89 FR 218 pgs. 89052-89056 - Constellation Energy Generation LLC; Limerick Generating Station, Units 1 and 2; Exemption
Type: NOTICEVolume: 89Number: 218Pages: 89052 - 89056
Pages: 89052, 89053, 89054, 89055, 89056Docket number: [Docket No. 50-352; 50-353; NRC-2024-0194]
FR document: [FR Doc. 2024-26075 Filed 11-8-24; 8:45 am]
Agency: Nuclear Regulatory Commission
Official PDF Version: PDF Version
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NUCLEAR REGULATORY COMMISSION
[Docket No. 50-352; 50-353; NRC-2024-0194]
Constellation Energy Generation LLC; Limerick Generating Station, Units 1 and 2; Exemption
AGENCY:
Nuclear Regulatory Commission.
ACTION:
Notice; issuance.
SUMMARY:
The U.S. Nuclear Regulatory Commission (NRC) is issuing an exemption in response to letter dated February 17, 2023, as supplemented by letters dated July 21, 2023, July 31, 2023, August 16, 2023, and May 28, 2024. Constellation Energy Generation LLC (Constellation, the licensee) has requested exemption from specific requirements for reduction of risk from anticipated transients without scram (ATWS) events for light-water-cooled nuclear power plants. Constellation is the holder of the Renewed Facility Operating License Nos. NPF-39 and NPF-85, which authorize the operation of Limerick Generating Station, Units 1 and 2 (Limerick).
DATES:
This document was published in the Federal Register on November 12, 2024.
ADDRESSES:
Please refer to Docket ID NRC-2024-0194 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-2024-0194. 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, at 301-415-4737, or by email to PDR.Resource@nrc.gov. 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.
• NRC's PDR: The PDR, where you may examine and order copies of publicly available documents, is open by appointment. 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 a.m. and 4 p.m. eastern time (ET), Monday through Friday, except Federal holidays.
FOR FURTHER INFORMATION CONTACT:
Michael Marshall, Office of Nuclear Reactor Regulation, U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, telephone: 301-415-2871; email: Michael.Marshall@nrc.gov.
SUPPLEMENTARY INFORMATION:
I. Background
Constellation is the holder of the Renewed Facility Operating License Nos. NPF-39 and NPF-85, which authorize the operation of Limerick Generating Station, Units 1 and 2. The facilities consist of boiling water reactors (BWRs) located in Montgomery County, Pennsylvania and is located next to the Schuylkill River.
[top] By letter dated February 17, 2023, as supplemented by letters dated July 21, 2023, July 31, 2023, August 16, 2023, and May 28, 2024, Constellation has requested exemption from specific requirements of section 50.62 of title 10 of the Code of Federal Regulations (10 CFR), "Requirements for reduction of risk from anticipated transients without scram (ATWS) events for light-water-cooled nuclear power plants." A publicly available version of each letter is in ADAMS under Accession Nos. ML23052A023, ML23202A219, ML23212B105, ML23228A094, and ML24149A211, respectively. Constellation specifically requests an exemption from the requirements of 10 CFR 50.62(c)(3) and the automatic activation requirements of 10 CFR 50.62(c)(4) and (c)(5) for a period of 30 days before the calendar year 2027 refueling outage for Unit 2 and for a period of 30 days before the calendar year 2026 refueling outage for Unit 1. In conjunction with this exemption request the licensee submitted an associated license amendment request (ADAMS Accession No. ML23052A023) to add operational constraints to the limiting conditions of operations in the technical specifications (TSs) for each Limerick unit to be in effect during each respective exemption period to ensure that there is no increase in the potential
II. Request/Action
Pursuant to 10 CFR 50.62, the Commission's regulations establish specific ATWS mitigation requirements for nuclear power plants, with paragraphs (c)(3), (c)(4), and (c)(5) applicable to BWRs like Limerick Units 1 and 2. The systems that are required are to be operational are the alternate rod injection (ARI) system, the automatic activation of the standby liquid control system (SLCS), and equipment to trip the reactor coolant recirculation pumps automatically under conditions of an ATWS. Constellation requested an exemption from all requirements for ARI capability in 10 CFR 50.62(c)(3) and only from the automatic response capability in 10 CFR 50.62(c)(4) for SLCS and in 10 CFR 50.62(c)(5) recirculation pumps trip (RPT) for a period of 30-days prior to the calendar year 2027 refueling outage for Unit 2 and the calendar year 2026 refueling outage for Unit 1. During each 30-day period prior to the refueling outage, referred to by Constellation as the 30-day redundant reactivity control system (RRCS) demolition period, Constellation will begin upgrading the RRCS by demolishing the existing analog system and replacing it with a new digital system which will be completed during the refueling outage. To support RRCS demolition period, Constellation submitted a license amendment request to temporarily modify certain TS limiting conditions for operation to: (1) not require operability of certain automatic initiation features of ATWS equipment that are in the scope of work being performed, and (2) establish operating condition that ensure that there would be no increase in the consequences of an ATWS event should one occur during the 30-day RRCS demolition period. In addition, they also requested that certain surveillance requirements related to the ATWS features within the scope of work not be required during the RRCS demolition period. The limiting condition for operation changes temporarily limit the maximum reactor thermal power during the 30-day RRCS demolition period based on combination of operating parameters. Specifically, the maximum power at which the plant is limited based on the number of out of safety relief valves, the ability to manually initiate SLCS within five minutes, a minimum suppression pool water level, and the operability of the reactor water level 3 recirculation runback system. The operational constraints identified by Constellation for each identified maximum thermal power limit are listed in the following table.
| Maximum reactor thermal power | Maximum number of SRVs out of service | Manual initiation time for SLCS (minutes) | Minimum suppression pool water level (feet) | Additional system credited |
|---|---|---|---|---|
| 90% | 0 | 5 | 23 | Level 3 Recirculation Runback. |
| 87% | 0 | 5 | 22 | Level 3 Recirculation Runback. |
| 84% | 1 | 5 | 22 | Level 3 Recirculation Runback. |
In addition, as stated in their license amendment request, as evaluated by NRC staff in the safety evaluation (SE) to the license amendment request (LAR) to reduce the risk from a potential ATWS event during the 30-day period, the licensee will implement additional ATWS mitigation strategies to provide an equivalent level of ATWS protection to their normal automatic ATWS mitigation capability.
III. Discussion
Pursuant to 10 CFR 50.12, the Commission may, upon application by any interested person or upon its own initiative, grant exemption from the requirements of 10 CFR part 50 when: (1) the exemptions are authorized by law, (2) will not present an undue risk to public health or safety, (3) are consistent with the common defense and security; and (4) when special circumstances are present, as defined in 10 CFR 50.12(a)(2). This exemption would allow Constellation to temporarily disable the ARI, and the automatic activation of the SLCS and recirculation pumps at Limerick so that digital upgrades can be made leading up to the refueling outages of each unit.
A. The Exemption Is Authorized by Law
The Atomic Energy Act of 1954, as amended, does not require any specific systems to reduce the risk from ATWS events. These systems are required by NRC regulation. The intent of the regulations requires systems to mitigate the ATWS conditions, should they occur. The NRC staff has determined that granting the exemption will not result in a violation of the Atomic Energy Act of 1954, as amended, NRC regulations, or any other laws. Therefore, the requested exemption is authorized by law.
B. The Exemption Presents no Undue Risk to Public Health and Safety
The NRC requires that an exemption demonstrate that it does not present undue risk to public health and safety if it is granted. Constellation provided an analysis that with the proposed systems offline, the lower power limit, the manual activation of the SLCS and the recirculation runback pumps, that the disabling of the ATWS mitigation measures will not present undue risk to public health and safety. The disabling of automatic ATWS mitigation systems for 30-days potentially increases the severity of an ATWS event should it occur within the window. An ATWS that is not successfully mitigated could result in core damage due to excessive heat generation. ATWS events are unlikely events that are expected to occur once or more during an operating reactor's service life. The proposed changes to the reactor systems do not change the likelihood of an ATWS event occurring. The consequences of an ATWS can vary from a minor event that can be addressed with the available protection systems, to more severe that require more significant measures leading to a sudden shutting down of a nuclear reactor, if necessary to protect the core from damage.
[top] The proposed ATWS mitigation strategies and TS limits presented by the licensee in the analysis in its LAR in
C. The Exemption Is Consistent With the Common Defense and Security
The requested exemption does not change safeguards and security programs at Limerick. Constellation stated those programs will remain in full effect during the 30-day RRCS demolition period exemption time periods in calendar year 2027 for Unit 2 and in calendar year 2026 for Unit 1. Therefore, the NRC staff finds that the action is consistent with the common defense and security.
D. Special Circumstances
Pursuant to 10 CFR 50.12(a)(2)(ii), special circumstances are present when application of the regulation in the particular circumstances is not necessary to achieve the underlying purpose of the rule. The underlying purpose of 10 CFR 50.62 is that there are systems available to operators to sufficiently mitigate the consequences of an ATWS event, that are reliable, independent and diverse from the reactor trip system. This is made clear in 49 FR 26040 as it states "The equipment required by this amendment (10 CFR 50.62(c)) is for the purpose of reducing the probability of unacceptable consequences following anticipated operational occurrences." The systems that are required by 10 CFR 50.62 at BWRs are an alternative rod insertion system, automatic SLCS, and automatic reactor coolant recirculation pump trip system.
In 49 FR 26041, the Commission provided that some operating nuclear power plants licensed to operate prior to August 22, 1969, may be granted a permanent exemption from these requirements if they can demonstrate that their risk from an ATWS is sufficiently low. The Commission provided guidance for the factors that it determined to be important to this such as, power level, unique design features that could prevent or mitigate the consequences of an ATWS, or the remaining plant lifetime. The Commission has granted these exemptions for plants licensed to operate prior to 1969 based on the finding that the risk from an ATWS is sufficiently low and therefore was not necessary to achieve the underlying purpose of the rule for Haddam Neck (55 FR 10124) and Yankee Nuclear Power Station (53 FR 20704). While Limerick Units 1 and 2 were licensed to operate after August 22, 1969, they are seeking a temporary, not a permanent exemption from these requirements. The NRC staff notes that this 30-day RRCS demolition period is temporary in nature, one time per unit, and that the resulting RRCS modifications to upgraded, digital systems will restore permanent, full compliance with 10 CFR 50.62(c)(3)-(5) afterwards. This temporary nature of the exemption aligns with the factor the Commission considered to be important to grant a permanent exemption of "the remaining plant lifetime." In addition, the licensee has proposed in the associated LAR to impose operational controls including restrictions on the power level of the plant during the 30-day RRCS demolition period, which in part is used by the licensee in its analysis to demonstrate that there is no net increase in the severity of an ATWS. This aligns with the factor of "power level" identified by the Commission as an important factor in granting such an exemption from the ATWS rules because the power level of Limerick Units 1 and 2 will be limited by the plant's TS during their respective 30-day RRCS demolition period. Finally, while the licensee has not identified any unique design features at Limerick Units 1 and 2, it has proposed unique limiting conditions of operations such as reactor power less than or equal to 90% RTP, all 14 SRVs operable, and suppression pool water level greater than or equal to 23 feet. If suppression pool water level is less than 23 feet, but greater than 22 feet, reactor power must be reduced to less than 87%. If one SRV becomes out of service reactor power must be further reduced to less than or equal to 84% RTP. If two SRVs become inoperable or suppression pool water level drops below 22 feet then LCO 3.3.4.1 would apply, and the licensee would have one hour to restore at least one ATWS Recirculation Pump trip system to operable status within one hour or place the plant in Startup Mode within the next six hours as required by Limerick TS Action 3.3.4.1.e. The licensee has demonstrated in its analysis that by implementing these limiting conditions for operations, results in no net increase in the severity of an ATWS event. Finally, while the rule requires automatic systems, the licensee has demonstrated that the relevant human factors can sufficiently mitigate an ATWS event in the analysis, as documented by NRC staff in the SE to the associated LAR. The NRC staff finds that the relevant human factors are appropriate for a temporary exemption from the requirement for automatic systems because the licensee has demonstrated that the temporary limiting conditions for operation provide sufficient time margin in the event of an ATWS for manual actuation of these systems to provide the same level of ATWS mitigation as the automatic systems required by 10 CFR 50.62(c)(3)-(5), as evaluated by NRC staff in the SE to the LAR associated with this exemption. Therefore, the NRC staff finds that the risk of an ATWS is sufficiently low in support of this temporary exemption request, using the factors the Commission identified for certain nuclear power plants, not including Limerick Units 1 and 2, to be granted permanent exemptions from the ATWS requirements in 10 CFR 50.62(c).
[top] Specific to the application of the rule to Limerick, NRC staff notes that the Limerick updated final safety analysis report (UFSAR) and Tech Spec Bases provides specific descriptions of each system. As described in the UFSAR Section 4.6.1.2.5.4 for Limerick, the purpose of the alternative rod insertion system as required by 10 CFR 50.62(c)(3) is to provide independent solenoid valves to bleed air from the scram valve pilot air header on low water level or high dome pressure in the reactor pressure vessel when detected by the RRCS to increase the reliability of control rod insertion. As described in the UFSAR Section 9.3.5 and TS 3/4.1.5 and associated TS basis for Limerick, the purpose of the automatic SLCS as required by 10 CFR 50.62(c)(4) is to provide a backup capability for bringing the reactor from full power to a cold, Xenon-free shutdown, assuming that the withdrawn control rods remain fixed in the rated power pattern. As described in
The NRC staff notes that for 10 CFR 50.62(c)(3), the specific application of the rule over these temporary 30-day exemption periods is not necessary to achieve the purpose as stated in Limerick's UFSAR section 4.6.1.2.5.4 here because the compensatory actions to manually start the SLCS will provide the required negative reactivity to mitigate the ATWS. For 10 CFR 50.62(c)(4)-(5), the NRC staff notes that the licensee has demonstrated that the reactor operator's manual actuation of these systems will be able to provide the same level of ATWS mitigation as the automatic systems during the 30-day RRCS demolition period with the associated limiting conditions for operation, as evaluated by NRC staff in Section 3.4 "Walkthroughs" in its SE to the LAR associated with this exemption. Therefore, the specific application for automatic actuation of the systems required by the rule over these temporary 30-day exemption periods is not necessary to achieve the purposes as stated in Limerick's UFSAR sections 9.3.5, and TS 3/4.1.5 for 10 CFR 50.62(c)(4) and as stated in Limerick's UFSAR Section 7.1, 7.6, and TS 3/4.3.4 for 10 CFR 50.62(c)(5).
Application of 10 CFR 50.62(c)(3)-(5) during 30-day RRCS demolition period is not necessary to achieve the underlying purpose of the rule as Constellation stated that since the provided analysis shows that when the operational constraints of the lower power limit, a higher number of operable safety relief valves, an additional non-credited automatic action (recirculation pump runback), and manual activation of the SLCS system within a 5-minute time frame, an ATWS condition can be successfully mitigated using existing procedures. The NRC staff's independent review of the analysis provided that the comparable level of ATWS mitigation protection to the required systems in 10 CFR 50.62(c)(3)-(5) can be achieved with these proposed operational constraints and that the mitigation measures provide sufficient time margin for an operator to respond to an ATWS event in place of the required automatic systems for the limited period of the 30-day RRCS demolition period. Therefore, the underlying purpose of 10 CFR 50.62(c)(3)-(5), including the specific underlying purposes of each system as described in the Limerick UFSAR and Tech Spec Bases, are achieved by the licensee's implementation of additional ATWS mitigation strategies identified in the LAR associated with this exemption and compliance with the TS limiting conditions of operations proposed in LAR while the licensee turns off the ACI, automatic SLCS, and automatic RTP during the 30-day RRCS demolition period. Accordingly, compliance with the specific requirements of 10 CFR 50.62 is not necessary during the proposed 30-day RRCS demolition period to achieve the underlying purpose of the rule. The NRC staff finds that special circumstances are present pursuant to 10 CFR 50.12(a)(2)(ii).
Constellation also proposed that 10 CFR 50.12(a)(2)(iv) and 10 CFR 50.12(a)(2)(vi) as additional special circumstances that are applicable to the exemption request. The NRC staff has considered their applicability but found that the circumstances discussed above in 10 CFR 50.12(a)(2)(ii) were adequate to address the necessity of special circumstances for the exemption request.
E. Environmental Considerations
The NRC's approval of the exemption to 10 CFR 50.62(c)(3), (c)(4), and (c)(5) belongs to a category of actions that the NRC, by rule or regulation, has declared to be a categorical exclusion, after first finding that the category of actions does not individually or cumulatively have a significant effect on the human environment. Specifically, the exemption is categorically excluded from further environmental analysis under 10 CFR 51.22(c)(9).
Under 10 CFR 51.22(c)(9), the issuance of an amendment to a license for a reactor under part 50 or part 52 that changes a requirement or issuance of an exemption from the requirement of any regulation of 10 CFR is a categorical exclusion provided that:
• The proposed action involves the exemption from a requirement for the use of a facility component located within the restricted area, as defined in 10 CFR part 20;
• The exemption involves no significant hazards consideration. The basis for the NRC staff's determination is discussed in the no significant hazards consideration published in the Federal Register on October 27, 2023 (88 FR 73883);
• There is no significant change in the types or significant increase in the amounts of any effluents that may be released offsite. There are no additional quantities nor changes in effluents proposed to be released based on the proposed action;
• There is no significant increase in individual or cumulative public or occupational radiation exposure. All manual actions are proposed to be conducted from the main control room and no local actions are required based on information provided by Constellation in its letter dated August 16, 2023 (ADAMS Accession No. ML23228A094). The main control room is shielded and staffed 24 hours a day under normal circumstances;
Therefore, NRC staff has determined that these exemptions are categorically excluded from environmental review pursuant to 10 CFR 51.22(c)(9), and therefore no environmental assessment or environmental impact statement needs to be prepared in connection with the proposed exemption request.
IV. Conclusions
Accordingly, the NRC has determined that, pursuant to 10 CFR 50.12, the exemption is authorized by law, will not present an undue risk to public health and safety, and is consistent with the common defense and security. Special circumstances are also present at Limerick to justify the exemption. Therefore, the NRC hereby grants Constellation exemptions from all requirements for ARI capability under section 10 CFR 50.62(c)(3) and only from the automatic response capability of 10 CFR 50.62(c)(4) for SLCS and 10 CFR 50.62(c)(5) for RPT for a period of 30-days prior to the 2027 refueling outage for Unit 2 and the 2026 refueling outage for Unit 1 (also referred to by Constellation as the 30-day RRCS demolition period) while operating each respective Unit in accordance with the TS limiting conditions for operation and the additional ATWS mitigation strategies requested in the associated LAR to this exemption request dated February 17, 2023, as supplemented by letters dated July 21, 2023, July 31, 2023, August 16, 2023, and May 28, 2024. The exemption is authorized by law, will not present an undue risk to the public health and safety, and is consistent with the common defense and security. Also, special circumstances are present. Therefore, the Commission hereby grants Constellation a one-time exemption from 10 CFR part 50, section 50.62(c)(3) and only the automatic response capability of sections 50.62(c)(4) and 50.62(c)(5) during the 30-day RRCS demolition period to support the installation of the digital upgrade at Limerick.
Dated: November 5, 2024.
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For the Nuclear Regulatory Commission.
Bo Pham,
Director, Division of Operating Reactor Licensing, Office of Nuclear Reactor Regulation.
[FR Doc. 2024-26075 Filed 11-8-24; 8:45 am]
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