ML25344A371
| ML25344A371 | |
| Person / Time | |
|---|---|
| Site: | Limerick  |
| Issue date: | 12/10/2025 |
| From: | Para W Constellation Energy Generation |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| Download: ML25344A371 (0) | |
Text
200 Energy Way Kennett Square, PA 19348 www.ConstellationEnergy.com December 10, 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 Draft Safety Evaluation of CIM Common Cause Failure Excerpt 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),
RESPONSE REQUESTED: CIM CCF Excerpt From Limerick Digital I&C LAR Draft Safety Evaluation (L-2022-LLA-0140), dated November 13, 2025 (ADAMS Accession No. ML25336A022).
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) excerpt related to the Control Interface Module (CIM) for CEG review and comment. CEG has completed its review of the draft SE excerpt and provides comments contained within the Enclosure. The comments are not identified as proprietary.
LGS DMP LAR - Comments on Draft SE Excerpt NRC Docket Nos. 50-352 and 50-353 December 10, 2025 Page 2 This letter contains no regulatory commitments.
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
Enclosure:
CEG Comments on the Draft Safety Evaluation Excerpt Related to the CIM cc:
USNRC Region I, Regional Administrator USNRC Project Manager, LGS USNRC Senior Resident Inspector, LGS Para, Wendi E 2025.12.10 11:32:13 -05'00'
Enclosure CEG Comments on the Draft Safety Evaluation Excerpt Related to the CIM
Enclosure CEG Comments on the Draft Safety Evaluation Excerpt Related to the CIM Page 1 of 3 Item #
Page #
Location Comment 1
Page 1 Lines 36-37 It may be useful to consider whether there is a specific reason for referring to safety function rather than protection, as protection function is language used in the GDC and BTP 7-19. For clarity and accuracy, it may be useful to consider rewording this statement.
2 Page 2 Line 14 It may be useful to consider whether the use of the term complex is necessary in this context. The NUREG provides guidance for FPGA applications, and the complexity of a design is influenced by its specific use case. Since the characterization of complexity can be subjective and may reflect the basis established in the 2010 era definition within the NUREG, it may be useful to consider rewording this statement to help maintain objectivity and consistency.
3 Page 5 Line 51 There is a spelling error; the word alterative should be alternative.
4 Page 6 Line 12-17 It may be useful to consider that the statement regarding the CIM not qualifying as a simple device is subjective and could potentially set a precedent. This introduces a threshold between simple and complex devices that is not explicitly supported by the language in BTP 7-19 or NUREG/CR-7006. To maintain flexibility while ensuring accuracy, one option could be to remove the first sentence and revise the second to: the staff evaluated the CIM as a complex programmable device, rather than the staff determined that the CIM is a complex programmable device. This adjustment could help prevent the language from being restrictive to applicants and NRC reviewers in future evaluations, while still clearly documenting the decision-making process.
5 Page 6 Lines 40-46 Given that the Limerick alternative approach relies on the combined content of Sections 3.3.4.2.1 and 3.3.4.2.2 to meet BTP 3.1.3 evaluating these sections separately and providing interim conclusion statements does not accurately reflect the entire application and safety determination. For clarity and accuracy, it may be useful to consider removing interim conclusion statements.
If the statements are retained, it may be useful to consider providing additional detail regarding what was partially tested, including specific examples of items that were not tested. This clarification could help facilitate closure of any identified testing gaps in the future, while maintaining transparency in the documentation.
Enclosure CEG Comments on the Draft Safety Evaluation Excerpt Related to the CIM Page 2 of 3 Item #
Page #
Location Comment 6
Page 8 Lines 24-41 Given that the Limerick alternative approach relies on the combined content of Sections 3.3.4.2.1 and 3.3.4.2.2 to meet BTP 3.1.3 evaluating these sections separately and providing interim conclusion statements does not accurately reflect the entire application and safety determination. For clarity and accuracy, it may be useful to consider removing interim conclusion statements.
7 Page 11 Line 40 Statements in Section 3.3.4.2.4, Conclusion, and the placement of Section 3.3.4.2.3, between the Sections credited in the alternative approach (3.3.4.2.1 and 3.3.4.2.2) and the Conclusion Section (3.3.4.2.4), indicate the Limerick-specific operator actions and Chapter 15 analysis are credited in the safety determination. It may be useful to consider whether it is necessary to credit these elements in concluding that the CIM is not susceptible to a CCF. If the Limerick-specific operator actions and Chapter 15 analysis are not necessary to be credited in the safety determination, but the information could provide useful context for future applicants and reviewers, it could be considered for inclusion in a new, separate section following Section 3.3.4.2.4, Conclusion.
Additionally, for clarity and accuracy, it may be useful to consider adding a statement to the new section indicating that the Limerick-specific operator actions and Chapter 15 analysis were not credited in the alternative approach or the safety determination. This adjustment could help prevent unintended impacts on the Limerick licensing basis and avoid setting a precedent for future applicants.
8 Page 14 Line 43 Given that the Limerick alternative approach relies on the combined content of sections 3.3.4.2.1 and 3.3.4.2.2 to meet BTP 3.1.3 evaluating these sections separately and providing interim conclusion statements does not accurately reflect the entire application and safety determination. For clarity and accuracy, it may be useful to consider removing interim conclusion statements.
9 Page 14 Line 46 The conclusion statements refer to the Limerick-specific operator actions and Chapter 15 analysis. Refer to Item 7 related to the comments on crediting Limerick-specific operator actions and Chapter 15 analysis in the safety determination.
Enclosure CEG Comments on the Draft Safety Evaluation Excerpt Related to the CIM Page 3 of 3 Item #
Page #
Location Comment 10 Page 15 Line 7 The Limerick alternative approach utilizes three types of self-diagnostics to detect faults, as outlined in Section 3.3.4.2.2 on pages 8 - 9. The Limerick PPS application provides operators with alarms, indications, and alerts generated by these self-diagnostic functions, as described in Section 3.3.4.2.2 on pages 9-11. For clarity and accuracy, it may be useful to consider rewording this statement.
11 Page 15 Lines 11-13 The conclusion statements refer to the Limerick-specific operator actions and Chapter 15 analysis. Refer to Item 7 related to the comments on crediting Limerick-specific operator actions and Chapter 15 analysis in the safety determination.
12 Page 15 Lines 16-22 The current wording states the conclusion but does not explain what evidence or analyses support it. It may be useful to consider adding references to the underlying evaluations to improve clarity and transparency.
Examples of supporting details that could be mentioned include the extensive testing results that demonstrate CIM performance under design basis conditions, the Failure Modes and Effects Analysis (FMEA) findings that address potential vulnerabilities, the diagnostic capabilities of the CIM that detect and mitigate faults, and the independent displays and controls in PPS/DPS that provide redundancy and diversity. Including these elements would make the basis for the conclusion more explicit and easier for future applicants and NRC reviewers to understand.
Additionally, the conclusion statements refer to the Limerick-specific operator actions and Chapter 15 analysis. Refer to Item 7 related to the comments on crediting Limerick-specific operator actions and Chapter 15 analysis in the safety determination.
13 Page 15 Line 17 It may be useful to consider whether there is a specific reason for referring to D3 measures rather than D3 coping, as D3 coping is the standard language in the Limerick submittals and BTP 7-19. For clarity and accuracy, it may be useful to consider rewording this statement.