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Federal Register / Vol. 86, No. 150 / Monday, August 9, 2021 / Notices risk-informed approach would provide an equivalent level of assurance for sump performance without incurring significant cost and occupational dose associated with removing, replacing, or reinforcing insulation in containment.
The NRC staff finds that the risk associated with the requested exemptions is consistent with the guidance in RG 1.174 for the use of probabilistic risk assessment and with the Commissions policy statement on safety goals for the operations of nuclear power plants; therefore, the requested exemptions present no undue risk to the public health and safety.

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C. The Exemptions Are Consistent With the Common Defense and Security The requested exemptions would allow the use of a risk-informed methodology to allow SNC to resolve a generic safety concern for PWRs associated with the potential clogging of the ECCS and CSS strainers during certain design-basis events. The proposed change would be adequately controlled by safety acceptance criteria and technical specification requirements and is not related to security issues. Because the common defense and security is not impacted by the requested exemptions, the requested exemptions are consistent with the common defense and security.
D. Special Circumstances Are Present The requested exemptions from 10
CFR 50.46a1 would allow SNC to use a risk-informed methodology in lieu of a deterministic methodology to show conformance with the ECCS and CSS
performance criteria accounting for debris in containment for LOCAs. In its request, SNC cited the special circumstances criteria of 10 CFR
50.12a2ii and iii and stated that application of the regulation in the particular circumstances would not serve the underlying purpose of the rule or is not necessary to achieve the underlying purpose of the rule and that compliance would result in undue hardship or other costs that are significantly in excess of those contemplated when the regulation was adopted, or that are significantly in excess of those incurred by others similarly situated.
The licensee stated that the intent of 10 CFR 50.46a1 is to ensure that ECCS cooling performance design requirements imposed by 10 CFR 50.46
are determined by a rigorous method that provides a high level of confidence in ECCS performance. SNC stated that its proposed risk-informed approach accounts for the effects of debris on the ECCS cooling performance and supports
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a high probability of successful ECCS
performance based on the risk results meeting the acceptance guidelines of RG
1.174.
The licensee also stated that in order to meet a deterministic threshold value for sump debris loads, the debris sources in containment would need to be significantly reduced. SNC stated that the amount of radiological exposure received during the removal and/or modification of insulation from the Vogtle, Units 1 and 2 containments is dependent on the scope of the changes.
The licensee stated that the expected total dose for replacing insulation in Vogtle, Units 1 and 2 is estimated generically to be about 200 roentgen equivalent man rem 100 rem per unit based on the South Texas Project pilot submittal.
The licensee concluded that the special circumstances described in 10
CFR 50.12a2ii and iii would apply to its requested exemptions.
The NRC staff evaluated the exemption request and summarized its evaluation of the proposed riskinformed approach in a safety evaluation ADAMS Accession No.
ML20268A070. Since 10 CFR
50.46a1 requires a deterministic approach, an exemption is an appropriate means to grant the licensee relief to use an alternative, riskinformed approach. The underlying purpose of the regulation is to protect the public health and safety in the event of a LOCA by establishing criteria for the ECCS. In its safety evaluation, the NRC staff concluded, in part, that the licensee adequately demonstrated that the change in risk attributable to debris in postulated LOCAs is very small. The NRC staff also concluded that the licensees proposal for demonstrating compliance with the ECCS and the CSS
performance requirements meets the risk acceptance guidelines in RG 1.174, because the approach is related to a permissible exemption request, is consistent with defense-in-depth philosophy, maintains sufficient safety margins, results in a small increase in risk, and the impact of the approach is monitored by the licensee using performance measurement strategies.
Therefore, the NRC staff finds that the licensees use of the proposed riskinformed approach to consider the impacts of debris meets the underlying intent of 10 CFR 50.46 to ensure that a licensee demonstrates that the ECCS
and the CSS will provide adequate cooling for the reactor core and containment, as well as containment atmosphere cleanup, following postulated design-basis accidents.

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The NRC staff also finds that the licensee demonstrated that using the required deterministic approach as opposed to the proposed risk-informed approach would result in undue hardship or other costs that are significantly in excess of those contemplated when the regulation was adopted, or that are significantly in excess of those incurred by others similarly situated.
Based on the above, the NRC staff concludes that the special circumstances described in 10 CFR
50.12a2ii and iii are present for the requested exemptions.
E. Environmental Considerations The regulations in 10 CFR 51.21, Criteria for and identification of licensing and regulatory actions requiring environmental assessments, generally provide that NRC licensing and regulatory actions require an environmental assessment EA except those identified in 10 CFR 51.20b as requiring an environmental impact statement, those identified in 10 CFR
51.22c as categorical exclusions, and those identified in 10 CFR 51.22d as other actions not requiring environmental review. These regulations also provide that the NRC
may, in special circumstances, prepare an EA on an action covered by a categorical exclusion. Typically, exemptions are identified in 10 CFR
51.22c as categorical exclusions;
however, because the requested exemptions propose a novel riskinformed approach to the requirements in 10 CFR 50.46a1, the NRC staff determined that special circumstances were present and prepared an EA. As discussed in the EA and the associated Finding of No Significant Impact published in the Federal Register on April 7, 2021, 2021 86 FR 18076 and in accordance with 10 CFR 51.31a, the Commission has determined that granting the requested exemptions will not have a significant effect on the quality of the human environment.
IV. Conclusion Accordingly, the Commission has determined, pursuant to 10 CFR 50.12, that the requested exemptions are authorized by law, will not present an undue risk to the public health and safety, and are consistent with the common defense and security and that special circumstances are present.
Therefore, the Commission hereby grants SNCs request for exemptions under 10 CFR 50.12 for Vogtle, Units 1
and 2, from 10 CFR 50.46a1 to allow the use of a risk-informed methodology in lieu of a deterministic methodology
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