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Kashiwazaki may also be sitting on active faults

January 24, 2013


Quake faults at TEPCO's Niigata nuclear power plant may be active



TOKYO (Kyodo) -- Some faults under Tokyo Electric Power Co.'s Kashiwazaki-Kariwa nuclear plant, the world's biggest on Japan's northwest coast, could be regarded as active based on new safety standards, Kyodo News found Wednesday through documents that the utility has made public and other materials.

If the faults are judged as likely active by the Nuclear Regulation Authority, established in the wake of the 2011 Fukushima Daiichi complex disaster, the utility will face difficulties in reactivating the plant in Niigata Prefecture.

Under Japanese government criteria, active faults are defined as those that have moved in the last 120,000 to 130,000 years. But the NRA plans to move the benchmark to 400,000 years ago in the new safety standards, which are expected to come into force in July.

The draft standards presented by the NRA on Tuesday stated that nuclear power plant operators would not be allowed to build reactors directly above active faults.

The utility known as TEPCO, the operator of the crippled Fukushima plant, is currently conducting a geological survey of the faults running under the Kashiwazaki reactors with a combined output capacity of 8,212,000 kilowatts.

The NRA said it will decide whether to conduct its own investigation after the outcome of the survey becomes clear.

According to TEPCO, two faults called "alpha" and "beta" are located below the Nos. 1 and 2 reactors. Faults are also located under the Nos. 3 and 5 to 7 reactors.

The No. 4 reactor does not sit directly above a fault, but there are some under the adjacent reactor turbine building.

TEPCO has denied the faults are active under existing guidelines, but, for example, the beta fault could be categorized as active under the new definition because it has displaced a ground layer including volcanic ash dating back 240,000 years.

The NRA is conducting, or plans to conduct, investigations into six nuclear facilities in Japan that are suspected to have suspicious faults on their premises, but the Kashiwazaki-Kariwa plant is not among them.

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