Another access control irregularity at Kashiwazaki-Kariwa Nuclear Power Station: exit gate fails to intercept unauthorized passage

Tokyo Electric Power Company (TEPCO) announced on August 7 that an irregularity related to access control occurred at the Kashiwazaki-Kariwa Nuclear Power Station. An operator improperly used his own ID card to allow a colleague who had left his ID card in the central control room to pass through the gate and exit. TEPCO stated that the access control system failed to display an error message at the time and was unable to prevent this unauthorized passage.

According to disclosed information, the incident occurred during the “exit” process and involves management matters related to nuclear material protection. TEPCO has not yet publicly disclosed the specific date of the incident, the identities of the personnel involved, the detailed reasons why the system failed to trigger an alarm, or subsequent disciplinary actions and preventive measures.

The Kashiwazaki-Kariwa Nuclear Power Station has previously experienced multiple issues related to nuclear material protection and counter-terrorism measures, including intrusion detection equipment failures and employees using others' identification cards to enter the central control room. In 2021, Japan's Nuclear Regulation Authority imposed de facto operational suspension measures on the plant, which were lifted in December 2023.

Following the previous incidents, TEPCO implemented a number of corrective measures, including installing biometric authentication equipment, reinforcing gates in restricted areas, and strengthening multi-layered protection around the central control room. This latest incident occurred on the exit side, revealing that the access control system still has issues to be investigated in the identification and interception of abnormal passage.

Unit 6 of the Kashiwazaki-Kariwa Nuclear Power Station resumed commercial operation in April 2026, making it the first reactor at TEPCO to resume commercial operation after the Fukushima Daiichi Nuclear Power Station accident. This incident occurred shortly after Unit 6 resumed commercial operation. To date, TEPCO has not announced whether this incident will affect the operational schedule of Unit 6.

TEPCO stated that it will continue to disclose relevant non-conformance items through public information channels. Subsequent regulatory determinations, system failure causes, and corrective measures remain to be further disclosed by the company and regulatory authorities.