NISA at fault

September 14, 2012

NISA skipped check of active fault under nuke plant due to 'lack of data'

http://mainichi.jp/english/english/newsselect/news/20120914p2a00m0na012000c.html

The government's Nuclear and Industrial Safety Agency (NISA) did not evaluate a possibly active fault under a nuclear reactor in Ishikawa Prefecture because there were no documents supporting an active fault there, according to internal audit results finalized on Sept. 14.

The internal audit found that the agency had ample opportunity to survey the approximately 300-meter-long S-1 fault under the No. 1 reactor at Hokuriku Electric Power Co.'s Shika nuclear plant in 2008 and 2009, the same time plant buildings were being checked for earthquake resistance. The agency, however, apparently decided to skip the survey of the fault line because "there were no documents indicating the possibility of any active fault running under the plant's premises."

In 2006, the government established new earthquake-proofing building standards for nuclear facilities, and NISA initiated checks of existing buildings to make sure they met the new standards. NISA subsequently directed power companies to make sure their plants met the new requirements.

The agency, however, did not set a deadline for the power firms to submit their reports, and the checks were delayed at many locations. In 2007 -- before all the reports had been submitted -- the Niigata Chuetsu-Oki Earthquake hit off Japan's west coast, damaging Tokyo Electric Power Co.'s Kashiwazaki-Kariwa nuclear plant in Niigata Prefecture.

In the wake of the quake, NISA began treating seismically active fault lines with new importance, and demanded that power companies submit mid-term reports on their earthquake readiness. The agency also set out a priority-based plant screening schedule, under which the examination of smaller faults on nuclear facility property was apparently pushed back.

Hokuriku Electric submitted its mid-term earthquake survivability report for the No. 2 reactor at the Shika plant in March 2008. In the report, the utility called the S-1 fault under the No. 1 reactor building "inactive." NISA never performed a follow-up survey of the fault, and approved the content of the Hokuriku Electric report in February 2009.

The S-1 fault was added to the NISA survey list only recently, after experts declared in July this year that the fault showed strong signs of being active.