Safety Countermeasure of Onagawa NPS after Great East-Japan Earthquake and Tsunami November 14, 2014 University of California at Berkeley

HIgashidori

Tohoku Area

Fukushima Daiichi

Onagawa

130km from the epicenter

Fukushima Daini

Epicenter

Tokai No.2 0

100

200

km miles 0

100

200

Akiyoshi Obonai Takao Watanabe Kazuo Hirata Tohoku Electric Power Company Copyright © March, 2012 Tohoku Electric Power Co., Inc. All rights reserved.

Tohoku Electric Power Co., Inc.

1

Why do we need improving safety? On March 11,2011, we were able to respond appropriately against earthquake and tsunami. However, this success does not guarantee for the next potential disaster or accident. We need continuous effort to keep safety.

Tohoku Electric Power Co., Inc.

2

Presentation Outline 1. Lesson from Onagawa and Fukushima 2. Immediate Upgrades 3. Further Safety Improvements 4. Summary

Tohoku Electric Power Co., Inc.

3

Lesson from Onagawa (1) 1. Re-evaluate the tsunami height Although tsunami height on 3/11 was lower than the site grade, there was not a lot of margin. Maximum tsunami height:13m (Tsunami prediction:13.6m) Site grade:13.8m (before earthquake:14.8m) New findings: Interlocking movement of tsunami sources was observed in the 3/11’s tsunami.

2. Secure water tightness. There is a possibility that unexpected leak path still exists like the internal flooding of unit 2.  Backup method is important in case the water tightness was broken. Tohoku Electric Power Co., Inc.

4

Lesson from Onagawa (2) 3. Reduce the possibility of fire  The fire, which occurred from the non-safety related switch gear panel of unit 1, did not spread to the safety-related equipment by effort of inhouse firefighting team.  However, if this fire spread to the safety-related equipment, the situation would become worse. 4. Further improvements  For example, the various ways for logistics support. Tohoku Electric Power Co., Inc.

5

Lesson from Fukushima Daiichi 1. Protect from flooding 2. Enhance Electric Power Supply System 3. Enhance Cooling System 4. Enhance Confinement System 

Minimize the amount of radioactive release to the environment when severe accident occurred.

Evacuees: Approx. 335 thousand by Government Headquarters of Great East Japan Earthquake (Dec 21, 2011)

5. Fortify Emergency Response Center

Tohoku Electric Power Co., Inc.

6

Step for improving safety ▼3/11/2011 - Great Earthquake

1st

step

- Fukushima Daiichi accident

 Immediate Safety Upgrades -

Tsunami protection

-

Extended loss of AC Power

2nd step Lesson from Onagawa

 Further safety improvement

Lesson from Fukushima

-

Meet the requirement of regulatory body

Safety countermeasure for severe accident

 Filed the “safety screening permission” to the regulatory body (December 27,2013) Tohoku Electric Power Co., Inc.

7

Immediate Safety Upgrades Enhancement

Countermeasure

Status

Construction of levee & sea flood walls

Deployed

Replacement of building door to the watertight sealed door

Under work

Power supply car

Deployed

Air-Cooled EDG

Deployed

Alternative water injection pump car

Deployed (3 vehicles)

Alternative mobile sea water pump car

Deployed (2 vehicles)

Spare motor for sea water pumps

Deployed

Protect from Flooding

Electric Power Supply

Cooling System

Tohoku Electric Power Co., Inc.

8

Immediate Upgrade : Construction of Levee

The top: 17m above sea level

Levee (3.2m) Site grade:13.8m

Tohoku Electric Power Co., Inc.

9

Immediate Upgrade : Enhance Electric Power Supply (1) Step1: Movable Power-Supply Car  Rate Output: 400kVA X 4 units  Deploy on a ground at 22m above sea level

Step2: Installation of Air-cooled Diesel Generator  Rate Output:5,000kVA X3 units  Set up on a small hill at 52m above sea level

Tohoku Electric Power Co., Inc.

10

Immediate Upgrade : Enhance cooling system HydroSub Systems

(deployed on September 28, 2012) Pump capacity: 1,800 ton/h, Pump head:120 m Number of vehicle:2, Hose length:4,200m

Submerged Seawater Pumps

Engine

Reactor Building

P

RPV

PCV

Intake sea water

Reactor Seawater Pump

RCW Hx

Reactor Cooling Water Pump Sea Water Pump area

Sea Water Hx Building

Tohoku Electric Power Co., Inc.

RHR Hx

Residual Heat Removal Pump

Hx : Heat Exchanger

11

Continuous Training Continuous Training and Improvements (kaizen) Electric Bus Connection Box (Power Car and M/C switch gear)

①Simulator Training

②Cable Connection Training with Power Supply Car

(Station Black Out)

Outdoor water inlet nozzle Indoor water outlet nozzle

Reactor Building

Filtrate tank Filtrate tank

③Air-Cooled Diesel Generator Start-Up Training

Condensate make up nozzle

Kaizen! Quick and Easy

Attach a nozzle to connect fire engine hose with just one touch

④Water Injection Training using Fire Engine

Tohoku Electric Power Co., Inc.

12

Further Safety Enhancement Enhancement

Countermeasure

Re-evaluate Tsunami New levee height

Status Under work

Re-evaluate Design basis ground motion Further seismic reinforcement

Under work

Confinement System Filtered PCV (Primary Containment System)

Under work

Stationary Gas Turbine Generator

Under work

Add DC (Direct Current) Battery

Under work

Mobile heat exchanger

Under work

Electric Power Supply

Cooling System

Emergency Response Fortify Emergency Response Center Tohoku Electric Power Co., Inc.

Planning

13

Reevaluate tsunami prediction  We set up new tsunami sources.

 Next, we considered the uncertainties of tsunami sources (fault location, disproportion of slip, fault rupture pattern, etc.).

New evaluation of maximum tsunami height: O.P. 23m. (note: O.P.is Onagawa Peil, and datum plane for construction, )

Considered tsunami sources Main tsunami sources

Interplate earthquake

Oceanic intraplate earthquake Earthquake that occur within the upper crust

Standard fault 基準断層モデル model

Consider the uncertainty of slip quantity, すべり量,アスペリティの形状・位置 location of asperity and hypocenter 破壊開始点の不確かさを考慮

Magnitude

March 11/2011 Great East Japan earthquake

Mw9.0

Tsunami earthquake（1896, Meiji-Sanriku earthquake)

Mw8.3

Normal fault type earthquake（1933, SyowaSanriku earthquake etc.）

Mw8.6

Submarine active faults (F2,F-4fault,F-5fault,F-6～F9fault)

Mw6.2～ 7.0

Onagawa NPS 女川地点

Shift the アスペリティ asperity area 位置を移動

Shift the アスペリティ asperity area 位置を移動 （

Tohoku Electric Power Co., Inc.

Hypocenter 破壊開始点 Shift the 位置を移動） Hypocenter )

Uncertainties of tsunami sources (Example of March 11 type tsunami)

14

Further Safety Enhancement: New Levee (1)

Vertical鋼管式鉛直壁 sea wall made of 延長：約680m steel pipe (total length:680m) Concrete placement

Levee made of earth and cement セメント改良土による堤防 (total 延長：約120m length:120m) Vertical sea wall made of steel pipe (Height: 15m (O.P.+29m)) Present Levee :Height 3.2m. (O.P.+17m)

Original site grade: 13.8m

Foundation improvement

Levee height: 15m Foundation

Directly founded on bedrock

Tohoku Electric Power Co., Inc.

total height:29m

Bedrock

15

Further Safety Enhancement: New Levee (2) Platform for constructing new Levee

View from the harbor

New Levee

View from the site Tohoku Electric Power Co., Inc.

Photo of steel pipe 16

Reevaluate the design basis seismic ground motion (DBSGM) North-South Direction

Observed Earthquake Response Spectrum: East-West Direction 応答スペク トルＳｓ－Dh 応答スペク トルＳｓ－Bh ４．７_B2_PNS_hagi_spl.waz ４．７_B2_PEW_hagi_spl.waz s

500

Findings:

0. 1

20

100 50

20 10

10

度

0. 01 5

10

(cm/s) 5

March 11

0. 01

April 7

2

1

1

2

0. 1

速

10

1 0.5

the value of the observed earthquake spectrum exceeded that of the design basis seismic ground motion in a short period

10 0

Velocity (cm/sec)

10 0

100

1 0.

00 1

0.5

0.2

0. 00 1

0.2

0.1 0.01

0.02

0.05

0.1

0.2

0.5

1

2

5

0. 1

0. 1

度

(h=0.05) 10 0

200

速

(cm/s)

10

10 00

1

10 00

10 00 0

10 0

1000

200

50

(c m)

(c m/

(h=0.05)

10 00 00

(c m/ s

1

500

m)

10

10 00 00

1000

Velocity (cm/sec)

(c

10 00 0

)2

)2

応答スペク トルＳｓ－Dh 応答スペク トルＳｓ－Bh 201103111446_B_7ch_B2_ns(PN)hagitori_spc.waz 201103111446_B_8ch_B2_EW(PN)hagitori_spc.waz

10

0.1 0.01

周 期(秒)(sec) Period

0.02

0.05

0.1

0.2

0.5

1

2

5

10

We decided to set up new “Design Basis Seismic Ground Motion”

周 期(秒) Period (sec)

Design Earthquake Motion Ss-D （Horizontal） (Earthquake ground motion with the site specific earthquake source locations) Design Earthquake Motion Ss-B （Horizontal） (Earthquake ground motion with no such specific source locations)

Tohoku Electric Power Co., Inc.

17

Review the earthquake pattern

Set up new design basis ground motion Earthquake pattern

Reference earthquake

Interplate earthquake

3/11/2011, Great Tohoku earthquake

Oceanic intraplate earthquake

4/7/2011 Miyagikenoki-earthqake

Land plate Ocean trench Inland Crustal movement

Oceanic plate Interplate earthquake (plate boundary)

Movement of plate

Oceaniac interplate earthquake

Earthquake that occur within the upper crust

Submarine active faults (F2,F-4fault,F-5fault,F-6～F9fault) Earthquake pattern and earthquake occurrence location

Tohoku Electric Power Co., Inc.

18

Set up new Design Basis Seismic Ground Motion (Ss) Reference earthquake for review, and Design Basis Seismic Ground Motion (DBSGM) Magnitude

Design basis ground motion (H: Horizontal, V: Vertical) Ss-1H (640gal) Ss-1V (320gal)

M7.1

(cm/s)

度

(cm/s)

5

度

(cm/s)

)2

/s

1

速

10 5

度

0.

(cm/s)

01

5

2

2

1

1

0.5

0.5

0.5

0.5

0.2

0.2

0.2

0.2

周 期(秒) Period (sec)

1

2

5

10

0.1 0.01 0.02

0.05 0.1

0.2

0.5

1

周 期(秒) Period (sec)

Response spectrum for Ss-1

Tohoku Electric Power Co., Inc.

2

5

20

10

1

0.5

10

0.1 0.01 0.02

0.05 0.1

0.2

0.5

1

2

5

10

0. 1

20

2

0.2

2

0

20

1

0.05 0.1

1

0

50

10

100

50

0.

2

0.1 0.01 0.02

(h=0.05)

10

0 速

10 01

Vertical

1

0

50

20

0.

)

200

10

100

50

1

500

20

200

50

50 速

10

0.

F－６断層～Ｆ－９断層による地震（UD方向） EQ caused byＦ-６～Ｆ-９fault *2

1000

0

10

0

500

Horizontal

1

基準地震動Ss-2

(c m

(h=0.05) 50

1000

DBGM Ss-2V 3/7/2011 After shock *2 2011年４月７日宮城県沖型地震（M7.5）

*2 method using fault model

(c m

)

00

/s

(c m

00

)2

━・━

EQ caused byＦ-６～Ｆ-９fault （EW）*2

0

100 50

20

0. 01 5

EQ

━‥━

velocity

度

━・━

velocity

速

1

velocity

velocity

50

0.

………

(c m

20

10

200

10

20

100

0

200

3/7/2011 After shock *2

0

Vertical

1

10

━━━

2011年４月７日宮城県沖型地震（M7.5） F－６断層～Ｆ－９断層による地震（NS方向） F－６断層～Ｆ－９断層による地震（EW方向） caused byＦ-６～Ｆ-９fault（NS）*2

………

(h=0.05)

0

500

)

20

0

1000

DBGM Ss-2H 基準地震動Ss-2

━━━

*1

50

)2 /s

(c m

50

00

Horizontal

10

20

500

3/11/2011 Great Tohoku EQ 基準地震動Ss-1

2011年東北地方太平洋沖地震（UD方向）

(h=0.05)

1000 1

DBGM Ss-1V

………

*1 remove the effect of the surface ground for observed record at bed rock

(c m

)

00

(c m

10

━・━

━━━

20

基準地震動Ss-1 2011年東北地方太平洋沖地震（NS方向） 2011年東北地方太平洋沖地震（EW方向） 3/11/2011 Great Tohoku EQ （EW）*1

00

3/11/2011 Great Tohoku EQ（NS）*1

00

DBGM Ss-1H

………

10

━━━

)2

Induced by fault (F-6 ～F-9)

/s

Inland crustal movement

Ss-2H (1000gal) Ss-2V ( 600gal)

0

M7.5

(c m

4/7/2011, After shock

00

Oceanic interaplate earthquake

50

M9.0

00

3/11/2011, Great Tohoku earthquake

10

Interplate earthquake (plate boundary)

20

Reference earthquake for review

10

Earthquake pattern

0.

01

0.1 0.01 0.02

0.05 0.1

0.2

周 期(秒) Period (sec)

0.5

5

周 期(秒)(sec) Period

Response spectrum for Ss-2

19

10

Further Safety Enhancement : Additional Seismic reinforcement (1/2)  Status of seismic-resistant work  Based on the findings of 3/11/2001(Great Earthquake) and 4/8/2011 (aftershock), additional seismic reinforcement has been under work for pipe, cable, sea water intake structure, and reactor building.

Installation of additional support

Example: seismic reinforcement for pipe

Tohoku Electric Power Co., Inc.

20

Further Safety Enhancement : Additional Seismic reinforcement (2/2)  Status of seismic-resistant work

example: Seismic reinforcement for reactor building operating floor

Before

Add the steal beam

Add the steal beam

After

Increase the strength of wall Tohoku Electric Power Co., Inc.

(Photo of steel brace installation)

21

Further Safety Enhancement : Filtered PCV System The characteristics of FCVS (Filtered Containment Vessel system) of Onagawa NPS is;  Install the FCVS inside the reactor building.  Decontamination Factor (DF): for aerosol > 1000, and we plan to install iodine filter. Release from the roof of the R/B Stack

Reactor building

Rupture disk

Hardened vent system

MO

Dry well

Rupture disk

※

MO

RPV

Suppression Chamber

MO ※

※

MO

※Isolation valve is designed to operate outside the secondary containment system by manually.

Tohoku Electric Power Co., Inc.

PCV

22

Further Safety Enhancement :

HPAC (High Pressure Core Cooling System)

Key feature  DC (Direct Current) power supply is not necessary for starting. (It can be started manually at the field.) HPAC (High Pressure Cooling System)

New

Movable alternative Battery and charger



RCIC



Alternative pump

Connection Point

RPV RCIC Pump

PCV Tohoku Electric Power Co., Inc.

RCIC turbine

HPAC Pump

HPAC turbine

Condensate Storage Tank Reactor Building

Outside

23

Further Safety Enhancement : Alternative mobile heat exchanger system  Purpose It works as the ultimate heat sink. (It works instead of RCW and RSW.)  Configuration Mobile heat exchanger + mobile sea water circulation system (Hydrosub) Capacity:1440m3/h/unit (when output pressure is 1.2MPa) Reactor Building Heat exchanger

RPV

Alternative mobile heat exchanger units

RHR

Mobil sea water circulation unit

Capacity:18.6MW (when sea water temperature is 26℃) Heat exchanger

PCV

Heat exchanger

RSW RCW Sea

Tohoku Electric Power Co., Inc.

24

Further Safety Enhancement : Alternative power supply system Enhance AC power system Permanently-installed facilities Gas turbine generator: set up at high ground and secure diversity from design base EDG. Install light oil tank in the basement for operating mobile equipment during 7days. Enhance DC power system Permanently-installed facilities Increase the number of batteries :supply DC for more than 24 hours.  Alternative mobile battery charger units Mobile battery charger: supply DC power for more than 24 hours.

Mobile DC Power system)

Mobile car

Reactor Building

Gas Turbine Generator

Capacity: 2000AH

Light oil tank for EDG (330kL X 2)

EDG

Connecting port (DC) Connecting port (AC)

Light oil tank M/C

 Number of unit:6  Capacity:400kVA/unit

Tohoku Electric Power Co., Inc.

 Number of unit:2  Capacity: 45000kVA/unit

25

Further Safety Enhancement : Fortify ERC (Emergency Response Center)

Fortify ERC for sever accident Key Features Seismic-isolation building Thick skeleton for radiation shielding Artist Rendition of Emergency Response Center once completed

(Less than 100mSv/7days when SA occurred)

Diverse communication tool Exclusive diesel generator

Tohoku Electric Power Co., Inc.

26

Further Safety Enhancement : PRA evaluation Total core damage frequency (CDF) = 6.2 X 10-5 /reactor・year (unit2) ⇒ We plan to conduct PRA after implementing SA countermeasure.

Tsunami

Internal Event (transient, LOCA)

2.2 X 10-5 /reactor・year

(Exclude severe accident management countermeasure ) 2.0X 10-5 /reactor・year

2.0X 10-5 /reactor・year Tohoku Electric Power Co., Inc.

27

Road Map :Pursuit of safety  We have taken various safety countermeasure after 3/11/2011.  We will continue to make efforts to enhance safety.

Prevent the recurrence of a similar accident at Fukushima Dai-ichi

▼Present

▼3/11/2011

Safety Shutdown

Immediate

Pursue the safety Further Safety 更なる安全対策 on going basis Improvement

upgrades

Lesson from Onagawa and Fukushima

Tohoku Electric Power Co., Inc.

Meet the requirement of new regulation

28

Conclusion  On 3/11/2011, we were able to respond appropriately.  There is no end of pursuing nuclear safety  Always consider the new findings.  Careful preparedness is necessary.

 Challenging point  How many safety countermeasure (Defense In Depth) do we need?  How safe is safe enough?

Thank you for your kind attention! Tohoku Electric Power Co., Inc.

29