Japan Nuclear Plant Atop Likely Active Quake Fault

From USA Today

By  Michael Winter

An earthquake fault under a nuclear plant in western Japan is “highly likely” active, meaning the two-reactor facility will probably be closed permanently, a panel of experts reported Monday.

The draft report on the Tsuruga generating station, in Fukui prefecture, was commissioned by the country’s Nuclear Regulation Authority. The panel discovered in December that Unit 2 sits atop a “crush zone” of small rocks and sediment that could move with a major fault, the Urazoko, which lies just 600 to 1,000 feet from the reactors.

“If new knowledge is obtained, the judgment could be reviewed. However, at least at this point, the fault at the plant site is highly likely an active fault that needs to be considered in terms of seismic design,” the report said, according toThe Japan Times.

A fault is defined as being active if it has moved within the past 120,000 to 130,000 years, though regulators are planning to extend that back to 400,000 years. Last week, the NRA tightened a safety “guideline” by expressly forbidding the industry from putting reactors or cooling equipment on active faults.

A 2010 seismic safety symposium evaluated the hazard the Tsuruga plant faced because of its proximity to the Urazoko fault.

The Tsuruga station is owned by Japan Atomic Power Co., a consortium of Japanese utilities that includes the operator of the Fukushima plant damaged by the March 2011 earthquake and tsunami. Unit 2 opened in 1987, and Unit 1 in 1970.

The NRA already plans to not allow any plant older than 40 years to operate, all but dooming Unit 1 and Japan Atomic’s plans to build two more reactors.

Japan Atomic Power has objected to the findings, saying they lack “scientific support.” The utility can appeal to the NRA.

Monday’s report comes 10 days after the five-member panel could not agree on whether the nearby, four-reactor Oi nuclear power plant also sits on a similar active fault. In November, experts inspected the fault, which cuts between Units 1 and 2 on a bluff above the Sea of Japan.

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