ML24222A395
| ML24222A395 | |
| Person / Time | |
|---|---|
| Site: | Clinton  |
| Issue date: | 08/23/2024 |
| From: | Joel Wiebe Plant Licensing Branch III |
| To: | Rhoades D Constellation Energy Generation |
| Wiebe J | |
| References | |
| EPID L-2023-LLA-0118 | |
| Download: ML24222A395 (8) | |
Text
August 23, 2024 David P. Rhoades Senior Vice President Constellation Energy Generation, LLC President and Chief Nuclear Officer Constellation Nuclear 4300 Winfield Road Warrenville, IL 60555
SUBJECT:
CLINTON POWER STATION, UNIT 1 - REGULATORY AUDIT REPORT TO SUPPORT THE REVIEW OF THE AMENDMENTS TO REVISE REACTOR WATER CLEANUP VALVE ISOLATION TIMING (EPID L-2023-LLA-0118)
Dear David P. Rhoades:
By letter to the U.S. Nuclear Regulatory Commission (NRC, the Commission) dated August 21, 2023 (Agencywide Documents Access and Management System (ADAMS)
Accession No. ML23233A168), Constellation Energy Generation, LLC (the licensee) submitted a license amendment request (LAR) for Clinton Power Station (Clinton), Unit No. 1, to revise the reactor water cleanup system isolation functions that are listed in Technical Specification 3.3.6.1, "Primary Containment and Drywell Isolation Instrumentation," Table 3.3.6.1-1, "Primary Containment and Drywell Isolation Instrumentation." Specifically, the change increases the allowable value for Function 4.b, "Differential Flow - Timer," and renames Function 4.b as "Differential Flow Timer - High." In addition, new functions are added for a differential flow -
high-high trip and an associated differential flow high - high timer. In order to gain an understanding of the changes, the NRC staff conducted an audit under the Office of Nuclear Reactor Regulation guidance LIC-111, Regulatory Audits. The audit plan was provided on January 24, 2024 (ML23361A157). Following the audit and in response to a request for additional information, the licensee supplemented the LAR on May 9, 2024 (ML24130A221).
The amendment was issued on July 11, 2024 (ML24157A324).
The audit was conducted from January 24, 2024, through April 26, 2024, virtually using an online portal and online discussions. The purpose of the audit was to gain understanding, to verify information, and to identify information that will require docketing to support the proposed licensing actions. The enclosure to this letter provides a report of the NRC staffs audit.
D. Rhoades If you have any questions, please contact me by telephone at (301) 415-6606 or by email at Joel.Wiebe@nrc.gov.
Sincerely,
/RA/
Joel S. Wiebe, Senior Project Manager Plant Licensing Branch III Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-461
Enclosure:
Audit Report cc: Listserv
Enclosure REGULATORY AUDIT REPORT TO SUPPORT REVIEW OF LICENSE AMENDMENT REQUEST TO REVISE REACTOR WATER CLEANUP ISOLATION VALVE TIMING CLINTON POWER STATION, UNIT 1 DOCKET NO. 50-461
1.0 BACKGROUND
By letter to the U.S. Nuclear Regulatory Commission (NRC) dated August 21, 2023 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML23233A168), Constellation Energy Generation, LLC (the licensee) submitted a license amendment request (LAR) for Clinton Power Station (Clinton), Unit No. 1, to revise the reactor water cleanup (RWCU) system isolation functions that are listed in Technical Specification (TS) 3.3.6.1, "Primary Containment and Drywell Isolation Instrumentation,"
Table 3.3.6.1-1, "Primary Containment and Drywell Isolation Instrumentation."
Specifically, the change increases the allowable value for Function 4.b, "Differential Flow
- Timer," and renames Function 4.b as "Differential Flow Timer - High." In addition, new functions are added for a differential flow - high-high trip and an associated differential flow high - high timer. In response to a request for additional information (RAI), the licensee supplemented the LAR on May 9, 2024 (ML24130A221).
The NRC staff determined it would be efficient to conduct an audit in order to enable the staff to examine and evaluate information with the intent to gain understanding, verify information, and/or identify information that will require docketing to support the basis of a licensing or regulatory decision. The NRC staff performed an audit from January 24, 2024, through April 26, 2024. The audit was conducted via electronic portal that was established by Constellation.
The NRC staff performed and completed its audit in accordance with NRR Office Instruction LIC-111, Revision 1, Regulatory Audits (ML19226A274).
2.0 AUDIT TEAM The following NRC staff members participated in the audit:
Joel Wiebe, Project Manager, NRR, Division of Operating Reactor Licensing (DORL) - Joel.Wiebe@nrc.gov John Parillo, Technical Reviewer, NRR Division of Risk Assessment, Radiation Protection and Consequence Branch (ARCB) - John.Parillo@nrc.gov Ming Li, Technical Reviewer, NRR Division of Engineering and External Hazards, Instrumentation and Controls Engineering Branch (EICB) - Ming.Li@nrc.gov Jeff Correll, Technical Reviewer, NRR Division of Reactor Oversight, Operator Licensing and Human Factors Branch (IOLB) - Jeff.Correll@nrc.gov Fred Forsaty, Technical Reviewer, NRR Division of Safety Systems, Nuclear System Performance Branch (SNSB) - Fred.Forsaty@nrc.gov David Nold, Technical Reviewer, NRR Division of Safety Systems, Containment and Plant Systems Branch (SCPB) - David.Nold@nrc.gov Thang Thawn, NRR Division of Safety Systems, Containment and Plant Systems Branch (SCPB) - Thang.Thawn@nrc.gov 3.0 AUDIT
SUMMARY
The audit discussions included the following audit topics. Based on its review of the LAR and the results of the audit the NRC staff issued an RAI to Constellation by electronic mail dated May 3, 2024 (ML24222A409). Constellation provided a response to the RAI by letter dated May 9, 2024 (ML24130A221).
3.1 High Energy Line Break (HELB) Analysis Summary of Information in LAR Section 3.4.1 Inside Containment sub-compartment response was analyzed for the Main Steam Tunnel (MST), RWCU Heat Exchanger and Heat Exchanger Valve Rooms, RWCU Crossover Pipe Tunnel, Filter Demineralizer Holding Pump Room, Filter Demineralizer Valve Room, and Filter Demineralizer Rooms.
The results show peak temperatures, pressures, and differential pressures for each zone are bounded by the large break result in the base calculation. Also, the structure was evaluated to ensure allowable stresses were not exceeded.
The following zones were determined to be not affected by the proposed LAR changes:
C.4.4 Pipe Tunnel 791',
C.4.5 Backwash Tank Cubicle, and C.4.7 Recirculating Pump Cubicle.
Zone C.5.8 Pipe Tunnel 803'-3" has no RWCU high energy piping. However, this zone can experience environmental transients due to steam introduced from adjacent zones.
The temperature profile in this zone changed in that the maximum temperature of 223°F (degree Fahrenheit) is held for a longer duration (i.e., 1000 seconds vs 120 seconds) to account for the longer break duration.
Audit Activities. The table below lists documents that were made available to the NRC staff via the Constellation electronic portal entitled NRC Audit - Clinton LAR to Revise RWCU Isolation Instrumentation. The staffs summary of their review of this information directly follows the table.
Document Title Revision / Date 3C10-0377-001 3C10-1182-003 Audit Summary ATD-0278 Design Change Package EC Number 636711 Containment Subcompartment Analyses - RWCU Line Break RWCU Line Break Inside Main Steam Tunnel in Containment Responses to Questions from Audit Call on March 20, 2020 sic* - Question #1 *this call actually occurred on March 20, 2024 Secondary Containment Response Due to RT Pump Room Line Break RWCU Differential Flow Modification Revision 4 / June 21, 2023 Revision 3 / May 5, 2023 Revision 0/ March 20, 2024 Revision 0 / January 17, 1994 Revision 000 / June 27, 2023 During the audit, the NRC staff focused on the regulatory requirements of Title 10 of the Code of Federal Regulations (10 CFR) part 50, appendix A, Criterion 4Environmental and dynamic effects design bases and the guidance of NUREG-0800, section 5.4.8, Reactor Water Cleanup System (Boiling-Water Reactor (BWR)), Revision 3.
To better understand the supporting documents that support the LARs conclusions, the NRC staff reviewed the assumptions and the methodologies contained within both calculations 3C10-0377-001 and 3C10-1182-003. The staff also checked for congruence between the conclusions presented in LAR, section 3.4.1, and the information contained in these two calculations.
During the Breakout session audit discussion with the licensee on March 20, 2024, the NRC staff confirmed that due to the mass and energy release within the RWCU pump rooms, RWCU isolation from the Containment would occur in a significantly shorter time than the differential flow setpoints of 45 seconds. These RWCU pump rooms are located on the second tier from lowest elevation within the Auxiliary Building. Since this isolation time is much faster than the differential flow delay of 45 seconds, the HELB analysis for these rooms is unaffected by the proposed change contained in the LAR.
3.2 Internal Flooding Analysis Summary of Information in LAR Section 3.4.2 The licensee revised the calculation that documents the internal flooding analysis to determine maximum flood levels in sub-compartments both inside and outside containment. The licensee stated that only the RWCU line breaks inside containment credit differential flow as the means for detection and isolation of breaks. The calculation addresses releases corresponding to double ended guillotine breaks (i.e., isolated by the short timer) and the maximum release that will be isolated by the long timer. The calculation evaluates both steady state flood levels due to flow in and out of a cubicle, and flood levels due to total released inventory. The revised calculation resulted in increased flood levels in eight containment Environmental Zones: C4.5; C5.3; C5.4; C5.6; C5.7; C5.9; C5.12; and C5.13. Results of the revised calculation indicated that flood level increases will not impact any safe-shutdown equipment.
The increased flood levels were also evaluated for impacts to the RWCU cubicles structure. The evaluation determined that the structures remain qualified for design basis loads.
Audit Activities. The table below lists documents that were made available to the NRC staff via the Constellation electronic portal entitled NRC Audit - Clinton LAR to Revise RWCU Isolation Instrumentation. The staff documented its review of this information in Safety Evaluation dated July 11, 2024 (ML24157A324).
Document Title Revision / Date 3C10-0485-0001 Audit Summary Internal Flood Analysis Responses to Questions from Audit Call on March 20, 2020 sic* - Question #2
- This call actually occurred on March 20, 2024 Revision 11 / June 19, 2023 Revision 0/ March 20, 2024 During the audit, the NRC staff focused on: (a) the regulatory requirements of 10 CFR part 50, appendix A, Criterion 4Environmental and dynamic effects design bases; (b) the guidance of NUREG-0800, section 5.4.8, Reactor Water Cleanup System (BWR),
Revision 3; (c) NUREG-0800, section 3.4.1, Internal Flood Protection for Onsite Equipment Failures. Revision 3, and (d) NUREG-0800, section 3.6.1, Plant Design For Protection Against Postulated Piping Failures In Fluid Systems Outside Containment, Revision 3.
To better understand the supporting document that supports the LARs conclusions, the NRC staff reviewed the assumptions and the methodologies contained within calculation 3C10-0485-0001. The staff also verified the congruence between the conclusions presented in LAR, section 3.4.2, and the information contained in this calculation.
During the Breakout session audit discussion with the licensee on March 20, 2024, the NRC staff furthered their understanding of the Auxiliar Building layout. The RWCU pump rooms are located on the second tier from the lowest elevation within the Auxiliary Building. As stated before, due to the mass and energy release within the RWCU pump rooms that RWCU isolation from the Containment would occur in a significantly shorter period than the differential flow setpoints of 45 seconds. The licensee stated that the RWCU pump rooms do not have watertight doors and a line break within this area could flood into the Auxiliary Building hallway. However, the floor plugs in the hallway above the emergency core cooling system (ECCS) cubicles have seals to prevent a flood from leaking into the ECCS cubicles.
4.0 AUDIT CONCLUSION The purpose of the audit was to gain understanding, to verify information, and to identify information that will require docketing to support the proposed licensing action. As a result of the audit and the NRC staffs review of the LAR, the staff issued the RAI dated May 3, 2024, the licensee responded on May 9, 2024, and the amendment was issued on July 11, 2024.
Date: August 23, 2024
ML24222A395 NRR-106 OFFICE NRR/DORL/LPL3/PM NRR/DORL/LPL3/LA NRR/DSS/SCPB/BC NAME JWiebe SRohrer MValentin DATE 08/09/2024 08/13/2024 05/31/2024 OFFICE NRR/DORL/LPL3/BC NRR/DORL/LPL3/PM NAME JWhited JWiebe DATE 08/20/2024 08/23/2024