Fault Near Fukui Pref. Nuclear Power Plant May Be Active; Survey To Determine Whether It Extends Directly Under Reactor

Yomiuri Shimbun file photo
Tsuruga Power Station’s No. 2 reactor, center, in Fukui Prefecture in October last year

A team of investigators working for Japan’s Nuclear Regulation Authority (NRA) said Friday that they could not rule out the possibility that a seismic fault located near the No. 2 reactor of Fukui Prefecture’s Tsuruga Power Station is active.

The existence of the fault, called the K Fault, has been confirmed at a location about 300 meters north of the reactor building. The Japan Atomic Power Company (JAPC) aims to restart the reactor, but it will not be allowed to do so unless it can prove that the fault does not extend directly beneath the reactor building.

According to the NRA’s new regulatory standards, which set safety practices for nuclear power plants, if an active fault that could cause an earthquake runs directly beneath an important facility such as a reactor building, the plant cannot be turned on.

At issue are questions of whether the fault is active, and whether it extends directly under the building.

At a meeting on Friday to discuss whether the fault was active, the JAPC argued that it was not, based on the results of a drilling survey and volcanic ash analysis, among other data.

The screening team, however, said that the possibility of the fault being active remains, as the complex layering of soil deposits in the area makes it difficult to determine the fault’s type.