Guidance on completing a Radiation Risk Assessment using Unsealed Radionuclides These guidance notes should be read before completing the radiation risk assessment form. They should be read in conjunction with the Trust’s Risk Management Strategy and Policy (found on Freenet under Risk management strategy and policy ). A separate risk assessment form should be completed for each radionuclide used unless it is deemed sensible to put them altogether. If this is the case, then an explanation should be inserted. If the radionuclides are the same but used in a very different way, then a separate form is required. General risk assessment may be added to this form if it is easier. The radiation risk assessment form is not meant to be prescriptive but may be tailored to the individual situation (eg removing control measures which are not relevant and adding others which are) so long as the format is adhered to. This form may be used as a prior risk assessment, reviewing current ones as well as when an event occurs. 1 Persons at Risk Consider who might be harmed and if any pregnant or young people are involved. Enter the maximum number of radiation workers who may be involved and if they have had training. Under the “other persons involved” note down the number of people (not radiation workers) who may be affected (eg domestics staff, builders etc..). 2 Dose Assessment The whole body and extremity dose rates (mSv/h) can be calculated using data from table 1 if there is no previous data available (eg data of external exposure obtained from TLD/film badge results). Information on radionuclides not listed may be obtained from the Radiation Safety Group (RSG). Radionuclid e

A

B

C

Emission

Point source at 30cm*

Contact with 5ml syringe *

Tenth Value Layer (TVL)# of lead (mm) [γ only]

β γ γ γ γ γ β γ γ γ β β β β

8.62 E-2 7.29 E-4 3.90 E-4 5.16 E-4 9.94 E-4 2.61 E-4 1.08 E-1 2.79 E-4 6.04 E-5 1.97 E-4 1.18 E-1 -

1.1

11

0.6 0.6 1.2 0.4 43 0.4 0.09 0.29 24 -

2,000

> 20,000

> 40,000

200 – 2,000

2,000 – 20,000

20,000 – 40,000

20 - 200

200 – 2,000

2,000 – 20,000

2 - 20

20 – 200

200 – 2,000

0.2 – 2

2 – 20

20 - 200

0.02 – 0.2

0.2 – 2

2 - 20

< 0.02

< 0.2

2000

Reasons for categorisation Early transient erythema – ICRP85 Below erythema level

500 – 2000

500 : legal limit

150 – 500

< 150 : non classified level

50 – 150

(100mGy) No clinically relevant functional impairment – ICRP 103. Also including nonradiation worker (50mGy)

< 50 Table 2b

In the example given above, the max extremity dose EEX(b) = 5.5 which gives a consequence score is 1.

b Obtaining the Likelihood Score The likelihood score (between 1 – 5) can be obtained from the table 3 for each hazard and then noted down in the boxes provided Score

Frequency

1

Rare

Description This will probably never happen or recur

2

Unlikely

Do not expect it to happen or recur but it is possible it may do so

3

Possible

Might happen or recur occasionally

4

Likely

5

Almost Certain

Will probably happen or recur, but it is not a persisting issue / circumstance Will undoubtedly happen or recur, possibly frequently.

Table 3

c Obtaining the Risk Score The risk is the likelihood of harm occurring together with an indication of how serious that harm could be. Risk rating = Likelihood score x Consequence score Using table 4, find the risk rating (1 – 25). CONSEQUENCE

Rare (1) Catastrophic (5) Major (4) Moderate (3) Minor (2)

Negligible (1)

5 4 3 2 1

LIKELIHOOD Possible (3)

Unlikely (2) 10 8 6 4 2

15 12 9 6 3

Likely (4)

Almost certain (5)

20 16 12 8 4

25 20 15 10 5

Table 4

If the likelihood score is thought to be 3 and the consequence score is 2 (from whole body dose calculations above), then the risk rating = 3 x 2 = 6

The risk rating (between 1-25) corresponds to a risk score (between 1 – 4) as given in table 5. Note this down in the table. First written by : Date first written

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Risk Score

Risk

1

Very Low risk

2

Low risk

3

Moderate risk

4

High risk

Description Local investigation where appropriate Contributory factor(s) to be identified; discuss with local management the need for any changes in practice, policies, procedures, education or training. Identify contributory factors. Discuss at the local radiation governance meeting. Action plans to be monitored centrally. Report incident immediately to manager/head of department. Inform risk manager. Full investigation to be undertaken including interview with staff and identification of root causes. Action plans to be monitored centrally. To be reported to the Radiation Board.

Table 5

From the example above, with the risk rating being 6, the risk score (obtained from table 5) = 2

4 Control Measures State the type of shielding suitable for the radionuclide used (e.g. lead for I-131, Perspex for P-32). If shielding is adopted, it should have an appropriate thickness: Gamma Radiation: The thickness of lead should be greater than or equal to the TVL of the radionuclide (see table 1, column C). However, the attenuated dose should still be checked to ensure that it does not exceed any dose limit given in table 6. Beta Radiation:

10mm of Perspex should provide adequate shielding for all Beta emitters listed in table 1 excluding Y-90 and I-131.

A list of control measures have been given as a prompt. These may or may not be applicable to the situation being assessed. If it is not applicable or not being carried out, explain why not under the “If no, explain why not” column. Otherwise give details under the other column. For other control measures which are relevant but not listed, please add extra rows. The chance of contamination spread can be significantly reduced by ensuring that gloves are used and that all work is carried out on spill trays which are lined with absorbent materials. Movement of radioactive materials also needs to be considered to ensure that accidental spillages are not a regular occurrence and the chance of significant contamination from the spillage is minimised by adopting an appropriate movement procedure

5 Radiation Risk Quantification after control measures are in place Assess what the doses will be (as above) after control measures are put in place and note these down. Again these values should be annual doses. EWB(a) example: There is a significant reduction in dose rate after introducing shielding (control measure) to stand behind during manipulations and shielded storage when the activity is not being used. If a shield containing 11mm of lead is introduced, then the whole body annual dose can be calculated as EWB(a) = 4.31/ 10 = 0.431 mSv. 6mm Perspex is also added before the lead shield to absorb the beta particles. EEX(a) example: Dose-sharing techniques are now introduced during syringe manipulation resulting in half the time spent being exposed from direct extremity contact. The annual extremity dose is then calculated as EEX(a) = 5.5/2 = 2.75 mSv.

The limit for non-classified workers and members of the public are given in table 6. Pregnant staff may come under the category of “members of the public” in this exercise. If any of the annual dose values after control measures have been adopted exceeds the respective limits given in table 6 then further action needs to be taken reduce this to within the limits. If this is not possible, then the member of staff would need to be classified. This should be noted in section 6. First written by : Date first written

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Whole body Extremities Skin (Contamination)

Non-classified Radiation workers (mSv) 6 150 150

Members of the public (mSv) 1 50 50

Table 6

Calculate the risk probability (described above) using the dose estimations post control measures EWB(a) and EEX(a). Obtain the consequence score, the likelihood rating and the risk score as before. If any further action is needed to reduce the risk score for each hazard, note that in the appropriate column. The number of hazards identified in section 3 should be the same number as those in section 5 after control measures are in place. 6 Hazard Identification & Control Measures for Incident Situations Note down situations where incidents could occur. Identify the best action to take when the incident occurs so that people are as safe as possible first. ( This could mean shutting down an area !) 7 Action Plan Any action as well as improvements required to reduce the risks should be included in the “Action required” section. The person responsible for carrying out the action and the date the action should be done needs to be inserted. When the action has been carried out, the “date completed” needs to be added as well as a signature from the person who carried it out. 8 Area Designation Risk assessments are a way of indication what an area should be designated as. Sometimes after carrying out the risk assessment, the area may change its designation. All this needs to be addressed in the space provided. An area can be designated as controlled or supervised for various different reasons. Areas need not be permanent. Some reasons for designating an area are as follows : Controlled Area: -

If increased security and restriction of access to that area is required. To reduce the spread of contamination which is likely. If a person is likely to receive a dose higher than the dose limits given in table 6

-

to keep conditions under review to determine if the area needs to be controlled In labs where only small quantities of very low energy radioactive materials are used. To reduce the spread of contamination which may occur.

Supervised Area:

9 Approval Once the form is completed, the person(s) carrying out the risk assessment should sign and date it and get the Head of department / section or lab manager to approve it. A member of the Radiation Safety Group should then sign it to say that it has been noted. 10 Summary All the hazards and control measures (group them if possible) far should noted in the summary table. A small list has been provided but it may not all be relevant or sufficient and extra columns may need to be added. A tick should be placed in the appropriate box to demonstrate how the each hazard has been addressed by at least one control measure.

First written by : Date first written

D. Purfield 27th Nov 08

Doc ref : Reviewed by :

V 4.1 DP on 14/12/09

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