Appendix-1

Progression of Events at Each Plant (Chronology)

Form

External AC power
DC power (A), (B)Emergency DG
Sea water system
2011/3/11

Fukushima Dai-ichi
Unit 1
Mark 1(BWR-3)

Fukushima Dai-ichi
Unit 2
Mark 1(BWR-4)

Fukushima Dai-ichi
Unit 3
Mark 1(BWR-4)

Fukushima Dai-ichi
Unit 4
Mark 1(BWR-4)In operation

In operation

In operation

Stopped(Regular inspection)

×
×
×
×

×
×
×
×

Earthquake occurred (14:46)
Scram

×
×
×

×
×
×
×

Earthquake occurred (14:46)

Earthquake occurred (14:46)

Earthquake occurred (14:46)

Scram

Scram

○(2 systems)

Fukushima Dai-ichi
Unit 5
Mark 1(BWR-4)
Stopped(Regular inspection.
Fuel loaded)

Fukushima Dai-ichi
Unit 6
Mark 2(BWR-5)
Stopped(Regular inspection.
Fuel loaded)

Fukushima Dai-ni
Unit 1
Mark 2(BWR-5)

Fukushima Dai-ni
Unit 2
Improved Mark 2(BWR-5)

Fukushima Dai-ni
Unit 3
Improved Mark 2(BWR-5)

Fukushima Dai-ni
Unit 4
Improved Mark 2(BWR-5)

Onagawa
Unit 1
Mark 1(BWR-4)In operation

In operation

In operation

In operation

In operation

××○(2 systems)○(2 systems)○(1/3 units)○(1/4 lines)○(2 systems)○(1/4 lines)○(2 systems)

×

×
×

×
×

○(1/4 lines)○(2 systems)○(2/3 units)○(2/3 systems)○(1/4 lines)○(2 systems)○(1/3 units)○(1/3 systems)

Earthquake occurred (14:46)

Earthquake occurred (14:46)

Earthquake occurred (14:46)

Earthquake occurred (14:46)

Scram

Scram

Scram

×
×
Earthquake occurred (14:46)

Onagawa
Unit 2
Improved Mark 1(BWR-5)
Under regularinspection, but activatedjust before theOnagawa
Unit 3
Improved Mark 1(BWR-5)Tokai Dai-ni
Unit 2
Mark 2(BWR-5)In operation

In operation○(1/5 lines)○(2 systems)○(2/2 units)○(2/2 systems)○(1/5 lines)○(2 systems)○(1/3 units)○(1/3 systems)○(1/5 lines)○(2 systems)○(3/3 units)○(3/3 systems)○(2 systems)○(2/3 units)○(2/3 systems)

Earthquake occurred (14:46)

Earthquake occurred (14:46)

Earthquake occurred (14:46)

Earthquake occurred (14:46)

Earthquake occurred (14:46)

Scram

Scram

Scram (Shutdown cooling)

Scram

Scram

×

Fire started (Arc discharge inregular electrical panel 14:57)

IC activated (14:52)

RCIC activated (14:50)/ stopped (15：28)

RCIC activated (15:05)/ stopped (15：25)

Tsunami hit(1st wave： 15:27／2nd wave:
15:35)

Tsunami hit(1st wave： 15:27／2nd wave:
15:35)

Tsunami hit(1st wave： 15:27／2nd wave:
15:35)RCIC activated (15:39)

RCIC activated (16:03)

RCIC manuallyactivated (15:26)
RCIC manuallyactivated (14:59)
Tsunami hit(1st wave： 15:27／2nd wave:
15:35)

Tsunami hit(1st wave： 15:27／2nd wave:
15:35)

Tsunami hit(1st wave： 15:27／2nd wave:
15:35)

Tsunami hit (1st wave：
15:22)

Tsunami hit (1st wave：
15:22)

Tsunami hit (1st wave：
15:22)

Tsunami hit (1st wave：15:22)

Tsunami hit (around 15:29
Tide indicator at maximum
water level)

RCIC activated(15:36)

Core depressurized(SRV operation 15:41)

Core depressurized(SRV operation 15:46)

Core depressurized(SRV operation 15:46)

Core depressurized(SRV operation 17:10)

Core damage begun(18:46). By simulation

Core depressurized(SRV operation 15:55)

RCIC activated(15:43)

RCIC activated(16:06)RCIC activated (15:54)

RCIC automatically stopped(18:29)Large quantity of hydrogengenerated/accumulated

D/W cooling system activated(17:53)D/W cooling system activated(20:02)

D/W cooling system activated(20:12)

D/W cooling system activated(19:14)

Spent fuel pool cooling (FPC
pump manually activated
19:30)

Hydrogen
explosion(15:36)

SRV automatically opened(core pressure 8MPa maintained
1:40)

RCIC stopped (11:36)

Electrical supply vehicle
damaged (15:36)

Water injection begun(MUWC system 0:00)

Top valve of reactor
pressure vessel opened (6:06)

HPCI activated (12:35)

Power supply begun from Unit 6
DG (DC recharge 8:13)

Power supply begun to Unit 5(DC recharge 8:13)

2011/3/13

Core depressurized(SRV operation
approx. 16:40)
Spent fuel pool cooling (FPC
pump manually activated
20:29)RCIC manually stopped(23:11)

RHR pump manuallyactivated (SHC mode
23:46)

RHR pump activated (SHC
mode 23:51)

Cold shutdown (0:58)

Nuclear reactor scram/reset(4:49)

Nuclear reactor rapid
depressurization begun (3:50)

Water injection begun(MUWC system 4:50)

RHR S/C spray mode begun(2:41)

S/C cooling (from MUWC to
FCS7:23)

RHR pump manuallyactivated (SHC mode
12:12)RCIC manually stopped (4:58)

RCIC manually stopped (4:53)

RHR manuallyactivated (SHC mode
begun 9:37)

S/C spray (MUWC system 7:35)

Cold shutdown
maintained (12:12～)

S/C cooling (MUWC from
FCS line 6:20)

S/C cooling (MUWP from
FCS line 6:30)
S/C cooling stopped (MUWP
7:52)

PCV pressure resistant ventline structure completed(18:30)

PCV pressure resistant ventline structure completed(10:58)

PCV pressure resistant ventline structure completed(12:13)

Cold shutdown (12:15)

Water injection to nuclear
reactor (switch to HPCS 11:17)

Core depressurized(SRV operation 21:52)

RCIC manually stopped (21:45)

Water injection to nuclear
reactor begun (MUWC 21:54)

RCIC automatically stopped(0:16)
Water injection begun (MUWC

Tsunami hit (1st wave：15:32)

RCIC manuallyactivated (15:36)

Water injection begun(MUWC system 22:53)

RHR manually activated (SHC
cooling mode 2:39)

S/C cooling stopped (MUWC
7:45)

Tsunami hit (around 15:29
Tide indicator at maximum
water level)

Water injection to nuclear
reactor begun (CRD pumpmanually activated 20:20)

2011/3/12
D/W pressure rise(to 0.84MPa 2:30)

Tsunami hit (around 15:29
Tide indicator at maximum
water level)

Cold shutdown (1:17)

RCIC manually stopped (13:11)
transition to HPCS

PCV pressure resistant vent line
structure complete(11:52)
Nuclear reactor water injection
stopped (HPCS 13:48)

RHRS, RHRC pump activated(incoming power frommakeshift cable 20:17/21:03)

HPCI stopped (2:42)
Core exposure begun(Water level ＝TAF attained
4:15)

Core damage begun(around 8：46). By
simulation
Large quantity of hydrogengenerated/accumulated

Hydrogen back flew
(From Unit 3)

Nuclear reactor
depressurized (Releasesafety valve @ 9:08)
Fresh water injection from fire
trucks begun (with boric acid
9:25)
SC vent AO valve (large valve)
opened (12:30)

Power supply begun from Unit 6
DG (MUWC system. 18:29)

Fire trucks damaged (@11:01)

SC vent AO valve (small valve)
opened (5:20)

Core depressurized(SRV opened 5:00)

Loss of cooling function wasdetermined(RCIC stopped (@13:25))

Sea water supply begun fromstorage to reverse valve pit(9:20)

Water injection to nuclear
reactor begun(MUWC 5:30)

Core depressurized(SRV opened @18:00)

Self Defense Force water supply
vehicles arrive, supplied fresh
water from reverse valve pit(10:53)

Water supply to spent fuel pool
begun
(MUWC 9:27)

Fuel rods completely exposed(Water level＝TAF-3700mm
18:22)

Hydrogen explosion(11:01)

Nuclear reactor water injection
begun (Make Up Water Pump
system. 13:20)

Supplemental external power
recovered (19:37)

2011/3/14
Emergency auxiliary coolingsystem activated (EECW.
Incoming power frommakeshift power 1:44)

Emergency auxiliary coolingsystem activated (EECW.
Incoming power frommakeshift power 3:20)

RHR pump activated (S/C poolcooling begun 3:50)

EECW manually activated(received power from supply
vehicle 11:00)

Water injection to
nuclear reactor begun(RHR LPCI mode
10:05)

Core damage begun(@19:46). By
simulation

Water injection to spent fuelpool begun (FPMUW system
16:30)

Large quantity of hydrogengenerated/accumulated

Cold shutdown (17:00)

Water injection to
nuclear reactor begun(RHR LPCI mode
10:48)

RHR S/C spray mode begun(16:02)

Water injection to
nuclear reactor begun(RHR LPCI mode
18:58)
Cold shutdown (18:00)
RHR pump activated(Shutdown coolingmode 23:43)

Sea water injection begun
by fire trucks (19:54)

2011/3/15

Pressure incontainment vessel S/C
indicated 0MPa (abs)(6:00-6:10)

Hydrogen explosion(6:12)

Cold shutdown (7:15)

Cold shutdown (0:40)

2011/3/16
Switched to normal external
power (15:47)

2011/3/17
2011/3/18
Passage to roof opened(3 spots 13:30)

Passage to roof opened(3 spots 17:00)

RHR makeshift sea water pumpactivated(emergency system 1:55)

RHR makeshift sea water pumpactivated(emergency system 21:26)

RHR manually activated (Fuelpool cooling @5:00)

RHR manually activated (Fuelpool cooling 22:14)

RHR pump activated(Shutdown-cooling mode
12:25)

RHR pump activated(Shutdown-cooling mode
18:48)

Cold shutdown (14:30)

Cold shutdown (19:27)

2011/3/19

2011/3/20

Unauthorized copying or distribution of this file is prohibited. Copyrights Team H2O Project all rights reserved

Appendix-1
Unit 1
Electricalpanel

Emergency
ＤＧ

Emergency

Progression of Events at Each Plant (Chronology)
Fukushima Dai-ichi
Unit 3
Unit 4

Unit 2Usabil Electrical
ity panel

ＤＧ１Ａ

×

ＤＧ1Ｂ

×

ＤＧ２Ａ
ＤＧ２Ｂ
（Air cooling）

Usabil Electrical
ity panel

Usabil Electrical
ity panel

ＤＧ３Ａ

××（※１） ＤＧ３Ｂ

×

×

ＤＧ４Ａ
ＤＧ４Ｂ
（Air cooling）

Unit 5Usabil Electrical
ity panel

Unit 6

Usabil Electrical
ity panel

ＤＧ５Ａ（※２）××（※１） ＤＧ５Ｂ（※２）

×

×

×

○

ＤＧ1Ｂ

×

×（※2）

ＤＧ1H

Usabil Electrical
ity panel

UsabilityElectrical
panel

ＤＧ２Ａ

×（※2） ＤＧ３Ａ

×（※2） ＤＧ４Ａ

×（※2）

DG A

○

DG A

ＤＧ２B

×（※2） ＤＧ３Ｂ

×（※2）

DG B

○

DG B (※2)×

ＤＧ2H

×（※2） ＤＧ3H

○

ＤＧ４Ｂ

○

ＤＧ4H

○

UsabiliElectrical panelty

HPCS D/G (※2)

Usabilit
Electrical panely○ (non-loadstandby）

× Sea waterpump
stopped×Sea waterpump
stoppedDG A
DG B
HPCS D/G

Usability

Electricalpanel

Usability○

ＤＧ２C (※2)×Sea water
pump stopped(DGS)(standby）○(standby）○(standby）

ＤＧ２D

○

ＤＧ２Ｈ

○

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／Ｃ６－１Ｃ○

Ｍ／Ｃ６－2Ｃ○

Ｍ／Ｃ６－3Ｃ○

Ｍ／Ｃ－2Ｃ×

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／Ｃ６－１Ｄ○

Ｍ／Ｃ６－2Ｄ○

Ｍ／Ｃ６－3Ｄ○

Ｍ／Ｃ－2Ｄ○Ｍ／Ｃ ２Ｅ×

Ｍ／Ｃ 4Ｅ×

HPCS DG M/C○Ｍ／Ｃ １H×

Ｍ／Ｃ 2H○

Ｍ／Ｃ 3H○

Ｍ／Ｃ 4H○

Ｍ／Ｃ６－2H○

Ｍ／Ｃ６－3H○

Ｍ／Ｃ－HPCS○

M/C 6A-1

×

M/C 1A-1○

M/C 2A-1○

M/C 3A-1○

M/C 4A-1○

Ｍ／Ｃ６－１Ａ ×Damaged by Ｍ／Ｃ６－2Ａ○

Ｍ／Ｃ６－3Ａ○

Ｍ／Ｃ－2Ａ-1

×

M/C 6A-2

×

M/C 1A-2○

M/C 2A-2○

M/C 3A-2○

M/C 4A-2○

Ｍ／Ｃ６－１Ｂ

×

Ｍ／Ｃ６－2Ｂ○

Ｍ／Ｃ６－3Ｂ○

Ｍ／Ｃ－2Ａ-2

×

M/C 6B-1

×

M/C 1B-1○

M/C 2B-1○

M/C 3B-1○

M/C 4B-1○

Ｍ／Ｃ６－１Ｓ×

Ｍ／Ｃ６－２SA-1○

Ｍ／Ｃ６－3SA-1○

M/C 6B-2

×

M/C 2B-2○

M/C 4B-2○

Ｍ／Ｃ６－1Ｅ

××

Ｍ／Ｃ 2Ａ×

Ｍ／Ｃ 2Ｂ
Ｍ／Ｃ ２SA

Ｍ／Ｃ １Ｓ×

Ｍ／Ｃ ３Ａ×

Ｍ／Ｃ 4Ａ××

Ｍ／Ｃ ３Ｂ×

Ｍ／Ｃ 4Ｂ××

Ｍ／Ｃ ３SA××
Ｍ／Ｃ ２SB

Ｍ／Ｃ 5Ａ××

Ｍ／Ｃ ３SB×

earthquake

Ｍ／Ｃ 5Ｂ×

M/C 1B-2○

M/C 3B-2○

Ｍ／Ｃ６－２SB-1○

Ｍ／Ｃ６－3SB-1○

Ｍ／Ｃ－2Ｂ-1

×

M/C 5SA-1

×

M/C 1SA-1○

M/C 3SA-1○

Ｍ／Ｃ６－2SA-2○

Ｍ／Ｃ６－3SA-2○

Ｍ／Ｃ－2Ｂ-2

×

M/C 5SA-2

×

M/C 1SA-2○

M/C 3SA-2○

Ｍ／Ｃ６－2SB-2○

Ｍ／Ｃ６－3SB-2○

M/C 5SB-1

×

M/C 1SB-1○

M/C 3SB-1○

Ｍ／Ｃ－2E×

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 4-1C○P/C 4-2C○P/C 4-3C-1○

P/C 2C×

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 4-1D○P/C 4-2D○

P/C4- 3C-2○

P/C 2D○P/C 4Ｅ×

P/C 6E○P/C 1D-1○

P/C 2D-1○

P/C 3D-1○

P/C 4D-1○

P/C 4-3D-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 4-1A×

P/C 4-2A○

P/C 4-3D-2○

P/C 2B×

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 4-1B×

P/C 4-2B○

P/C 4-3A-1○

P/C 2S×

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 4-1S×

P/C 4-2SA○P/C 4-3A-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 4-2SB○P/C 4-3B-1○

P/C 5SＡ×

P/C 1B-2○

P/C 2B-2○

P/C 3B-2○

P/C 4B-2○

P/C 4-3B-2○

P/C 5SＡ-1

×

P/C 1SA○P/C 3SA○P/C 4-3SA-1○

P/C 5SB×

P/C 1SB○

P/C 3SB○

P/C 4-3SB-1○

P/C 4-3SA-2○

P/C 4-3SB-2○

P/C 1A×

P/C 1B×

P/C 1S×

P/C ２Ｅ×

P/C ２Ａ○P/C ２Ａ-１

×

P/C ２Ｂ○P/C ２ＳＢ

Sea water
systemＤＧ１Ａ

Usabil Electrical
ity panel×

Ｍ／Ｃ １Ｂ

DC
power

×（※2）

ＨＰＣＳ ＤＧ

Usabil Electrical
ity panel

Tokai Dai-ni

×NormalNormal（Air cooling）

Electricalpanel

Onagawa (Tohoku Electric Power Co)
Unit 2
Unit 3

Unit 1

Ｍ／Ｃ １Ｄ

Ｍ／Ｃ

Ｐ／Ｃ

ＤＧ６Ｂ

Usability

Unit 4

Ｍ／Ｃ １Ｃ

Ｍ／Ｃ １Ａ

Emergency

ＤＧ６Ａ

Fukushima Dai-ni
Unit 2
Unit 3

Unit 1ＤＣ１２５Ｖ
main&transfer
bus 1Ａ
ＤＣ１２５Ｖ
main&transfer
１２５ＶＤＣ bus 1Ｂ

××

ＤＣ１２５Ｖ
main&transfer
bus 2Ａ
ＤＣ１２５Ｖ
main&transfer
bus 2Ｂ×××

P/C ３Ｂ×

P/C ３ＳＡ×

P/C ３ＳＢ

ＤＣ１２５Ｖ
main&transfer
bus 3Ａ
ＤＣ１２５Ｖ
main&transfer
bus 3ＢP/C 4Ｂ○

×○○

ＤＣ１２５Ｖ
main&transfer
bus ４Ａ
ＤＣ１２５Ｖ
main&transfer
bus ４Ｂ××

ＤＣ１２５Ｖ
main&transfer
bus 5Ａ
ＤＣ１２５Ｖ
main line
board 5Ｂ○○

ＤＣ１２５ＶDIST CENTER 6
Ａ

ＤＣ１２５ＶDIST CENTER 6B○○

ＤＣ１２５Ｖ
main line
boardＡ
ＤＣ１２５Ｖ
main line
board Ｂ○○

ＤＣ１２５Ｖ
main&transfer
bus Ａ
ＤＣ１２５Ｖ
main&transfer
bus Ｂ

○

○

ＤＣ１２５Ｖ
main&transfer
bus Ａ
ＤＣ１２５Ｖ
main&transfer
bus Ｂ

○

○

ＤＣ１２５Ｖ
main&transfer
bus Ａ
ＤＣ１２５Ｖ
main&transfer
bus Ｂ

○

○

１２５ＶDC
main&transfer
bus 1Ａ
１２５ＶDC
main&transfer
bus 1Ｂ○

１２５ＶDC main&transfer bus 2Ａ○

１２５ＶDC main&transfer bus 3Ａ○○

１２５ＶDC main&transfer bus 2Ｂ○

１２５ＶDC main&transfer bus 3Ｂ○

ＤＣ１２５Ｖ
main&transfer
bus 2Ａ
ＤＣ１２５Ｖ
main&transfer
bus 2Ｂ

○

○

A/B

Ａ

CCS A

×

ＲＨＲＳ Ａ×

ＲＨＲＳ Ａ×

ＲＨＲＳ Ａ×

ＲＨＲＳ Ａ×

ＲＨＲＳ Ａ×

ＲＨＲＳ Ａ×

ＲＨＲＳ Ａ×

ＲＨＲＳ Ａ×

ＲＨＲＳ Ａ×

ＲＨＲＳ Ａ○ＲＳＷ Ａ

RHRS A

×

CCS B

×

ＲＨＲＳ Ｂ×

ＲＨＲＳ Ｂ×

ＲＨＲＳ Ｂ×

ＲＨＲＳ Ｂ×

ＲＨＲＳ Ｂ×

ＲＨＲＳ Ｂ×

ＲＨＲＳ Ｂ×

ＲＨＲＳ Ｂ○ＲＨＲＳ Ｂ×

ＲＨＲＳ Ｂ

○

ＲＳＷ Ｂ

ＲＳＷ Ａ
○
× ＲＣＷ/ＲＳＷ ＲＳＷ Ｂ

○

Ｂ

○

RHRS B○

HPCS DGSW

×

HPCSS

×

HPCSS

×

HPCSS

○

HPCSS

○

ＨＰＳＷ

× ＨＰＣＷ ＨＰＳＷ
submerged○

HPCS DGS○

External power×
All 6 lines were lost due to the earthquake○
3/4 lines were lost due to earthquake（Tomioka line 1L only 500kV continued to receive power）

submerged○
4/5 lines were lost due to earthquake（Matsushima Main line 1L Only 275 kV survived）

×
Both lines were lost due
to earthquake

Remarks

Information on DC power of system-H was omitted.
：Lost functions：Unable to activate due to electrical board and/or cooling system were lost
：Incoming power was inaccessible due to the loss of electrical supply source

Loss of functions below were based on the estimation by the project;
・ Onagawa's M/C, P/C, and Tokai Dai-ni's P/C electrical panels

Unauthorized copying or distribution of this file is prohibited. Copyrights Team H2O Project all rights reserved

Appendix-1

Progression of Events at Each Plant (Chronology)
Fukushima Daiichi 1

Fukushima Daiichi 2

Fukushima Daiichi 3

Fukushima Daiichi 4

Fukushima Daiichi 5

Fukushima Daiichi 6

×

×

×

×

×

×

Emergency M/C board secured (not-

×

×

×

×

○

Fukushima Dai-ni Fukushima Dai-ni Fukushima Dai-ni Fukushima Dai-ni
Onagawa 1
Onagawa 2
12
3
4×Due to damage of
○
○
○
○
○
M/C
○
○
○
○
○
○

Emergency P/C board secured （notsubmerged）?

×

×

○

×

○

○

○

○

○

○

○

×

○
○ Shared fromunit 6○○ Recharged by

○

○

○

○

○

○

○

○(2 units）○(3 units）

×○(3 units）○（１unit） 2 units
submerged-

Item

Content

External power External power secured?

DC power board secured (not-submerged)?
DCelectrical board DC board battery maintained?

××○ Emergency
electrical board
available
×--× Run out-

Emergency DG function maintained (notsubmerged)?
Emergency DG function maintained (coolingwater secured）?

×○（1 unit）

×○(1 unit）-

× Pump submerged-

× Pump submerged × Pump submerged

HPCI/HPCS× Function lost× Function lost× Stopped after
depletion of DC
power

× Sea water pumpNA (underNA (underNA (under
lost due to
shutdown cooling) shutdown cooling) shutdown cooling)
submergence

ＩＣ／RCIC× IC function
incomplete and lost
function later× Functioned at first× Stopped after DC NA (underNA (underNA (under(reason unknown),○
then lost after as-is
power depletion
shutdown cooling) shutdown cooling) shutdown cooling)
condition maintained.

SLC function maintained?

× Power lost

CRD function maintained?

× Power lost

Emergency
electricalboard

Emergency DG

High pressure
cooling system

× Power lost. Electric
supply vehicle
× Power lost
destroyed by
explosion
× Power lost. Electric
supply vehicle
× Power lost
destroyed by
explosion

× Recovery of D/DFP
Low pressure
alternative
cooling systemfailed. Water supplied from × Power lost
fire truck to FP line

FP

×D/D Injection from FP failed(core pressure too high), watersupplied from fire trucks to FP line

DG

Onagawa 3

Tokai Dai-ni

○

×

○

○

○

○

○

○

○

○

○

○

○

○

○

○

○(3units）○(3 units）○(2 units）○(3 units）○(3 units）○(3 units）

× Pump submerged○(2 units）1 unit
submerged○(1 unit）2 units
submerged○(2 units）○(1 unit）2 units
submerged○(3 units）○(2 units）1 unit
submerged

× Fresh watercooling pumpfunction lost

○

○

○

× Pump function
lost due tosubmergence

○

○

○

○

○

○

○

○

○

× Power lost× Power lost○○（1/2 systems）

○

○

○

○

○

○

○(1/2 systems）

× Power lost× Power lost○○(1/2 systems）

○

○

○

× External power
lost due to M/Cdamage○（1/2 systems）○○(1/2 systems）

× Power lost× Power lost

○ Recharged by

○

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○

○

－(unconfirmed）－(unconfirmed）－(unconfirmed）－(unconfirmed）

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DG

MUWC／MUWP

× Power lost (pump × Power lost (pump × Power lost (pump × Power lost (pump ○ Shared fromsubmerged)
submerged)
submerged)
submerged)
unit 6

CS/CCS/RHR/LPCS× Power & sea
water pump lost× Power & sea
water pump lost× Power & sea
water pump lost× Power & sea
water pump lost× Power & sea water × Power & sea water × Power & sea water × Power & sea water
pump lost （recovered pump lost （recovered pump lost （recovered pump lost （recovered○（１/2 systems）
by makeshiftby makeshiftby makeshiftby makeshift
equipment）
equipment）
equipment）
equipment）

Sea water pump CCS, RSW, RHRS, HPSW function maintained(not-submerged）?

×

×

×

×

×

×

×

×

Plant condition

× Explosion

× Zero pressurein S/C× Explosion

× Explosion

○

○

○

○

Low pressure
cooling system

Cold shutdown accomplished?

Even if the LPCI
was set up, had it
been able to injectsufficient water tocool down the
core? (Further
research needed)
Remarks

LessonLoss of all AC
power disabledcontrol room'sfunction such as
monitoring andoperation, anddelayed recovery
actions. Very
important to
conduct training
for extreme
conditions like this.

If an electric supply If an electric supply As it was under
Pressure in RPV
vehicle wasvehicle andregular inspection, was high as it wasavailable, HPCI
ultimate heat sink recovery of FPC
testing reactor
could have been
were prepared till was important. The leakage of regular
maintained eventhe run-out ofwater in spent fuel inspection.
after battery
batteries, the worst pool was estimated Depressurized bydepletion. But the could have been
to last for about a opening the top
explosion at Unit 1 avoided.
week. Explosion
vent of the RPV.
destroyed ongoing
due to the backline-up and neverflow of hydrogenrecovered before
from Unit 3 wascore damage
not expected at all.
began.

As securing DC
power provides
more time forrecovery, it is very
important toprevent
submergence ofbatteries and DC
panels.

○ Recharged by
DG

In regularinspection.

Based on the
Cooling shutdown Cold shutdown was Important to noticeunderstanding that was performed by achieved because that if even one
hydrogen is lightsharing power from air cooling DG was external powerand easily leak
Unit 6. It would be not submerged and source were
anywhere,effective for all the ultimate heat sink available, cold
countermeasures to reactors to be able was not the sea.
shutdown will be
release into the air to share with power Diversity andachieved.
or to decrease its
sources each other. multiplicity ofdensity (e.g.
There was no
power source
recombiner) would accommodation
would be effective.
be essential
between 1-4 and 56.

× Power & sea water
pump lost （recovered○by makeshift
equipment）○(1/2 systems） As
was right after
activation, there's no
problem○○(１/2 systems）○（2/3 systems）○(1/3 systems）○○(1/3 systems）○○（2/3 systems）

○

○

○

○

○

○

Cold shutdown
achieved as
emergency DG andsea water pumpfunctioned eventhough external
power lost.
Important to notice
DG easily lose its
function as its sea
water pump is very
weak even to small
tsunami as this.

Turbine driven
As one DG and all
auxiliary sea water the external powers
cooling system lost lost, power supply
due toto emergency M/Csubmergence. Cold was lost, making
shutdown achieved one set of
by RHR after
emergency coolingdepressurization
function lost. 2
and cool-down by days later cold
RCIC/MUWC/SR shutdown achieved
V.
with recovered
external power.
Important to notice
DG easily lose its
function as its sea
water pump is very
weak even to small
tsunami.

Even if external
power is lost, aslong as power onsite is available,
there is no
problem.

Even if external
power is lost, aslong as power onsite is available,
there is no
problem.

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