ML24354A252
| ML24354A252 | |
| Person / Time | |
|---|---|
| Site: | 05200050 |
| Issue date: | 12/19/2024 |
| From: | Shaver M NuScale |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| Shared Package | |
| ML24354A251 | List: |
| References | |
| RAIO-177428 | |
| Download: ML24354A252 (1) | |
Text
RAIO-177428 NuScale Power, LLC 1100 NE Circle Blvd., Suite 200 Corvallis, Oregon 97330 Office 541.360.0500 Fax 541.207.3928 www.nuscalepower.com December 19, 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. 032 (RAI-10297 R1) on the NuScale Standard Design Approval Application
REFERENCE:
NRC Letter to NuScale, Request for Additional Information No. 032 (RAI-10297 R1), dated October 31, 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-10297 R1:
NonLOCA.LTR-1 is the proprietary version of the NuScale Response to NRC RAI No. 032 (RAI-10297 R1, Question NonLOCA.LTR-1). 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 1 has also been determined to contain Export Controlled Information. This information must be protected from disclosure per the requirement of 10 CFR § 810. 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 19, 2024.
Sincerely, Mark W. Shaver Director, Regulatory Affairs NuScale Power, LLC
RAIO-177428 Page 2 of 2 12/19/2024 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 Thomas Hayden, Project Manager, NRC
- NuScale Response to NRC Request for Additional Information RAI-10297 R1, Question NonLOCA.LTR-1, Proprietary Version : NuScale Response to NRC Request for Additional Information RAI-10297 R1, Question NonLOCA.LTR-1, Nonproprietary Version : Affidavit of Mark W. Shaver, AF-177435
RAIO-177428 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-10297 R1, Question NonLOCA.LTR-1, Proprietary Version
RAIO-177428 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-10297 R1, Question NonLOCA.LTR-1, Nonproprietary Version
Response to Request for Additional Information Docket: 052000050 RAI No.: 10297 Date of RAI Issue: 10/31/2024 NRC Question No.: NonLOCA.LTR-1 Issue The Non-LOCA methodology does not provide an adequate basis for model validation vs. test data (( 2(a),(c). Riser holes have an impact on thermal hydraulic conditions, for example but not limited to, initial conditions, natural circulation and RCS response; these impacts and any others need to be addressed. Information Requested a) Provide justification via sensitivity studies demonstrating that NRELAP5 can adequately calculate the actual expected NPM response with respect to the integrated topical report model. The total integral response of the Non-LOCA LTR model (from beginning of the event until the end of the period of interest) to various design basis events and conditions should be validated, (( }} 2(a),(c). The potential impact on the RCS response and conditions for the integrated model on the figures of merit calculated by the topical report model and downstream activities should be shown analytically as described below:
- i. Provide sensitivity analyses and evaluations of the impact of riser holes on the integral effects tests responses used for Evaluation Model validation for the Non-LOCA LTR, including the referenced integral effects test responses. The various impacts of riser holes on the integral test validation response should be captured in the impacts on the integrated NRELAP5 evaluation model results for Non-LOCA analyses.
ii. Provide sensitivities and evaluations for the impact of riser holes on the total integral response of the LTR model (Non-LOCA) to various design basis events and conditions that NuScale Nonproprietary NuScale Nonproprietary
show that the test validation response to riser holes is captured. The impact on the RCS response and conditions for the integrated model on the figures of merit calculated by the Non-LOCA LTR model should be shown analytically. b) Revise the LTR to include the above information. NuScale Response: Executive Summary NuScale previously provided information in the response to audit question A-NonLOCA.LTR-1 that demonstrated that ((
}}2(a),(c) riser holes on a NuScale Power Module (NPM) during both steady-state conditions and the short-term transient response to non-loss-of-coolant accident (non-LOCA) events, with focus on post-trip decay heat removal system (DHRS) cooling conditions. NuScale concluded that no further studies of riser holes were warranted (( }}2(a),(c) on non-LOCA events. However, in response to this request for additional information (RAI) specifically requesting additional studies, NuScale provides the results of multiple sensitivity studies focused on the impact of riser holes on the short-term transient response. The sensitivity studies include (( }}2(a),(c) In the sensitivity studies, the riser hole areas are modified
((
}}2(a),(c),ECI The results show that modifying the riser hole areas in NRELAP5 results in (( }}2(a),(c) The impacts of the modifications on figures of merit, (( }}2(a),(c) Therefore, it is concluded that modeling nominal riser hole areas is reasonable (( }}2(a),(c) The conclusion extends to modeling nominal form losses for the flow paths, because the form losses and flow area together characterize the flow path pressure drop. The provided sensitivities are consistent with those requested in this RAI. In addition, TR-0516-49416-P, Revision 4, Non-Loss-of-Coolant Accident Analysis Methodology, is revised as requested in this RAI.
Relevant Information from Previous Audit Question Response NuScale previously provided information regarding riser holes in the response to audit question A-NonLOCA.LTR-1, available in the electronic reading room (eRR) for TR-0516-49416-P. The NuScale Nonproprietary NuScale Nonproprietary
response to the audit question concluded (( }}2(a),(c) Relevant information from the previous audit question response is listed here to provide background and for comparison to new sensitivity results described later in this response. (( }}2(a),(c),ECI NuScale Nonproprietary NuScale Nonproprietary
The previous audit response concluded that NRELAP5 reasonably calculates the small impact of riser holes on an NPM during both steady-state conditions and the short-term transient response to LOCA and non-LOCA events. Additional Riser Hole Geometry Considerations As described in the previous response to audit question A-NonLOCA.LTR-1 and summarized above, ((
}}2(a),(c),ECI the largest allowable increase in lower riser hole flow area is a factor of (( }}2(a),(c),ECI relative to nominal. Similarly, the largest allowable decrease in lower riser hole flow area is a factor of
((
}}2(a),(c),ECI relative to nominal.
As described in the previous response to audit question A-NonLOCA.LTR-1 and summarized above, ((
}}2(a),(c),ECI the largest allowable increase in upper riser hole flow area is a factor of
((
}}2(a),(c),ECI relative to nominal. Similarly, the largest allowable decrease in lower riser hole flow area is a factor of (( }}2(a),(c),ECI relative to nominal.
((
}}2(a),(c),ECI the above estimates of possible increases or decreases in riser hole area are considered bounding.
New Sensitivity Studies Based on the prior discussion, NuScale concluded that no further studies of riser holes were warranted ((
}}2(a),(c) However, to support the response to this RAI question specifically requesting further studies, additional sensitivity studies are performed. Sensitivity studies for the NPM response are performed for the following Final Safety Analysis Report (FSAR) Chapter 15 events: (( }}2(a),(c) In addition, sensitivity studies are performed NuScale Nonproprietary NuScale Nonproprietary
for ((
}}2(a),(c) test assessments. The sensitivity studies, and their results, are provided in the following sections.
Riser Hole Sensitivity Study for ((
}}2(a),(c)
A base case ((
}}2(a),(c) is selected to perform a riser hole sensitivity study. (( }}2(a),(c) Based on the riser hole geometry considerations described above, these sensitivity cases are (( }}2(a),(c),ECI The results of the sensitivity study are shown in Table 1. (( }}2(a),(c)
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Table 1: (( }}2(a),(c) Riser Hole Sensitivity Study (( }}2(a),(c) Transient plots of relevant parameters for the sensitivity study are shown in Figure 1 through Figure 14. ((
}}2(a),(c)
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((
}}2(a),(c)
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Overall, the results of the riser hole sensitivity study (( }}2(a),(c) demonstrate the following: (( }}2(a),(c) NuScale Nonproprietary NuScale Nonproprietary
Figure 1: (( }}2(a),(c) (( }}2(a),(c) NuScale Nonproprietary NuScale Nonproprietary
Figure 2: (( }}2(a),(c) (( }}2(a),(c) NuScale Nonproprietary NuScale Nonproprietary
Figure 3: (( }}2(a),(c) (( }}2(a),(c) NuScale Nonproprietary NuScale Nonproprietary
Figure 4: (( }}2(a),(c) (( }}2(a),(c) NuScale Nonproprietary NuScale Nonproprietary
Figure 4a: (( }}2(a),(c) (( }}2(a),(c) NuScale Nonproprietary NuScale Nonproprietary
Figure 4b: (( }}2(a),(c) (( }}2(a),(c) NuScale Nonproprietary NuScale Nonproprietary
Figure 4c: (( }}2(a),(c) (( }}2(a),(c) NuScale Nonproprietary NuScale Nonproprietary
Figure 5: (( }}2(a),(c) (( }}2(a),(c) NuScale Nonproprietary NuScale Nonproprietary
Figure 6: (( }}2(a),(c) (( }}2(a),(c) NuScale Nonproprietary NuScale Nonproprietary
Figure 7: (( }}2(a),(c) (( }}2(a),(c) NuScale Nonproprietary NuScale Nonproprietary
Figure 8: (( }}2(a),(c) (( }}2(a),(c) NuScale Nonproprietary NuScale Nonproprietary
Figure 9: (( }}2(a),(c) (( }}2(a),(c) NuScale Nonproprietary NuScale Nonproprietary
Figure 10: (( }}2(a),(c) (( }}2(a),(c) NuScale Nonproprietary NuScale Nonproprietary
Figure 11: (( }}2(a),(c) (( }}2(a),(c) NuScale Nonproprietary NuScale Nonproprietary
Figure 12: (( }}2(a),(c) (( }}2(a),(c) NuScale Nonproprietary NuScale Nonproprietary
Figure 13: (( }}2(a),(c) (( }}2(a),(c) NuScale Nonproprietary NuScale Nonproprietary
Figure 14: (( }}2(a),(c) (( }}2(a),(c) NuScale Nonproprietary NuScale Nonproprietary
Riser Hole Sensitivity Study for ((
}}2(a),(c)
((
}}2(a),(c)
A base group of cases ((
}}2(a),(c) is selected to perform a riser hole sensitivity study. (( }}2(a),(c) Based on the riser hole geometry considerations described above, these sensitivity cases are (( }}2(a),(c),ECI The results of the sensitivity study are shown in Table 2. (( }}2(a),(c)
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Table 2: (( }}2(a),(c) Riser Hole Sensitivity Study (( }}2(a),(c) NuScale Nonproprietary NuScale Nonproprietary
((
}}2(a),(c)
((
}}2(a),(c) Transient plots of relevant parameters for the sensitivity study are shown in Figure 15 through Figure 23. The figures focus on the short-term transient response (( }}2(a),(c)
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(( }}2(a),(c) (( }}2(a),(c) Overall, the results of the riser hole sensitivity study (( }}2(a),(c) demonstrate the following: (( }}2(a),(c) NuScale Nonproprietary NuScale Nonproprietary
(( }}2(a),(c) NuScale Nonproprietary NuScale Nonproprietary
Figure 15: (( }}2(a),(c) (( }}2(a),(c) NuScale Nonproprietary NuScale Nonproprietary
Figure 16: (( }}2(a),(c) (( }}2(a),(c) NuScale Nonproprietary NuScale Nonproprietary
Figure 17: (( }}2(a),(c) (( }}2(a),(c) NuScale Nonproprietary NuScale Nonproprietary
Figure 18: (( }}2(a),(c) (( }}2(a),(c) NuScale Nonproprietary NuScale Nonproprietary
Figure 19: (( }}2(a),(c) (( }}2(a),(c) NuScale Nonproprietary NuScale Nonproprietary
Figure 20: (( }}2(a),(c) (( }}2(a),(c) NuScale Nonproprietary NuScale Nonproprietary
Figure 21: (( }}2(a),(c) (( }}2(a),(c) NuScale Nonproprietary NuScale Nonproprietary
Figure 22: (( }}2(a),(c) (( }}2(a),(c) NuScale Nonproprietary NuScale Nonproprietary
Figure 23: (( }}2(a),(c) (( }}2(a),(c) NuScale Nonproprietary NuScale Nonproprietary
Riser Hole Sensitivity Study for Loss-of-Coolant Accident Event Analyses of LOCA events are outside of the scope of TR-0516-49416-P, Revision 4, Non-Loss-of-Coolant Accident Analysis Methodology (i.e., the non-LOCA topical report); the analyses are addressed in TR-0516-49422-P, Revision 3, Loss-of-Coolant Accident Evaluation Model (i.e., the LOCA topical report). However, similar audit questions regarding riser holes were asked of both topical reports (audit questions A-NonLOCA.LTR-1 and A-LOCA.LTR-2). For this reason, additional sensitivity studies for riser holes are performed for ((
}}2(a),(c) LOCA events and provided in this response.
The LOCA analyses consider multiple break locations and a spectrum of break sizes. As a result, a group of cases with differing locations or differing sizes is run for a consistent set of other initial conditions and bias parameters. Base groups of LOCA cases are selected to perform a riser hole sensitivity study. ((
}}2(a),(c)
Based on the riser hole geometry considerations described above, these sensitivity cases are ((
}}2(a),(c),ECI The results of the sensitivity study are shown in Table 3 (( }}2(a),(c NuScale Nonproprietary NuScale Nonproprietary
((
}}2(a),(c)
Table 4 shows the results of the same sensitivity study ((
}}2(a),(c) The results in Table 4 are similar to those in Table 3. Similar conclusions can be drawn. (( }}2(a),(c)
Table 5 shows the results of the same sensitivity study ((
}}2(a),(c) The results in Table 5 are similar to those in Table 3 and Table 4. (( }}2(a),(c)
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An additional set of sensitivity study results are provided in Table 6 (( }}2(a),(c) The Table 6 results are also similar to those in Table 3 through Table 5. NuScale Nonproprietary NuScale Nonproprietary
Table 3: (( }}2(a),(c) Loss-of-Coolant Accident Riser Hole Sensitivity Study (( }}2(a),(c) NuScale Nonproprietary NuScale Nonproprietary
Table 4: (( }}2(a),(c) Loss-of-Coolant Accident Riser Hole Sensitivity Study (( }}2(a),(c) NuScale Nonproprietary NuScale Nonproprietary
Table 5: (( }}2(a),(c) Loss-of-Coolant Accident Riser Hole Sensitivity Study (( }}2(a),(c) NuScale Nonproprietary NuScale Nonproprietary
Table 6: (( }}2(a),(c) Loss-of-Coolant Accident (( }}2(a),(c) Riser Hole Sensitivity Study ((
}}2(a),(c)
Transient plots of relevant parameters for the sensitivity study are shown in Figure 24 through Figure 32 ((
}}2(a),(c)
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(( }}2(a),(c) Similar transient plots are provided in Figure 33 through Figure 35 (( }}2(a),(c) Overall, the results of the riser hole sensitivity study for the LOCA (( }}2(a),(c) demonstrate the following: (( }}2(a),(c) NuScale Nonproprietary NuScale Nonproprietary
Figure 24: (( }}2(a),(c) (( }}2(a),(c) NuScale Nonproprietary NuScale Nonproprietary
Figure 25: (( }}2(a),(c) (( }}2(a),(c) NuScale Nonproprietary NuScale Nonproprietary
Figure 26: (( }}2(a),(c) (( }}2(a),(c) NuScale Nonproprietary NuScale Nonproprietary
Figure 27: (( }}2(a),(c) (( }}2(a),(c) NuScale Nonproprietary NuScale Nonproprietary
Figure 28: (( }}2(a),(c) (( }}2(a),(c) NuScale Nonproprietary NuScale Nonproprietary
Figure 29: (( }}2(a),(c) (( }}2(a),(c) NuScale Nonproprietary NuScale Nonproprietary
Figure 30: (( }}2(a),(c) (( }}2(a),(c) NuScale Nonproprietary NuScale Nonproprietary
Figure 31: (( }}2(a),(c) (( }}2(a),(c) NuScale Nonproprietary NuScale Nonproprietary
Figure 32: (( }}2(a),(c) (( }}2(a),(c) NuScale Nonproprietary NuScale Nonproprietary
Figure 33: (( }}2(a),(c) (( }}2(a),(c) NuScale Nonproprietary NuScale Nonproprietary
Figure 34: (( }}2(a),(c) (( }}2(a),(c) NuScale Nonproprietary NuScale Nonproprietary
Figure 35: (( }}2(a),(c) (( }}2(a),(c) NuScale Nonproprietary NuScale Nonproprietary
Riser Hole Sensitivity Studies for Additional Chapter 15 Events In addition to the riser hole sensitivity studies for the Chapter 15 events described above, (( }}2(a),(c) Riser Hole Sensitivity Study for Test Assessments As described previously, (( }}2(a),(c) The following (( }}2(a),(c) test assessments are selected for sensitivity studies (( }}2(a),(c) (( }}2(a),(c) NuScale Nonproprietary NuScale Nonproprietary
For each of the above test assessments, ((
}}2(a),(c)
Figure 36 to Figure 40 provide the results of the sensitivity ((
}}2(a),(c)
((
}}2(a),(c)
Figure 41 to Figure 45 provide the results of the sensitivity ((
}}2(a),(c)
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(( }}2(a),(c) Figure 46 to Figure 50 provide the results of the sensitivity (( }}2(a),(c) Figure 51 to Figure 53 provide the results of the sensitivity (( }}2(a),(c) (( }}2(a),(c) Overall, the results of the sensitivity studies for test assessments demonstrate the following: (( }}2(a),(c) NuScale Nonproprietary NuScale Nonproprietary
Figure 36: (( }}2(a),(c) (( }}2(a),(c) NuScale Nonproprietary NuScale Nonproprietary
Figure 37: (( }}2(a),(c) (( }}2(a),(c) NuScale Nonproprietary NuScale Nonproprietary
Figure 38: (( }}2(a),(c) (( }}2(a),(c) NuScale Nonproprietary NuScale Nonproprietary
Figure 39: (( }}2(a),(c) (( }}2(a),(c) NuScale Nonproprietary NuScale Nonproprietary
Figure 40: (( }}2(a),(c) (( }}2(a),(c) NuScale Nonproprietary NuScale Nonproprietary
Figure 41a: (( }}2(a),(c) (( }}2(a),(c) NuScale Nonproprietary NuScale Nonproprietary
Figure 41b: (( }}2(a),(c) (( }}2(a),(c) NuScale Nonproprietary NuScale Nonproprietary
Figure 42a: (( }}2(a),(c) (( }}2(a),(c) NuScale Nonproprietary NuScale Nonproprietary
Figure 42b: (( }}2(a),(c) (( }}2(a),(c) NuScale Nonproprietary NuScale Nonproprietary
Figure 43a: (( }}2(a),(c) (( }}2(a),(c) NuScale Nonproprietary NuScale Nonproprietary
Figure 43b: (( }}2(a),(c) (( }}2(a),(c) NuScale Nonproprietary NuScale Nonproprietary
Figure 44a: (( }}2(a),(c) (( }}2(a),(c) NuScale Nonproprietary NuScale Nonproprietary
Figure 44b: (( }}2(a),(c) (( }}2(a),(c) NuScale Nonproprietary NuScale Nonproprietary
Figure 45a: (( }}2(a),(c) (( }}2(a),(c) NuScale Nonproprietary NuScale Nonproprietary
Figure 45b: (( }}2(a),(c) (( }}2(a),(c) NuScale Nonproprietary NuScale Nonproprietary
Figure 46a: (( }}2(a),(c) (( }}2(a),(c) NuScale Nonproprietary NuScale Nonproprietary
Figure 46b: (( }}2(a),(c) (( }}2(a),(c) NuScale Nonproprietary NuScale Nonproprietary
Figure 47a: (( }}2(a),(c) (( }}2(a),(c) NuScale Nonproprietary NuScale Nonproprietary
Figure 47b: (( }}2(a),(c) (( }}2(a),(c) NuScale Nonproprietary NuScale Nonproprietary
Figure 48a: (( }}2(a),(c) (( }}2(a),(c) NuScale Nonproprietary NuScale Nonproprietary
Figure 48b: (( }}2(a),(c) (( }}2(a),(c) NuScale Nonproprietary NuScale Nonproprietary
Figure 49a: (( }}2(a),(c) (( }}2(a),(c) NuScale Nonproprietary NuScale Nonproprietary
Figure 49b: (( }}2(a),(c) (( }}2(a),(c) NuScale Nonproprietary NuScale Nonproprietary
Figure 50a: (( }}2(a),(c) (( }}2(a),(c) NuScale Nonproprietary NuScale Nonproprietary
Figure 50b: (( }}2(a),(c) (( }}2(a),(c) NuScale Nonproprietary NuScale Nonproprietary
Figure 51: (( }}2(a),(c) (( }}2(a),(c) NuScale Nonproprietary NuScale Nonproprietary
Figure 52: (( }}2(a),(c) (( }}2(a),(c) NuScale Nonproprietary NuScale Nonproprietary
Figure 53: (( }}2(a),(c) (( }}2(a),(c) NuScale Nonproprietary NuScale Nonproprietary
Conclusion The information provided in the previous response to audit question A-NonLOCA.LTR-1 and this response demonstrates that NRELAP5 reasonably calculates the small impact of riser holes on an NPM during both steady-state conditions and the short-term transient response to non-LOCA events. TR-0516-49416-P is revised to identify that sensitivity studies were performed for test assessments and NPM design-basis events and that the results show that riser holes do not have a significant impact on non-LOCA transient progression and figures of merit. The conclusions from the sensitivity studies in this response are consistent with the prior NuScale conclusion that additional studies were not warranted. Impact on Topical Report: Topical Report TR-0516-49416, Non-Loss-of-Coolant Accident Analysis Methodology, has been revised as described in the response above and as shown in the markup provided in this response. NuScale Nonproprietary NuScale Nonproprietary
Non-Loss-of-Coolant Accident Analysis Methodology TR-0516-49416-NP Draft Revision 5 © Copyright 2024 by NuScale Power, LLC 7
The non-LOCA evaluation model is applicable to a nuclear power plant that follows the general description of the NuScale plant designs in Section 3.0. The applicability of the EM is based on the non-LOCA phenomena identification and ranking table and assessment of the high-ranked phenomena that are treated as part of the system transient analysis.
The non-LOCA evaluation model does not address the evaluation of specified acceptable fuel design limits (SAFDLs), which are evaluated in a downstream subchannel analysis. The subchannel analysis codes and methods are covered in separate methodologies and assessments (Reference 6, supplemented by Reference 28). However, the interface of the non-LOCA system transient analysis with the downstream subchannel analysis is part of the non-LOCA evaluation model.
The non-LOCA evaluation model does not address the evaluation of the accident radiological source term and dose. The accident radiological source term and dose analyses are covered in separate methodologies and assessments (Reference 8). However, the interface of the non-LOCA system transient analysis with downstream radiological analysis is part of the non-LOCA evaluation model.
The EM is applicable for the short-term non-LOCA transient progression; the non-LOCA transient analysis short-term duration and analysis process are discussed further in Section 4.2 and Section 4.3. During this time frame the mixture level remains above the top of the riser and primary side natural circulation is maintained. The reactivity control and extended passive cooling analysis methodology in the long-term, including events that transition from DHRS cooling to ECCS cooling, is addressed in separate methodologies and assessments (Reference 26). RAI 10297 Question NonLOCA.LTR-1
The plant design overview description in Section 3.0, plant model description in Section 6.0, input and biasing discussion in Section 7.0, and the example calculations in Section 8.0 do not include the design feature of riser holes (upper or lower). Riser holes are included in the NPM designs to mitigate potential boron dilution impacts of long term DHRS cooling and riser uncovery. The riser holes do not impact the short term DHRS cooldown during the non-LOCA phase. The PIRT and test assessments in Section 5.0 did not incorporate the riser holes; however, the PIRT and assessments documented in Section 5.0 remain valid, since the design feature of the riser holes results in negligible differences in the prediction of RCS parameters for the short-term non-LOCA transient progression as confirmed by sensitivity studies discussed in Section 5.0 and Section 7.0. The effect of the riser holes during extended passive cooling is addressed in separate methodologies and assessments (Reference 26).
Control rod ejection accident analysis is addressed by a separate methodology (Reference 21) and is not part of the non-LOCA evaluation model.
Loss of coolant accident analysis, including analysis of an inadvertent opening of one or more valves on the RPV, is addressed by a separate methodology (Reference 2) and is not part of the non-LOCA evaluation model.
Analysis of the peak containment pressure and temperature response is addressed by a separate methodology (Reference 2) and is not part of the non-LOCA evaluation model.
Non-Loss-of-Coolant Accident Analysis Methodology TR-0516-49416-NP Draft Revision 5 © Copyright 2024 by NuScale Power, LLC 26 of a spring loaded arming valve in the vent port path from the main disc chamber to the vent line. If the differential pressure across this arming valve is greater than a threshold value, the arming valve closes, which prevents the main disc chamber from discharging through the vent line, blocking the RRV from opening. The RRV does not open until the arming valve differential pressure decreases below the release pressure. The IAB is also used in the RVVs for some NPM designs. Provided the IAB device setpoint is reached, if applicable, the RVV and RRV components fail to the open (safe) position upon the loss of power, thus enabling reliable long-term cooling without operator actions, alternating current (AC) or direct current (DC) power, or make-up water. Successful operation of the ECCS requires isolation of the containment, such that the coolant inventory of the RCS is preserved. 3.5 Other Important Systems and Functions Other systems and functions that are important in mitigating plant response during a postulated non-LOCA event are discussed below. Reactor Coolant System The reactor coolant system (RCS) consists of the RPV, reactor core, riser, upper plenum, SGs (shell side), downcomer, lower plenum, and pressurizer (PZR). The arrangement of the RCS and the relative locations of the thermal centers in the core and the SGs promote buoyancy driven natural circulation flow. The RPV consists of a steel cylinder with an inside diameter of approximately 10 ft and an overall height of approximately 60 ft and is designed for a normal operating pressure of approximately 1850-2000 psia. Nozzles on the upper head provide connections for reactor safety valves (RSVs) and RVVs. The core configuration for an NPM consists of 37 fuel assemblies and 16 control rod assemblies (CRAs). The fuel assembly design is modeled from a standard 17x17 PWR fuel assembly with 24 guide tube locations for control rod fingers and a central instrument tube. The assembly is nominally half the height of standard plant fuel and is supported by five spacer grids. The U-235 enrichment is below the current U.S. manufacturer limit of 4.95 weight percent. RAI 10297 Question NonLOCA.LTR-1 Each NPM uses two once-through helical coil SGs for steam production. The SGs, which produce superheated steam, are located in the annular space between the RCS hot leg riser and the reactor vessel inside diameter wall. Each SG is designed to remove 50 percent of the rated core thermal power. Flow paths in the upper riser are provided to mitigate potential boron dilution impacts during long-term DHRS cooling and riser uncovery. An NPM design may include flow paths in the lower riser to mitigate potential boron dilution impacts near the core inlet during long-term ECCS cooling. The PZR provides the primary means for controlling RCS pressure. PZR heaters and spray maintain a constant reactor coolant pressure during operation. A steel PZR baffle
Non-Loss-of-Coolant Accident Analysis Methodology TR-0516-49416-NP Draft Revision 5 © Copyright 2024 by NuScale Power, LLC 475 RAI 10297 Question NonLOCA.LTR-1 5.3.7.13 Impact of NPM Riser Holes on NIST Test Assessments The NPM design may include holes in the riser that allow cross-flow between the riser and downcomer. (( }}2(a),(c) The overall performance of the NRELAP5 code and model, in terms of its level of code-to-data agreement, did not change from the previous assessment. The NIST-2 assessments described in Section 5.3.7 (( }}2(a),(c) The above results provide confidence in the ability of NRELAP5 to simulate natural circulation flow and temperature distribution in the presence of cross-flow holes in the riser while also demonstrating that such riser holes do not significantly impact the NIST test assessments. 5.4 Conclusions of NRELAP5 Applicability for Non-LOCA The high-ranked phenomena identified by the PIRT process for NPM non-LOCA transients were evaluated with respect to the high-ranked phenomena identified by the PIRT process for NPM LOCA scenarios, as well as the NRELAP5 assessments performed as part of the NuScale LOCA evaluation model development. A gap analysis was performed to identify high-ranked phenomena for non-LOCA transients that are not assessed as part of the NuScale LOCA evaluation model development. High-ranked phenomena for non-LOCA events that are not assessed as part of the NuScale LOCA evaluation model development were addressed in different ways:
- 1. Additional NRELAP5 code assessment performed against separate effects or integral effects test data
- 2. Code-to-code benchmark performed between NRELAP5 and independent system thermal-hydraulics code
- 3. Phenomenon is addressed as part of the downstream subchannel analysis
Non-Loss-of-Coolant Accident Analysis Methodology TR-0516-49416-NP Draft Revision 5 © Copyright 2024 by NuScale Power, LLC 489 Lower Riser Audit Question A-NonLOCA.LTR-63 RAI 10297 Question NonLOCA.LTR-1 (( }}2(a),(c) Figure 6-6 Reflector / core bypass without fuel assemblies (for illustration only)
Non-Loss-of-Coolant Accident Analysis Methodology TR-0516-49416-NP Draft Revision 5 © Copyright 2024 by NuScale Power, LLC 492 Upper Riser Audit Question A-NonLOCA.LTR-63 RAI 10297 Question NonLOCA.LTR-1 (( }}2(a),(c) Normal flow in the riser is single-phase subcooled water. Transients that involve RPV depressurization or inventory loss can result in flashing and two-phase flow in the riser region. (( }}2(a),(c) Figure 6-9 Typical reactor pressure vessel upper riser model (( }}2(a),(c)
Non-Loss-of-Coolant Accident Analysis Methodology TR-0516-49416-NP Draft Revision 5 © Copyright 2024 by NuScale Power, LLC 525 reactor trip from hot full power. An example of a normalized trip worth as a function of time, for which the control rods are fully inserted 2.278 seconds after being released by the control rod drive mechanisms, is presented in Table 7-2. 7.1.6 Biasing of Other Parameters This section describes the biasing of non-reactivity parameters used for the non-LOCA transient analyses. A brief discussion of each parameter is provided in the following sections.
Initial Conditions (Section 7.1.6.1)
Valve Characteristics (Section 7.1.6.2)
Analytical Limits and Response Times (Section 7.1.6.3) RAI 10297 Question NonLOCA.LTR-1
Riser Holes (Section 7.1.6.4) 7.1.6.1 Initial Conditions The initial conditions assumed for the non-LOCA transient analyses are the most adverse with respect to the acceptance criterion of interest. These conditions are normally consistent with steady state operation, allowing for calibration and instrument errors and steady state fluctuations. Recognizing that the initial conditions do not contribute equally to the severity of the event consequences, alternate approaches may be used to set these conditions. For instance, bounding values may be used for certain parameters to provide a more restrictive response for a specific acceptance criterion. Alternately, nominal conditions may be used if the event consequences are insensitive to a specific initial condition. A general description of the biasing of initial conditions, as applied to the non-LOCA transient analyses for an NPM, is provided below. Table 7-2 Example of normalized trip worth vs. time after trip Time After Trip (sec) Normalized Trip Worth 0.0 0.0 0.428 0.011 0.616 0.044 0.766 0.099 0.900 0.176 1.022 0.276 1.138 0.397 1.220 0.502 1.250 0.540 1.458 0.706 1.952 0.893 2.278 1.0
Non-Loss-of-Coolant Accident Analysis Methodology TR-0516-49416-NP Draft Revision 5 © Copyright 2024 by NuScale Power, LLC 531 RAI 10297 Question NonLOCA.LTR-1 7.1.6.4 Riser Holes Flow paths in the lower riser and upper riser are modeled based on their nominal dimensions and form losses per the NPM design. Tolerances specified on riser hole dimensions and elevations in the design ensure the uncertainty in riser hole area is small. Riser holes have minimal impact on the short-term non-LOCA transient progression. Sensitivity studies (( }}2(a),(c) were performed. The sensitivity study results confirmed that (( }}2(a),(c) the impact on figures of merit relevant to short-term non-LOCA was negligible. 7.1.7 Credit for Nonsafety-related Components or Operator Actions There are three occasions where nonsafety-related equipment is credited for event mitigation by the non-LOCA transient analyses. Listed below is the equipment associated with these occurrences. Table 7-3 Examples of analytical limits and actuation delays (reactor trip system and engineered safety features actuation system) Signal Analytical Limit Actuation Delay High power 25% RTP (power < 15% RTP) 2.0 seconds 120% RTP (power 15% RTP) 2.0 seconds High count rate 5.0E+5 counts/second 2.0 seconds Startup rate 3 decades/minute 31 seconds (source range) 3 decades/minute 2 seconds (intermediate range) High power rate +/-15% RTP/minute 2.0 seconds High RCS riser temperature 610°F 8.0 seconds High containment pressure 9.5 psia 2.0 seconds High pressurizer pressure 2000 psia 2.0 seconds High pressurizer level 80% 3.0 seconds Low pressurizer pressure 1720 psia 2.0 seconds Low low pressurizer pressure 1600 psia 2.0 seconds Low pressurizer level 35% 3.0 seconds Low low pressurizer level 20% 3.0 seconds Low steam pressure 300 psia 2.0 seconds Low low steam pressure 100 psia 2.0 seconds High steam pressure 800 psia 2.0 seconds High steam superheat 150°F 8.0 seconds Low steam superheat 0°F 8.0 seconds Low RCS flow 1.7 ft3/second 6.0 seconds Low low RCS flow 0.0 ft3/second 6.0 seconds Low RCS level 350-390 inches 3.0 seconds High CNV water level 220-260 inches 3.0 seconds Low AC voltage 0 VAC 60.0 seconds
Non-Loss-of-Coolant Accident Analysis Methodology TR-0516-49416-NP Draft Revision 5 © Copyright 2024 by NuScale Power, LLC 666 8.0 Representative Calculations RAI 10297 Question NonLOCA.LTR-1 The methodology of Chapter 7 is utilized in conjunction with the NRELAP5 model of Chapter 6 to provide representative transient results. The calculations are for a representative NPM design, consistent with the design characteristics in Chapter 3. Riser holes are not modeled in the representative calculations. The transients noted below were selected to demonstrate the application of the NuScale Non-LOCA methodology for analysis of the representative plant responses to a wide range of postulated equipment failures and malfunctions. 1. Cooldown and/or Depressurization of the RCS (Section 8.1) 2. Heatup and/or Pressurization of the RCS (Section 8.2) 3. Reactivity Anomaly (Section 8.3) 4. Increase in RCS Inventory (Section 8.4) 5. Decrease in RCS Inventory (Section 8.5) The information included for each representative transient includes: an event description; the results for the acceptance criteria of interest; and, conclusions regarding the acceptance criteria of interest. These results are presented to demonstrate the application of the non-LOCA methodology to a representative NPM. Fuel rod and core physics parameter inputs for the representative transients were developed using COPERNIC (Reference 22) and SIMULATE5 (Reference 23) respectively. 8.1 Cooldown and/or Depressurization of the Reactor Coolant System 8.1.1 Decrease in Feedwater Temperature The purpose of this section is to present the thermal-hydraulic response of a representative NPM for a decrease in feedwater temperature event. This event is evaluated for MCHFR. 8.1.1.1 Event Description The general decrease in feedwater temperature (DFWT) event description can be found in Section 7.2.1.1. Based on Section 7.2.1.1, MCHFR is the only acceptance criterion that may be potentially challenged during the DFWT event. No single failure is applied since the challenging cases occur when all equipment operates as designed. No loss of power is applied since all loss of power scenarios terminate feedwater or trip the reactor, thus reducing the overcooling event. Chosen from a series of MCHFR sensitivity cases, the representative DFWT case presented here represents a case that could challenge MCHFR, based on the NRELAP5 MCHFR pre-screening. This case features the following conditions:
Conservative initial condition biasing (as shown in Table 7-7) is applied in order to maximize the consequences of the overcooling event in terms of
RAIO-177428 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-177435
AF-177435 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. 10297 R1, Question NonLOCA.LTR-1) 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 10297 R1, Question NonLOCA.LTR-1. 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-177435 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 19, 2024. Mark W. Shaver}}