The Facts in the Recovery Process of Fukushima Nuclear ...gnssn.iaea.org/actionplan/Shared Documents/Action... · Overview of Fukushima Daiichi NPS (1F) and Fukushima Daini NPS (2F)

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The Facts in the Recovery Process of

Fukushima Nuclear Accident

March 21, 2012

@IAEA IEM, Vienna

Akira Kawano

Tokyo Electric Power Company


What I will present

1.How the Earthquake and the Tsunami affected

the Power Supply at 1F and 2F sites ?

2.How the Accident Developed and was Stabilized

at 1F and 2F Sites ?

3.How We Responded to the Accident at 1F and

2F Sites ?

4.Summary

5.Reference


１．How the Earthquake and the Tsunami Affected

the Power Supply at 1F and 2F Sites ?

Unit 6 Unit 5 Unit 1

Unit 2 Unit 3

Unit 4 Unit 1

Unit 2 Unit 3

Unit 4

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


Overview of Fukushima Daiichi NPS (1F)

and Fukushima Daini NPS (2F)

Plant Unit

In

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 Hitachi

Shutdown for maintenance

Full 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




4A 4B

4D 4C

4E

D／G

4B

D／G

4A

D／G

3B

D／G

3A D／G

2B

D／G

2A

D／G

1B

D／G

1A

3A 3B

3C 3D

3SA 3SB

2A 2B

2C 2D

2E

2SA 2SB

1A 1B

1C 1D

1S

Shutdown by earthquake

Shutdown by Tsunami

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

The DG lost 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

Ohkuma

4L

Ohkuma

3L

Ohkuma

2L

Ohkuma

1L


双葉線１Ｌ

双葉線２Ｌ

5A

5C

5B

5D

D／G

5A

D／G

5B

D／G

HPCS

D／G

6A

D／G

6B

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

HPCS 6C

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 2L Yonomori 1L

For transmitting

power

For transmitting

power


Damages of transmission line

& Shinfukushima substation by earthquake

500kV Disconnector 275kV 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 （C）GeoEye

Collapse of filled soil & sand

Tower collapse


6.9kV 6.9kV

2F Offsite Power was secured after the Tsunami Offsite Power

500kV 66kV

H STr

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

Ｄ/Ｇ

Emergency

Power for Unit #1

Ｄ/Ｇ

1H 1A 1B

6.9kV

Ｄ/ＧＤ/Ｇ

2H 2A 2B

Ｄ/Ｇ

3H 3A 3B

6.9kV

Ｄ/ＧＤ/Ｇ

4H 4A 4B

One 500 kV line was available.

66 kV lines were outage because of scheduled

maintenance and substation trouble but recovered.

Many power centers and motors were damaged

because of the flooding.

P P P P

Emergency

Power for Unit #2 Emergency

Power for Unit #3 Emergency

Power for Unit #4

Ｄ/Ｇ

P : Cooling Pumps

Ｄ/Ｇ : Diesel Generator

Ｄ/Ｇ

P Ｄ/Ｇ

P Ｄ/Ｇ

P Ｄ/Ｇ

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/cannot beused










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 4B（air-cooled）

×(*1) DG 5B(*2) ×DG 6B

（air-cooled）○ DG １Ｂ × DG 2Ｂ ×(*2) DG 3Ｂ ○ DG 4Ｂ ×(*2)

－－－－－－－－－－ HPCS DG ×(*2) DG 1Ｈ × DG 2Ｈ ×(*2) DG 3Ｈ ○ DG 4Ｈ ○

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

M/C 6B-2 × M/C 1Ｂ-2 ○ M/C 2Ｂ-2 ○ M/C 3Ｂ-2 ○ M/C 4Ｂ-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 A




○

DC125V mainbus panel B

×DC125V P/C

2B×

DC125V mainbus panel 3B

○DC125V mainbus panel 4B

×DC125V P/C

5B○

DC125V DISTCENTER 6B

○DC125V mainbus panel B




○

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 ×

- -

Regu

lar use

P/C

P/C 1A ×

－

Sea w

ater

system

DC

pow

er

supply

125V

DC

Em

erge

ncy D

GM

/C

－

Regu

lar use

Em

erge

ncy

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 1Ｂ ×

×M/C 2A

Em

erge

ncy u

se

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

.9K

V M

/C

480V

PC

D

C

O: operable X: damaged Sea Water System


2. How the accident developed

and 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-site

power 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 been

continuously improved

・Currently the closed cycle

cooling is in function

Sea water was initially injected into

the spent fuel pool; currently

injecting freshwater

Outage in progress

[Power supply] Emergency DG 6B

start up

[Sea water system] Total loss

3/19

Alternative RHRS was

started and the spent fuel

pool and reactor were cooled

Increase in spent fuel pool

temperature to near 70°C

3/20

Units 5, 6 cold shutdown

Installation of temporary RHRS

Installation of temporary power

supply

In operation

[Power supply] One off-site power

supply system secured

[Sea water system] Total loss apart

from Unit 3

3/12

Unit 3 cold

shutdown

Units 1, 2, 4

Water injection using MUWC

3/14

RHR startup

Water injection using RCIC

3/14 Units 1, 2 cold shutdown

3/15 Unit 4 cold shutdown

RHRC motor was replaced

Installation of temporary power

supply


-1000

1000

3000

5000

7000

3/1112:00

3/1118:00

3/120:00

3/126:00

3/1212:00

3/1218:00

3/130:00

3/136:00

3/1312:00

3/1318:00

3/140:00

3/146:00

3/1412:00

3/1418:00

3/150:00

3/156:00

3/1512:00

3/1518:00

3/160:00

0.00

2.00

4.006.00

8.00

10.00

3/1112:00

3/1118:00

3/120:00

3/126:00

3/1212:00

3/1218:00

3/130:00

3/136:00

3/1312:00

3/1318:00

3/140:00

3/146:00

3/1412:00

3/1418:00

3/150:00

3/156:00

3/1512:00

3/1518:00

3/160:00

逃がし弁機能（7.47,7.54,7.61MPa abs）

設計圧力（8.7MPa abs）

運転圧力（7.0MPa abs）

0.000

0.200

0.400

0.600

0.800

1.000

3/1112:00

3/1118:00

3/120:00

3/126:00

3/1212:00

3/1218:00

3/130:00

3/136:00

3/1312:00

3/1318:00

3/140:00

3/146:00

3/1412:00

3/1418:00

3/150:00

3/156:00

3/1512:00

3/1518:00

3/160:00


ベント実施圧力（0.723MPa abs）

R

x W

ate

r

Level [m

m]

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)

Earthquake （14:46）

Tunami （15:23）

Rx P

ressu

re

[MP

a]

D/W

&

S/C

Pre

ssu

re [M

Pa

]

0(TAF)

（3:50 ~ ）Depressurization Pressure Control

（0:00 ~ ）

（3:45 ~ ）

▼(18:30） Vent Line Configuration Completed

Cold Shut Down（14:46）

Overscale

Restoration of RHR system

2F Unit 1 Plant Parameter and Operation


• Operator’s 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

Condensat

e Storage

Tank

RPV

Reactor Building

Heat Exchanger Building

Heat rejection by

opening SRVs

Temperature

increase

Tsunami flooding Inoperable by

flooding

Equipment cooling system was not

available.

RHRC Pump

RHRS Pump

RHR Pump

RCIC MUWC

MSIV

Suppression

Chamber

(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 and

MUWC at low pressure condition was a critical factor for successful

reactor cooling.


0

20

40

60

80

100

120

140

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

（℃）

3/12 06:20～07:47S/C injection by FCS(A)3/12 07:10　D/W spray3/12 07:37　S/C spray

3/1311:32～13:26　14:29～14:37D/W spray

0

50

100

150

200

250

300

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

（kPa[gage]）

0

20

40

60

80

100

120

140

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

3/14 01:24RHR(B) started withS/C cooling mode

3/17 20:03～20:20Water transfer fromCondenser to S/C viaCST to monitorCondenser water level

3/1311:32～13:2614:29～14:37D/W spray

3/12 06:20～07:45S/C injection by FCS(A)3/12 07:10　D/W spray3/12 07:37　S/C spray

Variation of major parameters【２Ｆ－1】（from March 11 to 19）

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

S/C water temperature reached 100ºC (212F).

It eventually increased up to about 130ºC (266F).

Water injected to S/C through Hydrogen Recombiner cooler discharge line in order

to 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 projected

restoration time, as a back-up plan, TSC decided to make PCV vent

line up ready.

PCV pressure went up to about 280 kPa [gage] before restoration of

RHR, 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 cold

shutdown 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

設計圧力

（0.53MPa abs）

ベント実施圧力

（0.954MPa abs）

0.00

2.00

4.006.00

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

逃がし弁機能（7.28,7.35,7.41MPa 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

原子炉水位（燃料域)(A）（mm）

原子炉水位（燃料域)(B）（mm）

In Operation(Over Scale)

Rx W

ate

r

Le

ve

l [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)

（19:04）Sea Water

Order for Vent Preparation （0:06） ▼

（4:00） Fresh Water ［80t］（14:53）

（18:18 - 25）（21:30）

（14:52）

Earthquake （14:46）

Tunami （15:27）

Operation Unclear

Order for Vent ▼ （8:03）（14:30） D/W Pr decrease confirmed

Unit 1 R/B Explosion （15:36）

Core Damage Started due to MAAP Analysis

Rx P

ressu

re

[MP

a]

D/W

&

S/C

Pre

ssu

re [M

Pa

]

1F Unit 1 Plant Parameter and Operation

0(TAF)

Rx water level data revealed incorrect afterward


-4000

-2000

0

2000

4000

6000

3/1112:00

3/1118:00

3/120:00

3/126:00

3/1212:00

3/1218:00

3/130:00

3/136:00

3/1312:00

3/1318:00

3/140:00

3/146:00

3/1412:00

3/1418:00

3/150:00

3/156:00

3/1512:00

3/1518:00

3/160:00

0

2

4

6

8

10

In Operation (Over Scale)

0.00

2.00

4.006.00

8.00

10.00

3/1112:00

3/1118:00

3/120:00

3/126:00

3/1212:00

3/1218:00

3/130:00

3/136:00

3/1312:00

3/1318:00

3/140:00

3/146:00

3/1412:00

3/1418:00

3/150:00

3/156:00

3/1512:00

3/1518:00

3/160:00

逃がし弁機能（7.44,7.51,7.58MPa abs）設計圧力（8.7MPa abs）


0.000

0.200

0.400

0.600

0.800

1.000

3/1112:00

3/1118:00

3/120:00

3/126:00

3/1212:00

3/1218:00

3/130:00

3/136:00

3/1312:00

3/1318:00

3/140:00

3/146:00

3/1412:00

3/1418:00

3/150:00

3/156:00

3/1512:00

3/1518:00

3/160:00


ベント実施圧力（0.954MPa abs）

Rx W

ate

r

Le

ve

l [m

m]

RCIC

HPCI No Operation

SRV

FP/Fire Engine

PCV Vent



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





（19:５４）Sea Water

Order for Vent Preparation ▼ （17:30）

Depressurization （~18:00）

Earthquake （14:46） Tunami

（15:27）

▼(2:55) Operation confirmed


Unit1 R/B Explosion （15:36）


Rx P

ressu

re

[MP

a]

D/W

&

S/C

Pre

ssu

re [M

Pa

]

1F Unit 2 Plant Parameter and Operation Unit3 R/B Explosion （11:01）

Impact sound （6:00-6:10）

Valve Condition Unclear

Order for Sea Water Injection Preparation （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

3/1112:00

3/1118:00

3/120:00

3/126:00

3/1212:00

3/1218:00

3/130:00

3/136:00

3/1312:00

3/1318:00

3/140:00

3/146:00

3/1412:00

3/1418:00

3/150:00

3/156:00

3/1512:00

3/1518:00

3/160:00

設計圧力（0.53MPa

abs）

ベント実施圧力（0.954MPa

0.00

2.00

4.006.00

8.00

10.00

3/1112:00

3/1118:00

3/120:00

3/126:00

3/1212:00

3/1218:00

3/130:00

3/136:00

3/1312:00

3/1318:00

3/140:00

3/146:00

3/1412:00

3/1418:00

3/150:00

3/156:00

3/1512:00

3/1518:00

3/160:00

逃がし弁機能（7.44MPa,7.51MPa,7.58MPa）設計圧力（8.7MPa）

運転圧力（7.0MPa）

-4000

-2000

0

2000

4000

6000

3/1112:00

3/1118:00

3/120:00

3/126:00

3/1212:00

3/1218:00

3/130:00

3/136:00

3/1312:00

3/1318:00

3/140:00

3/146:00

3/1412:00

3/1418:00

3/150:00

3/156:00

3/1512:00

3/1518:00

3/160:00

I n Ope ratio n (Ove r Sc ale )

R

x W

ate

r

Le

ve

l [m

m]

RCIC

HPCI

SRV

D/D-FP

FP/Fire Engine

PCV Vent



● Fuel Range (mm)

○ Wide Range (mm)





（16:30）Sea Water

Order for Vent Preparation ▼ （17:30）

Earthquake （14:46） Tunami

（15:27）

Unit1 R/B Explosion （15:36）


Rx P

ressu

re

[MP

a]

D/W

&

S/C

Pre

ssu

re [M

Pa

]

1F Unit 3 Plant Parameter and Operation Unit3 R/B Explosion （11:01）

Order for Preparation ▼（17:12）

0(TAF)

(11:36) Trip

Automatic Start (12:35)

(16:03)

(2:42) Stop

（13:12）Sea Water Fresh Water （9:25）


（~9:08）Depressurization

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

After HPCI shut down, water injection

using D/D FP was implemented, however

not possible due to high reactor pressure


3. How We Responded to the

Accident 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 power

supply sources

What 1F site focused on during March 11-15


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

Work in complete darkness

In the service building. Many

scattered objects were also

on the floor.

Temporary power supply

Connect temporary

batteries to recover

instrumentations.

Major Activities at Fukushima Daiichi Unit 1

～Factors disturbing the recovery work (inside the building) ～

Scram

response

Preparations

for water

injection

Preparations

for venting

Water

injection

started

Venting

Deteriorating

operability

due to the

tsunami


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/4D

with temporary cable. The hydrogen explosion of Unit 1&3

caused damage of the temporary cable.

Scram

response

Preparations

for water

injection

Preparations

for venting

Water

injection

started

Venting

Deteriorated

operability

due to the

tsunami

Major Activities at 1F

～Factors disturbing initial recovery of instrumentations and power supply ～

Hurdles for the work:

Darkness and suspensions due

to aftershocks, tsunami alarms,

Puddles, openings of manholes,

debris and other obstacles

caused by the tsunami,

Influence of the hydrogen

explosions


Number of Aftershocks Greater than M 5.0

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

12/5 4/1

Da

ily N

um

be

r of A

fters

ho

cks G

reate

r th

an

M 5

.0

Cum

ula

tive N

um

ber

of A

fters

hocks G

reate

r th

an M

5.0

On March 11th alone

155 times > M 5.0

37 times > M6.0

3 times > M7.0

Total during first week

358 times > M 5.0


Instruments were monitored wearing a full face mask with a flashlight in

complete darkness

Supervising (2)

Supervising at a deputy

supervisor’s desk wearing

a full face mask in

complete darkness

Supervising (1)

Check indicated values only

with a flashlight in complete

darkness


～Factors disturbing the recovery work (inside the buildings) ～

Scram

response

Deteriorating

operability

due to the

tsunami

Water

injection

started

Venting

Preparations

for water

injection

Preparations

for venting


• 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 the

control room were unavailable.

Scram

response

Deteriorating

operability

due to the

tsunami

Water

injection

started

Venting

Preparations

for water

injection

Preparations

for venting

Major Activities at 1F Unit 1 <factors disturbing recovery work (outside the building) >


Scram

response

Deteriorating

operability

due to the

tsunami

Water

injection

started

Venting


～Containment Vessel Venting Operation (1) ～

Self-contained

breathing apparatus

Two valves, a PCV vent valve (MO valve) and a S/C vent valve (AO valve: small) were selected

as 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.

72

AO

ボンベ

210

MO ラプチャーディスク排気筒

1AO

ボンベ

閉

閉

83

AO閉

閉90

AO

0.549MPabsで破壊

RPV

D/W

RPVRPV

D/W

IA

IA

D/W最高使用圧力0.528MPabs

ベント実施圧力0.954MPabs

電磁弁

電磁弁

213

AO

Shift workers operation to

manually open

valve

MO

AO

AO

AO

AO

MO

Exhaust

stack

Closed

Closed

Closed

Closed

Solenoid

valve

Solenoid valve

Cylin

de

r

Cylin

de

r

D/W maximum

operating pressure:

0.528MPaabs

Ruptured

disc Broke at

0.549MPabs

Venting

pressure:

0.954MPaabs

Preparations

for water

injection

Preparations

for venting


Water

injection

started

Venting



72

AO

ボンベ

210


1AO

ボンベ

閉

閉

83

AO閉

閉90

AO

0.549MPabsで破壊

RPV

D/W

RPVRPV

D/W

IA

IA



電磁弁

電磁弁

213

AO

（25%開）

1st team proceeded to site to operate

PCV vent valve (MO valve) on the

2nd level of the R/B, and implemented

operation to open the valve manually.

R/B 2nd level R/B 1st level

South-side

double door

To 2nd level by

southeast stairs PCV vent valve

(MO valve)

North-side

double door

Operation to open PCV vent

valve (MO valve) successful

Access route to PCV vent valve (MO valve)

Manual

opening

operation

successful

MO

MO

AO

AO

AO

AO

Ruptured disc

Broke at 0.549MPabs

Air stack

Closed

Closed

Closed

Solenoid valve

Solenoid valve

Cylin

der

Cylin

der

D/W maximum operating pressure

Venting pressure

Closed

(25% open)

Operation to manually open

PCV vent valve (MO valve) Scram

response

Deteriorating

operability

due to the

tsunami

Preparations

for water

injection

Preparations

for venting


Water

injection

started

Venting



72

AO

ボンベ

210


1AO

ボンベ

閉

閉

83

AO閉

閉90

AO

0.549MPabsで破壊

RPV

D/W

RPVRPV

D/W

IA

IA



電磁弁

電磁弁

213

AO

（25%開）

2nd team entered the torus room (R/B B1F), but the valve was located at a direction of 180 degrees from where the team entered the torus room.

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

R/B 1st floor R/B B1F

S/C vent

valve

(AO valve)

Dose at the

north-side

double

door was

high, and

south-

bound

course was

selected

Manual operation was abandoned and another means were selected

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

Manual opening

operation

successful

AO

AO

Manual opening

operation abandoned

due to high dose

AO

AO MO

MO Ruptured disc

Broke at 0.549MPabs

Air stack

Closed

Closed

Closed

Solenoid valve

Solenoid valve

Cylin

der

Cylin

der

D/W maximum operating pressure

Venting

pressure

Closed

(25% open)

Operation to manually open S/C

vent valve (AO valve) valves

South-side

double door

North-side

double door

Deteriorating

operability

due to the

tsunami

Scram

response

Preparations

for water

injection

Preparations

for venting


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 how

to operate them.

Flashlights

Cable

Tools (screwdrivers, etc.)

Batteries taken from cars

Engine driven Generators*

Engine driven Air Compressors*

*They were in the warehouses

of the affiliated companies and

difficult to find.


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△

inoperable due to the



loss of cooling system

RHRC/RCRS(A,C) ×inoperable due to the

submerge of power

source and motor

×inoperable due to the

submerge of power

source and motor


submerge of power

source and motor


submerge of power

source 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○ stand-by △



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 to

submerge△


loss of cooling system○ operation △











MUWC

(alternative water injection)MUWC(Ｂ) ○ 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 cooling

systems

RHR(B)

including cooling

systems

LPCS

EDG(A)


Field Walkdown

• Challenges in conducting field walkdown

– Under continuous tsunami alerts, walkdown must be done in the field where a

lot 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 / component

functionality verified.

– Results were summarized and shared at TSC.

– TSC set priorities on recovery of RHR (B) cooling

systems by replacing motors and supplying power

from survived electrical buses and mobile power

vehicles 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.


Logistics in Emergency Situation • Procurement and transportation of Materials and Equipment

– Emergency procurement of motors, cable, mobile power vehicles, fuel oil and

mobile 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 Kashiwazaki

Kariwa NPP by trucks.

– Securing redundant communication measures were critically important when major

highway was damaged and public cell phone services were disrupted.

Mobile Power Vehicles Fuel oil delivery to the site Necessary materials and

equipment prioritized and listed


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 and

high 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


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 laid,

RHR (B) of Unit 1 started up at 1:24 on March 14 and other units followed.

• Finally at 15:42 on March 14

with the start up of Unit 4 RHR,

RHR of all four reactors of

Fukushima Daini started

operation.


Temporary Power Supply and Motor Replacement at 2F

Unit #3

Hx

Building

Unit #1

Reactor

Rad-Waste

Building

TSC

Main Office

Unit #4

Turbine

Unit #2

Hx

Building

Unit #1

Hx

Building

Unit #4

Hx

Building

Unit #2

Reactor Unit #3

Reactor

Unit #4

Reactor

Unit #3

Turbine

Unit #1

Turbine

Unit #2

Turbine

Mobile Power Supply Truck (500kVA)

Temporary Cables

Mobile Power Supply Truck (500kVA)

6.6kV/480V Transformer

6.6kV/480V Transformer

About 9 km of temporary cables

were laid and motors were

replaced.


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 cooling system

△

inoperable due to

loss of cooling

system

△

inoperable due to

loss of cooling

system

△

inoperable due to

loss of cooling

system

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 tie-line

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


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×

inoperable for loss of

core pressure×


core pressure×


core pressureRCIC

RWCU

EDG(B)

RHR(C )

Unit 2 Unit 3 Unit 4System

RHR(A)

including cooling

systems

RHR(B)

including cooling

systems

Unit 1

LPCS

EDG(A)


Overview of the 10-Unit Simultaneous Accidents

Date 1F 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 1:24

RHR 3/14 7:13

RHR

3/14 15:42

RHR

3/14 18:00

3/15 7:15

3/12 12:15

3/20 14:30

3/19 22:14

RHR

3/12 8:13

D/G-6B

3/22 10:35

P/C-4D

3/22 10:36

P/C-4D

3/20 15:46

P/C-2C

3/20 15:46

P/C-2C

3/19 5:00

RHR

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


Testimonies from the Field (Operators)

―In an attempt to check the status of Unit 4 D/G, I was

trapped 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 saved

my 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 I

couldn’t leave—I 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 was

overwhelmed.‖

―Unit 3 could explode anytime soon, but it was my turn to

go to the main control room. I called my dad and asked

him to take good care of my wife and kids should I die.‖


Testimonies from the Field (Maintenance Persons)

―We saw our car crashed by the explosion of the Unit 3. If

we had gotten on the car a few minutes earlier, all of us

would have been dead.‖

We were replacing fire hoses when the explosion of Unit 3

occurred. We felt almost dying since many large rubbles

were falling down to us. I urgently ran underneath a nearby

fire engine. One of my colleagues got injuries in his leg and

stomach.‖

―There were so many manholes opened by the tsunami. In

order to lay cables, we had to proceed step by step

carefully checking safety in the complete darkness.‖

―We were working in the Unit 3/4 control room when the

explosion occurred. I was resigned to my fate. Dose rate

was going up in the room after the explosion and we

desperately 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 around

us. I got into a panic for a while.‖


4. Summary


The 1F accident was caused by the simultaneous loss of multiple safety

functions 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 for

a extended period of time” and “the loss of the heat removal function of

the emergency seawater system for a extended period of time.”

Preparations had been previously made to receive power from neighboring

units in the event that AC power and DC power were not available. During the

accident, direct tsunami damage was so widespread that the neighboring

units were all in the same condition.

Summary of Lessons Learned

―Carefully consider the robustness of current design of

nuclear power plants and emergency preparedness

against beyond design basis events that could lead to

common cause failures regardless of their assumed

probability demonstrating a continuous learning

organization.‖


Success path regarding Cooling and Heat Removal from the Reactor

1)Promptly initiate core injection

methods using high-pressure cooling

water injection equipment

2)Initiate depressurization methods before losing

of high-pressure cooling water injection function

3)Stable low-pressure cooling water injection methods

should 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 operation

and plant conditions.

It is inevitable to maintain water injection and core cooling function thoroughly

and continuously even in poor environmental conditions.

Technical Lessons Learned


2F Key Success Factors

Accident mitigation by applying EOP and AMG

Prioritized restoration strategy based on Field Walkdown

Prompt restoration with success of emergency

procurement 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

TEPCO English website http://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

INPO—Special Report on Fukushima Daiichi Nuclear Power Station http://www.nei.org/resourcesandstats/documentlibrary/safetyandsecurity/reports/special-report-

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

EPRI—Fukushima 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.html

















http://www.nei.org/resourcesandstats/documentlibrary/safetyandsecurity/reports/special-report-on-the-nuclear-accident-at-the-fukushima-daiichi-nuclear-power-station

























http://my.epri.com/portal/server.pt?Abstract_id=000000000001023422

http://my.epri.com/portal/server.pt?Abstract_id=000000000001023422


Thank you for your attention!


5. References

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 Data Maximum Response Acceleration

against 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.


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

周期(秒)

加

速

度

(Gal)

Res_1FZ2011031114462R2_EW.wazRes_1f2_Ss-1_mat_EW.wazRes_1f2_Ss-2_mat_EW.wazRes_1f2_Ss-3_mat_EW.waz

(h=0.05)

0.02 0.05 0.1 0.2 0.5 1 2 50

1000

2000

3000

周期(秒)

加

速

度

(Gal)

2FZ2011031114463R2_NS2F3_mat_Ss-1H_NS2F3_mat_Ss-2H_NS2F3_mat_Ss-3H_NS

(h=0.05)

Fukushima daiich

period（s） period（s）

0 50 100 150-800

-400

0

400

800

時間(秒)

加速

度(G

al)

550

0 50 100 150-800

-400

0

400

800

時間(秒)

加速

度(G

al)

277

Fukushima daini

0.02 0.05 0.1 0.2 0.5 1 2 50

500

1000

1500

2000

周期(秒)

加

速

度

(Gal)


(h=0.05)

Observation records Design-basis seismic ground motion Ss-1H Design-basis seismic ground motion Ss-2H Design-basis seismic ground motion Ss-3H

0.02 0.05 0.1 0.2 0.5 1 2 50

500

1000

1500

2000

周期(秒)

加

速

度

(Gal)


(h=0.05)

Observation records Design-basis seismic ground motion Ss-1H Design-basis seismic ground motion Ss-2H Design-basis seismic ground motion Ss-3H

Unit 2（W-E） Unit 3（N-S）

time（s） time（s）

Acce

lera

tion

（Gal

）

Acce

lera

tion

（Gal

）

550 277

Acce

lera

tion

（Gal

）

Acce

lera

tion

（Gal

）

Intensity of the earthquake at the power stations


（C)GeoEye

Inundated Areas at 1F

Inundation throughout almost all areas where main buildings sited Units 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 flooded Fukushima

Daiichi

Unit

1 Unit

2

Unit

3

Unit

4 Unit

6

Unit

5

Radwaste

Processing

building

Elevation of major

Unit-1-4 buildings:

O.P.10m

Elevation of major

Unit-5,6 buildings:

O.P.13m


１号機２号機３号機４号機

運用補助共用建屋

６号機５号機

６号機ＤＧ建屋

O.P.+1 3 m

O .P.+1 0 m

O .P.+4 m

O .P.+4 m

原子炉建屋

タービン建屋

3u Emergency D/G

air inlet louver

Location of Openings from which Sea Water

could Flow into Main Buildings (Fukushima Daiichi Nuclear Power Station)

Turbine

building

Reactor

building

Unit 6 D/G building

Unit 5 Unit 6

Unit 1 Unit 2 Unit 3 Unit 4

▼：Openings at the ground level from

which sea water could flow into buildings

▼：Openings connected to underground

trenches/ducts where sea water could flow

into buildings


Inundated Areas at 2F

Inundation occurred throughout all areas along the sea, but it was not observed to

have inundated over the slope and into areas where major buildings are sited.

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

Inundation height in areas where principal buildings sited: OP approx. 12~14.5m

Inundation height in area south of Unit 1: OP approx. + 15~16m

Limited area was flooded

Inflowed

intensively

（C)GeoEye

Unit 2 Unit 1 Unit 3 Unit 4

Elevation of major

Unit-1-4 buildings:

O.P.12m


Location of Openings from which Sea Water

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

Inside Unit 1 heat exchanger building Units 3 & 4

Sea side of turbine building

▼：Openings at the ground level from which sea water could flow into buildings

▼：Openings connected to underground trenches/ducts where sea water could flow into buildings

Heat exchanger

building

Turbine

building

Reactor

building

Unit

1

Unit

2

Unit

3

Unit

4


Base level O.P.0m

Reactor building

Ocean-side area Main building area

breakwater

Design basis tsunami height O.P.+5.2m

Site level O.P. +12m

Water intake

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

against 5.2m Tsunami height

Site level O.P. +4m

Turbine building

Tsunami Height @1F v.s. 2F

4月9日記者発表

• The new design basis Tsunami height for 1F & 2F were evaluated based on the JSCE Tsunami assessment

methodology. (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 and

openings 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 highest tsunami water level

O.P. +5.7m

Base level O.P. 0m

-

-

-

- Assumed highest

tsunami water levelO.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-side area

Main building area

Water intake

Site level O.P. +4m

Safety measures has taken against 5.7m

Tsunami height

breakwater

Water

Pump

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-side area

Main building area

Water intake

Site level O.P. +4m

Safety measures has taken against 5.7m

Tsunami height

breakwater

Water

Pump

Design basis

tsunami height

O.P.+5.7m


Differences in Tsunami that hit Fukushima Daiichi

and Daini NPSs

1050

100150

福島第二

福島第一0

2

4

6

8

10

12

14

水深[m]Sea floor

displacement

[m]

Fukushim

a

Da

iich

i

Fu

ku

sh

ima

Dain

i

Ma

xim

um

tsu

na

mi h

eig

ht

［m

］

Peaks coinciding

↓

Tsunami height: High

Peaks not coinciding

↓

Tsunami height: Low

①

②

③

Same amplification rate

Water level

fluctuation from

each block Time T

Warm colored blocks

generated massive

tsunami wave heights

③

②

①

Tsunami of various magnitudes at a depth of

around 150m were amplified at the same rate

and struck at each nuclear power station

Water depth [m]

①

＋

②

＋

③

Postulated Tsunami Model


Permitted Design Basis(1)… Tsunami assessment

Tsunami assessment in construction permit

Fukushima NPSs

•Historical tsunamis of Iwate and Miyagi coast were larger than that of Fukushima

•Approved 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 Survey Group( http://www.coastal.jp/ttjt/) 07 May 2011

Inundation

Run-up

Unit Ground Level Tsunami Height〔m〕

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


Permitted Design Basis(2)… Tsunami assessment

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

（http://outreach.eri.u-tokyo.ac.jp/eqvolc/201103_tohoku/#Inversion 2011/3/18） 2011/3/11 source area

English edition

http://www.jsce.or.jp/committee/ceofnp/Tsunami/eng/tsuna

mi_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


Unit 1 Unit 2

Equipm

ent

Installed

building

Installe

d floor

Possi

bility

of

use

Status Equipme

nt

Installed

location

Installed

floor

Pos

sibili

ty of

use

Status

DG

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

DG 1B T/B B1FL × Submerged DG 2B Shared

pool 1FL ×

M/C

submerged

cannot be

used

－－－－－－－－－－

(M/C)

Emerge

ncy

high

voltage

switchb

oard

M/C 1C T/B 1FL × Water

damage M/C 2C T/B B1FL × Submerged

M/C 1D T/B 1FL × Water

damage M/C 2D T/B B1FL × Submerged

－－－－－ M/C 2E Shared

pool B1FL × Submerged

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

Voltage Switchboard (Immediately after the Tsunami)


Unit 3 Unit 4

Equipme

nt

Installed

location

Installe

d floor

Possi

bility

of

use

Status Equipme

nt

Installed

location

Install

ed

floor

Pos

sibili

ty of

use

Status

DG

DG 3A T/B B1FL × Submerge

d DG 4A T/B B1FL × Submerged

(Construction

in progress)

DG 3B T/B B1FL × Submerge

d DG 4B Shared

pool 1FL ×

M/C

submerged

cannot be

used

－－－－－－－－－－

(M/C)

Emerge

ncy

high

voltage

switch

board

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 Shared

pool B1FL × Submerged




Unit 5 Unit 6

Equipme

nt

Installed

location

Install

ed

floor

Po

ssi

bilit

y of

use

Status Equipment Installed

location

Install

ed

floor

Pos

sibili

ty of

use

Status

ＤＧ

DG 5A T/B B1FL ×

Related

equipment

Water

damage

DG 6A R/B B1FL ×

Related

equipment

Water

damage

DG 5B T/B B1FL ×

Related

equipment

Water

damage

DG 6B DG

building 1FL ○ －

－－－－－ HPCSD/G R/B B1FL ×

Related

equipment

Water

damage

(M/C)

Emerge

ncy

high

voltage

switchb

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 ○ －

－－－－－ HPCS

DG M/C R/B 1FL ○ －




Fukushima Daiichi: DG System Outline

All function

was lost after

the tsunami

Power was

secured in

Unit 6 (B)

only

[Fukushima Daini: DG System Outline]

Power was

secured in

Unit 3

(B)(H) and

Unit 4 (Ｈ)

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 water

pump

D/G Heat

exchanger

Sea

～～

～～

～～～～

Outside air

Air cooler D/G

Cooling water pump

Heat

exchanger

Sea water

pump Heat

exchanger

Cooling water

pump

D/G Sea

～～～～

～～～～


Power Access/Restoration Status Immediately

after 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 small

engine 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 engine

generator)

March 19 Backup transformer ~ Unit 1 & 2 temporary M/C (A) cable laid

March 20 Off-site power restored (P/C2C power received)



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)



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 23 Temporary RHRS alternative pump switched to off-site

power



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)

● After tsunami → Total loss of instrumentations due to loss

of offsite power and DC 125V

● March 11-14: to install temporary batteries to important

instrumentations, such as reactor water level, reactor

pressure, 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: March

23, 1F2: March 25, 1F3/4: March 22)

● ～Present: to prioritize the recovery of redundant

instrumentations for their reliability and to change step by step

from temporary battery to original power source


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

● May 9: to go into R/B to calibrate the D/W pressure

instrument @1F1

● May 10-12: to calibrate the fuel zone reactor water level

instrument @1F1

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

● June 3-4: to install the temporary reactor pressure and

Δpressure instrument at the test line of fuel zone reactor

water level instrument @1F1, to obtain more precise data on

reactor pressure and water level

● June 22-24: to install the temporary reactor pressure and

Δpressure instrument at the test line of fuel zone reactor

water level instrument @1F2

- not successful due to rapid evaporation of water inside instrumentation line by

high PCV temperature


Current status of important instrumentations @1F

Paramete

r/unit 1F1 1F2 1F3 1F4 1F5 1F6

Reactor

water level

Ａ：◎

Ｂ：△

Ａ：△

Ｂ：△

Ａ：△

Ｂ：△ N/A ○ ○

Reactor

pressure Ａ：◎ Ａ：○

Ａ：△

Ｂ：△ N/A ○ ○

Reactor

water temp. Not sampled Not sampled Not sampled N/A ○ ○

Temperatur

e around

RPV

○ ○ ○ N/A N/A N/A

D/W

pressure ◎ △ ○ N/A N/A N/A

S/C

pressure ○ × ○ N/A N/A N/A

CAMS rad

monitor D/W：×

S/C：○

D/W：○

S/C：○

D/W：○

S/C：○ N/A N/A N/A

S/C

temparature ○ ○ ○ - - -

◎：calibrated, ○：assumed to be intact, △：under continuous observation, ×：failure


Unit 1 Isolation Condenser

R

PV

Primary Containment

Open to the Air

Fire protection system Pure water make up system

MO

Ｂ system Ａ system Isolation

Condensor

1B

10A 10B

3A

3B

PLR P’P

MO

MO

MO

MO

MO

MO

MO MO

MO

1A

2B 2A

4A

4B

①Initiating system by

opening the valve

② Reactor steam is cooled by Isolation condenser coolant tank

④Condensate water return

back to RPV driven by

natural convection force

③Heated water in the tank

released 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 )

Sea

Tb

Condenser

H/W

Gen

CST

Filtrated Water Tank

SLC

Stac

k

Sea

CCS

D/G CCSW

SRV

CRD

HPCI

CP RFP

ＣWＰ

CS MUWC

DD FP

IC

S/C vent valve

D/W vent valve

RP

V

from CST＆H/W

Sea

:Operable

:Inoperative due to power loss

: Briefly Operative


The automatic isolation interlock of the IC was actuated due to the loss of power

caused by the tsunami and then lost its function. Afterwards, the reactor water

level decreased in a short period of time and the core was exposed (Dropped to

TAF), leading to the core damage. During this time, it was difficult to understand

plant status due to the loss of power.

Based on the analysis results, it is evaluated that the core would have been

damaged regardless of the continuation of the operation of the IC after 18:18.

When the water level gauge was temporarily restored using a temporary power

source after 21:00 on March 11, a reading was obtained showing that the reactor

water level was above TAF. However at this point, there was not enough

information to comprehensively determine that this reading was erroneous. At the

Emergency 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 damage

was recognized due to the increase in dose rate in front of the double doors of the

reactor building at around 23:00 on March 11 and the unusually high reading for

the dry well pressure that was obtained for the first time at around 0:00 on March

12.

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


On March 12 at around 3:00, the reactor pressure decreased, although reactor

depressurization operation was not conducted. This implies that damage to the

reactor cooling water pressure boundary had occurred due to core damage. This

implies that core damage might have progressed to a considerable extent in a

short 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 is

consistent with the events actually observed.

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


1F Unit 2 Schematic System Diagram (After Tsunami)

Sea

Tb

Condenser

H/W

Gen

CST


SLC

Stac

k

Sea

RHR

D/G RHRS

SRV

CRD

HPCI

LPCP MD-RFP

ＣWＰ

CS

MUWC DD FP

S/C vent valve

D/W vent valve

:Operable


RP

V

TD-RFP

from CST＆H/W

CST

RCIC

HPCP

Sea

:Inoperative


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 level

started.

About 1 hour and 20 minutes later after the RCIC shutdown, the fire engine’s

pump was started up and preparations for low-pressure water injection were

ready. However the SRV did not immediately operate during reactor

depressurization.

It is considered that core damage occurred because low-pressure water injection

did not function immediately after the SRV was activated and reactor

depressurization was achieved. Because of the rapid decrease in the retained

water 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 core

damage started due to the decrease in reactor water level followed by

degradation of the function of the RCIC.

Summary of the Plant Behavior in Unit 2


1F Unit 3 Schematic System Diagram (After Tsunami)

Sea

Tb

Condenser

H/W

Gen

CST


SLC

Stac

k

Sea

RHR

D/G RHRS

SRV

CRD

HPCI

LPCP MD-RFP

ＣWＰ

CS

MUWC DD FP

S/C vent valve

D/W vent valve

RP

V

TD-RFP

from CST＆H/W

CST

RCIC

HPCP

Sea

:Operable


:Inoperative


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

activating the diesel-driven fire pump. However, because the reactor pressure

was higher than the water injection pressure, switching to low-pressure water

injection was not immediately successful after shutdown of the high-pressure

systems (HPCI). This caused degradation of cooling and thus leading to core

damage.

S/C venting was conducted and repeated several times. The monitoring car

reading near the main gate increased temporarily. However no large increase in

the background level was observed.

In addition, the hydrogen that was generated following the core damage was not

completely retained in the PCV and leaked into the reactor building, and is

considered to have caused the explosion of the reactor building.

Summary of the Plant Behavior in Unit 3