ML24326A347
| ML24326A347 | |
| Person / Time | |
|---|---|
| Site: | 05200050, 99902078 |
| Issue date: | 11/21/2024 |
| From: | NuScale |
| To: | Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML24326A327 | List: |
| References | |
| LO-176070 | |
| Download: ML24326A347 (1) | |
Text
Response to NuScale Topical Report Audit Question Question Number: A-LOCA.LTR-48 Receipt Date: 05/06/2024 Question:
NRELAP validation requires SET and IET that scale NPM for individual phenomenon or a plant transient. NIST1 and NIST2 facilities are built to provide scaled data for LOCA in NuScale designs. One approach is to simulate tests with NRELAP and compare the predictions with the data. This approach is not sufficient for validation with IET data as the underlying phenomena may compensate and provide acceptable comparison. For adequacy of the code and validation, it is important the non-dimensional groups representing high ranking or dominant phenomena are of same order of magnitude and are high ranking in both test facilities and NPM. A top-down scaling will confirm that. Scaling results for NuScale are documented in multiple reports; EE-080-8025 Rev 1, EE-101798 Rev 2. The staff has the following audit questions.
a) (( 2(a)(c) Explain and justify the differences of this boundary condition. b) (( }} 2(a)(c) Explain the differences in RPV pressure predictions? c) (( }} 2(a)(c) NuScale Nonproprietary NuScale Nonproprietary
(( }} 2(a)(c) d) (( }} 2(a)(c) Please explain and justify this process.
Response
Item a) (( }}2(a)(c) NuScale Nonproprietary NuScale Nonproprietary
((
}}2(a)(c) This is demonstrated by the core power plots provided in response to audit question A-LOCA.LTR-36. The audit question A-XPC.LTR-15 requests information regarding Phase 2 scaling distortions, and therefore, Phase 2 is not discussed further herein.
Item b) The differences observed for the comparison of NPM-160 and NIST-1 to NPM-250 and NIST-2 in ((
}}2(a)(c)
Item c) ((
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((
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(( }}2(a)(c) (( }}2(a)(c) ((
}}2(a)(c) To summarize, the break enthalpy NuScale Nonproprietary NuScale Nonproprietary
difference flow Pi group considers more than the enthalpy from the break location and can be negative depending on the break location. (( }}2(a)(c) (( }}2(a)(c) 1. Although the transient progression differs between NPM-160 and NPM-20, there are no significant changes to the LOCA, containment vessel, or IORV phenomena identification and ranking table. The top-down applicability shows the same dominant phenomena in the LOCA transient between NPM-160 and NPM-20. 2. The bottom-up applicability shows that the applied ranges of closure models are not significantly different in the LOCA transient between NPM-160 and NPM-20. ) ((
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(( }}2(a)(c) Therefore, considering the plant designs and NIST test conditions, results of the supporting scaling analyses, and LOCA evaluation model applicability assessments, the similarities between NPM-160 and NIST-1 can be applied to the comparison of NPM-250 and NIST-2. Item d) To clarify, normalized Pi group values are not utilized for distortion factor calculations. Normalizing to the most dominant Pi group between the model and prototype provides the relative distortion to the most dominant process. Therefore, other Pi groups are less than unity and ranged according to their magnitudes. This allows the analyst to evaluate the relative importance of each parameter and identify if highly important Pi groups are distorted between the model and prototype. (( }}2(a)(c) EE-101798 and ER-119368 are available in the eRR as part of the response to audit question A-LOCA.LTR-4. Revised Response (( }}2(a)(c) NuScale Nonproprietary NuScale Nonproprietary
This revised response clarifies the process for calculating the normalized PI groups. ((
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((
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Revised Response - September 2024 ((
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(( }}2(a)(c) No changes to the SDAA are necessary. NuScale Nonproprietary NuScale Nonproprietary}}