Post-Fukushima Safety Enhancements

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Safe Facilities Made Safer

Image of a generic nuclear plant highlighting the different Post Fukushima Safety Enhancement including mitigation strategies, flex equipment, containment venting systems, spent fuel pool instrumentation, emergency preparedness and flooding and seismic defenseMitigation Strategies web page hyperlink Containment Venting System web page hyperlink Flooding and Seismic Defense web page hyperlink Flooding and Seismic Defense web page hyperlink Spent Fuel Pool Instrumentation web page hyperlink Emergency Preparedness web page hyperlink Flex Equipment web page hyperlink Flex Equipment web page hyperlink


On March 11, 2011, a 9.0-magnitude earthquake, followed by a 45-foot tsunami, heavily damaged the nuclear power reactors at Japan's Fukushima Dai-ichi facility. Following this accident, the NRC required significant enhancements to U.S. commercial nuclear power plants.1

The enhancements included: adding capabilities to maintain key plant safety functions following a large-scale natural disaster; updating evaluations on the potential impact from seismic and flooding events; new equipment to better handle potential reactor core damage events; and strengthening emergency preparedness capabilities. Combined, these actions ensure that the nuclear industry and the NRC are prepared for the unexpected.

In August, 2019, the NRC amended its regulations to establish regulatory requirements for nuclear power reactor applicants and licensees to mitigate beyond-design-basis events. The new rule, 10 CFR 50.155, "Mitigation of beyond design basis events," makes NRC Order EA-12-049, "Order Modifying Licenses With Regard to Requirements for Mitigation Strategies for Beyond-Design-Basis Events" (Mitigation Strategies Order), and Order EA-12-051, "Order Modifying Licenses With Regard to Reliable Spent Fuel Pool Instrumentation" (Spent Fuel Pool Instrumentation Order), generically applicable; establishes regulatory requirements for documentation of changes; and addresses several Petitions for Rulemaking that were submitted to the NRC following the March 2011 Fukushima Dai-ichi event. The final rule was published in the Federal Register on August 9, 2019 (84 FR 39684) with an effective date of September 9, 2019. The FRN also announced the public availability of the final regulatory guidance, Regulatory Guide 1.226, "Flexible Mitigation Strategies for Beyond-Design-Basis Events" and Regulatory Guide 1.227, "Wide-Range Spent Fuel Pool Level Instrumentation."

The rule package is available in ADAMS at Accession No. ML19058A006.


1 Although this information focuses on commercial nuclear power plants, the NRC considered the lessons of the accident for other types of nuclear facilities and required enhancements as appropriate.

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Page Last Reviewed/Updated Wednesday, March 11, 2020