The Nuclear Regulation Authority on Wednesday accepted an assessment that reactor 2 at the Tsuruga nuclear plant in Fukui Prefecture is sitting on an active fault, increasing the likelihood that the unit can never be restarted.
“We have received a report from a panel of experts that said there is an active fault. . . . I think there is a need to accept the conclusion sincerely,” NRA Chairman Shunichi Tanaka told a meeting attended by other commissioners to discuss the panel’s conclusion.
It is the first time regulatory authorities have acknowledged that an existing reactor is located on a fault that is feared might shift. The judgment may leave plant operator Japan Atomic Power Co. with no option but to scrap reactor 2.
The NRA also wants Japan Atomic Power to study how the spent-fuel pool inside the No. 2 reactor building would be affected in the event the fault moves.
Most of Japan’s nuclear reactors are currently offline because of the Fukushima No. 1 complex disaster that started in 2011, and they are required to undergo the NRA’s safety assessment process to check whether they satisfy the new regulatory requirements to be introduced in July before they can resume operations.
The NRA, however, is unlikely to go ahead with a safety review for reactor 2 of the two-unit Tsuruga plant, given the panel’s assessment, if Japan Atomic Power submits an application.
The panel, consisting of NRA Commissioner Kunihiko Shimazaki and four outside experts concluded last week that a zone of rock fragments called D-1, running directly beneath reactor 2, is an active fault, rejecting Japan Atomic Power’s objections.
The panel also said the D-1 fault could move along with a confirmed major active fault called Urazoko that is located about 200-300 meters from the reactor 1 and 2 buildings, and may affect facilities located above.
Nuclear plant operators are not permitted to build or operate reactors and other important safety facilities directly above active faults — currently defined as those that have moved in the last 120,000 to 130,000 years.
Japan Atomic Power, however, is still conducting its own investigation at the plant in a bid to overturn the panel’s assessment, while the company’s president, Yasuo Hamada, said last week the firm may eventually have to consider taking the issue to court.
Major utilities holding a stake in Japan Atomic Power are closely watching how the issue unfolds, fearing that the company may fall into negative net worth if it has to scrap reactor 2 because of a shortage of decommissioning funds and loss in asset value.
The company has set aside money for future decommissioning costs on the assumption that reactor 2 will operate for 40 years, but it has been commercially operating for only 26 years.
Restarting Japan Atomic Power’s two other reactors is also unlikely to be easy, with reactor 1 at the Tsuruga plant aging and a reactor at the Tokai No. 2 plant in Ibaraki Prefecture facing local opposition.
Japan Atomic Power is currently surviving on revenues such as basic fees from major utilities that have contracts to receive electricity.
But the utilities may not be able to offer support forever because they are also struggling amid increased fuel costs for thermal power generation to make up for the loss of nuclear power.