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NRA will conduct on-site survey at Tsuruga plant

November 14, 2012


Date set for fissure survey at Fukui nuclear plant



Japan's Nuclear Regulation Authority will examine fissures beneath the Tsuruga nuclear plant in Fukui Prefecture to determine whether the cracks are active faults.

NRA officials will conduct the survey with 4 outside experts on December 1st and 2nd.

A meeting to assess the results of the investigation is scheduled for December 10th. If any of the fissures are judged to be an active fault, the NRA will prohibit the restart of the plant's No.1 and No.2 reactors.

Experts who surveyed the Tsuruga plant in April found that one of the fissures could be linked to an active fault that runs through the compound.

They also said another fissure directly below the No.2 reactor could be an active fault.

The NRA will conduct on-site surveys at 6 nuclear plants across Japan to investigate whether fissures beneath them are active faults.

The agency carried out its first survey at Ohi plant, also in Fukui Prefecture, earlier this month. It instructed the plant's operator to conduct a further examination.

NRA to check ground under Tsuruga plant

The Nuclear Regulation Authority has decided to conduct an on-site investigation to check whether the crush zone beneath reactor buildings at Japan Atomic Power Co.'s Tsuruga nuclear power plant in Fukui Prefecture is an active fault on Dec. 1 and 2.

If the authority judges the zone to be an active fault, it plans to decide against approving the restart of the plant's two idled reactors.

This investigation is the second of its kind for the authority following one on Nov. 2 at Kansai Electric Power Co.'s Oi nuclear plant in the prefecture. The authority could not reach a conclusion in that probe and asked KEPCO to conduct further investigation. As observers said a final decision would thus inevitably be considerably delayed, attention has been focused on how the authority would tackle other investigations.

As the one-day investigation in Oi was insufficient, the authority's investigation at the Tsuruga plant will be for two days. The Tsuruga plant has a certain amount of geological data collected through Japan Atomic Power Co.'s own research, so the authority intends to use the Tsuruga investigation as a model case to enhance discussion regarding other plants, including Oi.

The active fault problem occurred after the former Nuclear and Industrial Safety Agency comprehensively checked the evaluation of quake-resistance at plants following the Great East Japan Earthquake. Experts at a NISA hearing suggested that the crush zone beneath reactor buildings at the Tsuruga plant could move in conjunction with the active Urasoko Fault nearby.

Nuclear regulators set 2nd field survey destination at Tsuruga plant



TOKYO (Kyodo) -- Japan's nuclear regulatory body on Wednesday selected the Tsuruga plant in Fukui Prefecture as its second destination to conduct a field survey to check faults that could undermine the safety of atomic power stations.

According to a plan unveiled the same day, the Nuclear Regulation Authority said it will send a team of experts to the plant owned by Japan Atomic Power Co. on Dec. 1, and if necessary also on Dec. 2. The plant's two reactors are offline.

At the Tsuruga plant, faults running directly underneath its two reactors are feared to move in conjunction with an active fault called Urazoko, which is located about 250 meters from the reactor buildings.

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

If the NRA decides that the reactors are sitting above active faults, the two reactors will not be allowed to resume operation and could be scrapped.

The Tsuruga plant's No. 1 reactor started commercial operation in 1970, but it was not until 2008 that the Urazoko fault, part of which runs under the plant's premises, was confirmed to be active.

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.

The NRA, launched in September, conducted its first on-site inspection at Kansai Electric Power Co.'s Oi plant in Fukui Prefecture earlier this month.

But a team involved in the investigation has yet to reach a conclusion on whether faults found there can be regarded as active.

Of the 50 commercial reactors in Japan, only two reactors at the Oi plant are currently online amid strong public concerns over the safety of nuclear power.


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