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Oi : Third inspection

July 27, 2013



Japan nuke plant checked again for active earthquake fault
  • JIJI 

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.

Expert team studies fault at Ohi plant



Japan's nuclear regulator began a 2-day survey of a fault running beneath the nuclear plant in Ohi, Fukui Prefecture, on Saturday.

Scientists and a team from the Nuclear Regulation Authority examined the geology of a trench that was dug near the plant's Number 3 reactor to decide if the fault is active.

The NRA had already conducted 2 inspections since last November. Opinion remains divided on the status of the fault that runs from north to south on the plant's premises.

In the 3rd survey that began on Saturday, the team studied strata of the wall and the fault found on the bottom of a newly dug trench to the south of the Number 3 reactor.
The trench is about 70 meters long and 40 meters deep.

Nuclear Regulation Authority Commissioner Kunihiko Shimazaki said it will not make a judgment right away but will examine the findings in a meeting.

The survey will continue on Sunday.

The fault in question runs beneath pipes that carry sea water to cool the reactors.

The number 3 and 4 reactors may be shut down if the fault is determined to be active. The plant's operator, Kansai Electric, maintains that it is inactive.

The Regulation Authority conducted a safety check of the 2 reactors based on Japan's new guidelines, and gave permission for the utility to keep them online until a safety inspection scheduled for September.

Kansai Electric is applying for safety checks with the aim of continuing operations after September's inspection, but the Regulation Authority has decided not to conduct an assessment until a conclusion is reached on the status of the fault.
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