NHK reported this morning that Japanese nuclear regulators have categorized a security lapse at the Kashiwazaki-Kariwa nuclear plant in Niigata Prefecture at the most serious level in terms of antiterrorism measures. According to the network, the Nuclear Regulation Authority (NRA) was notified by the plant’s operator TEPCO in January that a worker accidentally damaged sensor equipment for detecting intruders. On Tuesday, the results of an investigation of the plant were reported during an NRA closed-door meeting. The probe reportedly found that other sensor equipment may have been broken since March 2020, making the plant vulnerable to intruders for months. NRA Chairman Fuketa reportedly said at a news conference that the plant was “in an extremely serious situation” in terms of protecting nuclear material and said it will conduct additional onsite inspections.