ML25226A079
| ML25226A079 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 08/14/2025 |
| From: | James Holloway Dominion Energy, Dominion Energy Nuclear Connecticut |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| 24-349B | |
| Download: ML25226A079 (1) | |
Text
Dominion Energy Nuclear Connecticut, Inc 5000 Dominion Boulevard, Glen Allen, VA23060 DominionEnergy.com U. S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, DC 20555 August 14, 2025 DOMINION ENERGY NUCLEAR CONNECTICUT, INC MILLSTONE POWER STATION UNIT 3 5'1-Dominion p Energy Serial No.:
NRA/NDM:
Docket No.:
License No.:
24-3498 RO 50-423 NPF-49 RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION REGARDING PROPOSED AMENDMENT TO REVISE TECHNICAL SPECIFICATIONS RELATED TO CONTROL BUILDING ISOLATION, ACCIDENT MONITORING INSTRUMENTATION, ACCUMULATOR AND REFUELING WATER STORAGE TANK BORON CONCENTRATION LIMITS, AND SECONDARY CONTAINMENT SURVEILLANCE REQUIREMENTS By letter dated March 20, 2025 (ADAMS Accession No. ML25079A225), Dominion Energy Nuclear Connecticut, Inc. (DENC) submitted a license amendment request (LAR) to revise the technical specifications (TSs) for Millstone Power Station Unit 3 (MPS3) related to control building isolation, accident monitoring instrumentation, accumulator and refueling water storage tank (RWST) boron concentration limits, and secondary containment surveillance requirements. The proposed TS changes include the relocation of the boron concentration limits in TS Limiting Condition for Operation (LCO) 3.5.1 (Accumulators) and TS LCO 3.5.4 (RWST) to the Core Operating Limit Report (COLR).
The addition of TS 3.5.1 and TS 3.5.4 was also proposed in MPS3 TSs 6.9.1.6.a and 6.9.1.6.b for the applicable methodologies to establish the core operating limits included in the COLR for accumulators and RWST boron concentration limits.
On June 18, 2025, the U.S. Nuclear Regulatory Commission (NRC) staff sent DENC the subject Request for Additional Information (RAI) as a draft e-mail. On July 15, 2025, the NRC issued the final version of the RAI (ADAMS Accession No. ML25197A608) related to the proposed LAR. DENC agreed to respond within 30 days of issuance, or no later than August 14, 2025.
The attachment provides DENC's response to the NRC's RAI on the proposed LAR.
Serial No.: 24-349B Docket No.: 50-423 Page 2 of 2 If you have any questions or require additional information regarding this submittal, please contact Nick Maynard at (804) 273-3910.
I declare under penalty of perjury that the foregoing is true and correct.
Executed on August 14, 2025.
Sincerely, James E. Holloway Vice President - Nuclear Engineering & Fleet Support
Attachment:
Response to RAI on LAR to Revise Control Building Isolation, Accident Monitoring Instrumentation, Accumulator and Refueling Water Storage Tank Boron Concentration Limits, and Secondary Containment Surveillance Requirements Technical Specifications Commitments made in this letter: None.
cc:
U. S. Nuclear Regulatory Commission Region I 475 Allendale Road, Suite 102 King of Prussia, PA 19406-1415 Richard V. Guzman Senior Project Manager U.S. Nuclear Regulatory Commission One White Flint North, Mail Stop 9 E3 11555 Rockville Pike Rockville, MD 20852-2738 NRC Senior Resident Inspector (w/attachment)
Millstone Power Station Director, Radiation Division Department of Energy and Environmental Protection 79 Elm Street Hartford, CT 06106-5127 f
1
ATTACHMENT MILLSTONE POWER STATION UNIT 3 Serial No.: 24-349B Docket No.: 50-423 RESPONSE TO RAI ON LAR TO REVISE CONTROL BUILDING ISOLATION, ACCIDENT MONITORING INSTRUMENTATION, ACCUMULATOR AND REFUELING WATER STORAGE TANK BORON CONCENTRATION LIMITS, AND SECONDARY CONTAINMENT SURVEILLANCE REQUIREMENTS TECHNICAL SPECIFICATIONS Dominion Energy Nuclear Connecticut, Inc Millstone Power Station Unit 3
Serial No.: 24-3498 Docket No.: 50-423 Attachment, Page 1 of 7 RESPONSE TO RAI ON LAR TO REVISE CONTROL BUILDING ISOLATION, ACCIDENT MONITORING INSTRUMENTATION, ACCUMULATOR AND REFUELING WATER STORAGE TANK BORON CONCENTRATION LIMITS, AND SECONDARY CONTAINMENT SURVEILLANCE REQUIREMENTS TECHNICAL SPECIFICATIONS By letter dated March 20, 2025 (ADAMS Accession No. ML25079A225), Dominion Energy Nuclear Connecticut, Inc. (DENC) submitted a license amendment request (LAR) to revise the technical specifications (TSs) for Millstone Power Station Unit 3 (MPS3) related to control building isolation, accident monitoring instrumentation, accumulator and refueling water storage tank (RWST) boron concentration limits, and secondary containment surveillance requirements. The proposed TS changes include the relocation of the boron concentration limits in TS Limiting Condition for Operation (LCO) 3.5.1 (Accumulators) and TS LCO 3.5.4 (RWST) to the Core Operating Limit Report (COLR).
The addition of TS 3.5.1 and TS 3.5.4 was also proposed in MPS3 TSs 6.9.1.6.a and 6.9.1.6.b for the applicable methodologies to establish the core operating limits included in the COLR for accumulators and RWST boron concentration limits.
On June 18, 2025, the U.S. Nuclear Regulatory Commission (NRC) staff sent DENC the subject Request for Additional Information (RAI) as a draft e-mail. On July 15, 2025, the NRC issued the final version of the RAI (ADAMS Accession No. ML25197A608) related to the proposed LAR. DENC agreed to respond within 30 days of issuance, or no later than August 14, 2025.
This attachment provides DENC's response to the NRC's RAI on the proposed LAR.
RAl-1 Methodology for Determining the Boron Concentration Limits in Accumulators and RWST The licensee indicates on page 16 of 25 of Attachment 1 to the LAR that the methodology documented in the NRG-approved topical report (TR) VEP-FRD-42-A, Revision 2, is applicable for use in determining the boron concentration limits in accumulators and RWST. As indicated on page 9 of the NRC staff's safety evaluation (ML031621014), the TR safety evaluation report (SER) approved the use of VEP-FRD-42, specifically for Westinghouse and Framatome ANP Advanced Mark-BW fuel. Accordingly, the NRC placed the follow Condition and Limitation upon VEP-FRD-42:
Prior to the use of the Topical Report VEP-FRD-42, Revision 2, methodology for fuel types other than Westinghouse and Framatome ANP Advanced Mark-BW fuel, VEPCO must confirm that the impact of the fuel design and its specific features can be accurately modeled with the VEPCO nuclear design and safety analysis codes and methods as discussed in its submittal dated May 13, 2002. Should the changes necessary to accommodate another fuel product require changes to the reload methodology of Topical Report VEP-FRD-42, Revision 2, these proposed changes are required to be submitted for prior NRC review and approval.
Serial No.: 24-3498 Docket No.: 50-423 Attachment, Page 2 of 7 Clarify if there are fuel types other than Framatome ANP Advanced Mark-BW and Westinghouse fuel (such as GAIA fuel) to be installed in the MPS3 core for this application and describe how those fuel types comply with the Condition and Limitation of VEP-FRD-42 cited above.
DENC Response to RAl-1 Millstone Power Station Unit 3 (MPS3) has loaded and is operating with Framatome GAIA fuel following the completion of the spring 2025 refueling outage. The transition to Framatome GAIA fuel from Westinghouse RFA-2 fuel was implemented under the provisions of 10 CFR 50.59, in conjunction with receiving explicit approval from the Nuclear Regulatory Commission (NRC) via Amendments 287, 289, 290, and 291 to the MPS3 operating license (References 1 through 4 ). The application of the Dominion Energy Nuclear Connecticut Inc. (DENC) reload methodology defined in VEP-FRD-42-A (Reference 5) to Framatome GAIA fuel was performed under the provisions of 10 CFR 50.59. Specifically, this was done by addressing the Condition and Limitation within the Safety Evaluation Report (SER) on Revision 2 of VEP-FRD-42-A, related to application of the method to fuel types other than Westinghouse and Framatome ANP Advanced Mark-BW fuel.
VEP-FRD-42-A Revision 2 Licensing History Summary DENC employs the methodology of VEP-FRD-42-A, Revision 2, Minor Revision 2 (Reference 5) when designing reload cores for MPS3.
Minor Revision 1 (Reference 6) to VEP-FRD-42-A, Revision 2 (Reference 7) was issued in August 2003, and incorporated the allowed use of the Studsvik Core Management System (CMS) suite comprised of CASMO4 and SIMULATE3 to perform core neutronics predictions. Minor Revision 1 was issued under the provisions of 10 CFR 50.59. The incorporation of the Studsvik CMS code suite comprised of CASMO4 and SIMULATE3 into VEP-FRD-42-A, as documented in the NRC approved methodology of DOM-NAF P-A (Reference 8), did not constitute a departure from a method of evaluation requiring NRC review and approval per the NRG-endorsed 50.59 guidance (References 9 and 10).
VEP-FRD-42, Revision 2, Minor Revision 1 is the cited version of VEP-FRD-42 in Amendment 268 (Reference 11) to the MPS3 Operating License.
Following NRC approval of its application to MPS3 (Reference 11 ), Minor Revision 2 (Reference 5) to VEP-FRD-42-A, Revision 2 (Reference 7) was issued in October 2017.
This minor revision to the report allowed use of the Studsvik Core Management System (CMS5) suite comprised of CASMO5 and SIMULATES to perform core neutronics predictions, marked the use of the Virginia Power PDQ Two Zone and NOMAD models as obsolete analytical models, and reflected the application of VEP-FRD-42-A to MPS3.
Minor Revision 2 was issued under the provisions of 10 CFR 50.59. The incorporation of the Studsvik CMS5 code suite into VEP-FRD-42-A, as documented in the NRC approved methodology of SSP-14-P01/028-TR-P-A (Reference 12), did not constitute a departure
Serial No.: 24-3498 Docket No.: 50-423 Attachment, Page 3 of 7 from a method of evaluation requiring NRC review and approval per the NRG-endorsed 50.59 guidance (References 9 and 10). The updates made to reflect the application of VEP-FRD-42-A to MPS3 were bounded by the NRC approval granted as Amendment 268 (Reference 11 ).
Assessment of the VEP-FRD-42-A Condition and Limitation on Applicability to Framatome GAIA VEP-FRD-42-A contains a Condition and Limitation addressing the applicability of the method to fuel types other than Westinghouse and Framatome ANP Advanced Mark-BW fuel. The Condition and Limitation is reported below:
"Prior to the use of the Topical Report VEP-FRD-42, Revision 2, methodology for fuel types other than Westinghouse and Framatome ANP Advanced Mark-BW fuel, VEPCO must confirm that the impact of the fuel design and its specific features can be accurately modeled with the VEPCO nuclear design and safety analysis codes and methods as discussed in its submittal dated May 13, 2002. Should the changes necessary to accommodate another fuel product require changes to the reload methodology of Topical Report VEP-FRD-42, Revision 2, these proposed changes are required to be submitted for prior NRC review and approval."
As part of the implementation of the Framatome GAIA fuel product at MPS3, DENC addressed this Condition and Limitation under the provisions of 10 CFR 50.59 and concluded that no changes were necessary to reload methodology of VEP-FRD-42-A to accurately model the Framatome GAIA fuel product.
The Reload Nuclear Design Methodology of VEP-FRD-42-A consists of three major analytical models: CMS5 (for neutronic analysis), RETRAN (for non-Loss of Coolant Accident (LOCA) system transient response), and VIPRE-D (for Core Thermal-Hydraulics). Each of these analytical models are governed via NRC approved topical reports. CMS5 is described in SSP-14-P01/028-TR-P-A (Reference 12). Dominion Energy's RETRAN model is described in VEP-FRD-41-P-A (Reference 13). VIPRE-D is described in DOM-NAF-2-P-A, with Appendix F describing the ORFEO-GAIA and ORFEO-NMGRID CHF correlations (Reference 14). The models of References 12, 13, and 14 are applicable to Framatome GAIA fuel.
Assessment of Neutronics Model Applicability to Framatome GA/A SSP-14-P01/028-TR-P-A (Reference 12) describes the neutronics model used to analyze the reload core. SSP-14-P01/028-TR-P-A contains a Limitations/Conditions describing the fuel features for which its modeling capability is applicable. The Framatome GAIA fuel utilized at MPS3 is described in Attachments 3 (proprietary) and 4 (non-proprietary) of Reference 15 and was approved as Amendment 290 (Reference 3). The following items summarize how the Limitation/Condition of SSP-14-P01/028-TR-P-A is met by Framatome GAIA fuel:
Fuel and Poison:
Serial No.: 24-349B Docket No.: 50-423 Attachment, Page 4 of 7 o Uranium Oxide fuel enriched to more than 5 wt% U-235 (TS 5.3.1 ).
o Framatome GAIA fuel contains a 17x17 lattice array.
o Theoretical density is between 0.94 and 0.95.
o Gadolinia is used as an integral poison and is limited to less than 12%.
o Discrete absorbers and integral fuel burnable absorbers (IFBA) are not used within Framatome GAIA fuel.
Cladding:
o Framatome GAIA fuel utilizes M5 cladding material.
Structural Material:
o Framatome GAIA fuel utilizes NRC approved materials (Q12, M5, and Alloy718).
Burnup:
o MPS3 is limited to a lead rod average burnup of 62 GWD/MTU.
Therefore, no changes to VEP-FRD-42-A (Reference 5) that require NRC approval were identified to apply the model of SSP-14-P01/028-TR-P-A (Reference 12) to Framatome GAIA fuel.
Assessment of non-LOCA System Transient Response Model Applicability to Framatome GA/A VEP-FRD-41-P-A (Reference 13) describes the use of RETRAN to perform non-LOCA safety analysis. The fuel modeling within RETRAN is simplistic, as it takes input in the form of geometric parameters and material property lookup tables. The Framatome GAIA fuel material property lookup tables were determined from the fuel vendor's approved fuel performance code, as required by Section 5.3 of VEP-FRD-41-P-A. Reactivity modeling is driven by a point kinetics model. The inputs to the point kinetics are shown to be bounding of the reload core via the detailed fuel neutronic modeling defined by VEP-FRD-42-A and SSP-14-P01/028-TR-P-A. Therefore, no changes to VEP-FRD-42-A that require NRC approval were identified to apply the model of VEP-FRD-41-P-A to Framatome GAIA fuel.
Assessment of Core Thermal-Hydraulics Model Applicability to Framatome GA/A DOM-NAF-2-P-A including Appendix F (Reference 14) describes the core thermal hydraulic model used to assess the departure from nucleate boiling (DNB) performance of the fuel. VEP-FRD-42-A requires that the core thermal hydraulics method be listed within the Core Operating Limits Report (COLR). Amendment 291 (Reference 4) to the MPS3 Operating License acquired this approval. Therefore, no changes to Reference 5
Serial No.: 24-349B Docket No.: 50-423 Attachment, Page 5 of 7 that require NRC approval were identified to apply the model of DOM-NAF-2-P-A including Appendix F to Framatome GAIA fuel.
Assessment of Event Specific Discussion within VEP-FRD-42-A Applicability to Framatome GA/A Section 3.3.4 of VEP-FRD-42-A (Reference 5) discusses key parameter confirmations for various events. Two specific events required additional consideration, due to the use of Framatome safety analysis methods to analyze Rod Ejection (Section 3.3.4.3) and Loss of Coolant Accident (LOCA) Peaking Factor Evaluation (Section 3.3.4.5). The Framatome AREA method analyzes the rod ejection event of Framatome GAIA fuel at MPS3 (Reference 4 ), and the Framatome LOCA methods analyze the response of GAIA fuel to a LOCA (Reference 2). The description of the key event parameters requiring reload verification for rod ejection and LOCA is focused on reactivity parameters, peaking factors, and axial power shapes. The description within VEP-FRD-42-A remains valid for the confirmation of these key parameters, even with the use of the Framatome safety analyses for rod ejection and LOCA. Therefore, no changes to VEP-FRD-42-A requiring NRC approval were identified.
Conclusion of the Assessment of the VEP-FRD-42-A Condition and Limitation on Applicability to Framatome GAIA The application of VEP-FRD-42-A to MPS3 reload cores containing Framatome GAIA fuel is within the Condition and Limitation of its SER, allowing DENC to apply the reload methodology of VEP-FRD-42-A to Framatome GAIA fuel without prior NRC review and approval under 10 CFR 50.59.
References
- 1. Letter to E. S. Carr (Dominion Energy) from R. V. Guzman (US NRC), "Millstone Power Station, Unit No. 3 - Issuance of Amendment No. 287 Re: Supplement to Spent Fuel Pool Criticality Safety Analysis (EPID L-2022-LLA-0196)," dated September 26, 2023 (ADAMS Accession No. ML23226A005).
- 2. Letter to E. S. Carr (Dominion Energy) from R. V. Guzman (US NRC), "Millstone Power Station, Unit No. 3 - Issuance of Amendment No. 289 to Use Framatome Loss-of-Coolant Accident Evaluation Methodologies for Establishing Core Operating Limits (EPID L-2023-LLA-0065)," dated May 21, 2024 (ADAMS Accession No. ML24109A002).
- 3. Letter to E. S. Carr (Dominion Energy) from R. V. Guzman (US NRC), "Millstone Power Station, Unit No. 3 - Issuance of Amendment No. 290 to Revise Technical Specifications for Reactor Core Safety Limits, Fuel Assemblies, and Core Operating Limits Report for Use of Framatome GAIA Fuel (EPID L-2023-LLA-0074)," dated June 4, 2024 (ADAMS Accession No. ML24128A276).
Serial No.: 24-3498 Docket No.: 50-423 Attachment, Page 6 of 7
- 4. Letter to E. S. Carr (Dominion Energy) from R. V. Guzman (US NRC), "Millstone Power Station, Unit No. 3 -
Issuance of Amendment No. 291 to Support Implementation of Framatome GAIA Fuel (EPID L-2023-LLA-0150)", dated November 19, 2024 (ADAMS Accession No. ML24296B234 ); as supplemented by letter dated December 12, 2024 (ADAMS Accession No. ML24346A253).
- 5. VEP-FRD-42-A Revision 2, Minor Revision 2, "Reload Nuclear Design Methodology," October 2017 (ADAMS Accession No. ML18012A098).
- 6. VEP-FRD-42-A Revision 2, Minor Revision 1, "Reload Nuclear Design Methodology," August 2003 (ADAMS Accession No. ML15313A149).
- 7. VEP-FRD-42-A Revision 2, Minor Revision 0, "Reload Nuclear Design Methodology," August 2003 (ADAMS Accession No. ML032680720).
- 8. DOM-NAF-1-P-A, Revision 0, Minor Revision 0, "Qualification of the Studsvik Core Management System Reactor Physics Methods for Application to North Anna and Surry Power Stations," June 2003 (ADAMS Accession No. ML031690108).
- 9. NEI 96-07, Revision 1, Guidelines for 10 CFR 50.59 Implementation," November 2000 (ADAMS Accession No. ML003771157).
- 10. Regulatory Guide 1.187, Revision 3, "Guidance for Implementation of 10 CFR 50.59, 'Changes, Tests, and Experiments,"' June 2021 (ADAMS Accession No. ML21109A002).
- 11. Letter to D. A. Heacock (Dominion Energy) from R. V. Guzman (US NRC),
"Millstone Power Station, Unit No. 3 - Issuance of Amendment Adopting Dominion Core Design and Safety Analysis Methods and Addressing the Issues Identified in Three Westinghouse Communication Documents (CAC No. MF6251 )," dated July 28, 2016 (ADAMS Accession No. ML16131A728).
- 12. SSP-14-P01/028-TR-P-A, Revision 0, "Generic Application of the Studsvik Scandpower Core Management System to Pressurized Water Reactors,"
September 2017 (ADAMS Accession No. ML17279A986).
- 13. VEP-FRD-41-P-A Revision 0, Minor Revision 3, "VEPCO Reactor System Transient Analysis Using the RETRAN Computer Code," January 2019 (ADAMS Accession No. ML19141A148).
- 14. DOM-NAF-2-P-A, Revision 0, Minor Revision 5, "Reactor Core Thermal-Hydraulics Using the VIPRE-D Computer Code," May 2024 (ADAMS Accession No. ML24170B053).
Serial No.: 24-349B Docket No.: 50-423 Attachment, Page 7 of 7
- 15. Letter to USNRC from J. E. Holloway (Dominion Energy), "Dominion Energy Nuclear Connecticut, Inc., Millstone Power Station Unit 3, Proposed Amendment to Revise Technical Specifications for Reactor Core Safety Limits, Fuel Assemblies, and Core Operating Limits Report Related to Framatome GAIA Fuel,"
dated May 23, 2023 (ADAMS Accession No. ML23145A195).