Japan’s Nuclear Regulation Authority (NRS) has concluded that unit 2 of the Tsuruga NPP in Fukui Prefecture does not meet the strict safety regulations introduced following the 2011 Fukushima disaster. This effectively refusing permission to plant operator Japan Atomic Power Co (JAPC) to restart the facility. This is the first time NRA, set up in 2012 has rejected an application to restart a reactor under the new rules.
Current safety standards do not permit the installation of safety-critical equipment on an active fault line and NRA said it cannot rule out the possibility that a fault line running under the reactor building may be connected to the nearby active “K Fault” some 300 metres north of the unit 2 reactor building. The conclusion will be reported to NRA commissioners who are expected to uphold and finalise the judgment.
NRA will publish its official decision later, after which JAPC can either apply for additional screening or consider decommissioning the unit. JAPC has reiterated its view that the fault under the reactor will not move, based on the results of a boring survey near the building. “We will conduct additional research. We are not thinking of scrapping [the unit], JAPC President Mamoru Muramatsu told reporters.
In May 2013, NRA geological experts said a fault running underneath Tsuruga 2 was active, but JAPC rejecting the findings and applied for a safety review in November 2015, hoping to restart the unit.
According to The Mainichi, the review process for the reactor has been “rocky”, with the regulator having faced a temporary two-year suspension after it was revealed JAPC had submitted documents with over 1,000 inaccuracies and rewritten data without approval. The process was suspended again in April 2023 over faulty documents presented by the operator.
The Tsuruga NPP, around 300 km west of Tokyo, comprises two units. Unit 1, a boiling water reactor, began operation in 1970, and is due to be decommissioned. Unit 2, a 1,160 MWe pressurised water reactor started up in 1987 and went offline in May 2011.
A number of leading newspapers have published editorials discussing the situation. Asahi Shimbun noted: “A major nuclear accident would cause irreversible damage. Based on this lesson, regulatory decisions on the safety of reactors should err on the side of greater safety when in doubt. The risk from an active fault directly below a critical nuclear facility is extremely high, and if its presence under the reactor cannot be denied, there is a compelling case for not allowing the operation of the reactor.” It added. However, that NRA cannot force the decommissioning of nuclear reactors that do not meet the new safety standards but noted that nine years have already passed since the application to restart the Tsuruga 2 unit. “The prolonged review process is due to the operator’s mishandling of the procedure.
“Given the backlog of other nuclear plant reviews and the time the NRA has already devoted to this application, Japan Atomic Power must surely realise it is being unreasonable in pursuing the undertaking,” the paper said. It said the location of the Tsuruga plant is not suitable for a nuclear facility as it is located on a peninsula and evacuation routes would be limited in the event of an earthquake.
The Mainichi, in its editorial, noted that NRA’s decision “has underscored the difficulty of keeping nuclear power online in earthquake-prone Japan”. It added: “The parties involved must maintain a safety-first stance.” It said NRA’s assessment result means that Tsuruga 2 “had been running with seismic risks since it went online in 1987” and that JAPC “should opt for decommissioning”.
JAPC was established in 1957 as a wholesaler to sell electricity to power companies. In 1966, it began operating Japan’s first commercial nuclear station, the Tokai plant in Ibaraki Prefecture. In 1970, when the Osaka Expo opened, JAPC launched Tsuruga 1 to supply electricity to the expo venue. Both reactors are being decommissioned. JAPC’s only other reactor, Tokai 2, has no prospect of restarting, having been closed for a long time. To sustain JAPC’s operations, five major power companies, including Tokyo Electric Power Co and Kansai Electric Power Co, are paying around JPY90bn ($585m) a year.
“Can these operators gain support from their shareholders and consumers over assisting JAPC any longer?,” The Mainichi asked. “With the increasing use of renewable energy and the declining necessity for nuclear power plants, it is time for JAPC to reassess its role and organisational structure.” It concluded: “If the use of nuclear power is to continue, efforts must be made to dispel public concerns. The government and operators have a responsibility to thoroughly verify and implement measures to enhance safety.”
Similarly, Yomiuri Shimbun said NRA’s decision not to allow the reactor to resume its operations may have been largely influenced “by a sense of distrust toward the JAPC for its repeated mishandling of the situation”.
While JAPC intends to continue conducting additional investigations, reapply for a safety screening and correct documents the outcome will depend on whether the JAPC will be able to collect convincing new data. “NRA is negative about further continuation of the screening from a standpoint of seeking high levels of safety. It is said that, as the underground structure of the Tsuruga plant is complex, it is difficult to completely prove that there are no active faults,” the paper noted.
“The NRA and the JAPC need to continue their dialogue to reach a scientific conclusion that is acceptable to both sides…. The screening should be hastened while giving consideration to safety.”
To date, following the closure of all of Japan’s reactors in the wake of the Fukushima disaster, 24 have already been decommissioned. Of the 27 that have undergone safety screenings, the restart of 17 has been approved, 12 of which have already resumed operations. The remaining five are preparing to resume operations after improving safety measures. The screenings of 10 reactors are still ongoing.
