ML25027A394
| ML25027A394 | |
| Person / Time | |
|---|---|
| Site: | 05200050 |
| Issue date: | 01/27/2025 |
| From: | NuScale |
| To: | Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML25027A392 | List: |
| References | |
| LO-178725 | |
| Download: ML25027A394 (1) | |
Text
Response to SDAA Audit Question Question Number: SGFIV Flow Testing Report Summary Receipt Date:
Question:
Provide a summary of the SGFIV test report for docketing to support Chapter 3.9.2 Safety Evaluation.
Response
The following summary reflects ER-175773, SGFIV Flow Test Data Analysis, Revision 0 engineering report issued to analyze the results of the steam generator flow induced vibration (SGFIV) flow testing for use in the NPM-20 standard design application. The testing summary focuses on the following areas:
Demonstration that fluid elastic instability (FEI) and vortex shedding (VS) do not occur for the expected NuScale Power Module (NPM) flows with margin.
Presentation of damping results over the tested flow ranges.
Evidence that the use of dynamic pressure sensors during comprehensive vibration assessment program (CVAP) startup testing is a reasonable method to detect significant vibrations of steam generator tubes.
Justification that the tube supports used in the SGFIV test specimen provide sufficient test results to be applied to the NPM-20 design.
Steam generator flow-induced vibration flow testing validates fluid elastic instability (FEI) and vortex shedding (VS) design analysis margin for the NPM-20 operating range. These vibration mechanisms are applicable to the primary side flow across the outside of the SG tubes.
((2(b),(c) The trends of the sensor responses throughout the range of velocities tested are consistent with low-velocity turbulent buffeting (TB). For NuScale Nonproprietary NuScale Nonproprietary
(( }}2(b),(c) Figure 1 and Figure 2 show displacement power spectral densities (PSDs) as a function of test specimen flow. (( }}2(b),(c),ECI NuScale Nonproprietary NuScale Nonproprietary
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The peak-to-peak modal displacement as a function of flow is provided for sensors that show the largest displacements in Figure 3 through Figure 5. (( }}2(b),(c) (( }}2(b),(c),ECI NuScale Nonproprietary NuScale Nonproprietary
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The test results show high coherence in the FIV range between tube modes with high displacement and dynamic pressure sensors at varying distances. The results indicate that the use of dynamic pressure sensors is an effective approach to detect significant vibrations in the NPM-20 steam generator tubes. Figure 6 and Figure 7 show dynamic pressure sensor response coherence as a function of frequency and flow. Adjacent dynamic pressure sensors produced similar results, which indicates consistent performance and installation demonstrating these sensors are appropriate for full benchmarking of the dynamic pressure sensors for startup testing. (( }}2(b),(c),ECI NuScale Nonproprietary NuScale Nonproprietary
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(( }}2(b),(c),ECI (( }}2(b),(c),ECI NuScale Nonproprietary NuScale Nonproprietary
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Comparisons of tube and tube support frequencies in the displacement spectra indicate that the support conditions of the tubes behaved linearly and tube modes determined from the test data compare well with the modal analysis used in the pre-test predictions which uses linear boundary conditions. (( }}2(a),(c) Neither VS and FEI were observed in the testing. The NPM margins are minimum values based on the maximum flow rate tested. In summary, the SGFIV Flow Testing documented in ER-175773 met the objectives supporting pre-test predictions and confirm the safety of the SG design against damaging vibration mechanisms as represented in the US460 Standard Design Approval Application and NPM-20 comprehensive vibration assessment program. No changes to the SDAA are necessary. NuScale Nonproprietary NuScale Nonproprietary}}