30 Jan (NucNet): Japan�s Kashiwazaki-Kariwa nuclear power plant operated safely during and after a major earthquake that struck in July 2007, a new report from International Atomic Energy Agency (IAEA) experts confirmed today.

The report, which has already been sent to Japan�s Nuclear and Industrial Safety Agency, is the third in a series issued by an IAEA-led team of international experts that completed its mission in December 2008. Two previous missions were carried out by the same team in August 2007 and January 2008. All missions were carried out at the invitation of Japan�s government.

All seven units at the plant, in Niigata prefecture, have been shut down since the earthquake.

The IAEA said today: �The consequences of the July 2007 earthquake on the plant were unique in the sense that the levels of seismic ground motion estimated in the design process were very significantly exceeded by the event.�

However, the IAEA said: �The mission found that there is consensus in the scientific community about the causes of those unexpectedly large ground motions experienced at the plant site and, consequently, it has been possible to identify the precautions needed to be taken in relation to possible future events and the newly-calculated seismic hazard at the site is much higher than both the July 2007 event and the original design earthquake level.

�These precautions were based on extensive studies and assessments conducted by a number of specialised institutions and experts in different fields. The necessary upgrades and actions were consequently defined and are being implemented by the Japanese utility (Tokyo Electric Power Company) for both safety and non-safety related components at the nuclear power plant.�

Lessons learned from the results of the plant integrity evaluation process applied to the July 2007 earthquake and used for the seismic safety re-evaluation to the new higher seismic input will improve the design and evaluation criteria and approaches currently used in Japan and worldwide, the IAEA said.

The results are also contributing to an ongoing review and revision of related IAEA safety standards, which are expected to be released shortly, the agency said.

The report is on the IAEA�s web site (http://www.iaea.org).

� by John Shepherd

>>Related reports in the NucNet database (available to subscribers)

IAEA Experts Prepare For New Japan Visit To Review Quake Analyses (News in Brief No. 128, 6 November 2008)

'Steady Progress� Being Made At Japan�s Quake-Hit Kashiwazaki-Kariwa (World Nuclear Review No. 46, 26 November 2008)

IAEA Team Completes Third Kashiwazaki-Kariwa Mission (News in Brief No. 140, 11 December 2008)

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