Nuclear regulation body detects active fault under Tsuruga reactor

要約

A five-member team of the Nuclear Regulatory Authority decided Dec. 10 that there is a strong possibility that a “crush zone” of small rocks and sediment running beneath the No. 2 reactor of Japan Atomic Power Co.‘s Tsuruga nuclear power plant is an active fault. The team’s conclusion is based on a two-day on-site geological survey as well as examination of data provided by the operator of the plant.

On the basis of the team’s decision, Mr. Shunichi Tanaka, head of the NRA, said, “At this point, we cannot conduct safety checks to clear the restart of the Tsuruga reactors.”

The decision means that it has become extremely difficult for Japan Atomic Power to restart the No. 2 reactor as well as the plant’s No. 1 reactor, which is near the No. 2 reactor. The No. 1 reactor, which started commercial operation in March 1970, is Japan’s oldest commercial reactor. The logical step should be to decommission both reactors.

The crush zone beneath the Tsuruga nuclear power plant’s No. 2 reactor, which is called D-1, branches out from the Urazoko fault, an active fault located about 250 meters from the reactor buildings.

Japan Atomic Power plans to build two new reactors only about 800 meters from the Urazoko fault. Three crush zones run beneath the site.

Constructing reactors at such a seismically unstable location is reckless and defies common sense. The government’s guidelines prohibit building reactors and the facilities essential to their safe operation above active faults. The NRA should subject the nuclear power company’s new construction plan to the strictest scientific scrutiny to determine if the location is safe.

In the past, the safety evaluation of geological faults near nuclear power stations was largely left to the operators. The NRA team’s decision shows that the safety evaluation by operators was slipshod.

The Nuclear and Industrial Safety Agency and the Nuclear Safety Commission, which have allowed nuclear power plants to operate despite warnings from seismologists, bear a grave responsibility for the situation. It is important to determine what these bodies did during their safety checks.

日本語の抄訳はウィークリー12月22日号のP18に掲載されています。