ML25120A135
| ML25120A135 | |
| Person / Time | |
|---|---|
| Site: | 99902041, PROJ0728 |
| Issue date: | 04/29/2025 |
| From: | Ngola Otto Licensing Processes Branch |
| To: | Elliott G Framatome |
| References | |
| EPID L-2024-TOP-0033, ANP-10358P, Rev 0 | |
| Download: ML25120A135 (1) | |
Text
OFFICIAL USE ONLY - PROPRIETARY INFORMATION 1
OFFICIAL USE ONLY - PROPRIETARY INFORMATION REQUEST FOR ADDITIONAL INFORMATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION FRAMATOME TOPICAL REPORT, ANP-10358P, REVISION 0, INCREASED BURNUP FOR PRESSURIZED WATER REACTORS DOCKET NO. 99902041 EPID L-2024-TOP-0033 ISSUE DATE: 04/29/2025 Regulatory Basis Applicable regulatory requirements and guidance identified by the U.S. Nuclear Regulatory Commission (NRC) staff and relevant to the staffs request for additional information are below:
Fuel Design:
Regulatory requirements and guidance for the design of nuclear fuel are intended to ensure acceptable behavior under normal operation, anticipated transients, and postulated accidents:
General Design Criterion (GDC) 10, in Appendix A to Title 10 of the Code of Federal Regulations (10 CFR) Part 50, requires that the reactor core and associated coolant, control, and protection systems shall be designed with appropriate margin to assure that specified acceptable fuel design limits are not exceeded during any condition of normal operation, including the effects of anticipated operational occurrences.
NUREG-0800, Standard Review Plan for the Review of Safety Analysis Reports for Nuclear Power Plants: LWR Edition (SRP) Section 4.2, Fuel System Design, provides review guidance to the NRC staff concerning the establishment of specified acceptable fuel design limits to assure:
the fuel system is not damaged as a result of normal operation and anticipated operational occurrences fuel system damage is never so severe as to prevent control rod insertion when it is required the number of fuel rod failures is not underestimated for postulated accidents core coolability is maintained Loss-of-Coolant Accidents (LOCAs) :
Significant regulatory requirements pertinent to this review for LOCAs include, but are not limited to, the following:
10 CFR 50.46 specifies requirements pertaining to the performance of emergency core cooling systems during a postulated LOCA. While some operating reactors now use fuel designs that do not conform to the specific features listed in the applicability requirements for 10 CFR 50.46 (e.g., use of M5 cladding), regulatory requirements in 10 CFR 50.46 currently remain in effect for all domestic operating power reactors, in some cases through exemptions. Requirements of 10 CFR 50.46 particularly relevant to the current review include the following:
as described in paragraph (a), analytic evaluation models for calculating emergency core cooling system performance must use realistic models with an estimate of the uncertainty in the calculated results or conform to the required and acceptable features described in Appendix K to 10 CFR Part 50.
OFFICIAL USE ONLY - PROPRIETARY INFORMATION 2
OFFICIAL USE ONLY - PROPRIETARY INFORMATION analytic evaluation models must demonstrate conformance to the acceptance criteria described in paragraph (b) for demonstrating adequate emergency core cooling system performance. Among these acceptance criteria, paragraph (b)(4) requires that calculated changes in core geometry shall be such that the core remains amenable to cooling.
GDC 35 establishes minimum requirements for water-cooled nuclear power plants with respect to emergency core cooling. In particular, GDC 35 requires abundant core cooling capable of transferring heat from the reactor core following any loss of reactor coolant, such that fuel and cladding damage that could interfere with continued effective core cooling is prevented and cladding metal-water reaction is limited to negligible amounts.
GDC 35 further incorporates design requirements for emergency core cooling systems, addressing redundancy, leak detection and isolation, and functionality both with and without offsite power.
Appendix K to 10 CFR Part 50 consists of two parts, the first of which specifies required and acceptable features of LOCA evaluation models, and the second of which specifies documentation required for LOCA evaluation models. Appendix K incorporates requirements for modeling significant physical phenomena throughout all phases of the LOCA event, including relevant heat sources, fuel rod performance, and thermal-hydraulic behavior.
In addition to these regulatory requirements, the regulatory guidance applicable to LOCA includes the following:
SRP Section 15.6.5, Loss-of-Coolant Accidents Resulting from Spectrum of Postulated Piping Breaks within the Reactor Coolant Pressure Boundary, provides guidance to support the NRC staffs review of LOCA analyses.
Regulatory Guide (RG) 1.157, Best-Estimate Calculations of Emergency Core Cooling System Performance, provides guidance concerning realistic modeling of the LOCA with explicit accounting for relevant uncertainties.
SRP Section 15.0.2, Review of Transient and Accident Analysis Methods, provides guidance to support the NRC staffs review of analytical evaluation models used to perform safety analyses for nuclear reactors.
RG 1.203, Transient and Accident Analysis Methods, provides regulatory guidance to licensees and applicants concerning the development and assessment of evaluation models used to perform safety analyses for nuclear reactors.
Question 1 Q12 and M5 Growth Section 5.1.2.6, Q12 Growth Correlations, of Topical Report, ANP-10358P, Revision 0, discusses the fuel assembly and grid growth correlations used for Q12 and M5. Supporting data for these correlations have a ((
))
The NRC staff request that Framatome discuss potential breakaway growth behavior of Q12 assemblies and discuss whether the upper design limit (UDL) would cover potential breakaway trends assembly growth. Discuss the margins for the design limit of the Q12/M5 grid growth model. Specifically, discuss the margins ((
))).
OFFICIAL USE ONLY - PROPRIETARY INFORMATION 3
OFFICIAL USE ONLY - PROPRIETARY INFORMATION Question 2 M5 Hydride Reorientation Section 5.2.1.1, Radial Hydride Reorientation, of Topical Report, ANP-10358P, Revision 0, discusses radial hydride reorientation in M5 cladding. The detailed analysis performed to support the rod internal pressure limit is not provided in the Topical Report.
Therefore, the NRC staff requests that Framatome describe the stress analysis performed to determine the rod internal pressure limit that ensures that cladding stresses remain below the M5 hydride reorientation threshold, including detailed results and relevant figures.
Question 3
((
))
In Section B.4.1.3.3 of the Topical Report, the term ((
)) is used to describe one of the configurations analyzed for ((
)), but this term is not defined. Therefore, the NRC staff request that Framatome provide the definition of ((
)) as discussed in Section B.4.1.3.3, ((
)) of Topical Report, ANP-10358P, Revision 0. Include schematics describing the configurations analyzed.
Question 4 Least Transient Oxidation Margin Analysis Section 7.2, Cladding Embrittlement Research, of Topical Report, ANP-10358P, Revision 0, introduces an alternative oxidation figure of merit (FOM) called the least transient oxidation margin (LTOM). This FOM is also discussed in Appendix C, 10 CFR 50.46 Compliance Demonstration Sample Problems, of Topical Report, ANP-10358P, Revision 0. However, the information provided in the Topical Report is insufficient for the NRC staff to gain a full understanding of how LTOM is calculated and used.
Therefore, the NRC staff request that Framatome provide a detailed example of a 10 CFR 50.46, Acceptance Criteria for Emergency Core Cooling Systems for Light-water Nuclear Power Reactors, compliance analysis for the Realistic Large Break LOCA (RLBLOCA) and Small Break LOCA (SBLOCA) cases. Also, include a detailed description of how the LTOM is calculated; a description of the applicable criteria and limits; figures that graphically illustrate the criteria, the metrics, and the margins; and a comparison of maximum local oxidation margin versus LTOM.
Question 5
((
))
Section C.3, Fuel Dispersal, of Topical Report, ANP-10358P, Revision 0 provides an illustrative example of the fuel dispersal analysis. The NRC staff found that some details are missing to fully understand and evaluate the merits of the proposed approach.
Therefore, the NRC staff request that Framatome provide a more detailed example for the
((
)) analysis. Describe all the steps in calculating the relevant metrics.
Provide detailed descriptions of the ((
)) used in the analysis, including equations. Provide examples of ((
OFFICIAL USE ONLY - PROPRIETARY INFORMATION 4
OFFICIAL USE ONLY - PROPRIETARY INFORMATION
))
and discuss possible scenarios.
Question 6
((
)) Calculation Sections B.2, LOCA, and B.3, ((
)) of Topical Report, ANP-10358P, Revision 0, describe the ((
)). The NRC staff found that some details are missing to fully understand and evaluate the merits of the proposed approach.
Therefore, the NRC staff request that Framatome provide a detailed explanation for the
((
)) calculation, including relevant equations and a discussion of their basis. Provide justification for the ((
)) assumptions used (e.g., ((
))). Also, provide a discussion of
((
)). Discuss the impact of ((
)).
Question 7
((
))
Section B.3.1, ((
)) of Topical Report, ANP-10358P, Revision 0, discusses
((
)). The NRC staff needs more information about this process to assess its validity within the context of the ((
)) analysis.
Therefore, the NRC staff request that Framatome provide a detailed discussion of the ((
)) approach. Explain why ((
)) is appropriate, as opposed to ((
)). Discuss any benefits or conservatisms associated with the chosen approach. Also, provide a simple illustrative example.
Question 8
((
))
Section B.4.2.1 of Topical Report, ANP-10358P, ((
)), discusses the characterization of ((
)). In particular, Section B.4.2.1 indicates that realistic evaluation models, such as Framatomes RLBLOCA, ((
)).
The assertion that the ((
)) is an important component to Framatomes approach of demonstrating ((
)). In audit discussions between NRC staff and Framatome staff conducted from March 24, 2025, through March 27, 2025, Framatome indicated that ((
)).
Therefore, the NRC staff requests that Framatome provide a sample analysis that shows the impact of using the ((
)). Also,
OFFICIAL USE ONLY - PROPRIETARY INFORMATION 5
OFFICIAL USE ONLY - PROPRIETARY INFORMATION discuss details of how the sensitivity study was performed, including how sampling was implemented to account for changes in ((
)). Discuss conservatisms for the chosen ((
)).
Question 9
((
))
Section B.4.1.3.2, ((
)) of Topical Report, ANP-10358P, Revision 0, discusses
((
)). In audit discussions between NRC staff and Framatome staff conducted from March 24, 2025, through March 27, 2025, Framatome provided additional information about ((
)).
Therefore, the NRC staff request that Framatome provide a detailed discussion of the potential impact of ((
)). Also, discuss ((
)) and other relevant phenomena along with their approximate magnitude and timing. Provide schematics and any quantitative or qualitative information to support the discussion, as necessary.
Question 10
((
))
Section B.3.4, ((
)), of Topical Report, ANP-10358P, Revision 0 discusses
((
)). To gain better understanding of how ((
)) was performed for this analysis, the NRC staff requests that Framatome provide more information about how the ((
)) were determined, how they relate to ((
)), and discuss potential conservatisms.
Additionally, the NRC staff requests that Framatome discuss how ((
)). Include the ((
)). Discuss ((
)). Clarify whether the new ((
))
Question 11
((
))
Section 7.3.3.2, ((
)), of Topical Report, ANP-10358P, Revision 0, discusses
((
)). The discussion of thresholds for making various ((
)) is not clear to the NRC staff. Therefore, the NRC staff requests that Framatome summarize the ((
)) adjustments made in this topical report.
Specifically, provide clarification on ((
)), and on the ((
ML25120A135 OFFICE NRR/DORL/LLPB/PM NRR/DORL/LLPB/(A)BC NRR/DSS/SFNB/BC NAME NOtto JRankin SKrepel DATE 04/29/2025 04/28/2025 04/22/2025