Japan: Tsuruga Nuclear Plant May Have Been Built On Active Fault And Could Be ‘Disqualified’

Active faults may force Tsuruga atomic plant to be ‘disqualified’ (Mainichi/Kyodo News, April 25, 2012):

TSURUGA (Kyodo) — The Tsuruga nuclear plant of Japan Atomic Power Co. in Fukui Prefecture could be “disqualified” as a fault running under it and soft earth layers may have moved together in the distant past, nuclear power regulatory agency officials said Tuesday.

It is unusual for government officials to point out the possibility that a nuclear power plant is faced with such a fundamental problem. The state does not allow a reactor building or other key nuclear facilities on an active fault or a fault that could move along with it.

If the risk that it could move along with an active fault is confirmed, the two-reactor Tsuruga plant could be decommissioned.

The Nuclear and Industrial Safety Agency under the Ministry of Economy, Trade and Industry has decided to call for Japan Atomic Power to immediately conduct an investigation, saying it cannot judge the plant’s safety until the result of the new investigation is known.

The decision follows a report by a team of 10 agency officials and members of its expert panel who examined faults running under the plant’s premises, including one fault stretching 35 kilometers called Urazoko. Also under the premises are around 160 soft fractured zones.

“It is highly likely that the fractured zones moved in a new period given features of the strata,” said one expert. “They may have moved along with movements of the Urazoko Fault.”

The fault is believed to have moved sometime in a period not more than 4,500 years ago.

The layers are “typical” fractured zones created by movements of active faults, said Yuichi Sugiyama, a senior researcher at the National Institute of Advanced Industrial Science and Technology affiliated with the agency.

Researchers on active faults have long pointed out the danger the fractured zones and the Urazoko Fault could pose but Japan Atomic Power said when it applied for building two more reactors in 2004 that Urazoko is not an active fault.

Urazoko was confirmed an active after Takashi Nakata, professor emeritus at Hiroshima University, and others pointed out in 2008 errors in Japan Atomic Power’s research.


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