Last week's powerful earthquake in central Japan stressed parts of a local nuclear power plant to the extent that the limit set in the plant's design was exceeded, according to a report released at a meeting of the safety panel on Wednesday.
The report, discussed at a regular meeting of the Nuclear Regulation Authority, noted that the potentially alarming ground acceleration readings did not appear to pose an immediate safety threat to the Shika facility on the Noto Peninsula.
File photo taken in December 2023 shows Hokuriku Electric Power Co.'s Shika Nuclear Power Plant in Shika, Ishikawa Prefecture, central Japan. (Kyodo) ==Kyodo
The magnitude 7.6 quake struck the power plant as the agency, a government subsidiary, was reviewing planned safety measures to reactivate one of the two reactors operated by Hokuriku Electric Power Co. Both were offline when the quake struck on New Year's Day.
According to the weather agency, the quake reached a maximum of 7 on the country's seismic intensity scale in Shika, Ishikawa Prefecture on the Sea of Japan coast.
During Wednesday's meeting, Akira Ishiwatari, a geologist who studies earthquake-related issues on the panel, said: “Since the recent quake had a huge impact, we need to rely on experts' research when reviewing safety measures in the future.”
Shinsuke Yamanaka, the agency's chief, told reporters that such seismic research by experts could take years and that activity on underwater faults that triggered the latest quake would need to be taken into account “as new findings” when updating safety standards.
Yamanaka, an expert in nuclear energy technology, also called on the operator to investigate the failure of the electrical transformers in reactors No. 1 and 2, which has left the Shika power plant partially unable to receive electricity from outside sources.
Hokuriku Electric said the plant could continue to cool used fuel even after the recent quake.
Nobuhiko Ban, another panel member and an expert on radiation protection, called it a “huge problem” that radiation levels at some sites near the Shika plant were not monitored in real time after the quake and slammed the effort of aircraft and drones for purpose.
Nuclear power plant operators in Japan have shut down many reactors in recent years while improving emergency power procurement systems following reactor meltdowns at the Fukushima-Daiichi complex due to a complete blackout following the March 2011 quake and tsunami.
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