Broken Switch has CA Nuke Seeing White

Tuesday, January 3, 2017 @ 10:01 AM gHale

A broken switch at a California nuclear power plant left a reactor cooling system temporarily inoperable.

That issue led the Nuclear Regulatory Commission (NRC) to cite the Diablo Canyon nuclear plant for a low-risk safety finding.

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The NRC issued a “white finding” Thursday, claiming the plant failed to adequately maintain an aspect of its emergency core cooling system, resulting in a low-to-moderate safety risk at the plant. The NRC evaluates regulatory performance at nuclear plants by color-coding inspection findings as green, white, yellow or red, in order of increasing safety significance.

PG&E, which owns and operates the plant, has since corrected the situation, spokesman Blair Jones said, and it plans to appeal the finding.

“We are absolutely committed to the highest safety standards,” he said. “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.”

The two units at Diablo Canyon are each equipped with two emergency core cooling systems, which use water to cool the reactors if an accident or malfunction occurs.

During a scheduled test in May, workers discovered one of the cooling systems for Unit 2 was inoperable for up to a year and a half; that particular system had last been checked in October 2014.

The problem ended up being a limit switch installed in a way that had it operating beyond its optimal capacity.

Jones said because there are two cooling systems per reactor, there would have been little risk to the public in the event an accident had occurred while the switch was not working.

“We also believe that in the unlikely event this system was needed, our professional operators, who continually train and drill to meet any potential emergency, would have successfully responded to ensure the equipment met its function,” he said.

If the utility’s appeal is unsuccessful, it means there will be an additional NRC inspection of the plant in the coming year. (The plant already undergoes an annual inspection, per federal law.)

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