ML25069A611
| ML25069A611 | |
| 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: ML25069A611 (1) | |
Text
Response to NuScale Topical Report Audit Question Question Number: A-FSR.LTR-8 Receipt Date: 05/10/2024 Question:
Table 6-8 provides the manufacturing tolerance uncertain factors versus enrichment for 0 and 1450 ppm Boron. Table 6-9 provides the combined uncertainy of the individual factors. Please provide a short discussion of how these values are combined to develop Table 6-9.
Response
Section 6.5.1.1 provides an explanation of how the combined uncertainty factors in Table 6-9 and Table 6-10 are determined from Table 6-7 and Table 6-8, respectively. For each enrichment in Tables 6-8 and 6-9, the uncertainty factors for Pin Pitch, Clad OD, and Storage Cell Width vary by enrichment, while the maximum uncertainty factors are used for GT IT, Absorber Width, and Cell Pitch. The maximum uncertainty factors, independent of enrichment were chosen for GT IT, Absorber Width, and Cell Pitch because the factors
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Additionally, NuScale self-identified an editorial error in the uncertainty factors reported in Table 6-7 and Table 6-8 for the Storage Cell Width. Those uncertainty factors are updated to match the criticality analysis, EC-139299, US460 Fuel Racks - Nuclear Criticality Safety Evaluation of Spent Fuel Storage Racks. No changes were necessary for the combined uncertainty factors in Table 6-9 or Table 6-10, or the overall final maximum keff values.
Markups of the affected changes, as described in the response, are provided below:
NuScale Nonproprietary NuScale Nonproprietary
NuScale US460 Fuel Storage Rack Design Topical Report TR-145417-NP Draft Revision 1
© Copyright 2024 by NuScale Power, LLC 145 The uncertainty factors for the individual manufacturing tolerances are shown in Table 6-7 and Table 6-8, while the statistically combined uncertainty factors are shown in Table 6-9 and Table 6-10. The uncertainty factors for the Guide and Instrument Tubes (GT ITs), the neutron absorber plate width, and the cell pitch are small and exhibit a significant amount of scatter. The maximum value of these three uncertainty terms are used instead of the enrichment dependent values to compute the statistically combined uncertainty factors.
Audit Question A-FSR.LTR-3, Audit Question A-FSR.LTR-4, Audit Question A-FSR.LTR-5 Table 6-7 Manufacturing Tolerance Uncertainty Factors versus Enrichment, 0 ppm Boron
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NuScale US460 Fuel Storage Rack Design Topical Report TR-145417-NP Draft Revision 1
© Copyright 2024 by NuScale Power, LLC 146 Audit Question A-FSR.LTR-3, Audit Question A-FSR.LTR-4, Audit Question A-FSR.LTR-5 Table 6-8 Manufacturing Tolerance Uncertainty Factors versus Enrichment, 1450 ppm Boron
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Table 6-9 Combined Uncertainty Factors versus Enrichment, 0 ppm Boron
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