information about Fukushima published in English in Japanese media info publiée en anglais dans la presse japonaise
11 Décembre 2012
http://ajw.asahi.com/article/behind_news/social_affairs/AJ201212110030
Japan Atomic Power Co. may have to decommission one of its reactors after seismologists concluded the plant is sitting over an active fault line, potentially the first permanent shutdown of a nuclear unit in Japan since the Fukushima disaster last year.
A panel of seismologists and geologists with Japan's Nuclear Regulation Authority (NRA) has been reviewing geological records and this month visited the Tsuruga nuclear power plant to watch the results of drilling and other tests.
"There is no way we can carry out the safety assessments (that are required) for a restart," the chairman of the NRA, Shunichi Tanaka, said on Dec. 10 at an open meeting after being presented with the panel's assessment that there is an active fault under the plant's No. 2 reactor.
The government in Japan, one of the world's most seismically active countries, does not allow nuclear plants to be situated over active fault lines.
But about 160 geological fault lines cut across the premises of the Tsuruga nuclear power plant, including some that lie directly beneath its two reactor buildings. In addition, the Urasoko fault, which is active, runs about 200 meters east of the reactor buildings.
Much attention has been given to whether the fault lines situated directly beneath the reactor buildings could slide in tandem with the Urasoko fault when the latter shifts.
A fault line called D-1, situated directly beneath the No. 2 reactor building, was assessed to have moved in the past in tandem with the Urasoko fault and thus likely active, according to Kunihiko Shimazaki, deputy chairman of the NRA and head of the seismic panel.
"You could call it an active fault," Shimazaki told reporters after the Dec. 10 meeting. "It likely represents simultaneous movement induced by the motion of the Urasoko fault."
The experts intensively studied the vicinity of the point where the D-1 fault branches out from the Urasoko fault during an on-site survey on Dec. 1-2. The survey revealed a new fault line near D-1, and the experts agreed that the fault line was formed under approximately the same stress that drives the activity of the Urasoko fault. The panel concluded that future slippage along that fault line could not be ruled out.
Though 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 results of the Dec. 10 expert panel meeting will be presented to a regular meeting of the NRA on Dec. 12, when the agency may 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 fault lines under or near Tsuruga and five other nuclear plants 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 tens of billions of yen 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.
THE ASAHI SHIMBUN AND WIRE REPORTS
Utility yet to decide on scrapping Tsuruga reactor
http://www3.nhk.or.jp/daily/english/20121211_35.html
The operator of the Tsuruga nuclear power plant on the Sea of Japan coast says it has not decided whether to decommission one of the facility's reactors.
The Nuclear Regulation Authority said in an assessment meeting with experts on Monday that a fault directly under the Number 2 reactor is likely active. The assessment could lead to decommissioning of the reactor. Government guidelines prohibit building key nuclear power facilities above active faults.
Speaking to reporters on Tuesday, officials of Japan Atomic Power Company said it is studying what would make decommissioning unavoidable. They said the utility will consult other energy firms that buy power from it, as the matter could affect plans to raise electricity rates.
The utility's Vice President Hiroshi Masuda said it will provide a scientific explanation to the authority to win its approval for restarting the reactor.
Dec. 11, 2012 - Updated 11:58 UTC (20:58 JST)
N-plant operator questions regulator's assessment
http://www3.nhk.or.jp/daily/english/20121211_31.html
The operator of the Tsuruga nuclear power plant on the Sea of Japan coast has asked a nuclear regulator to explain its assessment that faults running under one of the facility's reactors may be active.
Japan Atomic Power Company on Tuesday sent an open letter to the Nuclear Regulation Authority, saying its assessment is beyond comprehension.
On Monday, an NRA expert panel concluded that so-called crush zones under the Number 2 reactor of the plant in Fukui Prefecture may be active faults.
The firm asked the authority why it concluded that the nearby active Urasoko fault and a fault called D-1 that runs beneath the reactor could move together.
The company's Vice President Hiroshi Masuda said he understands that the authority makes judgments based on science, and that he hopes it will provide scientific responses.
A senior official of the NRA secretariat says the authority will examine the letter and respond.
Government guidelines prohibit building key nuclear power facilities over active faults. If fissures lying beneath the Tsuruga plant's reactor are officially determined to be active, the plant may have to be scrapped.
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