Shika too

July 17, 2012

Research shows Shika atomic plant may sit on active quake fault

http://mainichi.jp/english/english/newsselect/news/20120717p2g00m0dm042000c.html

TOKYO (Kyodo) -- Governmental research has suggested a strong possibility that a fault beneath Hokuriku Electric Power Co.'s Shika Nuclear Power Station may be active, raising questions about the utility's claim in the late 1990s that it is inactive, sources familiar with the research said Monday.

Government regulations do not allow construction of a nuclear reactor above an active quake fault. If it is confirmed active, the Shika power station may be labeled as sitting on premises ineligible for a nuclear power plant.

The research by the Economy, Trade and Industry Ministry's Nuclear and Industrial Safety Agency shows the fault -- technically named S-1, which runs southeast to northwest within the premises -- moved sometime after 130,000 to 120,000 years ago, the sources said.

Hokuriku Electric Power conducted excavation surveys when it applied for building a second reactor for the plant in 1997 and, based on it, said the fault "does not indicate activity."

In a review of fault lines after the Great East Japan Earthquake of March 11, 2011, NISA went through excavation data presented by Hokuriku Electric and came to a conclusion that the research suggests a strong possibility that S-1 may have been active in a relatively recent period.

Geological layers comprised not just bedrock from ancient periods but sand and pebbles from a period dating back to 130,000 to 120,000 years and they were deformed, according to the sources.

It remains unknown at this point if S-1 generates a quake on its own or shakes ground in association with nearby active faults. Given that another fault lies beneath the No. 2 reactor, if the two faults jolt at the same time, it could throw the plant into danger.

Mitsuhisa Watanabe, a geomorphology professor at Toyo University, said, "I must say Hokuriku Electric is making a far-fetched assessment in saying that geological layers of 130,000 to 120,000 years have not been morphed."

Watanabe said the fault is suspected of having been active in a later period.

Research and surveys by NISA have suggested that a soft fault layer, called a crushed zone, could move at Japan Atomic Power Co.'s Tsuruga Nuclear Power Station in Fukui Prefecture, raising the possibility that the plant may have to be shut down.

Citizens are also calling for research into Kansai Electric Power Co.'s Oi nuclear power plant relating to a similar soft fault layer.