NRC CAL – NOV (White)

On August 17, 2011, the NRC issued a Notice of Violation to Northern States Power Company for a violation associated with a White Significance Determination Process finding. The violation involved the failure to maintain the direct current electrical power subsystems operable in Modes 1 through 4, as required by Technical Specification 3.8.4. Specifically, from December 21, 1994 to approximately October 22, 2010, all battery chargers in Unit 1 were susceptible to a common mode failure under design basis accident conditions. Under those conditions, the battery chargers would stop providing an output, or "lock-up," when their alternating current input voltage dropped below their nameplate minimum voltage at the battery charger motor control center.