Fault risk at Higashidori plant

December 15, 2012

Regulators: Faults beneath Higashidori nuclear plant likely active

http://ajw.asahi.com/article/0311disaster/fukushima/AJ201212150032

THE ASAHI SHIMBUN

Fault lines beneath the Higashidori nuclear power plant in Aomori Prefecture may be active, Nuclear Regulation Authority experts said on Dec. 14.

The announcement was made the same day the industry watchdog completed its two-day on-site survey of the plant, which is operated by Tohoku Electric Power Co. Another nuclear plant that carries the same name is under construction in Higashidori by Tokyo Electric Power Co.

Experts on the NRA's five-member panel told a post-survey news conference that they believed that shifts in geological formations across the fault lines being studied represent activity during the past 100,000 years.

The movements may have been induced by slippage along an active fault that lies elsewhere, but it cannot be ruled out that the surveyed faults are themselves seismically active, according to the panel members.

"There is repeated activity," said Hiroshi Sato, a professor of structural geology at the University of Tokyo. "I believe the faults are active."

NRA Deputy Chairman Kunihiko Shimazaki, who heads the panel, said the opinions of the panel members are "looking toward the same direction."

They are scheduled to meet on Dec. 20 in Tokyo to officially conclude whether the fault lines are active. An assessment that they are active would make it difficult to restart the nuclear reactor at the plant in the near future.

(This article was written by Ryuta Koike and Yu Kotsubo.)

Fault risk for Aomori nuclear plant is raised

http://www.japantimes.co.jp/text/nn20121215a1.html

Jiji

HIGASHIDORI, Aomori Pref — Earthquake faults beneath the Higashidori nuclear power plant in Aomori Prefecture could be active and dangerous, a regulator said Friday.

Nuclear Regulation Authority Commissioner Kunihiko Shimazaki made this revelation at a press conference after a two-day on-the-spot survey of the plant, which currently has one Tohoku Electric Power Co. reactor but, according to plans, will have another one built for the utility as well as two constructed for and run by Tokyo Electric Power Co.

Shimazaki and other survey participants will meet Thursday to consider the results of their probe.

If the regulators suspect the faults are active, it may be difficult for Tohoku Electric to restart the now-offline reactor amid safety concerns stemming from the triple-meltdown disaster at Tepco's Fukushima No. 1 power plant.

The experts Thursday confirmed four crush zones, including those running near the reactor 1 building. They continued the survey Friday to determine when the zones moved and find out whether there is any possibility they will move again.

Tohoku Electric has offered the explanation that fault slips under the plant site are caused by changes in groundwater levels.

But Shimazaki said Thursday he can't accept that explanation.

Survey team member Yota Kumaki, a professor at Senshu University, said the same day Tohoku Electric's claim raises many questions.

Another team member, Hiroshi Sato, a professor at the University of Tokyo, said he can't understand on what grounds the company drew such a conclusion.

Tohoku Electric maintains there are no active faults beneath the plant and thus there are no safety concerns.

The plant is the third nuclear power station to be inspected by the NRA for possible active faults, following Kansai Electric Power Co.'s Oi plant and Japan Atomic Power Co.'s Tsuruga plant, both in Fukui Prefecture. None of the earlier probes has reached a conclusion.

Following the latest survey, the agency plans to conduct on-site fault studies at Hokuriku Electric Power Co.'s Shika plant in Ishikawa Prefecture, Kepco's Mihama plant and the Japan Atomic Energy Agency's Monju fast-breeder reactor, both in Fukui.

Regulator suggests active faults beneath Higashidori nuclear plant

http://mainichi.jp/english/english/newsselect/news/20121215p2g00m0dm021000c.html

AOMORI, Japan (Kyodo) -- A Japanese nuclear regulator Friday suggested that earthquake faults beneath the Higashidori nuclear power plant site in Aomori Prefecture could be active and dangerous.

Nuclear Regulation Authority Commissioner Kunihiko Shimazaki made the suggestion at a press conference after a two-day on-the-spot survey of the plant site owned by Tohoku Electric Power Co.

Shimazaki and other survey participants will meet next Thursday to consider the survey results.

If they suspect the faults are active, it may be difficult for Tohoku Electric to restart the plant now left offline amid safety concerns after the March 2011 Fukushima Daiichi nuclear plant.

The Higashidori plant has one reactor with another reactor being planned. The reactor entered commercial operation in December 2005 and suspended operation for regular checkups in February 2011.

The second reactor construction plan has been left uncertain since the Fukushima accident.

Tokyo Electric Power Co. has a plan to build two rectors at a site neighboring the Higashidori plant. Construction of the first started in January 2011 and has been suspended since the Fukushima accident.

Shimazaki also indicated that the TEPCO plan could be affected because the faults beneath the Higashidori plant site stretch to the planned TEPCO plant site.