Japan's Nuclear Regulation Authority (NRA) concluded on 29 June that three NPPs were guilty of "level 2" safety violations by breaching standards on placement of power cables. NRA said new safety standards regarding power cable installation had been violated at Tokyo Electric Power Co's (Tepco's) Fukushima Daiini NPP in Fukushima Prefecture, Tohoku Electric Power Co's Onagawa plant in Miyagi Prefecture and Chubu Electric Power Co's Hamaoka plant in Shizuoka Prefecture. Tepco's Kashiwazaki-Kariwa NPP in Niigata Prefecture was earlier also found to have committed a level 2 violation - the second heaviest violation in the NRA's four-tier list.
The NRA is set to carry out additional safety inspections on the three recently named nuclear plants as well as at the Kashiwazaki-Kariwa plant to check whether problems at these plants have been corrected. Violation of power cable-related safety standards has been found at 19 reactors at six NPPs, as well as at Japan Nuclear Fuel Ltd's used fuel reprocessing facility in Aomori Prefecture. Subsequent inspections by power companies and the NRA found such violations at a total of 5,344 locations on the premises of those plants. Of these, violations at the four NPPs, including Kashiwazaki-Kariwa, were deemed particularly malicious as utilities failed to check their power cable placing and continued to violate the safety standards even after regulations for power companies to conduct in-house inspections on power cable installation were introduced in October 2003.