ML24353A218

LLC, Response to NRC Request for Additional Information No. 037 (RAI-10357 R1) on the NuScale Standard Design Approval Application

ML24353A218
Person / Time
Site:	05200050
Issue date:	12/18/2024
From:	Shaver M NuScale
To:	Office of Nuclear Reactor Regulation, Document Control Desk
Shared Package
ML24353A217	List: ML24353A218
References
RAIO-177389
Download: ML24353A218 (1)

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RAIO-177389 NuScale Power, LLC 1100 NE Circle Blvd., Suite 200 Corvallis, Oregon 97330 Office 541.360.0500 Fax 541.207.3928 www.nuscalepower.com December 18, 2024 Docket No.52-050 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk One White Flint North 11555 Rockville Pike Rockville, MD 20852-2738

SUBJECT:

NuScale Power, LLC Response to NRC Request for Additional Information No. 037 (RAI-10357 R1) on the NuScale Standard Design Approval Application

REFERENCE:

NRC Letter to NuScale, Request for Additional Information No. 037 (RAI-10357 R1), dated October 17, 2024 The purpose of this letter is to provide the NuScale Power, LLC (NuScale) response to the referenced NRC Request for Additional Information (RAI).

The enclosure to this letter contains the NuScale response to the following RAI question from NRC RAI-10357 R1:

15.0.5-6 is the proprietary version of the NuScale Response to NRC RAI No. 037 (RAI-10357 R1, Question 15.0.5-6). NuScale requests that the proprietary version be withheld from public disclosure in accordance with the requirements of 10 CFR § 2.390. The enclosed affidavit (Enclosure 3) supports this request. Enclosure 2 is the nonproprietary version of the NuScale response.

This letter makes no regulatory commitments and no revisions to any existing regulatory commitments.

If you have any questions, please contact Amanda Bode at 541-452-7971 or at abode@nuscalepower.com.

I declare under penalty of perjury that the foregoing is true and correct. Executed on December 18, 2024.

Sincerely, Mark W. Shaver Director, Regulatory Affairs NuScale Power, LLC

RAIO-177389 Page 2 of 2 12/18/2024 NuScale Power, LLC 1100 NE Circle Blvd., Suite 200 Corvallis, Oregon 97330 Office 541.360.0500 Fax 541.207.3928 www.nuscalepower.com Distribution:

Mahmoud Jardaneh, Chief New Reactor Licensing Branch, NRC Getachew Tesfaye, Senior Project Manager, NRC Stacy Joseph, Senior Project Manager, NRC

NuScale Response to NRC Request for Additional Information RAI-10357 R1, Question 15.0.5-6, Proprietary Version : NuScale Response to NRC Request for Additional Information RAI-10357 R1, Question 15.0.5-6, Nonproprietary Version : Affidavit of Mark W. Shaver, AF-177390

RAIO-177389 NuScale Power, LLC 1100 NE Circle Blvd., Suite 200 Corvallis, Oregon 97330 Office 541.360.0500 Fax 541.207.3928 www.nuscalepower.com NuScale Response to NRC Request for Additional Information RAI-10357 R1, Question 15.0.5-6, Proprietary Version

RAIO-177389 NuScale Power, LLC 1100 NE Circle Blvd., Suite 200 Corvallis, Oregon 97330 Office 541.360.0500 Fax 541.207.3928 www.nuscalepower.com NuScale Response to NRC Request for Additional Information RAI-10357 R1, Question 15.0.5-6, Nonproprietary Version

Response to Request for Additional Information Docket: 052000050 RAI No.: 10357 Date of RAI Issue: 10/17/2024 NRC Question No.: 15.0.5-6 Issue FSAR Section 15.0.5 is missing the results from the lower riser hole flow evaluation calculations, as required by the XPC topical report methodology, that shows that the flow rates used in the boron transport analysis are justified. The results are needed to show that the applicable regulations identified by NuScale in the XPC topical report are met when the methodology is applied to the NPM-20 design. The calculation results from the application of the topical report methodology to a particular design is within the scope of an FSAR and is not considered proprietary similar to the results of the application of other topical report methodologies. The results from the lower riser hole flow evaluation calculations are used in the boron transport either directly as stated in the XPC topical report methodology or as an input based on its results. The XPC topical report methodology states This section provides an acceptable approach for evaluation of riser hole flow rates for use in boron transport analyses, or for justification of use of rates determined from a different source. During the audit, the staff observed that the NuScale calculation that appears to contain the lower riser hole flow evaluation calculations states that (( 2(a),(c) The results from the lower riser hole flow evaluation calculations are required to perform the boron transport safety analysis and therefore must be verified per 10 CFR 50 Appendix B. Information Requested Revise FSAR Section 15.0.5 to present the results of the lower riser hole flow evaluation calculations. These results need to be calculated following the XPC topical report methodology and show that the flow rates used in the boron transport analysis are appropriate. The lower riser hole flow evaluation calculation results need to be verified by NuScale in accordance with 10 CFR 50 Appendix B given the calculations are used in the boron transport analyses either directly as stated in the XPC topical report methodology or as an input based on its results. NuScale Nonproprietary NuScale Nonproprietary

NuScale Response: The issue portion of the Request for Additional Information (RAI) states, in part (emphasis added): The lower riser hole flow evaluation calculation results need to be verified by NuScale in accordance with 10 CFR 50 Appendix B given the calculations are used in the boron transport analyses either directly as stated in the XPC topical report methodology or as an input based on its results. This portion of the RAI implies that NRC staff believe that any input to a safety-related calculation must come from a calculation or other engineering document verified in accordance with 10 CFR 50 Appendix B. This belief implies that any input to a safety-related calculation must come from a document also classified as safety-related. The identified assertion is not consistent with NuScales internal policies and procedures that govern the implementation of NuScales design control program, which the NRC staff reviewed to verify compliance with the requirements of Criterion III, Design Control of Appendix B to 10 CFR Part 50. The NRC staff concluded that NuScale is implementing its design control program in accordance with the regulatory requirements of Criterion III of Appendix B to 10 CFR Part 50 as documented in the NRC Inspection Report dated April 12, 2024 (ADAMS Accession No. ML24099A129). Additionally, this assertion appears illogical, particularly for system thermal-hydraulic analysis where safety-related and nonsafety-related components are modeled. An analogy can be made for a feedwater pump curve. A design may specify a limiting feedwater pump curve that is used, for example, as a design input to an increase in feedwater flow event safety analysis. The feedwater pump does not perform any safety-related functions in the design. A limiting feedwater pump curve is input to the safety analysis to assure the design is bounded. Analyses would demonstrate that the feedwater pump curve for the pump design selected for the plant, or installed at the plant, remains below the limit that is input in the safety analysis, and as such the pump design meets one of its requirements. The RAI text implies that such analyses would need to be classified as safety-related, simply because they confirm a bounding input used in a safety analysis and unrelated to any function performed by the component. For the boron transport results presented in Final Safety Analysis Report (FSAR) Section 15.0, Transient and Accident Analyses, NuScale chose to confirm that the riser hole flow rates predicted by NRELAP5 were conservative for use by performing a confirmation assessment, NuScale Nonproprietary NuScale Nonproprietary

(lower riser hole flow assessment). The lower riser hole flow assessment was performed following the approach described in TR-124587, Revision 0, Extended Passive Cooling and Reactivity Control Methodology, Section 5.2.3. The results of the lower riser hole flow assessment are used to demonstrate the adequacy of the NRELAP lower riser hole flow rates and the NRELAP lower riser hole flow rates (not the lower riser hole flow assessment) are used as design input to generate the boron transport analysis results presented in FSAR Section 15.0. In order to drive closure of this RAI, the results of the lower riser hole flow assessment are integrated into an engineering document that is classified as safety-related. The safety-related engineering document is currently in revision to include the above mentioned information and the lower riser hole evaluation results are required to be verified in accordance with the applicable requirements of MN-122626-P, Revision 0, NuScale LLC Quality Assurance Program Description, Section 2.3.1, Design Verification, which complies with Appendix B to 10 CFR Part 50. Consistent with the information requested in this RAI, FSAR Section 15.0.5, Extended Passive Cooling for Decay and Residual Heat Removal, is revised to include the results of the previously described lower riser hole flow assessment. The lower riser hole flow assessment concludes that the lower riser hole flow rates calculated by NRELAP5 are acceptable for use in the extended passive cooling boron transport analysis. Impact on US460 SDAA: FSAR Section 15.0 has been revised as described in the response above and as shown in the markup provided in this response. NuScale Nonproprietary NuScale Nonproprietary

NuScale Final Safety Analysis Report Transient and Accident Analyses NuScale US460 SDAA 15.0-38 Draft Revision 2 Audit Item A-15.0.5-1, Audit Item A-15.0.5-2 ESB parameters used in the boron transport analysis are selected to provide conservative calculations. These parameters include: high-biased mixing tube minor form losses, and nominal inner surface roughness mixing tube length conservatively modeled longer than actual design length mixing tube inlet elevation conservatively modeled lower than actual design elevation mixing tube outlet elevation conservatively modeled higher than actual design elevation Audit Item A-15.0.5-1 boron oxide pellets conservatively modeled as equilateral cylinders with 3/8 in. diameter, which is larger than the actual design diameter, for cases with slow-biased boron dissolution from the ESB Audit Item A-15.0.5-1, Audit Item A-15.0.5-2 The condensate flow into the ESB dissolvers and containment mixing tubes, which is generated by the effective minimum CNV wall condensation area, is modeled in the boron transport and precipitation analyses as described in Reference 15.0-8. The temperature of the ESB condensate is modeled at the saturation temperature of the CNV vapor pressure. Audit Item A-15.0.5-1, Audit Item A-15.0.5-2 RAI 15.0.5-1, RAI 15.0.5-6 Lower riser hole flow rates calculated by NRELAP5 are assessed as described in Reference 15.0-8 and. RAI 15.0.5-1, RAI 15.0.5-6 Results from low RPV pressure cases show that NRELAP5 calculates lower values of riser hole flow and is therefore more conservative than the alternate assessment calculation. NRELAP5 calculates a wide range of flow values, ranging from 0.1 kg/s to 6 kg/s. In contrast, the alternate assessment calculation range is relatively small, from 7 kg/s to 10.6 kg/s. Generally at lower pressures the long term cooling NRELAP5 model shows flow oscillations in the liquid space which tends to distribute the core thermal energy in both the forward and reverse directions as opposed to the alternate assessment calculation solution which assumes a forward flow heat balance energy solution. RAI 15.0.5-1, RAI 15.0.5-6 Results from high RPV pressure cases, with nominal loss coefficients, show that the alternate assessment calculation value is equal to or higher than the NRELAP5 value, implying that the NRELAP5 value is conservative. The NRELAP5 cases apply the nominal loss coefficient.

NuScale Final Safety Analysis Report Transient and Accident Analyses NuScale US460 SDAA 15.0-39 Draft Revision 2 Audit Item A-15.0.5-1, Audit Item A-15.0.5-2 RAI 15.0.5-1, RAI 15.0.5-6 The lower riser hole flow rates calculated by NRELAP5 are determined to be acceptable for use in the boron transport and precipitation analyses because the use of the average riser hole flow from NRELAP5 increases the difference between the calculated core and downcomer boron concentrations during ECCS cooling. With this conservatively biased riser hole flow, the limiting boron transport analysis results demonstrate that the boron concentration in the RPV remains above the critical concentration. The parameters used for modeling riser holes in the extended passive cooling analyses include: RAI 15.0.5-1, RAI 15.0.5-6 total lower riser hole flow area of 7.07 sq in. with forward loss coefficient of 2.8 and reverse loss coefficient of 2.8. RAI 15.0.5-1, RAI 15.0.5-6 grouped upper riser hole flow area of 12 sq in. at each of the four upper riser hole elevations with forward loss coefficient of 5.75 and reverse loss coefficient of 4.75. elevation of riser holes groups are distributed to match the design within constraints of model nodalization forward and reverse losses are considered Audit Item A-15.0.5-1, Audit Item A-15.0.5-2 The result for the limiting cases for the boron transport analysis are given in Table 15.0-18. Results for beginning of cycle (BOC) and middle of cycle (MOC) are also given for the injection line break for comparison. Figures 15.0-5 through Figure 15.0-10 show the boron concentrations and boron masses in the RPV and CNV for the limiting cases. The methodology for calculating boron transport is presented in Reference 15.0-8; calculation of the critical boron concentration accounts for the highest-worth control rod assembly remaining stuck out of the core. Audit Item A-15.0.5-1, Audit Item A-15.0.5-2 The margin to boron precipitation limits is evaluated. Key input parameters and initial conditions used in the limiting boron precipitation case are provided in Table 15.0-22. Audit Item A-15.0.5-1, Audit Item A-15.0.5-2 The minimum difference between core or downcomer concentration and the precipitation limit is recorded along with the time of the minimum in Table 15.0-19. The limiting event is the 100 percent high point vent line outside the CNV. Figure 15.0-11 and Figure 15.0-12 show the boron concentrations and boron masses in the RPV and CNV for the limiting case. The break outside the CNV reduces RCS inventory available for ECCS cooldown, however, margin to boron precipitation is maintained. The lower riser holes maintain mixing during ECCS operation and boron precipitation is

RAIO-177389 NuScale Power, LLC 1100 NE Circle Blvd., Suite 200 Corvallis, Oregon 97330 Office 541.360.0500 Fax 541.207.3928 www.nuscalepower.com Affidavit of Mark W. Shaver, AF-177390

AF-177390 Page 1 of 2

NuScale Power, LLC AFFIDAVIT of Mark W. Shaver I, Mark W. Shaver, state as follows: (1) I am the Director of Regulatory Affairs of NuScale Power, LLC (NuScale), and as such, I have been specifically delegated the function of reviewing the information described in this Affidavit that NuScale seeks to have withheld from public disclosure, and am authorized to apply for its withholding on behalf of NuScale. (2) I am knowledgeable of the criteria and procedures used by NuScale in designating information as a trade secret, privileged, or as confidential commercial or financial information. This request to withhold information from public disclosure is driven by one or more of the following: (a) The information requested to be withheld reveals distinguishing aspects of a process (or component, structure, tool, method, etc.) whose use by NuScale competitors, without a license from NuScale, would constitute a competitive economic disadvantage to NuScale. (b) The information requested to be withheld consists of supporting data, including test data, relative to a process (or component, structure, tool, method, etc.), and the application of the data secures a competitive economic advantage, as described more fully in paragraph 3 of this Affidavit. (c) Use by a competitor of the information requested to be withheld would reduce the competitors expenditure of resources, or improve its competitive position, in the design, manufacture, shipment, installation, assurance of quality, or licensing of a similar product. (d) The information requested to be withheld reveals cost or price information, production capabilities, budget levels, or commercial strategies of NuScale. (e) The information requested to be withheld consists of patentable ideas. (3) Public disclosure of the information sought to be withheld is likely to cause substantial harm to NuScales competitive position and foreclose or reduce the availability of profit-making opportunities. The accompanying Request for Additional Information response reveals distinguishing aspects about the response by which NuScale develops its NuScale Power, LLC Response to NRC Request for Additional Information (RAI No. 10357 R1, Question 15.0.5-6) on the NuScale Standard Design Approval Application. NuScale has performed significant research and evaluation to develop a basis for this response and has invested significant resources, including the expenditure of a considerable sum of money. The precise financial value of the information is difficult to quantify, but it is a key element of the design basis for a NuScale plant and, therefore, has substantial value to NuScale. If the information were disclosed to the public, NuScales competitors would have access to the information without purchasing the right to use it or having been required to undertake a similar expenditure of resources. Such disclosure would constitute a misappropriation of NuScales intellectual property, and would deprive NuScale of the opportunity to exercise its competitive advantage to seek an adequate return on its investment. (4) The information sought to be withheld is in the enclosed response to NRC Request for Additional Information RAI 10357 R1, Question 15.0.5-6. The enclosure contains the designation Proprietary at the top of each page containing proprietary information. The information considered by NuScale to be proprietary is identified within double braces, (( }} in the document.

AF-177390 Page 2 of 2 (5) The basis for proposing that the information be withheld is that NuScale treats the information as a trade secret, privileged, or as confidential commercial or financial information. NuScale relies upon the exemption from disclosure set forth in the Freedom of Information Act (FOIA), 5 USC § 552(b)(4), as well as exemptions applicable to the NRC under 10 CFR §§ 2.390(a)(4) and 9.17(a)(4). (6) Pursuant to the provisions set forth in 10 CFR § 2.390(b)(4), the following is provided for consideration by the Commission in determining whether the information sought to be withheld from public disclosure should be withheld: (a) The information sought to be withheld is owned and has been held in confidence by NuScale. (b) The information is of a sort customarily held in confidence by NuScale and, to the best of my knowledge and belief, consistently has been held in confidence by NuScale. The procedure for approval of external release of such information typically requires review by the staff manager, project manager, chief technology officer or other equivalent authority, or the manager of the cognizant marketing function (or his delegate), for technical content, competitive effect, and determination of the accuracy of the proprietary designation. Disclosures outside NuScale are limited to regulatory bodies, customers and potential customers and their agents, suppliers, licensees, and others with a legitimate need for the information, and then only in accordance with appropriate regulatory provisions or contractual agreements to maintain confidentiality. (c) The information is being transmitted to and received by the NRC in confidence. (d) No public disclosure of the information has been made, and it is not available in public sources. All disclosures to third parties, including any required transmittals to NRC, have been made, or must be made, pursuant to regulatory provisions or contractual agreements that provide for maintenance of the information in confidence. (e) Public disclosure of the information is likely to cause substantial harm to the competitive position of NuScale, taking into account the value of the information to NuScale, the amount of effort and money expended by NuScale in developing the information, and the difficulty others would have in acquiring or duplicating the information. The information sought to be withheld is part of NuScales technology that provides NuScale with a competitive advantage over other firms in the industry. NuScale has invested significant human and financial capital in developing this technology and NuScale believes it would be difficult for others to duplicate the technology without access to the information sought to be withheld. I declare under penalty of perjury that the foregoing is true and correct. Executed on December 18, 2024. Mark W. Shaver}}