The reactor at Diablo Canyon nuclear power plant in San Luis Obispo operated for a year and a half with some emergency systems disabled, according to a 2010 safety review by the federal Nuclear Regulatory Commission.

The incident was one of 14 “near-misses” the NRC uncovered in its inspections of nuclear power plants where problems had been occurring. An analysis by the group Union of Concerned Scientists concluded that “many of these significant events occurred because reactor owners, and often the NRC, tolerated known safety problems.”

The NRC found a range of problems at the 14 plants, including poor design, equipment failure, poor training and human error.



The issue at the Diablo Canyon plant, which is operated by Pacific Gas & Electric, involved malfunctioning valves that prevented other valves from opening. The valves were improperly repaired and subsequent tests failed to detect the problem, according to the report.

Analysis by the Union of Concerned Scientists found that the NRC’s inspections suggest that nuclear plants “continue to experience problems with safety-related equipment and worker errors that increase the risk of damage to the reactor core.”

The UCS report also cited three instances in which NRC inspectors aggressively pursued power plant operators to enforce safety standards.

-- Julie Cart

Photo: Diablo Canyon nuclear power plant. Credit: Los Angeles Times