NRC CITES PRAIRIE ISLAND UNIT 1 NUCLEAR PLANT FOR AN ISSUEIN

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NRC CITES PRAIRIE ISLAND UNIT 1 NUCLEAR PLANT FOR AN ISSUEINVOLVING BATTERY CHARGERSNuclear Regulatory Commission issued a violation of low to moderate safety significance to Prairie Island Unit 1 Nuclear Power Plant which will result in additional NRC oversight. The two-unit plantoperated by Northern States Power Company-Minnesota is located in Welch, Minn., approximately 45 miles southeast of Minneapolis.NRC resident inspectors at the plant identified an issue involving Unit 1 safety-related batterychargers during routine inspections. The chargers were found to have the potential of not performing theirsafety functions under certain event scenarios, such as if incoming voltage was lower than normal. The devices charge batteries which would provide alternate power to remotely operate important plant safetyequipment. Each reactor has two chargers. If both are lost, the chargers can be reset manually in order to continue to operate. The utility has taken actions to address the issue. The NRC has evaluated the actions and considers them acceptable.“Even though this issue did not have an impact on routine plant operation or members of the public, the NRC requires safety-related equipment to be operable in accordance with the conditions of the plant’s operating license,” said Region III Administrator Mark Satorius. “Contrary to these requirements, batterychargers at Prairie Island Unit 1 were susceptible to failure under certain conditions.”The NRC evaluates performance at nuclear power plants with a color coded process which classifiesregulatory findings as green, white, yellow or red, in order of increasing safety significance. Afterconsideration of the information the NRC staff has characterized the inspection finding as “white” meaning ithas a low to moderate safety significance. The NRC will conduct a supplemental inspection to provideassurance that plant operators have understood the causes of the problem, evaluated other areas of plantoperation for similar problems, and taken sufficient corrective actions to prevent recurrence.The company has until September 16 to contest the finding. The NRC inspection report detailing the finding is publically available under accession number ML111610249 through the Agency Documents Access and Management System (ADAMS) at the NRC website. ###