ML23249A272
| ML23249A272 | |
| Person / Time | |
|---|---|
| Site: | 99902041 |
| Issue date: | 09/19/2023 |
| From: | Gerond George Licensing Processes Branch |
| To: | Elliott G Framatome |
| Shared Package | |
| ML23249A275 | List: |
| References | |
| EPID L-2023-TOP-00XX | |
| Download: ML23249A272 (1) | |
Text
September 19, 2023 Ms. Gayle Elliott, Director Licensing and Regulatory Affairs Framatome Inc.
3315 Old Forest Road Lynchburg, VA 24501
SUBJECT:
REQUEST FOR U.S. NUCLEAR REGULATORY COMMISSION CONFIRMATION ON THE USE OF PRESSURE LOSS COEFFICIENTS WITHIN THE SCHEME-P SOLUTION METHOD IN THE TOPICAL REPORT ANP-10311P-A, REVISION 1, COBRA-FLX: A CORE THERMAL-HYDRAULIC ANALYSIS CODE (EPID L-2023-TOP-0047)
Dear Ms. Elliott:
By letter dated April 12, 2023 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML23107A128), Framatome, Inc. (Framatome) submitted a request for U.S. Nuclear Regulatory Commission (NRC) Confirmation to the use of pressure loss coefficients (PLCs) within the SCHEME-P solution method in Topical Report (TR)
ANP-10311 P-A, Revision 1, "COBRA-FLX: A Core Thermal-Hydraulic Analysis Code."
The request was focused on Request for Additional Information (RAI) A.1 from the original COBRA-FLX TR stated as follows:
The documentation provided in TR, ANP-10311 P, Revision 0 (Reference 1 of the safety evaluation (SE)) does not fully demonstrate that the two solution methods under review yield the same results, within convergence limits, for the same geometric models and boundary conditions. Since the two methods can be used interchangeably, it is important to verify that they give the same results for the same conditions.
The response to RAI A.1 is stated as follows:
The response demonstrated the consistency of the two solution methods by expanding the original presentation in Section 5.1 of TR ANP-10311 P, Revision 0 (Reference 1) to include comparison of steady-state results from models consisting of 12, 52, 75, and 7083 subchannels. These comparisons verify that the SCHEME-Pressure (P) and pressure velocity (PV)-solution methods yield results to within 0.4 percent for the same boundary conditions and model geometry. Based on the results of the comparisons, AREVA NP Inc.
(AREVA) is adopting the user requirement that hydraulic resistances for spacer grids be positioned at an axial position corresponding to the upper-half of the control volume. This will lead to results that are more consistent between analyses based on the P-and PV-solution methods.
The NRC staff determined that the comparisons provided adequately demonstrate the consistency of the two solution methods, and appropriately illustrate the differences due to the variances in computational mesh definition between the two models. The user requirement for hydraulic resistance locations is particularly appropriate for consistency between the two methods for thermal margin (CHF/DNB) evaluations. The NRC staff has concluded that RAI A.1 has been resolved.
Framatome developed a self-imposed user restriction to ensure that hydraulic resistances or PLCs for spacer grids be positioned at an axial position corresponding to the upper-half of the control volume. However, Framatome believed that this restriction was not needed for the SCHEME-P solution and should only be applied to the PV solution. To ensure that such an interpretation did not result in a change to an approved method, Framatome requested that the NRC examine the issue and either confirm or deny if the NRC believed such a change was covered by the current SE.
The NRC staff examined Framatomes request to clarify that the impact due to PLC placement is limited to PV due to staggered mesh and to clarify the RAI A.1 restriction applies only to PV and have the following feedback.
The RAI was focused on ensuring that the PV and Scheme-P provide the same results.
The RAI response demonstrated that the PV provide the same results as Scheme-P only when the hydraulic resistance for the spacer grids was positioned at an axial position corresponding to the upper-half of the control volume.
The RAI response demonstrated the Scheme-P results were insensitive to the axial position of the control volume in which the spacer grid was applied.
Therefore, the restriction from RAI#1 would only need to be applied to the PV method and would not need to be applied to Scheme-P.
Based on the NRC staffs understanding discussed above, the NRC staff confirmed that Framatomes clarification is not a new conclusion and is consistent with the conclusions of the TRs SE and should be considered covered by that SE.
Please contact Ngola Otto at 301-415-6695 or via e-mail at Ngola.Otto@nrc.gov with any questions you may have regarding this letter.
Sincerely,
/RA/
Gerond A. George, Chief Licensing Projects Branch Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 99902041
ML23249A275 (Package)
ML23249A272 (Letter)
ML23107A128 (Framatome Request)
- via email, **NLO OFFICE NRR/DORL/LLPB/PM NRR/DORL/LLPB/LA NRR/DSS/SFNB/BC OGC**
NAME NOtto DHarrison SKrepel MCarpentier DATE 09/06/2023 09/11/2023 09/11/2023 09/19/2023 OFFICE NRR/DORL/LLPB/BC NRR/DORL/LLPB/PM NAME GGeorge NOtto DATE 09/19/2023 09/19/2023