Extremely Confidential

What should we learn from the severe accident at
the Fukushima Dai-ichi Nuclear Power Plant?

Interim Report Summary
BWR- Team H2O Project -Revised on December, 21st, 2011
1
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Fukushima Dai-ichi, lessons learned … Summary

Extremely Confidential

The biggest lesson is not the underestimation of the tsunami risk, but the lackof design philosophy to prevent any grave accidents from any threats.
Extracted from Nuclear Safety Commission of Japan’s Design Guidelines (Supervised by Cabinet Office Nuclear Safety Commission Secretariat)
Part 1 Safety Review Guideline No 27: (Design) In case of power loss:● There is no need to consider long-period loss of AC power, since we can expect swift restoration of the transmission line or restoration of power
through the emergency AC power supply system.
●

If the system structure or operational method (i.e. constant backup) of the emergency AC power-supply is deemed highly reliable, then there is no need to take
into account any scenario of a complete AC power blackout in the design of the plant.

Extracted from Additional Report of Japanese Government to IAEA (Second Report)

September 2011 Nuclear Disaster Response Headquarters●(First group of lessons learned) The tsunami damage to the plant which is the cause of the accident, occurred due to an underestimation of the height andfrequency of the tidal waves, and that countermeasures against large scale tsunami impacts were insufficient.

●

The Central Disaster Prevention Council, in regards to the prevention plan for tsunami disaster, proposed fundamental ideas such as to pursue
countermeasures against tsunami by anticipating two categories, the maximum size and the frequent size.
The Nuclear and Industrial Safety Agency started deliberating on design standards for anticipating appropriate height and taking into account theperiod and frequency of recurrence.

United Nations’ comment on the Fukushima Dai-ichi nuclear accident (Mainichi Newspaper website, September 15, 2011)● On September 14th, the UN presented a Summary Report on Nuclear Safety-Security regarding the impact of the Fukushima Dai-ichi Nuclear Plant Accident. The UN
criticized Japan for being “too modest” in its assumptions of such a disaster and severe accidents, and commented that they were troubled by the safety
standards and international emergency crisis response, which were at that point recognized as the international standard.

● In the report, it stated that “Japan underestimated the possible threats. And all nuclear power plants globally must review their risk assessments
against severe accidents, and that risk of nuclear power plant accidents must be eliminated through experience and utilization of the latest technologies.

No matter how high we set the estimation, there will always be a possibilityof an event that exceeds it.

2

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Summary

Extremely Confidential

Safety design for nuclear reactors in the world had shared common design philosophy– No fundamental question against it had ever been raised in the past.
● No countermeasure exists for events● 72 Safety Regulations Defined by theUnited States Atomic Energy Commission- Later became the foundation for NRC regulation.
- Later adopted by other G5 countries.
- Products introduced to Japan through full-turnkey
projects.

● Probability approach applied by Prof.
Rasmussen et al. at MIT- Severe accidents and natural phenomena withprobability of occurrence lower than a specific value,
have little effect and risk to the safety of the nuclear
reactor and are insignificant enough to ignore.

out of scope.
- Large scale tsunami beyond expectation had hit.
- Complete power loss was not assumed.
- Almost all safety devices and ECCS’s assumed
that power supply is available.

● Probability theory should not be
brought to use on events that have anenormous impact to society.
- Even if the probability is insignificantly low, if
the impact is enormous, the risk is also enormous.
- Probability % (miniscule) ×Impact (∞) ＝ ∞That is why we need to re-examine the design philosophy – the problem does not lay onlyin the design conditions such as the ‘estimation of scale’ or the ‘height of the tsunami’.

3

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Extremely Confidential

Fukushima Dai-ichi, lesson learned - Summary

Specifically, it’s important for us to humbly accept the following two points.
1. The design philosophy itself was flawed.
・

After what happened in the Fukushima Dai-ichi Plant, we should stop debating safety issues focusing on“assumptions on the scale of events” such as the height of the tsunami or the magnitude of the earthquake.

・The core design philosophy should be “to maintain power supply and cooling functions on the reactor core, nomatter what happens, and how to achieve this.”

2. The last strong hold “primary containment vessel myth” has been busted.
・

Until now, there was a belief that “even in an unforeseen event to the reactor core, the containment vessel willcontain the radioactive material and will be guaranteed to prevent it from leaking” (= containment vessel myth).

・However, in Fukushima Dai-ichi the core melted down and the molten nuclear fuel rods accumulated at thebottom of the pressure vessel. Then the molten fuel breached through the base of the pressure vessel, and melted
through the bottom of the containment vessel, resulting in the leakage of a large amount of radioactively
contaminated water and gas outside the containment vessel.

・

Furthermore, we have to say that all the operating reactors in Fukushima Dai-ichi, reactor No.1, No.2, and No.3,
suffered meltdown and significant damage to their primary containment vessels.

・This means that, in Fukushima Dai-ichi, the containment vessel failed as the “last line of defense.”
4
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Summary

Extremely Confidential

The biggest concern in the design (recriticality and LOCA) did NOT occur. Instead, thereactor fell into an unexpected loop after meltdown, resulting in massive hydrogen
explosion and leakage of radiation to the external environment.

● The biggest concern in the design of the nuclear reactor was recriticality and pipeline rupture (LOCA:
Loss of Coolant Accident).
- It was feared that a breach of the molten nuclear fuel rods into the containment vessel would result in power excursion
followed by a huge explosion, spreading radiation across the environment.
- It was also feared that an event, such as a major earthquake, would cause a pipeline rupture to the core reactor’s coolant
circulation loop.
● In order to prevent this, the nuclear reactors were designed to "shutdown", "cool", and "contain“.
- In case of emergency, the nuclear reactor will be scrammed (emergency shutdown).
- After the scram, decay heat removal will be constantly implemented to achieve cold shutdown (cool).
- Even if cold shutdown is failed, the containment vessel will prevent radioactive material from leaking outside with its 2
meter-thick concrete walls (contain).
● All reactors that suffered meltdown in Fukushima Dai-ichi (reactors 1-3) did not result in nuclear
excursion. Why?
- In the process of the meltdown, the boron carbide of the control rods, inserted during the scram, melted and mixed into
the fuel. This alleviated the nuclear reaction. Furthermore, the fuel rods that melted through the reactor fell and spread out
at the bottom of the wide container. Our theory is that this condition also contributed to the prevention of recriticality.
● However, the meltdown caused a massive amount of hydrogen and fission gas to leak from thecontainment vessel out into the reactor building, resulting in a hydrogen explosion. This event was notconsidered in the design of containment vessel.

● Therefore, the containment vessel was not able to ‘contain’ hydrogen and radiation from leaking out.

5

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Summary

Extremely Confidential

In Fukushima Dai-ichi reactor 1, not even one of the emergency devices worked during
the incident (which mostly can be said also with reactors 2, 3 and 4) .
Reactor 1

Countermeasures in designPowersupplyvehicleBackup power (emergency
generator, batteries)
Backup coolant

HPCI /
HPCS● Countermeasures tomitigate accidents・・Emergency Core Cooling
System (IC, RCIC, HPCI,
boron injection, etc.).
Containment vessel vent.

Containment vessel (2mthick concrete, and 3cm thickmetal plate. (100%guaranteed containment inany situation.)△
Only 1 / 5 good

×

○

×

○

All lost from the tsunami

2 / 2 good

All lost fromthe tsunami

4 / 4 good×
Only unit lost in explosion during an attempt to connect it to No.1

××

Failed to function

After DCpower depleted

×

×

Failed after operating(Reactor 2, failed after 3
days)

After DCpower depleted

×

CCSW /
RSW /
RHRS
etc.

×

×Reactor 5○Reactor 6

×FP pump did not work

MUWC /
MUWP

None
functioned

×Reactor 5○Reactor 6

Due to power loss

FP○
Used to run sea
water pump－
Coolant was not in use

×

CRD

None
functioned－
Coolant was not in use

Due to power loss

Low Pressure
Coolingsaline pump

・×
All lost from the tsunami

SLC

Low Pressure
Cooling ECCS,
etc● In case of core
meltdown (Last lineof defense)

IC /
RCIC

Reactor 5 & 6Power loss

×Reactor 5○Reactor 6

×○Power supply and motor flooded

Power supplied×△Power supply and motors flooded by the tsunami

RHT type partiallyfunctioning. Later
repaired.

Reactor No.1, 3, and 4 = Hydrogen explosion
No.2 = Damaged containment vessel

Nonefunctioned● ●Precondition: Power supply available
Design: Hydrogen explosion out of scope・Countermeasures toprevent accidents
High Pressure Cooling ECCS, etc

・

Power

●

Reactor 4

All 6 lines lost from the earthquake

Emergency
generator
DC power
supplyReactor 3

×External
power
supply● Major earthquake⇒ Scram (Emergency shutdown).
All scrammed successfully inFukushima Dai-ichi, Dai-ni,
Onagawa, Tokai Dai-ni.

Reactor 2

All leaked
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The reactor went into an unexpected loop (not part of the design), which probability theory6
neglected, making itself incapable of preventing the meltdown and hydrogen explosion.

Lessons learned from Fukushima Dai-ichi…Summary

Extremely Confidential

Safety design of both the power supply and ultimate heat-sink
was too focused on multiplicity, and lacked diversity.
In Fukushima Dai-ichi● Reactor No. 1・・All of the two DC power sources (batteries) wereplaced in the basement of the turbine building.
2 emergency generators (DG) were:- both placed in the basement of the turbine building.
- both seawater cooling type, so their cooling systems
were all placed at the sea side.

● Similar (sets of) safety measures were implemented at
the other reactors as well.

・Placed in the same area

・

Equipment with same
specifications

・

Operated from the same
power source

・The same above applies toother plants● All failed to function for the “samereason”.
● Without diversification, it will bedifficult to eliminate risks, even if
the number of measures are
increased.
7
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Lessons learned from Fukushima Dai-ichi…Summary

Extremely Confidential

The fundamental safety philosophy should be that “power, cooling function, and water
sources must be secured in any situation”. The safety principles should have 3 layers,
normal, emergency, and extreme emergency.
Normal
●
・
・
・

Power
External power supply
Backup generator (DG)
DC power supply (battery)● Cooling function・ High-pressure coolant system(RCIC, HPCI etc.)
・ Ventilation
・ Low-pressure coolant system(RHR etc.)

Extreme Emergency

Emergency● Secure water and power bycreating seawater intake tunnel,
and connecting it to a verticalpipeline from a power hub set
on an elevated area (see page 9).
● In case the regular measures fail,on-site emergency power andcooling systems work.
- Backup battery- Power supply vehicle (AC&DC)
- Emergency DG vehicle- Cable, Power panel, etc.
- Water pump, etc.
● Executed by the electric powercompany.

Can use computer simulation● Supply power from off-site byhelicopters etc.
● Supply water from a nearby
water source such as a river,lake, pond, etc.
● Collaboration by different
parties (power company,
government, and Self Defense
Forces, etc. )- Secure access route to theplant, etc.

Diversity and multiplicity● Countermeasures withdifferent principles(diversity)● Increase number ofcountermeasures(multiplicity)● Hot standby and cold
standby (Speed)● Regular / Backup (role)● On-site and off-site(location)● Electric power company
and its alliance withgovernment (Mainresponsibility)

Difficult to simulate
Characteristic

Hot standby

Cold standby (on-site)

Cold standby (off-site)
Speed

Built-in as permanent system

Ready to be plugged in (on-site)
On-siteReady to be plugged in (off-site)

Built-in or not

Off-site
Location

Power company

Power company + Government, etc.

Main responsibility

8

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Lessons learned from Fukushima Dai-ichi…Summary

Extremely Confidential

Example of emergency countermeasure: Create seawater intake tunnel leading to themountain for sufficient elevation. Plug in on-site emergency pumps and batteries toprovide cooling function.

Nuclear Reactor Building

Turbine Building
Seawater heat exchanger building
Door

Door
Door

Seawater

Reference Plane

Pump

O.P.
Seawall
Inlet Channel● Create a tunnel to draw
in seawater.

● Build a verticalpipeline for drawing
coolant water to a
sufficiently high level.

● Connect pump, powerhub, and power in caseof emergency

If required, transport necessary equipment (power sources, pumps, etc.), by helicopter tothe inlet (in case of extreme emergency)
9
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Lessons learned from Fukushima Dai-ichi…Summary

Extremely Confidential

Lessons learned from Fukushima Dai-ichi: Events overwhelmingly beyond the design
philosophy had occurred.
● Ordeals far beyond the design philosophy of the nuclear reactor- Long-term power outage (AC&DC).
- Without the cooling system, the core reactor started meltdown within an extremely short period of time.
- Zirconium oxidation caused hydrogen buildup.
- No system to vent the hydrogen resulted in a massive explosion.

● None of the emergency safety devices functioned (all due to prolonged power loss)- IC，ECCS, boric acid insertion, emergency gas treatment.

● Even with such a strong earthquake and tsunami, cold-shutdown could have beenachieved if just one emergency power supply was secured- Fukushima Dai-ichi Reactors 5 and 6 (only one backup generator for the cooling system was working)- Fukushima Dai-ni Reactors 1 – 4 (2 units for Reactor 3, and 1 unit backup generator for Reactor 4 were working)● Major events that hindered recovery action on site, or significantly damaged functionsof the reactor- Critical devices were stored in the basements and completely flooded.
・・ Emergency generators (AC)・・ Batteries (DC)- Cooling system pumps and motors at the shoreline were damaged or submerged by the tsunami.
- Unable to secure coolant for the water cooling emergency generators.
- Unable to control ventilation from the outside.
- Power panels for connecting external power were flooded.
- Difficulty in connecting power vehicles to the panels, most of which were submerged and not functioning.

10

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Lessons learned from Fukushima Dai-ichi…Design Philosophy…

Extremely Confidential

Ordeal far beyond the design philosophy of the nuclear reactor – Events totally unexpectedin the original design, or events expected but on an unforeseeable scale have occurred.
Crucial Events
at Fukushima Dai-ichi No. 1 – 4

Design Philosophy

Reality

Implications

Prolonged outage of・ Even if station-blackout occurs, power can be quickly
restored before causing any serious problems.
・ The emergency DG can be used as backup until
external power is restored.

・ External AC power supply and emergency DG
were not restored before the hydrogen
explosion.

・ AC power shortage lasted
longer than what wasestimated in the design.

all DC and AC power・ DC power will last for at least 8 hours.
・ Even if DC power drains down, it can be extended byrecharging from AC power source.

With complete loss ofcooling functions,core meltdown
occurred within a very
short period of time.

Zirconium oxidation
built up massivehydrogen.

・ The core reactor’s high pressure cooling function isrun by DC power.
・ DC power will not drain right away.
・ Thus, even if station-blackout occurs, the reactor’swater level, temperature, and pressure can becontrolled with the high pressure cooling system until
AC power is restored.
・ Hydrogen can be brought down below the
inflammable level by injecting nitrogen in thecontainment vessel and activating the flammability
control system.
・ Radioactive materials can be contained within thevessel even while operating ventilation.

No system to release
the hydrogen, which
resulted in a massive
explosion.

・ Therefore, hydrogen will not leak into the reactor
building nor accumulate. If ever there is a leak,
flammability control system can be applied.
・ This prevents hydrogen explosion caused by leak to
the reactor building.

・ Almost all DC power was submerged by thetsunami.
・ The flooded DC batteries were un-rechargeable.
・ DC power supply drained instantly, and thehigh pressure cooling system stopped working
simultaneously (Reactor 1).
・ Water level of the nuclear reactor dropped, andcore meltdown occurred in a very short time.
・ Although the timing of the fuel damage waspredicted, power and pumps were not restoredin time.
・ Core damage caused hydrogen buildup.
・ Hydrogen leaked into the containment vessel
through the Safety Relief Valve (SRV).
・ Increased pressure and temperature in thecontainment vessel caused the hydrogen to leakinto the reactor building through the vent line,
and accumulated in the upper floor.
Flammability control system did not work.
・ The hydrogen level reached the combustion
threshold and resulted in a massive explosion.
・ On-site personnel were not aware of the risksof hydrogen explosion.

・ Instant loss of all DC power
supply from the flood was notexpected.
・ Loss of power and cooling
function lasted longer than
anticipated in the design.
・ No manual to restore powerand cooling function underharsh conditions, such as incomplete darkness and amid
rubble.
・ Hydrogen leak to the reactor
building and explosion were
not considered in the design.
・Thus, no hydrogen detection
system in the building.
・No system to release thehydrogen outside.
・No manual to deal with thistype of hydrogen explosion.
11

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Lessons learned from Fukushima Dai-ichi…Design Philosophy…Power loss…

Extremely Confidential

Long-term power outage (DC&AC) occurred – While design philosophy assumed “in caseof Station Blackout, AC power would be quickly restored, and DC will last for at least 8hours”.
Fukushima
Dai-ichiReactor 1

Fukushima
Dai-ichiReactor 2

Fukushima
Dai-ichiReactor 3

・
Restorationof external
power

Tokai Dai-ni

×All 6 lines were lost from the earthquake

Only 1/4 lines
workedOnly 1/5 lines
workedAll 2 lines lost fromthe earthquake△○
・ Reactor 1 & 3: allworking・ Reactor 2: 1/3
working×△

Lost all from the tsunami

Only 1/5 wasworking・ Reactors 1 & 2:
none worked
・ Reactor 3: 2/3
Reactor 4: 1/3
worked○4/4 working○
8/8 working○
Used to power
sea-line pump○
Power partiallyrestored by power
supply vehicle○
2/2 working

×
Lost all fromthe tsunami

×・

Onagawa
Reactors 1 - 3△

Lost all from the tsunamiPowersupplyvehicleFukushima Dai-ni
Reactors 1 – 4△

×

DC power
supplyFukushima Daiichi
Reactors 5&6

×External
AC power

Backupdieselgenerator

Fukushima
Dai-ichiReactor 4

Reactor 2: Planned to use the power supply vehicle but it wasdestroyed by explosion in Reactor 1.
Reactors 1, 3 and 4: Response was slow due to search for usable
power panels and installing of cables to the available power panels.

×
Not restored before the hydrogen explosion

×
Not restored
before cold
shutdown○
6/6 working○
2/2 working－
Not required since external power supply or
emergency generator was working.

－At least one external power source wasavailable right after the earthquake andTsunami.

Power loss lasted longer than expected in the design○
・ 2/3 working○
154kV backup
power restored on
March 13 at 19:37.

12

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Lessons learned from Fukushima Dai-ichi…Design Philosophy…Cooling System…

Extremely Confidential

At Fukushima Dai-ichi Reactor 1, complete loss of all coolant systems, due to total power
loss, had rapidly led to core-meltdown. Core damage is estimated to have started 2 to 3
hours after Tsunami.
Loss of cooling system and occurrence of core meltdown
Dai-ichiReactor 1

Dai-ichiReactor 2

Dai-ichiReactor 3

××

Malfunction

After DCpower
drained

HPCI /
HPCS

High Pressure Cooling××

Worked but later
malfunctioned(Reactor 2: 3 days after)

After DCpower
drainedIC /RCIC

Dai-ichiReactor 4

Dai-ichiReactor 5&6－
In cold shutdown－
In cold shutdown

Fukushima
Dai-niOnagawa×Rctr 1&2:

×Rcr2

Flooded andlost.
○Rctr 3&4

○Rctr 1.3○

Fukushima Dai-ichi Reactor 1: Total loss of cooling function
Tokai
Dai-nicondensate watertransfer pumpDD fire pump○With fire truck

Filtered water tank○(to be verified)

海

condensate water tank

Alternative
water

Containment vessel
Pressure tank

Main Steam Release Safety Valve (SRV)
Driver air

×

SLC System

×Rctr 5Due to power loss

○Rctr 6××Rctr 5

CRD System○

D / W vent○(to be verified)Electro magnetic
valve

○

Containment
vessel vent○(to be verified)

MO
(AC)

Exhaust pipe

Low Pressure Cooling×FP

FP pump not working

××Rctr 5

Power loss

○Rctr 6○△
(to be verified)

Driver air

Manual handle○Rctr6

Due to power loss

MO
MO
(DC)
(AC)
MO
MO
(DC)
(AC)

AO

Electro magneticvalve

圧力抑制室 (S /C)

AO

Rapture disk

S / C vent○Powersupplied×

MUWC /
MUWP

Power supply and motor flooded

LPCS
seawater pumpCore damage start(Analysis)△

Seawater cooling type power supply and motor flooded

RHR
partiallyfunctioned,
then restored

3 / 11
18:46

3 / 14
19:46

3 / 13
8:46

Hydrogen Explosion○(to be verified)

放水口へ
From
海 water inlet

×

CCSW / RSW/ RHRS etc.

○

On halt
Reactor 4 hydrogen
explosion(Backflow from Rctr 3)△○
Partially flooded

Lost except
Rctr 3 (nopower &
motor)
Operating ＝＞ cold shutdown(or damage)Core was damaged a few hours after the loss of cooling
functions followed by exposure of fuel rods.

SHC pump

Supporting
saline pumpCore spraypump (CS)

ＩＣ

HPCI

● Dai-ichi Reactor 1: All cooling functions
were lost simultaneously.
● No other option but to supply water to thereactor with only one fire truck.
13
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Lessons learned from Fukushima Dai-ichi…Design Philosophy…Hydrogen explosion…

Extremely Confidential

In reactor 1 with no coolant functionality, core meltdown caused the cladding tube
around the fuel rods to oxidize and built up a massive amount of hydrogen.
Mechanism of hydrogen generation● Without power and cooling, the core’s temperature and pressure surged. This
lowered the water level in the core and eventually caused the fuel rods to be
exposed above the coolant water.
Zirconium alloy

Hydrogengenerated● As the temperature in the core increased, the cladding tube around the fuel rods
(zirconium alloy) started melting and oxidizing at approximately 900℃, whichraised core temperature further.

Melted fuelH2

● The chemical reaction between the molten cladding tubes (zirconium) andoxygen in the steam in the pressure vessel produced a massive amount ofhydrogen (zirconium-water reaction).
● According to TEPCO’s simulation, in Reactors 1, 2 and 3, with the water level
down and the fuel rods exposed, core damage (melting of fuel) possibly
started in about 2 hours after the exposure of the fuel rods.

図出典： 徹底解剖 東日本大震災 (双葉社)

Simulated time to core damage(From the timing of Fukushima Dai-ichi Reactor 1
Reactor 2
earthquake) (If water level is below the fuel) (If data of water level is correct)

Reactor 3
Reactor 2(If water level is below the fuel) (If data of water level is correct)

Reactor 3(If water level is below the fuel)Approx. 3 hrs
・March 11 17:46

Approx. 75 hrs
・March 14 17:46

Approx. 75 hrs
・ March 14 17:46

Approx. 40 hrs
・ March 13 06:46

Approx. 40 hrs
・March 13 06:46

Core damage
started:Approx. 4 hrs
・March 11 18:46

Approx. 77 hrs
・ March 14 19:46

Approx. 77 hrs
・March 14 19:46

Approx. 42 hrs
・March 13 08:46

Approx. 42 hrs
・ March 13 08:46

Damage to containment
vessel occurred:

Approx. 15 hrs
・March 12 05:46

No damage

Approx. 109 hrs
・March 16 03:46

No damage

Approx. 66 hrs
・ March 14 08:46

Core exposure started:

Note) Source May 23, 2011 Tokyo Electric Power Company Corp. "“Analysis and effect evaluation of the records on operations and accidents at Fukushima Dai-ichi Nuclear Power Plant in
Tohoku Region Pacific Coast Earthquake”
・Date of analysis: May 16, 2011
・
Method： Used the gathered information on condition of the equipment and plant operation when the earthquake first occurred as input for simulation information, and analyzed.
・Software： Accident Analysis Code (MAAP＝Modular Accident Analysis Program)
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14Lessons Learned from Fukushima Dai-ichi…Design philosophy…Hydrogen explosion…

Extremely Confidential

The reactor building had no system to “detect” or “release(*)” hydrogen, resulting in a
massive explosion. ※)Emergency gas treatment system did not function because of the power outage
Reactor No.1 (East side)

Reactor No. 3 (East side)

Reactor No. 4 (East side)

Hydrogen built up
in the 5th floor

Hydrogen built up in the 5th &partially in the 4th floor (north-east)

Hydrogen built up in the
5th & partially in the 4th, floor (east west)● Leak path-2 (Reactors 1&3): It is also possible that high- ● Leak path (Reactor 4) : It is estimated hydrogen produced at
Reactor 3 back-flowed into reactor 4 through connecting pipes
pressure & -temperature gas passed through vent lines andused for the emergency gas processing system.
damaged the pipes and valves during the ventilation of the
4号炉原子炉建屋
PCV, creating gaps for the hydrogen to leak through.

● Leak path-1 (Reactors 1&3): It is estimated thehydrogen leaked into the reactor building throughgaps in the connections and piping (hatch, drywellflange, electric penetration).
原子炉建屋

原子炉建屋

５階

主排気筒

排気ダクト→

５Ｆ

5階南側排気ダクト
4階西側排気ダクト

OP.39920
燃料貯蔵プール リアクターキャビティ 機器仮置プール
↓
↓
↓

４Ｆ

5F

ドライウェルフランジ

４階

4F

207

３Ｆ
HVE3-1A

OP.26900

AO

AO

208

GD

↑3号機 emergency gas process-----↓4号機

AO

BF3

BF3

3F

-4

-2

電気ペネトレーション：モジュール型：キャニスタ型

Hydrogenback flow from
Reactor 3

4階東側排気ダクト

OP.32300
AO

３階

排
気
塔

GD

２階

２Ｆ
AO

OP.18700

バグフィルターAO

BF3

HVE3-1B

BF3
-5A

SGTS

-5B

A
O

OP.16780
OP.16400
OP.15300

ハッチ

AO
AO
漏洩ガス流
BF3

１階

AO

SGTS

AOC

GD

BF3
-7

186

2F

SGTS
SGTS

AO

排風機 AO

AO

AO

GL

A
O

AO

１Ｆ

OP.14688

AO

back flow gas
排風機-6emergency gas process

OP.10200

ＳＧＴＳ

AO

× BF3 -14

電気ペネト
レーション

原子炉格納容器< Leak path from containment vessel (estimated) >

1F

AO
BF3

AO

-17

BF3

×

AOC
187

AO
GD

BF3
-9

-8

AO

AO

205

206

損傷の可能性が考えられる箇所
の例

ＳＧＴＳ

ＭO
２7１

15
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Lessons Learned from Fukushima Dai-ichi…Importance of power supplies…

Extremely Confidential

Even with such a strong earthquake and tsunami, cold-shutdown could have beenachieved if even a single emergency power supply were secured; Fukushima Dai-ichi(Rctrs 5 & 6), Tokai Dai-ni, Fukushima Dai-ni, etc.

These reactors lost almost all external power, but were able to achieve cold shutdown with thesurviving (one or two) emergency generators. (Note: Frontline (RHR pump) has to be working as well)
Fukushima Daiichi
Reactor 1

Fukushima
Dai-ichiReactor 2

Fukushima
Dai-ichiReactor 3

LPCS(MUWC/MUWP,
etc.)
LPCS seawater
pump(CCSW/RSW/R
HRS, etc.)

Fukushima Dai-ni
Reactors 1 - 4

Onagawa
Reactors 1 - 3

Tokai Dai-ni

△

△

×

Lost all 6 lines from the earthquake

Only 1/4 lines
Working

Only 1/5 working

Both lines lost inearthquake○
・ Reactors 1 & 3: allworking・ Reactor 2: 1/3
working×△△

Lost all from the tsunami

Only 1/5
Working(flex)

・ Reactors 1 & 2: Noneworking
・ Rector 3: 2/3 working
・ Reactor 4: 1/3
working○
4/4 working○
８/８ working

Emergency
generator

HPCS(IC/RCIC, etc.)

Fukushima Daiichi
Reactors 5 & 6×External AC
power supply

DC power
supply(A type, B type)

Fukushima
Dai-ichiReactor 4○
2/2 working

×
Lost all from the tsunami

×○
2/3 working○
6/6 working○
2/2 working

Lost all fromthe tsunami

××

Malfunctioned after a while

Stopped after
DC powerdrained－On halt○
Shared power
supply×Power outage

○

○

×

△

seawater power supply & motor flooded by tsunami

None working except
Reactor 3: (power &motor flooded)Core damage / Hydrogen explosion (or damage)○
All working except Onagawa Reactor 2○(Needs to be verified)○Partially flooded

Cold shutdown achieved○
Partially flooded

16

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Lessons Learned from Fukushima Dai-ichi…Importance of power supplies…

Extremely Confidential(Continued…) Chronology to cold shutdown or hydrogen explosion.
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)×○(2 systems)

××Earthquake occurred (14:46)

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

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

In operation

In operation

In operation

In operation

×○(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

○(2 systems)○(1/3 units)

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)

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)

RCIC manuallyactivated (15:26)
RCIC manuallyactivated (14:59)
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)

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

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

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： 15:27／2nd wave:
15:35)RCIC activated (16:03)

Water injection begun(MUWC system 22:53)

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

RCIC manually stopped(23:11)

RHR pump manuallyactivated (SHC mode
23:46)

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

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

Tsunami hit (1st wave：15:32)

Core depressurized(SRV operation
approx. 16:40)

Core depressurized(SRV operation 21:52)

RCIC manuallyactivated (15:36)

Spent fuel pool cooling (FPC
pump manually activated
20:29)RCIC manually stopped(21:45)
Water injection to nuclear
reactor begun (MUWC 21:54)

RHR pump activated(SHC mode 23:51)

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

Hydrogen
explosion(15:36)

Electrical supply vehicle
damaged (15:36)

RCIC stopped (11:36)

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

Water injection begun(MUWC system 0:00)

HPCI activated (12:35)

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

Nuclear reactor rapid
depressurization begun (3:50)

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

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

2011/3/13

RHR manually activated (SHC
cooling mode 2:39)

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

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)

PCV pressure resistant ventline structure completed(12:13)

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

S/C cooling stopped (MUWC
7:45)

S/C cooling stopped (MUWP
7:52)

Cold shutdown (12:15)

PCV pressure resistant vent line
structure complete(11:52)

PCV pressure resistant ventline structure completed(18:30)

PCV pressure resistant ventline structure completed(10:58)

Cold shutdown (0:58)

Nuclear reactor scram/reset(4:49)

Cold shutdown (1:17)

RCIC manually stopped(13:11)transition to HPCS

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 acid9:25)
Power supply begun from Unit
6 DG (MUWC system. 18:29)

SC vent AO valve (large
valve) opened (12:30)

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

Supplemental external power
recovered (19:37)

2011/3/14
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)

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

17
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Lessons Learned from Fukushima Dai-ichi…Placement…

Extremely Confidential

Critical devices, such as emergency power supplies (AC) and batteries (DC), were stored inbasements and completely flooded.
● The greater the height difference between the tsunami and the altitude of the plant, the greater the damage=> Dai-ichi No 1-4: 5.5m, No 5, 6: 1.5m. Onagawa: 0m. Tokai Dai-ni: -2.6m● Those power supplies placed in areas much lower than the tsunami crest were disabled.
Dai-ichi Rctr1

Reactor 2

Height of flood

Reactor 3

Reactors 5 & 6

Fukushima Dai-ni

Onagawa

Tokai Dai-ni

O.P.aprx14.5m

O.P.aprx14.5m

O.P.aprx13m

H.P.6.3ｍ(T.P.= O.P.+0.727ｍ)(T.P.=O.P.+0.727ｍ)(T.P.=O.P.+0.74ｍ)(T.P.= H.P.0.89m)

O.P.13m

O.P.12m

O.P.13.8m

H.P.8.9m

O.P.1.9m(A)Reactor 5

O.P.0m

O.P.0.5m(No.1 A/B)

O.P.10.2m(B)O.P.4.9m(A)/(B)

H.P.1.6ｍ(A/B/H)(Air cool)

Reactor 6

O.P. 15.5m(Main building area)(T.P. =

Altitude (Mainbuilding)
Emergency
generator
elevation

Reactor 4

O.P.+0.727ｍ)

O.P.10m

O.P.4.9m(A)O.P.2ｍ(B)O.P.1.9m(A)O.P.10.2m(B)(Air cool)

O.P.1.9m(A/B)(No. 1～4 A/B/H)

O.P.14ｍ(No. 2/3 A/B/H)

O.P.5.8m(A)/(H)
O.P.

13.2m(B)(Air cool, survived)

DC motherboard elevation(Ａ) and (B) type

Turbinebuilding B1
O.P.4.9m

Emergency
generator lost?

×

×

×

×

Lost from flood

A: Lost from flood
B: Power panel
lost from flood

Lost from flood

A: Lost from flood
B: Power panel lostfrom flood○×DC power
supply lost?
Note

Same
O.P.1.9m

Same
O.P.6.5m

×Malfunction from flood

Same
O.P.1.9m

Same (No. 5 &6)
O.P.9.5m

Control bldg
2F(No. 1 & 2)
Control bldg
1F(No. 3 & 4)
O.P.18m(1/no. 2A/B)
O.P.12.2m(No3/4 A/B)○○

Reactor 6: 1 unit OK

2 units from Reactor 3,
2 units from Reactor 4 OK

Lost from flood

・O.P: Onahama Port Construction Reference Plane
・T.P. Tokyo bay standard sea level
Unauthorized copying or distribution of this file is prohibited. Copyright Team H2O Project all rights reserved

Control bldg 1F(No 1)
Control bldg B1F(No 2)
OuterB1F (No. 3)
O.P.9.5m (no.1A/B)
O.P.7m (no. 2A/B)
O.P.5m (No. 3A/B)○
All units from Reactors 1 & 3,
2 in Reactor 2 OK

Outer B1F
H.P.9.1m(Battery location)○
2 units OK○
Working
・O.P: Onagawa Reference Plane
・Accounted in -1m of slide-down by earthquake
・H.P: Hitachi Bay Construction Reference Plane18

Lessons Learned from Fukushima Dai-ichi…Seawater cooling system…

Extremely Confidential

On-shore motors and pumps for main cooling system malfunctioned due to tsunami – Of
13 emergency generators in Dai-ichi, all but one (air cooling type) malfunctioned. Water-cooling DG
with cooling devices at the coastal side were especially vulnerable.
Loss of functions of emergency generators
Unit 1
Electricalpanel

Emergency
ＤＧ

Fukushima Dai-ichi
Unit 3
Unit 4

Unit 2Usabil Electrical
ity panel

ＤＧ１Ａ

×

ＤＧ1Ｂ

×

Usabil Electrical
ity panel

ＤＧ２Ａ

ＤＧ３Ａ

×

×（※１） ＤＧ３Ｂ

×

×

ＤＧ２Ｂ
（Air cooling）

Usabil Electrical
ity panel

Unit 5Usabil Electrical
ity panel

ＤＧ４Ａ（Air cooling）

Usabil Electrical
ity panel

ＤＧ５Ａ（※２）××（※１） ＤＧ５Ｂ（※２）

×

×

ＤＧ４Ｂ

Unit 6

ＤＧ６Ａ
ＤＧ６Ｂ（Air cooling）

ＨＰＣＳ ＤＧ

Fukushima Dai-ni
Unit 2
Unit 3

Unit 1

UsabilityElectrical
panel

×（※2）

ＤＧ１Ａ

×

○

ＤＧ1Ｂ

×

×（※2）

ＤＧ1H

Usabil Electrical
ity panel×

Usabil Electrical
ity panel

Usabil Electrical
ity panel

Usabilit Electrical
y
panel

ＤＧ２Ａ

×（※2） ＤＧ３Ａ

×（※2） ＤＧ４Ａ

×（※2）

DG A

○

DG A

○ (non-load DG A

ＤＧ２B

×（※2） ＤＧ３Ｂ

○ ＤＧ４Ｂ

×（※2）

DG B

○

DG B (※2)× Sea water
pump stopped

ＤＧ2H

×（※2） ＤＧ3H

Seawater cooling type emergency diesel generator (D/G 10 units)
Reactor 1A・B, Reactor 2A, Reactor 3A・B, Reactor 4A, Reactor 5A&B, Reactor 6A&H
Seawaterpump
HeatexchangerAllmalfunctioned
from tsunami

Ｄ/Ｇ

Air cooling type D/G (3 units)
Reactor 2B, Reactor 4B, Reactor 6B
Ｄ/Ｇ

Coolant pumpHeat
exchanger

Atmosphere

Only reactor
6 wasworking

Fukushima Dai-ni
Seawater cooling D/G (12 units)
Reactors 1 - 4A・B・H～～
Seawater pump
Heat
Sea～ ～～～
exchanger～～○ ＤＧ4H○

Usabilit
Usabilit ElectricalElectrical panelyy panelstandby）

DG B

HPCS D/G (※ ×Sea water
HPCS D/G

2)

pump stopped

Tokai Dai-ni
Usabil Electrical
ity
panel

Usability○×Sea water
pump stopped(DGS)(standby）○(standby）○(standby）

ＤＧ２C (※2)
ＤＧ２D

○

ＤＧ２Ｈ

○

(Legend)○: Working ×: Malfunctioned*1 Power panel malfunction from flood*2 Malfunction from loss of cooling system

Emergency diesel generators at Fukushima Dai-ichi

～～
～～
Sea
～～
～～

Onagawa (Tohoku Electric Power Co)
Unit 1
Unit 2
Unit 3

Unit 4

Coolant pump

Ｄ/Ｇ

Only 3 /12
working● Total of 24 emergency generators malfunctioned. The
loss of cooling function is 1.5 times higher than lossof generator itself (= more orange than pink).
－ Flooded generator (or power panel): 9 cases (pink)－ Cooling system malfunction (motor, pump, etc.): 15 cases (orange)● This is especially so when looking at Fukushima Daiichi Reactors 5 & 6 and Dai-ni, which had relatively
little flooding in the reactor building.
－ Dai-ichi Reactors 5 & 6: 4/4 cooling systems on the coast lost.
－ Fukushima Dai-ni: 6/9 cooling systems on the coast lost.

● Emergency generators for cooling system installednear the coast are vulnerable to tsunami, even withno damage to the generator unit.
－ The only generator that survived in Fukushima Dai-ichi (Reactor 6)
was an air cooling type. It had no cooling device on the coast.

19
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Lessons Learned from Fukushima Dai-ichi…Emergency generator coolant…

Extremely Confidential

Workers were unable to secure coolant for the water-cooling type emergency generators.

Dai-ichiReactor1
Availability of
coolant for
emergency
generator

Recovery?

Dai-ichiReactor2

Dai-ichiReactor 3

Dai-ichiReactor 4

Dai-ichi Reactors 5 &6Fukushima Dai-ni

Onagawa×○○

Lost (Seawater coolant)

Only one air coolingtype unit was working(Reactor 6).

Of all 12 units, 3 units
from Reactors 3 & 4
were working.

Remaining 4 units all
failed (seawatercooling type)

Remaining 9 units
failed.
(8 units lost its
seawater coolingsystem andintermediate loop. 1
unit lost intermediate
loop)

○

○

○

Type B seawatercooling system for all
reactors restored
through maintenancecheckup, motor
replacement, andtemporary power
connection.

Flooded pumps andvalves were restored
after being inspected
and repaired in afactory. DG on
standby.

×
Unable to recover

After restoring thedamaged A typeseawater pump forreactor 6, type A
generators started
operating.

Tokai Dai-ni○
All working for
Reactors 1 & 3.

○
2 units working.
One failed.
(Seawater coolant)

2 units lost for
Reactor 2 (1 unit
intermediate loop and
Seawater coolant. 1
unit lost intermediate
loop)○
Flooded pumpinspected andrestored.
DG on standby.

Note: Precondition is that related power panels, power bus-line and other supply routes are working.

20
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Lessons Learned from Fukushima Dai-ichi…Vent operation…

Extremely Confidential

Unable to perform ventilation from the outside – Workers spent too much time preparing
the vent line and failed to execute ventilation.

Right after the tsunami, Reactor 1 lost all functions
for coolant injection and PCV ventilation...

Result of ventilation
Dai-ichiReactor 1

W/W
vent

Dai-ichiReactor 2

Dai-ichiReactor 3

Equipment

Daiichi
Rctr 4

Daiichi
Rctrs
5&6

Fukushima Daini×△

Succeededin opening
the vent
valve buthydrogen
explosion
occurredright after.

Vent line
constructed
but unable
to hold thenecessarypressure to
open
rupture disc.

Openedthe valve
once, but
could notkeep it
open.

－

－

－
Construc
ted vent
line

Constructedvent line
but could
notmaintain it.

－
PC
V
vent

－

－

○

－

×

Power &seawater lost－×

power&seawater system
lost－power&seawater systemlostfire truck

Water
suppliedthrough
RCIC and
MUWC(emergency DG
worked)condensate water feed
(FDW)

×

×
×

Make-Up Water
Condensate (MUWC)

Notes(2F1)－

×

Shutdown cooling (SHC)

Application

No power (hydraulicpump)High pressure coolant
injection (HPCI)Core spray (CS)

equi
pme
nt

×
－

Wat
er
inje
ctio
n
equi
pme
nt

△

D/W
vent

Onaga
wa,
Tokai
Dai-ni

Damagestatus－No power, motor waterS/C vent valve
Valve no: AO-1601-72

×Power loss/low airpressure

temp power

S/C vent bypass valve
Valve no: AO-1601-90

×No power/low airpressure

improvised
compressor

D/W vent valve
Valve no: AO-1601-1

×

No power/low airpressure

D/W vent bypass valve
Valve no: AO-1601-83

×No power/low air

PCV vent valve
Valve no: MO-1601-210

×Manualoperation△Used
temporary gascylinderNo power… Then tried to manually open the valve atbasement but gave up as radiation level increased.
(Later succeeded by using the improvised compressor)
Succeeded inmanual release○: Successful－: Not implemented● Was not able to operate the ventilation appropriately. On
top of power outage, multiple obstacles such as darkness,transmission problems, parameter loss, frequent aftershocks,
increasing radiation, rubble, etc., made it impossible.
Manual operation of ventilation was also extremely difficult.
● As a result, failed to operate the ventilation at the right time.

MO
210

排気筒

ラプチャーディスク
0.549MPabsで破壊（25%開）

×: Failed

AO
83

AO
1

閉

D/W最高使用圧力
0.528MPabs

ベント実施圧力0.954MPabs

閉

IAAbandoned
電磁弁
manual release
due to highradiation level IA
ボ
ン
ベ

AO
90

電磁弁

ボ
ン
ベ

RPV

D/W

AO
72

AO
213

閉

閉

21

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

Lessons Learned from Fukushima Dai-ichi…External power panel…

Extremely Confidential

Dai-ichi Reactors 1 - 4, with power panels to external power flooded, failed cold shutdown.
● Almost all of the crucial panels, such as M/C and P/C, malfunctioned in reactors 1-4 which eventually exploded.
● Especially, all of the power panels were lost at reactors 1 and 3.
Unit 1
Electricalpanel

Emergency
ＤＧ

Emergency

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）

×

×

ＤＧ１Ａ

×

○

ＤＧ1Ｂ

×

×（※2）

Usabil Electrical
ity panel

Usabil Electrical
ity panel

UsabilityElectrical
panel

ＤＧ２Ａ

×（※2） ＤＧ３Ａ

×（※2） ＤＧ４Ａ

×（※2）

DG A

○

DG A

○ (non-load DG A
standby）(standby）

ＤＧ２B

×（※2） ＤＧ３Ｂ

×（※2）

DG B

○

DG B (※2)× Sea water
pump stopped

DG B(standby）

HPCS D/G (※×Sea water

HPCS D/G

ＤＧ1H

×

ＤＧ2H

○

×（※2） ＤＧ3H

ＤＧ４Ｂ

○

ＤＧ4H

○

Usabilit
Usabilit ElectricalElectrical panel
y
y
panel

2)

pump stopped

Usability

Electricalpanel

Usability○

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

○
○
(standby）

ＤＧ２D

○

ＤＧ２Ｈ

○

×

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 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／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／Ｃ６－3H○

Ｍ／Ｃ－HPCS○×

Ｍ／Ｃ 2Ａ×

Ｍ／Ｃ ３Ａ×

Ｍ／Ｃ 4Ａ×

Ｍ／Ｃ 5Ａ×

M/C 6A-1

×

M/C 1A-1○

M/C 2A-1○

M/C 3A-1○

M/C 4A-1○

Ｍ／Ｃ６－2H
Damaged by
Ｍ／Ｃ６－2Ａ
Ｍ／Ｃ６－１Ａ ×earthquake○

Ｍ／Ｃ １Ａ○

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 2Ｂ
Ｍ／Ｃ ２SA

Ｍ／Ｃ １Ｓ×

Ｍ／Ｃ ３Ｂ×

Ｍ／Ｃ 4Ｂ××

Ｍ／Ｃ ３SA××
Ｍ／Ｃ ２SB

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 ３SB×

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
１２５ＶDC
main&transfer
bus 3Ａ
１２５ＶDC
main&transfer
bus 3Ｂ○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

DC
power

×（※2）

ＨＰＣＳ ＤＧ

Usabil Electrical
ity panel

Ｍ／Ｃ 2Ｃ

Ｍ／Ｃ １Ｂ

Normal（Air cooling）

Electrical
panel

Tokai Dai-ni

×NormalＰ／Ｃ

ＤＧ６Ｂ

UsabilityOnagawa (Tohoku Electric Power Co)
Unit 1
Unit 2
Unit 3

Unit 4

Ｍ／Ｃ １Ｃ

Ｍ／Ｃ

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 6Ａ

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 2Ｂ○○○○

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○

Sea waterＢsystem○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：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○
3/4 lines were lost due to earthquake（Tomioka line 1L only 500kV continued to receive power）

Information on DC power of system-H was omitted.

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

×
Both lines were lost due
to earthquake

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 panels22

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Lessons Learned from Fukushima Dai-ichi…Connecting power supply vehicles…

Extremely Confidential

With almost no working panels for the power supply vehicles to connect to, it was very
difficult to supply power.
Power supply vehicle arrangements● Power supply vehicle arrived right after the tsunami (High voltage vehicle)－ March 11 approx. 22:00 First group arrives with one unit.
－ March 12 approx. 01:20 4 units arrive (total 5 units)－ March 12 approx. 03:00 7 units arrive (total 12 units)● Same as above (Low voltage vehicle)－ March 11 approx. 23:30 2 units from Self Defense Force－ March 12 approx. 07:00 3 more units arrive

Difficulty with connection● Few power supply vehicles were rounded up by dawn of March 12.
● However, there was trouble connecting them as very few power panels (M/C, P/C) were working
due to tsunami as well as time was consumed in identifying working ones.
● Furthermore, factors such as rubble, aftershocks, transmission problems, insufficient heavyequipment, hindered the set-up of lines to connect vehicles.
● All the preparations made for restoring power in Fukushima Dai-ichi Reactor 2 had to start fromscratch when Reactor 1 exploded.

23
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Lessons Learned from Fukushima Dai-ichi…Countermeasure summary…

Summary of countermeasures - 1

Extremely Confidential

Specific measures/ Guidelines

Secure power (Without power supplies, cooling function to the reactor will instantly stop)
Power Supply

CoolingfunctionControl Roomfunction

Ventilation
function
Prevention against
hydrogen explosion

Disaster and accident
manual/infrastructureNote) Compared with
instructions from NISA

Secure external AC power supply● Ensure water seal and pressure resistance, or place in elevated areas.
● Improve earthquake resistance of external power supply and multiplicity of power supply routes. Allow versatility of
power within the wider region.
Secure emergency diesel generator (DG)
● Ensure water seal and pressure resistance, or place in elevated areas.
● Reinforce the capability to share DG power supplies: All DG to be shared by all reactors (i.e. multiplexing). DG at
Reactor 6 was shared with Reactor 5, but not so with Reactors 1- 4.
● Add more air-cooling and gas turbine types of DG (Only the air cool type survived as it did not need seawater pumpand circulation.)● Place gasoline and diesel tanks on elevated areas.
● Activate DG automatically during earthquake scram.
Secure AC power● Ensure water seal and pressure resistance, or place in elevated area.
● Versatile AC power supply (versatility between M/C and P/C)
● Reinforcement of power supply vehicles
・ Add on-site units, add more units, review locations
・ Add different types of vehicles: DC, AC, AC & DC mixed, with generator, with DG, etc.
● Enable air transport of power supply vehicles and other backup power supplies (set up helipad on the premises orrooftop )● Store power cables and tools for working on terminals in appropriate places.
● Set up multiple hubs for connecting power supply vehicles to power panels, and improve water resistance.
Secure DC power supply● Ensure water seal and pressure resistance, or place in elevated area.
● Upgrade DC power capacity (from 8 hours to 24 hours or above).
● Designate mobile battery vehicles in case a disaster renders the DC power supplies useless.

● Black text = exists● Red text = does not exist

24
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Lessons Learned from Fukushima Dai-ichi…Countermeasure summary…

Summary of countermeasures - 2

Power Supply

CoolingfunctionControl Roomfunction
Ventilation
function
Prevention against
hydrogen explosion

Disaster and accident
manual/infrastructureNote) Compared with
instructions from NISA
● Black text = exists● Red text = does not exist

Extremely Confidential

Specific measures/ Guidelines

Secure cooling functions (Without the cooling function, core will melt down in a matter of hours. Meltdown
triggers hydrogen buildup.)● Ensure water source: secure source and means of water supply from multiple sources such as water tanks, water
reservoir, lakes, rivers, sea, etc.
● Secure the necessary number of fire trucks and fire hoses. Set in elevated areas.
● Install multiple hubs for fire truck hoses.
● Secure water seal and pressure resistance of high- and low-pressure cooling systems, or place in elevated areas.
● Secure water seal and pressure resistance of facilities and buildings near the sea.
● Prepare motor cleaning devices and parts.
● Must have alternative core cooling system, which drives on an independent set of coolant, power, and waterinjection systems.
● Implement feed-and-breed systems via wet-well vent (to secure heat sink until cold shutdown).
● Prepare portable underwater pumps.
Monitoring of spent fuel pool
● Strengthen the system to thoroughly monitor temperature and water level (both hard and soft).
Secure control room functions● It is important to secure monitoring systems. Prepare backup batteries so that measuring instruments can bemonitored during power outage.
● Maintenance and upgrade of central control room.
● Proper storage of protective suits, masks, dosimeters, etc for workers.
Secure ventilation● Reexamine the logic of the ventilation system (its effectiveness was unclear) and design philosophy of rupture disc.
● Reconsider the location of the vent line valve (focus on operability).
● Considering the rupture disc didn’t open, review the method for opening/closing its valve (change the method).
● Consider installing multiple measures to reduce pressure within the core (consider a system that doesn’t rely on SR
valve which is run by DC power).
● Prepare temporary power source and gas tanks so that vent line can be set up swiftly during power outage.
● Prepare batteries near/in the central control room to open and close SR valve to relieve core-pressure.
25
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Lessons Learned from Fukushima Dai-ichi…Counter measure summary…

Summary of countermeasures - 3

Power Supply

CoolingfunctionControl Roomfunction

Ventilation
function
Prevention against
hydrogen explosion
Disaster and accident
manual/infrastructureNote) Compared with
instructions from NISA

Extremely Confidential

Specific measures/ Guidelines

To prevent a hydrogen explosion● Reinforce the containment vessel’s sealing functions: Reevaluate the sealing materials used for PCV head flanges,
electric cable routing, hatches, etc, and improve the resistance against high temperature and pressure.
● In case of massive hydrogen buildup, install measures to reduce its density in an enclosed space;・ Install hydrogen detectors in the enclosed space (transmit signal using own power source or by RF).
・ Ensure filling of nitrogen into the containment vessel during ventilation.
● Install canopy to ventilate hydrogen (remote control＋manual operation＋absorption filter for fission gas)
Enrich disaster and accident manual (AM)● Redesign of AM: How long (hours) should the water and power supply last? How to arrange off-site support while
supplies last? In order to achieve this, perform the following:・ Set quantitative values on how long water and power supplies will last, and create corresponding manuals.
・ Define operational manual to supply alternative power/water and equipment, and to set them up on-site in order toensure completion within specified life expectancy.
・ Implement periodic training to verify that the above tasks can be executed within the necessary period of time.
(including extreme conditions such as night time, holidays, simultaneous accidents on all reactor units, etc.)

Reinforcement of infrastructure● Assemble operators to the power plant after an earthquake, assign emergency supporting staff.
(Assemble within a specified time. Set an alternative assembly location in case of large scale disaster (i.e. - beyond
100 yd in US ))● Secure access to the plant (reinforce roads, bridges, etc.)● Improve accessibility to and from the plant in case of earthquake and tsunami:
・ Reinforce the main road (include measures against liquefaction).
・ Secure appropriate amount of heavy machinery, and drivers for clearing up rubble.
・ Secure routes suitable for earthquake and tsunami situation (Construct passage or path that will not crack orliquefy, and has no manholes.)・ Set up gasoline tanks.
● Communication among operators, restoration team, emergency response office, and central control room were cut
off. This made it impossible to report in a timely manner. Means and equipment for communication during an
emergency must be secured.

● Black text = exists● Red text = does not exist

26
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AM structure... Comments from local government…

Extremely Confidential“Regarding the reoperation of the plant, what happened at Fukushima Dai-ichi, including decision
making, has to be examined. Computer simulation that hasn’t taken this into account isunsubstantiated” – Governor of Niigata Pref(*). Izumida *) re: Another nuclear power plant location.
Governor Izumida’s comment (extracted from regular briefing on Sep 14th)●○

Q: What do you think about the government’s announcement
regarding the IAEA’s participation in the evaluation of the stress
test?
Governor: It isn’t enough. What happened in the
Fukushima Dai-ichi isn’t just about the mechanisms andequipment. The decision making mechanism must be
evaluated as well. We need to consider questions such as,
when should the decision to pour seawater have been
made? who should have made the decision? can someone
really make such a decision knowing that he/she is disposing of aplant worth hundreds of billions of yen?
Was there really nothing that could have been done to prevent therelease of a massive amount of radiation? It was pointed out in
IAEA ‘s report that the prime minister was intervening too muchwith the site. Considering this, there isn’t much point in
conducting stress test without reviewing the decision
making mechanism, like who’s responsible for what.
If you ask me if there really is any point in computer
simulations, without even verifying if there was a pipeline
rupture, that is solely based on past knowledge and perception,and then having the IAEA review it, I’d say that it may bebetter than doing nothing at all, but it’s really nothing
more than that.

What it means● Prevention measures must be made from both thetechnical and organizational aspects.
● Technical aspect: Inspect Fukushima Dai-ichi (back fromdesign philosophy), and identify lessons learned andcountermeasures.
● Organizational aspect: Establish an organization to
implement the countermeasures, and clarify therequirement for the decision-making mechanism.
・ Redesign the decision-making mechanism to prioritize preventionof recurrence as top priority.
(Head Office, Technical Support Center, Off-site Center, Central
Control Office)・ Design the organizational structure and identify the roles for the
implementation of the countermeasures (Power company, National
Government, Local Government)● Reinforce training: Practical training necessary forcountermeasures and organizations (that were
established based on the lessons learned) to beeffective.
・ Training program simulating the accident in Fukushima Dai-ichi.
・ Plan and practice program, and improve the results.
・ Case study around the world.

In addition to technical measures, accident management systems for local participation27
in terms of decision-making, organization, and training are required.
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Copyright Team H2O Project all rights reserved

AM structure…Mission…

Extremely Confidential

In order to achieve that, it is very important to incorporate the following missions in
the design of Accident Management.
Safety Priority● To protect human life and promote safety culture, create a system that prioritizes “safety of plant”
and “safety of local community” above all.
● Hydrogen explosion and radiation leaks must be prevented at all cost. (Never Fukushima again.)Real time
information
sharing NW● Provide network that allows real-time and transparent information sharing during severe accidents(or risks).
● Create a system that notify the status once the accident mode is on, and that allows information
sharing and discussion regarding the progress of the accident.

Local
participation● System that allows local bodies to share information and make decisions on the safety of the area.
● Enrich human resources of the local administration such as nuclear power specialists and consultants.
● Impel and reinforce training.

Transparent andswift decision
making● Design an organization and authority where proper and transparent governance works.
－ Plant safety: The site (plant head or shift manager) is the chief decision maker.
－ Local safety: The local government can share information from the plant in real-time
to make final decisions.
－ Decision-making process should be transparent and should not be delayed or diverted
due to external influences.

Proper training
to secure safety● To guarantee the items above, AM (accident management) procedure manual and countermeasures
have been defined appropriately.
● Select qualified personnel for executing the manual.
● Selected personnel will undergo necessary training.
● Periodic evaluation on these procedures, personnel, and training shall be conducted from a neutral
28
point of view (possibly a third party)
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AM structure…Information sharing network…

Extremely Confidential

For severe accidents that require prompt action, there needs to be a real-time networkthat enables all the stakeholders to share information and participate in discussion.
FutureCurrent situation (Article 10 In case of accident)

On-site Emergency
Headquarter(at Earthquake
shelter)● Fukushima Pref. Social Affairs & Env’t Dept,
Nuclear Power Safety Div (Governor)● Okuma-city Consumer and Env’t Protection
Div (Mayor)● Futaba-city Citizens' Livelihood Sec (Mayor)● Surrounding cities, towns, and villages● Police, fire department, coast guard

Overall Emergency
Headquarters(Power company)

Emergency
Headquarters(Central government)

Emergency
Headquarters(Prefecture)

Emergency
Headquarters(City/Town/Village)

TV conference
systemOff-site Emergency
Headquarter(at Headquarters
of TEPCO)● Nuclear Emergency Preparedness
Div of NISA at METI (Minister of METI)● Related parties of Ministry of Education● Cabinet Secretariat, Cabinet Office

Individual Plant'sCentral control room

Local Emergency
Headquarters(Earthquake shelter)

Off-site center

Confirm receipt of fax by phone
Transmit FAX● Related departments within power company
Phone callContact points indicated in Act on Special Measures Concerning Nuclear Emergency Preparedness Article 10 Section 1●

Real-time (limited): Real-time TV conference available between the●・ Dedicated line
・ Emergency power・ Countermeasuresagainst earthquake
and tsunami.
・ Network security, etc.

System that enables the network to simultaneously connects related
stakeholders and plants, and help real-time information sharing,

power plan and Head Office.

meetings, and decision making.
●Bi-directional (partial): Communication other than with government

・city/state/province of the plant.

bodies are mainly one-directional through phone, FAX and mail.
・●Limited information sharing:・Communication difficulties during power outage and transmission

Function: Share information and hold conference regarding plant status,
countermeasures, local safety, evacuation, etc.

・Let stakeholders know that AM (accident management) mode is on, and share
the progress of events.

problems.
・

Stakeholders: Plant, power company’s headquarter, government, prefecture andLocal government pointed out that information on the accident provided to・Help transparent and prompt decision-making with all the information shared.

them was insufficient (partly because they were using public lines).

・Prevent information from leaking.

29
It will be too late to consult with the head office when the accident passes a critical point.
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AM structure…Governance…

Extremely Confidential

Ensure plant safety: Front line (Plant Head and Unit Manager) shall have absolute authority, and mustgovern the plant with accident prevention and containment as top priority – equivalent toairline’s “air-traffic controller” and “pilot”, or manufacturing’s “CEO” and “Chief Engineer”.
Logistical support to the site
Power company
Head office or
central government

Head office
Emergency Headquarter
Share
information

Government

Government
Emergency Headquarter● Power plant: Decisions and actions with top priorities
on accident prevention and safety. On this issue, it
should be independent from management.

local government● Head office: Entrust the site to “plant safety”. Provides
logistical support to the plant.

Plant

Plant Head
(Earthquake shelter)
Local government

Share info on
local safety

Prefecture
Emergency Headquarter

Instructions &commands

Shift Manager(Central control room)

Power Company’s Head Office and Plant: Separation of
Safety from Business

City/Town/Village
Emergency Headquarter

Full authority over the plant's accident response
・ Undefined accident = Plant Head・ Defined accident = Shift Manager on-site

Plant Head and Shift Manager: Act as ‘Traffic Controller’and ‘Pilot’.
● Plant Head (= Traffic Controller):・ Provide instructions to the shift manager in the event
not defined in the Accident Procedure (AM Manual).
・ Has absolute authority and responsibility over the safety andaccident prevention of all reactors in the plant.
● Shift Manager (= Pilot):・ Has absolute authority over the plant’s safety on
events and operations defined in the AM manual.
・ Shares information to stakeholders when in AM mode.

In order to achieve this mission, Plant Head and Unit Managers should go throughstricter qualification and trainings, and receive appropriate rewards.

30

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AM structure…Local participation…

Extremely Confidential

We must aim for a decision-making system where the local officials can make decisions
on “the safety of the citizens” as a local autonomy.

Power company

Only in extremely severe events, thecentral government shall instruct local
governments for the interests of national
defense.
Government

Head Office orCentral Government

Government
Emergency Headquarter

Head office
Emergency Headquarter

The accident from the local government’s view point● Overwhelmed with incomplete and erroneous
information.
● Delayed information (status of the accident, evacuation, etc.)● Contents of the information were confusing.
● It was confusing who had authority to make decisions(accident response, evacuation, etc.)★ The local governments had no authority to participate indecision-making, so were positioned like “victims”.

Share info andagreements.

Share
information

Ideal role of local government

Plant

Prefecture
Plant Head
Emergency Headquarter(Earthquake shelter) Share info on
local safety
Prefecture of Power Plant

Instructions &commands

Shift Manager(Central control room)

Conference
Discussion
Decision

City/Town/Village
Emergency Headquarter

local government

Understand the situation of the accident so thatdecisions such as whether to evacuate can be made.

● Decision-making: On local safety and evacuation, the head of
local government should have full understanding of the situationand discuss with plant’s head before making any final decision.
● Training: Head of local government should receive constanttraining to develop good judgment skills.
● Information sharing: Information needed to make decisions
shall be provided directly from the plant rather than from thecentral government or head office of power company.
● Network: There is a network to conduct these missions.
● Decision standards: Basis on the roles and responsibilities of
the national and local government is explicitly defined.

( Three Mile Island accident in US: One of the reasons the powercompany was able to build a good relationship with the local
government/community was because they involved the locals in theoperations/trainings of the plant after the accident. )Principle is to “Operate the plant safely with the locals”.

31

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AM structure…CATO…

Extremely Confidential

In order to achieve that, the local government should strengthen human resources, suchas by hiring a senior officer (CATO*) with expertise on nuclear technology. (* Chief Atomic Technology
Officer)

Future direction (vision)

Mission of CATO

Local Emergency Headquarter

Prefecture
Governor

consult

Country’s
Emergency Headquarter

CATO & otherSpecialist TeamPower company’s
Emergency Headquarter

Share information,
decisions, andinstructions

Media

Local
policedepartment

Local fire
department
head office

Emergency
Headquarter ofcity/village

Other cities
andvillages

Local citizens, ships, vessels in the area, etc.

● The local governor makes overall
judgments while consulting to
CATO and others and act as acontrol tower.

Coast
Guard, etc.

● Qualifications: If the local governor deems thathe/she will have difficulty in handling issues on the
nuclear power plant accident, which require
technical knowledge and expertise, he/she should
assign a CATO, who is responsible for the technology andsafety of the nuclear power plant .
To maintain neutrality, CATO candidates should have noprevious affiliation with the power company or thegovernment.
This is only subject to areas with nuclear power plants.
● Role of CATO: To have meetings and share
information with the power company, government,
administrative agencies, emergency headquarters.
To advise to the governor.

For example, Niigata Prefecture introduced a new post, “Crisis Manager”, who manages
risks related to the nuclear power plants. - Expenses including training should be
32
shouldered by the central government.
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AM structure…AM structure…

Extremely Confidential

From now on, we need to manage accidents in 3 categories and establish its own AM
structure.
Accident Category

Accident

Examples・ Core reactor scram + external
power outage + activation of
emergency generator (DG)

Information
NW
ON

SevereAccident

Grave Accident

・ Reactor scram + complete power
outage (DG unavailable)

Responsibility of “Plant Safety”

Responsibility of “Local Safety”

・ Defined in AM = ShiftManager・ Plant shares information directlywith local government.
・ Local government makes final
decision to evacuate.
・ Central government provides
logistical support and agreement.

Ministry ofEnvironment

・ Not defined in AM = Plant
Head・ Fukushima Dai-ichi Reactor 6,
Tokai Dai-ni, etc.

Responsibility
withingovernment

ON・ Same as above

・ Same as above

Ministry ofEnvironment

ON・ Same as above

・ Central government has authority
to make decisions

Office of
Prime
Minister・ Fukushima Dai-ichi Reactor 5・ Complete loss of power andcooling function
・ Core meltdown, increasing risk ofradioactive leakage
・ Fukushima Dai-ichi Reactors 1 - 4
・ Terrorist attack

・ Central government provides
necessary support(e.g. Self Defense Force
deployment)

・ Central government, after
consulting with local government,
shall make overall decisions fornational defense/national interest.

When the situation reaches extreme level, the central government will take control
in order to protect national safety and interests.

33

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AM structure…ＧAM judgment…

Extremely Confidential

For example, as to Fukushima Dai-ichi Reactors 1 – 3, wasn’t there a need to judge thelevel and stage of accidents and determine the appropriate actions?
Form

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

Activate IC/RCICTsunami impact

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

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)○(2 systems)

Tsunami hit(1st wave： 15:27／2nd wave:
15:35)● Availability of power (External power, Emergency
DG, Battery, etc.)- Should be able to comprehend the availabilityof all power sources so that it can be checked
instantly.

Core damage begun(18:46). By simulation

Activate
HPCS

Large quantity of hydrogengenerated/accumulated● Availability of HPCS functions.
Possibility of malfunction and estimated timing.

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

HPCS
malfunction
Core damage
start

Criteria of Severe Accident (SAM) and Grave Accident(GAM) (illustration)

Hydrogen
explosion(15:36)

RCIC stopped (11:36)

Electrical supply vehicle
damaged (15:36)

HPCI activated (12:35)● Status of the core reactor and risk of meltdown
based on the overall availability and conditions of
the power and cooling functions.

2011/3/13
HPCI stopped (2:42)↓

Core exposure begun(Water level ＝TAF attained
4:15)

Mass accumulationof Hydrogen

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

Hydrogen back flew
(From Unit 3)★ Looking at the chronology of Fukushima Dai-ichi
Reactors 1 – 3, power outage + HPCS
malfunction resulted in meltdown and radioactive
leakage. (+ Hydrogen explosion on Reactors 1 &3)

Nuclear reactor
depressurized (Releasesafety valve @ 9:08)
Fresh water injection from fire
trucks begun (with boric acid
9:25)

Hydrogen explosion(Reactor 2 unknown)

SC vent AO valve (large
valve) opened (12:30)

2011/3/14

Radiation leak

: Accident stage

Fire trucks damaged (@11:01)

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

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

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

Core depressurized(SRV opened @18:00)

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

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

Hydrogen explosion(11:01)★ When expected to lose power and cooling
functions, the probability of GAM is very high.

Core damage begun(@19:46). By
simulation
Large quantity of hydrogengenerated/accumulated: Severe Accident stage

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

34

2011/3/15

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

Hydrogen explosion(6:12)

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AM structure…ＩＮＥＳ index…

Extremely Confidential

Government announced level 4 on March 12, level 5 on March 18, and level 7 on April 12.
However, were these really appropriate? (level, timing, frequency, and key message)
Facts and References● The event in Fukushima was the first to ever pass level 5 since theestablishment of the International Nuclear Event Scale (INES) in 1989. There wasno precedence of an ongoing event to be declared on such a scale.
・ Chernobyl (April 26, 1986 - Level 7) and Three Mile Island (March 28, 1979 - Level 5) werescaled in years after the events.
● On March 12 15:36, the hydrogen explosion occurred in Dai-ichi Reactor 1. At thatpoint it should have already met the criterion of level 5.
・Level 5 = Severe damage to the nuclear reactor core or radiation protection vessels. Requires
planned emergency action.
● “The primary purpose of the INES Scale is to facilitate communication andunderstanding …on the safety significance of events.”“INES is a tool for promptly communicating to the public in consistent terms thesafety significance of reported nuclear incidents….” (Extracted from official site of INES)● The “impact on people and environment” criterion in Levels 6 and 7 is highly
subject to interpretation.
・ Level 7: more than several tens of thousands of tera-becquerels (TBq) =>stochastic health effects over a wide area, perhaps involving more than one
country, long-term environmental contamination, and sheltering and evacuation isnecessary.
・ Level 6: thousands to tens of thousands of TBq => sheltering and evacuation is
likely.
・ Level 5: hundreds to thousands of TBq => Localized sheltering and/or evacuation may belikely.
● Compared to Chernobyl, the amount of radiation in Fukushima Dai-ichi is around10%.
・ Chernobyl = 5.2 million TBq, Fukushima Dai-ichi = 370,000 TBq (NISA), 630,000 TBq(NSC)

Issues and Lessons
●

●

●
●

Was it really necessary to declare the scale 3 times
while the accident was in-progress? (issue withinternational response?)
Learning from the experience in Fukushima, there needs to be
specific guideline in how to declare the scale for progressing
accidents.

In hindsight, the question remains whether the level 4
declared on March 12 23:00 was a technical mistake.
Why was level 7 declared on April 12, one month after
explosion of Dai-ichi Reactors 1 to 4, not right after three
explosions?

●

The accident was still expanding, so instead of justindicating the scale, shouldn’t it have focused on providing
more precise and clear-cut explanations regarding the“impact on people and environment”?

●

The radiation level of Fukushima does fit the level 7
criterion but in terms of “impact on people andenvironment”, which is the original purpose of thescale, the impact is much smaller than Chernobyl. It
seems that level 6 (or a level between 6 and 7) is more
appropriate in this case.

●

Further discussions should be made to review INES criteria
based on what was learned in the Fukushima Dai-ichi Accident
and aim for improvement, especially the criteria for Level 6 and
7 (or modify into detailed scale).

35
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AM structure…Message to public…

Extremely Confidential

Was the message to the public appropriate? Wasn’t there a gap between what’s stated
and what actually happened? Doesn't it add anxiety to the local and international society?
Press Conference with the Chief Cabinet Secretary (Sources from various news articles from the web; March 12 onwards)
March 12 18:00 (Reactor 1 after the explosion)・・“Does it mean there was no damage to the nuclear reactor? Has it been confirmed?” => I would like to answer that once
we have clarified the details, including final confirmation of facts and analysis of the cause.
“Does the government expect the hydrogen explosion and radiation leak?” => We are handling this matter while
expecting the worst. This accident, when it occurred, was within the scope of our expectations…. Commentsthat give out a false sense of alarm or security must not be made.

Issues & lessons learned● When should public statements
be made?
● Was the hydrogen explosion
really anticipated?

March 13 (Regarding Reactor 1 and 3)
・

・

・

・

・
・

・
・

8:00: In regards to Reactor 1, we have confirmed that the filling of seawater is working well as it would with the pump. …wecan logically conclude that the core is now filled with seawater, or at the least filled to a level that covers thefuel rods.
8:00: (regarding reactor 3) … By this ventilation and water injection with the pump, we should be able to manage,
secure and control the situation, although there will be some level of radioactive materials in the gas it will have no effecton the health, and will insure nuclear reactor safety.
8:00: “At what time will the filling of seawater end?” => Even if we’re done pouring water into the pressure tankand core reactor, we’d also like to fill-up the containment vessel …if we continue filling the pressure tank, it will
overflow, meaning the water will be going outside, so we would like to continue filling it with water.
11:00: (regarding Reactor 3) ….water pump stopped functioning… It is presumed that water level on the fuel rods dropped,
exposing the top of the fuel rods. Because of this, the safety valve of the pressure tank opened and the pressure in the nuclear
reactor dropped. Pumping of water started at 9:08. At 9:25 we mixed boric acid to increase the safety even more.
11:00 “What is the status on the exposed fuel rods in Reactor 1?” => We believe that water have been filled, so it’s nolonger exposed.
11:00: “Does it mean that core meltdown occurred in Reactor 1?” => There is a possibility. Although we can’t
confirm, since of course we can’t see inside the reactor, it is very likely so we are handling the situation with theassumption that it did occur.
11:00: “Reactor 1 exploded soon after the ventilation. What about reactor 3?” => This time we were able toproperly inject the water and to set up the vent.
11:00: “Have you already prepared what to do in case Reactor 1 can’t no longer be filled with seawater?” => We believe that,
although it was at the last moment, we were able to fill the reactor with seawater before the problem got any
bigger. For the other reactors, we’d like to do the same and be prepared at all times.

● What was the basis for the
methods used for the vent andwater injection when planningand executing it?
● Didn’t they anticipate severe
damage of pressure vessel andwater to leak to the containment
vessel?
● At this point, did they prepare
the way to restore power and tocool the core in reactor 3?
● Was the countermeasure to
explosion in reactor 3 reallyprepared?

36

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AM structure…Government safety guidelines…

Extremely Confidential

The government’s safety guideline has been incorrect – “No need to consider long-termloss of power.”
Nuclear Safety Commission’s Design Guidelines(Supervised by Cabinet Office Nuclear Safety Commission Secretariat)

Section 1: Safety Review Guideline No. 27 “In case of power loss"● Nuclear reactors and facilities should be able to safely stopand secure cooling function in case of a short-term lossof all AC power.

(Explanation)

Facts at Fukushima Dai-ichi● Transmission line was not restored
before hydrogen explosion.
● Emergency AC power supply system
malfunctioned due to the tsunami andwas not restored before the hydrogen
explosion.

● There is no need to consider long-period loss of AC power,
since we can expect swift restoration of the transmission
line or restoration of power through the emergency AC
power supply system.

● Not only the AC power, but also the
DC power supply were completely lostfor a long period.

● If the system structure or operational method (i.e. constantbackup) of the emergency AC power-supply system is deemed
highly reliable, then there is no need to take into accountany scenario of a complete AC power blackout in thedesign of the plant.

● Due to the complete loss of all AC andDC power for a long period, key
functions such as parameter-control at
the central operation room, cooling,
and water-injection were all lost.

It is necessary to verify why and who is responsible for this guideline, and completely
redesign the atomic energy administration, as known for its back-scratching structure. 37
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AM structure…On-site and off-site boundaries…

Extremely Confidential

It is imperative to provide clear safety guidelines for long-term power loss. For example, if
it is over 24 hours, off-site support shall be provided, and if within 24 hours, the on-siteteam has to deal with it.
Length of AC power outage

Guideline

Main player
Power supply

24 hours● Prepare on-site plan and safetymeasures that can prevent coredamage for at least 24 hours for any
type of power loss.

● For power loss over 24 hours, off-site
support and actions shall be made.

● Power company● Power company and central government● Secure power supply on-site for atleast 24 hours.

● Must accomplish off-site support within
24 hours.

● In US, boundary between on-site and off-site response is 72 hours for NRC and 24 hours for INPO.
● For example, USA has a special unit that is intensively trained to work in radiation-contaminated areas (e.g. Fort
Leonard Wood Chemical Biological Radioactive Unit).
● Japan should have a similar special unit as well.
38
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AM structure…Education and training…

Extremely Confidential

Future education and training should include ‘lessons learned from Fukushima Dai-ichi’.
Important items for the education and training programs (Example)● Practical training under extreme conditions such as in Fukushima Dai-ichi Reactor 1・ Complete power outage, loss of cooling function, darkness, aftershocks, high radiation, insufficientmaterials, and telecommunication problems.
・ Risk of core damage and hydrogen build-up in a couple of hours from the stop of cooling system.
・ (Furthermore) Severe accident during holidays, night, bad weather, fire, and road blocks (simultaneously).
・ Emphasis on the absolute prevention of a hydrogen explosion under any circumstances.
● Practical training to supply alternative power source and cooling system to the plant (forexample) “within 2 hours” during complete power outage
・ Prepare and store the requirements. (Define the type and quantity of power/water sources and equipments
to meet the necessary time of cooling.)
・ Actual operation to carry and set up alternative systems such as power supply, coolant, water-injection,
carry-on batteries on-site.
・ Organize and operate supply chains for emergency equipment (at the plant, at the head office, etc.)● Set specific indicators/goals/periods in each training and check its proficiency level.
・ Example: Provide X amount of power/water supply within Y hours. Complete task A within B hours, etc.
● Practical training not only for the power company, but together with the central and local
government and related stakeholders.
● Share and pass down the experience and lessons learned from Fukushima Dai-ichi with all
power companies in Japan and the world.
39
Unauthorized copying or distribution of this file is prohibited. Copyright Team H2O Project all rights reservedSources and references…

Extremely Confidential

List of the main sources and references
Tokyo Electric Power Company (from website)・
Fukushima Dai-ichi Reactors 1 – 6 plant-related parameters (water level, pressure, temperature, monitored data).
・Effect of the Tohoku earthquake and tsunami on nuclear power plant and current situation.
・Collection of reports based on provisions of Utility Industry Law Article 106, section 3. (May 16 2011)
・
Report on the responding action based on the report on the damage on power equipment in the vicinity of Fukushima Dai-ichi nuclear power
plant. (May 23 2011)
・
Analysis and evaluation based on operations and accident records in Fukushima Dai-ichi nuclear power plant during the 2011 Tohoku earthquake.
(May 23 2011)
・
Effects of the earthquake and tsunami on the Fukushima Dai-chi and Dai-ni nuclear power plants. (May 24 2011)
・
Chronology of seawater injection at Fukushima Dai-ichi nuclear power plant Reactor 1. (May 26 2011)
・
The research result on the effects of tsunami by the 2011 Tohoku earthquake to Fukushima Dai-ichi and Dai-ni nuclear power plants.
・
Recovery status on Fukushima Dai-ichi and Dai-ni nuclear power plants. (August 10, 2011)
・
Effects on the nuclear reactor facilities at Fukushima Dai-ni nuclear power plant from the 2011 Tohoku earthquake. (August 8, 2011)
・
Effects on the nuclear reactor facilities at Fukushima Dai-ichi nuclear power plant from the 2011 Tohoku earthquake. (September 9, 2011)
・
Analysis on the explosion of nuclear reactor building in Fukushima Dai-ichi nuclear power plant. (October 21, 2011)
Nuclear and Industrial Safety Agency (from website)・
Examination standards for verifying implementation of emergency safety measures. (May 6, 2011)
・
Examination standards for verifying implementation of safety measures against severe accidents. (June 18, 2011)
・
Security of external power source in nuclear power plants and reprocessing plants. (April 15, 2011)
・
Report of the Japanese Government on cabinet meeting with IAEA in regards to Nuclear Safety – The accident at Tokyo Electric Power
Company Fukushima nuclear power plant. (June 7, 2011)
・
Additional report from the Japanese government to IAEA - The accident at Tokyo Electric Power Company Fukushima nuclear power plants (2ndreport). (September 11, 2011)
・
Comparison of Fukushima Dai-ichi nuclear power plant with other power plants. (June 24, 2011)
Tohoku Electric Power Company (from website)・
Situation of Onagawa nuclear power plant during the 2011 Tohoku earthquake and tsunami. (May 30, 2011)
Japan Atomic Power Company (from website)
・
Effect of the 2011 Tohoku earthquake on Tokai Dai-ni power plant reactor facilities. (September 2, 2011)40
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Extremely Confidential

Note) The translation of this report has been done by a limited number of staff and within a limited period of time. If there
are any discrepancies between this translation and the original Japanese report, please refer to the Japanese report forclarifications.

The project would like to extend its special thanks to the following people for their great support in this translation work:
Mr. Kenjiro Ishikawa
Ms. Jewel Naruse
Ms. Seiko Toyama
Mr. Curtis Hoffmann
Ms. Keiko Sato

41
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