NRA starts checking for active faults at Tsuruga plant

December 1, 2012

Vulnerability of two units probed

NRA begins Tsuruga fault investigation

Kyodo

http://www.japantimes.co.jp/text/nn20121201x1.html

Experts appointed by the Nuclear Regulation Authority started a field survey Saturday to check for active faults running directly beneath the two reactors of the Tsuruga nuclear plant in Fukui Prefecture.

The NRA fears that the major active Urazoko fault, which already has been confirmed to lie only 250 meters away from the reactor buildings, could trigger smaller faults underneath the two units if it were to shift.

Past investigations have suggested that several faults running underneath reactors 1 and 2 extend from the Urazoko fault, raising fears about another disaster on the scale of the Fukushima meltdowns. If the NRA decides the reactors were constructed above faults that could move in the future, Japan Atomic Power Co. would likely be prevented from ever restarting them and could be forced to decommission the two units.

The Tsuruga plant, on the Sea of Japan coast, is the second nuclear complex the NRA has targeted for such an on-site investigation, following surveys at Kansai Electric Power Co.'s Oi power station in the same prefecture. The NRA has yet to reach a conclusion on whether faults detected at the Oi facility are active and what degree of danger they pose.

The Tsuruga plant's No. 1 unit started operations in 1970, making it the oldest of Japan's 50 commercial reactors. But it was not until 2008 that Japan Atomic Power confirmed that the Urazoko fault, part of which runs beneath the facility, was active.

The investigative team consists of NRA Commissioner Kunihiko Shimazaki, a seismologist and four other nuclear experts.

NRA Chairman Shunichi Tanaka said earlier that Japan Atomic Power will find it difficult to bring the reactors back online if an active fault is found to run beneath them.

"The existence of the active (Urazoko) fault raises serious concerns. And I can't imagine what kind of measures could be taken (by the company) for the safe operation of the two reactors" if it is found to be connected to faults running directly underneath them, Tanaka said.

When asked how long Japan Atomic Power could be prohibited from resuming operations at the plant in such an event, Tanaka said it might have to wait "until the active fault is gone" — suggesting the reactors would probably have to be scrapped.

Experts start investigation at Tsuruga plant over active faults

http://mainichi.jp/english/english/newsselect/news/20121201p2g00m0dm007000c.html

TOKYO (Kyodo) -- Experts appointed by Japan's nuclear regulatory body on Saturday started a field survey to check whether active faults are running directly underneath the reactors of Japan Atomic Power Co.'s Tsuruga plant on the Sea of Japan coast.

With a major active fault called Urazoko already confirmed to be located at about 250 meters from reactor buildings, it is feared that other faults running underneath the reactors could move in conjunction with the Urazoko fault.

If the Nuclear Regulation Authority decides that the reactors are sitting above faults that could move in the future, the plant's Nos. 1 and 2 reactors are unlikely to be allowed to resume operation and may be scrapped.

The Tsuruga plant in Fukui Prefecture is the second location where the NRA has chosen to conduct an on-site investigation of faults following Kansai Electric Power Co.'s Oi plant in the prefecture. The NRA has not reached a conclusion on whether faults at the Oi plant are active.

The Tsuruga plant's No. 1 unit started commercial operation in 1970, making it the oldest unit among the country's 50 commercial reactors. But it was not until 2008 that the Urazoko fault, part of which runs under the plant, was confirmed to be active by Japan Atomic Power.

Several other faults running underneath the two reactors appear to be extending from the Urazoko fault, raising concerns that safety could be undermined.

The investigative team consists of NRA Commissioner Kunihiko Shimazaki, a seismologist, and four other experts recommended from academic circles. Investigations may continue Sunday.

NRA Chairman Shunichi Tanaka said earlier that the power company would likely face difficulty putting the reactors back online if an active fault is found.

"The existence of an active fault brings about serious concerns. And I can't imagine what kind of measures can be taken for (the operation of) the reactors that are already installed," he said.

Tanaka also suggested that the power company may end up decommissioning the reactors, saying, "When asked the question of how long the company will not be allowed to resume operations, it may be until the (active) fault is gone."

Japan has been reviewing the risks that could be posed by active faults in the wake of the nuclear crisis at Tokyo Electric Power Co.'s Fukushima Daiichi complex, which was triggered by a huge earthquake and tsunami on March 11, 2011.

Of the 50 commercial reactors in Japan, only two reactors at the Oi plant are currently online