Confirmed: Higashidori on active faults

December 27, 2012

Panel retains view faults under Tohoku Electric atomic plant active

http://mainichi.jp/english/english/newsselect/news/20121227p2g00m0dm025000c.html

TOKYO (Kyodo) -- A panel of Japan's nuclear regulatory authority concluded Wednesday that geological faults running under Tohoku Electric Power Co.'s atomic power plant in Aomori Prefecture are active, clouding the prospects for the plant's reactivation.

The conclusion was unchanged from what panel members agreed in their previous meeting last week, although Tohoku Electric officials were given an opportunity during Wednesday's meeting to argue that there are no active faults at the site that could undermine the safety of the sole reactor at the Higashidori plant.

"There were no facts that made us correct the recognition we reached earlier," Kunihiko Shimazaki, the head of the panel and a commissioner of the Nuclear Regulation Authority, told a news conference after the meeting.

The seismologist also said that he expects the utility to carry out investigations based on the idea that active faults exist at the plant and evaluate their impact.

The faults in question are not seen to run directly beneath the reactor at the Higashidori complex, but the panel's assessment highlights the difficulty of putting the reactor back online anytime soon as it is necessary to reassess the plant's quake resistance and take measures to reinforce the facilities.

"Even if there were an application (for reactivation) based on a view that there are no active faults, I have to say that is wrong," Shimazaki said.

Tohoku Electric's Executive Vice President Takeo Umeda told a separate news conference that his company has no intention of backing away from its view that the faults are not active and will seek to "enhance its explanation" by conducting further investigation at the site.

The faults judged as active include one called F-3, running vertically through the plant's premises, and another called F-9, located parallel to F-3.

The two have been observed at the southern area of the plant's premises but are known to be stretching toward the northern area close to the No. 1 reactor building and the adjacent land where Tokyo Electric Power Co. plans to build its own Higashidori plant.

In the process of agreeing that the faults are probably active, the members of the panel have pointed to such findings as irregular elevated areas seen in the land form and a section of flat stones found close to a fault surface that they say is a feature of a strike-slip fault.

Tohoku Electric officials tried to counter this view by showing that some fault zones of crushed rocks are found to be consolidated deep underground, suggesting that it is unlikely the faults have moved in recent geological time. But the panel members were not convinced.

The reactor at the Higashidori plant entered commercial operation in December 2005. The plant is the third site that the nuclear regulatory body, launched in September, has sent a panel of experts to in order to check faults suspected to be active.

Another team of experts has already agreed that a fault running directly underneath a reactor at Japan Atomic Power Co.'s Tsuruga plant in Fukui Prefecture is likely to be active, an assessment that could leave the company with no option but to scrap the unit.

A similar team appointed by the regulatory body visited Kansai Electric Power Co.'s Oi plant, also in Fukui Prefecture, for an assessment, but it has not yet reached a conclusion.

________________________

See also :

Tohoku Electric fails to convince NRA that faults are inactive

Kyodo

http://www.japantimes.co.jp/text/nn20121227a4.html

A Nuclear Regulation Authority panel said Wednesday it remains convinced that geological faults running under Tohoku Electric Power Co.'s atomic power plant in Aomori Prefecture are active, indicating the facility's sole reactor cannot be restarted.

The panel reached the same conclusion in an earlier meeting. On Wednesday, however, Tohoku Electric officials were given the opportunity to argue their claim that clay swollen with water was responsible for deformations in geological layers.

"There were no facts that made us correct the recognition we reached earlier," Kunihiko Shimazaki, the head of the panel and an NRA commissioner, told reporters after the meeting.

He also said he expects the utility to evaluate the impact of the faults on the assumption they are active.

Although the faults don't run directly beneath the sole reactor at the Higashidori complex, a reassessment of the plant's quake resistance, as demanded by the panel, will keep the reactor offline for the foreseeable future.

The faults deemed active, including two dubbed F-3 and F-9, run parallel and lengthwise through the plant's premises.

Observed at the southern end of the plant, they are known to stretch to the north, close to the reactor 1 building and to adjacent land that Tokyo Electric Power Co. intended to build its own Higashidori plant on.

The panel members have pointed to irregular elevated areas and other findings that indicate the faults are active.

December 26, 2012

Experts conclude nuclear plant fault assessment

http://www3.nhk.or.jp/daily/english/20121226_28.html

Experts from Japan's Nuclear Regulation Authority say 2 faults under a nuclear power plant in northern Japan may be active.

Their assessment could keep the plant offline for some time.

On Wednesday, one member of the Nuclear Regulation Authority, Kunihiko Shimazaki, and 4 other experts gave their final assessment of an inspection they made earlier this month at the Higashidori plant in Aomori Prefecture.

At a meeting last Thursday, they said 2 fissures under the plant may be active.

At Wednesday's session, plant operator Tohoku Electric Power Company argued that the fissures are not active.
The utility said the faults have hardened deep under the ground and there are no indications they have moved in recent times.

The experts pointed to a lack of evidence substantiating the utility's claim and said the claim is insufficient to declare the fissures not active. They also said the utility's flat denial of the possibility that the faults are active makes them worry about whether it can handle nuclear plants safely.

Shimazaki said his team has found no evidence to contradict the view that the faults are active.

The team will finalize a report on their findings in early January.

Tohoku Electric will have to review its anti-quake measures at the plant, taking into account the presence of active faults within the grounds of the facility.

This is the second case in which experts have found faults under a nuclear plant active. Earlier this month, they determined that faults running underneath the Tsuruga nuclear plant in Fukui Prefecture are active.