ML25343A261
| ML25343A261 | |
| Person / Time | |
|---|---|
| Site: | 99902041 |
| Issue date: | 12/16/2025 |
| From: | Ngola Otto Licensing Processes Branch |
| To: | |
| References | |
| EPID L-2025-TOP-0013 RAI 11050, TP BAW-10247 | |
| Download: ML25343A261 (0) | |
Text
OFFICIAL USE ONLY - PROPRIETARY INFORMATION OFFICIAL USE ONLY - PROPRIETARY INFORMATION REQUEST FOR ADDITIONAL INFORMATION-11050 BY THE NUCLEAR REGULATORY COMMISSION OFFICE OF NUCLEAR REACTOR REGULATION TOPICAL REPORT, BAW-10247, REVISION 0, SUPPLEMENT 3P, REVISION 0, REALISTIC THERMAL-MECHANICAL FUEL ROD METHODOLOGY FOR BOILING WATER REACTORS SUPPLEMENT 3: EXTENSION TO HIGHER EXPOSURES FRAMATOME, INC.
EPID L-2025-TOP-0013 DOCKET NO. 99902041 ISSUE DATE: 12/16/2025
=
Background===
By letter dated April 4, 2025 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML25094A181), Framatome, Inc. (Framatome) submitted topical report (TR) BAW-10247, Revision 0, Supplement 3, Revision 0, Realistic Thermal-Mechanical Fuel Rod Methodology for Boiling Water Reactors Supplement 3: Extension to Higher Exposures (ADAMS Package Accession No. ML25094A177), to the U.S. Nuclear Regulatory Commission (NRC) for review and approval for licensing applications. Upon review of the submittal and completion of the regulatory audit that was conducted on September 9-11, 2025, the NRC staff has determined that request for additional information (RAI)-11050 is necessary to continue the review. The RAIs questions are provided below.
Regulatory Basis The fuel system consists of arrays of fuel rods, including fuel pellets and tubular cladding, spacer grids, end plates, and reactivity control rods. The objectives of the fuel system safety review are to provide assurance that (1) the fuel system is not damaged as a result of normal operation and anticipated operational occurrences (AOOs), (2) fuel system damage is never so severe as to prevent control rod insertion when it is required, (3) the number of fuel rod failures is not underestimated for postulated accidents, and (4) coolability is always maintained. The NRC staff acceptance criteria are based on the NUREG-0800, Standard Review Plan (SRP),
Section 4.2, "Fuel System Design." These criteria include three parts: (1) design bases that describe specified acceptable fuel design limits as depicted in General Design Criterion 10 to Appendix A of Title 10 of the Code of Federal Regulations (10 CFR) Part 50, (2) design evaluation that demonstrates that the design bases are met, and (3) testing, inspection, and surveillance plans that show that there are adequate monitoring and surveillance of irradiated fuel. The design bases include fuel system damage, fuel rod failure, and fuel coolability. Fuel performance codes provide analytical evaluation to verify design bases and criteria.
Question 1 Framatome provided detailed Fission Gas Release (FGR) modeling information and comparison to high burnup data in Section 3.1.2, "G4-Fission Gas Release," of TR BAW-10247, Revision 0, Supplement 3. Rod internal pressure is proportional to FGR by the ideal gas law, which suggests that the rod internal pressure (RIP) model should continue to be acceptable for use at higher burnup. However, the RIP model is not qualified at the higher level of burnup requested within this supplement, and ample justification for the continued applicability of the RIP model into the burnup range requested is not provided within the TR.
OFFICIAL USE ONLY - PROPRIETARY INFORMATION OFFICIAL USE ONLY - PROPRIETARY INFORMATION The NRC staff requests that Framatome provide figures showing calculated vs measured RIP and RIP calculated vs measured vs burnup. Additionally, provide justification via analysis and/or comparison to data at higher burnup levels showing that the RIP model is applicable for use at the higher burnup requested without additional validation.
Question 2 Framatome provided within Figure 3-6, "Exposure Range for Cr-doped Fission Gas Release Dataset," of TR BAW-10247, Revision 0, Supplement 3, a dataset of FGR for Chromia (Cr) doped fuel at higher burnup which indicates that higher burnup datapoints were used to calibrate RODEX4. However, this dataset does not demonstrate RODEX4s predictive capabilities of FGR for Cr doped fuel at the burnup range requested, as only the measured quantity of FGR is shown. Framatome provided multiple figures in its response to RAI 8b within ANP-10340Q1P, Revision 0 (ADAMS Package Accession No. ML18171A107) demonstrating RODEX4s ability to predict Cr doped fuel FGR at a comparable level to non-doped. Similarly, the figures within the response did not adequately demonstrate RODEX4s capability to accurately and reliably predict Cr doped fuel FGR at the higher burnup range requested for approval within Supplement 3.
Therefore, the NRC staff requests that Framatome provide a figure that shows RODEX4s performance against FGR data for Cr doped fuel. For example, generating a figure similar to Figure 3-3, "High Exposure Dataset, Calculated and Measured Fission Gas Release Values,"
plotting the Cr doped dataset provided within Figure 3-6 alongside RODEX4s predictions.
Question 3 Section 5.3, "Extension of NAF RPP Correlations for Higher Enrichments," of TR BAW-10247, Revision 0, Supplement 3, indicates the existing radial power profile (RPP) tables in RODEX4 have an upper bound enrichment of 5 weight percent (wt%) uranium (U)-235 for both gadolinia and non-gadolinia fuel. The RPP entries in these tables were derived for specific combinations of relevant parameters by using ((
)) to process RPP values that were generated via
((
)) for a wide range of parameters. Section 5.3 of the TR also indicates that the updated version of ((
)), was used to extend the enrichment range of non-gadolinia fuel to 10 wt% U-235 and that the extension of gadolinia tables above 5 wt%
U-235 followed the same procedure used in GALILEO. Based on the TR submittal, it is not clear to the NRC staff how RODEX4 processes the transition from one range of U-235 enrichment generated from one code to another range generated by another code. Additionally, in a regulatory audit conducted from September 9, 2025, to September 11, 2025 (ADAMS Package Accession No. ML25212A128), Framatome indicated RPPs for higher enrichments were developed using ((
)).
The NRC staff requests that Framatome provide discussions detailing the manner in which the RPPs were generated using ((
)) and the relationship between these RPPs and the RPP tables used in the version of RODEX4 for which NRC-approval is being sought (e.g., are the ((
)) RPPs processed by ((
)) to generate the updated RODEX4 RPP tables)? Additionally, please clearly identify which enrichment ranges of RPPs are attributed to which code and discuss how RODEX4 processes the transition from one range to another. Lastly, please provide an example RPP plot of power density versus pellet radius from APOLLO2-A.
OFFICIAL USE ONLY - PROPRIETARY INFORMATION OFFICIAL USE ONLY - PROPRIETARY INFORMATION Question 4 As stated in Section 6.1, "Dimensional Change," and Appendix B, "BWR Fuel Rod to Fuel Assembly Differential Growth Correlation," of TR BAW-10247, Revision 0, Supplement 3, the RODEX4 methodology for fuel rod growth has been revised to a differential fuel rod to fuel assembly growth model to evaluate the limiting end of life (EOL) margin. The burnup range of the fuel rod growth data shown in Figure B-2, "BWR Fuel Rod Growth Correlation for SRA Cladding," ((
)). Framatome asserts NUREG-1475, Revision 1, Applying Statistics, was used in the extrapolation of these values to the burnup range requested. However, the statistical procedure used from NUREG-1475, Revision 1, within the TR is not entirely clear to the NRC staff. The statistical procedure used to develop the ((
)) was described in more detail during the regulatory audit conducted from September 9, 2025, to September 11, 2025 (ADAMS Package Accession No. ML25212A128).
Therefore, the NRC staff requests that Framatome provide a discussion describing how the
((
)) is applied within the fuel rod and fuel assembly growth model. Additionally, provide justification for extrapolating fuel rod/fuel assembly differential growth to higher burnup.
Question 5 Line A.V of Table 2-1, "Standard Review Plan Section 4.2 Criteria," of TR BAW-10247, Revision 0, Supplement 3 states that the previously approved channel bow method (TR BAW-10247Q3(P), Appendix B (ADAMS Package Accession No. ML081340220)) ((
)) However, no justification is provided within the TR to support this assertion.
Additionally, while BAW-10247Q3(P), Appendix B, provides a discussion on the determination of ((
)) no discussion is provided in BAW-10247Q3(P), Appendix B, or the current TR regarding the applicability of the approach for ((
)) or assurances that the resulting ((
)) will yield results that remain within the approved ((
)) of RODEX4.
The NRC staff requests that Framatome provide justification that the previously approved channel bow method discussed in BAW-10247Q3(P), Appendix B, ((
)) for RODEX4.
Additionally, provide justification ((
)) currently approved for RODEX4 as specified in Section B.7 of BAW-10247Q3(P),
Appendix B.
Question 6 In Section 3.2.2, "G6-Cladding Mechanical Properties," of TR BAW-10247, Revision 0, Supplement 3, Framatome provides Figures 3-9, "Mechanical Testing on Irradiated Cladding,"
and 3-10, "Burst Strains for Irradiated Cladding, Hydrogen < 500 PPM." These figures
OFFICIAL USE ONLY - PROPRIETARY INFORMATION OFFICIAL USE ONLY - PROPRIETARY INFORMATION encompass data from various mechanical tests which respectively demonstrate that the irradiation hardening of fuel rod cladding saturates around the midlife of fuel rods, and that the irradiated cladding continues to satisfy the one percent uniform strain licensing criterion under the effects of hydrogen and irradiation embrittlement through EOL. Framatome asserts that these conclusions from the mechanical tests indicate that RODEX4 can calculate stress and strain at higher burnup levels. The figures provided are comprised strictly of datasets, which do demonstrate Framatomes claim that the mechanical parameters remain consistent while approaching EOL, but no predictive capability of RODEX4 is shown. Because only data is provided, the figures do not adequately demonstrate RODEX4s ability to adequately capture the saturation effect shown in the data, and in turn, accurately and reliably predict the mechanical parameters at higher burnup.
Therefore, the NRC staff requests that Framatome provide a comparison of RODEX4s calculations of yield stress and plastic strain over the range of fast neutron fluence to the datasets shown in Figures 3-9 and 3-10 (i.e., a calculated vs measured plot vs fluence for what is shown in Figures 3.9 and 3.10).
ADAMS Accession Nos.:
ML25343A262 (Package)
ML25343A263 (RAI Question - Proprietary)
ML25343A261 (RAI Question - Non-Proprietary) *via eRAI Application **via eConcurrence OFFICE NRR/DSS/SFNB/BC*
NRR/DORL/LLPB/PM*
NRR/DORL/LLPB/BC* (A)
NAME SKrepel NOtto MMarshall DATE 12/4/2025 12/8/2025 12/10/2025 OFFICE NRR/DORL/LLPB/LA** NRR/DORL/LLPB/PM**
NAME DHarrison NOtto DATE 12/11/2025 12/11/2025