The operator of the Tsuruga nuclear plant in Fukui Prefecture is rejecting the finding of a team of experts Monday that an earthquake fault under the plant precludes the restart of one of its reactors.
Japan Atomic Power Co. said the conclusion is “totally unacceptable,” noting the experts focused largely on geological formation data and not other aspects, and vowed to continue an additional probe on the plant’s premises to counter the assessment.
But Kunihiko Shimazaki, the Nuclear Regulation Authority commissioner who led the team, said at a news conference they had “reached a decision based on the data we have now” and there is no need for the company to carry out further studies.
It is the first time that a panel under the newly launched NRA has concluded that an existing reactor may be sitting directly above an active fault, a situation banned by safety screening guidance for nuclear power stations.
The NRA will release its own judgment based on the outcome of the experts’ discussions Monday, but NRA Chairman Shunichi Tanaka, who attended the meeting, said he feels the authority “cannot implement safety assessments for the resumption (of the plant) in the current situation.”
Some local residents were stunned by the NRA-led team’s conclusion. Tsuruga Mayor Kazuharu Kawase said the outcome was “very tough,” but added it is possible safety could be confirmed through additional studies.
It has been known for years that a major active fault, called Urazoko, lies about 250 meters from the reactor buildings. But the focus of the latest discussions has been on whether another fault called D-1, with a zone of crushed rock, located beneath the No. 2 reactor could move in conjunction with the Urazoko fault.
The experts agreed that what appears to be an extended section of D-1 had moved as an active fault in the past, together with the movement of the Urazoko fault, Shimazaki said in wrapping up the meeting.
The extended section of D-1 falls within the definition of an active fault Shimazaki thinks appropriate, which is a fault that has moved in the last 400,000 years.
He also said the experts took into consideration the fact that a large fault like Urazoko exists on the premises of the plant.
“If plant operators know there is an active fault at the site in the first place, they will usually not build (a nuclear complex) there,” Shimazaki added.
The Tsuruga plant has two units, with reactor 1 starting commercial operation in 1970 and reactor 2 in 1987. But it was not until 2008 that the Urazoko fault was confirmed to be active by Japan Atomic Power.
Another NRA-appointed team has already visited the Oi plant to check for faults, but it has not yet reached a conclusion. The NRA plans to send similar teams of experts to at least four other facilities around the country.