The Nuclear and Industrial Safety Agency on April 25 decided to raise ground motion projections to be used in the anti-seismic design of the suspended Kashiwazaki-Kariwa nuclear power plant in Niigata Prefecture.
The decision came after Tokyo Electric Power Co., the operator of the Kashiwazaki-Kariwa plant, told NISA that calculations taking into account two or more sliding inland fault lines in a seismic event produced ground motions in excess of previous estimates, which had only considered one sliding fault.
TEPCO will recalculate, on the basis of the new results, whether the equipment at the nuclear plant will be able to withstand the projected seismic shocks.
TEPCO officials said the utility will reinforce, as required, exhaust stacks and other equipment that may be affected by shocks exceeding the earlier projections.
NISA plans to consider the seismic risks of nearby active fault lines beneath the seabed as well.
According to a new business plan to be submitted to the government on April 27, TEPCO is hoping to bring the Kashiwazaki-Kariwa plant back online by the end of fiscal 2013. The last operating reactor at the plant, Unit 6, was shut down on March 25 for regular maintenance.
In March, NISA ordered the operators of nuclear power plants and other nuclear facilities that lie close to more than one active fault to submit evaluations based on the assumption of multiple fault lines slipping together.
In that context, NISA has so far decided to raise the ground motion projections for three nuclear power plants, including the Tsuruga nuclear plant in Tsuruga, Fukui Prefecture, and the Monju prototype fast breeder reactor, also located in Tsuruga.
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