the facts in the recovery process of fukushima nuclear accident (kawano)

8/2/2019 The Facts in the Recovery Process of Fukushima Nuclear Accident (Kawano)

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All Rights Reserved 2011The Tokyo Electric Power Company, Inc. 0

The Facts in the Recovery Process ofFukushima Nuclear Accident

March 21, 2012

@IAEA IEM, ViennaAkira Kawano

Tokyo Electric Power Company


2/76


What I will present

1.How the Earthquake and the Tsunami affectedthe Power Supply at 1F and 2F sites ?

2.How the Accident Developed and was Stabilizedat 1F and 2F Sites ?

3.How We Responded to the Accident at 1F and2F Sites ?

4.Summary5.Reference


3/76


How the Earthquake and the Tsunami Affectedthe Power Supply at 1F and 2F Sites ?

Unit 6Unit 5Unit 1Unit 2

Unit 3Unit 4

Unit 1

Unit 2Unit 3

Unit 4

Fukushma Daiichi(1F) Fukushma Daini(2F)


4/76


Overview of Fukushima Daiichi NPS (1F)

and Fukushima Daini NPS (2F)

Plant UnitIn

Operation

Since

Plant

Type

Power

Output

(MWe)

Main

Contractor

Pre-earthquake Status

1F

1 1971.3 BWR-3 460 GE Operating

2 1974.7 BWR-4 784 GE/Toshiba Operating

3 1976.3 BWR-4 784 Toshiba Operating

4 1978.10 BWR-4 784 HitachiShutdown for maintenanceFull core offloaded to spent

fuel pool

5 1978.4 BWR-4 784 Toshiba Shutdown for maintenance

6 1979.10 BWR-5 1100 GE/Toshiba Shutdown for maintenance

2F


2 1984.2 BWR-5 1100 Hitachi Operating




5/76


4A4B

4D 4C

4E

DG

4B

DG

4A

DG

3B

DG

3ADG

2B

DG

2A

DG

1B

DG

1A

3A3B

3C3D

3SA3SB

2A2B

2C2D

2E

2SA2SB

1A1B

1C1D

1S

Shutdown by earthquake

Shutdown by Tsunami

Power supply of Unit 1-4 @ 1F after Tsunami

The DGlost the function due to either M/C failure, loss of

sea water system, or DG main unit failure.

Okuma Line 1L, 2L: Receiving circuit breaker damaged in earthquake

Okuma Line 3L: Renovation work in progress

Okuma Line 4L: Circuit breaker shutdown by protection relay activation

Ohkuma4L

Ohkuma3L

Ohkuma2L

Ohkuma1L


6/76


5A

5C

5B

5D

DG

5A

DG

5B

DG

HPCS

DG

6A

DG6B

5SA-1 5SA-2 5SB-25SB-1 6A-1 6A-2

HPCS6C

6B-1 6B-2

6D

Shutdown by earthquake

Shutdown by Tsunami

Survived after tsunami

Power supply of Unit 5/6 @ 1F after Tsunami

Futaba

1L

Futaba

2L

Yonomori 2LYonomori 1L

For transmitting

power

For transmitting

power


7/76


Damages of transmission line

& Shinfukushima substation by earthquake

500kV Disconnector275kV Circuit Breaker

- About 10 km away from both 1F and 2F site- Important switchgear station from which electricity of 1F & 2F is transmitted to Tokyo area

Transmission tower collapse

Collapse CGeoEye

Collapse of filled soil & sand

Tower collapse


8/76All Rights Reserved 2011The Tokyo Electric Power Company, Inc. 7

6.9kV 6.9kV

2F Offsite Power was secured after the TsunamiOffsite Power

500kV66kV

H STr

Unit #1, 2 STr Unit #3, 4 STr

/

EmergencyPower for Unit #1

/1H 1A 1B

6.9kV

/ /2H 2A 2B

/

3H 3A 3B

6.9kV

/ /

4H 4A 4B

One 500 kV line was available.

66 kV lines were outage because of scheduledmaintenance and substation trouble but recovered.

Many power centers and motors were damagedbecause of the flooding.

PPPP




/

P: Cooling Pumps

/ : Diesel Generator

/P

/P

/P

/P

Tomioka Line Iwaido Line



Integrity of Power Supply System After the Tsunami at 1F and 2F

*1 functionality lost due to inundation of power panels *2 functionality lost due to the damage of sea water system

Power panelCan/can

not be

usedPower panel

Can/can

not be

usedPower panel

Can/can

not be

usedPower panel

Can/can

not be

usedPower panel

Can/can

not be

usedPower panel

Can/can

not be

usedPower panel

Can/can

not be

usedPower panel

Can/can

not be

usedPower panel

Can/can

not be

usedPower panel

Can/can

not be

used

DG 1A DG 2A DG 3A DG 4A DG 5A(*2) DG 6A (*2) DG 1A DG 2A (*2) DG 3A (*2) DG 4A (*2)

DG 1B DG 2B

air-cooled(*1) DG 3B

DG 4Bair-cooled

(*1) DG 5B(*2) DG 6B

air-cooled DG DG 2 (*2) DG 3 DG 4 (*2)

HPCS DG (*2) DG 1 DG 2 (*2) DG 3 DG 4

M/C 1C M/C 2C M/C 3C M/C 4C M/C 5C M/C 6C M/C 1C M/C 2C M/C 3C M/C 4C

M/C 1D M/C 2D M/C 3D M/C 4D M/C 5D M/C 6D M/C 1D M/C 2D M/C 3D M/C 4D

M/C 2E M/C 4E HPCS DG

M/C M/C 1H M/C 2H M/C 3H M/C 4H

M/C 6A-1 M/C 1A-1 M/C 2A-1 M/C 3A-1 M/C 4A-1

M/C 6A-2 M/C 1A-2 M/C 2A-2 M/C 3A-2 M/C 4A-2

M/C 6B-1 M/C 1-1 M/C 2-1 M/C 3-1 M/C 4-1

M/C 6B-2 M/C 1-2 M/C 2-2 M/C 3-2 M/C 4-2

M/C 5SA-1 M/C 1SA-1 M/C 3SA-1

M/C 5SA-2 M/C 1SA-2 M/C 3SA-2

M/C 5SB-1 M/C 1SB-1 M/C 3SB-1

M/C 5SB-2 M/C 1SB-2 M/C 3SB-2

P/C 1C P/C 2C P/C 3C P/C 4C P/C 5C P/C 6C P/C 1C-1 P/C 2C-1 P/C 3C-1 P/C 4C-1

P/C 1D P/C 2D P/C 3D P/C 4D P/C 5D P/C 6D P/C 1C-2 P/C 2C-2 P/C 3C-2 P/C 4C-2

P/C 2E P/C 4E P/C 6E P/C 1D-1 P/C 2D-1 P/C 3D-1 P/C 4D-1

P/C 2A P/C 3A P/C 4A P/C 5A P/C 6A-1 P/C 1D-2 P/C 2D-2 P/C 3D-2 P/C 4D-2

P/C 2A-1 P/C 5A-1 P/C 6A-2 P/C 1A-1 P/C 2A-1 P/C 3A-1 P/C 4A-1

P/C 1B P/C 2B P/C 3B P/C 4B P/C 5B P/C 6B-1 P/C 1A-2 P/C 2A-2 P/C 3A-2 P/C 4A-2

P/C 5B-1 P/C 6B-2 P/C 1B-1 P/C 2B-1 P/C 3B-1 P/C 4B-1 P/C 1S P/C 3SA P/C 5SA P/C 1B-2 P/C 2B-2 P/C 3B-2 P/C 4B-2

P/C 5SA-1 P/C 1SA P/C 3SA

P/C 2SB P/C 3SB P/C 5SB P/C 1SB P/C 3SB

DC125V mainbus panel A

DC125V P/C

2A

DC125V mainbus panel 3A

DC125V mainbus panel 4A

DC125V P/C

5A

DC125V DISTCENTER 6A





DC125V mainbus panel B

DC125V P/C

2B

DC125V mainbus panel 3B

DC125V mainbus panel 4B

DC125V P/C

5B

DC125V DISTCENTER 6B





A RHRS A RHRS A RHRS A RHRS A RHRS A RHRS A RHRS A RHRS A RHRS A

B RHRS B RHRS B RHRS B RHRS B RHRS B RHRS B RHRS B RHRS B RHRS B

SW

- -

Regularuse

P/C

P/C 1A

Seawater

system

DC

power

supply

125V

DC

EmergencyDG

M/C

Regularuse

Emergency

use

M/C 2SB

M/C 2SA

M/C 3SA

M/C 3SB

M/C 2B

M/C 3A

M/C 5BM/C 4B

M/C 5AM/C 4A

M/C 3B

M/C 1S

M/C 1

M/C 2A

Emergencyuse

M/C 1A

Unit 3 Unit 5Unit 4 Unit 6

- -

Fukushima DaiichiUnit 1 Unit 2

Fukushima DainiUnit 1 Unit 2 Unit 3 Unit 4

1F:No off-site power available 2F:Off-site power survived

DG

6.9KVM

/C

480VPC

DC

O: operable X: damagedSea Water System



2. How the accident developedand was stabilized at 1F & 2F

Sites?



Fukushima Daiichi Units 1 - 4 Fukushima Daiichi Units 5 & 6 Fukushima Daini Units 1 - 4

Progress made by each plant towards cold shutdown (outline)

Units 1-3 in operation

Unit 4: outage in progress

[Power supply] Total loss of off-sitepower supply and DG

[Sea water system] Total loss

Water injection using IC, RCIC,HPCI

PCV Venting, SRV operation& Sea water injection

Switch to freshwater

Heat removal route has beencontinuously improved

Currently the closed cyclecooling is in function

Sea water was initially injected intothe spent fuel pool; currently

injecting freshwater

Outage in progress

[Power supply] Emergency DG 6Bstart up

[Sea water system] Total loss

3/19

Alternative RHRS wasstarted and the spent fuel

pool and reactor were cooled

Increase in spent fuel pool

temperature to near 70C

3/20

Units 5, 6 cold shutdown

Installation of temporary RHRS

Installation of temporary powersupply

In operation

[Power supply] One off-site powersupply system secured

[Sea water system] Total loss apartfrom Unit 3

3/12

Unit 3 coldshutdown

Units 1, 2, 4

Water injection using MUWC

3/14

RHR startup

Water injection using RCIC

3/14

Units 1, 2 cold shutdown3/15 Unit 4 cold shutdown

RHRC motor was replacedInstallation of temporary power

supply



-1000

1000

3000

5000

7000

3/11

12:00

3/11

18:00

3/12

0:00

3/12

6:00

3/12

12:00

3/12

18:00

3/13

0:00

3/13

6:00

3/13

12:00

3/13

18:00

3/14

0:00

3/14

6:00

3/14

12:00

3/14

18:00

3/15

0:00

3/15

6:00

3/15

12:00

3/15

18:00

3/16

0:00

0.00

2.00

4.00

6.00

8.00

10.00

3/11

12:00

3/11

18:00

3/12

0:00

3/12

6:00

3/12

12:00

3/12

18:00

3/13

0:00

3/13

6:00

3/13

12:00

3/13

18:00

3/14

0:00

3/14

6:00

3/14

12:00

3/14

18:00

3/15

0:00

3/15

6:00

3/15

12:00

3/15

18:00

3/16

0:00

7.47,7.54,7.61MPa abs

8.7MPa abs

7.0MPa abs

0.000

0.200

0.400

0.600

0.800

1.000

3/11

12:00

3/11

18:00

3/12

0:00

3/12

6:00

3/12

12:00

3/12

18:00

3/13

0:00

3/13

6:00

3/13

12:00

3/13

18:00

3/14

0:00

3/14

6:00

3/14

12:00

3/14

18:00

3/15

0:00

3/15

6:00

3/15

12:00

3/15

18:00

3/16

0:00

0.38 MPa abs

0.723MPa abs

RxW

ater

Level[mm]

RCIC

HPCS No Operation( Inoperative due to submersion of power source and inoperative auxiliary cooling system)

SRV

MUWC

RHR

PCV Vent

S/C Pressure (MPa)

D/W Pressure (MPa)

Earthquake14:46

Tunami15:23

R

xPressure

[M

Pa]

D/W

&S/C

Pressure[MPa]

0(TAF)

3:50 ~ DepressurizationPressure Control

0:00 ~

3:45 ~

(18:30Vent LineConfiguration Completed

Cold Shut Down14:46

Overscale

Restoration of RHR system

2F Unit 1 Plant Parameter and Operation



Operators initial response

MSIVs closed manually, and reactor

pressure controlled by SRVs.

RCIC actuated manually to maintain

reactor water level. RCIC repeated

automatic trip due to high water level

signal and manual restart.

MUWC actuated for alternative

water injection measure introduced

for Accident Management, as stated

in EOP manual for seamless water

injection.

Reactor depressurized and RCIC

stopped due to steam pressure

decrease.

Water level maintained by MUWC.

Sea

Steam

Water

Condensate Storage

Tank

RPV

Reactor Building

Heat Exchanger Building

Heat rejection byopening SRVs

Temperatureincrease

Tsunami floodingInoperable by

flooding

Equipment cooling system was notavailable.

RHRC Pump

RHRS Pump

RHR Pump

RCIC MUWC

MSIV

SuppressionChamber

(S/C)

Response at Main Control Room and TSC



0

1

2

3

4

5

6

7

8

3/11 3/12 3/13 3/14 3/15

(MPa [gage])

3/11 16:15 Reactor depressurization

started (SRV automatically opened)

3/14 10:05

LPCI and S/C

cooling and spray

by RHR(B)

3/14 13:40

Cold shutdown3/12 0:00

MUWC started

3/11 15:36 - 3/12 4:58

RCIC Operation

(intermittent)

-1000

-500

0

500

1000

1500

3/11 3/12 3/13 3/14 3/15

(mm)

Out of measurement range

3/11 16:15

Reactor depressurization started

(SRV automatically opened)

Successful Reactor Cooling during Transient

Reactor Pressure (Unit 1)Reactor Water Level (Unit

1)

Securing uninterrupted water injection throughout the

depressurization process with RCIC at high pressure condition andMUWC at low pressure condition was a critical factor for successfulreactor cooling.



0

20

40

60

80

100

120

140

3/11 3/13 3/15 3/17 3/19

3/12 06:2007:47

S/C injection by FCS(A)

3/12 07:10 D/W spray

3/12 07:37 S/C spray

3/13

11:3213:26 14:2914:37

D/W spray

0

50

100

150

200

250

300

3/11 3/13 3/15 3/17 3/19

kPa[gage]

3/14 01:24

RHR(B) started with

S/C cooling mode

3/17 20:0320:20Water transfer from

Condenser to S/C via

CST to monitor

Condenser water level

3/13

11:3213:26

14:2914:37

D/W spray

3/12 06:2007:45

S/C injection by FCS(A)

3/12 07:10 D/W spray

3/12 07:37 S/C spray

S/C Temperature (Unit 1)S/C Pressure (Unit 1)

S/C water temperature reached 100C (212F). It eventually increased up to about 130C (266F).

Water injected to S/C through Hydrogen Recombiner cooler discharge line in orderto mitigate temperature and pressure increases.

Alternative injection to reactor using MUWC switched to D/W spray, then S/C spray.

S/C temperature decreased after restoration of RHR.

EOP includes an alternative water injection measures employing MUWC .

Flexible approach to cool S/C using Hydrogen Recombiner worked well.

Efforts to Control Temperature and Pressure in PCV



Preparation for Venting

PCIS and SGTS actuated to secure isolation of the PCV and

maintained negative pressure of the reactor building.

Judging from the increasing PCV pressure trend and projectedrestoration time, as a back-up plan, TSC decided to make PCV ventline up ready.

PCV pressure went up to about 280 kPa [gage] before restoration ofRHR, but did not reach its design maximum pressure 310 kPa [gage].

PCV vent line up was made ready as a back-up plan. This would enable feed and breed cooling to avoid potential

core damage.

(As restoration of cooling capability was successful and coldshutdown was achieved, venting was not conducted actually.)



0.000

0.200

0.400

0.600

0.800

1.000

3/11

12:00

3/11

18:00

3/12

0:00

3/12

6:00

3/12

12:00

3/12

18:00

3/13

0:00

0.53MPa abs

0.954MPa abs

0.00

2.00

4.00

6.00

8.00

10.00

3/11

12:00

3/11

18:00

3/12

0:00

3/12

6:00

3/12

12:00

3/12

18:00

3/13

0:00

7.28,7.35,7.41MPa abs

8.7MPa abs

7.0MPa abs

-3000

-1000

1000

3000

5000

3/11

12:00

3/11

18:00

3/12

0:00

3/12

6:00

3/12

12:00

3/12

18:00

3/13

0:00

)(Amm

)(Bmm

In Operation(Over Scale)

RxWater

Level[m

m]

IC

HPCI No Operation

SRV No Operation

FP/Fire Engine

PCV Vent

Fuel Range (A) (mm)

Fuel Range (B) (mm)

Rx Pressure (A) (MPa)

Rx Pressure (B) (MPa)

S/C Pressure (A) (MPa)

D/W Pressure (B) (MPa)

19:04Sea Water

Order for Vent Preparation 0:06

4:00Fresh Water 80t 14:53

18:18 - 2521:3014:52

Earthquake14:46

Tunami15:27

Operation Unclear

Order for Vent

8:03 14:30 D/W Pr decrease confirmed

Unit 1 R/BExplosion 15:36

Core Damage Started due toMAAP Analysis

Rx

Pressure

[MP

a]

D

/W

&S/C

P

ressure[MPa]

1F Unit 1 Plant Parameter and Operation

0(TAF)Rx water level data revealed incorrect afterward



-4000

-2000

0

2000

4000

6000

3/11

12:00

3/11

18:00

3/12

0:00

3/12

6:00

3/12

12:00

3/12

18:00

3/13

0:00

3/13

6:00

3/13

12:00

3/13

18:00

3/14

0:00

3/14

6:00

3/14

12:00

3/14

18:00

3/15

0:00

3/15

6:00

3/15

12:00

3/15

18:00

3/16

0:000

2

4

6

8

10

In Operation (Over Scale)

0.00

2.00

4.00

6.00

8.00

10.00

3/11

12:00

3/11

18:00

3/12

0:00

3/12

6:00

3/12

12:00

3/12

18:00

3/13

0:00

3/13

6:00

3/13

12:00

3/13

18:00

3/14

0:00

3/14

6:00

3/14

12:00

3/14

18:00

3/15

0:00

3/15

6:00

3/15

12:00

3/15

18:00

3/16

0:00

7.44,7.51,7.58MPa abs8.7MPa abs

7.0MPa abs

0.000

0.200

0.400

0.600

0.800

1.000

3/11

12:00

3/11

18:00

3/12

0:00

3/12

6:00

3/12

12:00

3/12

18:00

3/13

0:00

3/13

6:00

3/13

12:00

3/13

18:00

3/14

0:00

3/14

6:00

3/14

12:00

3/14

18:00

3/15

0:00

3/15

6:00

3/15

12:00

3/15

18:00

3/16

0:00

0.53MPa abs

0.954MPa abs

RxWater

Level[m

m]

RCIC

HPCI No Operation

SRV

FP/FireEngine

PCV Vent

Fuel Range (A) (mm)

Fuel Range (B) (mm)

CAMS D/W(A)(Sv/ CAMS S/C(A)(Sv/



S/C Pressure (MPa)

D/W Pressure (MPa)

19:Sea Water


Depressurization~18:00

Earthquake14:46 Tunami

15:27

(2:55) Operation confirmed

(11:00Vent LineConfiguration Completed

Unit1 R/BExplosion15:36


Rx

Pressure

[MP

a]

D

/W

&S/C

P

ressure[MPa]

1F Unit 2 Plant Parameter and OperationUnit3 R/BExplosion11:01

Impact sound6:00-6:10

Valve Condition Unclear

Order for Sea Water InjectionPreparation 12:05

2Valves Open

Small Vent Valves Opened

(13:25)Out of Service Judged

0(TAF)



0.000

0.200

0.400

0.600

0.800

1.000

3/11

12:00

3/11

18:00

3/12

0:00

3/12

6:00

3/12

12:00

3/12

18:00

3/13

0:00

3/13

6:00

3/13

12:00

3/13

18:00

3/14

0:00

3/14

6:00

3/14

12:00

3/14

18:00

3/15

0:00

3/15

6:00

3/15

12:00

3/15

18:00

3/16

0:00

0.53MPa

0.954MPa

0.00

2.00

4.00

6.00

8.00

10.00

3/11

12:00

3/11

18:00

3/12

0:00

3/12

6:00

3/12

12:00

3/12

18:00

3/13

0:00

3/13

6:00

3/13

12:00

3/13

18:00

3/14

0:00

3/14

6:00

3/14

12:00

3/14

18:00

3/15

0:00

3/15

6:00

3/15

12:00

3/15

18:00

3/16

0:00

7.44MPa,7.51MPa,7.58MPa8.7MPa

7.0MPa

-4000

-2000

0

2000

4000

6000

3/11

12:00

3/11

18:00

3/12

0:00

3/12

6:00

3/12

12:00

3/12

18:00

3/13

0:00

3/13

6:00

3/13

12:00

3/13

18:00

3/14

0:00

3/14

6:00

3/14

12:00

3/14

18:00

3/15

0:00

3/15

6:00

3/15

12:00

3/15

18:00

3/16

0:00

I n Operat ion(Over Scale )

RxWater

Level[m

m]

RCIC

HPCI

SRV

D/D-FP

FP/Fire Engine

PCV Vent

Fuel Range (A) (mm)

Fuel Range (B) (mm)

Fuel Range (mm) Wide Range (mm)



S/C Pressure (MPa)

D/W Pressure (MPa)

16:30Sea Water


Earthquake14:46 Tunami

15:27

Unit1 R/BExplosion15:36


Rx

Pressure

[MP

a]

D

/W

&S/C

P

ressure[MPa]

1F Unit 3 Plant Parameter and OperationUnit3 R/BExplosion11:01

Order for Preparation17:12

0(TAF)

(11:36) Trip

Automatic Start(12:35)

(16:03)

(2:42) Stop

13:12Sea WaterFresh Water9:25

(8:41Vent Line Configuration Completed

~9:08Depressurization

(22:15)Stop due to running out of fuel

After HPCI shut down, water injectionusing D/D FP was implemented, howevernot possible due to high reactor pressure



3. How We Responded to theAccident at 1F & 2F Sites?

- What difficulties existed- What were effectively utilized

- How the difficulties were overcome- Testimonies



Establishing an alternative method to inject water into the

reactor pressure vessel (RPV)

Venting of the primary containment vessel (PCV)

Recovery of the most important instrumentations:

reactor water level

reactor pressure

drywell pressure

wet-well (suppression chamber: S/C) pressure

Recovery of the lights in the control rooms and other powersupply sources

What 1F site focused on during March 11-15

M j A ti iti t F k hi D ii hi U it 1



Activities were done in complete darkness due to lack of power sources.

Work in complete darknessIn the service building. Manyscattered objects were alsoon the floor.

Temporary power supplyConnect temporarybatteries to recoverinstrumentations.

Major Activities at Fukushima Daiichi Unit 1

Factors disturbing the recovery work (inside the building)

Scram

response

Preparationsfor waterinjection

Preparations

for venting

Waterinjectionstarted

Venting

Deterioratingoperabilitydue to the

tsunami

M j A ti iti t 1F



Image of a power supply cart

Used batteries taken from cars for recovery of important

instrumentations. Put Engine-Generators to provide power for the control room

lightings and PCV vent valve actuation.

Tried to connect a mobile power supply vehicle to P/C 2C/4Dwith temporary cable. The hydrogen explosion of Unit 1&3

caused damage of the temporary cable.

Scram

response


Preparations

for venting


Venting

Deterioratedoperabilitydue to the

tsunami

Major Activities at 1F

Factors disturbing initial recovery of instrumentations and power supply

Hurdles for the work:

Darkness and suspensions dueto aftershocks, tsunami alarms,

Puddles, openings of manholes,

debris and other obstaclescaused by the tsunami,

Influence of the hydrogenexplosions



Number of Aftershocks Greater than M 5.0

3/11Dates (from March 11, 2011 to Dec. 5th, 2011)

12/54/1

DailyNum

berofAftershock

sGreaterthanM

5.0

CumulativeN

umberofAftersho

cksGreaterthanM5.0

On March 11th alone

155 times > M 5.0

37 times > M6.03 times > M7.0

Total during first week358 times > M 5.0




Instruments were monitored wearing a full face mask with a flashlight incomplete darkness

Supervising (2)Supervising at a deputysupervisors desk wearing

a full face mask incomplete darkness

Supervising (1)Check indicated values onlywith a flashlight in completedarkness


Factors disturbing the recovery work (inside the buildings)

Scram

response


tsunami


Venting


Preparations

for venting

M j A i i i 1F U i 1



Many obstacles on access routes disturbed access to the field.

Vehicles had to avoid passing over fire protection hoses laid in the field.

Most of the prepared communication tools between the ERC and thecontrol room were unavailable.

Scram

response


tsunami


Venting


Preparations

for venting

Major Activities at 1F Unit 1



27/76


Scram

response


tsunami


Venting


Containment Vessel Venting Operation (1)

Self-containedbreathing apparatus

Two valves, a PCV vent valve (MO valve) and a S/C vent valve (AO valve: small) were selectedas the target for manual PCV venting operation .

Manual valve operation were planned to be conducted by 3 teams with 2 shift workers per team(one worker per team would be difficult due to the total darkness) and shift supervisors and vice-

supervisors were selected to the team members. Equipment for the teams included fire-resistant clothing, self-contained breathing apparatus,

APD, survey meter and flash light.

At 9:03, it was confirmed that evacuation from the vicinity of south side of the NPS completed.At 9:04, the team members headed to the site for the venting operation.

72AO

210

MO

1AO

83

AO

90AO

0.549MPabs

RPV

D/W

RPVRPV

D/W

IA

IA

D/W0.528MPabs

0.954MPabs

213

AO

Shift workers operation tomanually openvalve

MO

AO

AO

AO

AO

MO

Exhauststack

Closed

Closed

Closed

Closed

Solenoidvalve

Cylinder

Cylinder

D/W maximumoperating pressure:

0.528MPaabs

Ruptureddisc Broke at

0.549MPabs

Venting

pressure:0.954MPaabs


Preparations

for venting



28/76



Venting



72AO

210MO

1AO

83

AO

90AO

0.549MPabs

RPV

D/W

RPVRPV

D/W

IA

IA

D/W0.528MPabs

0.954MPabs

213

AO

25%

1st team proceeded to site to operatePCV vent valve (MO valve) on the2nd level of the R/B, and implementedoperation to open the valve manually.

R/B 2nd levelR/B 1st level

South-sidedouble door

To 2nd level bysoutheast stairs PCV vent valve

(MO valve)

North-sidedouble door

Operation to open PCV ventvalve (MO valve) successful

Access route to PCV vent valve (MO valve)

Manualopening

operationsuccessful

MO

MO

AO

AO

AO

AO

Ruptured disc

Broke at 0.549MPabs

Air stack

Closed

Closed

Closed

Solenoid valve

Solenoid valve

Cylinder

Cylinder

D/W maximum operating pressure

Venting pressure

Closed

(25% open)

Operation to manually openPCV vent valve (MO valve)

Scram

response


tsunami


Preparations

for venting



29/76



Venting



72AO

210MO

1AO

83

AO

90AO

0.549MPabs

RPV

D/W

RPVRPV

D/W

IA

IA

D/W0.528MPabs

0.954MPabs

213AO

25%

2nd team entered the torus room (R/B

B1F), but the valve was located at adirection of 180 degrees from where theteam entered the torus room.

The survey meter rose up to the limit onthe way, and the team members returned.

R/B 1st floor R/B B1F

S/C ventvalve

(AO valve)

Dose at thenorth-sidedouble

door washigh, andsouth-boundcourse wasselected

Manual operation was abandoned

and another means were selected

Access route to S/C vent valve (AO valve)

Manual openingoperation

successful

AO

AO

Manual openingoperation abandoned

due to high dose

AO

AOMO

MORuptured disc

Broke at 0.549MPabs

Air stack

Closed

Closed

Closed

Solenoid valve

Solenoid valve

Cylinder

Cylinde

r

D/W maximum operating pressure

Ventingpressure

Closed

(25% open)

Operation to manually open S/Cvent valve (AO valve) valves

South-sidedouble door

North-sidedouble door


tsunami

Scram

response


Preparations

for venting


30/76


What were available for the recovery work after the tsunami?

There were only the following limited number of

devices and tools available!

Fire Engines: only a few people knew howto operate them.

Flashlights

Cable Tools (screwdrivers, etc.)

Batteries taken from cars Engine driven Generators* Engine driven Air Compressors**They were in the warehousesof the affiliated companies anddifficult to find.


31/76


System Status after the Tsunami at 2F

secure (power, pump and motor all working) loss of function (power, pump or motor inoperable)

malfunction (inoperable due to factor other than power, pump or motor)

RHR(A) inoperable due to the

loss of power source

and cooling system

inoperable due to the

loss of cooling system





RHRC/RCRS(A,C)


submerge of powersource and motor







EECW(A) inoperable due to the

submerge of power

source and motor


submerge of power

source and motor


submerge of power

source and motor


submerge of power

source and motor



and cooling system







inoperable due to

submerge







RHR(B) inoperable due to the

loss of cooling system inoperable due to the

loss of cooling system stand-by inoperable due to the


RHRC/RCRS(B,D) inoperable due to the

submerge of power

source and motor


submerge of power

source

stand-by inoperable due to the

submerge of power

source and motor

EECW(B) inoperable due to the

submerge of power

source and motor


submerge of power

source

operation inoperable due to the

submerge of power

source




loss of cooling system stand-by



inoperable due tosubmerge

inoperable due to theloss of cooling system

operation inoperable due to theloss of cooling system









MUWC

(alternative water injection)MUWC() stand-by stand-by stand-by stand-by

stand-by stand-by stand-by stand-by

RHR(C )

EDG(B)

RWCU

RCIC

Unit 4Unit 3Unit 2Unit 1System

RHR(A)

including coolingsystems

RHR(B)

including cooling

systems

LPCS

EDG(A)


32/76


Field Walkdown

Challenges in conducting field walkdown

Under continuous tsunami alerts, walkdown must be done in the field where alot of debris, openings and flooding areas existed in the dark.

Preparation for emergency evacuation in case of further tsunami and other

safety measures for personnel going out to the field. Successful access to the field was 6 hours after the tsunami flooding.

Field walkdown after the tsunami

Plant equipment status checked / componentfunctionality verified.

Results were summarized and shared at TSC.

TSC set priorities on recovery of RHR (B) coolingsystems by replacing motors and supplying powerfrom survived electrical buses and mobile powervehicles through temporary cable.

In order to establish a well-prioritized restoration strategy,degree of damage and possibility of short-term restoration

must be understood through walkdown.

L i ti i E Sit ti


33/76


Logistics in Emergency Situation Procurement and transportation of Materials and Equipment

Emergency procurement of motors, cable, mobile power vehicles, fuel oil andmobile transformers with close cooperation between site TSC and corporate ERC.

Rated output of some motors were not the same as that of the original motors.TSC determined to install them based on the evaluation of actual load conditions.

Difficulties experienced in logistics

Motors were transported from Toshiba by a chopper of SDF and from KashiwazakiKariwa NPP by trucks.

Securing redundant communication measures were critically important when majorhighway was damaged and public cell phone services were disrupted.

Mobile Power Vehicles Fuel oil delivery to the siteNecessary materials andequipment prioritized and listed


34/76


Emergency Restoration Efforts in the Field

Pumps of RHR cooling systems (RHRC, RHRS, EECW) were inspected.

Motors were replaced for pumps in RHRC and EECW.

In order to restore the inundated electrical buses, temporary cable andhigh voltage mobile power vehicles were deployed.

Temporary cable was laid from survived power cubicles in Rad-Waste

Building and Unit 3 Heat Exchanger Building.Drawing made at TSC for temporary cable laying

Motor replacement


35/76


Recovering Electricity

Temporary cable of 9 km length was laid by about 200 personnel within a day.Usually this size of cable laying requires 20 personnel and more than 1 month period.

After the pumps for RHR cooling systems were restored and temporary cable was laidRHR (B) of Unit 1 started up at 1:24 on March 14 and other units followed.

Finally at 15:42 on March 14with the start up of Unit 4 RHR,RHR of all four reactors ofFukushima Daini startedoperation.


36/76


Temporary Power Supply and Motor Replacement at 2FUnit #3

Hx

Building

Unit #1

Reactor

Rad-WasteBuilding

TSC

Main Office

Unit #4Turbine

Unit #2Hx

Building

Unit #1Hx

Building

Unit #4Hx

Building

Unit #2

ReactorUnit #3Reactor

Unit #4

Reactor

Unit #3Turbine

Unit #1Turbine

Unit #2Turbine

MobilePowerSupplyTruck(500kVA)

Temporary Cables

MobilePowerSupplyTruck(500kVA)

6.6kV/480VTransformer

6.6kV/480VTransformer

About 9 km of temporary cableswere laid and motors were

replaced.

System Status after Emergency Restoration at 2F


37/76


System Status after Emergency Restoration at 2F

secure (power, pump and motor all working) loss of function (power, pump or motor inoperable)

malfunction (inoperable due to factor other than power, pump or motor)

RHR(A) inoperable due to


and coolin s stem

inoperable due to

loss of cooling

s stem

inoperable due to

loss of cooling

s stem

inoperable due to

loss of cooling

s stem

RHRC/RCRS(A,C) inoperable due to

submerge of power

source and motor

inoperable due to

submerge of power

source and motor

inoperable due to

submerge of power

source and motor

inoperable due to

submerge of power

source and motor

EECW(A) inoperable due to

submerge of power

source and motor

inoperable due to

submerge of power

source and motor

inoperable due to

submerge of power

source and motor

inoperable due to

submerge of power

source and motor

inoperable due to


and cooling system

inoperable due to

loss of cooling

system

inoperable due to

loss of cooling

system

inoperable due to

loss of cooling

system

inoperable due to

submerge

inoperable due to

loss of cooling

system

inoperable due to

loss of cooling

system

inoperable due to

loss of cooling

system

RHR(B) operation operation operation operation

RHRC/RCRS(B,D) operation operation operation operation

EECW(B) operation operation operation operation

stand-by stand-by stand-by stand-by

operable using t ie-line

from unit #2 stand-by stand-by stand-by


loss of purge line


loss of purge line


loss of purge line


loss of purge line

MUWC

(alternative water injection)MUWC(B) stand-by stand-by stand-by operation

inoperable for loss of

core pressure


core pressure


core pressure


core pressureRCIC

RWCU

EDG(B)

RHR(C )

Unit 2 Unit 3 Unit 4System

RHR(A)

including coolingsystems

RHR(B)

including cooling

systems

Unit 1

LPCS

EDG(A)

O i f th 10 U it Si lt A id t


38/76


Overview of the 10-Unit Simultaneous Accidents

Date1F 2F

1 2 3 4 5 6 1 2 3 4

3/11

3/12

3/13

3/14

3/15

3/16-19

3/20

3/14 17:00

3/14 1:24RHR

3/14 7:13RHR

3/14 15:42RHR

3/14 18:00

3/15 7:15

3/12 12:15

3/20 14:30

3/19 22:14RHR

3/12 8:13D/G-6B

3/22 10:35P/C-4D

3/22 10:36P/C-4D

3/20 15:46P/C-2C

3/20 15:46P/C-2C

3/19 5:00RHR

3/20 14:30

Station Black-Out

Loss of Ultimate Heat Sink

Cold Shutdown

3/12 15:36 Unit 1 Explosion

3/15 6:00-6:10 Unit 4 Explosion (?)

3/14 11:01 Unit 3 Explosion

3/11 15:27 1st Tsunami, 15:35 2nd Tsunami 3/11 15:22~ Tsunamis


39/76


Testimonies from the Field (Operators)

In an attempt to check the status of Unit 4 D/G, I wastrapped inside the security gate compartment. Soon the

tsunami came and I was a few minutes before drowning,when my colleague smash opened the window and savedmy life.

In total darkness, I could hear the unearthly sound of SRV

dumping steam into the torus. I stepped on the torus to

open the S/C spray valve, and my rubber boot melted. The radiation level in the main control room was

increasing 0.01 mSv (1 mrem) every 3 seconds but Icouldnt leaveI felt this was the end of my life.

I asked for volunteers to manually open the vent valves.

Young operators raised their hands as well; I wasoverwhelmed.

Unit 3 could explode anytime soon, but it was my turn togo to the main control room. I called my dad and askedhim to take good care of my wife and kids should I die.

Testimonies from the Field (Maintenance Persons)


40/76


Testimonies from the Field (Maintenance Persons)

We saw our car crashed by the explosion of the Unit 3. Ifwe had gotten on the car a few minutes earlier, all of uswould have been dead.

We were replacing fire hoseswhen the explosion of Unit 3occurred. We felt almost dying since many large rubbleswere falling down to us.I urgently ran underneath a nearbyfire engine. One of my colleagues got injuries in his leg andstomach.

There were so many manholes opened by the tsunami. Inorder to lay cables, we had to proceed step by stepcarefully checking safety in the complete darkness.

We were working in the Unit 3/4 control room when theexplosion occurred. I was resigned to my fate. Dose ratewas going up in the room after the explosion and wedesperately tried to find places with lower dose rate.

After replacing an air cylinder for the PCV ventilation of

Unit 3, I heard sound of steam and saw white mist aroundus. I got into a panic for a while.


41/76


4. Summary


42/76


The 1F accident was caused by the simultaneous loss of multiple safetyfunctions due to far beyond design basis of tsunami. The main factors of the

accident are the simultaneous loss of total AC power and DC power fora extended period of timeand the loss of the heat removal function ofthe emergency seawater system for a extended period of time.

Preparations had been previously made to receive power from neighboringunits in the event that AC power and DC power were not available. During the

accident, direct tsunami damage was so widespread that the neighboringunits were all in the same condition.

Summary of Lessons Learned

Carefully consider the robustness of current design ofnuclear power plants and emergency preparedness

againstbeyond design basis eventsthat could lead tocommon cause failuresregardless of their assumedprobability demonstrating a continuous learningorganization.

Technical Lessons Learned


43/76


Success path regarding Cooling and Heat Removal from the Reactor

1)Promptly initiate core injectionmethods using high-pressure coolingwater injection equipment

2)Initiate depressurization methods before losingof high-pressure cooling water injection function

3)Stable low-pressure cooling water injection methodsshould be available during the depressurization stage

4)Provide reliable PCV venting methods (heat removal

through the atmospheric discharge of heat)

5)Provide measures to restore the

cooling function using sea water

6)Provide measures which enable necessary monitoring for those operationand plant conditions.

It is inevitable to maintain water injection and core cooling function thoroughlyand continuously even in poor environmental conditions.

Technical Lessons Learned


44/76


2F Key Success Factors

Accident mitigation by applying EOP and AMG

Prioritized restoration strategy based on Field Walkdown

Prompt restoration with success of emergencyprocurement for materials and equipment

Logistics for long term emergency response

Organizational integrity: Leadership, Communication,Accountability, Professionalism

Organization and Management Features

Design/Engineering Features

Availability of most of M/C, P/C and Battery

Availability of off-site power

Website Information


45/76


Website Information

TEPCO English websitehttp://www.tepco.co.jp/en/nu/fukushima-np/index-e.html

Internal Investigation Committee Interim Report (Dec. 2nd, 2011)http://www.tepco.co.jp/en/press/corp-com/release/11120205-e.html

Report on initial responses to the accident (Dec. 22nd,2011)

The Latest version of accident Timeline (Dec.22nd, 2011)English version will be on the following website soon.

http://www.tepco.co.jp/en/press/corp-com/release/11122208-e.html

INPOSpecial Report on Fukushima Daiichi Nuclear Power Stationhttp://www.nei.org/resourcesandstats/documentlibrary/safetyandsecurity/reports/special-report-

on-the-nuclear-accident-at-the-fukushima-daiichi-nuclear-power-station

EPRIFukushima Daini Independent Review and Walkdown

http://my.epri.com/portal/server.pt?Abstract_id=000000000001023422
http://www.tepco.co.jp/en/nu/fukushima-np/index-e.htmlhttp://www.tepco.co.jp/en/press/corp-com/release/11120205-e.htmlhttp://www.tepco.co.jp/en/press/corp-com/release/11122208-e.htmlhttp://www.nei.org/resourcesandstats/documentlibrary/safetyandsecurity/reports/special-report-on-the-nuclear-accident-at-the-fukushima-daiichi-nuclear-power-stationhttp://www.nei.org/resourcesandstats/documentlibrary/safetyandsecurity/reports/special-report-on-the-nuclear-accident-at-the-fukushima-daiichi-nuclear-power-stationhttp://my.epri.com/portal/server.pt?Abstract_id=000000000001023422http://my.epri.com/portal/server.pt?Abstract_id=000000000001023422http://my.epri.com/portal/server.pt?Abstract_id=000000000001023422http://www.nei.org/resourcesandstats/documentlibrary/safetyandsecurity/reports/special-report-on-the-nuclear-accident-at-the-fukushima-daiichi-nuclear-power-stationhttp://www.nei.org/resourcesandstats/documentlibrary/safetyandsecurity/reports/special-report-on-the-nuclear-accident-at-the-fukushima-daiichi-nuclear-power-stationhttp://www.nei.org/resourcesandstats/documentlibrary/safetyandsecurity/reports/special-report-on-the-nuclear-accident-at-the-fukushima-daiichi-nuclear-power-stationhttp://www.nei.org/resourcesandstats/documentlibrary/safetyandsecurity/reports/special-report-on-the-nuclear-accident-at-the-fukushima-daiichi-nuclear-power-stationhttp://www.nei.org/resourcesandstats/documentlibrary/safetyandsecurity/reports/special-report-on-the-nuclear-accident-at-the-fukushima-daiichi-nuclear-power-stationhttp://www.nei.org/resourcesandstats/documentlibrary/safetyandsecurity/reports/special-report-on-the-nuclear-accident-at-the-fukushima-daiichi-nuclear-power-stationhttp://www.nei.org/resourcesandstats/documentlibrary/safetyandsecurity/reports/special-report-on-the-nuclear-accident-at-the-fukushima-daiichi-nuclear-power-stationhttp://www.nei.org/resourcesandstats/documentlibrary/safetyandsecurity/reports/special-report-on-the-nuclear-accident-at-the-fukushima-daiichi-nuclear-power-stationhttp://www.nei.org/resourcesandstats/documentlibrary/safetyandsecurity/reports/special-report-on-the-nuclear-accident-at-the-fukushima-daiichi-nuclear-power-stationhttp://www.nei.org/resourcesandstats/documentlibrary/safetyandsecurity/reports/special-report-on-the-nuclear-accident-at-the-fukushima-daiichi-nuclear-power-stationhttp://www.nei.org/resourcesandstats/documentlibrary/safetyandsecurity/reports/special-report-on-the-nuclear-accident-at-the-fukushima-daiichi-nuclear-power-stationhttp://www.nei.org/resourcesandstats/documentlibrary/safetyandsecurity/reports/special-report-on-the-nuclear-accident-at-the-fukushima-daiichi-nuclear-power-stationhttp://www.nei.org/resourcesandstats/documentlibrary/safetyandsecurity/reports/special-report-on-the-nuclear-accident-at-the-fukushima-daiichi-nuclear-power-stationhttp://www.nei.org/resourcesandstats/documentlibrary/safetyandsecurity/reports/special-report-on-the-nuclear-accident-at-the-fukushima-daiichi-nuclear-power-stationhttp://www.nei.org/resourcesandstats/documentlibrary/safetyandsecurity/reports/special-report-on-the-nuclear-accident-at-the-fukushima-daiichi-nuclear-power-stationhttp://www.nei.org/resourcesandstats/documentlibrary/safetyandsecurity/reports/special-report-on-the-nuclear-accident-at-the-fukushima-daiichi-nuclear-power-stationhttp://www.nei.org/resourcesandstats/documentlibrary/safetyandsecurity/reports/special-report-on-the-nuclear-accident-at-the-fukushima-daiichi-nuclear-power-stationhttp://www.nei.org/resourcesandstats/documentlibrary/safetyandsecurity/reports/special-report-on-the-nuclear-accident-at-the-fukushima-daiichi-nuclear-power-stationhttp://www.nei.org/resourcesandstats/documentlibrary/safetyandsecurity/reports/special-report-on-the-nuclear-accident-at-the-fukushima-daiichi-nuclear-power-stationhttp://www.nei.org/resourcesandstats/documentlibrary/safetyandsecurity/reports/special-report-on-the-nuclear-accident-at-the-fukushima-daiichi-nuclear-power-stationhttp://www.nei.org/resourcesandstats/documentlibrary/safetyandsecurity/reports/special-report-on-the-nuclear-accident-at-the-fukushima-daiichi-nuclear-power-stationhttp://www.nei.org/resourcesandstats/documentlibrary/safetyandsecurity/reports/special-report-on-the-nuclear-accident-at-the-fukushima-daiichi-nuclear-power-stationhttp://www.nei.org/resourcesandstats/documentlibrary/safetyandsecurity/reports/special-report-on-the-nuclear-accident-at-the-fukushima-daiichi-nuclear-power-stationhttp://www.nei.org/resourcesandstats/documentlibrary/safetyandsecurity/reports/special-report-on-the-nuclear-accident-at-the-fukushima-daiichi-nuclear-power-stationhttp://www.nei.org/resourcesandstats/documentlibrary/safetyandsecurity/reports/special-report-on-the-nuclear-accident-at-the-fukushima-daiichi-nuclear-power-stationhttp://www.tepco.co.jp/en/press/corp-com/release/11122208-e.htmlhttp://www.tepco.co.jp/en/press/corp-com/release/11122208-e.htmlhttp://www.tepco.co.jp/en/press/corp-com/release/11122208-e.htmlhttp://www.tepco.co.jp/en/press/corp-com/release/11122208-e.htmlhttp://www.tepco.co.jp/en/press/corp-com/release/11122208-e.htmlhttp://www.tepco.co.jp/en/press/corp-com/release/11122208-e.htmlhttp://www.tepco.co.jp/en/press/corp-com/release/11120205-e.htmlhttp://www.tepco.co.jp/en/press/corp-com/release/11120205-e.htmlhttp://www.tepco.co.jp/en/press/corp-com/release/11120205-e.htmlhttp://www.tepco.co.jp/en/press/corp-com/release/11120205-e.htmlhttp://www.tepco.co.jp/en/press/corp-com/release/11120205-e.htmlhttp://www.tepco.co.jp/en/press/corp-com/release/11120205-e.htmlhttp://www.tepco.co.jp/en/nu/fukushima-np/index-e.htmlhttp://www.tepco.co.jp/en/nu/fukushima-np/index-e.htmlhttp://www.tepco.co.jp/en/nu/fukushima-np/index-e.htmlhttp://www.tepco.co.jp/en/nu/fukushima-np/index-e.htmlhttp://www.tepco.co.jp/en/nu/fukushima-np/index-e.html


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Thank you for your attention!


47/76


5. References

Intensit of the earthq ake at the po er stations


48/76

All Rights Reserved 2011The Tokyo Electric Power Company, Inc. 47 47

Intensity of the earthquake at the power stations

*: The records were stopped approximately 130-150 seconds after recording started.

Observation Point

(The lowest basement of

reactor buildings)

Observed DataMaximum Response Accelerationagainst Basic Earthquake Ground

Motion (Gal)Maximum Response

Acceleration (gal)

Horizontal

(N-S)

Horizontal

(E-W)Vertical

Horizontal

(N-S)

Horizontal

(E-W)Vertical

Fukushima

Daiichi

Unit 1 460* 447* 258* 487 489 412

Unit 2 348* 550* 302* 441 438 420

Unit 3 322* 507* 231* 449 441 429

Unit 4 281* 319* 200* 447 445 422

Unit 5 311* 548* 256* 452 452 427

Unit 6 298* 444* 244 445 448 415

Fukushima

Daini

Unit 1 254 230* 305 434 434 512

Unit 2 243 196* 232* 428 429 504

Unit 3 277* 216* 208* 428 430 504

Unit 4 210* 205* 288* 415 415 504

In Fukushima Daiichi the observed data partially exceeded the maximum response acceleration with respect to the

design-basis earthquake, however most data was below the baseline

Note) Standard ground motion Ss: Seismic motion that was newly established to evaluate seismic safety, taking into account the

earthquakes, etc., that could occur around the power station, based on the revised seismic design review guidelines.



49/76


In Fukushima daiich observation record partially exceeded the design-basis earthquake

ground motion, however it was confirmed to be almost the same level

0.02 0.05 0.1 0.2 0.5 1 2 50

1000

2000

3000

()

(Gal)

(h=0.05)

0.02 0.05 0.1 0.2 0.5 1 2 50

1000

2000

3000

()

(Gal)

(h=0.05)

Fukushima daiich

periodsperiods

0 50 100 150-800

-400

0

400

800

(Gal)

550

0 50 100 150

-800

-400

0

400

800

(Gal)

277

Fukushima daini

Observation recordsDesign-basis seismic ground motion Ss-1HDesign-basis seismic ground motion Ss-2HDesign-basis seismic ground motion Ss-3H

Observation recordsDesign-basis seismic ground motion Ss-1HDesign-basis seismic ground motion Ss-2HDesign-basis seismic ground motion Ss-3H

Unit 2W-E Unit 3N-S

timestimes

Acceleration

Gal

Acceleration

Gal

550 277

Accele

ration

Gal

Acceleration

Gal


Inundated Areas at 1F


50/76


C)GeoEye


Inundation throughout almost all areas where main buildings sitedUnits 1~4: Inundation height in areas where principal buildings sited:OP approx. 11.5m~15.5m

(Localized inundation height in southwest area: OP approx. 16m~17m)

Unit 5 & 6: Inundation height in areas where principal buildings sited: OP approx.13m~14.5m

Almost whole area was floodedFukushima

Daiichi

Unit1

Unit2

Unit3

Unit4

Unit6

Unit5

RadwasteProcessing

building

Elevation of majorUnit-1-4 buildings:

O.P.10m

Elevation of majorUnit-5,6 buildings:

O.P.13m

Location of Openings from which Sea Water


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O . P .+ 1 3 m

O . P .+ 1 0 m

O .P .+ 4 mO .P .+ 4 m

3u Emergency D/Gair inlet louver

p gcould Flow into Main Buildings

(Fukushima Daiichi Nuclear Power Station)

Turbinebuilding

Reactorbuilding

Unit 6 D/G building

Unit 5Unit 6

Unit 1 Unit 2 Unit 3 Unit 4

Openings at the ground level fromwhich sea water could flow into buildingsOpenings connected to undergroundtrenches/ducts where sea water could flowinto buildings



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Inundation occurred throughout all areas along the sea, but it was not observed tohave inundated over the slope and into areas where major buildings are sited.

Run up of tsunami centered on the south side of Unit 1Inundation height in sea side area: OP approx. +7.0~7.5m

Inundation height in areas where principal buildings sited: OP approx. 12~14.5mInundation height in area south of Unit 1: OP approx. + 15~16m

Limited area was flooded

Inflowedintensively

C)GeoEye

Unit 2 Unit 1Unit 3Unit 4

Elevation of majorUnit-1-4 buildings:

O.P.12m

Location of Openings from which Sea Waterld fl i t M i B ildi


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could flow into Main Buildings(Fukushima Daini Nuclear Power Station)

Inside Unit 1 heat exchanger buildingUnits 3 & 4

Sea side of turbinebuilding

Openings at the ground level from which sea water could flow into buildingsOpenings connected to underground trenches/ducts where sea water could flow into buildings

Heat exchangerbuilding

Turbinebuilding

Reactorbuilding

Unit1

Unit2

Unit3

Unit4

Tsunami Height @1F v s 2F


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Base levelO.P.0m

Reactor

building

Ocean-sidearea Main building area

breakwater

Design basistsunami heightO.P.+5.2m

Site levelO.P. +12m

Water

intake

Inundation height apx. O.P. +6.5 - 7mSafety measures has taken

against 5.2m Tsunami height

Site levelO.P. +4m

Turbine building

Tsunami Height @1F v.s. 2F

49

The new design basis Tsunami height for 1F & 2F were evaluated based on the JSCE Tsunami assessmentmethodology. (1F: O.P.+5.7m, 2 F: O.P.+5.2m)

The countermeasures were implemented at both NPSs, such as pump motor elevation raised @1F andopenings sealed @2F, that were all equivalent from the viewpoint of resistance against Tsunami hazard.

The 15m class Tsunami caused by M9.0 class earthquake that accidentally attacked 1F was far beyond design

basis and whatever evaluation and whatever countermeasures did not matter at this time.1F

2F

O.P.Onahama Point

Hx building

Assumed highesttsunami water level

O.P. +5.7m

Base levelO.P. 0m

-

-

-

-Assumed highest

tsunami water level

O.P. +5.7m

Base levelO.P. 0m

Site levelO.P. +10m(Units 1-4*)

* Site level on Units 5 and 6 is O.P. +13m

Turbine building

Reactor buildingInundation heightapx. O.P. +14-15m

Ocean-sidearea

Main building area

Water intake

Site levelO.P. +4m

Safety measures hastaken against 5.7m

Tsunami height

breakwater

WaterPump

Assumed highesttsunami water level

O.P. +5.7m

Base levelO.P. 0m

Site levelO.P. +10m(Units 1-4*)

* Site level on Units 5 and 6 is O.P. +13m

Turbine building

Reactor buildingInundation heightapx. O.P. +14-15m

Ocean-sidearea

Main building area

Water intake

Site levelO.P. +4m

Safety measures hastaken against 5.7m

Tsunami height

breakwater

WaterPump

Design basistsunami heightO.P.+5.7m

Differences in Tsunami that hit Fukushima Daiichi


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and Daini NPSs

1050

100150

0

2

4

6

8

10

12

14

[m]Sea floor

displacement[m]

Fukushima

Daiichi

Fu

kushima

Da

ini

Maximumtsunamiheight

m

Peaks coinciding

Tsunami height: High

Peaks not coinciding

Tsunami height: Low

Same amplification rate

Water levelfluctuation fromeach blockTime T

Warm colored blocksgenerated massivetsunami wave heights

Tsunami of various magnitudes at a depth ofaround 150m were amplified at the same rate

and struck at each nuclear power station

Water depth [m]

Postulated Tsunami Model

Permitted Design Basis(1) Tsunami assessment


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g ( )

Tsunami assessment in construction permit

Fukushima NPSs

Historical tsunamis of Iwate and Miyagi coast were larger than that of FukushimaApproved design basis at Fukushima NPS was 3.1-3.7m

Fukushima NPSs

3.11.2011 tsunami heights (m)Historical tsunami heights (m)

Preliminary results by The 2011 Tohoku Earthquake Tsunami Joint SurveyGroup( http://www.coastal.jp/ttjt/) 07 May 2011

Inundation

Run-up

Unit Ground Level Tsunami Heightm

R/B,Tb/B

m

Pumps

m

Design Basis Modified in

2002 (2009)

11 march

2011

1F 1-4 10.2 4 3.1 5.7 (6.1) 14-15

1F 5-6 13.2 4 3.1

2F1-4 12 7 3.7 5.2 7-7.5



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Earthquake Magnitude Earthquake

#1 8.2 1952 Nemuro-oki

#2 8.4 1968 Tokachi-oki

#3 8.3 1896 Meiji-Sanriku

#4 8.6 1611 Keicho-Sanriku

#5 8.2 1793 Miyagi-oki

#6 7.7 1978 Miyagi-oki

#7 7.9 1938 Fukushima-oki

#8 8.1 1677 Enpo-Bousou

htt ://outreach.eri.u-tok o.ac. /e volc/201103 tohoku/#Inversion 2011/3/182011/3/11 source area

English editionhttp://www.jsce.or.jp/committee/ceofnp/Tsunami/eng/tsunami_eng.html

In JSCE- 2002, assumed 8 earthquakes individually. March

11 Earthquake occurred over several areas simultaneously.

Tsunami Assessment was revised based on the JSCE (Japan

Society of Civil Engineers) Method,2002

Damage Status of Unit 1 & 2 Emergency DG and Emergency High


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Unit 1 Unit 2

Equipment

Installedbuilding

Installed floor

Possibility

ofuse

StatusEquipme

ntInstalledlocation

Installedfloor

Possibility ofuse

Status

DG

DG 1A T/B B1FL Submerged DG 2A T/B B1FL Submerged

DG 1B T/B B1FL Submerged DG 2BShared

pool1FL

M/Csubmergedcannot be

used

(M/C)

Emergencyhigh

voltageswitchb

oard

M/C 1C T/B 1FL Water

damageM/C 2C T/B B1FL Submerged

M/C 1D T/B 1FL Water

damageM/C 2D T/B B1FL Submerged

M/C 2E Sharedpool

B1FL Submerged

Voltage Switchboard (Immediately after the Tsunami)



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Unit 3 Unit 4

Equipment

Installedlocation

Installed floor

Possibility

ofuse

StatusEquipme

ntInstalledlocation

Installed

floor

Possibility ofuse

Status

DG

DG 3A T/B B1FL Submerge

d DG 4A T/B B1FL Submerged

(Constructionin progress)

DG 3B T/B B1FL Submerge

d DG 4BShared

pool1FL

M/Csubmergedcannot be

used

(M/C)

Emergencyhigh

voltageswitchboard

M/C 3C T/B B1FL Submerge

d M/C 4C T/B B1FL Submerged(Inspection

in progress)

M/C 3D T/B B1FL Submerge

d M/C 4D T/B B1FL Submerged

M/C 4E Sharedpool

B1FL Submerged




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Unit 5 Unit 6

Equipment

Installedlocation

Installed

floor

Po

ssibility ofuse

Status EquipmentInstalledlocation

Installed

floor

Possibility ofuse

Status

DG 5A T/B B1FL

Relatedequipment

Waterdamage

DG 6A R/B B1FL

Relatedequipment

Waterdamage

DG 5B T/B B1FL

Relatedequipment

Waterdamage

DG 6BDGbuilding

1FL

HPCSD/G R/B B1FL Related

equipmentWater

damage

(M/C)Emerge

ncyhigh

voltageswitchb

oard

M/C 5C T/B B1FL Submerged M/C 6C R/B B2FL

M/C 5D T/B B1FL Submerged M/C 6D R/B B1FL

HPCSDG M/C

R/B 1FL


Fukushima Daiichi: DG System Outline


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All functionwas lost after

the tsunami

Power was

secured inUnit 6 (B)only

[Fukushima Daini: DG System Outline]

Power wassecured inUnit 3(B)(H) andUnit 4 ()only

Sea water-cooled DG (10)

Unit 1 (A)(B), Unit 2 (A), Unit 3 (A)(B), Unit 4 (A), Unit 5 (A)(B), Unit 6 (A)(H)

Air-cooled DG (3)

Unit 2 (B), Unit 4 (B), Unit 6(B)

Sea water-cooled DG (12)Unit 1 to Unit 4(A)(B)(H)

Sea waterpump

D/GHeatexchanger

Sea

Outsideair

Air cooler D/G

Cooling water pump

Heatexchanger

Sea waterpump

Heatexchanger

Cooling waterpump

D/GSea

Power Access/Restoration Status Immediately


62/76


yafter 1F-1,2 Shutdown

Date Operation and Restoration Status

March 11 Temporary MCR lighting on (Temporary small engine generator)

March 12

Power source for Unit 1 Instrument restored (Temporary smallengine generator)

Power source for Unit 1 Instrument restored (power source cart)

Temporary small engine generator destroyed by H2 explosion

Temporary MCR lighting on (another temporary small enginegenerator)

March 19 Backup transformer ~ Unit 1 & 2 temporary M/C (A) cable laidMarch 20 Off-site power restored (P/C2C power received)



63/76


after 1F-3,4 Shutdown


March 11 Temporary MCR lighting on (Temporary small engine generator)

March 13 P/C 4D restored (power source cart)

March 14

Yonomori Line 1L step-down transformer cart (66/6.9kW)connected to the Shin-Fukushima Substation

Yonomori Line 1L ~ Okuma Line 3L connected

Power source for Unit 1 Instrument restored (power source cart)The power source cart destroyed by H2 explosion

March 18 Unit 3 & 4 MC, Switch installation location

March 22 Off-site power restored (P/C4D power received)



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after 1F-6 Shutdown


March 11

DG6B startup (6A and 6H were shut down by the tsunami,6B is an air-cooled type

SGTS(B) startup, DC125V/250V (B system) restoration

March 12 DC125V/250V (A system) restoration

March 13 MUWC(B) startup

March 19

RHR 6B startup, temporary RHRS alternative pump startup(power source cart)

DG6A startup (March 21 shutdown)

March 20 Cold shutdown condition

March 22 Off-site power restored (M/C6C, 6D power received)

March 23Temporary RHRS alternative pump switched to off-sitepower



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March 12 DC125V/250 restoration

March 13 MUWC(A), SGTS(A) startup

March 18 Temporary RHRS alternative pump startup (power source cart)

March 19 RHR 5C startup

March 20 Cold shutdown condition

March 22 Off-site power restored (M/C6C, 6D power received)

March 23 Temporary RHRS alternative pump switched to off-site power

after 1F-5 Shutdown

Recovery Process of I&C equipments @1F (1/2)


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After tsunami Total loss of instrumentations due to loss

of offsite power and DC 125V

March 11-14: to install temporary batteries to importantinstrumentations, such as reactor water level, reactorpressure, D/W pressure, S/C pressure etc. (1F-1-3: March 11,

1F-5/6: March 14) and to start to obtain plant data

March 22-25: to recover AC 120V bus for I&C (1F1: March23, 1F2: March 25, 1F3/4: March 22)

Present: to prioritize the recovery of redundantinstrumentations for their reliability and to change step by stepfrom temporary battery to original power source



67/76


y q p @ ( )

May 9: to go into R/B to calibrate the D/W pressureinstrument @1F1

May 10-12: to calibrate the fuel zone reactor water levelinstrument @1F1

- water level assumed as lower than -500cm of TAF

June 3-4: to install the temporary reactor pressure andpressure instrument at the test line of fuel zone reactorwater level instrument @1F1, to obtain more precise data onreactor pressure and water level

June 22-24: to install the temporary reactor pressure andpressure instrument at the test line of fuel zone reactor

water level instrument @1F2

- not successful due to rapid evaporation of water inside instrumentation line byhigh PCV temperature

Current status of important instrumentations @1F


68/76


p

Parameter/unit

1F1 1F2 1F3 1F4 1F5 1F6

Reactorwater level

N/A

Reactorpressure

N/A

Reactorwater temp.

Not sampled Not sampled Not sampled N/A

Temperature around

RPV N/A N/A N/A

D/Wpressure

N/A N/A N/A

S/Cpressure

N/A N/A N/A

CAMS radmonitor

D/WS/C

D/WS/C

D/WS/C

N/A N/A N/A

S/Ctemparature

- - -calibrated,assumed to be intact, under continuous observation, failure

Unit 1 Isolation Condenser


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Unit 1 Isolation Condenser

RPV

Primary Containment

Open to the Air

Fire protection systemPure water make up system

MO

system systemIsolationCondensor

1B

10A10B

3A

3B

PLR PP

MO

MO

MO

MO

MO

MO

MOMO

MO

1A

2BA

4A

4BInitiating system by

opening the valve

Reactor steamiscooled byIsolationcondenser coolanttank

Condensate water returnback to RPV driven bynatural convection force

Heated water in the tankreleased to the open air

MSIV

Function of the Isolation condenser

Depressurization of the reactor by steam condensation during reactor Isolation(MSIV closure condition)

Redundancy design(2 systems)

1F Unit 1 Schematic System Diagram (After Tsunami )


70/76


Sea

TbCondenser

H/W

Gen

CST

FiltratedWaterTank

SLC

Stack

Sea

CCS

D/GCCSW

SRV

CRD

HPCI

CPRFP

W

CS MUWCDD FP

IC

S/C vent valve

D/W vent valveRPV

from

CSTH/W

Sea

:Operable:Inoperative dueto power loss

: BrieflyOperative

Summary of the Plant Behavior in Unit 1 (1/2)


71/76


The automatic isolation interlock of the IC was actuated due to the loss of powercaused by the tsunami and then lost its function. Afterwards, the reactor waterlevel decreased in a short period of time and the core was exposed (Dropped toTAF), leading to the core damage. During this time, it was difficult to understandplant status due to the loss of power.

Based on the analysis results, it is evaluated that the core would have beendamaged regardless of the continuation of the operation of the IC after 18:18.

When the water level gauge was temporarily restored using a temporary powersource after 21:00 on March 11, a reading was obtained showing that the reactorwater level was above TAF. However at this point, there was not enoughinformation to comprehensively determine that this reading was erroneous. At theEmergency Response Headquarters on the site and the Head Office, it was not

deemed at this point that the IC had stopped. The possibility of the core damagewas recognized due to the increase in dose rate in front of the double doors of thereactor building at around 23:00 on March 11 and the unusually high reading forthe dry well pressure that was obtained for the first time at around 0:00 on March12.




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On March 12 at around 3:00, the reactor pressure decreased, although reactordepressurization operation was not conducted. This implies that damage to thereactor cooling water pressure boundary had occurred due to core damage. Thisimplies that core damage might have progressed to a considerable extent in ashort period of time.

Based on the results using the accident analysis codes, it took about 3 hours to

drop to TAF after the earthquake and about 4 hours until core damage began,which indicates the rapid event progress to the core damage. This result isconsistent with the events actually observed.


1F Unit 2 Schematic System Diagram (After Tsunami)


73/76


y g ( )

Sea

TbCondenser

H/W

Gen

CST

FiltratedWaterTank

SLC

Stack

Sea

RHR

D/GRHRS

SRV

CRD

HPCI

LPCPMD-RFP

W

CS

MUWC DD FP

S/C vent valve

D/W vent valve

:Operable:Inoperative dueto power loss

RPV

TD-RFP

fromCSTH/W

CSTRCIC

HPCP

Sea

:Inoperative

Summary of the Plant Behavior in Unit 2


74/76


As the RCIC of Unit 2 functioned for a relatively long period of time, the core

decay heat was lower than immediately after shutdown. However as the high-pressure systems (RCIC) lost its function, decrease in the reactor water levelstarted.

About 1 hour and 20 minutes later after the RCIC shutdown, the fire enginespump was started up and preparations for low-pressure water injection wereready. However the SRV did not immediately operate during reactor

depressurization.

It is considered that core damage occurred because low-pressure water injectiondid not function immediately after the SRV was activated and reactordepressurization was achieved. Because of the rapid decrease in the retainedwater due to the outflow of steam to the S/C associated with reactor

depressurization, cooling function degraded furthermore.

According to the analysis by using the MAAP code, it is evaluated that coredamage started due to the decrease in reactor water level followed bydegradation of the function of the RCIC.


1F Unit 3 Schematic System Diagram (After Tsunami)


75/76


Sea

TbCondenser

H/W

Gen

CST

FiltratedWaterTank

SLC

Stack

Sea

RHRD/GRHRS

SRV

CRD

HPCI

LPCPMD-RFP

W

CS

MUWC DD FP

S/C vent valve

D/W ventvalve

RPV

TD-RFP

fromCSTH/W

CSTRCIC

HPCP

Sea

:Operable:Inoperative dueto power loss:Inoperative



76/76

In Unit 3, preparations for low-pressure water injection were performed by

activating the diesel-driven fire pump. However, because the reactor pressurewas higher than the water injection pressure, switching to low-pressure waterinjection was not immediately successful after shutdown of the high-pressuresystems (HPCI). This caused degradation of cooling and thus leading to coredamage.

S/C venting was conducted and repeated several times. The monitoring carreading near the main gate increased temporarily. However no large increase inthe background level was observed.

In addition, the hydrogen that was generated following the core damage was notcompletely retained in the PCV and leaked into the reactor building, and is

considered to have caused the explosion of the reactor building.


the facts in the recovery process of fukushima nuclear accident (kawano)

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