The Nuclear Regulatory Commission has identified a “white” inspection finding, or low to moderate safety issue, concerning an emergency cooling system at the Diablo Canyon Power Plant in California.
The agency detailed the Sept. 12 finding in a letter to operator Pacific Gas & Electric on Monday. Located about 12 miles southwest of San Luis Obispo, Diablo Canyon is the last operating nuclear plant in California and is scheduled to close by 2025.
NRC spokesman Victor Dricks said on Friday that the plant’s Unit 2 emergency core cooling system was inoperable for an extended period of time because of a maintenance issue. It occurred when workers incorrectly set a mechanical switch on one of the system’s valves. That valve then did not send the proper signal to a second valve, rendering the cooling system inoperable, Dricks explained. The emergency core cooling system provides water to the reactor when it loses coolant.
PG&E has since restored the valve and replaced the affected components, including the limit switch, according to the NRC. The agency is considering taking regulatory action, which could involve escalated enforcement or additional inspections at the plant, and will make a determination within three months. Escalated enforcement could entail altering the plant’s safety rating and increased regulatory oversight.
“We are absolutely committed to the highest safety standards, and constantly inspect the plant to ensure we meet our primary mission to protect public health and safety first,” PG&E spokeswoman Blair Jones said by email Wednesday. “This relentless focus on safety led us to discover this issue and make immediate repairs. We believe it is not reflective of current plant performance.”
