The Nuclear and Industrial Safety Agency on June 19 told Chugoku Electric Power Co. that its maximum estimate for an earthquake striking around the Shimane nuclear power plant is too low.
At a NISA meeting of experts, the utility revealed the possibility of three active faults on the western side of the nuclear plant in Matsue moving together along a stretch of 51.5 kilometers. That event could trigger a short-period earthquake of a strength for which the utility is not prepared, leading to possible damage to key equipment at the plant.
Under NISA’s instructions, Chugoku Electric will review its estimates for possible earthquakes. If it concludes that a larger earthquake could damage equipment at the Shimane nuclear plant, it will be required to take additional quake-resistance measures.
The meeting was held to show the results of re-evaluations of faults around the nuclear plant.
A similar situation arose earlier this year when studies found that active faults with a total length of about 100 kilometers could move together near the Tsuruga nuclear power plant in Fukui Prefecture.
In May, NISA instructed Japan Atomic Power Co., operator of the Tsuruga plant, to review its estimates for earthquakes in the area.
On June 19, Japan Atomic Power said it will implement research by November on possible earthquakes caused by simultaneous movements of the active faults.
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