Nuclear NRC failed to properly inspect Diablo Canyon pipes before leak, audit finds Inspectors with the U.S. Nuclear Regulatory Commission (NRC) failed to properly inspect Diablo Canyon Power Plant pipes before a cooling system leak shut down one of the plant’s two reactors for eight days in 2020. Kevin Clark 3.29.2022 Share Follow @KClark_News Inspectors with the U.S. Nuclear Regulatory Commission (NRC) failed to properly inspect Diablo Canyon Power Plant pipes before a cooling system leak shut down one of the plant’s two reactors for eight days in 2020. The findings were released by the U.S. Office of Inspector General (OIG) on March 28. In the last few years inspectors said they had reviewed multiple concerns about the NRC’s oversight of Diablo Canyon’s safety-related structures, systems, and components. Concerns included specific allegations that the NRC had inadequately inspected the plant’s auxiliary feedwater system (AFS) prior to the cooling system leak. An AFS is a backup water supply that can be used to cool the reactor if normal feedwater is out of service. This photo shows the July 2020 leak and the corrosion that appears to be far more long-standing. (Source: DCNPP). According to the OIG’s findings, the NRC failed to identify AFW piping insulation in Diablo Canyon’s Unit 2 that had long been in a degraded condition. This degradation led to the leak which Pacific Gas & Electric (PG&E) employees found while working at the plant on July 23, 2020. PG&E owns and operates Diablo Canyon, the last operating nuclear plant in California. The OIG found that at no time during the NRC’s January and April 2020 AFW system inspections, or during weekly plant status inspections, did the NRC report any findings regarding SSCs that exhibited defects--such as degraded insulation on the AFW system--that would impact function. MORE: NRC to Address Inoperable Safety System at Diablo Canyon Nuclear Plant The OIG findings also said the NRC had not inspected the area where the leak occurred, even though its inspection report indicated that inspectors had conducted a complete walkdown of the AFW system in April 2020. The OIG report also said the five hours NRC staff spent directly inspecting AFW systems in both Diablo Canyon reactors was fewer than the 12 recommended in the applicable NRC inspection procedure for the complete April 2020 walkdown. “Senior regional officials acknowledged that the inspection was inadequate,” federal inspectors said in their report. Eight days after the Unit 2 shutdown, PG&E restarted the unit after inspecting 40 pipe sections and repairing piping in several locations to ensure pipe thickness met requirements. The NRC issued PG&E a notice of violation for “failure to appropriately screen relevant operating experience.” The commission the violation was based in part on the fact that the utility received information in 2009 and 2010 relating to corrosion of carbon steel piping under insulation, but did not identify the AFW as being susceptible to corrosion under insulation. OIG Inspectors said PG&E remedied the AFW system failure and that the plant continues to operate safely. The inspectors also said the NRC should ensure that its inspectors are trained to identify corrosion under insulation, that inspection procedures are adequate for walkdowns (especially with a single unit versus a multiple-unit plant), that NRC managers are involved in reviewing whether inspectors follow procedures, and that managers are appropriately involved in helping select systems and components for inspection. The plant has two Westinghouse-designed 4-loop pressurized-water nuclear reactors. Unit 1 entered service in May 1985 and Unit 2 in March 1986. As part of its congressionally mandated mission, the NRC regularly inspects commercial nuclear power plants. NRC inspections assess whether licensees are properly conducting operations and maintaining equipment to ensure safe operations. In a statement sent to Clarion Energy, the NRC said it continues to have “full confidence” in its staff. “We are reviewing the Inspector General’s report and will take appropriate action if needed," said Victor Dricks, NRC senior public affairs officer. “At no time was public safety endangered because of this incident.” A spokesperson with PG&E said that “safety is and always will be our most important responsibility at PG&E and Diablo Canyon, and the plant has an excellent safe operating record.” In 2018, the California Public Utilities Commission approved a settlement to shut down Diablo Canyon. The plant currently provides 8% of California's electricity production and 15% of its carbon-free electricity. PG&E intends to begin active decommissioning of the plant in 2025 and to complete the project in one decade. Related Articles Dominion Energy approved to extend North Anna Power Station operations for 20 more years South Carolina considers its energy future through state Senate committee TVA approves more funding for advanced nuclear reactors A robot’s attempt to get a sample of the melted fuel at Japan’s damaged nuclear reactor is suspended
