Union Electric Company, dba Ameren Missouri, Callaway Plant; Unit No. 1, 65618-65622 [2022-23569]

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[FR Doc. 2022–23758 Filed 10–27–22; 4:15 pm] 10:00 a.m. Briefing on NRC International Activities (Public Meeting) (Contact: Jen Holzman, 301–287–9090) VerDate Sep<11>2014 Week of November 21, 2022—Tentative NUCLEAR REGULATORY COMMISSION [Docket No. 50–483; NRC–2022–0139] Union Electric Company, dba Ameren Missouri, Callaway Plant; Unit No. 1 Nuclear Regulatory Commission. ACTION: Exemption; issuance. AGENCY: The U.S. Nuclear Regulatory Commission (NRC) is granting exemptions from certain portions of the SUMMARY: PO 00000 Frm 00051 Fmt 4703 Sfmt 4703 acceptance criteria for emergency core cooling, and the general design criteria for emergency core cooling, containment heat removal, and atmosphere cleanup to allow the use of a risk-informed analysis to evaluate the effects of debris in containment following a loss-of-coolant accident for the Callaway Plant, Unit No. 1 (Callaway) located in Callaway County, Missouri. The exemptions are in response to a request dated March 31, 2021, from Union Electric Company, doing business as Ameren Missouri (the licensee) related to the licensee’s proposed approach to resolve a generic safety concern for pressurized water reactors associated with potential clogging of emergency core cooling and containment spray system strainers during certain design basis events. DATES: The exemptions were issued on October 21, 2022. ADDRESSES: Please refer to Docket ID NRC–2022–0139 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 https://www.regulations.gov and search for Docket ID NRC–2022–0139. Address questions about Docket IDs in Regulations.gov to Stacy Schumann; telephone: 301–415–0624; email: Stacy.Schumann@nrc.gov. 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 https://www.nrc.gov/reading-rm/ adams.html. To begin the search, 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 PDR.Resource@nrc.gov. The request for the exemptions was submitted by letter dated March 31, 2021, as supplemented by letters dated May 27, 2021, July 22, 2021, August 23, 2021, October 7, 2021, January 27, 2022, March 8, 2022, May 26, 2022, and September 8, 2022. For the convenience of the reader, instructions about obtaining materials referenced in this document are provided in the ‘‘Availability of Documents’’ section. • NRC’s PDR: You may examine and purchase copies of public documents, by appointment, at the NRC’s PDR, Room P1 B35, One White Flint North, E:\FR\FM\31OCN1.SGM 31OCN1 65619 Federal Register / Vol. 87, No. 209 / Monday, October 31, 2022 / Notices 11555 Rockville Pike, Rockville, Maryland 20852. To make an appointment to visit the PDR, please send an email to PDR.Resource@nrc.gov or call 1–800–397–4209 or 301–415– 4737, between 8:00 a.m. and 4:00 p.m. Eastern Time (ET), Monday through Friday, except Federal holidays. FOR FURTHER INFORMATION CONTACT: I. Availability of Documents Mahesh Chawla, Office of Nuclear Reactor Regulation, U.S. Nuclear Regulatory Commission, Washington, DC 20555–0001, telephone: 301–415– 8371, email: Mahesh.Chawla@nrc.gov. The documents identified in the following table are available to interested persons through one or more of the following methods, as indicated. ADAMS accession No. Document Ameren Missouri, letter to U.S. Nuclear Regulatory Commission, ‘‘Callaway Plant, Unit 1, Request for License Amendment and Regulatory Exemptions for a Risk-Informed Approach to Address GSI–191 and Respond to GL 2004–02 (LDCN 19–0014),’’ dated March 31, 2021. Ameren Missouri, letter to U.S. Nuclear Regulatory Commission, ‘‘Callaway Plant, Unit 1, Supplement to Request for Licence Amendment and Regulatory Exemptions for a Risk-Informed Approach to Address GSI–191 and Respond to GL 2004–02 (LDCN 19–0014),’’ dated May 27, 2021. Ameren Missouri, letter to U.S. Nuclear Regulatory Commission, ‘‘Callaway Plant, Unit 1, Supplement to Request for License Amendment and Regulatory Exemptions for a Risk-Informed Approach to Address GSI–191 and Respond to GL–2004–02 (LDCN 19–0014),’’ dated July 22, 2021. Ameren Missouri, letter to U.S. Nuclear Regulatory Commission, ‘‘Callaway Plant, Unit 1, Transmittal of Documents Identified from NRC Audit of License Amendment Request Regarding Risk-Informed approach to Closure of Generic Safety Issue 191 (EPID L–2021–LLA–0059),’’ dated August 23, 2021. Ameren Missouri, letter to U.S. Nuclear Regulatory Commission, ‘‘Callaway Plant, Unit 1, Third Supplement to Request for License Amendment and Regulatory Exemptions for a Risk-Informed Approach to Address GSI–191 and Respond to GL–2004–02 (LDCN 19–0014) (EPID L–2021–LLA–0059 and EPID L–2021–LLE–0021),’’ dated October 7, 2021. Ameren Missouri, letter to U.S. Nuclear Regulatory Commission, ‘‘Callaway Plant, Unit 1, Fourth Supplement to Request for License Amendment and Regulatory Exemptions for a Risk-Informed Approach to Address GSI–191 and Respond to GL–2004–02 (LDCN 19–0014) (EPID L–2021–LLA–0059 and EPID L–2021–LLE–0021),’’ dated January 27, 2022. Ameren Missouri, letter to U.S. Nuclear Regulatory Commission, ‘‘Callaway Plant, Unit 1, Fifth (Post-Audit) Supplement to Request for License Amendment and Regulatory Exemptions for a Risk-Informed Approach to Address GSI–191 and Respond to GL 2004–02 (LDCN 19–0014) (EPID L–2021–LLA–0059 and EPID L–2021–LLE– 0021),’’ dated March 8, 2022. Ameren Missouri, letter to U.S. Nuclear Regulatory Commission, ‘‘Callaway Plant, Unit 1, Response to Request for Additional Information Regarding Request for License Amendment and Regulatory Exemptions for Risk-Informed Approach to Address GSI–191 and Respond to Generic Letter 2004–02 (LDCN 19–0014) (EPID L–2021–LLA– 0059 and EPID L–2021–LLE–0021),’’ dated May 26, 2022. Ameren Missouri, letter to U.S. Nuclear Regulatory Commission, ‘‘Callaway Plant, Unit 1, Correction of Text Contained in Enclosures Provided with Supplements to Request for License Amendment and Regulatory Exemptions for a Risk-Informed Approach to Address GSI–191 and Respond to Generic Letter 2004–02 (LDCN 19–0014) (EPID L–2021–LLA–0059 and EPID L–2021–LLE–0021),’’ dated September 8, 2022. SUPPLEMENTARY INFORMATION: The text of the exemption is attached. Dated: October 25, 2022. For the Nuclear Regulatory Commission. Mahesh L. Chawla, Project Manager, Plant Licensing Branch IV, Division of Operating Reactor Licensing, Office of Nuclear Reactor Regulation. Attachment—Exemption Nuclear Regulatory Commission Docket No. 50–483 khammond on DSKJM1Z7X2PROD with NOTICES Union Electric Company, Callaway Plant, Unit No. 1, Exemptions I. Background Union Electric Company, doing business as (dba) as Ameren Missouri (the licensee), is the holder of Renewed Facility Operating License No. NPF–30, which authorizes operation of the Callaway Plant, Unit No. 1 (Callaway). The license provides, among other things, that the facility is subject to all rules, regulations, and orders of the U.S. Nuclear Regulatory Commission (NRC) now or hereafter in effect. The facility consists of VerDate Sep<11>2014 17:15 Oct 28, 2022 Jkt 259001 a pressurized-water reactor (PWR) located in Callaway County, Missouri. In 1996, the NRC identified Generic Safety Issue (GSI)–191, ‘‘Assessment of Debris Accumulation on PWR Sump Performance,’’ associated with the effects of debris accumulation on PWR sump performance during design-basis accidents. As part of the actions to resolve GSI–191, the NRC issued Generic Letter (GL) 2004–02, ‘‘Potential Impact of Debris Blockage on Emergency Recirculation during Design Basis Accidents at Pressurized-Water Reactors,’’ dated September 13, 2004 (ML042360586), to holders of operating licenses for PWRs. In GL 2004–02, the NRC staff requested that licensees perform an evaluation of their emergency core cooling systems (ECCS) and containment spray system (CSS) recirculation functions considering the potential for debris-laden coolant to be circulated by the ECCS and the CSS after a loss-of-coolant accident (LOCA) or high energy line break inside containment and, if appropriate, take additional actions to ensure system function. GL 2004–02 required that licensees provide a written response to the NRC, pursuant to Title 10 of the Code of Federal Regulations (10 CFR) Section 50.54(f), describing the PO 00000 Frm 00052 Fmt 4703 Sfmt 4703 ML21090A184 (Package). ML21147A222. ML21203A192 (Package). ML21237A135 (Package). ML21280A378 (Package). ML22027A804 (Package). ML22068A027 (Package). ML22146A337 (Package). ML22251A343. results of their evaluation and any modifications made, or planned, to ensure the ECCS and CSS remain functional. II. Request/Action By application dated March 31, 2021, (Agencywide Documents Access and Management System (ADAMS) Accession No. ML21090A184), as supplemented by letters dated May 27, 2021, July 22, 2021, August 23, 2021, October 7, 2021, January 27, 2022, March 8, 2022, May 26, 2022, and September 8, 2022 (ML21147A222, ML21203A192, ML21237A135, ML21280A378, ML22027A804, ML22068A027, ML22146A337, and ML22251A343, respectively), the licensee, pursuant to 10 CFR 50.12, ‘‘Specific exemptions,’’ requested exemptions from certain requirements of 10 CFR 50.46, ‘‘Acceptance criteria for emergency core cooling systems for light-water nuclear power reactors,’’ and 10 CFR part 50, Appendix A, General Design Criterion (GDC) 35, ‘‘Emergency core cooling’’; GDC 38, ‘‘Containment heat removal’’; and GDC 41, ‘‘Containment atmosphere cleanup,’’ to allow use of a risk-informed methodology instead of the traditional deterministic methodology, E:\FR\FM\31OCN1.SGM 31OCN1 khammond on DSKJM1Z7X2PROD with NOTICES 65620 Federal Register / Vol. 87, No. 209 / Monday, October 31, 2022 / Notices to resolve the concerns associated with GSI– 191, and respond to GL 2004–02 for Callaway. Specifically, the licensee requested exemptions from 10 CFR 50.46(a)(1)(i), which, in part, requires the ECCS cooling performance to be calculated in accordance with an acceptable evaluation model as described in 10 CFR 50.46(a)(1), and for postulated LOCAs of different sizes, locations and other properties sufficient to provide assurance that the most severe LOCAs are evaluated. The NRC staff interprets the Section 50.46(a)(1) requirement to calculate ECCS performance for ‘‘other properties’’ as requiring licensees to consider the impacts of debris generation and transport in containment. The most significant form of debris in nuclear power reactor containments is piping and component insulation that can become debris during LOCAs, transport and accumulate in the sumps, and clog the sumps strainers, thus creating resistance to coolant flow. Fibrous debris from this insulation can also enter the reactor core and directly impede heat transfer from the fuel to the coolant. The approval of a risk-informed methodology would require exemptions from 10 CFR 50.46(a)(1)(i) and GDCs 35, 38, and 41 because the NRC has interpreted these regulations as requiring a deterministic approach and bounding calculation to show compliance with ECCS and CSS performance criteria in 10 CFR 50.46(b) and GDCs 35, 38, and 41. Issuance of exemptions is an appropriate means to grant relief from the use of a deterministic approach to show compliance with these requirements. The licensee’s 10 CFR 50.46 deterministic analysis considered the debris in containment and demonstrated that the debris loading could prevent acceptable ECCS and CSS operation and core cooling for certain pipe ruptures. Based on its analysis, the licensee concluded that the amount of debris in the Callaway containment would need to be reduced to demonstrate compliance with 10 CFR 50.46 criteria using a deterministic analysis for certain largebreak LOCA sizes because, for those breaks, the plant-specific testing threshold for generation and transport of debris was exceeded. Additionally, the licensee’s deterministic in-vessel analysis was limited to breaks that could generate and transport to the strainers fibrous debris amounts in excess of the plantspecific tested debris limit for the strainers. This value was chosen because it also represents the deterministic limit for strainer failure for pipe breaks. Therefore, any break that generates and transports more than the amount of fibrous debris bounded by plant testing is already assumed to cause strainer failure and increase core damage frequency. Because these large breaks are already assumed to contribute to plant risk because of strainer failure, there is no need to evaluate them for risk contribution due to invessel failure. Other debris types were bounded by the strainer evaluation and are not critical to the in-vessel analysis. Therefore, all cases where core damage might occur due to debris arriving at the core are already covered by scenarios that cause VerDate Sep<11>2014 17:15 Oct 28, 2022 Jkt 259001 strainer failure and do not need to be counted as additional increases in risk. The licensee requested exemptions from the requirement to use a deterministic analysis for specific scenarios of LOCA breaks producing and transporting debris in excess of the plant-specific tested debris limits. Since it determined that the probability of consequences from debris effects is very low, the licensee requested exemptions to allow the use of a riskinformed analysis to show adequate assurance of ECCS and CSS functionality, in accordance with the criteria in Regulatory Guide (RG) 1.174, Revision 3, ‘‘An Approach for Using Probabilistic Risk Assessment in Risk-Informed Decisions on Plant-Specific Changes to the Licensing Basis,’’ dated January 2018 (ML17317A256). RG 1.174 was developed in consideration of the Commission’s Policy Statements on safety goals 1 and the use of probabilistic risk assessment methods in nuclear regulatory activities.2 Therefore, RG 1.174 provides an acceptable method for licensees and NRC staff to use in assessing the impact of licensing basis changes when the licensee chooses to use risk information. The requirements in GDC 35 require, in part, that the ECCS safety system functions adequately to transfer heat from the reactor core following a LOCA and in the presence of a worst single failure, at a rate such that (a) fuel and clad damage that could interfere with continued effective core cooling is prevented and (b) clad metal-water reactor is limited to negligible amounts. The licensee stated in its application dated March 31, 2021, that the function of the ECCS emergency sump is assumed to fail for scenarios where debris exceeds the amount determined in acceptable plant-specific testing. Failure of the sump and strainers results in loss of cooling to the core. The licensee requested exemptions from the requirements of GDC 35, which requires the use of a deterministic approach, for those LOCA breaks that exceed the plant-specific testing debris threshold. The licensee requested exemptions from the deterministic requirements of GDC 35, to allow the use of a risk-informed analysis, in accordance with the criteria in RG 1.174, to show that the risk from debris effects is very low. The requirements in GDC 38 require containment heat removal, rapid reduction of containment pressure and temperature, and maintenance of pressure and temperature at an acceptably low level following a LOCA, and in the presence of a single failure, to preserve containment function. The licensee proposed that exemptions be granted from the requirements in GDC 38 that specify the use of a deterministic approach. The request applies only to those LOCA breaks that exceed the plant-specific testing debris threshold. Current Callaway design basis 1 Commission’s Safety Goal Policy Statement, ‘‘Safety Goals for the Operations of Nuclear Power Plants; Policy Statement,’’ published in the Federal Register on August 4, 1986 (51 FR 28044), as corrected, and republished, on August 21, 1986 (51 FR 30028). 2 Use of Probabilistic Risk Assessment Methods in Nuclear Activities; Final Policy Statement,’’ August 16, 1995 (60 FR 42622). PO 00000 Frm 00053 Fmt 4703 Sfmt 4703 calculations are based on the containment cooling system (containment fan coolers) functioning in conjunction with the CSS and ECCS, both of which can be affected by debris. Using deterministic assumptions, the licensee’s analysis and testing does not assure that the emergency sump strainers will be available to support the CSS and ECCS function considering the effects of debris produced by those breaks that can generate and transport debris amounts greater than the plant-specific testing threshold. The licensee requested exemptions from the deterministic requirements of GDC 38 to allow the use of a risk-informed analysis, in accordance with the criteria in RG 1.174, to show that the risk from debris effects is very low. The requirements in GDC 41, require, in part, containment atmosphere cleanup to control substances that may be released into the reactor containment, to reduce the concentration and quality of fission products released to the environment following postulated accidents, and to control the concentration of hydrogen or oxygen and other substances in the containment atmosphere following postulated accidents, assuming a single failure. The licensee stated that using deterministic assumptions, its analysis and testing cannot demonstrate that the emergency sump strainers will be available to support the CSS function considering the effects of debris produced and transported by breaks not bounded by acceptable plant-specific testing. The licensee requested exemptions from the deterministic requirements of GDC 41 to allow the use of a risk-informed analysis, in accordance with the criteria in RG 1.174, to show that the risk from debris effects is very low. III. Discussion Pursuant to 10 CFR 50.12, the Commission may, upon application by any interested person or upon its own initiative, grant exemptions from the requirements of 10 CFR part 50, when (1) the exemptions are authorized by law, will not present an undue risk to public health or safety, and are consistent with the common defense and security; and (2) when special circumstances are present. Under 10 CFR 50.12(a)(2)(ii), special circumstances are present when ‘‘[a]pplication 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.’’ The licensee proposed to use a riskinformed methodology instead of a deterministic approach to account for the effects of debris in containment for portions of the LOCA analysis applicable to breaks that exceed the Callaway plant-specific debris testing threshold. The licensee’s methodology, termed Risk over Deterministic, or RoverD, divides the loss of core cooling design-basis analysis into two portions: the ‘‘deterministic analysis’’ and the ‘‘risk-informed analysis.’’ The riskinformed analysis is used by the licensee for breaks that generate and transport debris exceeding the plant-specific testing threshold. These breaks result in fibrous E:\FR\FM\31OCN1.SGM 31OCN1 Federal Register / Vol. 87, No. 209 / Monday, October 31, 2022 / Notices debris estimated to arrive in the ECCS sump post-LOCA in amounts that are equal to or greater than the amount of fiber used in acceptable strainer testing. The acceptable limit was determined using testing methods intended to determine the maximum ECCS strainer head loss for the tested condition. Also, the licensee evaluated the in-core aspects of fibrous debris to prevent adequate fuel cooling. The licensee found that for invessel effects, all breaks that generate and transport fibrous debris amounts less than the strainer acceptance criterion can be evaluated deterministically and shown to have acceptable outcomes. Therefore, the invessel effects do not contribute to changes in core damage frequency. For ECCS and CSS analyses other than the postulated largebreak LOCAs that generate less than the strainer acceptance limit, the licensee applied a deterministic methodology. If the exemptions were granted for these postulated breaks, the requirement to use a deterministic methodology for all other postulated LOCA breaks would continue to apply. khammond on DSKJM1Z7X2PROD with NOTICES A. The Exemptions Are Authorized by Law The exemptions would allow the use of a risk-informed methodology to show compliance with 10 CFR 50.46(a)(1)(i), and GDCs 35, 38, and 41 of Appendix A to 10 CFR part 50, when considering debris in containment generated and transported by those breaks that exceed the plant-specific testing threshold. These regulations were promulgated under and are consistent with the Commission’s authority under Section 161 of the Atomic Energy Act of 1954, as amended. Because the application of a riskinformed methodology to show compliance with 10 CFR 50.46, and GDC 35, 38, and 41 of Appendix A to 10 CFR part 50, would not violate the Atomic Energy Act of 1954, as amended, or the Commission’s regulations, the exemptions are authorized by law provided all requisite findings are made. B. The Exemptions Present No Undue Risk to Public Health and Safety The provisions of 10 CFR 50.46 and GDCs 35, 38, and 41 of Appendix A to 10 CFR part 50 establish criteria for the emergency core cooling, containment cooling, and containment atmosphere cleanup system performance. As part of the amendment request, the licensee submitted exemption requests to change its design-basis analysis specified in the Updated Final Safety Analysis Report (UFSAR) to allow use of risk-informed and deterministic methodologies to specifically account for the impacts of debris in containment. The licensee justified its use of the risk-informed approach by stating that the proposed riskinformed approach meets the key principles in RG 1.174, Revision 3, in that it is consistent with defense-in-depth philosophy, maintains sufficient safety margins, results in a small increase in risk, and is monitored by the licensee using performance measurement strategies. Additionally, the licensee stated that the proposed exemptions, to allow use of the risk-informed method, are consistent with Key Principle 1 in RG 1.174 that requires a proposed change to the licensing basis (or VerDate Sep<11>2014 17:15 Oct 28, 2022 Jkt 259001 amendment) to meet current regulations unless the change is explicitly related to requested exemptions. The probabilistic risk analysis results provided by the licensee and evaluated by the NRC staff in its safety evaluation, showed that the increase in risk associated with debris generation and transport on ECCS and CSS function following postulated LOCAs is very small, in accordance with the criteria in RG 1.174. The NRC staff concluded that the risk is consistent with the guidance in RG 1.174 and with the Commission policy statements on safety goals and the use of probabilistic risk assessment methods in nuclear regulatory activities; therefore, the requested exemptions present no undue risk to public health and safety. C. The Exemptions Are Consistent With the Common Defense and Security The requested exemptions would allow the licensee to use a risk-informed methodology to resolve a generic safety concern for PWRs associated with potential clogging of the ECCS and CSS strainers during certain design-basis events. The change is 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 exemptions, the exemptions are consistent with the common defense and security. D. Special Circumstances Under the regulations in 10 CFR 50.12, the Commission may grant exemptions from the requirements of 10 CFR part 50 provided certain findings are made; namely, that special circumstances are present, the exemptions present no undue risk to public health and safety, the exemptions are consistent with the common defense and security, and the exemptions are authorized by law. The exemptions would allow the use of a risk-informed methodology to show compliance with 10 CFR 50.46(a)(1)(i), and GDCs 35, 38, and 41 of Appendix A to 10 CFR part 50, specifically for the analyses of debris in containment impacting emergency cooling function during postulated largebreak LOCAs that exceed the plant-specific testing threshold. The licensee requested exemptions citing the special circumstances criteria of 10 CFR 50.12(a)(2)(ii), because compliance 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. The licensee cited these special circumstances for all of the requested exemptions. The licensee stated that an objective of each of the regulations for which exemptions are proposed is to maintain low risk to the public health and safety through the adequate functioning of the ECCS and CSS safety systems. These systems must be supported by adequate functioning of the containment sumps. The regulations in 10 CFR 50.46(a)(1)(i) and GDCs 35, 38, and 41 of Appendix A to 10 CFR part 50 are met when the licensee can demonstrate, using a bounding calculation or other deterministic method that the ECCS and CSS are capable PO 00000 Frm 00054 Fmt 4703 Sfmt 4703 65621 of functioning during design basis events. The licensee stated that its risk-informed analysis to show adequate functioning of ECCS and CSS, considering the impacts of debris during certain LOCA events, demonstrates that the ECCS and CSS systems will operate with a high degree of reliability. The licensee stated that special circumstances exist because the underlying intent of the regulations, to ensure adequate protection of public health and safety is met when applying a risk-informed approach to address GSI–191 and responding to GL 2004– 02. Further, it states that the risk-informed approach is consistent with RG 1.174 and supports operation of those functions with a high degree of reliability. Thus, the licensee concludes that the underlying intent of each regulation is met, and the special circumstances described in 10 CFR 50.12(a)(2)(ii) apply to each of the exemptions proposed by the licensee. The NRC staff evaluated the licensee’s application, as supplemented and discussed the details of its evaluation of the riskinformed approach in an NRC safety evaluation available under ADAMS Accession No. ML22220A132. Although 10 CFR 50.46(a)(1) requires a deterministic approach, the GDCs do not specify that a risk-informed methodology may not be used to show compliance; however, because the NRC has interpreted each of these regulations as requiring a deterministic approach, exemptions are an appropriate means to grant the licensee relief to use an alternative approach. The underlying purpose of each regulation is to protect public health and safety in the event of a LOCA by establishing criteria for emergency core cooling, containment cooling and containment atmosphere cleanup system performance. In its safety evaluation, the NRC staff concluded, in part, that the licensee adequately demonstrated that the change in risk attributable to debris that exceed the plant specific threshold is very small and meets the risk acceptance guidelines in RG 1.174. The NRC staff also concluded that the analysis is consistent with defense-in-depth philosophy, maintains sufficient safety margins, results in a small increase in risk, and is monitored by the licensee using performance measurement strategies. Therefore, the licensee’s use of the riskinformed analysis meets the underlying requirements of 10 CFR 50.46 and GDCs 35, 38, and 41 of Appendix A to 10 CFR part 50, to ensure that a licensee demonstrates that the ECCS and CSS will provide adequate cooling for the reactor core and containment and provide containment atmosphere cleanup during design-basis accidents considering the impacts of debris, since it meets the guidelines in RG 1.174. Based on the above, the NRC staff concludes that special circumstances under 10 CFR 50.12(a)(2)(ii) exist because compliance with the deterministic requirements of 10 CFR 50.46(a)(1)(i), and GDCs 35, 38, and 41 of Appendix A to 10 CFR part 50 is not necessary to achieve the underlying purpose of each rule. E. Supplemental Information For more technical details, refer to the SE associated with these exemptions under E:\FR\FM\31OCN1.SGM 31OCN1 65622 Federal Register / Vol. 87, No. 209 / Monday, October 31, 2022 / Notices ADAMS Accession No. ML22220A130 (enclosure 2). ACTION: F. Environmental Considerations Pursuant to 10 CFR 51.21, ‘‘Criteria for and identification of licensing and regulatory actions requiring environmental assessments,’’ the NRC has prepared an environmental assessment (EA) and finding of no significant impact (FONSI) summarizing the findings of its review of the environmental impacts of the proposed action under the National Environmental Policy Act (NEPA). The NRC staff determined that special circumstances under 10 CFR 51.21 exist to warrant preparation of an EA and FONSI because Callaway is proposing a risk-informed approach to resolve GSI–191 as recognized in Staff Requirement Memorandum SECY–12–0093, ‘‘Closure Options for Generic Safety Issue—191, Assessment of Debris Accumulation on Pressurized-Water Reactor Sump Performance,’’ dated December 14, 2012 (ML12349A378). Because this action uses risk information to justify exemptions from deterministic regulations, the NRC staff considered preparations of an EA and FONSI to be a prudent course of action that would further the purposes of NEPA. Based on its review, the NRC concluded that an environmental impact statement is not required and that the proposed action will have no significant impact on the environment. The NRC published a final EA and FONSI on the proposed action in the Federal Register on August 29, 2022 (87 FR 52816). IV. Conclusions Accordingly, the Commission has determined that, pursuant to 10 CFR 50.12, exemptions are authorized by law, will not present an undue risk to the public health and safety, are consistent with the common defense and security, and special circumstances are present pursuant to 10 CFR 50.12(a)(2)(ii). Therefore, the NRC hereby grants Union Electric Company, dba Ameren Missouri, one-time exemptions from 10 CFR 50.46(a)(1), and 10 CFR part 50, Appendix A, GDCs 35, 38, and 41 to allow the use of 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 those breaks that exceed the plant-specific Callaway testing threshold. Dated at Rockville, Maryland, this 21st day of October 2022. For the Nuclear Regulatory Commission. Gregory F. Suber, Deputy Director, Division of Operating Reactor Licensing, Office of Nuclear Reactor Regulation. khammond on DSKJM1Z7X2PROD with NOTICES [FR Doc. 2022–23569 Filed 10–28–22; 8:45 am] BILLING CODE 7590–01–P POSTAL REGULATORY COMMISSION Notice. The Commission is noticing a recent Postal Service filing for the Commission’s consideration concerning a negotiated service agreement. This notice informs the public of the filing, invites public comment, and takes other administrative steps. DATES: Comments are due: November 2, 2022. ADDRESSES: Submit comments electronically via the Commission’s Filing Online system at https:// www.prc.gov. Those who cannot submit comments electronically should contact the person identified in the FOR FURTHER INFORMATION CONTACT section by telephone for advice on filing alternatives. SUMMARY: FOR FURTHER INFORMATION CONTACT: David A. Trissell, General Counsel, at 202–789–6820. SUPPLEMENTARY INFORMATION: Table of Contents I. Introduction II. Docketed Proceeding(s) I. Introduction The Commission gives notice that the Postal Service filed request(s) for the Commission to consider matters related to negotiated service agreement(s). The request(s) may propose the addition or removal of a negotiated service agreement from the market dominant or the competitive product list, or the modification of an existing product currently appearing on the market dominant or the competitive product list. Section II identifies the docket number(s) associated with each Postal Service request, the title of each Postal Service request, the request’s acceptance date, and the authority cited by the Postal Service for each request. For each request, the Commission appoints an officer of the Commission to represent the interests of the general public in the proceeding, pursuant to 39 U.S.C. 505 (Public Representative). Section II also establishes comment deadline(s) pertaining to each request. The public portions of the Postal Service’s request(s) can be accessed via the Commission’s website (https:// www.prc.gov). Non-public portions of the Postal Service’s request(s), if any, can be accessed through compliance with the requirements of 39 CFR 3011.301.1 [Docket Nos. MC2023–26 and CP2023–25] New Postal Products AGENCY: Postal Regulatory Commission. VerDate Sep<11>2014 17:15 Oct 28, 2022 Jkt 259001 1 See Docket No. RM2018–3, Order Adopting Final Rules Relating to Non-Public Information, June 27, 2018, Attachment A at 19–22 (Order No. 4679). PO 00000 Frm 00055 Fmt 4703 Sfmt 4703 The Commission invites comments on whether the Postal Service’s request(s) in the captioned docket(s) are consistent with the policies of title 39. For request(s) that the Postal Service states concern market dominant product(s), applicable statutory and regulatory requirements include 39 U.S.C. 3622, 39 U.S.C. 3642, 39 CFR part 3030, and 39 CFR part 3040, subpart B. For request(s) that the Postal Service states concern competitive product(s), applicable statutory and regulatory requirements include 39 U.S.C. 3632, 39 U.S.C. 3633, 39 U.S.C. 3642, 39 CFR part 3035, and 39 CFR part 3040, subpart B. Comment deadline(s) for each request appear in section II. II. Docketed Proceeding(s) 1. Docket No(s).: MC2023–26 and CP2023–25; Filing Title: USPS Request to Add Priority Mail & First-Class Package Service Contract 223 to Competitive Product List and Notice of Filing Materials Under Seal; Filing Acceptance Date: October 25, 2022; Filing Authority: 39 U.S.C. 3642, 39 CFR 3040.130 through 3040.135, and 39 CFR 3035.105; Public Representative: Arif Hafiz; Comments Due: November 2, 2022. This Notice will be published in the Federal Register. Erica A. Barker, Secretary. [FR Doc. 2022–23672 Filed 10–28–22; 8:45 am] BILLING CODE 7710–FW–P OFFICE OF SCIENCE AND TECHNOLOGY POLICY Framing the National Nature Assessment Office of Science and Technology Policy (OSTP). ACTION: Notice of request for information. AGENCY: Nature is important in its own right, and provides value to the lives of all Americans. To increase our knowledge of nature in the United States and its links to global change, the Office of Science and Technology Policy (OSTP), on behalf of the United States Global Change Research Program (USGCRP), requests input from the public to help inform the framing, development, and eventual use of the first National Nature Assessment (NNA). USGCRP committed to conducting a National Nature Assessment on April 8, 2022, under the authority of the Global Change Research Act of 1990. President Biden reinforced and elevated the SUMMARY: E:\FR\FM\31OCN1.SGM 31OCN1

Agencies

[Federal Register Volume 87, Number 209 (Monday, October 31, 2022)]
[Notices]
[Pages 65618-65622]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2022-23569]


-----------------------------------------------------------------------

NUCLEAR REGULATORY COMMISSION

[Docket No. 50-483; NRC-2022-0139]


Union Electric Company, dba Ameren Missouri, Callaway Plant; Unit 
No. 1

AGENCY: Nuclear Regulatory Commission.

ACTION: Exemption; issuance.

-----------------------------------------------------------------------

SUMMARY: The U.S. Nuclear Regulatory Commission (NRC) is granting 
exemptions from certain portions of the acceptance criteria for 
emergency core cooling, and the general design criteria for emergency 
core cooling, containment heat removal, and atmosphere cleanup to allow 
the use of a risk-informed analysis to evaluate the effects of debris 
in containment following a loss-of-coolant accident for the Callaway 
Plant, Unit No. 1 (Callaway) located in Callaway County, Missouri. The 
exemptions are in response to a request dated March 31, 2021, from 
Union Electric Company, doing business as Ameren Missouri (the 
licensee) related to the licensee's proposed approach to resolve a 
generic safety concern for pressurized water reactors associated with 
potential clogging of emergency core cooling and containment spray 
system strainers during certain design basis events.

DATES: The exemptions were issued on October 21, 2022.

ADDRESSES: Please refer to Docket ID NRC-2022-0139 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 https://www.regulations.gov and search for Docket ID NRC-2022-0139. Address 
questions about Docket IDs in Regulations.gov to Stacy Schumann; 
telephone: 301-415-0624; email: [email protected]. 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 https://www.nrc.gov/reading-rm/adams.html. To begin the search, 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 [email protected]. The request for the exemptions was 
submitted by letter dated March 31, 2021, as supplemented by letters 
dated May 27, 2021, July 22, 2021, August 23, 2021, October 7, 2021, 
January 27, 2022, March 8, 2022, May 26, 2022, and September 8, 2022. 
For the convenience of the reader, instructions about obtaining 
materials referenced in this document are provided in the 
``Availability of Documents'' section.
     NRC's PDR: You may examine and purchase copies of public 
documents, by appointment, at the NRC's PDR, Room P1 B35, One White 
Flint North,

[[Page 65619]]

11555 Rockville Pike, Rockville, Maryland 20852. To make an appointment 
to visit the PDR, please send an email to [email protected] or call 
1-800-397-4209 or 301-415-4737, between 8:00 a.m. and 4:00 p.m. Eastern 
Time (ET), Monday through Friday, except Federal holidays.

FOR FURTHER INFORMATION CONTACT: Mahesh Chawla, Office of Nuclear 
Reactor Regulation, U.S. Nuclear Regulatory Commission, Washington, DC 
20555-0001, telephone: 301-415-8371, email: [email protected].

I. Availability of Documents

    The documents identified in the following table are available to 
interested persons through one or more of the following methods, as 
indicated.

----------------------------------------------------------------------------------------------------------------
                          Document                                           ADAMS accession No.
----------------------------------------------------------------------------------------------------------------
Ameren Missouri, letter to U.S. Nuclear Regulatory           ML21090A184 (Package).
 Commission, ``Callaway Plant, Unit 1, Request for License
 Amendment and Regulatory Exemptions for a Risk-Informed
 Approach to Address GSI-191 and Respond to GL 2004-02
 (LDCN 19-0014),'' dated March 31, 2021.
Ameren Missouri, letter to U.S. Nuclear Regulatory           ML21147A222.
 Commission, ``Callaway Plant, Unit 1, Supplement to
 Request for Licence Amendment and Regulatory Exemptions
 for a Risk-Informed Approach to Address GSI-191 and
 Respond to GL 2004-02 (LDCN 19-0014),'' dated May 27, 2021.
Ameren Missouri, letter to U.S. Nuclear Regulatory           ML21203A192 (Package).
 Commission, ``Callaway Plant, Unit 1, Supplement to
 Request for License Amendment and Regulatory Exemptions
 for a Risk-Informed Approach to Address GSI-191 and
 Respond to GL-2004-02 (LDCN 19-0014),'' dated July 22,
 2021.
Ameren Missouri, letter to U.S. Nuclear Regulatory           ML21237A135 (Package).
 Commission, ``Callaway Plant, Unit 1, Transmittal of
 Documents Identified from NRC Audit of License Amendment
 Request Regarding Risk-Informed approach to Closure of
 Generic Safety Issue 191 (EPID L-2021-LLA-0059),'' dated
 August 23, 2021.
Ameren Missouri, letter to U.S. Nuclear Regulatory           ML21280A378 (Package).
 Commission, ``Callaway Plant, Unit 1, Third Supplement to
 Request for License Amendment and Regulatory Exemptions
 for a Risk-Informed Approach to Address GSI-191 and
 Respond to GL-2004-02 (LDCN 19-0014) (EPID L-2021-LLA-0059
 and EPID L-2021-LLE-0021),'' dated October 7, 2021.
Ameren Missouri, letter to U.S. Nuclear Regulatory           ML22027A804 (Package).
 Commission, ``Callaway Plant, Unit 1, Fourth Supplement to
 Request for License Amendment and Regulatory Exemptions
 for a Risk-Informed Approach to Address GSI-191 and
 Respond to GL-2004-02 (LDCN 19-0014) (EPID L-2021-LLA-0059
 and EPID L-2021-LLE-0021),'' dated January 27, 2022.
Ameren Missouri, letter to U.S. Nuclear Regulatory           ML22068A027 (Package).
 Commission, ``Callaway Plant, Unit 1, Fifth (Post-Audit)
 Supplement to Request for License Amendment and Regulatory
 Exemptions for a Risk-Informed Approach to Address GSI-191
 and Respond to GL 2004-02 (LDCN 19-0014) (EPID L-2021-LLA-
 0059 and EPID L-2021-LLE-0021),'' dated March 8, 2022.
Ameren Missouri, letter to U.S. Nuclear Regulatory           ML22146A337 (Package).
 Commission, ``Callaway Plant, Unit 1, Response to Request
 for Additional Information Regarding Request for License
 Amendment and Regulatory Exemptions for Risk-Informed
 Approach to Address GSI-191 and Respond to Generic Letter
 2004-02 (LDCN 19-0014) (EPID L-2021-LLA-0059 and EPID L-
 2021-LLE-0021),'' dated May 26, 2022.
Ameren Missouri, letter to U.S. Nuclear Regulatory           ML22251A343.
 Commission, ``Callaway Plant, Unit 1, Correction of Text
 Contained in Enclosures Provided with Supplements to
 Request for License Amendment and Regulatory Exemptions
 for a Risk-Informed Approach to Address GSI-191 and
 Respond to Generic Letter 2004-02 (LDCN 19-0014) (EPID L-
 2021-LLA-0059 and EPID L-2021-LLE-0021),'' dated September
 8, 2022.
----------------------------------------------------------------------------------------------------------------


SUPPLEMENTARY INFORMATION: The text of the exemption is attached.

    Dated: October 25, 2022.

    For the Nuclear Regulatory Commission.
Mahesh L. Chawla,
Project Manager, Plant Licensing Branch IV, Division of Operating 
Reactor Licensing, Office of Nuclear Reactor Regulation.

Attachment--Exemption

Nuclear Regulatory Commission

Docket No. 50-483

Union Electric Company, Callaway Plant, Unit No. 1, Exemptions

I. Background

    Union Electric Company, doing business as (dba) as Ameren 
Missouri (the licensee), is the holder of Renewed Facility Operating 
License No. NPF-30, which authorizes operation of the Callaway 
Plant, Unit No. 1 (Callaway). The license provides, among other 
things, that the facility is subject to all rules, regulations, and 
orders of the U.S. Nuclear Regulatory Commission (NRC) now or 
hereafter in effect. The facility consists of a pressurized-water 
reactor (PWR) located in Callaway County, Missouri.
    In 1996, the NRC identified Generic Safety Issue (GSI)-191, 
``Assessment of Debris Accumulation on PWR Sump Performance,'' 
associated with the effects of debris accumulation on PWR sump 
performance during design-basis accidents. As part of the actions to 
resolve GSI-191, the NRC issued Generic Letter (GL) 2004-02, 
``Potential Impact of Debris Blockage on Emergency Recirculation 
during Design Basis Accidents at Pressurized-Water Reactors,'' dated 
September 13, 2004 (ML042360586), to holders of operating licenses 
for PWRs. In GL 2004-02, the NRC staff requested that licensees 
perform an evaluation of their emergency core cooling systems (ECCS) 
and containment spray system (CSS) recirculation functions 
considering the potential for debris-laden coolant to be circulated 
by the ECCS and the CSS after a loss-of-coolant accident (LOCA) or 
high energy line break inside containment and, if appropriate, take 
additional actions to ensure system function. GL 2004-02 required 
that licensees provide a written response to the NRC, pursuant to 
Title 10 of the Code of Federal Regulations (10 CFR) Section 
50.54(f), describing the results of their evaluation and any 
modifications made, or planned, to ensure the ECCS and CSS remain 
functional.

II. Request/Action

    By application dated March 31, 2021, (Agencywide Documents 
Access and Management System (ADAMS) Accession No. ML21090A184), as 
supplemented by letters dated May 27, 2021, July 22, 2021, August 
23, 2021, October 7, 2021, January 27, 2022, March 8, 2022, May 26, 
2022, and September 8, 2022 (ML21147A222, ML21203A192, ML21237A135, 
ML21280A378, ML22027A804, ML22068A027, ML22146A337, and ML22251A343, 
respectively), the licensee, pursuant to 10 CFR 50.12, ``Specific 
exemptions,'' requested exemptions from certain requirements of 10 
CFR 50.46, ``Acceptance criteria for emergency core cooling systems 
for light-water nuclear power reactors,'' and 10 CFR part 50, 
Appendix A, General Design Criterion (GDC) 35, ``Emergency core 
cooling''; GDC 38, ``Containment heat removal''; and GDC 41, 
``Containment atmosphere cleanup,'' to allow use of a risk-informed 
methodology instead of the traditional deterministic methodology,

[[Page 65620]]

to resolve the concerns associated with GSI-191, and respond to GL 
2004-02 for Callaway.
    Specifically, the licensee requested exemptions from 10 CFR 
50.46(a)(1)(i), which, in part, requires the ECCS cooling 
performance to be calculated in accordance with an acceptable 
evaluation model as described in 10 CFR 50.46(a)(1), and for 
postulated LOCAs of different sizes, locations and other properties 
sufficient to provide assurance that the most severe LOCAs are 
evaluated. The NRC staff interprets the Section 50.46(a)(1) 
requirement to calculate ECCS performance for ``other properties'' 
as requiring licensees to consider the impacts of debris generation 
and transport in containment. The most significant form of debris in 
nuclear power reactor containments is piping and component 
insulation that can become debris during LOCAs, transport and 
accumulate in the sumps, and clog the sumps strainers, thus creating 
resistance to coolant flow. Fibrous debris from this insulation can 
also enter the reactor core and directly impede heat transfer from 
the fuel to the coolant.
    The approval of a risk-informed methodology would require 
exemptions from 10 CFR 50.46(a)(1)(i) and GDCs 35, 38, and 41 
because the NRC has interpreted these regulations as requiring a 
deterministic approach and bounding calculation to show compliance 
with ECCS and CSS performance criteria in 10 CFR 50.46(b) and GDCs 
35, 38, and 41. Issuance of exemptions is an appropriate means to 
grant relief from the use of a deterministic approach to show 
compliance with these requirements.
    The licensee's 10 CFR 50.46 deterministic analysis considered 
the debris in containment and demonstrated that the debris loading 
could prevent acceptable ECCS and CSS operation and core cooling for 
certain pipe ruptures. Based on its analysis, the licensee concluded 
that the amount of debris in the Callaway containment would need to 
be reduced to demonstrate compliance with 10 CFR 50.46 criteria 
using a deterministic analysis for certain large-break LOCA sizes 
because, for those breaks, the plant-specific testing threshold for 
generation and transport of debris was exceeded.
    Additionally, the licensee's deterministic in-vessel analysis 
was limited to breaks that could generate and transport to the 
strainers fibrous debris amounts in excess of the plant-specific 
tested debris limit for the strainers. This value was chosen because 
it also represents the deterministic limit for strainer failure for 
pipe breaks. Therefore, any break that generates and transports more 
than the amount of fibrous debris bounded by plant testing is 
already assumed to cause strainer failure and increase core damage 
frequency. Because these large breaks are already assumed to 
contribute to plant risk because of strainer failure, there is no 
need to evaluate them for risk contribution due to in-vessel 
failure. Other debris types were bounded by the strainer evaluation 
and are not critical to the in-vessel analysis. Therefore, all cases 
where core damage might occur due to debris arriving at the core are 
already covered by scenarios that cause strainer failure and do not 
need to be counted as additional increases in risk.
    The licensee requested exemptions from the requirement to use a 
deterministic analysis for specific scenarios of LOCA breaks 
producing and transporting debris in excess of the plant-specific 
tested debris limits. Since it determined that the probability of 
consequences from debris effects is very low, the licensee requested 
exemptions to allow the use of a risk-informed analysis to show 
adequate assurance of ECCS and CSS functionality, in accordance with 
the criteria in Regulatory Guide (RG) 1.174, Revision 3, ``An 
Approach for Using Probabilistic Risk Assessment in Risk-Informed 
Decisions on Plant-Specific Changes to the Licensing Basis,'' dated 
January 2018 (ML17317A256). RG 1.174 was developed in consideration 
of the Commission's Policy Statements on safety goals \1\ and the 
use of probabilistic risk assessment methods in nuclear regulatory 
activities.\2\ Therefore, RG 1.174 provides an acceptable method for 
licensees and NRC staff to use in assessing the impact of licensing 
basis changes when the licensee chooses to use risk information.
---------------------------------------------------------------------------

    \1\ Commission's Safety Goal Policy Statement, ``Safety Goals 
for the Operations of Nuclear Power Plants; Policy Statement,'' 
published in the Federal Register on August 4, 1986 (51 FR 28044), 
as corrected, and republished, on August 21, 1986 (51 FR 30028).
    \2\ Use of Probabilistic Risk Assessment Methods in Nuclear 
Activities; Final Policy Statement,'' August 16, 1995 (60 FR 42622).
---------------------------------------------------------------------------

    The requirements in GDC 35 require, in part, that the ECCS 
safety system functions adequately to transfer heat from the reactor 
core following a LOCA and in the presence of a worst single failure, 
at a rate such that (a) fuel and clad damage that could interfere 
with continued effective core cooling is prevented and (b) clad 
metal-water reactor is limited to negligible amounts. The licensee 
stated in its application dated March 31, 2021, that the function of 
the ECCS emergency sump is assumed to fail for scenarios where 
debris exceeds the amount determined in acceptable plant-specific 
testing. Failure of the sump and strainers results in loss of 
cooling to the core. The licensee requested exemptions from the 
requirements of GDC 35, which requires the use of a deterministic 
approach, for those LOCA breaks that exceed the plant-specific 
testing debris threshold. The licensee requested exemptions from the 
deterministic requirements of GDC 35, to allow the use of a risk-
informed analysis, in accordance with the criteria in RG 1.174, to 
show that the risk from debris effects is very low.
    The requirements in GDC 38 require containment heat removal, 
rapid reduction of containment pressure and temperature, and 
maintenance of pressure and temperature at an acceptably low level 
following a LOCA, and in the presence of a single failure, to 
preserve containment function. The licensee proposed that exemptions 
be granted from the requirements in GDC 38 that specify the use of a 
deterministic approach. The request applies only to those LOCA 
breaks that exceed the plant-specific testing debris threshold. 
Current Callaway design basis calculations are based on the 
containment cooling system (containment fan coolers) functioning in 
conjunction with the CSS and ECCS, both of which can be affected by 
debris. Using deterministic assumptions, the licensee's analysis and 
testing does not assure that the emergency sump strainers will be 
available to support the CSS and ECCS function considering the 
effects of debris produced by those breaks that can generate and 
transport debris amounts greater than the plant-specific testing 
threshold. The licensee requested exemptions from the deterministic 
requirements of GDC 38 to allow the use of a risk-informed analysis, 
in accordance with the criteria in RG 1.174, to show that the risk 
from debris effects is very low.
    The requirements in GDC 41, require, in part, containment 
atmosphere cleanup to control substances that may be released into 
the reactor containment, to reduce the concentration and quality of 
fission products released to the environment following postulated 
accidents, and to control the concentration of hydrogen or oxygen 
and other substances in the containment atmosphere following 
postulated accidents, assuming a single failure. The licensee stated 
that using deterministic assumptions, its analysis and testing 
cannot demonstrate that the emergency sump strainers will be 
available to support the CSS function considering the effects of 
debris produced and transported by breaks not bounded by acceptable 
plant-specific testing. The licensee requested exemptions from the 
deterministic requirements of GDC 41 to allow the use of a risk-
informed analysis, in accordance with the criteria in RG 1.174, to 
show that the risk from debris effects is very low.

III. Discussion

    Pursuant to 10 CFR 50.12, the Commission may, upon application 
by any interested person or upon its own initiative, grant 
exemptions from the requirements of 10 CFR part 50, when (1) the 
exemptions are authorized by law, will not present an undue risk to 
public health or safety, and are consistent with the common defense 
and security; and (2) when special circumstances are present. Under 
10 CFR 50.12(a)(2)(ii), special circumstances are present when 
``[a]pplication 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.''
    The licensee proposed to use a risk-informed methodology instead 
of a deterministic approach to account for the effects of debris in 
containment for portions of the LOCA analysis applicable to breaks 
that exceed the Callaway plant-specific debris testing threshold. 
The licensee's methodology, termed Risk over Deterministic, or 
RoverD, divides the loss of core cooling design-basis analysis into 
two portions: the ``deterministic analysis'' and the ``risk-informed 
analysis.'' The risk-informed analysis is used by the licensee for 
breaks that generate and transport debris exceeding the plant-
specific testing threshold. These breaks result in fibrous

[[Page 65621]]

debris estimated to arrive in the ECCS sump post-LOCA in amounts 
that are equal to or greater than the amount of fiber used in 
acceptable strainer testing. The acceptable limit was determined 
using testing methods intended to determine the maximum ECCS 
strainer head loss for the tested condition.
    Also, the licensee evaluated the in-core aspects of fibrous 
debris to prevent adequate fuel cooling. The licensee found that for 
in-vessel effects, all breaks that generate and transport fibrous 
debris amounts less than the strainer acceptance criterion can be 
evaluated deterministically and shown to have acceptable outcomes. 
Therefore, the in-vessel effects do not contribute to changes in 
core damage frequency. For ECCS and CSS analyses other than the 
postulated large-break LOCAs that generate less than the strainer 
acceptance limit, the licensee applied a deterministic methodology. 
If the exemptions were granted for these postulated breaks, the 
requirement to use a deterministic methodology for all other 
postulated LOCA breaks would continue to apply.

A. The Exemptions Are Authorized by Law

    The exemptions would allow the use of a risk-informed 
methodology to show compliance with 10 CFR 50.46(a)(1)(i), and GDCs 
35, 38, and 41 of Appendix A to 10 CFR part 50, when considering 
debris in containment generated and transported by those breaks that 
exceed the plant-specific testing threshold. These regulations were 
promulgated under and are consistent with the Commission's authority 
under Section 161 of the Atomic Energy Act of 1954, as amended. 
Because the application of a risk-informed methodology to show 
compliance with 10 CFR 50.46, and GDC 35, 38, and 41 of Appendix A 
to 10 CFR part 50, would not violate the Atomic Energy Act of 1954, 
as amended, or the Commission's regulations, the exemptions are 
authorized by law provided all requisite findings are made.

B. The Exemptions Present No Undue Risk to Public Health and Safety

    The provisions of 10 CFR 50.46 and GDCs 35, 38, and 41 of 
Appendix A to 10 CFR part 50 establish criteria for the emergency 
core cooling, containment cooling, and containment atmosphere 
cleanup system performance. As part of the amendment request, the 
licensee submitted exemption requests to change its design-basis 
analysis specified in the Updated Final Safety Analysis Report 
(UFSAR) to allow use of risk-informed and deterministic 
methodologies to specifically account for the impacts of debris in 
containment. The licensee justified its use of the risk-informed 
approach by stating that the proposed risk-informed approach meets 
the key principles in RG 1.174, Revision 3, in that it is consistent 
with defense-in-depth philosophy, maintains sufficient safety 
margins, results in a small increase in risk, and is monitored by 
the licensee using performance measurement strategies.
    Additionally, the licensee stated that the proposed exemptions, 
to allow use of the risk-informed method, are consistent with Key 
Principle 1 in RG 1.174 that requires a proposed change to the 
licensing basis (or amendment) to meet current regulations unless 
the change is explicitly related to requested exemptions. The 
probabilistic risk analysis results provided by the licensee and 
evaluated by the NRC staff in its safety evaluation, showed that the 
increase in risk associated with debris generation and transport on 
ECCS and CSS function following postulated LOCAs is very small, in 
accordance with the criteria in RG 1.174.
    The NRC staff concluded that the risk is consistent with the 
guidance in RG 1.174 and with the Commission policy statements on 
safety goals and the use of probabilistic risk assessment methods in 
nuclear regulatory activities; therefore, the requested exemptions 
present no undue risk to public health and safety.

C. The Exemptions Are Consistent With the Common Defense and 
Security

    The requested exemptions would allow the licensee to use a risk-
informed methodology to resolve a generic safety concern for PWRs 
associated with potential clogging of the ECCS and CSS strainers 
during certain design-basis events. The change is 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 exemptions, the 
exemptions are consistent with the common defense and security.

D. Special Circumstances

    Under the regulations in 10 CFR 50.12, the Commission may grant 
exemptions from the requirements of 10 CFR part 50 provided certain 
findings are made; namely, that special circumstances are present, 
the exemptions present no undue risk to public health and safety, 
the exemptions are consistent with the common defense and security, 
and the exemptions are authorized by law. The exemptions would allow 
the use of a risk-informed methodology to show compliance with 10 
CFR 50.46(a)(1)(i), and GDCs 35, 38, and 41 of Appendix A to 10 CFR 
part 50, specifically for the analyses of debris in containment 
impacting emergency cooling function during postulated large-break 
LOCAs that exceed the plant-specific testing threshold.
    The licensee requested exemptions citing the special 
circumstances criteria of 10 CFR 50.12(a)(2)(ii), because compliance 
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. The licensee cited these special circumstances 
for all of the requested exemptions.
    The licensee stated that an objective of each of the regulations 
for which exemptions are proposed is to maintain low risk to the 
public health and safety through the adequate functioning of the 
ECCS and CSS safety systems. These systems must be supported by 
adequate functioning of the containment sumps. The regulations in 10 
CFR 50.46(a)(1)(i) and GDCs 35, 38, and 41 of Appendix A to 10 CFR 
part 50 are met when the licensee can demonstrate, using a bounding 
calculation or other deterministic method that the ECCS and CSS are 
capable of functioning during design basis events. The licensee 
stated that its risk-informed analysis to show adequate functioning 
of ECCS and CSS, considering the impacts of debris during certain 
LOCA events, demonstrates that the ECCS and CSS systems will operate 
with a high degree of reliability. The licensee stated that special 
circumstances exist because the underlying intent of the 
regulations, to ensure adequate protection of public health and 
safety is met when applying a risk-informed approach to address GSI-
191 and responding to GL 2004-02. Further, it states that the risk-
informed approach is consistent with RG 1.174 and supports operation 
of those functions with a high degree of reliability. Thus, the 
licensee concludes that the underlying intent of each regulation is 
met, and the special circumstances described in 10 CFR 
50.12(a)(2)(ii) apply to each of the exemptions proposed by the 
licensee.
    The NRC staff evaluated the licensee's application, as 
supplemented and discussed the details of its evaluation of the 
risk-informed approach in an NRC safety evaluation available under 
ADAMS Accession No. ML22220A132. Although 10 CFR 50.46(a)(1) 
requires a deterministic approach, the GDCs do not specify that a 
risk-informed methodology may not be used to show compliance; 
however, because the NRC has interpreted each of these regulations 
as requiring a deterministic approach, exemptions are an appropriate 
means to grant the licensee relief to use an alternative approach. 
The underlying purpose of each regulation is to protect public 
health and safety in the event of a LOCA by establishing criteria 
for emergency core cooling, containment cooling and containment 
atmosphere cleanup system performance. In its safety evaluation, the 
NRC staff concluded, in part, that the licensee adequately 
demonstrated that the change in risk attributable to debris that 
exceed the plant specific threshold is very small and meets the risk 
acceptance guidelines in RG 1.174. The NRC staff also concluded that 
the analysis is consistent with defense-in-depth philosophy, 
maintains sufficient safety margins, results in a small increase in 
risk, and is monitored by the licensee using performance measurement 
strategies. Therefore, the licensee's use of the risk-informed 
analysis meets the underlying requirements of 10 CFR 50.46 and GDCs 
35, 38, and 41 of Appendix A to 10 CFR part 50, to ensure that a 
licensee demonstrates that the ECCS and CSS will provide adequate 
cooling for the reactor core and containment and provide containment 
atmosphere cleanup during design-basis accidents considering the 
impacts of debris, since it meets the guidelines in RG 1.174.
    Based on the above, the NRC staff concludes that special 
circumstances under 10 CFR 50.12(a)(2)(ii) exist because compliance 
with the deterministic requirements of 10 CFR 50.46(a)(1)(i), and 
GDCs 35, 38, and 41 of Appendix A to 10 CFR part 50 is not necessary 
to achieve the underlying purpose of each rule.

E. Supplemental Information

    For more technical details, refer to the SE associated with 
these exemptions under

[[Page 65622]]

ADAMS Accession No. ML22220A130 (enclosure 2).

F. Environmental Considerations

    Pursuant to 10 CFR 51.21, ``Criteria for and identification of 
licensing and regulatory actions requiring environmental 
assessments,'' the NRC has prepared an environmental assessment (EA) 
and finding of no significant impact (FONSI) summarizing the 
findings of its review of the environmental impacts of the proposed 
action under the National Environmental Policy Act (NEPA). The NRC 
staff determined that special circumstances under 10 CFR 51.21 exist 
to warrant preparation of an EA and FONSI because Callaway is 
proposing a risk-informed approach to resolve GSI-191 as recognized 
in Staff Requirement Memorandum SECY-12-0093, ``Closure Options for 
Generic Safety Issue--191, Assessment of Debris Accumulation on 
Pressurized-Water Reactor Sump Performance,'' dated December 14, 
2012 (ML12349A378). Because this action uses risk information to 
justify exemptions from deterministic regulations, the NRC staff 
considered preparations of an EA and FONSI to be a prudent course of 
action that would further the purposes of NEPA. Based on its review, 
the NRC concluded that an environmental impact statement is not 
required and that the proposed action will have no significant 
impact on the environment.
    The NRC published a final EA and FONSI on the proposed action in 
the Federal Register on August 29, 2022 (87 FR 52816).

IV. Conclusions

    Accordingly, the Commission has determined that, pursuant to 10 
CFR 50.12, exemptions are authorized by law, will not present an 
undue risk to the public health and safety, are consistent with the 
common defense and security, and special circumstances are present 
pursuant to 10 CFR 50.12(a)(2)(ii). Therefore, the NRC hereby grants 
Union Electric Company, dba Ameren Missouri, one-time exemptions 
from 10 CFR 50.46(a)(1), and 10 CFR part 50, Appendix A, GDCs 35, 
38, and 41 to allow the use of 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 
those breaks that exceed the plant-specific Callaway testing 
threshold.

    Dated at Rockville, Maryland, this 21st day of October 2022.

    For the Nuclear Regulatory Commission.

Gregory F. Suber,

Deputy Director, Division of Operating Reactor Licensing, Office of 
Nuclear Reactor Regulation.

[FR Doc. 2022-23569 Filed 10-28-22; 8:45 am]
BILLING CODE 7590-01-P
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