Fukushima Dai‐ichi Nuclear Plant Accidentandand

Risk Management

Akito ArimaAkito ArimaPresident of Japan Radioisotope Association

March 9, 2012

1

1  Introduction

2

Damage caused by the earthquakeand tsunami(No.1)

Catastrophic earthquake and tsunamiMarch 11 2011March 11, 2011

16 000 people lost their lives and16,000 people lost their lives and  3,000  people remain missing

No deaths as a result of radioactive fallout from the Fukushima Dai‐ichi Nuclear Power Plant

3

Damage caused by the earthquakeand tsunami(No.2)

Total damage cost will be of the order of 169 billion yen ($8 billion),  18% of Japan’s budget.

130,000 homes were completely destroyed., p y y240,000 homes were partially destroyed.The areas of arable land that incurred damage isThe areas of arable land that incurred damage is 23,000 ha.

4 n clear po er plants and 12 thermal po er4 nuclear power plants and 12 thermal power plants were damaged.

4

Damage to the Nuclear Power Stations 

There are 15 commercial nuclear reactors. 14 of these suffered major damage as a result of14 of these suffered major damage as a result of the Tsunami (not by the Earthquake).

The situation at 3 reactors of the FukushimaThe situation at 3 reactors of the Fukushima Dai‐ichi was very serious due to the resultant d t th i tdamage to their reactor core.

5

Tohoku District - off the Pacific Ocean Earthquake

Occurrence: 14:46 March11, 2011

Mw(moment magnitude): 9.0( g )

Epicenter: approximately 130km off the coast of Sanrikuoff the coast of Sanriku(at 38.10 degrees north latitude,142.86 degrees east longitudeand 23 7km deep)and 23.7km deep)

6Map of JMA seismic intensities observed during the main shock. 6

Location of NPSs in the Tohoku District

Higashidori NPS

Fukushima Dai ichi NPS

Onagawa NPS

Fukushima Dai-ni NPS

Fukushima Dai-ichi NPS

Tokai Dai-ni NPS

77

2   JCO Accident

8

Criticality accident at JCOCriticality accident at JCO 

h l d h l f lThe criticality accident at the JCO nuclear fuel processing plant on September 30th in 1999.

Th iti lit t t t d 19h dThe criticality state was stopped 19hrs and 40mins.

9

Key to resolve the accident at JCOKey to resolve the accident at JCO 

ll h f ll d kAll the following entities tried to work as one in a cooperative way.all members of Science and Technology Agency ll h f th J At i Eall researchers of the Japan Atomic Energy Agencyall nuclear researchers in Japan 

10

New Legal System for Nuclear DisasterNew Legal System for Nuclear Disaster

New legal system was established due to g y

JCO accidentJCO accident

“The Special Law on Nuclear Disaster 

Countermeasures” 

11

3 Fukushima Dai‐ichi Nuclear3 Fukushima Dai‐ichi Nuclear Power Plant Accident

12

(1)Occurrence of the Accident(1)Occurrence of the Accident

Fukushima Dai‐ichi Nuclear Power Station was attacked by the earthquake and tsunamiy qThe scale of the earthquake was  M9.0.The protective infrastructure was designed only to withstand a tsunami of maximum height 5.7m。

The height of the Tsunami was in excess of 15mThe height of the Tsunami was in excess of 15mat the Fukushima Dai‐ichi.

13

Location of NPSs within Fukushima

ichi NPSFukushima Dai-

ichi NPS

Fukushima Dai-niNPSNPSNPS

Layouts of Fukushima Dai-ichi NPS and Fukushima Dai-ni NPSy

Unit 5

Unit 6Fukushima Dai-ichiNPS

Fukushima Dai-niNPS

Unit 3

Unit 4

Unit 1

U it 1

Unit 2

Unit 2

Unit 3

14

Unit 1Unit 4

14

Status of the Fukushima Dai‐ichi Nuclear Power Station before earthquake and tsunami

St t f 6 t b f th th k d t iStatus of 6 reactors before the earthquake and tsunami Unit１：under operation Unit２：under operation Unit２：under operation Unit３：under operation Unit４：under periodic inspection( all the fuel were Unit４：under periodic inspection( all the fuel were removed from the reactor to the spent fuel pool)

Unit５：under periodic inspectionp p Unit６：under periodic inspection

。

15

Main Sequence of the Accident (No 1)Main Sequence of the Accident (No.1)

Main sequence of accident at reactors 1 to 3Reactors 1 to 3 went into automatic shutdownReactors 1 to 3 went into automatic shutdown following the earthquake and emergency diesel generators started updiesel generators started up.Earthquake and subsequent tsunami broke the reactors’ connection to the external AC power supply.power supply.

16

Main Sequence of the Accident (No 2)Main Sequence of the Accident (No.2)

Main sequence of accident at reactors 1 to 3Tsunami caused the emergency dieselTsunami caused the emergency diesel generators to cease working.  Th h d h f l lThen the reactors and the spent fuel pools became unable to be cooled. This triggered a core nuclear meltdown in reactors 1 to 3 and hydrogen explosion in thereactors 1 to 3, and hydrogen explosion in the buildings of reactors 1, 3 and 4.

17

Current Status of the ReactorsCurrent Status of the Reactors

A two‐step cooling operation (Step1 and Step2) in reactors 1 to 3 was executed. p )In December 16 it was announced that this cold shutdown state had been achievedcold shutdown state had been achieved.

18

Current Status of “Roadmap towards Restoration from the Accident at Fukushima Daiichi Nuclear Power Station, TEPCO” (Step 2 completion)

☆: already reported to the government, Green colored shading: achieved target

December 16, 2011Nuclear Emergency Response HeadquartersGovernment-TEPCO Integrated Response Office

IssuesAs of Apr. 17 Mid‐term issues Step 2 (through the end of this year)

Step 1 (around 3 months) current status Issues(first announcement)

Step 1 (around 3 months)   

(

1) R

Cooling by minimum injection rate(injection cooling)

Consideration and preparation of reuse of accumulated water

Circulating water

cooling (start) ☆

Maintain and Continue cold shutdown condition

(around 3 years)

Circulating Circulatingwater                water cooling      cooling ☆ (continued)(start)

Cold shutdo

Stable

Fresh wat

（as of Dec. 16）

I.Cooling

Reactor

Protection against corrosion cracking of structural materials*

reuse of accumulated water

Improvement of work environment ☆ *partially ahead of schedule

Nitrogen gas injection

(start)

Nitrogen gas injection ☆ Nitrogen gas injection (continued)

own condition

e cooling

ter Injection

Installation of

(

2) Spent Fuel Pool

Fresh water

injection Consideration / installation of heat exchanging function

Remote‐controlledinjection operation

Circulation cooling system (installation of heat exchanger)☆*partially ahead of schedule

Start of removal work of fuels

More stablecooling

Reliability improvement in injection operation / remote‐control operation *ahead of schedule

Stablecooling

/ ☆Expansion☆ / consideration of

(

3) Accumulated W

Transferring water with high radiation level

Installation of storage facilities /

Installation of full‐fledged water processing facilities

Continuous processing of accumulated water

Storage / management of sludge waste etc.

Installation of storage / processing facilities ☆

Research on processing of l d

Storage ☆ / management ofsludge waste etc. 

Expansion ☆ / consideration of full‐fledged processing facilities

Decontamination ☆ / desalinationprocessing (reuse), etc

Reduction of total amof accum

ulated w

Secure storage place

II. Mitiga Design / implementation

f i bl ll

Storing water with low radiation level

Mitigation of contamination in groundwater

Water

decontamination processing

(

4) Grou

water

Mitigation of contamination in the ocean

Establishment of impermeable wall

Mitigate oc

contamina

Mitigate oc

Contamina

(continue

Mitigation of contaminationin groundwater

Consideration of method of i bl ll i

(Restoration of sub-drainage pumps with expansion of storage / processing facilities)

sludge waste etc.

Mitigation of contamination in the ocean

mount

water

ation

of impermeable wall against groundwater

(

5) Atmos

und

Installation of reactor buildingcover (Unit 1) ☆

Establishment of impermeable wall against groundwater

cean tion

cean ationed)impermeable wall against 

groundwater

l f d b / ll f

Dispersion of inhibitor

Removal / management of debris

Dispersion of inhibitor   Dispersion of inhibitor (continued)

Removal / management of debris                                                Removal / management of debris (continued)

Mitigate (cont

Mitigate 

19

sphere / Soil

Start of installation work ofreactor building container

Consideration of reactor building container

Removal of debris / installation of reactor building cover (Unit 3&4)

Installation of PCV gas control system

Removal of debris (top of Unit 3&4 R/B)

Installation of PCV gas control system

scatteringinued)

scattering

As of Apr 17 Mid‐term issuesStep 2 (through the end of this year)

Current Status of “Roadmap towards Restoration from the Accident at Fukushima Daiichi Nuclear Power Station, TEPCO” (Step 2 Completion)

☆: already reported to the government, Green colored shading: achieved target

ⅱDecember 16, 2011Nuclear Emergency Response HeadquartersGovernment-TEPCO Integrated Response Office

IssuesAs of Apr. 17

(first announcement) Step 1 (around 3 months)    

(

6) Measur

ReductionDisclosu

III. Monito

Decontam

Continuous environmental monitoring

Mid term issues(around 3 years)

Step 2 (through the end of this year)

Expansion, enhancement and disclosure of radiation dose monitoring in and out of the power station  

Decontam

current status （as of Dec.16）

rement, 

n and ure

oring/ ination

IV. Couagainst 

(

7) TsuRei

Continuous decontamination

Continue various countermeasures for radiation shielding

Enhancement of countermeasures against aftershocks and tsunami, preparation for various countermeasures for radiation shielding

Mitig

mination

Consideration/start of  full‐fledged decontamination

(

8)

untermeasures 

aftershocks, etc

nami,  

nforcement, etc

Reinforcement work of each UnitConsideration of reinforcement work of each Unit ☆

(Unit 4 spent fuel pool) Installation of supporting structure ☆

radiation shieldingE

preparation for various countermeasures for radiation shielding ate disasters

) Living/working 

environment    

V. Envi (

9

Improvement of  workers’ living /  working environmentImprovement of workers’ living / working environment

Enhancement of 

environment 

Improvem

entEn

(

10)pers

ronment im

provem

9) Radiation control  /Medical care

Improvement of radiation control / medical systemImprovement of radiation control / medical system

nhancement of 

Healthcarera) S

taff Training / sonnel allocation

ment

Concept of mid‐term security

Systematic implementation of staff training / personnel

allocation

Systematic implementation of staff training / personnelallocation

Exhaustive adiation dose 

control

20

Action plan for mid-and-long-term issues

Response based on the plant operation plan

securityEstablishing plant operation plan 

based on mid‐term security

Formulating a mid‐and‐long‐term roadmap

Future Steps towards Decommissioning

Step by step approach  towards decommissioning will be taken.gThe plan for the removal of fuel from the spent fuel pool and the removal of fuel fromspent fuel pool and the removal of fuel from the reactors will now be made.The decommissioning of the Fukushima Dai‐ichi Nuclear Power Plant is expected to take aichi Nuclear Power Plant is expected to take a period of the order of 30 to 40 years.

21

Countermeasures at off siteCountermeasures at off‐site

ff iCountermeasures at off‐siteThe area within a 20km radius of the power pplant was declared a “no‐go zone”.  Entry to this area was prohibited.pA decontamination initiative has been undertakenundertaken.No confirmed long term health effects to only 

h b t d lt fperson has been reported as a result of radiation exposure.

22

Result of airborne monitoring by MEXT and DOE

23as of July 2,2011 23

Protected Areas

k t

IidateEvacuation Prepared Area in

f Ekwamata Minami Soma

Deliberate Evacuation Area

case of Emergency

Evacuation Area

NamieKatsurao

Fukushima Dai-ichiOkuma

Futaba

Tamura

Fukushima Dai-ni

TomiokaKawauchi

Evacuation Prepared Area in case of Emergency

Ono Naraha

HironoHirono

24

Decontamination of Roof of Private House 

Cleaning by high pressured water

Preparation of decontamination

Cleaning by high-pressured water

Cleaning by high-pressured water

Decontamination(Back of rainwater pipe) Before: 40-50 kcpmAfter: less than 10kcpmAfter: less than 10kcpm

Before AfterEnd of rainwater pipe near ① 45 - 65

14End of rainwater pipe near ② 50 – 170Average 10 - 35

(Source: Cabinet Office based on Materials in Atomic Energy Commission Meeting)25

Generation of Contaminated Waste by Decontamination

Waste from School

Waste from private house

Soil bag around waste for

Waste from private house

gshielding

Contaminated soil buried in playground Waste from three private houses

(Source: Cabinet Office based on Materials in Atomic Energy Commission Meeting)26

(2)Features of the Accident(No 1)(2)Features of the Accident(No.1)

Diff f F k hi D i i hi f th JCODifferences of Fukushima Dai‐ichi from the JCO accident, the accident at 3‐mile island and Chernobyl nuclear power plants;Chernobyl nuclear power plants;

a)the earthquake and subsequent tsunami caused significant damage to basic infrastructurescaused significant damage to basic infrastructures including transport, communications and instrumentation.

b)a severe nuclear accident known as a core meltdown occurred.

c)accidents occurred simultaneously in a plurality of nuclear reactors. 

27

(2)Features of the Accident(No 2)(2)Features of the Accident(No.2)

Differences of Fukushima Dai‐ichi from the JCO accident, the accident at 3‐mile island and Chernobyl nuclear power plants;d) a hydrogen explosion occurredd)  a hydrogen explosion occurred.e)  the accident occurred over an extended period of timef)a large quantity of radioactive material wasf)a large quantity of radioactive material was released into surrounding areas. 

28

(3)Factors hindered to the establishment of cooperation between the related parties

) i d t di ti b t th t la) inadequate coordination between the central disaster countermeasures headquarters and the local disaster countermeasures headquarters 

b) insufficient numbers of experts and persons ofb) insufficient numbers of experts and persons of required experience mobilized at the early stages 

c) inadequate coordination between the Cabinet Secretariat, Cabinet Office, Ministry of Economy,Secretariat, Cabinet Office, Ministry of Economy, Trade and Industry

29

Organization for response to the nuclear emergency

Nuclear Emergency Response

(Law Cabinet Decisions)

Cabinet Office

pHeadquarters

Chief:Prime Minister

Local Nuclear Emergency Response HQs (Inside Prefectural Office of Fukushima)

Government  ‐ TEPCO Integrated Response Office

(including assistance from overseas)

Team in charge of Assisting the

Lives of Victims d th N l

Team in charge of Responding to the 

Cabinet Office

around the Nuclear Power Plant Economic Impact caused

by the Nuclear Power Station Incident

(review meetings of ministerial 

30

Cabinet SecretariatLiaison Meetings among relevant 

ministries and agencies

( glevel if necessary)

30

Workers’ EffortsWorkers  Efforts

h d d ff f l dThe endeavor and efforts of employees and personnel of Tokyo Electric Power Co. Ltd. and th F k hi D i i hi N l P Pl tthe Fukushima Dai‐ichi Nuclear Power Plant should be appreciated. 

I commend all the technicians in this task for their resolve and commitment to completing the 

i hi h i d doperation which was carried out under most difficult conditions imaginable –not described in 

t i i l d hi h t dany training manual‐and which prevented a worst‐case scenario.

31

(4)Damages caused by the Earthquake and  Tsunami 

b l d h hIt may be accurately assumed that the situation which led to the accident at the Fukushima Dai‐ichi Nuclear Power Plant would not have arisen if only the earthquake alone had occurred.only the earthquake alone had occurred. The accident that led to the core meltdown at the F k hi D i i hi N l P Pl t bFukushima Dai‐ichi Nuclear Power Plant can be attributed to the tsunami. 

32

The Fukushima Dai ichi Nuclear Power PlantThe Fukushima Dai‐ichi Nuclear Power Plant 

（１） f（１）The Tohoku‐Pacific Ocean earthquake struck this Plant at 2.46 p.m. on the afternoonstruck this Plant at 2.46 p.m. on the afternoon of March 11 2011

(2) A huge tsunami hit it.(2) A huge tsunami hit it.

Because of the earthquake, all 6 external power 

supply lines were knocked out.

This loss of power triggered 12 emergency diesel 

generators automatically started to provide 

b k l h h ha back up AC power supply to the reactors which 

resulted in the cooling of the reactorsresulted in the cooling of the reactors.

However, 11 of these emergency diesel generators 

malfunctioned because of the tsunami.

b bl lIt became impossible to cool down reactors 1 to 4.  

The melt down of the nuclear reactors of 1 2 and 3The melt down of the nuclear reactors of 1,2 and 3 

was due to the tsunami.was due to the tsunami.

AC Power Supply at Fukushima Dai ichi NPSat Fukushima Dai-ichi NPS

[External power supply]  [Emergency diesel generators][ p pp y]

x

[ g y g ]

X (Unit 1)X (Unit 1)Yonomori ‐line No 1x

xx

X (Unit 1)X (Unit 2)X (Unit 2)X (U it 3)

Yonomori line No.1

Yonomori‐ line No.2

Ok ma line No 1xx

X (Unit 3)X (Unit 3)X (Unit 4)

( )

Okuma‐ line No.1

Okuma‐line No.2

Ok li N 4xx

X (Unit 5)X (Unit 5)X (Unit 6)

Okuma‐line No.4

TEPCO nuclear lineX (Unit 6)O (Unit 6)

Earthquake andEarthquake and Tsunami Tsunami

3636

One of 12 emergency generators was located on 

the 1st floor of the building of reactor 6 was able 

to be continuously maintained.  

Reactors 5 and 6 were able to be cooled down. 

Main Sequence Flow of the Accident of Unit1, Unit2 and Unint3 of Fukushima Dai-ichi NPS

Loss of external power supply due to earthquake

Start‐up of emergency power generation

Core cooling system not using AC power

(Unit1:IC(isolation condenser), Unit2 (RCIC(reactor core g

All emergency diesel power generators stopped except for one generator in

isolation cooling system), Unit3: RCIC and HPCI (high pressure core injection system)

(11 emergency diesel power generator stopped, and one generator(with air cooling)survived.)

stopped except for one generator in Unit6 due to tsunami

Stop of core cooling system not using AC power

Loss of all AC power supply

Water injection from a fire extinguishing line

Loss of all AC power supply except for Unit6

(Unit 5 took power supply from Unit6 on 13 March).During this time without cooling the fuel

(Unit1:pure water‐>sea water, Unit2: sea waterUnit3: pure water‐> sea water)

During this time without cooling, the fuel was exposed and core melt started, 

generating hydrogen3838

(5)Effects of Earthquake(5)Effects of Earthquake Th f d t l i t it f th f ilit f ll i th The fundamental integrity of the facility following the 

earthquake was originally thought to have been maintained. This earthquake toppled several external power source q pp p

electricity pylons connected to the Fukushima Dai‐ichiNuclear Power Plant collapsed. 

The range of maximum acceleration observed during the The range of maximum acceleration observed during the quake which struck this power plant was between 319 and 550 gals, and the maximum response acceleration was 

d d i t 2 3 d 5exceeded in reactors 2, 3 and 5.  However, in reality, additional allowances in the 

earthquake‐resistant design meant that the damage to theearthquake resistant design meant that the damage to the due to the earthquake went unconfirmed. 

39

Collapsed TowerCollapsed Tower

• Damage of external power supply systems of the Fukushima Dai‐ichi and Dai‐ni NPSs

4040

(6)Effects of Tsunami(6)Effects of Tsunami

I h b bli h d h h f h It has been established that the cause of the Fukushima Dai‐ichi Nuclear Power Plant accident was the tsunami that engulfed the facility following thethe tsunami that engulfed the facility following the earthquake.

The Jougan tsunami was a huge tsunami that struck the The Jougan tsunami was a huge tsunami that struck the North‐eastern coastal region of Japan in the year 869. 

Given this and the recommendation for further studies Given this and the recommendation for further studies on the basis of additional knowledge acquired regarding the Jougan tsunami, it was apparent that the region was on the brink of suffering an earthquake that resulted in this tsunami. 

41

Onagawa Nuclear Power StationOnagawa Nuclear Power Station At th O l l t i t i d b th At the Onagawa nuclear power plant maintained by the 

Tohoku Electric Power Company and located closest to the epicenter, adequate tsunami countermeasures involving 

f fthe use of seawater pumps that allowed for an assessment of the tsunami were adopted and, as such, an accident at the nuclear power plant was able to be avoided. p p

Comparing the tsunami countermeasures implemented at th F k hi D i i hi NPS ith th t ithe Fukushima Dai‐ichi NPS with the tsunami countermeasures implemented at the Onagawa NPS,I am hesitant to suggest that there were adequate allowances were made in the measures adopted to deal with the situation at Fukushima. 

42

Tsunami getting over seawall at the Fukushima Dai‐ichi NPS

Seawall (height: 10m)

SeawallSea a

4343

Damage caused by TsunamiDamage caused by Tsunami  

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(7)Accident Management(7)Accident Management

Cooling of the reactor core by a substitute method based on pumping water from a fire p p ghydrant was possible as part of the accident management policy preparationsmanagement policy preparations.The adequate implementation of this function 

l b b l f llwas precluded by an inability to fully and completely carry out the accident management policy. 

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Unit 1 (alternative coolant injection via a fire extinguishing line)

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(8)Hydrogen Explosion(8)Hydrogen Explosion

The severity of the accident situation was aggravated by the hydrogen explosions that gg y y g poccurred within the nuclear reactor buildings. It is unfortunate that the countermeasures forIt is unfortunate that the countermeasures for dealing with the build‐up of hydrogen, 

l h f lincluding the countermeasures for dealing with the build‐up of hydrogen in the reactor buildings, were lacking.

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Destruction of the buildingby hydrogen explosion  

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(9)Venting Operation(9)Venting Operation

h i i d k l fThe venting operation was undertaken only after the complete evacuation of residents had been 

fi d B th k i l t dconfirmed. Because the work was implemented in the absence of power, workers initially attempted to carry out the venting operationattempted to carry out the venting operation manually.

B f h hi h d di i hBecause of the high‐dose radiation amounts, the operation was instead performed remotely using th i f ll t bl t dthe air of a small portable compressor operated with batteries taken from employees’ vehicles. 

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(10)SPEEDI (System for Prediction of ( )Environmental Emergency Dose Information) 

Assuming emission source information was able to be obtained, the SPEEDI system would yprobably have been used to assist in dealing with the accidentwith the accident.The action plan must be reviewed to ensure 

h bl h f hthe establishment of a system that is functional system even during the most severe of accidents. 

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4 Lessons for the Future in Terms4 Lessons for the Future in Terms of Risk Managementg

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(1)Countermeasuresfor Tsunami and Flood

There have not been enough countermeasures adopted for tackling the phenomenon of the tsunamis that potentially accompany an earthquake. q

Nuclear facilities need to adopt thorough countermeasures for tsunamis and floods basedcountermeasures for tsunamis and floods based on appropriate assumptions about occurrence frequency with consideration to the recurrencefrequency with consideration to the recurrence period, and also about the scale of such an event. 

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(2)Probabilistic Safety Assessment (PSA) 

PSA has not been adequately utilized and managed in Japan. PSA has not been used at g pall in Japan for determining the risk associated with tsunamiswith tsunamis. Adequate countermeasures based on the 

l f h hactive utilization of the PSA method to pinpoint and eliminate the failings of nuclear power plants must be adopted. 

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(3)Organizational System(3)Organizational System

di id l i h In responding to an accident, personnel with expertise in nuclear power generation technology must be assembled promptly, and the knowledge of all specialist organizations must be utilized. A system that allows for appointed y ppgovernment advisers to appropriately implement community‐related measuresimplement community related measures including evacuation.

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(4)Assembly of Scholars(4)Assembly of Scholars

Nuclear energy requires not only nuclear engineering but also other wide range of fields g g gsuch as earthquake and tsunami engineering, etcetc.A system for improving safety standards based 

h f h l f llon the active participation of scholars from all these related fields must be established. 

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The absolute necessity for advancement in research of the related fields.Scientific research into natural disasters like earthquakes and tsunamis and the predictiveearthquakes and tsunamis and the predictive research of them.Disaster prevention engineering incorporating earthquake and tsunami countermeasuresearthquake and tsunami countermeasures must be further developed.

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Zeal for safety research was evident at the initial stage of nuclear power development in Japan, g p p pbut no longer exists.

Continuous and accumulated safely research is a necessary foundation for guaranteeing nuclear powernuclear power. 

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Comprehensive research plans in each of various fields of earthquakes, tsunamis, severe accident q , ,and PSA etc. must be reviewed and reconstructed with the aim of achieving improved safelywith the aim of achieving improved safely.

International cooperation is necessary for the active development of these research plans.active development of these research plans.

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The present accident is as described belowThe present accident is as described below

(1) O f h i h i bili f(1) One of the aspects is the incapability of reactor core cooling.  Its reasons are the Loss‐of‐Offsite‐Power event caused by the quake and the drench of 11event caused by the quake and the drench of 11 emergency diesel generators and their distribution boards caused by the tsunami. The generators and y gtheir boards are located at the low level and even at the underground.

(2) The confusion of the decision‐making process for the residents against scattered radio activities at thethe residents against scattered radio activities, at the level of Japan government, TEPCO, and each local government. 

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The accident caused by the human factorsThe accident caused by the human factors

(1) the lack of viewpoint of Tsunami severe accident by the authorities concerned and TEPCO.accident by the authorities concerned and TEPCO.Especially they did not imagine multiple disasters 

h iat the same time. 

(2) They did not imagine loss of all power sources.

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(5)Promotion of Research(5)Promotion of Research

Continuous and accumulated safety research is a necessary foundation for guaranteeing y g gnuclear power. Comprehensive research plans must beComprehensive research plans must be reviewed and reconstructed with the aim of h fachieving improved safety

International cooperation is necessary for theInternational cooperation is necessary for the active development of these research plans. 

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ConclusionConclusion

We must utilize both renewable energy and nuclear energy for solving the two big problems.gy g g pThe two big problems(1) h h i f f il f l(1) the exhaustion of fossil fuels(2) the global warming( ) g g

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ConclusionConclusion

We have a responsibility to our predecessors and a responsibility to the future of the world p yto continue to achieve further advancements in nuclear powerin nuclear power.Research and development in respect of final 

l h l h l breactor disposal technologies should be considered at the international level. 

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More important and urgent problem;

Back End (decommissioning) problem

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Develop final disposal methods such as partitioning and transmutation technology p g gyDecide final disposal sitesdand

Develop the technologies for decommissioning p g gnuclear reactorsI t ti l ti i i di blInternational cooperation is indispensable.

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Thank you for your attention

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