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The Fukushima Daiichi The Fukushima Daiichi Nuclear Power Station AccidentNuclear Power Station Accident

Tomomi Matsunaga

Kansai Electric Power Company

Cooperation with JEPIC (Japan an Electric Power Information Center)

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Number of units Total power (MW) In operation �� Under construction � ��3UHSDUDWLRQ�IRU�FRQVWUXFWLRQ� ��

Total ��

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Nuclear Power Plants in Japan

Cessation of Operation : The Japan Atomic Power Co. – Tokai (1998)Chubu EP Co. – Hamaoka-1,2 (2009)

2

1

Status of Nuclear Power Plants after the Earthquake

Source: Japan Atomic Industrial Forum, INC. (JAIF)

¾ All units (Unit 1-3) were immediately shut down automatically

¾ Then safely went into cold shut down

¾ The unit was immediately shut down automatically

¾ Then safely went into cold shut down

3

The accident caused environmental damage at several units in the Fukushima Daiichi nuclear power Station after the earthquake occurred on March 11.

Other nuclear power plants in Japan were in normal operation or safely shutdown.

The Fukushima Daiichi Nuclear Power Station

4

Before the earthquake

Unit6Unit5

Unit1Unit2

Unit3Unit4

Source: NISA (http://nei.cashfly.net/static/images/BWR_illstration.jpeg)

Overview of Boiling Water Reactor (BWR) (Mark-I Type ;Fukushima Daiichi Unit 1,2,3,4 and 5)

5

Mechanism of Boiling Water Reactor (BWR)6

Containment VesselReactor Pressure Vessel

Condenser

Sea water

Pump

steam

waterGenerator

Turbine

Control rod

Suppression Chamber

fuel

Pump

Dry Well

Pump

Supply Electricity

㽴Electricity is generated by rotating the turbine and the generator with steam.

㽲Water is boiled within the reactor.

㽳Steam is generated and sent to the turbine.

Source: The Tokyo Electric Power Company, Inc.

¾ Before the earthquake ,Unit 1,2 and 3 of the Fukushima Daiichi Power plant were operating .

¾ Unit 4,5 and 6 were under periodic inspection.

¾ After the earthquake , all control rods were inserted into the reactor as designedand Unit 1,2 and 3 automatically shutdown .

¾ Offsite power supply was lost because of the earthquake.

¾ The emergency diesel generators installed in each Unit started normally.

¾ Direct damage to the safety-related equipment due to the earthquake was not found.

¾ Seawater pumps, DGs, and power panels at all Units were flooded by the tsunami, then all AC power sources for Units 1 to 6,except for one air-cooled DG for Unit 6 lost their functionality.

¾ All motor operated safety systems, water injection and cooling facilities at Units 1 to 5 became inoperable. This is the major cause of the Fukushima daiichiaccident.

Accident Description: Fukushima Daiichi NPS7

GeoEye

⑥⑤

①②③④

④

③

②

①

C

Intensive Inflow

inflow

inundated

Fukushima DaiichiFukushima Daiichi Fukushima DainiFukushima Daini

8Inundated and Inflow Area at Fukushima Daiichi and Daini Site

Turbine Electrical Generator

Condenser

Condensate Storage Tank

Poison TankStandby Liquid

Control System

Core Spray System

PCV Spray Cooling System

PCV

HPCI

RPV

Reactor Bldg.

Inoperable since the battery was soaked in water

Core Cooling by Isolation Condenser (3/11 14:52)

Feed

wat

erLi

ne

Isolation Condenser

Main Steam Line

Pump

Effort to sustain reactor water level

: Inoperable: Operable

Accident progression at Unit1(1/3)

Source: Nuclear and Industrial Safety Agency (NISA)

9

Inoperable due to the emergency DGs soaked in water (3/11 15:37)

External electricity was inoperable due to the earthquake (3/11 14:46)

HPCIFunction has not been correct

Core Spray System

Poison Tank

TurbineElectrical Generator

CondenserFeed

wat

erLi

ne

Main Steam Line

Pump

PCV

RPV

Reactor Bldg.

Isolation Condenser

Condensate Storage Tank

PCV Spray Cooling System

Decrease in reactor water level due to loss of cooling capability of emergency condenser, followed by uncovering the core

: Inoperable

Uncovering the Core(3/11 around 17:00 estimated)

Decrease in reactor water level

- Fuel Rod damage

-Hydrogen Generation due to a Zirconium- Water reaction

Accident progression at Unit1(2/3䋩


10

Accumulation of Hydrogen

Pla

ster

bo

ard

Rei

nfor

ced

Con

cret

e

Reactor building

Explosion

Reactor building

Hydrogen explosion in the operation floor


Accident progression at Unit1(3/3)11

Unit 4Unit 3

Unit 2

Accident Progression at Unit 2 through 4


12

Vapors rising from Unit 3 are assumed to be produced from Spent Fuel Pool.

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䊔䊮䊃ታᣉജ䋨㪇㪅㪐㪌㪋㪤㪧㪸㩷㪸㪹㫊䋩

Rx

Wat

er

Leve

l [m

m]

RCIC

HPCI No Operation

SRV

FP/Fire Engine

PCV Vent

䃂

Fuel Range (A) (mm)䃂

Fuel Range (B) (mm)䂾

CAMS D/W(A)(Sv/䌨䋩

䂾

CAMS S/C(A)(Sv/䌨䋩

䃂

S/C Pressure (MPa)

䃂

D/W Pressure (MPa)

䋨19:䋵䋴䋩Sea Water

Order for Vent Preparation 䂯

䋨17:30䋩

Depressurization䋨~18:00䋩

Earthquake䋨14:46䋩 Tusnami

䋨15:27䋩

䂯

(2:55) Operation confirmed

䂯

(11:00䋩

Vent Line Configuration Completed

Unit1 R/B Explosion 䋨15:36䋩

Core Damage Started due to MAAP Analysis

Rx

Pre

ssur

e [M

Pa]

D/W

& S

/C

Pre

ssur

e [M

Pa]

Fukushima Daiichi Unit 2 Plant Parameter and OperationUnit3 R/B Explosion 䋨11:01䋩

Impact sound 䋨6:00-6:10䋩

Valve Condition Unclear

Order for Sea Water Injection Preparation 䋨12:05䋩䂯

2Valves Open

Small Vent Valves Opened

(13:25)Out of Service Judged

0(TAF)

13

Source: The Tokyo Electric Power Company, Inc.

䃂

Rx Pressure (A) (MPa)

䃂

Rx Pressure (B) (MPa)

Hydrogen generation

Increase in D/W pressure

S/C pressure:0Mpa

Decrease in D/W pressure

Radioactive gas released into the air

Plant Parameter: Fukushima Daiichi Unit 2

Source: NISA and JNES

March 11 䌾 March 30, 2011

14

Increase in D/W pressure

Decrease in D/W pressure㽲around 11:30㽳around 15:00

Radioactive gas released into the air

accident - university corporation for atmospheric researchrpv g. inoperable the n water by ondenser...

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