The impact of FLEX on outage risk

摘要

Following the Fukushima Daiichi accident, the US Nuclear Regulatory Commission (NRC) issued order ES-12-049 [1] requiring nuclear plants in the US to implement mitigation strategies to cope with a beyond-design-basis external event. The event is assumed to result in an extended loss of all AC power and loss of access to the ultimate heat sink for all units on the site, with no expectation of either returning. The initial phase requires installed equipment and on-site resources to be used to maintain or restore cooling capability for the core, containment and spent fuel pool (SFP). The transition phase requires the use of portable onsite equipment to provide sufficient cooling for these functions. The final phase requires the use of offsite resources to sustain these functions indefinitely.