ML25218A252
| ML25218A252 | |
| Person / Time | |
|---|---|
| Site: | Clinton  |
| Issue date: | 08/06/2025 |
| From: | Wetzel B Plant Licensing Branch III |
| To: | Lien N Constellation Energy Generation |
| Wetzel, B | |
| References | |
| EPID L-2025-LLA-0099 | |
| Download: ML25218A252 (4) | |
Text
From:
Beth Wetzel To:
Lien, Nicholas: (Constellation Nuclear)
Cc:
ext_Chelsie_Miller; Derek.Hillinger@constellation.com
Subject:
Final RAI - Clinton Power Station, Unit 1 - A Proposed Change to the USAR to Approve Alternate Method of Verifying MSIV Closure RPS Response Time (EPID No. L-2025-LLA-0099)
Date:
Wednesday, August 6, 2025 10:14:00 AM
Dear Nicholas Lien,
By letter dated June 26, 2025 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML25177C292), Constellation Energy Generation, LLC (CEG, the licensee) requested a license amendment for a proposed change to the Updated Safety Analysis Report (USAR) to approve alternate method of verifying MSIV closure reactor protection system response time for Clinton Power Station (CPS), Unit 1. Specifically, the amendment request was submitted in response to a Green Finding with an associated Non-Cited Violation from the CPS Comprehensive Engineering Team Inspection that was issued by the NRC on May 8, 2025. This violation was cited against 10 CFR 50, Appendix B, Criterion V, Instructions, Procedures and Drawings, for a failure to have procedures appropriate to the circumstances for performing response time testing of the reactor protection system main steam isolation valve closure function, an activity affecting quality. The violation stated that this failure has led to CPS not meeting Technical Specification (TS) Surveillance Requirement (SR) 3.3.1.1.17, which requires the measurement of the RPS Response Time for Function 6 (Main Steam Isolation Valve -
Closure). The intent of CEGs request is to restore CPS to compliance by receiving NRC approval of the methodology used for verifying MSIV closure reactor protection system response time for CPS.
The NRC staff has reviewed the submittal and determined that additional information is needed to complete its review. The specific question is found in the enclosed request for additional information (RAI). On August 5, 2025, the CEG staff indicated that a response to the RAI would be provided by August 13, 2025.
If you have any questions, please contact me at 301-415-5223 or via e-mail at Beth.Wetzel@nrc.gov.
Beth Wetzel Project Manager Plant Licensing Branch III Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation
U.S. Nuclear Regulatory Commission O-8H10 301-415-5223
Docket No.: 50-461
Enclosure:
Request for Additional Information
cc: Listserv
REQUEST FOR ADDITIONAL INFORMATION
LICENSE AMENDMENT TO UPDATE THE SAR TO APPROVE ALTERNATE METHOD
OF VERIFYING MSIV CLOSURE REACTOR PROTECTION SYSTEM RESPONSE TIME
CONSTELLATION ENERGY GENERATION, LLC
CLINTON POWER STATION, UNIT 1
DOCKETNO.50461
By application dated June 26, 2025 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML25202A156), Constellation Energy Generation, LLC (CEG; the licensee) submitted a license amendment request (LAR) for Clinton Power Station, Unit 1. The proposed amendment would revise the Updated Safety Analysis Report (USAR) to include an alternate method of verifying Reactor Protection System Response Time (RPSRT) for Main Steam Isolation Valve (MSIV) Closure as an NRC-approved methodology. The U.S. Nuclear Regulatory Commission (NRC) staff determined that the following information is needed to complete its review.
RAI-1
Regulatory Basis
AppendixA to Title 10 of the Code of Federal Regulations, Part 50 (10 CFR 50),
General Design Criterion (GDC) 13, Instrumentation and Control, requires that instrumentation shall be provided to monitor variables and systems over their anticipated ranges for normal operation, for anticipated operational occurrences, and for accident conditions as appropriate to assure adequate safety, including those variables and systems that can affect the fission process, the integrity of the reactor core, the reactor coolant pressure boundary, and the containment and its associated systems. Appropriate controls shall be provided to maintain these variables and systems within prescribed operating ranges.
10 CFR 50.36, Technical Specifications paragraph (c)(3), states that surveillance requirements are requirements relating to test, calibration, or inspection to assure that the necessary quality of systems and components is maintained, that facility operation will be within safety limits, and that the limiting conditions for operation will be met.
Issue
In the LAR (Attachment 1,page 4 of 8) the licensee states that the RPS MSIV Closure Trip calibration surveillance requirement SR 3.3.1.1.13 test can reveal possible deterioration of the snap-acting limit switch, such as sluggish behavior (e.g., slow movement or sticking), which could preclude an RPS trip within the TS 3.3.1.1-1 required allowable limits.
The LAR included a commitment to revise CPS procedures 9431.10 (A through H),
but did not include its specific procedure steps.
Request
To reach a reasonable assurance determination that the proposed Clinton RPS MSIV Closure Trip Response Time methodology will be effective, the staff needs to review the proposed instructions within at least one of the licensees revised CPS procedures 94310.10 (A through H) for the RPS Main Steam Line Isolation Valve channel calibrations.
Please provide at least one of the proposed revised calibration surveillance procedures (assuming the instructions are identical for all RPS MSIV Inboard and Outboard Limit Switches) showing that:
- 1. Adequate instructions have been included for CPS maintenance and engineering personnel to reasonably observe, identify, and document/record any observations regarding the onset or degree of any observed snap-acting limit switch sluggish behavior which could have the potential to preclude an RPS trip within the TS 3.3.1.1-1 allowable limits (both setpoint and response time), such that any potential degradation of the switch performance during calibration and from one calibration to the next calibration can be readily identified. If there are any metrics or procedural steps that can be used to
repeatably record such degradation, such metrics or steps are also identified within the procedure.
- 2. Adequate instructions are included to record the trend of as-found data for the MSIV valve stem closure percentage travel over the course of time, to enable maintenance and engineering personnel to have a basis for evaluating whether the limit switch performance is degrading over time.