability is confirmed by the historical map of the site area,

31

showing the presence in the middle of the 19th century of a large pool on the site (Atlas van de buurtwegen, ca. 1845). The old pool is now filled in, but an important layer of peat ground was still found during recent excavation works. Experience with recent constructions and the observation of the water level of the ditches show that the level of the water table oscillates roughly between -2 m in the summer and -0,5 m in winter time.

Conceivable flooding Flooding on the site could have several origins: - excessive rain fall - excessive melting snow - rupture of a lock or dike on the canal Bocholt-Herentals - technical failure in a water circuit. These different scenarios are evaluated in order to determine which flooding can be considered as ‘‘conceivable’’.

Flooding by excessive rain fall In the more than 50 years of existence of the institute, no significant flooding on the site was ever experienced. A total inundation of the whole site area over more than a few centimeters can be excluded, based on its topographic situation: any significant rise of water above the ground level on the site will naturally tend to flow away to the land and ditches North, West or South, which are all at a lower elevation. However, an excessive rain fall will cause an increase of the water table level. It is known that the soil has a relatively low permeability and all the excess rain water is evacuated through pipes and ditches. An obstruction of these evacuation routes would cause an increase of the water table and the water level of the pool and ditches on the site. If no action is taken, they will overflow and part of the site could be flooded. Depending on the location, the excess water will flow away but can enter gravitationally the basements of the nearby buildings. All basements have ground water pumps installed evacuating automatically excess water to the pool. These pumps can provide a flow of a few tens of m3/h, which could be insufficient in the case of a fast intrusion of water. As a result, the floor of the basement of the MS building (at -1,5 m under ground level) could be partially or totally inundated. Flooding of the controlled area (located on the first stage with floor is at 1,2 m level) can be totally excluded in this scenario. However, a local flooding of some rooms by water intrusion through possible leaks in the roof in the case of a heavy rain fall is possible. Excess water will flow down the floor of the controlled areas to sewage pits or under the doors to outside. Flooding of the main electricity supply, transformers, the 090 medium voltage building and 091 diesel-generator building can be excluded in the case of an increase of the water table, as the floors are approximately +0,5 m above the street level. The inlet plugs of the underground fuel tanks are at about +0,1 m above the street level. Intrusion of water could however occur here also through leakages in the roofs of the buildings.

In summary, following flooding events are conceivable due to excessive rain fall:

32

-

the partial or total flooding of the basement of the MS building in the case of an obstruction of the gravitational rain water evacuation from the site and an absence of immediate actions to remediate;

-

the local flooding of some rooms of the controlled area or some rooms of the electricity supply buildings by water intrusion from the roof.

Flooding by excessive melting snow The consequences of excessive snow on the building resistance are investigated in section 4.1 of this report. Snow melting could also cause locally flooding, as the water outflow can be refrained by an obstruction of the evacuation routes by the snow. A flooding of the basement of the MS building by melting snow is possible but it can be expected that the inundation process will be slower than in the case of overflow by excessive rain fall as discussed above. It is very likely that the flooding will be compensated by the evacuation of the water with the ground water pumps in the basements.

Flooding by rupture of a lock or dike on the canal Bocholt-Herentals The canal Bocholt-Herentals is 57 km long and has in total ten locks to compensate the elevation difference. The canal goes in the East-West direction and is at the location of lock 7 (‘‘sas 7’’) the closest to the site, about 1,5 km on the North. Along the canal the water is contained by vertical walls and where necessary a slight local elevation of the ground. A rupture of the containment could create locally some flooding. This rupture could be caused by ageing but also by an external event, e.g. an earthquake. The water elevation of the sections of the canal at its closest point to the site is however lower than the site elevation: -

section between lock 8 (at 5 km West of lock 7) and lock 7: approx. 21,3 m;

-

section between lock 7 and lock 6 (at 3 km East of lock 7): approx. 23,7 m.

The sections further at the East of lock 6 have an elevation above 25 m but they are at more than 3,5 km from the site. Considering the topography, any flooding from these sections will inevitably flow to the section between lock 7 and lock 6 and further flow to the lower area on the North of the in the direction of the ‘‘Kleine Nete’’. In summary, a total or even partial inundation of the IRMM site by rupture of the containment of the canal can be excluded.

Flooding by technical failure of a water circuit Besides the external causes described above, flooding could be created by an on-site technical failure of a water circuit. The basement of the MS building contains various water circuit for the water supply systems, heating and cooling systems, sewage systems and evacuation of ground water. A rupture of a tube or a malfunction creating a siphon effect could lead to an at least partial flooding of the basement. Depending on the volume of water involved and its flow, the water level can be kept under control by the ground water pumps. A rupture of a water circuit in a room of the controlled area could also lead locally to some flooding. All rooms of the controlled areas are equipped with water detection with an alarm reported to the guards building. Excess water will flow down the floor of the controlled areas to sewage pits or under the doors to outside.

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Consequences on the safety functions Prevention of criticality As the nuclear material is stored in the controlled area at minimum +1,2 m height above the ground level, no criticality concern can raise in case of flooding on the site. Flooding by local damage to a water circuit is excluded as there are no water lines in the storage rooms. On the other hand, water intrusion through leakages in the roof could percolate and enter the storage cupboards. Water mixing with the storage containers could theoretically increase the moderation ratio, thus lowering the criticality margin. For this reason a specific calculation was done for all the current storage zones, in the most extreme and hypothetic case. Following assumptions were made: -

the full content of each zone is homogeneously mixed with water

-

the most penalising geometry (sphere)

-

the most penalising moderation ratio

-

water reflection.

The calculation demonstrates that even with the conservative assumptions there is a sufficient margin towards criticality.

Confinement of the radioactivity In case of flooding of the basements, the ‘‘static confinement’’ of the radioactivity in the controlled areas will remain unaltered. But an impact on the ‘‘dynamic confinement’’ function can be expected: most of the ventilators and the electrical cupboards for the control and power supply to the ventilators are located in the basements of the MS building. The pumps of the mist fire extinguishing systems and the related control and electricity supply are also located in the basement. It can be expected that once flooding of the basements and the related disturbances are observed, the controlled areas will be evacuated. Depending on the circumstances, the electricity supply to the building will have to be temporarily switched off to contain the electrocution risks if an intervention in the basements is needed. Independently of any action taken, following ‘‘cliff edge’’ effects can be identified: -

flooding basement > 12 cm: o water level reaches lower part of the cable connections in the electrical cupboards; loss of the electricity supply to the ventilation systems o for the same reason, loss of the power supply to the ground water pumps

-

flooding basement > 15 cm: o lower part of the control cupboard for the mist fire extinguishing system reached; loss of the electricity supply of the automatic fire extinguishing system o water reaches the lower connections and motor of the fire extinguishing pumps; loss of the four fire extinguishing pumps

34

o water reaches the lower connections and motor of the MS2 glove box extraction ventilators10; loss of the two glove box ventilators MS2 -

flooding basement > 25 cm: o water reaches the lower connections and motor of the room extraction ventilators of MS2; the three room extraction ventilators MS2 are inoperable

-

flooding basement > 32 cm: o water reaches the lower connections and motor of the room extraction ventilators of MS1; the three room extraction ventilators MS1 are inoperable.

The evaluation shows that in case of flooding in the basements above 12 cm, most of the electrical power supply will be interrupted and the ventilation will be inoperable, with as consequence a loss of the ‘‘dynamic confinement’’ function. The confinement of the radioactivity will remain ensured by the static confinement. But there is no back-up function anymore in the case an incident would happen in the controlled area with a spread of contamination. A situation without dynamic confinement will have no major consequences for a period of a few days as long as there is no working activity in the controlled areas. For longer periods, access to the controlled areas will be necessary for verifications, maintenance and replacing of ageing equipment. In that case minimal ventilation should be restored. The inoperability of the automatic fire extinguishing system will have to be compensated by organisational measures.

It can be concluded that flooding will not lead to release of radioactive substances. Flooding has however to be avoided or remediated without delays as it will have consequences to the operability of the controlled areas, damage safety equipment and decrease the overall protection level. Measures which can be envisaged to increase robustness of the installation Measures envisaged on the current infrastructure -

Installation of appropriate water detection in the basements with alarm reported to the alarm centre Detection will allow starting remedial organisational measures in the early stages of a potential flooding of the basements.

-

Improvement of the protection against water intrusion of the ventilator rooms A basic protection by sealing the openings and placement of dams at the room entrances could delay the possible flooding damages to the equipment. Note: a total protection of 040 building by making the basements water tight is not envisaged; many existing interconnections and openings would make such a provision unreliable; a protection of the electrical cupboards is excluded for the same reasons.

10

Contrarily to the glove box extraction of MS2, the two glove box extraction ventilators of MS1 are located in a room at the first floor and will not be damaged by a flooding in the basement (although they will lose the power supply

35

-

Installation on the extraction ventilator motors of a possibility to plug them to an alternative electricity supply In the situation that the electrical cupboards of the ventilators are flooded, a temporary alternative electricity supply to the ventilator motors should be installed (same measure as for earthquake).

-

Adequate transportable pump allowing to be used in case of urgency A transportable emergency pump available on the site will allow starting quickly with the evacuation of the water from the basement. Such a pump could be installed on the fire brigade truck.

Organisational measures -

Adaptation of the emergency instructions to deal with the flooding of the buildings The sequence of the appropriate measures to be taken once flooding is observed has to be integrated in the emergency procedures. Appropriate training of the involved technical staff has to be foreseen.

-

Continuous surveillance of the water level in the pool An abnormal increase of the level of the water pool on the site could be an indication of an obstruction. The installation of a level indication and the surveillance of the level could allow anticipating a possible flooding and initiating on time remedial actions.

Measure at the design of new installations -

At the design of the new nuclear facility, consideration should be given not to install safety equipment and the related electrical supply chain in the basement. If the safety equipment is installed at an appropriate level (a few tens of centimetres) above the ground level, the safety functions will remain guaranteed for any conceivable flooding of the site area

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4 Other extreme events 4.1 Very bad weather conditions Most extreme weather conditions in Belgium and the Netherlands The Royal Institute for Meteorology (KMI/IRM) publishes information about abnormal and extreme meteorological conditions and events observed in Belgium over the last century. A synthesis is done here below. Few observations of extreme weather conditions in the Netherlands as recorded by the Dutch Royal Institute for Meteorology (KNMI) are also mentioned (the climatology is not fundamentally different and the site is close to the Dutch border).

Strong winds and tornados Strong winds can be expected several times a year. It is not exceptional that some years wind velocities over 100 km/h are measured locally. The most extreme velocity ever recorded in Belgium is 166 km/h (1990). Heavy tornados are occasional in Belgium. The most severe tornado in the region occurred on 25 June 1967 in Oostmalle (25 km Northwest of Geel) and in Chaam and Tricht in the Netherlands. Based on the observation of the damages, these tornado’s are commonly classified as ‘‘F3’’ on the Fujita scale (or ‘‘EF4’’ on the enhanced Fujita scale), meaning that locally wind velocities up to 250-330 km/h could have been reached.

Heavy rainfalls Heavy rainfalls are mainly combined with storm weather. The period May-August is the most sensitive. The heaviest rainfalls recorded in the region reached 20-40 mm (20-40 L/m2) in short periods (periods of less than one hour) and up to more than 100 mm in periods of a few hours.

Hail Heavy hail is mainly combined with storm weather. The number of days with hail (about 40% of the storm days) is slightly increasing over the last decennia. Most commonly the hailstones don’t exceed 1 cm. For the most extreme hail storms in Belgium, hailstones up to 5 cm thick are observed (the absolute record is a hail stone of 250 g found after a storm in 1906). The residual ice layer due to hail reached in the most extreme circumstances 30 cm and at one occasion even more.

Lightning There are commonly 80 to 110 storm days with thunder registered per year in Belgium. Over the last decennia it is observed that the number of days tend to increase due to climate change effects. The frequency for lightning strike in Belgium varies between 0 and 10 per km2 per year. Lightning maps don’t show significant regional sensitivities11.

11 The

frequency of lightning strikes in Belgium is low in comparison with some other countries in the world, where an average of more than 50 strikes per km2 per year can be reached.

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Lightning is the most common cause of surcharge on the electricity grid (by direct or indirect strike).

Snow Snow layers of more than 20 cm are rather exceptional in the Northern part of Belgium, but are occasionally observed. Maxima of 34 cm were recorded in 1925 and 1973 in Ukkel. Closer and at a similar altitude as the site, maxima of 29 cm and 24 cm were recorded respectively in 1969 and 1985 in Kleine Brogel (Limburg Province). The maximum layer ever recorded in Belgium reached 1,15 m in 1953 in Botrange (at an altitude of about 700 m). In the North of the Netherlands, 59 cm has been recorded in 2005.

C onceivable events on the IRMM site due to extreme weather conditions Considering the historical data, following extreme weather conditions will be taken as reference for the assessment: - strong winds and EF4 tornado with winds up to 250-330 km/h; - heavy rainfall of 40 mm in one hour and up to more than 100 mm in one day; - hail with hailstones of 5 cm and residual hail layer of 30 cm; - lightning strike on or in the immediate vicinity of the MS building; - snow layer of more than 1 m. These different conditions are evaluated in order to determine the resulting ‘‘conceivable’’ events.

Strong winds or tornado Strong winds will primarily damage the infrastructure located outside, especially on the roofs and the less resistant parts of the MS building. Pressures of the order of 1 kN/m2 (100 kg/m2) can be theoretically12 expected for winds at 144 km/h (40 m/s). The wind pressure combined with wind missiles will damage the exposed windows and doors, with further damage on the infrastructure and equipment inside the buildings. The resistance of the masonry will not be exceeded. The controlled areas MS1 and MS2 have both outside doors with windows, which are however of the reinforced strong type (qualified according to the applicable BESOC standard for reinforced doors). According to their design characteristics, they will resist to overpressure and wind missiles. The inner access doors to the controlled areas inside the buildings are of the same type. For this reason it can be expected that the controlled areas will remain confined. Heavier winds can not totally be excluded. In the case of a tornado, the situation on the site is even less predictable. If the MS building would be directly affected by a tornado, winds in the range of 250-330 km/h will probably damage the walls of the controlled areas. Cracks or other can create locally breaches in the integrity of the confinement. But it can be assumed that the heavy metallic storage safes will not be affected.

12

Theoretical pressure calculated with the Bernoulli formula

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Heavy rainfalls A heavy rainfall of 40 mm in less than one hour could inundate the roof of the MS building. The water evacuation from the roof could be obstructed by the heavy flow and accumulating rubble. The edges on the border of the roof will retain the water from overflowing. Depending on the location, the edges on the roof above the controlled areas have a height between 5 and 20 cm. The resulting surcharge on the roof could reach locally maximum 2 kN/m2 (200 kg/m2). Considering the design surcharge fixed at 2 kN/m2 (200 kg/m2), no rupture of the roof slabs is expected. However, water intrusion in the controlled area through leakages in the roof is not excluded. The consequences of the possible resulting local flooding of the controlled areas are already addressed in section 3.2. The consequences of the heavy rainfalls on the whole site are also addressed in section 3.2.

Hail Extremely heavy hail will create damages to the outside infrastructure of low resistance. Sensitive parts of the building structure (e.g. exposed windows) will also be impacted. Data available in the literature on hail damage tests show that a hailstone of 5 cm (falling at a speed of 100 km/h) will have a direct impact energy of 30 J. This level of impact will not exceed the resistance of the reinforced doors and windows of the controlled areas of the MS building. The hail layer will create a charge on the roof. Even in the worst case, a hail layer reaching locally 30 cm will not create a surcharge above 2 kPa (200 kg/m2). The roof slabs will not collapse.

Lightning Lightning strikes could directly impact on the MS building or in the vicinity of the MS building. As there is no lightning protection on the roof of the old buildings on the site, damages could be expected. The lightning can ignite flammable equipment, e.g. the roofing on the top of the building. Due to the high voltage and induced currents, the lightning can create surges in conductors in the building and ignite locally one or more electrical installations. The electricity supply to the building can be also interrupted by the surge and the resulting shortcuts.

Snow An extreme snowfall creating a layer of more than 1 m on the roof of the MS building will create a uniform surcharge. Considering a snow density of 100 kg/m3, the surcharge will be 1 kN/m2 (100 kg/m2). No rupture of the roof slabs is expected in this case.

In summary, following conceivable events related to extreme weather conditions could have an impact on the controlled areas: - tornado directly affecting the MS building and causing damages to the building

structure, in particular the walls of the controlled areas; - intrusion of water in case of heavy rain falls; - fire in the controlled area as a result of a lightning strike.

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The intrusion of water is assessed in section 3.2 and will for this reason not be further addressed here. Consequences on the safety functions Prevention of criticality The possible damages to the building structure by a tornado will not alter the storage of the nuclear materials in the metallic safes. In the case a fire caused by a lightning strike would affect the storage rooms, the automatic extinguishing with gas will be activated. In the case of a simultaneous disturbance of the electricity supply, the activation with a manual switch on the gas bottles is still possible. In an extreme deteriorated situation, an intervention by the fire brigades and extinguishing from outside could be considered as an ultimate back-up. Water or watercontaining extinguishing means are in principle prohibited as it would increase the moderation ratio and thus lower the criticality margin. The fire brigade has a reserve of powder extinguishing agent (2.000 kg) for such purposes. It has been however calculated that with the currently stored quantities of nuclear materials, there is sufficient margin towards criticality even with the assumption of water intrusion in the safes (see section 3.2).

Confinement of the radioactivity In the case of cracks in the walls of the building created by a tornado, the material stored in safes will remain protected but damages are possible to the equipment in the laboratories, creating local contaminations. Possible airborne contamination will be extracted by the ventilation systems and retained on the HEPA filters. Any significant releases can be excluded. In case of a fire caused by a lightning strike, the fire extinguishing systems are activated but as mentioned above, a malfunction due to a disturbance of the electricity supply is not excluded (only the storage room has a back-up independently of the electricity circuits, with the manual switch on the gas bottles). The extension of a not immediately controlled fire will be contained during at least one hour by the room compartmentalisation. This should allow the fire brigade to organise the appropriate interventions. Only if the intervention is not successful for whatever reason, the fire could extend, the integrity of the confinement could be altered and a release of radioactive material is possible. A calculation has been performed to estimate the magnitude of the releases that can be expected in this case. The calculation is based on the inventory of nuclear materials currently stored in the main storage rooms. Following assumptions are made: -

automatic extinguishing out of service

-

dampers on the ventilation isolate the room after 15 min

-

integrity of the storage rooms is partially damaged

-

integrity of the storage cupboards is maintained

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-

5% of the bags (packages) containing the nuclear materials are destroyed at the end of the fire

-

airborne release ratios as prescribed by US DOE for a fire situation (DOE HDBK 3010-94).

The calculation assumes a pressure build-up in the room based on the involved fire load and the expected temperatures. From the calculations it comes out that this situation would lead to a release in the air of about 10 kBq to 100 kBq of alpha activity. As mentioned above, the license of the MS controlled areas authorises an airborne release of 74 kBq per week.

It can be concluded that no extreme weather conditions were identified that could lead to releases from the controlled areas, except lightning strike. A lightning strike causing a not controlled fire in the controlled area, if combined with the unavailability of the fire extinguishing systems and the failure of fire combating by the fire brigades could lead to releases. However, these releases would be of the order of what has been considered as acceptable at the licensing of the MS building. Measures which can be envisaged to increase robustness of the installation Measures envisaged on the current infrastructure -

Installation of an appropriate lightning protection of the roof of the MS building A lightning protection on the roof of the MS building will provide a basic protection and lower the risk for damages and initiation of a fire.

Measures at the design of new installations -

The new nuclear facility and the new 222 SHES building (with alarm centre) should be protected with lightning and surge protection. A protection of the respective buildings and their electrical circuits will lower the risk for damages and initiation of a fire.

4.2 Bush or forest fire Environmental situation of the site and the MS building The IRMM site is located in a forest area. On the 38 ha of the IRMM site, 24 ha (or approximately 6/10) is planted with mainly pine trees. Outside the site, the forest area extends mainly in the North and Northeast directions. The forest area is traversed by fire corridors to allow access for the fire brigades. The corridors in the vicinity of the site go in the Northeast/Southwest direction and are approximately 200 m distant from each other. The corridors on the site are accessible from outside through (locked) gates in the fence. Along the perimeter of the site, there is a free deforested area of about 10 m width to allow the surveillance of the fence, for guarding purposes.

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Around the MS building, there is a free area of 20 m without trees (the requirement of a free area is explicitly integrated in the license). As already mentioned, the forest management plan established in 2009 for the IRMM site foresees in a gradual removal of pine trees over 20 years to allow the original vegetation (oaks and birches) to expand again.

Figure 4.1: IRMM site (below on the picture) picture) with forest area at the North and Northeast

In addition, the forest management pays attention on fire protection and following provisions are foreseen: -

the maintenance of the fire corridors and free space along the fence;

-

the periodic mowing of the grass fields and grassland;

-

the removal of branches and the smaller wood residues when trees are cut (only tree trunks can be left as residues).

These measures have been contractually included in the programme of the company ensuring the gardening on the site.

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naturee fires and common remedial measures C onceivable natur Situation in Belgium and in the Antwerp Province In order to evaluate the situation related to fires of natural origin in the region, contact was taken with the local fire brigades of Mol and Geel as well as the fire brigade of Wuustwezel13. In summary, following points of attention were raised:

Experience with nature fires -

Three types of nature fires can be identified: -

fires of the grassland; bush fires; crown fires.

Grassland fires are the most common in our regions. Crown fires are the heaviest, but have a lower probability to occur in the region. Over the last years, the Mol fire brigade had one single experience with a crown fire. -

The attention for forest fires is increasing in Belgium. This is explained by the experience with fires over the last years. The gradual extension of the fire spread over the ‘‘Kalmthoutse Heide’’ in the North of the Antwerp Province is an example. This observed trend is probably linked to climate change effects.

Prevention and combating nature fires -

No real standards or guidelines exist in Belgium. As a result of recent nature fires, working groups have been created in 2011 by the Governmental Crisis Centre (Federal Service Interior Affairs) in order to perform overall risk assessments, define the measures to take and improve training. Final results are not yet available.

-

For the moment, the Belgian fire brigades rely mainly on the French experience and there is an enhanced interest for training in France. In France guidance documents exist (e.g. « Préfecture du Var, Guide des Equipements de Défense de la Forêt contre l’Incendie »). It is prescribed to foresee a free perimeter of 50 m around sensitive areas.

-

In Belgium, there is no fixed rule for a safety perimeter around buildings; the prevention measures have to be taken in function of a dedicated risk assessment. The replacement of pine trees by broadleaf trees is a rather common measure to decrease the risk. If grassland is maintained as perimeter, periodic cutting has to be foreseen.

-

The fire brigades of sensitive regions in Belgium rely on cartographies (scale 1/25.000 or 1/10.000) of the risk zones, which exist for the most common sensitive areas. This is experienced as a very useful tool to help to coordinate the interventions in case of fire.

13

In the Flemish region and in particular the Antwerp Province, the fire brigade of Wuustwezel has a high level of expertise in the prevention and combating of natural fire. The expertise is directly linked to the inherent sensitivity of the “Kalmthoutse Heide” and surrounding areas.

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-

Monitoring of the evolution of the risk in function of the meteorological circumstances is important. Currently this is organised by the fire brigade of Wuustwezel. In case of high risk, an alarm phase ‘red’ is announced. Complementary, small-scale specific ‘‘monitoring kits’’ can be installed locally in sensitive zones.

-

The rapid availability of sufficient volumes of extinguishing water is essential.

Conceivable events at IRMM With regard to the environmental situation of the IRMM site, a fire of natural origin and in particular a crown fire cannot be excluded. The fire could have been initiated on the site or in the forest area or gardens or houses outside the site and spread to the trees and vegetation in the vicinity of the buildings. Forest fire is for this reason included as a potential event in the IRMM contingency plan (see below in this report under section 6). The interventions will be in the first stage done by the IRMM fire brigade, supported by the Mol and Geel fire brigades. The extinguishing water has to be supplied by the hydrant system of the site (which can provide 75 to 110 m3/h at 2 to 4 bar) However, if the combating of the fire is not successful, following side-effects affecting the safety of the MS building are possible: - glowing ashes and the heat from the surroundings could ignite the roofing layer on the roof of the MS building, causing a direct risk for spread to the controlled areas; - glowing ashes and smoke at high temperature could enter the ventilation systems (air supply systems); in case of ignition of the filters, the smoke and heat could extend through the ventilation ducts to the controlled area rooms. In this case the automatic fire extinguishing will be triggered and the ventilation dampers (ensuring the room compartmentalisation) will be closed; - the main transformers (located outside at the back side of the 090 Main voltage building) could be damaged with interruption of the main electricity supply to the site as consequence; - the smoke could enter the air inlet of the diesel-generators. A heavy smoke could make one or more engines out of order. It is therefore essential in case of fire that the interventions by the fire brigade are rapid and efficient enough to prevent any extension to the nuclear controlled areas.

For the present study, the scenario of a forest fire causing fire in one or more rooms of the controlled area, combined with a loss of the electricity supply is considered as a conceivable event. Consequences on the safety functions Prevention of criticality The consequences of a fire on the criticality safety in the storage rooms are the same as in case of a fire initiated by lightning strike, see section 4.1.

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Confinement of the radioactivity In case of a fire spread to the controlled areas, the fire extinguishing systems are activated. However, the extinguishing will be inoperable if the electricity supply is lost (except for the storage rooms). The consequences of this event will be of the same type as in case of lightning strike, as addressed in section 4.1. The calculations show that this extreme situation would lead to a release in the air of about 10 kBq to 100 kBq of alpha activity. As mentioned, the license of the MS controlled areas authorises an airborne release of up to 74 kBq per week.

It can be concluded that a forest fire causing a fire in the controlled area combined with the unavailability of the normal and vital power supply could lead to releases outside the building. However, these releases would be of the order of what has been considered as acceptable at the licensing of the MS building. Considering the sensitivity of the site, extra measures are anyway advisable in order to limit the risk and enhance the efficiency of the fire combating. Measures which can be envisaged to increase robustness of the installation Measures envisaged on the current infrastructure -

Installation of a water reserve tank on the site A sufficient on-site water reserve is essential as complement to the hydrant system. The dimensioning of the water capacity will be further assessed with the local fire brigades.

-

Cutting of pine trees in the surroundings of the controlled areas The forest management plan foresees in a gradual replacement over 20 years of pine trees by broadleaf trees. The latter are less sensitive in case of forest fire. Priority could be given to the replacement of the pine trees at short distance of the nuclear controlled areas.

Organisational measures -

Enhancement of the training of the internal IRMM on combating forest fires The combating of a fire at its early stage is essential. The preparedness of the internal fire brigade on combating forest fires could help in this way. The training should be focused on the use of the appropriate on-site means for the protection of the sensitive areas.

-

Asses with the local fire brigades the implementation of a cartography of the risk zones of the Geel-Mol-Dessel region Cartographies (scale 1/25.000 or 1/10.000) of the risk zones are experienced as a very useful tool to help to coordinate the interventions in case of fire.

-

Improvement of the monitoring of the forest fire risk in function of the meteorological conditions The monitoring in the Antwerp Province is managed by the fire brigade of Wuustwezel, but the spread of this information to the nuclear sites and the definition of appropriate prevention measures in case of alarm could be more

45

formalised. The purchase and maintenance of a local monitoring tool (for the four involved nuclear sites) could be also pursued.

Measures at the design of new installations -

At the design of the new nuclear facility, an appropriate fire-resistant roof cover has to be foreseen. An appropriate roof cover (e.g. with fire resistant roofing) will provide a protection against glowing ashes from forest fire. It should be also avoided that ashes can accumulate in the drainage systems or edges and dead ends on the roof.

-

The air inlet of the room ventilation has to be protected against the intrusion of glowing ashes. Appropriate grids could be installed on the air inlet in order to avoid the intrusion of glowing ashes. The measure can be combined with the installation of fire resistant filtering of the air inlet.

4.3 Terrorist attacks (aircraft crash) Conceivable events A large variety of terrorist attacks could be imagined but it is assumed in the Belgian stress tests methodology that the most extreme terrorist attack on a nuclear site would be the result of a deliberate crash of an airplane. It is clear that the IRMM site and in particular the MS building is not an easy target for this type of malevolent action, as the building is relatively small in surface and height. However, for the completeness of the stress tests assessment, it has been requested to investigate more in detail this scenario, its consequences on the safety functions and possible remedial measures to improve the protection level.

Assessment of consequences on safety functions The effect of the aircraft crashes on the integrity of the building has been evaluated. The consequences of the resulting kerosene fire and the actions that can be taken to mitigate them have been assessed with the help of experts from the Belgian Air Force and the local Fire Brigades of Mol and Geel. The common ICAO standard for civil aviation (‘‘International Civil Aviation Organisation’’, Airport Services Manual, DOC 9137ANI898) is used as basis. An investigation was done on the available equipment and organisation means. The potential releases of radioactivity as result of the combined effect of impact damages and kerosene fire have been also evaluated. The results and conclusions of the assessment are presented in the classified addendum to this report.

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4.4 Site specific impacts caused by toxic gases Use and transport of toxic gases in and around the site Situation on the IRMM site Diverse types of gases are commonly in use for experimental purposes in the IRMM installations and in particular in the MS building. These gases are provided mainly in standard 50 L bottles, which are stored in distribution cupboards or racks outside the buildings. The distribution is ensured by a network of stainless steel tubing in the building. The pressure of the distributed gas depends on the application and varies commonly between 0,75 bar and 5 bar. Occasionally some gases of variable toxicity have to be used for the experiments (e.g. N2O, CO). No tubing conducting such toxic gases is located within the controlled areas MS1/MS2. Some tubing which could contain toxic gas passes in the basement under the MS1 controlled area. At their delivery on the IRMM site, the gas bottles are stored in a centralised gas bottle storage, at the back side of the 060 ISM building, about 200 m away from the MS building. Nitrogen gas and argon gas are used in larger quantities and four fixed storage tanks are installed close to the MS building: -

liquid nitrogen: 3200 L and 1346 L tank;

-

argon: 2 x 1346 L tank.

These inert gases are used within the buildings for different kind of applications. The gases are not toxic as such, but could lead to asphyxiation in the case of a too high concentration in a habitable room space. Tank trucks for the delivery of gas bottles to the central store pass at about 70 m of the MS building. Trucks for the delivery of liquid nitrogen and argon approach the MS building for the filling of the fixed tanks.

Situation in the vicinity of the IRMM site At the neighbouring installations of VITO and Innotek, gases are in principle used in the same way as at IRMM. The closest facility is at about 200 m of the MS building. Tank trucks transporting toxic gases can pass in the neighbourhood of the site: -

the main road to consider is the Retieseweg (N118), which is at its closest location at 550 m of the MS building;

-

a small private road goes along the perimeter on the Western corner of the site. The road is at its closest location at 20 m of the MS building. However, passage of trucks on this road is prohibited (maximum 3,5 T allowed);

-

the closest street in the ‘‘Europawijk’’ district is located at about 50 m of the MS building. Traffic of trucks on this road is rather exceptional but can formally not be excluded.

At longer distances, transports of large quantities are possible on the canal BocholtHerentals (passing at 1,5 km North of the site) and on the railway between Geel and Mol (passing at 2 km South of the site). The major chemical industries which could release large amounts of toxic substances are located South of Geel and in the vicinity of Balen, at more than 8 km from the site.

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Smaller industries located more nearby in a radius of about 4 km could not create severe releases, except in case of fire.

Conceivable Conce ivable events Leakages in case of failure of fixed installations on the IRMM site Leakages of gas lines or gas connection devices within the MS building could occur by malfunction or an accidental rupture of tubing. A leakage, if significant and if not immediately detected, could lead to intoxication or asphyxiation of the personnel. Even if the leakage doesn’t occur within the controlled area, suction of the gas is possible due to the underpressure. On the contrary, it can be expected that leakages outside the building or a rupture of a gas bottle outside or on a transport truck will have no impact within the controlled areas: the quantities in use at IRMM are too small to create disturbances over a distance of more than a few meters. In the same way, a rupture of a nitrogen tank or argon tank will not create an asphyxiation risk in the controlled areas. Other buildings of primarily importance for the nuclear safety of the installations, like the electricity supply buildings and guards building will not be affected, for the same reason.

Leakages in case of accidents in the vicinity of the IRMM site Significant leakages and gas releases could occur after a road accident of a tank truck. The radius of risk area for intoxication around the accident location can be estimated, although it is strongly dependent on the inherent gas toxicity, on the leakage rate and on the meteorological conditions. Data are available in the literature and show that, commonly, for the most frequently transported toxic gases, a ‘‘damage distance’’ of a few tens of meters to a few hundreds of meters must be considered as the immediately endangered area (risk for fatality or injuries). Based on this and with respect to the traffic in the vicinity of the IRMM site, accidents on the N118 road close to the site or (hypothetically) in a street in the Europawijk could have an impact if the meteorological conditions are unfavorable. Releases from industries or from railway or water transport accidents which could happen but will be originated at longer distances will in principle only create disturbances, requiring e.g. confinement within the buildings.

In summary, following conceivable events with toxic gases could endanger in the short term the personnel: - non detected leakage of toxic or asphyxiating gases within the MS building; - accident with a truck transporting toxic gases on the road or a street close to the MS

building.

Consequences on the safety functions Prevention of criticality The considered conceivable events will not affect the criticality control.

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Confinement of the radioactivity Personnel working in the controlled areas could be affected and faint in the case of intrusion of toxic or asphyxiating gases (a sudden unpredictable fainting worker could create a local contamination if the person is just manipulating radioactive substances). From the moment that the abnormal situation is observed by colleagues, actions will be undertaken to alert the rescue teams and evacuate the victims and all other staff present in the controlled area. Adequate personal protection equipment (autonomous breathing apparatus) are available at the entrance of the building and in the fire brigade truck. Despite the possible health consequences for the affected staff, the events will have no impact on the confinement of the radioactivity, as: -

no devices in controlled areas require a continuous surveillance for safety reasons;

-

the evacuation of victims or potentially affected persons is done according to wellestablished procedures and there is no reason that this would induce an increase of the radiological contamination risk outside the controlled area.

For the long term, access to the controlled areas will be necessary for verifications, maintenance and replacing of ageing equipment. It can be expected that at that moment the cause of the leakage will be identified and remediated. Until this is done the interventions, if needed, can be organised with the adequate personal protective equipment.

Measures which can be envisaged to increase robustness of the installation installation As no conceivable events with consequences on the nuclear safety of the installations were identified, no related measure is defined. It is nonetheless foreseen by IRMM to install fixed oxygen monitors in the rooms where there is a potential asphyxiation risk. This action is taken as prevention of work accidents and will therefore not be followed-up in the frame of the present assessment.

4.5 Site specific impacts caused by explosive gases and blast waves gases Use and transport of flammable ga ses in and around the site Situation on the IRMM site Two underground Low/Medium Pressure natural gas lines (with pressure between 0,02 and 0,5 bar, diameter 160 mm) supply the heating installations of the 180 Heating building (belonging to VITO) and of the basement of the new 200 RMP building. The underground location of the lines is identified with regular warning stakes. At its closest location, one line passes at 150 m of the MS building. The closest heating installation is in the 180 Heating building, situated at 170 m of the MS building. In the building, the rooms hosting the heating devices are monitored with gas detection. Besides the natural gas supply, some flammable gases are in use in limited quantities for diverse devices, including also equipment in the MS building. The 50 L bottles are stored in distribution cupboards or racks outside the building and distributed through tubing in the building.

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No flammable gas is in use in the controlled areas except ‘‘P10’’ gas (which is a mixture of 90% argon and 10 % methane)14. P10 is needed for the supply of some monitoring equipment (proportional counters). Storage of bottles with flammable gases inside the controlled areas is not allowed. At the delivery, the gas bottles for use at IRMM are stored in the centralised gas storage at the back side of the 060 ISM building. Distance rules between the different types of bottles are respected, according to the applicable regulatory requirements. Finally, to complete the overview, it cannot be excluded that a car with LPG tank (Liquefied Petrol Gas) parks along the building. The use of gas bottles (e.g. propane or butane) for some works on the infrastructure is also an eventuality.

Situation in the vicinity of the IRMM site A gas reduction installation belonging to the gas distribution company is located close to the entrance of VITO, at about 250 m from the MS building. The gas is supplied by a Medium Pressure line (pressure of maximum 14,7 bar, diameter 100 mm) to three reduction cabins and further at low pressure to the described installations on the IRMM site and to VITO. Besides, the situation outside IRMM related to transports and industries is the same as described here above in section 4.4.

Conceivable events Failure of the natural gas supply outside the buildings Leakages outside the buildings could be created by damages on the gas reduction installation by a rupture of a line, e.g. during excavation works. In that case, the gas could ignite. In the case of an accident with natural gas supply, the fire brigades apply safety distances: -

zone 1: ‘‘House Burning Distance’’ or zone in which the heat of burning gas can cause the ignition of surrounding building structures;

-

zone 2: zone in which no ignition is expected over a certain elapsed time (the time that the fire brigade can start an intervention);

-

zone 3: safety perimeter.

For a ‘‘guillotine’’ rupture of a Medium Pressure gas line of 100 mm, the recommended15 zones 1 and 2&3 are respectively 20 m and 30 m (no difference between zone 2 and 3). A similar graded approach is requested to be followed if there is no ignition. In that case, the recommended zones 1 and 2&3 are respectively 30 m and 50 m. 14

There is contestation about the flammability of P-10, as it contains 90 % of inert gas (Ar). Some publications mention it as “non-flammable”. However, this gas can be ignited in some circumstances (with Lower Explosion Level 40%) and is for this reason classified as flammable.

15

The recommended distances for Medium Pressure gas lines mentioned here are not yet officially published. For a “guillotine” rupture of a High Pressure gas line of 100 mm, the (published) recommended zones 1, 2 and 3 are respectively 30 m, 60 m and 100 m in case of ignition and 50 m, 90 m and 100 m if there is no ignition.

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The comparison of the recommended distances for Medium Pressure with the location of the gas lines at IRMM shows that the MS building is not endangered.

Gas leakage on a heating installation inside the buildings A leakage on the heating installation inside the 180 Heating building will trigger an alarm. The possibility exists in that case to close manually the gas supply line from outside the building. If the intervention comes too late, an explosion could occur. Severe damages can be expected on the building but it can be excluded that the resulting blast wave will have a direct damageable impact on the MS building as it is at 170 m distance and the building structure will be protected by the 130 CRM building located in between. A blast wave could however impact the 90 Medium voltage building which is located at the other side of the road in front of the 180 Medium voltage building. In an extreme situation, the main diesel generators and the medium voltage switch room could be damaged.

Failure of other devices on the site A leakage due to a rupture of the tubing of a P10 gas line in a room of the controlled area will not create an explosion risk. The ventilation rate in normal circumstances in the controlled areas ensures at least 10 renewals per hour. The content of a full bottle of gas (50 L at 200 bar) is approximately 10 m3 at atmospheric pressure. If totally released in a room, the lower explosion limit will not be reached. An explosion of gas due to a failure of a bottle or tank outside the building cannot be excluded. This could locally damage the building structure. In the worst case a leaking gas cloud could be partially aspirated in the controlled area. Considering the relatively small quantities of gas that could be involved and the high ventilation rate of the controlled areas, it can be excluded that lower explosion limit will be reached.

Leakages due to transport accidents Transport accidents involving explosive gases could occur. Possible occurrences with road, rail and water transports are similar to those described in section 4.4. Depending on the quantities involved, the possible accidents are classified in categories. Road and rail accidents involving gas transports are filed in category III and transports on waterways in category IV. The spread of a possible fire ball calculated for the most extreme scenario of a BLEVE16 caused by a LPG tank transport accident on the road (category III) with 2 m/s wind speed is 100 m. The calculated damage distance (burning distance) with possibility of generation of secondary fires is 400 m. For a category IV transport, the calculated distances for the fire ball and secondary damages are respectively 200 m and 800 m. Considering the distance of the Retieseweg being the main traffic way close to the site site, the controlled areas of the MS building would not be directly endangered by a category III accident (the scenario of an extreme BLEVE accident in a street of the Europawijk close to the site is excluded as too hypothetical). The same conclusion can be drawn in the case of a rail accident or a larger category IV accident involving a transport on the canal Bocholt-Herentals. 16

BLEVE or Boiling Liquid Expanding Vapour Explosion

51

An indirect impact of a road of waterway accident is however possible, as a major accident e.g. on the Retieseweg could initiate a forest fire. This issue is addressed in section 4.2.

In summary, following conceivable events related to explosive gases or blast waves could have a direct impact on the controlled areas: - explosion in the 180 Heating building causing damages to the 90 Medium voltage

building with a partial or total loss of the electrical power supply; - explosion of a gas bottle or tank outside in the vicinity of the controlled areas; - transport accident with flammable gases on a main traffic way, initiating a forest

fire. The consequences of the forest fire are assessed in section 4.2 and will for this reason not be further addressed here.

Consequences on the safety functions Prevention of criticality The considered conceivable events will not affect the criticality control.

Confinement of the radioactivity In the case of an explosion creating in the 180 Heating building creates damages to the electrical power supply, the ventilation of the controlled areas could be partially of totally interrupted. In that situation the controlled areas will be evacuated but there will be in the short term no other consequences as the static confinement remains guaranteed. For longer periods, provisions will have to be taken for re-accessing the areas (see section 2.2.1 and 3.2 above). In the case of a severe explosion of a gas bottle or tank in the immediate vicinity of the controlled area, the building structure could be locally damaged. A possible breach in the static confinement will be compensated by the dynamic confinement function, which will remain operational. Releases of possible airborne contamination can be excluded.

It can be concluded that no conceivable events involving explosive gases or blast waves will lead to release of radioactive substances, unless the accident would initiate a secondary event like a forest fire. Damages by the explosion of flammable gases in the controlled areas are not excluded. Measures which can be envisaged to increase robustness of the installation Measures envisaged on the current infrastructure -

Installation of flow limiters on the distribution of flammable gases Flow limiters could be installed on the ¼’’ tubing, in principle close to the gas bottles, after the pressure regulator. They will limit the leakage in case of a ‘‘guillotine’’ rupture of the tubing inside the building.

52

Organisational measures -

Formal periodic verification of the absence of flammable gas bottles stored in the controlled areas or in the immediate vicinity of the controlled areas A periodic verification will provide a better guarantee that no bottles would be accidentally endanger the controlled areas. Temporary use of flammable gas (e.g. for infrastructure work) should be subject to a dedicated risk assessment.

computer-4.6 Site specific impacts caused by external attacks on computer based controls and systems Conceivable events A variety of cyber attacks can be imagined and the worldwide threat is rising with time. With respect to the current assessment, a large range of scenarios could be taken into consideration, e.g.: -

a direct targeted attack on a the Commission’s network, the IRMM networks or any software installed on servers or computers continuously linked to the networks;

-

a direct or indirect attack on software applications which are not or only occasionally connected to other computers.

-

a cyber-attack that could impair support infrastructure like telephony.

These attacks could cause the inoperability of the systems. Apparent or hidden malfunctions are conceivable.

Assessment of consequences on safety functions The equipment and applications of importance for the safe operation of the nuclear facilities of the MS building and using of controlled by software have been considered. The consequences of cyber attack scenarios in normal and abnormal conditions have been assessed. The results of the assessment are presented in the classified addendum to this report. It appears that some cyber-attack scenarios could disturb the operation of the institute and the nuclear installations but no scenario will have a significant impact on the nuclear safety of the MS building.

53

5 Loss of electrical power 5.1 Loss of offoff -site power Back--up power so source Back urce The back-up power sources for the IRMM site are described in section 1.4.3 of this report. In case of loss of off-site power, one of the two redundant diesel-generators G1 and G2 of 1000 kVA will ensure the electrical power supply to the vital grid. More particularly, with respect of the safety functions of the MS building, the vital grid will ensure the continuity of the supply to:

Figure 5.1: location of the diesel generators G1/G2

-

the extraction ventilators ensuring the dynamic confinement;

-

the safety surveillance, monitoring and communication systems;

-

the mist extinguishing system which would be activated in case of fire.

The start of the diesel-generators is fully automated. The connection to the vital grid of the safety devices of the MS building is ensured in less than 15 s (see table 1.1). Start-up tests of the diesels are scheduled on a monthly basis. Charge tests and checking of the sequences in the operating mode normal/emergency is planned on a quarterly basis.

on--site back back--up source Autonomy of the on Two ‘‘day-tanks’’ contain 2400L fuel each and are located close to the diesel-generators as immediate reserve. The tanks are continuous standby. The consumption of the diesel engine is 240L/h at its maximum power, meaning that the day-tanks provide autonomy of at least 10h (for both diesels). Two supplementary underground tanks close to the generator building have a capacity of 2 x 4900 L. The fuel is used as reserve and pumped to the day-tanks. Attention is paid that the underground tanks are refilled when a minimum reserve of 2000L is reached. The tanks provide an additional autonomy which would be in the worst case 8 h, starting with the tank filling is at its minimal level and the diesels at their maximum power. Considering that the fuel of both day-tanks can be used and that the underground tanks have a minimal filling, the total autonomy is approximately 28h (10h + 10h + 8h). From the moment the fuel reserves would decrease and the autonomy would become a concern, the power demand on the vital grid could be reduced to the most essential functions. This would save fuel consumption and increase the autonmoy.

54

Measures which can be envisaged to increase the robustness of the plant Organisational measure -

Increase the frequency of the refilling of the underground tanks A systematic could be introduced to refill the underground tanks more regularly (e.g. if the filling is done once the fuel capacity of the underground tanks has decreased below 5000 L, the autonomy can be increased with at least 12h).

5.2 Loss of offoff -site power and of onon-site site backback-up power sources back--up source Provisions in case of loss of the main back As mentioned in section 1.4.3 of this report, two additional redundant diesel-generators D11 and D12 of 50 kVA ensure an additional back-up in the case of loss of off-site power with both main diesel-generators inoperable. One diesel-generator is continuously running to guarantee its availability. The generator supplies electrical power to: -

the glove box extraction ventilators (2 for MS1, 2 for MS2);

-

one extraction ventilator per controlled area (1 for MS1, 1 for MS2).

On the contrary to the ventilation, the mist fire extinguishing system is not supplied by the small generators in the case of a failure of the normal and vital grid. Only the gas extinguishing system has an additional back-up with manual activation, independently of electrical grid. The fire monitoring systems in the buildings are supplied by dedicated batteries in case of loss of the grid. For the other safety surveillance and communication systems of the alarm centre, an uninterruptable power supply (UPS) system of 1000 VAh installed in the guard building. For the lighting of the rooms, emergency lamps are mounted on various strategic locations. The lights will automatically switch on if their power supply is lost.

back--up sources Autonomy of the supplementary back The fuel for the small generators D11 and D12 is provided by day-tanks of 2 x 1000L. The consumption of a diesel engine is 10L/h, meaning that the autonomy of one generator is about 100h. In an extreme situation, an additional fuel reserve could be provided by the underground tanks (if not yet consumed by the main generators). This would increase the autonomy by at least 200h. The batteries of the fire monitoring systems provide autonomy for 24 hours. The uninterruptable supply system for the alarm centre has a limited autonomy. It can be assumed that the surveillance and monitoring systems have a back-up autonomy of less than one hour. The autonomy of the emergency lights is about one hour.

55

foreseenn to prevent damage or release Actions foresee A loss of off-site power, combined with a loss of the vital supply grid will not generate immediate nuclear safety risks as far as the event is not combined with a major disturbance or accident. The priority action is to evacuate the nuclear controlled areas to protect the involved staff, as only underpressure is ensured, but not the normal full ventilation. It can be expected that in the first stage of such an event, sufficient communication means will still be operable and that the emergency lighting will function to allow the evacuation in a safe and controlled way. The inoperability of part of the fire extinguishing system will have to be compensated by organisational measures. In this case there is no immediate safety concern. But it will be preferable that the electrical power supply to the vital grid is restored without unnecessary delays. If the restart of the main diesel-generators appears to be impossible, the possibility exists to hire a temporary generator which has then to be connected to the vital grid.

Measures which can be envisaged to increase the robustness of the plant Organisational measure -

Write a working instruction on the actions to be taken in case of loss of off-site power and in case of loss of the main diesel-generators A working instruction with the breakdown of actions to be taken would increase the preparedness to face power interruptions.

Measure at the design of new installations -

Assess and optimise the autonomy of the new alarm centre The alarm centre will be reinstalled in the new 222 SHES building, which is currently under design. For this building, the foreseen UPS capacity has been drastically increased to 12.000 VAh. The essential systems to be connected to the UPS (surveillance, monitoring, communication, lighting, …) and the achieved autonomy has to be assessed, to ensure maximum disponibility.

5.3 Loss of off off--site power and loss of the ordinary back up source, and loss of any other diverse back up source black--out on the site Total black This situation is basically the same as the one discussed in section 5.2, except that all the electricity supply on the site would fail, which means that simultaneously: -

both the two off-site power supply lines would be lost or the normal electricity supply grid of the site would fail;

-

both the two redundant main diesel-generators G1 and G2 would be inoperable or the vital supply grid of the site would fail;

-

both the two redundant back-up diesel-generators D11 and D12 would fail.

56

No specific extra provisions have been taken into consideration at the design to face such a total black-out. Although the probability for such a cascade of failures seems rather low, one should consider that some external events (e.g. forest fire) could be at the origin of a loss of the off-site power with simultaneously an impact on the operability of the diesel-generators (this issue is also addressed in section 6.2 of this report). For this reason the total black-out of the site has to be considered as a ‘‘conceivable event’’.

Actions Actio ns foreseen to prevent damage or release A total site black-out will result in a total loss of the ventilation in the MS building. After evacuation of the controlled areas, actions will be taken to restore the power supply, with priority to the extraction on the glove boxes and rooms of the controlled areas.

Measures which can be envisaged to increase the robustness of the plant Measure on existing infrastructure -

Replace the existing diesel-generators D11 and D12 by movable diesel-generators groups and keep them in standby on an alternative location on the site The existing diesel-generators are old and will have to be replaced in the coming years. By introducing movable generators at another location on the site common mode failures by external events can be avoided. The generators should have enough power to be able to supply the essential safety functions (ventilation extraction, fire extinguishing and equipment alarm centre). Simple electrical devices to connect the generators to these systems could be installed.

5.4 Loss of primary ultimate heat sink [Not applicable, see section 1.4.2]

5.5 Loss of the primary ultimate heat sink and ‘‘alternate ‘‘alternate heat sink’’ sink’’ [Not applicable, see section 1.4.2]

5.6 Loss of the primary ultimate heat sink, combined with blackblack- out [Not applicable, see section 1.4.2]

57

6 Severe accident management 6.1 Organisation of licensee to manage the accident and possible disturbances 6.1.1 Organisation planned

The IRMM plan to deal with accidents and possible disturbances IRMM has an ‘‘Internal Contingency Plan’’ which deals with all emergency situations, crisis situations and situations when business continuity has to be guaranteed17. The contingency plan covers following events: -

fire or explosion;

-

injured, contaminated or irradiated person(s);

-

forced entry, demonstrative action, bomb threat ("security" issues);

-

criticality accident;

-

spread of contamination or atmospheric release;

-

major technical disturbance (loss of electrical power, leakage, …)

-

off-site event or concern that could have an impact on the institute.

The contingency plan is documented in procedures, working instructions and supporting documentation and templates.

Response according to the contingency plan The contingency plan organisation is applicable to incidents, accidents or any crisis situation. Depending on the event and its possible consequences, a small or a more ‘heavy’ organisational structure will be set up.

Crisis situation within working hours Should a safety-related or security-related event occur within working hours on the IRMM site, a response will be foreseen. Without going in the details of all instructions, following stages can be identified depending on the severity of the event: -

In the first stage of any occurrence, the responsibles of the concerned intervention teams will be contacted by the Alarm Centre. They will try to gather all the necessary information about the situation and they will carry out the immediate protective actions according to the respective emergency instructions. The head of the safety services (‘‘SHES’’) will be informed.

-

If the situation cannot be kept easily under control or if co-ordination is needed at site level (e.g. when rescue from outside is requested), the IRMM Director will be informed. A ‘‘Crisis Centre’’ will be set up, with the Director, the head of the safety services, the responsible of the relevant units and depending on the situation

17 It should be noted that the installations of IRMM are not integrated as such in the ‘‘Belgian National Nuclear and Radiological Emergency Plan’’. It is assumed that an accident could a priori not lead to an extreme situation necessitating coordination at national level. In case of a nuclear emergency situation, the coordination will be done at provincial level according to the Nuclear Emergency Plan for the Mol Region.

58

additional staff for expert support. They will decide on further actions and ensure the overall site co-ordination. -

If there is an increased need for external communication (contacts with Authorities, with families and with press), communication responsibles will be designated to assist the Crisis Centre.

-

If the situation escalates and the Authorities decide to set up a local Co-ordination Centre, an IRMM delegate will be sent for support.

The Crisis Centre will also establish a direct contact with the ‘‘Head Quarters’’ of the Joint Research Centre in Brussels. The Federal Agency for Nuclear Controls will be contacted and the Authorities will be notified according to the procedure in force. The complete organisational structure of the overall contingency plan is presented in the scheme on figure 6.1.

Figure 6.1: IRMM organisation scheme in case of a crisis situation The Crisis Centre can also be set up in the case of any off-site event.

59

If long term co-ordination if necessary, the ‘‘Business Continuity Plan (BCP)’’ can be activated. The BCP is established at JRC level and identifies the necessary measures and resources (including staff, information, equipment, and protection of premises).

Crisis situation outside normal working hours The continuous surveillance of the site and in particular the Alarm Centre is assured by a 24/7 guards team. In order to cope with possible incidents, accidents or disturbances outside the working hours, an ‘‘on call’’ support is ensured by three IRMM staff members, with following functions: -

on call ‘‘Leader’’ function for the overall coordination

-

on call ‘‘Radiation Protection’’ function for the support in case of nuclear events;

-

on call ‘‘Technical support’’ function.

Following response to anomalies or alarms is foreseen: -

Whenever the guards detect an anomaly, during an inspection round or when an alarm occurs on one of the monitoring systems in the Alarm Centre, the on-call Leader will be contacted. In function of the nature of the occurrence, the on-call Radiation Protection or the on call Technical support will be called for immediate support on-site. Other competent persons can also be contacted to provide assistance. If needed, outside help will be requested (e.g. 112 service).

-

If the situation cannot be kept easily under control, or if a co-ordination is needed on a site level (e.g. when outside help is requested), the on call leader will contact the IRMM Director or his substitute and all other suitable persons for appropriate assistance. The Crisis Centre will be put in place. As long as the Director or his substitute is not present on site, the on-call Leader will take the role of ‘‘Emergency Director’’.

Actors of the emergency plan In summary, following persons have a key role in the coordination of emergencies: -

the Crisis Centre staff: the Director and the general management staff members, including communication responsibles and depending on the circumstances staff having a particular expertise

-

the responsible of the Alarm Centre and the guards

-

the internal IRMM Fire brigade (approximately 15 persons)

-

the radiation protection officers (5 persons)

-

the technical support staff (approximately 15 persons)

-

the building responsibles and responsibles for the staff registration

-

outside working hours: the on call staff

The actions which are expected to be taken by these actors in case of emergency are summarized in dedicated written instructions. The contingency plan is trained at least annually at the level of the site. Partial exercises involving the main intervention teams are organised on a monthly basis.

60

Infrastructure of the contingency plan The IRMM infrastructure for the contingency plan covers the important locations on the site, the intervention equipment and the communication means. An overview is given in the tables below. Table 6.1: summary of the important locations for the Contingency Plan

coordination centres: -

Crisis Centre: 010 Main building, room 150

-

Alarm Centre: 080 Entrance building (guards building)

grouping points: -

first grouping point: main entrance hall of each building

-

second grouping point, in case of site evacuation: 081 Cafeteria

-

fire brigade grouping point : fire brigade garage in 140 Safety building

-

grouping point for the guards: 080 Entrance building (guards building)

radiological decontamination places: -

MS building, room 239 (entrance controlled area MS1)

-

MS building, room 99 (entrance controlled area MS2)

-

010 Main building, room 17a (entrance controlled area)

centralised first aid location: -

020 Van de Graaff building, rooms 1-2 (offices medical service)

Table 6.2: summary of the intervention equipment for the Contingency Plan

fire protection equipment : -

-

fire brigade truck, including: o water tank 1.500 L o high-pressure pump (350 L/min at 40 bar) o 3 x 90 m hose reels o Low-pressure fire-fighting equipment (hoses, adapters) o 6 ‘‘BA sets’’ (self-contained breathing apparatus)

nozzles,

intervention equipment in the buildings on the site: o approximately 300 portable extinguishers all over the site o 30 m hose reels o two BA-sets at main entrance hall of the major buildings)

first aid equipment : -

approximately 40 first aid dispensers and stretchers

-

iodine tablets (stock at medical service)

-

defibrillator in car of the guards and in cafeteria

61

radiation protection equipment : -

reserve of face masks at main entrance hall of all buildings

-

reserve of intervention equipment and decontamination equipment in radiation protection office of the MS building (room 55)

-

reserve dosimeters for interventions

centralised first aid location: -

020 Van de Graaff building, rooms 1-2 (offices medical service)

support equipment for evaluation of radioactive releases : -

software for release computation

-

meteorological monitoring station on 020 Van de Graaff tower

Table 6.3: summary of the communication equipment for the Contingency Plan

communication between intervention teams: -

pager system

-

walkie-talkie portphones (for fire brigade and guards)

-

mobile telephones

alert systems: -

evacuation sirens in the buildings

-

overall public address system

external communication: -

telephones and faxes

-

dedicated telephone line

-

dedicated external radio communication line with Geel Police

Support from outside Public rescue services Depending on the situation, support from outside can be requested through the 112 alert service and by direct call. In case of fire, the Fire Brigade of Mol will the first corps addressed for an intervention18. The fire brigade premises are at a distance of 7 km from the site and experience shows that the first assistance is able to arrive on the site in about 12 minutes after a call 18

The Mol fire brigade will be the first to intervene as the IRMM site and buildings are located on the community of Mol.

62

Support from the heading fire brigade of Geel (also at 7 km from the site) will be requested by Mol if needed. Ambulance assistance will also be requested. Concerning the security support, the Police of Geel19 will be contacted.

Support by the SCK•CEN Related to emergency situations, nuclear assistance can also be requested to the SCK•CEN which is nearby, at about 4 km distance. Over the last years, contracts are established with the SCK•CEN to cover: -

a 24/7 medical support in case of radiological emergencies, including a dedicated ambulance and a decontamination facility at the SCK•CEN premises;

-

the realisation of low level radiological measurements in the case that an incidental contamination of a person is suspected.

Other support Various other type of assistance can be necessary (e.g. specific decontamination support, cleaning services, specific tools or equipment, refueling of tanks, etc…). The main companies susceptible to be contacted are listed in an ‘‘emergency telephone book’’.

6.1.2 Possible disruption with regard to the measures envisaged to manage accidents and associated management Following disturbing factors have been identified which could possibly interfere and impede the appropriate management of the conceivable evaluated in this report: -

the accessibility to the site for external rescue could be difficult or hazardous

-

the availability of the external rescue could be reduced if the services are overwhelmed by calls for immediate support

-

the access to the affected installation could be difficult or hazardous

-

the habitability of the coordination centres (Crisis Centre and Alarm Centre) could be impaired

-

nearby installations on the site or in the vicinity of the site could create additional hazards

-

some communication means could be inoperable or disturbed

-

the main electrical power supply could be interrupted

-

instrumentation could fail

-

some intervention equipment could be of no use or difficult to use

-

some staff could be unavailable for support on the site.

19

The police of Geel has the responsibility for the first intervention as the address of IRMM is on the community of Geel.

63

Each of these factors could create potentially delays and lower the efficiency of the interventions with respect to the expected performances.

Limited accessibility of the site In the case of forest fire the access of the rescue through the main entrance could be endangered, depending on the wind direction. Other access ways are possible and fire corridors are foreseen for this purpose. Nevertheless the use of alternative entries will cause inevitably some delays. In case of extreme weather conditions like snow, heavy rainfall, hail, the accessibility to site will also be retarded. In the same way the accessibility of the site to on call staff and supporting staff can be impeded and cause delays before appropriate measures are taken.

Reduced availability of external rescue services It can be expected that for some events affecting a wide area, the rescue services will be overwhelmed by calls for help, e.g. in case of earthquake, flooding, forest fire and extreme rainfall or hail. Priority will be given to lifesaving interventions, which means that the fire brigade and ambulances could only be available in the longer term.

Limited access to the affected installation In the case of a loss of the confinement (e.g. by a major fire in the controlled area) with a risk for spread of contamination, the access will only be possible if the rescue services are equipped with protection equipment and until advice can be provided by a radiation protection expert or dangerous goods advisor (this situation is foreseen in the current IRMM contingency plan). In the case of flooding, the access to the basement of the MS building can be temporarily endangered with respect to the electrocution risks. The access to the affected installations can be totally impeached in the case a severe event leads to structural damages with risk for collapsing of the building.

Impaired habitability of the coordination centres Some events like earthquake or forest fire can endanger the coordination centres, which will then have to be evacuated. Alternative locations have to be found, possibly not on the site (e.g. in the case of forest fire or major spread of contamination). This will inevitably delay the overall coordination.

Hazards from nearby installations In the case of a forest fire additional hazards could be created by other installations than the only MS building, like the gas storage or potential releases from chemical stores. This could result in a preventive evacuation of intervention staff, or move to outside a safety perimeter.

Unavailability of communication means The communication equipment, especially the mobile telephony can be heavily disturbed and temporarily inoperable by saturation, especially if an event affects a wider area, e.g. the whole district around the site. This can happen in case of earthquake, heavy rainfall, storm or tornado, etc. Alternative communication channels exist with radio, pagers and public address, but it can be expected that the communication flow will be slowed down.

64

Unavailability of the main power supply Earthquakes or some extreme weather conditions could cause a loss of off-site power. The vital infrastructure will the normally be supplied by the dieselgenerators. A lightning strike on the MS building could cause a total inoperability of the electrical power supply to the building. Temporarily the whole electricity supply to the site could also be affected. In the case a forest fire or a gas explosion affects the area in the vicinity of the 090 medium voltage building, the transformers and diesel-generators could be both inoperable, causing a total black-out.

Failure of the instrumentation Failure of the instrumentation due to loss of power or damage to cabling is imaginable. The instrumentation related to the safety of the MS building can however be compensated by operational measures, e.g. by increasing the guarding and surveillance.

Unavailability of intervention means In case of fire, the flow of water for fire extinguishing through the hydrant circuit could be reduced as the water lines are already in use on other locations outside the site. The storage of intervention equipment in the fire brigade garage could be damaged or inaccessible due to an extension of a forest fire or other reasons.

Partial unavailability of staff for support An important fraction of the staff lives in the vicinity of the site. Many staff members have children at the European school, which is nearby. In the case of an event affecting not only the site but a broader area, it can be expected that some staff will not be available as priority could be given to understandable private concerns. This could happen in the case of earthquake, forest fire and extreme weather conditions. The table 6.4 summarises the possible disruption of the accident management measures depending on the events evaluated in the sections 2, 3, 4 and 5. The severity of the impact is more or less ‘‘graded’’ with respect to the expected time that the perturbation could stay: - : no major perturbation expected +: potential perturbation in the first hour of the event ++: perturbation is possible in the first day of the event +++: perturbation is possible over several days after the initiating event

65

Accessibility site

Availability external rescue

Access affected installation

Habitability coordination centres

Hazards nearby installations

Unavailability communication

Unavailability power supply

Failure instrumentation

Unavailability intervention means

Partial unavailability staff

Earthquake

-

++

++

++

+

+

+++

+

-

++

Flooding

-

+

+

-

-

+

-

+

+

+

Wind storm or tornado

+

++

+

++

-

+

+++

+

--

+

Heavy rainfall

-

+

-

-

-

+

+

-

-

-

Snow

++

+

-

-

-

+

++

-

-

++

Heavy hail fall

+

+

-

-

-

+

++

-

-

++

Lightning strike

-

-

++

-

-

-

+

+++

-

-

Forest fire

+

++

++

++

+

++

+++

++

++

++

Toxic gases

-

-

-

++

-

-

-

-

-

-

Explosive gases and blast waves

-

-

-

++

-

-

+++

-

-

--

Table 6.4: summary of the possible disruptions as function of the external events

From the assessment it comes out that the likelihood for side-effects and the impact of perturbations is the highest in case of forest fire. Some remedial measures are further discussed in the next section 6.2.

6.2 Organisation in case of a severe accident accident No ‘‘severe accident’’ from internal or external origin is conceivable for the MS controlled areas in a similar way as for nuclear power reactors or other major nuclear installations. However, to complete the current assessment and in line with the prescribed methodology and report structure, the consequences on the organisation in the case of a forest fire will be further considered in this section. Forest fire requires more specific attention as: -

the event could lead to substantial damages in the controlled areas;

-

several side-effects or disruptions can be expected;

-

the occurrence is not purely hypothetical like for other events and the likelihood tends apparently to increase as a result of climate change effects.

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6.2.1 Accident management measures for for managing the consequences of a forest fire

Before occurrence of damage Forest fire is included in the IRMM contingency plan as one of the possible ‘‘scenario’s’’. The main actions that will be triggered by the alarm centre and the crisis centre are: -

the evacuation of the buildings and if needed the evacuation of the site ;

-

the intervention of the IRMM fire brigades, including the reconnaissance, the connection and use of the hydrant system for extinguishing and protecting the buildings;

-

the immediate call for support of the public fire brigades; the call for other rescue if needed

-

the support by the guards for facilitating the access to the buildings and the site;

-

the confinement of the buildings with respect to the doors and windows and if needed to stop of the ventilation;

-

the external communication (to Authorities, JRC headquarters and press).

After occurrence of damage Specific measures to be taken after fire damage to the controlled area are -

the contamination control and estimation of the possible releases

-

the medical and radiological assistance to potentially affected personnel

-

the estimation of the damages, decontaminations, cleaning and repair.

Adequacy of the existing management measures and possible additional provisions -

Improvement of the emergency instructions to deal with the forest fires Although forest fire is already included in the IRMM contingency plan, the procedures could be adapted or complemented with more detailed instructions for the fire brigades (available means, sensitive areas to protect, etc.), the guards (surveillance and communication, opening of gates the site through the fire corridors), technical services (stopping ventilation, restoration of electricity supply if lost) and other actors. Appropriate training has to be foreseen.

6.2.2 Accident management measures and installation design features for protecting confinement integrity

Prevention of criticality It has been mentioned in the report that the absence of a criticality risk in the storage rooms is ensured in the case there is no alternative solution than extinguishing with water.

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Calculations have been performed and demonstrate that, with the current amount of material in the storage, there is a sufficient margin towards criticality (see section 3.2). A more in depth calculation should be done demonstrating that the margins are still ensured would the total amount of material change.

Need for and supply of electrical power Alternative back-up power supply could be necessary in case of forest fire. The possibilities are described in section 5.2.

Adequacy of the existing management measures and possible additional provisions -

In the case of an increase of the amount of nuclear material in the store, recalculation of the available criticality margin The calculation of the maximal amount of nuclear material providing still sufficient margin towards criticality even in the most extreme situations will ensure that there is no concern Would the margin be too low, specific instructions have to be given and included in the emergency instruction to prevent any use of water or foam on the storage.

6.2.3 Accident management measures currently in place to mitigate the consequences of loss of containment integrity and to reduce red uce releases to the environment No specific measures are taken other than those discussed in sections 6.2.1/ 6.2.2.

6.2.4 Specific points for each stage 6.2.1, 6.2.2 and 6.2.3

Organisation provisions A partial unavailability of staff can be expected in the case of a forest fire affecting the whole area around the site. The emergency procedures foresee replacements for most of the essential functions.

habitability Availability and habitabi lity of the coordination centres A forest fire can endanger the alarm centre (located in the 080 Entrance building) and the crisis centre (by default located in the 010 Main building). The back-up location for the crisis centre is the 100 Conference building or 080 Entrance building (for the future it is foreseen to install the back-up crisis centre in the 222 SHES). There is no formal back-up coordination centre foreseen in the case that the site has to be evacuated.

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Adequacy of the existing management measures and possible additional provisions -

Review of the emergency instructions in order to assess the redundancy of all essential functions With respect to the assessments made, it is desirable that for all essential functions dealing with accident management, at least two back-up persons are defined and formalised in the emergency instructions.

-

Designation of a back-up location for the IRMM Crisis Centre, outside the site An adequate back-up location (or locations) should be selected allowing the IRMM Crisis Centre to further coordinate the actions if the site is not accessible. This could be e.g. at the fire brigade premises of Mol or Geel.

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7 Conclusions and proposal for action plan Conclusion At the design and construction of the controlled areas of the mass spectrometry building in the 1960’s and 1970’s, safety provisions have been foreseen in compliance with the applicable regulations and standards. A rather limited attention was paid for possible events from external origin, in particular natural events. The experience with the accident in Fukushima has shown the necessity to re-assess the robustness of the installations. It appears also that the gradually deteriorating climate conditions have increased the probability of some natural hazards. The assessments made in this report have shown that for most of the extreme events which are envisaged, no releases are expected. Nonetheless several measures are envisaged to further improve the protection level.

Proposed action plan The envisaged measures were categorised in this report as follows: -

short term and medium term measures on the current Infrastructure (I.)

-

Organisational measures (O.)

-

long term measures to be considered at the design of the New installations (N.).

The following tables give a summary of the measures and the events for which they should apply, with a proposed timing. The implementation of the measures is spread over the period 2012-2014.

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Table 7.1: summary envisaged measures on current infrastructure Nr.

Envisaged action and motivation

Applicable Events

Timing

I1

Installation on extraction ventilator motors of a connection allowing to plug them to an alternative electricity supply

Earthquake

2014

In the situation that the electrical cupboards of the ventilators are totally damaged, it should be possible to install a temporary alternative electricity supply to the ventilator motors without delay.

I2

Improvement of fixation of safety-related electrical cupboards

Flooding Lightning Forest fire Earthquake

2013

Flooding

2013

Flooding

2013

Flooding

2014

Lightning

2014

Forest fire

2014

Forest fire

2013

The improvement of the anchoring of all safety-related electrical cupboards, where possible and necessary, will decrease the damage risk.

I3

Installation of appropriate water detection in the basements with alarm reported to the alarm centre A detection will allow starting remedial organisational measures in the early stages of a potential flooding of the basements

I4

Improvement of the protection against water intrusion of the ventilator rooms A basic protection by sealing the openings and placement of dams at the room entrances could delay the possible flooding damages to the equipment.

I5

Adequate transportable pump to be used in case of urgency A transportable emergency pump available on the site will allow starting quickly with the evacuation of the water from the basement. Such a pump could be installed on the fire brigade truck.

I6

Installation of an appropriate lightning protection of the roof of the MS building A lightning protection on the roof of the MS building will provide a basic protection and lower the risk for damages and initiation of a fire.

I7

Installation of a water reserve tank on the site The availability of water is essential. A sufficient on-site water reserve is essential as complement to the hydrant system. The dimensioning of the water capacity will be further assessed with the local fire brigades.

I8

Cutting of pine trees in surroundings of the controlled areas The forest management plan foresees in a gradual replacement over 20 years of pine trees by broadleaf trees. The latter are less sensitive in case of forest fire. Priority could be given to the replacement of pine trees surrounding the controlled areas.

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I9

Installation of flow limiters on the distribution of flammable gases

Explosive gases

2013

Replace the existing diesel-generators D11 and D12 by movable diesel-generators groups and keep them in standby on an alternative location on the site

Earthquake

2013

The existing diesel-generators are old and will have to be replaced in the coming years. By introducing movable generators at another location on the site common mode failures by external events can be avoided.

Lightning

Flow limiters could be installed on the ¼’’ tubing, in principle close to the gas bottles, after the pressure regulator. They will limit the leakage in case of a ‘‘guillotine’’ rupture of the tubing inside the building. I10

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Flooding Loss offsite power

Table 7.2: summary envisaged organisational measures Nr.

Envisaged action and motivation

Applicable Events

Timing

O1

Adaptation of the emergency instructions to deal with earthquake

Earthquake

2014

Flooding

2013

Flooding

2013

Forest fire

2013

Forest fire

2013

Forest fire

2014

Explosive gases

2013

The sequence of the appropriate measures to be taken once an earthquake of whatever intensity is observed has to be integrated in the emergency procedures.

O2

Adaptation of the emergency instructions to deal with the flooding of the buildings The sequence of the appropriate measures to be taken once flooding is observed has to be integrated in the emergency procedures. Appropriate training of the involved technical staff has to be foreseen.

O3

Continuous surveillance of the water level in the pool An abnormal increase of the level of the water pool on the site could be an indication of an obstruction. The installation of a level indication and the surveillance of the level could allow anticipating a possible a flooding and initiating on time remedial actions.

O4

Enhancement of the training of the internal IRMM on combating forest fires The combating of a fire at its early stage is essential. The preparedness of the internal fire brigade on combating forest fires could help in this way. The training on the use of the appropriate on-site means for the protection of the sensitive areas is also essential.

O5

Assess with the local fire brigades the implementation of a cartography of the risk zones of the Geel-Mol-Dessel region Cartographies (scale 1/25.000 or 1/10.000) of the risk zones are experienced as a very useful tool to help to coordinate the interventions in case of fire.

O6

Improvement of the monitoring of the forest fire risk in function of the meteorological conditions The purchase and maintenance of a local monitoring tool (possibly for the 4 involved nuclear sites) could be pursued.

O7

Formal periodic verification of the absence of storage of flammable gas bottles in the controlled areas or in the immediate vicinity of the controlled areas A systematic for a periodic verification will provide a guarantee that no bottles would be accidentally endanger the controlled areas. Temporary use of flammable gas (e.g. for infrastructure work) should be subject to a dedicated risk assessment.

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08

Increase the frequency of the refilling of the underground tanks

Loss offsite power

2014

Loss offsite power

2013

In the case of an increase of the amount of nuclear Accident material in the store, re-calculation of the available Management criticality margin

2013

A systematic could be introduced to refill the underground tanks more regularly (e.g. if the filling is done once the fuel capacity of the underground tanks has decreased below 5000 L, the autonomy can be increased with about 15h 09

Write a working instruction on the actions to be taken in case of loss of off-site power and in case of loss of the main diesel-generators A working instruction with the breakdown of actions to be taken would increase the preparedness to face power interruptions.

O10

The calculation of the maximal amount of nuclear material providing still sufficient margin towards criticality even in the most extreme situations will ensure that there in no concern Would the margin be too low, specific instructions have to be given and included in the emergency instruction to prevent any use of water or foam on the storage. O11

Review of the emergency instructions in order to assess the Accident redundancy of all essential functions Management

2013

It is desirable that for all essential functions dealing with accident management, at least two back-up persons are defined and formalised in the emergency instructions. O12

Improvement of the emergency instructions to deal with the forest fires

Forest fire

2013

Forest fire

2013

Although forest fire is already included in the IRMM contingency plan, the instructions could be adapted or complemented with more detailed instructions for the fire brigades, the guards, technical services and other actors. Appropriate training has to be foreseen. O13 O1 3

Designation of a back-up location for the IRMM Crisis Centre, outside the site An adequate back-up location (or locations) should be selected allowing the IRMM Crisis Centre to further coordinate the actions if the site is not accessible. This could be e.g. at the fire brigade premises of Mol or Geel.

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Table 7.3: summary measures to be considered at the design of new installations Nr.

Envisaged action and motivation motivation

Applicable Events

N1

Consider the review level earthquake as design basis for the new nuclear facility

Earthquake

N2

The building and the infrastructure should be designed in order to resist the review level earthquake as defined in the current assessment. Consideration should be given not to install safety equipment and the related electrical supply chain in the basement.

Flooding

If the safety equipment is installed at an appropriate level (a few tens of centimetres) above the ground level, the safety functions will remain guaranteed for any conceivable flooding of the site area.

N3

The new nuclear facility and the new building with alarm centre should be protected with lightning and surge protection.

Lightning

A protection of the respective buildings and their electrical circuits will lower the risk for damages and initiation of a fire.

N4

An appropriate fire-resistant roof cover has to be foreseen.

Forest fire

A fire resistant cover (e.g. with fire resistant roofing) will provide a protection against sparks from forest fire. It should be also avoided that sparks can accumulate in the drainage systems or corners and dead ends on the roof. N5

The air inlet of the room ventilation has to be protected against the intrusion of glowing ashes.

Forest fire

Appropriate grids could be installed on the air inlet in order to avoid the intrusion of glowing ashes. The measure can be combined with the installation of fire resistant filtering of the air inlet. N6

Assess and optimise the autonomy of the new alarm centre The alarm centre will be reinstalled in the new 222 SHES building, which is currently under design. The essential systems to be connected to the UPS (surveillance, monitoring, communication, lighting, …) and the achieved autonomy has to be assessed.

Loss offsite power

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European Commission Joint Research Centre -- Institute for Reference Materials and Measurements Title: Complementary safety assessment for the nuclear laboratories at the JRC-IRMM Author(s): Pierre Kockerols, Andreas Fessler

2012 --- 78 pp. --- 21.0 x 29.7 cm

Abstract This report summarises the assessments made in order to evaluate the robustness of the nuclear laboratories of the IRMM against hazards from external origin. The evaluation is conducted in the frame of the Belgian Stress Tests. In line with the requirements of the Federal Agency for Nuclear Control, a standardised methodology is followed, addressing all conceivable events from external origin and their consequences on the safety of the installations. Based on the evaluation, a number of measures are identified which will further improve the safety provisions on the site.

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z

As the Commission’s in-house science service, the Joint Research Centre’s mission is to provide EU policies with independent, evidence-based scientific and technical support throughout the whole policy cycle. Working in close cooperation with policy Directorates-General, the JRC addresses key societal challenges while stimulating innovation through developing new standards, methods and tools, and sharing and transferring its know-how to the Member States and international community. Key policy areas include: environment and climate change; energy and transport; agriculture and food security; health and consumer protection; information society and digital agenda; safety and security including nuclear; all supported through a cross-cutting and multi-disciplinary approach.

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