NRA experts agree fault under Tsuruga plant active – Japan Atomic Power calls outcome “totally unacceptable” and vows to counter assessment

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The team of experts from Japan’s Nuclear Regulatory Authority has agreed that a fault running underneath the Tsuruga nuclear power plant is likely active, an assessment which would prevent the utility from restarting the nuclear reactors.

The Tsuruga nuclear power plant is one of the oldest in Japan, with the Unit 1 reactor starting commercial operation in 1970 and the Unit 2 reactor in 1987.  The utility which operates the Tsuruga plant, Japan Atomic Power, did not acknowledge the Urazoko fault was active until 2008.



The major fault line, the Urazoko fault, was found to be running just 250 meters from the two reactor buildings in 2008.

But what really upset local residents were the several smaller faults extending from the main Urazoko fault, one of which runs directly under Unit 2’s reactor.

Source: Wall Street Journal


Even after admitting the presence of the fault, the utility continued to operate the nuclear power plant, and downplayed the possibility of smaller faults moving in tandem with the Urazoko fault.

The NRA team of experts not only confirmed that the Urazoko Fault was active, but also found stratum deformation near another fault (D-1 fault), which runs directly from the Urazoko fault  underneath the Unit 2 reactor.

Regulation Authority inspecting official Kunihiko Shimazaki said his team agreed that the deformation was caused by a force similar to the one that caused the Urasoko Fault to move, and has likely moved as an active fault in the past together with the movement of the Urazoko fault.

NRA Chairman Shunichi Tanaka, said he feels the authority could not allow the restart of the reactors, because they “cannot implement safety assessments for the resumption (of the plant) in the current situation.”  While Tanaka has no authority to order a permanent shutdown of the units, his comments imply he will not allow the reactors to restart.

“All the panel is saying is that the fault could be an active one. That means they are arguing that it is equally possible that the fault is inactive,” said Hiroaki Koide, a nuclear reactor engineer at Kyoto University. “I suspect there is still a good chance of the reactor getting restarted in the future.”

Japan Atomic Power said in a statement that the outcome was “totally unacceptable” and vowed to continue an additional investigation on the plant’s premises, apparently to counter the assessment which likely will leave the utility with no alternative other than decommissioning the nuclear reactors onsite.

The central government’s top spokesman, Chief Cabinet Secretary Osamu Fujimura, stressed that steps need to be taken before any final decision. “We shouldn’t make any predictions at this stage,” he said.

Source: Kyodo News

Source: The Japan Times

Source: The Asahi Shimbun

Source: Yahoo News

Source: NHK

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