ML22278A111

DG-1417 (RG 1.256 Rev 0) Regulatory Analysis

ML22278A111
Person / Time
Issue date:	07/09/2024
From:	Joseph Kanney NRC/RES/DRA/FXHAB
To:
O'Donnell E
Shared Package
ML22277A014	List: ML22278A110 ML22278A111
References
RG 1.256 Rev 0 DG-1417
Download: ML22278A111 (3)

Text

REGULATORY ANALYSIS DRAFT REGULATORY GUIDE (DG)-1417 GUIDANCE FOR ASSESSMENT OF FLOODING HAZARDS DUE TO WATER CONTROL STRUCTURE FAILURES AND INCIDENTS (Proposed New Regulatory Guide (RG) 1.256 Revision 0)

1. Introduction This document presents an analysis to determine whether the U.S. Nuclear Regulatory Commission (NRC) staff should expend resources to develop Regulatory Guide (RG) 1.256, Guidance for Assessment of Flooding Hazards Due to Water Control Structure Failures and Incidents. This analysis considers the potential benefits and costs to the NRC and stakeholders and provides the public with insight into the NRCs decision-making.

2. Statement of the Problem The NRC staff prepared interim staff guidance (ISG) JLD-ISG-2013-01, Guidance for Assessment of Flooding Hazards Due to Dam Failure, in 2013 to help nuclear power plant (NPP) licensees complete flood hazard reevaluations in response to the NRCs Title 10 of the Code of Federal Regulations (10 CFR) 50.54(f) information request issued following the 2011 Fukushima accident. The flood hazard reevaluations were to be performed using analysis methods current in 2012 and guidance used by the NRC staff for reviewing external flooding analyses for early site permit (ESP) and combined license (COL) applications submitted under 10 CFR Part 52. ISGs were prepared to clarify or address issues not fully discussed in the NRCs Standard Review Plan (NUREG-0800), which was to be used as the basic reference for reviewing the post-Fukushima flood hazard reevaluations. ISGs are meant to be withdrawn after their purpose has been fulfilled or else integrated formally into the NRCs regulatory guidance framework.

The NRC is considering issuing a new RG to formally integrate JLD-ISG-2013-01 into the NRCs regulatory guidance framework.

3. Objective The objective of this regulatory analysis is to assess the need to incorporate JLD-ISG-2013-01 into the NRCs regulatory guidance framework in the form of a new RG to provide up-to-date guidance on methods that the NRC staff considers acceptable for use in the determination of design-basis floods at NPPs.

4. Identification and Analysis of Alternative Approaches The NRC staff considered the following alternative approaches:

1. Withdraw JLD-ISG-2013-01 ISG.

2. Incorporate JLD-ISG-2013-01 into the NRCs regulatory guidance framework by developing a RG.

Page 2 Alternative 1: Withdraw JLD-ISG-2013-01 ISG Under this alternative, the NRC staff would withdraw the ISG and not issue additional guidance. This alternative would not address the identified gaps that motivated the issuance of the ISG and would not capture the lessons learned in the post-Fukushima flooding reevaluations.

A decision to not issue additional guidance may result in the NRC staff issuing requests for additional information (RAIs) to applicants for large light-water reactor nuclear power plant licenses under 10 CFR Part 50 and Part 52. Applicants could, potentially, be burdened by the effort required to respond to those RAIs, and the NRC staff would be burdened by the need to review the applicants responses.

Alternative 2: Develop a new RG Under this alternative, the NRC staff would issue a new RG, based on improved analysis methods contained in the ISG, as well as lessons learned from the post-Fukushima flooding reevaluations, for use in the review of 10 CFR Part 50 and Part 52 license applications, including their adherence to siting criteria provided in 10 CFR Part 100. One benefit of this alternative is it would enhance reactor safety by providing up-to-date guidance and information on acceptable methods for the determination of design basis floods at NPPs. In addition, it would improve the NRC staffs ability to efficiently review future applications. The costs to the NRC would be the one-time cost of issuing a new RG (which is expected to be relatively small).

Finally, Alternative 2 would result in a RG that complements DG-1290, a proposed revision 3 of RG 1.59, Design Basis Floods for Nuclear Power Plants, by providing detailed guidance on failure of water control structures that might impact a nuclear power plant. The determination of design basis floods for NPPs is required regardless of the existence or currency of RG 1.256.

5. Comparison of Alternatives The alternatives were compared against each other with respect to safety, as well as the NRCs and applicant resources.

Alternative 1 would make license application reviews more burdensome for the NRC staff and very likely make license application preparation more burdensome for prospective applicants as well. Alternative 2 would impose a greater one-time additional cost to the NRC relative to Alternative 1. The one-time cost of Alternative 2 would be offset by the avoidance of the burdens imposed by Alternative 1. Alternative 2 would not impose significant additional costs on applicants relative to Alternative 1 and could possibly result in reduced costs to the prospective applicant relative to Alternative 1.

With respect to safety, Alternative 1 does not signify unsafe results since applicants would adopt methods that would be evaluated by NRC staff on a case-specific basis to establish its reasonable assurance of safety finding. Alternative 2 would be superior to Alternative 1 in that it would result in a new RG to include, where appropriate, updated codes and standards that would maintain and potentially enhance safety, improve clarity, and increase uniformity in application submittals and reviews.

With respect to NRC resources, Alternative 2 represents the greater initial cost to the NRC, which is attributable to the costs associated with preparing and issuing the RG versus the cost of withdrawing the ISG. However, over the lifetime of the RG, the overall NRC cost of

Page 3 Alternative 2 is estimated to be less than the overall cost of Alternative 1 by reducing the cost related to additional NRC staff resources and schedule impacts associated with the application review and RAI procedures.

With respect to applicants resources, Alternative 2 results in fewer costs when compared to Alternative 1. Having a new RG should reduce the need for RAIs and, therefore, the need for applicants to perform additional analyses to address them. Accordingly, costs to applicants associated with these additional activities are estimated to be lower with Alternative

2.

6. Decision Rationale Based on this regulatory analysis, the NRC staff concludes that issuance of a new RG is warranted to reflect the availability of new information and improved analysis methodologies that well served the NRC and stakeholders during the post-Fukushima flooding reevaluations. The NRC staff concludes that the proposed action would enhance NPP safety by providing up-to-date guidance and information on the determination of design basis floods at NPPs. Both prospective applicants (and current licensees) can use the updated guidance to ensure that their reactor designs not only demonstrate compliance with the Commissions regulations and, therefore, are safe, but to effectuate timely and efficient reviews by the NRC staff.