By Brenda Lorenz, Manager, Components & IT Systems, Fauske & Associates, LLC
A station (SBO) is defined as the all AC power at a nuclear plant, This is a loss of off-site together with a failure of the emergency backup to operate. Per NRC Regulations Title 1 0, Code Of Federal Regulations (CFR) 5063 Of all alternating current all US. plants a coping capability for SW conditions for a limited time period rarging from approximately tv.•o to sixteen hours. An extended of AC power event is as a loss of all off-site and on-site AC sources for an indetemnate period Of time. which will Challenge the kM1g-term Cooling Of the the Spent fuel (SFP) unless mitigating actions are taken. I his extended requirement is the result of the events at Fukushima.
Station batteries prm'ide control to switchgear breakers needed for the operation of the AC equipment including the independent Core cc-oling Sources The batteries also necessary control of vital plant parameters. some iS the power for DC independent Outside Of the requited independent offsite power supplies there are dedicated SBO diesel generatorsor gas turbines. Priat to recmh?ry from an EMP it is imperative that DC power remain available for indication and for control cm•ce AC is Far ELAPevent there is no design basis accident assumed. Nudear Energy Institute (NEI) Diverse And Flexible Coping Strategies (FLEX) Implementation Guide (NEI 12-06 Aug. 2012) requires the 125VDCdass I Ebatteries to for at least 24 hours. Approaches to meet this requirement include; • Load-shedding prrxedures, • Crcss-tying batteries • Delayed battery operation An exampk of a station DC battery system that will be used for this analysis is in Figure I. This figure shows the 125V DC bus battery and batterycharger. The bads were distributed betzeen two feeder panels. Figu 1 DC Battery Schematic