Tsuruga Nuclear Plant's No. 2 Reactor Faces Decommissioning Due to Active Fault Concerns

Tsuruga Nuclear Plant's No. 2 Reactor Faces Decommissioning Due to Active Fault Concerns

The Nuclear Regulation Authority (NRA) of Japan has concluded that the No. 2 reactor at the Tsuruga nuclear power plant in Fukui Prefecture does not meet regulatory safety standards. This decision stems from concerns about an active fault running directly beneath the facility.

This assessment by the NRA will likely prevent the restart of the plant, operated by Japan Atomic Power Co. The company will be forced to consider decommissioning the facility if the application to restart the reactor is denied.

The No. 2 reactor, which began operation in 1987, has an output of 1.16 million kilowatts. If the NRA rejects the restart application, it would mark the first time the agency has done so under the new regulatory standards established after the Fukushima disaster.

These improved safety regulations prohibit the operation of nuclear power plants if an active fault is known to run directly under critical facilities. The NRA requires electric power companies to scientifically prove the absence of active faults during the examination process for restarting nuclear power plants.

The review focused on determining whether the "K fault," found in a trench about 300 meters north of the reactor, is active and extends directly under the reactor building. Japan Atomic Power asserted that the K fault is not active, citing strata analysis and a boring survey. However, the NRA dismissed this claim as lacking scientific or technical basis.

Despite the NRA's decision, Japan Atomic Power has requested a new investigation be added to its application for a restart. The company hopes to "make a readjustment after conducting an additional investigation." However, the NRA is unlikely to approve this request as it has not yet decided on the content of the additional investigation.

The existence of an active fault at the Tsuruga plant has been known for nearly two decades. In 2008, the operator recognized the "Urasoko fault" located about 200 meters from the No. 2 reactor as an active one from about 4,000 years ago. Both in 2013 and 2015, the NRA's panel of experts pointed out that the fault directly below the reactor is active.

If the No. 2 reactor at Tsuruga is decommissioned, a large portion of the company's income could be lost. This could also hinder the progress of No. 3 and No. 4 reactors at the Tsuruga plant, which are still in the planning stages. A shakeup in the company's business foundation could affect the restart of the Tokai No. 2 nuclear power plant as well.