From: Wilson, George
To: Howe. Allen; Gitter, Joseph
Cc: Mathew. Roy; Hiland. Patrick; Skeen, David
Date: Friday, March 18, 2011 8:25:11 AM
Station Blackout Rule
Also, in the 1980s–specifically in 1988– the NRC concluded that additional regulatory requirements were justified in order to provide further assurance that a loss of both offsite and onsite emergency ac power systems–a station blackout condition–would not adversely affect public health and safety. Studies conducted by the NRC have shown that the hardware and procedures that have been implemented to meet the station blackout requirements have resulted in significant risk reduction and have further enhanced defense in depth. However, we plan to carefully evaluate the lessons learned from the events in Japan to determine if enhancements to the station blackout rule are warranted.
The NRC staff reviewed the responses from every nuclear power plant and issued a SER accepting the proposed coping methods. Each light-water-cooled nuclear power plant licensed to operate must be able to withstand for a specified duration and recover from a station blackout as defined in Sec. 50.2. As a result of the SBO rule all plants have (1) established SBO coping and recovery procedures; (2) completed training for these procedures; (3) implemented modifications as necessary to cope with an SBO; and (4) ensured a 4- 16 hour coping capability. The coping capability was based on the reliability and redundancy of the on-site electrical system, the frequency of a loss of off-site power and the time needed to restore off-site power. The staff also performed pilot inspections at 8 sites to verify proper implementation of the SBO rule. Based on the outcomes of those inspections the Staff concluded that the industry was properly implementing the rule.
There are 44 Units that rely on Battery power to cope with a SBO (4 hour coping)
There are 60 Units that have opted to use an alternate AC source (4-16 hours coping)
EICB Branch Chief, Division of Engineering
Mail Stop 012H2