ML24088A330

Regulatory Audit Plan in Support of License Amendment Request to Implement Framatome Gaia Fuel

ML24088A330
Person / Time
Site:	Millstone
Issue date:	04/04/2024
From:	Richard Guzman NRC/NRR/DORL/LPL1
To:	Carr E Dominion Energy Nuclear Connecticut
References
EPID L-2023-LLA-0150
Download: ML24088A330 (1)

Text

April 4, 2024 Eric S. Carr Chief Nuclear Officer Dominion Energy Nuclear Connecticut, Inc.

Millstone Power Station Innsbrook Technical Center 5000 Dominion Boulevard Glen Allen, VA 23060-6711

SUBJECT:

MILLSTONE POWER STATION, UNIT NO. 3 REGULATORY AUDIT PLAN IN SUPPORT OF LICENSE AMENDMENT REQUEST TO IMPLEMENT FRAMATOME GAIA FUEL (EPID L-2023-LLA-0150)

Dear Eric Carr:

By letter dated October 30, 2023 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML23304A047), Dominion Energy Nuclear Connecticut, Inc. (the licensee) submitted a license amendment request to revise the technical specifications (TSs) for Millstone Power Station, Unit No. 3 (MPS3).

The proposed amendment would revise the MPS3 TSs to support the implementation of Framatome GAIA fuel which is currently scheduled for onload during the spring 2025 refueling outage. The proposed TS changes include updating the reactor core safety limits (TS 2.1.1.2),

reducing the Reactor Trip System Instrumentation Trip Setpoint for the P-8 Interlock (TS Table 2.2-1, Item 18.c), and adding to the list of approved methodologies for the Core Operating Limits Report (TS 6.9.1.6.b). Additionally, the licensee requests approval of the following items to support the use of GAIA fuel at MPS3: (1) the design basis limits for a fission product barrier associated with MPS3-specific application of certain methodologies (DOM-NAF-2-P-A, Appendix F, VEP-NE-2-A, and ANP-10338-P-A) and (2) mixed-core penalties for application to departure from nucleate boiling ratio analysis results of MPS3 cores containing both Framatome GAIA fuel and the resident Westinghouse fuel.

The U.S. Nuclear Regulatory Commission (NRC) staff has reviewed the licensees submittal and determined that a regulatory audit would assist in the timely completion of the review. The NRC staff will conduct a regulatory audit to support its review in accordance with the enclosed audit plan. A regulatory audit is a planned activity that includes the examination and evaluation of primarily non-docketed information.

The NRC staff will conduct the audit to increase its understanding of the application and identify information that will require docketing to support the NRC staffs regulatory findings. The NRC staff will conduct the audit virtually from approximately April 30, 2024, through July 12, 2024.

Please contact me at (301) 415-1030 or Richard.Guzman@nrc.gov if you have any questions on this issue.

Sincerely,

/RA/

Richard V. Guzman, Senior Project Manager Plant Licensing Branch I Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-423

Enclosure:

Audit Plan cc: Listserv

Enclosure REGULATORY AUDIT PLAN REGARDING LICENSE AMENDMENT REQUEST TO IMPLEMENT FRAMATOME GAIA FUEL DOMINION ENERGY NUCLEAR CONNECTICUT, INC.

MILLSTONE POWER STATION, UNIT NO. 3 DOCKET NO. 50-423

1.0 BACKGROUND

By letter dated October 30, 2023 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML23304A047), Dominion Energy Nuclear Connecticut, Inc. (the licensee) submitted a license amendment request (LAR) to revise the technical specifications (TSs) for Millstone Power Station, Unit No. 3 (MPS3).

The proposed amendment would revise the MPS3 TSs to support the implementation of Framatome GAIA fuel which is currently scheduled for onload during the spring 2025 refueling outage. The proposed TS changes include updating the reactor core safety limits (TS 2.1.1.2),

reducing the Reactor Trip System Instrumentation Trip Setpoint for the P-8 Interlock (TS Table 2.2-1, Item 18.c), and adding to the list of approved methodologies for the Core Operating Limits Report (TS 6.9.1.6.b). Additionally, the licensee requests approval of the following items to support the use of GAIA fuel at MPS3: (1) the design basis limits for a fission product barrier associated with MPS3-specific application of certain methodologies (DOM-NAF-2-P-A, Appendix F, VEP-NE-2-A, and ANP-10338-P-A) and (2) mixed-core penalties for application to departure from nucleate boiling ratio analysis results of MPS3 cores containing both Framatome GAIA fuel and the resident Westinghouse fuel.

The staff from the Nuclear Regulatory Commissions (NRCs) Office of Nuclear Reactor Regulation (NRR) has initiated its review of the LAR in accordance with NRR Office Instruction LIC-101, License Amendment Review Procedures (ML19248C539).

2.0 REGULATORY AUDIT BASIS A regulatory audit is a planned license or regulation-related activity that includes the examination and evaluation of primarily non-docketed information. The audit is conducted to further identify material the NRC staff may determine is warranted on the docket to support the basis of a licensing or regulatory decision. Performing a regulatory audit is expected to assist the NRC staff in efficiently conducting its review of the LAR and to gain insights on the licensees processes and procedures related to the proposed changes.

The NRC staff will conduct this audit per NRR Office Instruction LIC-111, Regulatory Audits (ML19226A274), with exceptions noted within this audit plan. The NRC staff will perform the audit to support its evaluation of whether the licensees request can be approved per Title 10 of the Code of Federal Regulations (10 CFR), 50.90, Application for amendment of license, construction permit, or early site permit. The NRC staff will use NRR Office Instruction LIC-115, Processing Requests for Additional Information (ML21141A238), to request information needed to make a licensing or regulatory decision.

3.0 REGULATORY AUDIT SCOPE AND METHODOLOGY NRCs goals of the audit are the following:

Gain a better understanding of the detailed calculations, analyses, and bases underlying the LAR and confirm the NRC staffs understanding of the LAR.

Gain a better understanding of plant design features and their implications for the LAR.

Identify questions and requests that may become requests for additional information per NRR Office Instruction LIC-115.

4.0 INFORMATION AND OTHER MATERIAL NECESSARY FOR THE AUDIT The NRC staff will request information and interviews throughout the audit period. The NRC staffs initial audit questions and discussion topics are listed in section 9.0 of this audit plan. The NRCs licensing project manager will email any additional audit questions or requests as supplements to this audit plan so that the licensee can better prepare for audit discussions with NRC staff. The NRC staff requests the licensee to have the requested audit information readily available and accessible for the NRC staffs review via a web-based portal. Any information accessed through the licensees portal will not be held or retained in any way by NRC staff. The NRC staff will schedule audit meetings with the licensee as needed.

5.0 TEAM ASSIGNMENTS The audit team will consist of the following NRC staff.

Richard Guzman, Sr. Project Manager, Plant Licensing Branch 1 Summer Sun, Sr.Nuclear Engineer, Nuclear Systems Performance Branch Joshua Kaizer, Sr. Nuclear Engineer, Nuclear Methods and Fuel Analysis Branch Noushin Amini, Nuclear Engineer, Nuclear Methods and Fuel Analysis Branch 6.0 LOGISTICS To support the schedule established when the NRC staff accepted the LAR for technical review, audit activities will be performed remotely and virtually using Microsoft Teams, teleconference, and any web-based portals or meeting spaces created by the licensee. NRC information requests and communications with licensee staff will be coordinated through the NRCs licensing project manager.

The audit will occur from approximately April 30, 2024, through July 12, 2024. If requested, the audit team will conduct a telephone conference with the licensee for the purposes of introducing the team, discussing the scope of the audit, and describing the information to be made available on the internet portal. The audit team will also confirm with the licensee if the information made available on the online portal contains any sensitive or proprietary information. The audit team may request that the licensee and its representatives answer any audit team questions during the audit related to information provided on the portal at a mutually agreeable day and time by telephone conference or Microsoft Teams meetings. The NRC will work with the licensee to schedule additional audit meetings to discuss information needs and questions arising from the NRCs review of the audited information.

The NRC staff requests the licensee to have the information referenced in section 9.0 of this audit plan available and accessible for the NRC staffs review via an internet-based portal on or by April 30, 2024. The NRC staff requests that any supplemental information requested be available and accessible for the NRC staffs review within one week of the date of the NRCs notification to the licensee of the new requests. The NRCs licensing project manager will inform the licensee via routine communications when the NRC staff no longer needs access to the portal. The NRC staff requests the licensee to notify the NRCs licensing project manager when an audit item is added to its portal.

The NRC staff does not foresee the need for an onsite visit or in-person discussions between the NRC and licensee staff to discuss information to be provided on the portal at this time.

However, if the need for such a meeting is identified in the future, the audit plan will be revised and the schedule for the audit will be adjusted accordingly. The NRC project manager will coordinate any changes to the audit schedule and location with the licensee.

7.0 SPECIAL REQUESTS The NRC requests access to requested documents and information through a web-based portal that allows the NRC staff to access documents over the Internet. The following conditions associated with the online portal must be maintained while the NRC staff and contractors have access to the online portal:

The online portal will be password-protected. A separate password will be assigned to each member of the NRC staff and NRC contractors participating in the audit.

The online portal will prevent the NRC participants from printing, saving, downloading, or collecting any information directly from the online portal.

Conditions of use of the online portal will be displayed on the login screen and will require acknowledgment by each user.

Username and password information should be provided directly to members of the NRC staff and contractors. The NRC licensing project manager will provide the licensee names and contact information of the NRC staff and contractors participating in the audit. All other communications should be coordinated through the NRC project manager.

8.0 DELIVERABLES The NRC staff will develop any requests for additional information (RAIs), as needed, via NRR Office Instruction LIC-115 and issue such RAIs separately from audit-related correspondence.

The NRC staff will issue an audit summary report prior to completing its review of the LAR.

9.0 AUDIT QUESTIONS A. P-8 Trip Setpoint Section 3.3 of Attachment 1 to the LAR dated October 30, 2023, discusses the determination of the P-8 trip setpoint. It indicates that a deterministic departure from nucleate boiling ratio (DNBR) analysis for a low flow condition consistent with the P-8 interlock logic (loss of a reactor coolant pump (RCP)) was performed to establish the proposed P-8 trip setpoint. The analysis shows that an upper limit of 45 percent power is required to ensure the P-8 setpoint maintains the calculated DNBRs within the acceptable limits for GAIA fuel.

Please provide the following information:

1. Discuss the methods, computer codes, and values of key parameters (such as initial RCP flow, power level, reactor coolant system (RCS) pressure and temperature) used in the determination of the low flow condition consistent with the P-8 interlock logic (loss of an RCP). The discussion should show that the associated low flow condition determination used the NRC-approved methodology and computer codes, and the values of key parameters used for the flow determination would result in a lowest credible flow rate condition with consideration of uncertainties.

2. Discuss and justify that the values of key parameters (including initial reactor power, RCS pressure and temperature, RCS flow rate, axial and radial peaking factors, and power shape) used in the deterministic DNBR analysis would result in a lowest margin to the DNBR safety limits for MPS3 cores with GAIA fuel.

3. Identify the cases at different initial power levels that were analyzed to identify an upper limit of 45 percent power for use to determine the P-8 setpoint.

B. Methodologies and Acceptance Criteria for the Rod Ejection Analysis Section 3.4 of Attachment 1 to the LAR dated October 30, 2023, discusses the methodologies and acceptance criteria for the MPS3 rod ejection analysis (REA). It indicates that the REA analysis for GAIA fuel, using the methodologies in topical report (TR) ANP-10338-P-A, was performed against the acceptance criteria in Regulatory Guide (RG) 1.236. Table 1 on page 8/25 in Attachment 1 to the LAR lists the proposed acceptance criteria for the REA analysis.

Please provide the following information related to the acceptance criteria in Table 1.

1. Row 2 of Table 1 lists the limit in Figure 1 of RG 1.236 as the acceptance criterion for the high-temperature cladding failure threshold. Section 3.1 of RG 1.236 restricts the applicability of the Figure 1 limit to events with prompt critical excursions (i.e., ejected rod worth greater than or equal to $1.00). Provide a discussion to address the compliance with the above restriction for use of the Figure 1 limit.

2. Row 3 of Table 1 lists 1.12 for COBRA-FLX/ORFEO-GAIA (Reference 8, FRM TR, ANP-10341-P-A, Revision 0) as the acceptance criterion for the DNBR design limit. Identify the page and section number in Reference 8 that includes the DNBR design limit of 1.12 and identify the page number in the associated NRC safety evaluation (SE) approving the DNBR design limit.

3. Row 4 of Table 1 lists the limits in Figures 2 and 4 of RG 1.236 as the acceptance criterion for the pellet-cladding mechanical interaction (PCMI) threshold. Section 3.2 of RG 1.236 restricts the applicability of Figures 2 and 4 to recrystallized annealed (RXA) cladding type. Address the compliance with the above restriction for use of Figures 2 and 4 limits.

4. Row 5 of Table 1 lists the limits, less than 4754°F, decreasing linearly by 13.7°F per 10,000 MWD/MTU of burnup; rim melt is precluded, as the acceptance criterion for the fuel centerline melt temperature limits. Discuss the derivation and justify the above proposed acceptance criterion for the fuel melt temperature limits that are specific to REA application.

C. Application of ANP-10338-P-A to GAIA Fuel in MPS3 Cores Section 3.4 of Attachment 1 to the LAR dated October 30, 2023, discusses the application of the REA methodologies in ANP-10338-P-A to GAIA fuel in MPS3. It addresses the compliance with the limitations and conditions (L&C) imposed in the SEs approving the TRs applicable to REA application.

Please provide the following information related to the L&C compliance.

1. Compliance with a L&C of ANP-10342, GAIA Fuel Assembly Mechanical Design In section 3.4 of Attachment 1, the licensee indicates that an L&C of ANP-10342 is applicable to the REA application. The L&C states that the most up-to-date guidance and analytical limits should be considered when demonstrating acceptable performance of GAIA under reactivity-initiated accident conditions and highlights the recently issued REA guidance in RG 1.236. Also, the licensee indicates that the application of the REA methodology is compliant with RG 1.236 and thus, satisfies the L&C.

Section 2.2.1 of RG 1.236 provides guidance for selection of PWR REA initial conditions.

Specific guidance for selection of the initial conditions important to the REA analysis is discussed in sections 2.2.1.1 through 2.2.1.13.

Please provide a discussion to show that the REA analysis for MPS3 cores with GAIA meets each PWR REA initial condition in sections 2.2.1.1 through 2.2.1.13 of RG 1.236.

2. Compliance with L&Cs of the AREVA TR Related to REA Analysis On page 15 of 25 of Attachment 1, the licensee indicates that one deviation was taken from the NRC-approved ARCADIA rod ejection accident (AREA) methodology. The deviation is included in Attachment 4 of the LAR as Proprietary INSERT 1 Discuss the effect of the adopted deviation on the stated methodology and justify that it remains acceptable for REA analysis.

3. Calculated values for MPS3 AREA analysis On page 15 of 25 of Attachment 1, the licensee states that MPS3 AREA analysis results demonstrate margin to the limits for fuel temperature, fuel rim temperature, enthalpy, and enthalpy rise. DNB fuel rod failures are predicted, but the failure total remains within the assumptions of the current REA radiological analysis described in MPS3 FSAR [final safety analysis report] Chapter 15.4.8.

Please provide the values of the calculated peak fuel temperature, fuel rim temperature, enthalpy, and enthalpy rise to show that the values meet the applicable limits for the REA analysis. Also, discuss how the total number of DNB failure rods was calculated and specify the calculated total number of failure rods to show it is less than the number assumed in the current REA radiological analysis described in MPS3 FSAR.

4. REA Overpressure Analysis On page 15 of 25 of Attachment 1, the licensee states that if AREA overpressure analysis were performed, it would produce a reduced pressure response compared to the existing analysis described in the FSAR.

Please provide rationale or analysis to support the quoted statement related to the AREA overpressure response bounded by that in the FSAR.

5. Mixed-Core Application of MPS3 REA Analysis On page 16 of 25 of Attachment 1, the licensee states that the MPS3 REA analysis incorporates a conservative thermal-hydraulic penalty that accommodates mixed-core changes in flow distribution.

Please provide the value of the conservative mixed-core penalty factor, discuss how the value of the conservative penalty factor was determined and justify the use of the value of the penalty factor in the REA analysis.

6. Document of the Results of MPS3 AREA Analysis On page 16 of 25 of Attachment 1, the licensee states that the report summarizing the results of the MPS3 AREA analysis for GAIA fuel are available for USNRC audit.

Please load the subject report to the licensees portal for the NRC staff to audit.

D. Additional Topics for Audit Discussion The NRC staff intends to request the licensee to provide clarification for the following topics during the audit discussions:

DNBR Evaluation methodology and transition core penalty calculations Subchannel code modeling Uncertainty analysis Application of VIPRE-D/ORFEO-GAIA and VIPRE-D/ORFEO-NMGRID CHF code/correlation Monte Carlo calculations

ML24088A330 NRR-106 OFFICE NRR/DORL/LPL1/PM NRR/DORL/LPL1/LA NRR/DSS/SNSB/BC NAME RGuzman KEntz PSahd DATE 3/29/2024 3/29/2024 4/04/2024 OFFICE NRR/DSS/SFNB/BC NRR/DORL/LPL1/BC NRR/DORL/LPL1/PM NAME SKrepel HGonzález RGuzman DATE 3/29/2024 4/03/2024 4/04/2024