ML25069A614
| ML25069A614 | |
| Person / Time | |
|---|---|
| Site: | 05200050 |
| Issue date: | 03/10/2025 |
| From: | NuScale |
| To: | Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML25069A609 | List: |
| References | |
| LO-180139 | |
| Download: ML25069A614 (1) | |
Text
Response to NuScale Topical Report Audit Question Question Number: A-FSR.LTR-26 Receipt Date: 10/07/2024 Question:
Justify the selection of the lowest coefficient of friction based on the maximum acceleration in Phase II of the Bounding Condition Analysis, and why the stress analysis does not need to consider a higher coefficient of friction. Section 4.3.3.2 of the report notes that the maximum acceleration for the lowest coefficient of friction is not significantly different from the other three cases. While the lowest coefficient of friction may somewhat increase accelerations, sliding, and impact forces; it seems a higher coefficient of friction would maximize stresses in some components like the support legs. Additionally, a higher coefficient of friction may increase overturning. Since uplift is currently negligible, this may be insignificant.
Response
A coefficient of friction of [
] and an initial gap between fuel storage racks (FSRs) of
[
] in the whole pool model are selected to maximize the global response of the FSRs (i.e., accelerations, sliding, and impact). Although increasing the coefficient of friction leads to reduced sliding and increased risk of overturning, no results in the Phase II bounding condition analyses or the subsequent whole pool analysis indicate overturning is a significant concern.
An increased coefficient of friction could result in larger reactions under the legs and affect their local evaluation. The bounding condition calculation includes the total rack reactions on the spent fuel pool floor for each of the Phase II analyses. The case with a coefficient of friction of
[
] results in an average increase of approximately [
] times the total lateral reactions from the racks than the case with a coefficient of friction of [
]. Increasing the stress ratios from the local leg qualification from Table 4-25 by [
], which conservatively increases the effects of both the lateral and vertical load contributions, yields acceptable results for the leg and foot components. [
]
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[
] the qualification results in sufficient margin to account for an increased reaction due to a change in coefficient of friction.
No changes to the LTR are necessary.
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