NRA needs more members

January 17, 2013

Experts remain divided over whether Oi plant sits above active fault

http://mainichi.jp/english/english/newsselect/news/20130117p2g00m0dm030000c.html

TOKYO (Kyodo) -- Experts appointed by the Nuclear Regulation Authority remained divided Wednesday over whether an active fault runs under an atomic power plant in western Japan, in a sign that discussions on the matter could be prolonged.

If the five-member panel concludes there is an active fault that could undermine the safety of the Oi plant in Fukui Prefecture, the NRA is likely to ask operator Kansai Electric Power Co. to suspend the Nos. 3 and 4 units at the plant, which are the only operating reactors in the country.

During the discussion, NRA commissioner and panel head Kunihiko Shimazaki tried to come up with a conclusion on whether slips found at a trench in the northern part of the plant's premises are running under important facilities and have the potential to cause damage to the installations.

Of the remaining four panel members invited from outside the NRA, two members opposed viewing the slips as active faults, including Ritsumeikan University professor Atsumasa Okada who reiterated there is a high possibility that a landslide occurred in the area in question. The other two members, however, viewed the slips as possible active faults.

The meeting, which lasted over four hours, wrapped up with Shimazaki saying, "I want (the panel) to further consider the issue because I don't think safety matters have become completely clear."

As the panel failed to reach a conclusion after Kansai Electric enlarged the size of the trench in the northern area of the site, the panel will look into a large-scale trench to be excavated in the southern area during its next investigation.

The next panel meeting will be held in February or later so it can seek advice on whether Kansai Electric's plan to dig the new trench is appropriate, an official of the NRA secretariat said.

The panel started holding meetings from late October, hoping to determine whether a fault called F-6, a zone of crushed rock that runs north-south between the Nos. 1-2 reactors and Nos. 3-4 reactors, is active.

The fault is believed to run under a water channel that would be used to take in seawater to cool reactors in the event of an emergency.

Even if the slips in the northern trench are determined to be active, whether they are part of the F-6 is unknown because the panel has not been able to grasp the exact location of the F-6.

The official said that the NRA wants to study the location of the F-6 fault through data taken during boring surveys.

With the discussion becoming prolonged, Okada, a 70-year-old expert on active faults, expressed his strong frustration over the handling of the issue during the meeting. He complained that the panel needs to add more members, such as an expert on fault fracture zones, [why haven’t they included one?]and that the workload is too heavy for "an old man."