ML25069A650
| ML25069A650 | |
| 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: ML25069A650 (1) | |
Text
Response to NuScale Topical Report Audit Question Question Number: A-FSR.LTR-52 Receipt Date: 10/14/2024 Question:
Section 6.2 Assumptions, states, [
] The licensees response to AFSR.LTR10 points the reviewer to Section 8.6.4.3 of EC139299 R1 for a demonstration of why [
] However, Section 8.6.4.3 of EC139299 R1 does not provide demonstration of why [
] Instead Section 8.6.4.3 of EC139299 R1 potentially provides [
] Section 8.6.4.3 of EC139299 R1 does not address what depletion parameters were used in the analysis, so the demonstration lacks specificity. Therefore the question remains, how is [
]?
Response
The presence of an insert in the fuel assembly guide and instrument tubes has two primary impacts on reactivity during depletion that harden the spectrum: 1) the displacement of moderator in the guide tubes, and 2) the presence of materials that absorb neutrons. In the case of neutron source assemblies, the dominating factor that hardens the spectrum is the displacement of moderator since [
] Since the details of the neutron source assembly are not available, as described in the response to A-FSR.LTR-10, engineering judgment was applied and determined a conservative approach [
]
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[
]
The Electric Power Research Institute (EPRI) conducted a study of the reactivity impact of an in-core detector in the instrument tube in EPRI Report 3002008197, Sensitivity Analyses for Spent Fuel Pool Criticality, Revision 1 (Section 3). The results of the analysis show that the reactivity effect of the in-core detector in the instrument tube (EPRI assumed void in place of water) was as much as 0.0010 k from depletion effects. The conservative analysis presented in Section 8.6.4.3 of EC-139299 R1 (Figure 8-21), shows that [
] for the burnup and enrichment combinations in Table 6-35 of the topical report. The conclusion from this comparison is that modeling [
] this approach provides an additional conservative bias in the overall criticality safety analysis.
No changes to the LTR are necessary.
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