Updates on Fukushima Accident

• Accident Management• Degree of damage to the reactors• Developments of Energy and Nuclear Policies after

July 2011The Institute of Applied Energy

Plate Tectonics around Japan

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The 2011 off the Pacific coast of Tohoku Earthquake on March 11, 2011: Fault ModelBy Geospatial Information Authority of Japan

5.3m

1.2m

Damages of Seawall and Harbor Installation

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Output scale

Under 500MW Under 1,000MW Over 1,000MW

２０１１年５月１８日現在

Number of Number of Number of Number of

UnitsUnitsUnitsUnits

Total OutputTotal OutputTotal OutputTotal Output（（（（MWMWMWMW））））

In Operation 17171717 15493154931549315493

Not Operating 37373737 33354333543335433354

TotalTotalTotalTotal 54545454 48847488474884748847

Under Construction 3333 4141414141414141

In Operation

Not Operating

Under Construction

２

Nuclear Power Plants in Japan [as of July 21, 2011]

：Under Inspection

5

OhmaTomariHigashidori (Tohoku Electric)

Higashidori (Tokyo Electric)

１Onagawa

Fukushima Daiichi

Fukushima Daini

Tokai

Hamaoka

Ikata

３

Sendai

Genkai

Shimane

Takahama

Ohi

Mihama

Tsuruga

Shika

Kashiwazaki Kariwa

Fukushima Daiichi Nuclear Power Station

Unit #Reactor

TypeContainment

Type

Electric Output(Gross)

Start ofConstruction

Commercial Operation

Status at Earthquake

Unit-1 BWR/3

MARK-I

460 MWe 1967 1971 Operation

Unit-2

BWR/4 784 MWe

1969 1974 Operation

Unit-3 1970 1976 Operation

Unit-4 1972 1978Refueling

Outage

Unit-5 1971 1978Refueling

Outage

Unit-6 BWR/5 MARK-II 1100 MWe 1973 1979Refueling

Outage

6

Fukushima Daini Nuclear Power Station

Unit #Reactor

TypeContainment

Type

Electric Output(Gross)

Start ofConstruction

Commercial Operation

Status at Earthquake

Unit-1

BWR/5

MARK-II

1100 MWe

1975 1982

Operation

Unit-2

Improved MARK-II

1979 1984

Unit-3 1980 1985

Unit-4 1980 1987

7

BWR Safety Systems

� Control of Reactivity� Control Rods (CR)� Standby Liquid Control system (SLC)

� Removal of Heat from the Core� Residual Heat Removal system (RHR)� Emergency Core Cooling System (ECCS)

� Confinement of Radioactive Materials� Primary Containment Vessel (PCV)� Other Barriers (RPV, Reactor/Building etc.)

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Residual Heat Removal System (RHR)

Main Functions:

1) Shutdown cooling mode- Remove decay heat after

the reactor is shut down bycooling reactor water withheat exchangers.

- Heat is discharged ultimatelyto the sea through sea water cooling system.

2) Low Pressure Core Injectionmode (LPCI)

3) Other modes

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Heat Exchanger

Emergency Core Cooling System (ECCS)• Divided into:

� High Pressure (HP) system; and � Low Pressure (LP) system

(+ Automatic Depressurization System).

• Energy for operation:

� Turbine Driven (T/D) with high pressure steam from the RPV;

� Motor Driven (M/D) with AC power; or� Natural Force Driven (e.g. gravity).

10

BWR/4 Emergency Core Cooling System

ECCS- HPCI: High Pressure

Core Injection- CS: Core Spray- LPCI (RHR)

HPCI

CS

LPCI

CS

LPCI

11http://pbadupws.nrc.gov/docs/ML0230/ML023010606.pdf

BWR: Primary Containment Vessel (PCV)- MARK I Type -

� Consist of two separate volumes, a drywell and a wetwell (or Suppression Chamber), connecting with vent pipes.

� The drywell is a bulb-shape vessel made of steel and encloses the RPV.

� The wetwell is a torus with a large amount of water pool called ‘Suppression Pool’, where steam is injected and condensed to suppress the pressure increase in the PCV.

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http://www.nrc.gov/reading-rm/basic-ref/teachers/03.pdf

Inundated and Inflowed Area by Tsunami

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Fukushima Daiichi and Tsunami

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Vertical Cross Section of Unit 1

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Vertical Cross Section of Unit 2

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Vertical Cross Section of Unit 3 Buildings

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Seaside Components after Tsunami (Daiichi)

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Reactor Core Isolation Cooling System(RCIC)

• To inject water intothe reactor when thereactor is isolated.

• Driven by steam fromthe RPV.

• Controlled by DC battery. • Actuated automaticallyby a ‘Low Water Level’signal or manually.

• Stopped by a ‘HighWater Level’ signal.

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High Pressure Core Injection System(HPCI)

• To inject water intothe reactor in anemergency case.

• Driven by steamfrom the RPV.

• Controlled by DC battery. • Actuated automaticallyby a ‘Low Water Level’signal or manually.

• Stopped by a ‘HighWater Level’ signal.

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Accident Management (AM)

• Prevention and mitigation measures to a Severe Accident, an event that significantly exceeds the design basis event and could result in serious damage to the reactor core.

• Implemented by TEPCO after Chernobyl accident voluntarily (, not required by law):

� AM Guidelines prepared;� PCV vent and alternate water injection systems

installed; and � Operators trained.

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Alternate Water Injection System

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What SAM(Severe Accident Management) was in place?

[SOURCE] ICAPP2011 Presentation paper by Mr. Omoto.

Where SAM has reached?(Major Event Progression at 1F1)

[SOURCE] NISA,IAEA Safety Convention Meeting ,April 4,2011.

How much is degree of damage to the reactor?(1F1:Reactor Water Level, Maximum Core Temperature (Analysis Result))

[SOURCE] TEPCO Report (Reactor Core Status of Fukushima Daiichi Nuclear Power Station Unit1) issued on 5/15/2011

1F1:Transition of Core Status(Analysis result)

[SOURCE] TEPCO Report (Reactor Core Status of Fukushima Daiichi Nuclear Power Station Unit1) issued on 5/15/2011

Two Possible Paths to Reactor Building

�Two possibilities to accumulate hydrogen gas in the upper part of the R/B.� Leakage from

the PCV; or� Reverse flow

from venting line.

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to stack

1F1: SBO Analyses

March 11 March 12

14 16 18 20 22 24 02 04 06 08 10 12 14 16 18

CV Vent(14:30)

(19:04)Water injection

H2 Explosion(15:36)

Delay of AM about 20 hours

Rapid increase of dose-rate in operation floor of reactor building

(15:42 Tsunami SBO)

(17:00) (21:50)Melt start Failure of RPV and PCV Analysis by JNES reported at

March,2008 (MELCOR)

Analysis by JNES at June (MELCOR)(about 20:00)

RPV failureMelt start

(about 18:00)

Analysis by TEPCO at May (MAAP)(5:46)RPV failureMelt start (18:46)

Analysis by IAE at May (SAMPSON)

(19:37)(17:03)

Melt start

(21:21)

100% core meltRPV failure

(14:46 Earthquake)

�Amount of H2 in Operation Floor: about 250 kg (15%)�Deflagration Occurred�Peak Pressure: about 5 bars

Hydrogen Explosion Analysis by SAMPSON

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Aerial Dose Rate by Air Monitoring by MEXT, @July 2, 2011 Dose Estimation

Accumulated by March 11 of 2012, @July 20, 2011

Source: MEXT

Developments in Energy and Nuclear Policies after Fukushima Accident (3/11) in Japan - 1

• Prime Minister Kan expressed his idea about revising the current Basic Energy Plan 2010 including nuclear energy policy. Emergency Safety Measures to enable the recovery of cooling functions while preventing, to the extent possible, the release of radioactive materials. was launched on March 30.

• Suspension of the revision of the Framework for Nuclear Energy Policy, Atomic Energy Commission. April 5

• 1st Eminent Persons Group on future energy policies (Forum on Energy Policy) for METI met on May 12

• Progress status of the "Roadmap towards Restoration from the Accident at Fukushima Daiichi Nuclear Power Station“, TEPCO, May 17

• 1st Nuclear Incident Investigation and Verification Committee to Investigate Fukushima Daiichi NPS was held on June 7.

• In addition to the two pillars of power generation: Nuclear power and Fossil fuels, two new pillars of Renewables and Energy Saving will be added.

– percentage of renewable energy out of total power generated to at least over 20 percent by the earliest possible time in the 2020's. (about 20% in 2030 by Basic Energy Plan 2010)

– Press conference by PM Naoto Kan at the end of G8, May 27

Developments in Energy and Nuclear Policies after Fukushima Accident (3/11) in Japan - 2

• NSC directed NISA to report on Comprehensive Evaluation of Safety of Existing Nuclear Power Plants based on the Fukushima Dai-ichi NPP incident, July 6

• The Japan Business Federation, or Keidanren, said nuclear power continues to be vital for stable supplies of electricity, and that nuclear power needs to be promoted steadily by winning public understanding on the condition that its safety is secured. July 14

• NISA reported to NSC on its Two stages testing plan of the Comprehensive Evaluation of Safety of Existing Nuclear Power Plants, July 15 and 21

• Japan's Prime Minister Naoto Kan said he aims to eventually implement a policy focused on renewable energy, reducing use ofnuclear plants, to eventually end dependence on nuclear energy.

• In a joint assessment, the government and TEPCO said they have completed the first step of a restoration plan outlined in mid-April for a complete cold shutdown of the reactors within the original 3-month deadline. July 19

The report from Japan for IAEA Ministerial Conference on Nuclear Safety, June 8 (1)

• 28 items of Lessons learned categorized in five groups– Strengthen preventive measures against a severe

accident – Enhancement of countermeasures against severe

accidents – Enhancement of nuclear emergency responses – Reinforcement of safety infrastructure – Raise awareness of safety culture

http://www.kantei.go.jp/foreign/kan/topics/201106/iaea_houkokusho_e.html

The report from Japan for IAEA Ministerial Conference on Nuclear Safety, June 8 (2)

• consistent preparation for severe accidents was insufficient – fundamental revision of its nuclear safety preparedness

and response is inevitable– research to enhance preparedness and response

against severe accidents through international cooperation, and to work to lead the results achieved for the improvement of global nuclear safety

• confront much difficulty towards the restoration from the accident, and trust that we will be able to overcome this accident

- From the conclusive remarks

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Status quo (46%) Reduce (29%)

Public Poll on Nuclear Power, Pro and cons

(The Yomiuri Newspaper)

Dismantle 19%