OI, FUKUI PREF. – Prime Minister Shinzo Abe appears at a news conference in Manila on Saturday..”. | KYODOInspectors from the Nuclear Regulation Authority on Saturday started their third on-site survey o check for active faults beneath the Oi nuclear power plant in Fukui Prefecture.
The only two reactors in Japan currently online are located at this plant.
NRA experts conducted inspections at the Kansai Electric Power Co. plant in November and December.
The NRA has given permission to Kansai Electric to continue operating the two reactors — units 3 and 4 — until a mandatory inspection begins in September.
Members of the inspection team are split over whether there is an active fault underneath the plant. In the current inspection, to be carried out through Sunday, the inspectors will check a test trench that Kansai Electric newly dug south of reactor 3.
Earthquake guidelines for nuclear plants ban the construction of crucial facilities above an active fault.
The experts are focusing on whether a crush zone known as F-6 is an active fault. The F-6 crush zone, a fractured area in bedrock, runs more than 650 meters beneath a seawater intake channel for emergency cooling for both reactors 3 and 4.
Because Kansai Electric does not know the exact location of F-6, the NRA directed the company to drill the additional test trench.
The NRA may order the two reactors to be shut down before the the periodic checkups if it concludes that the F-6 crush zone is an active fault, officials said.
Kansai Electric has applied for the NRA to screen the two reactors under new safety standards introduced in early July, which is a prerequisite for restarting the reactors following the regular inspection.
The NRA will not begin the screening before reaching a conclusion on the fault survey.