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The Tsuruga 'series' continues

December 10, 2012

Tsuruga nuclear power plant may be on active fault



Japan's Nuclear Regulation Authority has determined that faults running underneath the Tsuruga nuclear power plant in Fukui Prefecture are active.

The NRA Chairman Shunichi Tanaka said the body cannot give a permit to restart the plant's reactors, which have been off-line since last year's nuclear accident at the Fukushima Daiichi power plant.

This comes after NRA official Kunihiko Shimazaki and 4 other experts carried out an on-site inspection earlier this month to see whether crush zones under the Tsuruga plant are actually active faults.

The Tsuruga plant sits near the major Urasoko Fault. The team conducted a boring survey on Urasoko Fault and a fault called the D-1. The D-1 Fault branches out from Urasoko and runs directly beneath the Number 2 reactor.

The experts said the Urasoko Fault is active and its possible impact on the fault under the plant in the event of an earthquake cannot be overestimated.

They said that the stratum deformation found near the D-1 Fault was caused by forces similar to those that cause the Urasoko Fault to move.

State regulations prohibit building nuclear reactors above active faults. Tanaka expressed readiness to convene a NSA meeting to hear opinions of members on what to do.

Tsuruga nuclear plant may have to be decommissioned as active fault found





Japan Atomic Power Co. may have to decommission one of its reactors after seismologists concluded the plant is sitting over an active faultline, potentially the first permanent shutdown of a nuclear unit in Japan since the Fukushima disaster last year.

"There is no way we can carry out safety assessments for a restart," the chairman of Japan's Nuclear Regulation Authority (NRA), Shunichi Tanaka, said on Dec. 10 at an open meeting after being presented with an assessment there is an active fault under the No. 2 reactor at the Tsuruga nuclear plant.

The government in Japan, one of the world's most seismically active countries, does not allow nuclear plants to be situated over active faultlines. An NRA panel of seismologists has been reviewing geological records and this month visited Tsuruga to watch the results of boring and other tests.

A fault line extending from below the reactor was assessed to have moved in the past in tandem with another nearby fault, Kunihiko Shimazaki, an NRA commissioner who led the seismic panel, told the meeting.

While Tanaka has no authority to order a permanent shutdown, his comment implies he will not allow the reactor to be restarted, forcing a decision on Japan Atomic over whether to mothball the unit.

A Japan Atomic official who attended the meeting said the company would carry out further seismic studies.

The agency will meet at a later date to make an official announcement on the 1,160 megawatt reactor, the larger of two at the plant in western Japan. The No. 2 unit started operating in 1987, while the 357-megawatt No. 1 reactor started in 1970.

The NRA is reviewing possible faultlines under or near Tsuruga and five other nuclear stations as part of moves to beef up safety and Tanaka has said any reactors sitting above won't be allowed to restart.

All but two of Japan's nuclear reactors are idled for safety checks after the Fukushima disaster, forcing the country to spend billions of dollars extra on fossil fuels to run power stations.

An earthquake and tsunami in March last year knocked out cooling and power at Tokyo Electric Power Co.'s Fukushima No. 1 plant north of the Japanese capital, causing the biggest release of radiation since Chernobyl in 1986.


See also : in the Japan Times


Monday, Dec. 10, 2012

Fault under reactor at Tsuruga likely active



in the Yomiuri

Fault running under Tsuruga plant reactor likely to be active: panel



December 9, 2012


Active fault under Tsuruga nuclear power plant



Japan's Nuclear Regulation Authority and other experts will hold discussions Monday on whether another active fault exists beneath the Tsuruga nuclear power plant in Fukui Prefecture.

The Tsuruga nuclear plant is the only one in Japan that has an active fault running beneath it.

If another fault underneath the plant's reactors is determined to be active the plant will be barred from restarting.

Regulation Authority official Kunihiko Shimazaki and 4 scientists examined the plant on the Japan Sea coast on December 1st and 2nd.

They conducted a so-called trench survey by digging into the ground beneath the compounds to examine the active Urasoko Fault and those branching out from it.

They confirmed that the Urasoko Fault is active. They also found stratum deformation near another fault, called D-1, which runs directly beneath the Number 2 reactor.

Shimazaki said his team shared the view that the deformation was caused by a force similar to the one that caused the Urasoko Fault to move.

Government's guidelines prohibit building a key nuclear power facility on an active fault.

Monday's meeting is drawing attention as the Number 2 reactor may have to be scrapped. That will depend on the assessment reached by the Nuclear Regulation Authority and the experts.





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