ML24215A047

LLC, Response to Sdaa Audit Question Number A-3.9.2-5

ML24215A047
Person / Time
Site:	05200050
Issue date:	08/02/2024
From:	NuScale
To:	Office of Nuclear Reactor Regulation
Shared Package
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References
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Download: ML24215A047 (1)

Text

Response to SDAA Audit Question Question Number: A-3.9.2-5 Receipt Date: 04/03/2023 Question:

NuScale has changed significantly the HCSG tube support system from the DCA submission. The staff met with NuScale prior to the acceptance review to examine plastic mockups of the tube supports, and has read the design descriptions in FSAR Chapter 5.4.2 and the FIV evaluation summary provided in TR-121353 CVAP Analysis. However, the staff needs to better understand the new tube support design, the likelihood that all tubes will have sufficient vertical and radial contact at all tube support locations to preclude any long unsupported sections, and how the upcoming confirmatory FIV measurements in the SIET TF-3 facility (based on older tube support designs) will be sufficient to confirm safe operation of the HCSG in the NPM-20. For this audit NuScale should make available:

1. Any and all design reports, drawings, assembly drawings/plans, mockups, and other materials that will help explain the new SG tube support designs.

2. Estimates of the quasi-static SG tube deflections at full power conditions due to all hydraulic, thermal, gravity, and dynamic phenomena and if available, the corresponding estimated vertical and radial reaction forces of the tube walls against the SG supports.

3. Plans and drawings for any mockups that NuScale may build and exercise to evaluate the assembly of the HCSG and support system and the percentage of tubes expected to be in strong contact with the supports.

4. Assessments of the experimental bias/correction factors to be applied to future SIET TF-3 measurements to map them to NPM-20 conditions with the new SG tube support design.

5. Assessments of the possibility of inactive tube supports, particularly near the bottom of the SG system, based on allowable tolerances in the SG tubes, tube supports and assembly, and NuScale Nonproprietary NuScale Nonproprietary

the quasi-static deflection assessments in item 2. If there is a reasonable chance of an inactive support how would the projected margins against VS and FEI change?

Response

Item 1 The following documents have been added to the eRR to provide the requested information: ((2(a),(c),ECI Item 2 A Finite Element Analysis (FEA) of the steam generator (SG) assembly has been performed to estimate SG tube deflections and SG tube-to-tube support reaction forces at full power operations. The analysis considers significant steady-state full power loading conditions as well as the latest SG support design. The significant loads on the tubes are ((

}}2(a),(c),ECI Based on the results of the FEA evaluation described above, the SG tubes within the helical region primarily (( 
}}2(a),(c),ECI Reaction forces for the six modeled tubes were calculated at each of the modeled SG tube-to-tube supports in a global cylindrical coordinate system, providing results in the radial, angular, NuScale Nonproprietary NuScale Nonproprietary

and vertical directions. At each SG tube-to-tube support contact locations, the primary reaction force on the tube is (( }}2(a),(c),ECI A summary of maximum and minimum reaction forces for each SG tube-to-tube support contact location is presented in Table 1. Table 1. (( }}2(a),(c),ECI Based on the magnitude and consistency of the reaction forces shown in Table 1 for the representative SG tubes included in the FEA evaluation, the SG tubes are expected to have contact reaction forces and deflections similar to those included in the FEA evaluation discussed above. Item 3 No mockups are currently used to specifically evaluate the steam generator (SG) tube-to-tube support fit-up. The assessment of tube-to-tube support shows (( }}2(a),(c),ECI Item 4 (( }}2(a),(c),ECI NuScale Nonproprietary NuScale Nonproprietary

Item 5 The results of Item 2 show that there is consistent contact force between the tube and tube support. The (( }}2(a),(c),ECI No changes to the SDAA are necessary. NuScale Nonproprietary NuScale Nonproprietary}}