Reactors at Japan Atomic Power Co.’s Tsuruga nuclear plant require further seismic review to ensure their safety, according to a team of international experts hired by the company to review its own investigation.
The Tsuruga plant’s Nos. 1 and 2 reactors are susceptible to seismic hazard from the active Urasoko fault, which lies “within a few hundred meters” of the nuclear station, according to prepared remarks by team member Neil Chapman, a professor of environmental geology at the U.K.’s University of Sheffield and a partner with Switzerland-based MCM Consulting.
Japan Atomic, which has Tokyo Electric Power Co. as its largest shareholder, commissioned the group of geology, seismology and nuclear experts to review two reports that the company submitted to Japan’s Nuclear Regulation Authority that found a separate fault directly under the No. 2 reactor wasn’t active.
At stake is the future of Japan Atomic, which may become insolvent if its reactors are found to be too risky to restart. The company will incur 256 billion yen ($2.6 billion) of losses if it decommissions the two reactors at the Tsuruga plant and one at its Tokai Dai-Ni nuclear station, the trade and industry ministry estimated in June 2012.
Chapman endorsed Japan Atomic’s findings, saying it had presented convincing evidence that the fault beneath or near unit No. 2 was not active, contradicting a study approved by the NRA in May that concluded the fault under unit No. 2 was active.
NRA Chairman Shunichi Tanaka said at the time that the findings violated safety regulations, while declining to assert that it meant the regulator would deny safety clearance needed to restart the reactor in western Japan.
The separate Urasoko fault could endanger the plant, which should prompt a review of possible hazards if that fault were to move, Chapman said in his remarks before a briefing today.
“We recommend that the seismic hazard analysis of the NPP should be continually improved and updated with new data and techniques, as they arise,” he wrote, referring to the Tsuruga nuclear power plant. “It should be broadened to include all aspects of seismic hazards.”
Japan Atomic and the NRA did not immediately respond to e-mails seeking comment about the findings.
All but two of Japan’s reactors are idled for safety assessments after the 2011 earthquake and tsunami caused meltdowns and radiation leaks at Tokyo Electric’s Fukushima Dai-Ichi plant. The NRA was set up after the disaster to independently review Japan’s nuclear power industry.