NMP2L2905, Response to Request for Additional Information for License Amendment Request to Revise Surveillance Requirement (SR) 3.6.1.3.12 to a Reduced Test Pressure and Corresponding Leakage Rate for Main Steam Isolation Valves
| ML25155B825 | |
| Person / Time | |
|---|---|
| Site: | Nine Mile Point  (NPF-069) |
| Issue date: | 06/09/2025 |
| From: | Knowles J Constellation Energy Generation |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| NMP2L2905 | |
| Download: ML25155B825 (1) | |
Text
200 Energy Way Kennett Square, PA 19348 www.constellation.com 10 CFR 50.90 NMP2L2905 June 9, 2025 United States Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Nine Mile Point Nuclear Station, Unit 2 Renewed Facility Operating License No. NPF-69 NRC Docket No. 50-410
Subject:
Response to Request for Additional Information for License Amendment Request to Revise Surveillance Requirement (SR) 3.6.1.3.12 to a Reduced Test Pressure and Corresponding Leakage Rate for Main Steam Isolation Valves
References:
1.
Letter from J. Knowles (Constellation Energy Generation, LLC) to U.S.
Nuclear Regulatory Commission, "Exemption Request from Certain Requirements of 10 CFR 50, Appendix J, for Nine Mile Point Nuclear Station, Unit 2," "License Amendment Request to Revise Surveillance Requirement (SR) 3.6.1.3.12 to a Reduced Test Pressure and Corresponding Leakage Rate for Main Steam Isolation Valves,"
NMP2L2894, ML25029A181, dated January 29, 2025 2.
Email Letter from R. Guzman, Project Manager, U.S. Nuclear Regulatory Commission, "Nine Mile Point Nuclear Station, Unit No. 2 - Request for Additional Information Re: LAR to Revise SR to Reduced Test Pressure and Leakage Rate for MSIVs (EPID L-2025-LLA-0019)," ML25134A031, dated May 14, 2025 By letter dated January 29, 2025 (Reference 1), Constellation Energy Generation, LLC (CEG) requested a change to the Nine Mile Point Nuclear Station Unit 2 (NMP2) Technical Specifications (TS) Request to Revise Surveillance Requirement (SR) 3.6.1.3.12 to a Reduced Test Pressure and Corresponding Leakage Rate for Main Steam Isolation Valves.
On May 5, 2025, the NRC Project Manager for NMP2 emailed draft Request for Additional Information (RAI) question necessary to complete their review. On May 13, 2025, CEG informed the NRC Project Manager that a clarification call was not necessary. On May 14, 2025, the NRC Project Manager issued the formal RAI question to CEG (Reference 2). to this letter contains the NRCs RAI question immediately followed by CEGs response.
Response to Request for Additional Information NMP2 MSIV Test Pressure Reduction Docket No. 50-410 June 9, 2025 Page 2 CEG has reviewed the information supporting the No Significant Hazards Consideration and the Environmental Consideration that was previously provided to the NRC in Reference 1.
The additional information provided in this submittal does not affect the conclusion that the proposed license amendment does not involve a significant hazards consideration. This additional information also does not affect the conclusion that neither an environmental impact statement nor an environmental assessment need be prepared in support of the proposed amendment.
This letter contains no new regulatory commitments.
Should you have any questions concerning this submittal, please contact Ron Reynolds at 267-533-5698.
I declare under penalty of perjury that the foregoing is true and correct. Executed on the 9th day of June 2025.
Respectfully, Justin W. Knowles Senior Manager - Licensing Constellation Energy Generation, LLC
Attachment:
Response to Request for Additional Information cc:
USNRC Region I, Regional Administrator w/attachment USNRC Senior Resident Inspector, NMP USNRC Project Manager, NMP A. L. Peterson, NYSERDA B. Frymire, NYSPSC A. Kauk, NYSPSC
ATTACHMENT Nine Mile Point Nuclear Station Unit 2 Renewed Facility Operating License No. NPF-69 NRC Docket No. 50-410 Response to Request for Additional Information
Attachment Response to Request for Additional Information Page 1 of 2 NMP2 MSIV Test Pressure Reduction Docket No. 50-410 INTRODUCTION By letter dated January 29, 2025, (Agencywide Documents Access and Management System (ADAMS) Accession No. ML25029A181), Constellation Energy Generation, LLC (the licensee),
submitted a license amendment request (LAR) for Nine Mile Point Nuclear Station, Unit No. 2 (NMP2). Specifically, the licensee requested changes to the NMP2 Technical Specifications (TS) Surveillance Requirement (SR) 3.6.1.3.12 to reduce the main steam isolation valve (MSIV) test pressure value from >40 pounds per square inch gauge (psig) to >25 psig. In addition, the licensee is requesting a corresponding change to the maximum allowable leakage through each MSIV from <50 standard cubic feet per hour (scfh) to <39 scfh.
The U.S. Nuclear Regulatory Commission (NRC) staff has reviewed the information provided in the submittal and has determined that additional information as requested in the below is needed to complete its review. This request for additional information (RAI) is necessary for the staff to evaluate the licensees scaled approach for the new maximum allowable leakage value, to ensure that the leakage considered in the licensees accident analysis is still being met, and to confirm that applicable regulations are met.
REGULATORY BASIS The regulation at Title 10 of the Code of Federal Regulations (10 CFR), Section 50.54(o),
requires primary reactor containments for water-cooled power reactors be subject to the requirements of Appendix J to 10 CFR Part 50, "Leakage Rate Testing of Containment of Water-Cooled Nuclear Power Plants." Appendix J specifies containment leakage testing requirements, including the types required to ensure the leak-tight integrity of the primary reactor containment and systems and components which penetrate the containment. In addition, Appendix J discusses leakage rate acceptance criteria, test methodology, frequency of testing and reporting requirements for each type of test.
The regulation at 10 CFR 50.36(c)(3) requires TS to include items in the "Surveillance Requirements" category, which 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.
REQUEST FOR ADDITIONAL INFORMATION The licensee is requesting to lower the MSIV test pressure value from >40 psig to >25 psig and states that this proposed reduction in test pressure would also require an adjustment to the maximum allowable leakage through each MSIV to account for the change in test pressure. As a result, the licensee is proposing to adjust the maximum allowable leakage through each MSIV from 50 scfh to 39 scfh. Specifically, the licensee states in the LAR:
in the NMP2 TS to the proposed test pressure, the equivalent maximum allowable The NRC staff noted that the licensee did not provide the method used to calculate the new maximum allowable leakage limit. That NRC staff requests the licensee to (1) provide a more
Attachment Response to Request for Additional Information Page 2 of 2 NMP2 MSIV Test Pressure Reduction Docket No. 50-410 detailed explanation of the scaled approach, specifying the exact method (e.g., conversion factor) used to determine the new maximum allowable leakage limit and (2) verify that the new proposed leakage rate is bounded by the accident analyses in the current licensing basis.
CEG RESPONSE (1) The analysis used a simplified flow rate equation of flow rate to the square root of the differential pressure to calculate the equivalent leakage limit through each MSIV at the proposed reduced test pressure as follows:
=
=
=
=
= 39 Where:
is the maximum leakage rate in SCFH @ 40 psig (50 SCFH) is the maximum leakage rate in SCFH @ 25 psig is the Current Test Pressure (40 psig) is the Proposed Test Pressure (25 psig) is the Loss Coefficient (Constant)
Based on the above calculation, the equivalent maximum leakage rate to 50 SCFH at 40 psig is 39 SCFH at 25 psig.
(2) The proposed test pressure (25 psig) and the associated leakage limit (39 SCFH) is equivalent and conservative to the current test method (40 psig, 50 SCFH) to properly assess MSIV performance and condition. Therefore, the new proposed leakage rate through each MSIV (39 SCFH) is bounded by the accident analyses in the current licensing basis.