ML25363A085
| ML25363A085 | |
| Person / Time | |
|---|---|
| Site: | Limerick  |
| Issue date: | 12/29/2025 |
| From: | Para W Constellation Energy Generation |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| Download: ML25363A085 (0) | |
Text
200 Energy Way Kennett Square, PA 19348 www.ConstellationEnergy.com December 29, 2025 U.S. Nuclear Regulatory Commission Washington, DC 20555-0001 ATTN: Document Control Desk Limerick Generating Station, Units 1 and 2 Renewed Facility Operating License Nos. NPF-39 and NPF-85 NRC Docket Nos. 50-352 and 50-353
Subject:
Review of Entire Draft Safety Evaluation from the Digital Plant Protection System License Amendment Request
References:
- 1. Constellation Energy Generation, LLC (CEG) letter to the U.S. Nuclear Regulatory Commission (NRC), "License Amendment Request to Revise the Licensing and Design Basis to Incorporate the Replacement of Existing Safety-Related Analog Control Systems with a Single Digital Plant Protection System (PPS)," dated September 26, 2022 (NRC Agencywide Documents Access and Management System (ADAMS) Accession No. ML22269A569).
- 2. CEG letter to the NRC, "Resubmittal of License Amendment Request to Revise the Licensing and Design Basis to Incorporate the Replacement of Existing Safety-Related Analog Control Systems with a Single Digital Plant Protection System (PPS) - To Address Proprietary Issues with INL HFE Reports," dated September 12, 2023 (ADAMS Accession No. ML23255A095).
- 3. Email from Michael Marshall, (NRC) to Ashley Rickey (CEG), Transmittal of Draft Safety Evaluation: Limerick 1 and 2 - L-2022-LLA-0140 - Draft Safety Evaluation, dated December 11, 2025.
In Reference 1 CEG requested a License Amendment Request (LAR) to facilitate replacement of the Limerick Generating Station (LGS), Units 1 and 2 existing safety-related analog control systems with a single digital PPS. In Reference 2, CEG submitted an LAR supplement that replaced in its entirety the original LAR. CEG replaced the original submittal to address issues associated with proprietary/non-proprietary information.
In the Reference 3 email, the NRC provided a draft Safety Evaluation (SE) for CEG review and comment. CEG has completed its review of the draft SE and provides comments contained within the Enclosure. The comments are not identified as proprietary.
This letter contains no regulatory commitments.
LGS DMP LAR - Comments on Entire Draft SE NRC Docket Nos. 50-352 and 50-353 December 29, 2025 Page 2 If you have any questions regarding this submittal, then please contact Ms. Ashley Rickey at Ashley.Rickey@constellation.com.
Respectfully, Wendi Para Senior Manager, Licensing Constellation Energy Generation, LLC Attachment CEG Comments on the Entire Draft Safety Evaluation cc:
USNRC Region I, Regional Administrator USNRC Project Manager, LGS USNRC Senior Resident Inspector, LGS Para, Wendi E 2025.12.29 09:59:20
-05'00'
Attachment CEG Comments on the Entire Draft Safety Evaluation
Attachment CEG Comments on the Draft Safety Evaluation Page 1 of 3 Item #
Page Location Comment 1
17 Lines 24 - 25 The HPCI system summary does not include the system tie to Core Spray. It may be useful to consider rewording the summary starting on Line 24 for accuracy and clarity. One option could be to use the HPCI system summary below, from the LTR, Revision 1:
The HPCI system provides and maintains an adequate coolant inventory inside the reactor vessel to limit fuel clad temperatures resulting from postulated small breaks in the RCPB. HPCI uses a large steam-driven pump to inject water into one of the main feedwater (FW) lines and one of the Core Spray (CS) headers to the Reactor Pressure Vessel (RPV).
2 27 Line 12 The NRC first references the CIM Audit on page 27.
This audit differs from the Open Items and EQ Audits first referenced in the draft Safety Evaluation on pages 69 and 141, respectively. The NRC provides the ADAMS Accession Numbers for the Open Items and EQ Audits. For consistency and accuracy, it may be useful to consider providing the Accession Numbers for the two CIM Audits on Page 27 after the first reference.
3 33 Line 2 Line 2 states, the ABB master programming language control configuration software development environment. For accuracy, the reference to ABB should be changed to Advant.
4 49 Lines 2 - 5 In order to be consistent with LIM-25-010-P, it may be useful to consider rewording the sentence starting on Line 2 for accuracy and clarity. One option could be to use the wording below:
Although the PPS uses inter-channel communication for voting purposes, each division can maintain functional independence because each data link is redundant and when both redundant data links are lost, the LCL will default to a trip state for RPS signals and to a known conservative state for NSSSS/ECCS/RCIC signals.
3 87 Lines 27 - 29 LTR, Revision 1, Section A.6.3.3 has updated discussion on
Attachment CEG Comments on the Draft Safety Evaluation Page 2 of 3 the HARP Analysis. It states, The HARP uses electromechanical relays for some ECCS/NSSS actuations but provides justification that the response time testing of the HARP can be eliminated from surveillance on the basis that operability of the relay will be verified during surveillance testing. It may be useful to consider rewording the sentence starting on Line 27 for accuracy and clarity. One option could be to use the wording below:
The RPS TU and HARP contain no software and have been screened out from contributing to response time degradation, if operability can be verified by the required SR tests.
4 87 Lines 35 - 39 The conclusion statement in Lines 38-39 is not consistent with Draft SE Lines 27-29 or LTR, Revision 1. Both state response time testing is not needed for the RPS TU and HARP. It may be useful to consider rewording the sentence starting on Line 35 for accuracy and clarity. One option could be to use the wording below:
Based on the similarities between the architecture in WCAP-18461-P-A and the Limerick PPS architecture, the NRC staff found that manual response time tests are not needed for the safety signal paths with the exception that components DI621, DO620, RPS TU, and HARP still require periodic surveillance testing to verify operability.
5 109 Line 15 There is a typographical error; the word dedicated should be designated, as reflected in LIM-25-010-P.
6 118 Lines 17 and 20 The reference to operator actions in Lines 17 and 20 are not consistent with the NRCs proposed changes to the CIM portion of the SE which replaced this term with the phrase, operator knowledge. It may be useful to consider rewording the paragraph starting on Line 16 to ensure consistency. One option could be to use the wording below:
This reduction allowed the NRC staff to consider self-diagnostic capabilities and controls and operator knowledge of those features to make a regulatory finding on whether the licensee has demonstrated that CCF vulnerabilities in the CIM portion of the proposed PPS have been adequately addressed. The NRC staffs evaluation of the available self-diagnostic
Attachment CEG Comments on the Draft Safety Evaluation Page 3 of 3 capabilities of the Limerick PPS is in Section 3.3.4.2.2 of this SE. The NRC staffs evaluation of the controls and operator knowledge of those features to address a design basis event coincident with a CCF of the CIMs, is in Section 3.3.4.2.3 of this 22 SE.
7 191 Lines 1 - 2 The sentence as-written is incomplete. It may be useful to consider rewording the sentence starting on Line 1 for accuracy and clarity. One option could be to use the wording below:
The NRC staff reviewed the fiber optic cabling external to the PPS cabinets, including associated connections, to verify their qualification for the anticipated environmental conditions at the installed locations.