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

Summary of the Earthquake and Situation of the Kashiwazaki-Kariwa NPP 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

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)

Main Incidents found in Inspections Leakage of water including radioactive materials into non-controlled area in the reactor building (Unit 6) Displacement of the main exhaust duct (Unit 3) Motor Damaged Damage found on the coupling of the drive axis of the reactor building overhead crane (Unit 6) Fire on the house transformer B (Unit 3)

Main Incidents found in Inspections (cont) Reactor Building Building Ventilation Still Working after Plant Shutdown Turbine Building Unit 7 Main Exhaust Duct Monitoring House Reactor Filter Main Exhaust Duct Turbine Gland Steam Exhauster Turbine Condenser Filter Rare Gas Hold -up Equipment Detection of radioactive materials in the main exhaust duct resulting from loss of the steam seal inside the turbine (Unit 7) 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 Fire Extinguishing Pipe Fall down of drums (Solid waste storage warehouse)

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 Division of Nuclear Installation Safety) and 5 international experts

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.

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 Subcommittee The Advisory Committee for Natural Resource and Energy (existing) (existing) The Seismic and Structural Design Subcommittee The Subcommittee for Investigation and Response to the Nuclear Facilities affected by Chuetsu-oki Earthquake The Nuclear Emergency Preparedness Subcommittee report advice report 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 name )