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Mitigation Strategies for Beyond-Design-Basis External Events

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Nuclear Regulatory Commission.


Interim staff guidance; issuance.


The U.S. Nuclear Regulatory Commission (NRC) is issuing the final Revision 2 to Japan Lessons-Learned Division Interim Staff Guidance (JLD-ISG), JLD-ISG-2012-01, “Compliance with Order EA-12-049, Order Modifying Licenses with Regard to Requirements for Mitigation Strategies for Beyond-Design-Basis External Events.” This ISG provides guidance and clarification to assist nuclear power reactor licensees with the identification of measures needed to comply with requirements to mitigate challenges to key safety functions. These requirements are contained in Order EA-12-049, “Order Modifying Licenses with Regard to Requirements for Mitigation Strategies for Beyond-Design-Basis External Events.”


This guidance is effective on April 25, 2018.


Please refer to Docket ID NRC-2012-0068 when contacting the NRC about the availability of information regarding this document. You may obtain publicly-available information related to this document using any of the following methods:

  • Federal Rulemaking Website: Go to and search for Docket ID NRC-2012-0068. Address questions about NRC dockets to Jennifer Borges; telephone: 301-287-9127; email: For technical questions, contact the individual listed in the FOR FURTHER INFORMATION CONTACT section of this document.
  • NRC's Agencywide Documents Access and Management System (ADAMS): You may obtain publicly-available documents online in the ADAMS Public Documents collection at​reading-rm/​adams.html. To begin the search, select “ADAMS Public Documents” and then select “Begin Web-based ADAMS Search.” For problems with ADAMS, please contact the NRC's Public Document Room (PDR) reference staff at 1-800-397-4209, 301-415-4737, or by email to The ADAMS accession number for each document referenced (if it is available in ADAMS) is provided the first time that it is mentioned in this document. Revision 2 to JLD-ISG-2012-01 is available in ADAMS under Accession No. ML17005A188.
  • NRC's PDR: You may examine and purchase copies of public documents at the NRC's PDR, Room O1-F21, One White Flint North, 11555 Rockville Pike, Rockville, Maryland 20852.
  • NRC's Interim Staff Guidance Website:​reading-rm/​doc-collections/​isg/​japan-lessons-learned.html.
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Eric Bowman, Office of Nuclear Reactor Regulation, U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001; telephone: 301-415-2963, email:

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I. Background Information

The original Final Japan Lessons-Learned Project Directorate Interim Staff Guidance, JLD-ISG-2012-01 (ADAMS Accession No. ML12229A174) dated August 29, 2012, was issued to describe to the public methods acceptable to the NRC for complying with Order EA-12-049 issued March 12, 2012 (ADAMS Package Accession No. ML12054A736). This ISG endorsed the methodologies described in the industry guidance document, Nuclear Energy Institute (NEI) 12-06, “Diverse and Flexible Coping Strategies (FLEX) Implementation Guide,” Revision 0, (ADAMS Accession No. ML12242A378), submitted on August 21, 2012. Revision 1 to JLD-ISG-2012-01 (ADAMS Accession No. ML15357A163) was issued on January 22, 2016, and endorsed NEI 12-06, Revision 2 (ADAMS Accession No. ML16005A625), issued in December 2015. The NRC staff is now issuing Revision 2 to JLD-ISG-2012-01, which incorporates additional guidance related to reevaluated seismic hazard information and some additional changes based on lessons learned in the implementation of Order EA-12-049. This revision endorses NEI 12-06, Revision 4 (ADAMS Accession No. ML16354B421), issued in December 2016.

The NRC issued Order EA-12-049 following evaluation of the Japan earthquake and tsunami and resulting nuclear accident at the Fukushima Dai-Start Printed Page 18090ichi Nuclear Power Plant in March 2011. Order EA-12-049 requires all licensees and construction permit holders to develop a three-phase approach for mitigating beyond-design-basis external events. The initial phase requires the use of installed equipment and resources to maintain or restore core cooling, containment, and spent fuel pool cooling. The transition phase requires providing sufficient, portable, onsite equipment and consumables to maintain or restore these functions until they can be accomplished with resources brought from off site. The final phase requires obtaining sufficient offsite resources to sustain those functions indefinitely. Order EA-12-049 also specified that the NRC would issue final interim staff guidance in August 2012, to provide additional details on an acceptable approach for complying with Order EA-12-049.

The original version of this ISG, which endorsed the original NEI 12-06, was issued on August 29, 2012. Revision 1 to JLD-ISG-2012-01 incorporated acceptable alternative approaches to compliance proposed by licensees, as well as the NRC's review strategy described in COMSECY-14-0037, “Integration of Mitigating Strategies for Beyond-Design Basis External Events and the Reevaluation of Flooding Hazards” (ADAMS Accession No. ML14238A616), which clarified the NRC's position on the interdependency of the mitigating strategies responses and the responses to the seismic and flooding reevaluations. The NRC has further revised this ISG in Revision 2 in order to include additional guidance regarding reevaluated seismic hazard information and changes based on lessons learned related to mitigating strategies implementation. This revised guidance will be publicly available and used by members of the industry to help develop their responses to Order EA-12-049, including impacts of the reevaluated seismic and flooding information, and by the NRC in its reviews of licensee strategies. On November 10, 2016 (81 FR 79056), the NRC requested public comments on draft Revision 2 to JLD-ISG-2012-01. The NRC received comments from seven stakeholders, which were considered in the development of the final Revision 2 to JLD-ISG-2012-01. The questions, comments, and NRC resolutions of those comments are contained in “NRC Responses to Public Comments: Revision 2 to JLD-ISG-2012-01, Compliance with Order EA-12-049, `Order Modifying Licenses with Regard to Requirements for Mitigation Strategies for Beyond-Design-Basis External Events'” (ADAMS Accession No. ML17005A187).

II. Congressional Review Act

This ISG revision is a rule as defined in the Congressional Review Act (5 U.S.C. 801-808). However, the Office of Management and Budget has not found it to be a major rule as defined in the Congressional Review Act.

III. Backfitting and Issue Finality

This ISG provides guidance on an acceptable method for implementing the requirements contained in Order EA-12-049. Licensees may voluntarily use the guidance in Revision 2 to JLD-ISG-2012-01 to demonstrate compliance with Order EA-12-049. Methods or solutions that differ from those described in this ISG may be deemed acceptable if they provide sufficient basis and information for the NRC to verify that the proposed alternative demonstrates compliance with Order EA-12-049.

Issuance of this ISG does not constitute backfitting as defined in section 50.109 of title 10 of the Code of Federal Regulations (10 CFR), “Backfitting” (the Backfit Rule), and is not otherwise inconsistent with the issue finality provisions in 10 CFR part 52, “Licenses, Certifications, and Approvals for Nuclear Power Plants.”

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Dated at Rockville, Maryland, this 19th day of April, 2018.

For the Nuclear Regulatory Commission.

Anita L. Lund,

Director, Division of Licensing Projects, Office of Nuclear Reactor Regulation.

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[FR Doc. 2018-08601 Filed 4-24-18; 8:45 am]