Japan’s Nuclear Regulation Authority (NRA) said on 17 March that Tokyo Electric Power Co’s (Tepco’s) plan to restart unit 7 at its Kashiwazaki-Kariwa NPP in Niigata Prefecture must be put on hold after finding “shoddy” repairs security systems at the site. NRA said the plant had been vulnerable to unauthorised entry in around a dozen locations since March last year, after its security system lost partial functionality and backups were not effective. Intruder detection systems were defective in 15 locations at the plant, according to Tepco. NRA deemed backup systems were insufficient in 10 of the locations.

Nuclear power plants detect unauthorized entry through security cameras and sensors installed at various points. The NRA was told by Tepco about the loss of functionality earlier this year and confirmed the problem through its investigation in late February. NRA provisionally rated the breach at the plant at the worst level in terms in safety and severity, marking the first time it has given such an assessment. It will notify TEPCO of the rating, finalisng it if there are no objections, and consider what disciplinary action should be taken.

"Systematic monitoring functionality fell, and the effectiveness of the physical protection system could not have been adequately confirmed for a long period of time. In terms of nuclear safeguarding, it could have resulted in a grave situation," NRA said. NRA Chairman Toyoshi Fuketa told a press conference that additional investigations following the revelation would take "a year or more" and suggested the plant's application for restarting could not be processed until they conclude.

Regarding penalties such as ordering the plant to be decommissioned or revoking its licence to operate, Fuketa said they would be discussed at a public meeting after the rating is finalised. NRa said security staff at Tepco did not take steps to resolve the issue despite being aware the backup system was not effective. The staff said functionality has now been restored to the system, and no intruders have been detected.

NRA also found that a similar loss of functionality in a physical protection system occurred in multiple locations from January 2018 to March 2020, and it took time for the equipment to return to normal.

NRA is demanding that Tepco conduct a third-party probe on the cause of the defects and report the findings within six months.

The Kashiwazaki-Kariwa plant has seen a number of security issues, including an incident in which an employee used a colleague's ID pass last September to enter the central control room unauthorised. Tepco issued to stern warnings its president, Tomoaki Kobayakawa and 12 others and took other disciplinary action over the incident.

In addition, safety installations have not been completed at the unit 7 reactor and fuel loading that was originally scheduled to be conducted in March to April has been revised to "undecided”. Tepco had been focusing on preparing units 6 and 7 at Kashiwazaki-Kariwa for restart while also dealing with the clean-up at Fukushima Daiichi.

Restarting the two 1356 MWe Advanced Boiling Water Reactors would increase the company's earnings by an estimated JPY100 billion ($916 million) a year, saving massive costs being spent on fossil fuel for its thermal power plants. Tepco applied for NRA approval of its design and construction plan for the units in 2013. They were the first Japanese boiling water reactors to be put forward for restart.

Fuketa said an additional inspection of the site will take “at least more than a year even if it proceeds at an extremely fast pace”. Since January this year, Tepco has repeatedly reported to the NRA that it had taken measures to remedy the situation. However, NRA found these measures were inadequate when it conducted an unannounced inspection in February.

Asahi Shimbun said Fuketa was clearly infuriated by the utility’s handling of the situation. “The alternative steps are shoddy as anyone can see,” he said at an emergency news conference on 16 March. “We need to determine whether Tepco settled on the measures due to a ‘lack of knowledge’ or it believed that it could just gloss over the problem with ‘that level of response’.”

Industry minister Hiroshi Kajiyama acknowledged that Tepco is nowhere near restarting the Kashiwakazi-Kariwa plant, and said the company’s situation is “extremely concerning.” Kashiwazaki Mayor Masahiro Sakurai expressed “shock” over Tepco’s actions at the news conference. “I am afraid that the recent problem illustrates the company’s inability to alter its systemic awareness,” he said.

Tepco said it is taking the NRA's assessment "very seriously" and it "will quickly respond", adding, "We would like to deeply apologise for the concern we have caused amongst regional residents, and society as a whole, as a result of these incidents."

Tepco said it had informed NRA on 5 March that repairs had been made to all the malfunctioning equipment. It also confirmed that no unauthorised access has been found to have occurred at the affected locations. "Furthermore, we have put in place a system for implementing effective substitute measures to counteract any new malfunctions of nuclear material protection equipment."