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Niigataken Chuetsu-oki Earthquake and its Influences on the Kashiwazaki-Kariwa NPP

Niigataken Chuetsu-oki Earthquake and its Influences on the Kashiwazaki-Kariwa NPP

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Summary of the Earthquake andSituation of the Kashiwazaki-Kariwa NPP

• Summary of the Earthquake– Occurrence: July 16, 2007 at 10:13 am JST– Earthquake Source:

• 17km below the seabed off Jo-chuetsu area in Niigata prefecture (37°33.4′North 、 138°36.5′East ）

• Epicenter Distance: 16km from the NPP– Magnitude: 6.8

• Situation of the NPP– When the earthquake occurred:

• Unit 2 was in start-up• Unit 3, 4 and 7 were in normal operation• Unit 1, 5 and 6 were out of operation for the periodic inspections

– Units 2, 3, 4 and 7 were automatically shut down following the high seismic acceleration trip signals

Kashiwazaki-Kariwa NPP

Niigata city

Epicenter

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Influences of the Earthquake on the NPP

• Inspections have been performed from just after the earthquake, and the followings are found up to August 10.

– Incidents found in visual inspections (69 incidents)• Incidents related to radioactive materials (15 incidents)

– Leakage of water including radioactive materials into non-controlled area in the reactor building (Unit 6)

– Flooding on the operating floor in the reactor building (Unit 1～ 7)– Leakage of water into B5 floor of the reactor combination building (Unit

1)– Displacement of the main exhaust duct (Unit 1～ 5)– Detection of radioactive materials in the main exhaust duct (Unit 7) etc

• Incidents not related to radioactive materials (54 incidents)– Fire on the house transformer B (Unit 3)– Deviations from LCO (Unit 1～ 3)– Fall of the service platform into the spent fuel pool (Unit 1, 4)– Fall down of drums (Solid waste storage warehouse) etc

– Incident found in detailed inspections• Damage found on the coupling of the drive axis of the reactor

building overhead crane (Unit 6)

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Main Incidents found in Inspections

Fire on the house transformer B (Unit 3)Fire on the house transformer B (Unit 3)

Displacement of the main exhaust duct (Unit 3)Displacement of the main exhaust duct (Unit 3)Leakage of water includingradioactive materials into

non-controlled area inthe reactor building (Unit 6)

Leakage of water includingradioactive materials into

non-controlled area inthe reactor building (Unit 6)

Motor Motor

Damaged

Damage found on the coupling of the drive axisof the reactor building overhead crane (Unit 6)

Damage found on the coupling of the drive axisof the reactor building overhead crane (Unit 6)

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Main Incidents found in Inspections (cont)

Fall down of drums (Solid waste storage warehouse)Fall down of drums (Solid waste storage warehouse)Leakage of water into B5 floor of

the reactor combination building (Unit 1)Leakage of water into B5 floor of

the reactor combination building (Unit 1)

B1 Floor

B2 Floor

B3 Floor

B4 Floor

B5 Floor

Sump

Duct

Reactor Combination Building

Pene

Water Flow-in

Break of FireExtinguishing Pipe

Detection of radioactive materials in the main exhaust duct resulting from loss of the steam seal inside the turbine (Unit 7)Detection of radioactive materials in the main exhaust duct resulting from loss of the steam seal inside the turbine (Unit 7)

Unit 7Main Exhaust

DuctMonitoring

House

Main

Exhaust D

uct

Filter

Filter

Reactor Building

TurbineBuilding

Reacto

r Turbine

Condenser

Rare Gas Hold-up Equipment

Turbine GlandSteam Exhauster

Building Ventilation

Still Workingafter Plant Shutdown

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The IAEA Mission to the NPP

• The objectives were to conduct a fact finding mission in relation to the current conditions at the nuclear power plant and to identify the preliminary lessons learned from the event.

– Mission Date: August 6 to 10, 2007– Location: Kashiwazaki-Kariwa NPP and NISA Headquarter etc– IAEA Review Team: Team Leader (Mr. Philippe Jamet, Director of the Divisi

on of Nuclear Installation Safety) and 5 international experts

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Outlines of the IAEA Mission Report

• Based on the report release dated August 17 on the IAEA HP, main findings and lessons learned are as follows:

– Operating plants were automatically shutdown and all plants behaved in a safe manner, during and after the earthquake. The three fundamental safety functions of (a) reactivity control, (b) removal of heat from the core and (c) confinement of radioactive materials were ensured.

– Very minor radioactive releases to the environment were estimated to result in an individual dose well below the authorized limits.

– Safety related structures, systems and components seem to be in a general condition much better than expected for such a strong earthquake. This is probably due to the conservatisms introduced at different stages of the design process.

– In accordance with the new seismic guidelines, a re-evaluation of the seismic safety needs to be done taking into account the effects of the Niigataken Chuetsu-oki earthquake and the potential existence of active faults underneath the site.

– The possibility that a component remains functionally available under normal operating conditions but sustains hidden damage, should be considered.

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How to Advance Future

• "The Subcommittee for Investigation and Response to the Nuclear Facilities affected by Chuetsu-oki Earthquake" have been established as shown below.

• The subcommittee investigates the facts regarding the concrete influence of the earthquake on the NPP, and determines future action assignments and measures for the regulatory body and licensees.

The Nuclear and Industrial Safety SubcommitteeThe Advisory Committee for Natural Resource and Energy

The Seismic and StructuralDesign Subcommittee

The Nuclear Emergency Preparedness Subcommittee

The Subcommittee for Investigation and Response

to the Nuclear Facilities affected by Chuetsu-okiEarthquake

WG for the Evaluation of Management and Equipment

Integrality (Tentative name )

WG for Self-Defense Fire Fighting and Information Connection/ Service of the Nuclear Facilities affected by Chuetsu-oki Earthquake (Tentative na

me )

(existing) (existing)

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