NRC Issues Interim Staff Guidance Related to Mitigation Strategies for Beyond-Design-Basis External Events
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The NRC has issued the final Revision 2 to Japan Lessons-Learned Division Interim Staff Guidance (ISG). This ISG provides guidance and clarifications on identifying measures needed to comply with requirements to mitigate challenges to key safety functions. These requirements are embodied in Order EA-12-049, “Order Modifying Licenses with Regard to Requirements for Mitigation Strategies for Beyond-Design-Basis External Events.” The NRC issued this order following evaluation of the 2011 Japan earthquake and tsunami, which resulted in a nuclear accident at the Fukushima nuclear plant. This order requires licensees to develop a three-phase approach for mitigating beyond-design-basis external events. The original version of this ISG was issued in 2012 and endorsed NEI 12-06. This revision provides additional guidance regarding reevaluated seismic hazard information and changes based on lessons learned related to mitigating strategies implementation.