NRC critiques OIG report on Diablo Canyon feedwater system oversight

May 5, 2022, 12:00PMNuclear News

The Nuclear Regulatory Commission turned the tables a bit on its inspector general’s office this week, releasing its response to a March 25 OIG event inquiry that criticized an NRC inspection at California’s Diablo Canyon nuclear power plant, performed after a July 2020 auxiliary feedwater (AFW) system failure at Unit 2.

The response highlights a number of what the agency terms “factual errors” and takes issue with several portions of the OIG report.

The response: Findings outlined in the NRC response include:

  • The leak in the AFW system did not cause the plant to shut down as stated by the OIG, nor did it compromise plant safety. The Diablo Canyon plant has operated safely and continues to do so.
  • The staff found no evidence that the AFW pipe corrosion hidden under metal-jacketed insulation should have been identified by NRC inspectors before the leak occurred. The resident inspectors then assigned to Diablo Canyon followed appropriate guidance during their inspection of the system, and regional and headquarters management appropriately determined that the leak had very low safety significance. Corrosion under insulation, which caused this leak, is known to the industry and the NRC.
  • The agency remains confident in the effectiveness of its inspection program, which is one of many ways in which it verifies nuclear power plant safety. Other methods include Reactor Oversight Program performance indicators, rigorous plant licensing requirements, robust design margins for every plant, redundant safety systems that provide defense in depth, and operator and training requirements to enable plant operators to respond to equipment malfunctions and unexpected events.

What they’re saying: “After reviewing the inspector general’s event inquiry, our technical staff determined that the Reactor Oversight Program and its associated inspection program continue to provide reasonable assurance of adequate protection of public health and safety,” stated Dan Dorman, the agency’s executive director for operations. “Resident inspectors are vital to the NRC safety mission. I have full confidence in the qualification, abilities, and professionalism of the inspectors involved in this event inquiry, as well as all of our inspectors.”


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