NISA orders investigation

July 18, 2012

Nuclear safety agency orders underground survey

http://www3.nhk.or.jp/daily/english/20120718_26.html

Japan's nuclear safety agency has ordered power companies to assess underground cracks below 2 nuclear power plants on the Sea of Japan coast to determine whether or not they are active faults.

Experts with the Nuclear and Industrial Safety Agency suggested on Tuesday that further studies are needed on a 900-meter underground fissure that runs north-south between the No.2 and No.3 reactors at Ohi nuclear plant in Fukui Prefecture. They said a lack of data about the fissure led them to propose the investigation.

The experts also said a crack running 250 meters below the No.1 reactor at Shika nuclear plant in Ishikawa Prefecture is highly likely to be an active fault, but that analysis has been insufficient.

The agency on Wednesday instructed the plants' operators, Kansai Electric and Hokuriku Electric, to survey the sites.

The No.3 reactor at the Ohi plant is currently in operation after recently being brought back online. The No.4 reactor was also restarted on Wednesday night.

The agency says it will not order the reactors stopped for the survey, but that the outcome could affect their operation.

The agency has already ordered a reassessment of fissures at the Tsuruga nuclear plant in Fukui Prefecture and the Higashidori nuclear plant in Aomori Prefecture.

The government's quake-resistance guidelines do not allow construction of key nuclear facilities directly above active faults. This means the No.1 reactor at Shika plant might never be restarted.