ML24313A121

LLC - Response to NRC Request for Additional Information No. 020 (RAI-10150 R1) on the NuScale Standard Design Approval Application

ML24313A121
Person / Time
Site:	05200050
Issue date:	11/08/2024
From:	Shaver M NuScale
To:	Office of Nuclear Reactor Regulation, Document Control Desk
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ML24313A120	List: ML24313A121
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RAIO-175678
Download: ML24313A121 (1)

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RAIO-175678 NuScale Power, LLC 1100 NE Circle Blvd., Suite 200 Corvallis, Oregon 97330 Office 541.360.0500 Fax 541.207.3928 www.nuscalepower.com November 08, 2024 Docket No.52-050 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk One White Flint North 11555 Rockville Pike Rockville, MD 20852-2738

SUBJECT:

NuScale Power, LLC Response to NRC Request for Additional Information No. 020 (RAI-10150 R1) on the NuScale Standard Design Approval Application

REFERENCE:

1. NRC Letter to NuScale, Request for Additional Information No. 020 (RAI-10150 R1), dated March 09, 2024 The purpose of this letter is to provide the NuScale Power, LLC (NuScale) response to the referenced NRC Request for Additional Information (RAI).

The enclosure to this letter contains the NuScale response to the following RAI question from NRC RAI-10150 R1:

3.9.3-11 is the proprietary version of the NuScale Response to NRC RAI No. 020 (RAI-10150 R1, Question 3.9.3-11). NuScale requests that the proprietary version be withheld from public disclosure in accordance with the requirements of 10 CFR § 2.390. The enclosed affidavit (Enclosure 3) supports this request. Enclosure 1 has also been determined to contain Export Controlled Information. This information must be protected from disclosure per the requirement of 10 CFR § 810. Enclosure 2 is the nonproprietary version of the NuScale response.

This letter makes no regulatory commitments and no revisions to any existing regulatory commitments.

If you have any questions, please contact Elisa Fairbanks at 541-452-7872 or at efairbanks@nuscalepower.com.

I declare under penalty of perjury that the foregoing is true and correct. Executed on November 08, 2024.

Sincerely, Mark W. Shaver Director, Regulatory Affairs NuScale Power, LLC

RAIO-175678 Page 2 of 2 11/08/2024 NuScale Power, LLC 1100 NE Circle Blvd., Suite 200 Corvallis, Oregon 97330 Office 541.360.0500 Fax 541.207.3928 www.nuscalepower.com Distribution:

Mahmoud Jardaneh, Chief New Reactor Licensing Branch, NRC Getachew Tesfaye, Senior Project Manager, NRC Prosanta Chowdhury, Senior Project Manager, NRC

NuScale Response to NRC Request for Additional Information RAI-10150 R1, Question 3.9.3-11, proprietary : NuScale Response to NRC Request for Additional Information RAI-10150 R1, Question 3.9.3-11, nonproprietary : Affidavit of Mark W. Shaver, AF-175679

RAIO-175678 NuScale Power, LLC 1100 NE Circle Blvd., Suite 200 Corvallis, Oregon 97330 Office 541.360.0500 Fax 541.207.3928 www.nuscalepower.com NuScale Response to NRC Request for Additional Information RAI-10150 R1, Question 3.9.3-11, proprietary

RAIO-175678 NuScale Power, LLC 1100 NE Circle Blvd., Suite 200 Corvallis, Oregon 97330 Office 541.360.0500 Fax 541.207.3928 www.nuscalepower.com NuScale Response to NRC Request for Additional Information RAI-10150 R1, Question 3.9.3-11, nonproprietary

Response to Request for Additional Information Docket: 052000050 RAI No.: 10150 Date of RAI Issue: 03/09/2024 NRC Question No.: 3.9.3-11 Regulatory Basis 10 CFR 50.55a(b), Use and conditions on the use of standards. Systems and components of boiling and pressurized water-cooled nuclear power reactors must meet the requirements of the ASME BPV Code and the ASME OM Code as specified in 10 CFR 50.55a(b).

Issue Section 3.9.3 of FSAR Chapter 3 discusses the structural integrity of pressure-retaining components, their supports, and core support structures that are designed to be consistent with the 2017 ASME Code,Section III Division 1, subject to limitations and modification in 10 CFR 50.55a(b)(1).

In Section 3.9.3, it is stated that the lower RPV section and upper RPV section are connected by flange connection. However, the upper RPV section is made of low alloy steel and lower RPV section is made of austenitic stainless steel with different material properties (e.g., thermal expansion coefficients, modulus of elasticities, etc.). Because of the differing materials, shearing stress would also need to be accounted for in estimating the total load to determine whether the bolting stress limit would be exceeded. At this time, the ASME Code closure Bolting stress limit in XIII-4000 does not address combined tension and shear in Service Levels A, B and C.

Requested Information Provide a summary of the inputs, assumptions, allowable stress limits, and results demonstrating that the upper-to-lower RPV flange bolted joint meets the ASME Section III stress limits, including consideration of the shear loading that results from differential thermal expansion. Make the analysis available for staff review and update the FSAR to clarify how the combined tension and shear for RPV closure bolts are accounted for and meet stress limits.

NuScale Nonproprietary NuScale Nonproprietary

NuScale Response:

Executive Summary The upper to lower reactor pressure vessel (RPV) flange bolted connection meets the American Society of Mechanical Engineers (ASME)Section III criteria. Thermal loadings, including differential thermal expansion, are considered in accordance with the ASME Section III criteria and the applicable load combinations. The cumulative usage factor (CUF) for fatigue is less than 1.0 for all locations. A full summary of Design, Test, and Service Levels A-D results are provided in Table 10, Table 11, and Table 12. The lowest ASME criteria margin is for bearing stress at the RPV closure mating surfaces at ((2(a),(c),ECI for a Service Level C event. The thermal expansion of the differing materials is insignificant due to similar coefficients of thermal expansion. The preliminary results demonstrate the limiting stresses are at the connection and are dominantly experienced at the flange mating surfaces, and not the closure studs for the connection. Since the analyses demonstrate the mating surfaces bear the stress, no sliding is expected at the connection. The ANSYS model completed for the flange connection and components include a comprehensive consideration of stresses including combined shear and normal stresses. Both normal and shear stresses are considered for all stress checks performed in the evaluation. For the bolts explicitly, shear stresses due to all loading mechanisms, including differential thermal expansion, are considered in the computation of stresses to meet the ASME Section III Mandatory Appendix XIII-4000 acceptance criteria. The FSAR accurately represents the RPV design, ASME requirements, and Appendix XIII-4000 acceptance criteria without modification. The comparison of the ANSYS model for the flange connection and a two-dimensional full axisymmetric model showed good correlation between resultant primary stress due to pressure and in some instances over predicts stress in comparison to the two-dimensional full axisymmetric model; therefore, it is concluded that the boundary conditions utilized in the seal analysis are valid. Model Geometry and Boundary Conditions Primary, primary plus secondary, and peak stresses are calculated using a threedimensional FEM (finite element model). Structural loading includes thermal, pressure, seismic, and appropriate interface mechanical loading. Primary plus secondary stress intensity range and NuScale Nonproprietary NuScale Nonproprietary

fatigue usage analysis evaluates limiting locations in accordance with Section III, Subarticle NB-3200 and Mandatory Appendix XIII of the 2017 Edition of the ASME Boiler and Pressure Vessel Code (BPVC). The calculation of fatigue usage considers the effects of light water reactor (LWR) environmentally assisted fatigue (EAF) in accordance with NRC RG 1.207 and NUREG/CR-6909, when applicable. Hand calculations are performed as an additional validation source for primary stresses for the lower RPV shell, the upper RPV shell, and the closure studs. NuScale Power, LLC analyzed the RPV lower sub-assembly, reactor coolant system (RCS) upper sub-assembly, and 4.250-4UNC closure stud components. Analysis focused on the flange area and portions of the shell near the flange for the RPV lower sub-assembly and the RCS upper sub-assembly. Analysis utilized two different 1/20th symmetric models. One model represented the flange with no alignment pin hole and two closure studs. The second model represented the flange with an alignment pin hole and two closure studs. These model simplifications allowed minimizing the mesh and computational time needed, while providing accurate results. Figure 1 shows both models that are analyzed. Primary plus secondary, thermal stress ratchet, and fatigue analysis utilized a 1/20th symmetric model with no alignment pin. NuScale Nonproprietary NuScale Nonproprietary

Figure 1: Simplified Models (( }}2(a),(c),ECI The upper RPV shell is made of SA-508 Grade 3 Class 2, the lower RPV shell is made of SA-965, FXM-19, and the closure studs are made of SB-637, Alloy 718. The 2017 ASME BPVC, Section II, Materials, Part D, Properties (customary) does not contain RPV cladding material 308L/309L properties. The analysis uses SA-240, Type 304 as the RPV cladding material because of the similarities in mechanical properties to 308L/309L. Tables 1 through Table 4 show the design stress intensity (Sm), yield strength (Sy), ultimate tensile strength (Su), and thermal expansion coefficients. NuScale Nonproprietary NuScale Nonproprietary

Table 1: Design Stress Intensity (Sm) Temperature ( F) SA-965, Grade FXM-19 (ksi) SA-508, Grade 3 Class 2 (ksi) SB-637, Alloy 718 (ksi) SA-240, Type 304 (ksi)1 100 33.3 30.0 50.0 20.0 200 33.1 30.0 48.0 20.0 300 31.4 30.0 46.9 20.0 400 30.4 30.0 46.1 18.6 500 29.7 30.0 45.6 17.5 600 29.2 30.0 45.1 16.6 650 29.0 30.0 45.0 16.2

1. SA-240, Type 304 material properties are used for 308L/309L cladding material Table 2: Yield Strength (Sy)

Temperature ( F) SA-965, Grade FXM-19 (ksi) SA-508, Grade 3 Class 2 (ksi) SB-637, Alloy 718 (ksi) SA-240, Type 304 (ksi)1 100 55.0 65.0 150.0 30.0 200 47.1 61.2 144.0 25.0 300 43.3 59.1 140.7 22.4 400 40.7 57.5 138.3 20.7 500 38.8 56.1 136.8 19.4 600 37.4 54.7 135.3 18.4 650 36.8 53.9 134.9 18.0

1. SA-240, Type 304 material properties are used for 308L/309L cladding material NuScale Nonproprietary NuScale Nonproprietary

Table 3: Ultimate Tensile Strength (Su) Temperature ( F) SA-965, Grade FXM-19 (ksi) SA-508, Grade 3 Class 2 (ksi) SB-637, Alloy 718 (ksi) SA-240, Type 304 (ksi)1 100 100.0 90.0 185.0 75.0 200 99.4 90.0 177.6 71.0 300 94.2 90.0 173.5 66.2 400 91.1 90.0 170.6 64.0 500 89.1 90.0 168.7 63.4 600 87.7 90.0 166.9 63.4 650 87.0 90.0 166.3 63.4

1. SA-240, Type 304 material properties are used for 308L/309L cladding material Table 4: Thermal Expansion Coefficients Temperature

( F) SA-508 Grade 3 Class 2 Thermal Expansion Coefficient (x10-6) (1/ F) SA-965 FXM-19 Thermal Expansion Coefficient (x10-6) (1/ F) 70 6.4 8.2 100 6.5 8.2 150 6.6 8.4 200 6.7 8.5 250 6.8 8.6 300 6.9 8.7 350 7.0 8.8 400 7.1 8.9 450 7.2 9.0 500 7.3 9.1 550 7.3 9.1 600 7.4 9.2 650 7.5 9.2 700 7.6 9.3 750 7.7 9.3 800 7.8 9.4 Mesh settings were consistent between the closure flange with no alignment pin model and the model with the alignment pin. The shell, closure studs, nuts, and O-ring regions of the model NuScale Nonproprietary NuScale Nonproprietary

had sweep meshing applied. The other components have no meshing method specified. The final mesh is a combination of tetrahedral and hex-dominant meshing. Figure 2 shows the final FEA model mesh. Figure 2: Full Model Mesh (( }}2(a),(c),ECI NuScale Nonproprietary NuScale Nonproprietary

Thermal Analysis Primary stress analysis applied a thermal condition of ((

}}2(a),(c),ECI, design temperature, to all components. No thermal stresses are included in the primary stress evaluation; the application of temperature is to ensure the correct moduli of elasticity is considered.

Transient thermal analysis applied time histories consistent with the design transients described in FSAR Section 3.9.1.1. When the containment is evacuated, radiation heat transfer applies to the outer surface of the RPV. The minimum pool temperature of ((

}}2(a),(c),ECI and an emissivity of

((

}}2(a),(c),ECI is used.

The FEA modeling software thermal transient analysis requires the material properties as inputs to the analysis, including the thermal expansion coefficient. Table 4 provides the thermal expansion coefficients. Structural Analysis The upper to lower RPV flanged bolted connection, including closure studs, are evaluated using the loads and the load combinations reported in Table 6 and 7, respectively, from the applicable ASME BPVC 2017, Section III criteria. The evaluation types that were performed to compute the stresses included classical engineering calculations (i.e., hand calculations) and finite element analyses. Figure 3, Figure 4, and Figure 5 display the pressure application locations considered in this evaluation. Pressures were applied to the internal surfaces of the RPV, including the inner mating surfaces of the flange highlighted in red in Figures 3 and 4. A gasket seating pressure of ((

}}2(a),(c),ECI is applied to the O-ring groves highlighted in red in Figure 5. An end cap pressure is also applied to the model to ensure that the appropriate axial pressure stress was considered in each of the evaluations.

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Figure 3: Internal Pressure Application (( }}2(a),(c),ECI NuScale Nonproprietary NuScale Nonproprietary

Figure 4: Inner Mating Surfaces (( }}2(a),(c),ECI Figure 5: Gasket Seating Pressure Faces (( }}2(a),(c),ECI NuScale Nonproprietary NuScale Nonproprietary

A frictional contact region applies a static coefficient of friction of (( }}2(a),(c),ECI to the mating surfaces of the upper and lower RPV flanges. Figure 6 shows the meshed mating faces. Figure 6: Frictional Mating Surfaces (( }}2(a),(c),ECI Frictionless supports were applied to the symmetry planes and a displacement constraint was applied to the top cut surface of the model as shown in Figure 7 and Figure 8, respectively. NuScale Nonproprietary NuScale Nonproprietary

Figure 7: Frictionless Supports at Symmetry Planes (( }}2(a),(c),ECI NuScale Nonproprietary NuScale Nonproprietary

Figure 8: Displacement Support (( }}2(a),(c),ECI The primary stress evaluations use the four pressures in Table 5. For other service level evaluations, the applicable pressure is defined as part of the transient time history in the evaluation. Table 5: Internal Surface Pressure (( }}2(a),(c),ECI NuScale Nonproprietary NuScale Nonproprietary

Key Assumptions Five key assumptions are used in the evaluation:

The effect of heat generation (i.e., the resultant temperature and thermal stress due to radiation from the core) is not included in this analysis. o Note, temperatures due to the individually defined thermal transients are considered.

The analysis assumes the gasket is a double O-ring configuration with a gasket seating pressure (( }}2(a),(c),ECI.

The analysis includes one pretension of 650 kips to the closure studs and it assumes the seal is adequately seated to preclude leakage. o Note, in accordance with the ASME RPV Design Specification all bolted joints shall be design to remain sealed. The ASME RPV Design Report will document satisfaction the requirement is met, and ITAAC allows the NRC to confirm closure.

Deadweight includes the RPV mass and total solid weights, which is equivalent to (( }}2(a),(c),ECI.

Design basis pipe break pipe whip, design basis pipe break jet impingement, and refueling loads are not considered. Inputs Table 6 reports the types of loads considered in the evaluation. Table 7 reports the associated load combinations for each ASME service level. Table 6: Pressure, Mechanical, and Thermal Loads Load Description P Pressure (internal or external), including test pressure DW Deadweight TH Thermal transient loads DFL Piping reaction loads due to dynamic fluid loads (water hammer, pipe break, valve actuation) SSE Safe-shutdown earthquake BLT Bolt loads L Lifting and handling loads NuScale Nonproprietary NuScale Nonproprietary

Table 7: ASME Load Combinations for Reactor Pressure Shell Plant Event Service Level Load Combinations(2) Allowable Limit Design Design P + DW + BLT +/- DFL +L(3) Design RPV Hydrostatic Test Test P + DW + BLT Test Normal Operating Transients A P + DW + BLT + TH +/- DFL A Refueling(1) P + DW + BLT + TH + L Continued Operating Transients B P + DW + BLT + TH +/- DFL B Normal Operation + Seismic P + DW + BLT + TH +/- SSE Fatigue RPV Depressurization C P + DW + BLT + TH +/- DFL C SG Tube Rupture Rod Ejection Accident D P + DW + BLT C RPV Depressurization + SSE P + DW + BLT +/- SSE +/- DFL D Pipe Breaks + SSE Notes: 1. Refueling loads are unavailable at this time, see Key Assumptions. The load combination for the normal operating transients bounds the refueling load combination for this preliminary evaluation. 2. BLT includes preload and gasket seating loads. DFL includes pipe break loads. 3. Lifting/handling loads are not currently available at this time The O-ring seals sit in a groove in the bolted connection flange. As the depth of the groove is smaller than the O-ring free height diameter, the seal compresses when the flange is bolted together to form the sealing contact surface. The nominal groove depth achieves a target compression ratio of ((

}}2(a),(c),ECI.

Allowable Stress Limits Table 8 provides the complete list of ASME BPVC acceptance criteria used in the analysis for the RPV pressure flange and shell components. Table 9 provides the acceptance criteria for the 4.250-4UNC closure studs. NuScale Nonproprietary NuScale Nonproprietary

ASME BPVC, 2017 Edition, Section II, Materials, Part D, Properties (customary) does not provide an ultimate tensile strength or a yield strength for (( }}2(a),(c),ECI at elevated temperatures. Three times the stress intensity (Sm) is used for the yield strength (Sy) and a reduced ratio yield strength is used for the ultimate strength (Su). ASME BPVC acceptance criteria for the closure studs are shown in Table 9. The tensioning region includes the region below the threaded region for the lower nut. The stress in this region is limited to 0.9Sy, or 0.9(3Sm) when 3Sm is substituted for Sy. Strength limits in the tensioning region are determined at maximum tensioning temperature. Stud stresses in the tensioning region may not exceed 0.9Sy. y in Table 8 is the maximum allowable range of thermal stress ST,a computed on an elastic basis divided by either the yield strength Sy or 1.5Sm, whichever is greater. NuScale Nonproprietary NuScale Nonproprietary

Table 8: ASME BPVC Acceptance Criteria for Reactor Pressure Flange and Shell Condition Category Limit ASME BPVC Subarticle Design Pm Sm XIII-3141, Table XIII-3110-1 PL 1.5(Sm) Level B Pm 1.1(Sm) XIII-3142, Table XIII-3110-1 PL 1.1(1.5)(Sm) Level A&B P + Q 3(Sm) XIII-3420 Thermal Ratchet Max[y'Sy or y1.5Sm] XIII-3430 CUF U<1.0 XIII-3520 Level C Pm Max [1.2(Sm) or Sy] XIII-3143, Table XIII-3110-1 Pm(2) Max [1.1(Sm) or 0.90(Sy)] PL Max [1.2(1.5)(Sm) or 1.5(Sy)] Level D Pm Min [2.4(Sm) or 0.7(Su)] XXVII-3210 Pm(3) 0.7(Su) XXVII-3210 PL 1.5 of Pm limit XXVII-3220 Test Pm 0.90(Sy) XIII-3600(b) Design, Test, Levels A, B, and C Average Bearing Sy XIII-3710(a) Design(1) Triaxial 4Sm XIII-3740(a) Level C Triaxial 4.8Sm XIII-3740(b) Note: 1. Design bounds Level A and B. 2. Ferritic steel pressure only load case. 3. Ferritic material only NuScale Nonproprietary NuScale Nonproprietary

Table 9: ASME BPVC Acceptance Criteria for Reactor Pressure 4.250-4UNC Closure Studs Condition Category Limit ASME BPVC Subarticle Design - Appendix E Average Stud Stress Sm E-1210(b) Level A&B Average Stud Stress Sy(1) XIII-4210 Maximum Stud Stress Sy(1) XIII-4220 CUF U<1.0 XIII-3520, XIII-4230 Level C Average Stud Stress Sy(1) XIII-4210 Maximum Stud Stress Sy(1) XIII-4220 Level D Average Stud Stress Min [0.7(Su) or Sy](1,2) XXVII-3610(b) Maximum Stud Stress Su(1,2) XXVII-3610(c) Notes: 1. 3Sm is used for Sy because Sy is not available at design temperature for (( }}2(a),(c),ECI. 2. A reduced yield strength is substituted for the ultimate tensile strength for the allowable Level D stress limits. NuScale Nonproprietary NuScale Nonproprietary

Results Figure 9, Figure 10, and Figure 11 display the locations that are considered in the evaluation of the upper to lower RPV flanged bolted connection, including closure studs. Table 10, Table 11, and Table 12 report the margins for the most limiting region for the applicable ASME Code criteria. The calculated stresses consider normal and shear stress due to the applied load. Results meet the applicable ASME Code criteria for the upper to lower reactor pressure vessel flange bolted connection. Table 10: Reactor Pressure Vessel Summary of Limiting Results (( }}2(a),(c),ECI NuScale Nonproprietary NuScale Nonproprietary

Figure 9: Upper Flange Stress Classification Line Locations (( }}2(a),(c),ECI NuScale Nonproprietary NuScale Nonproprietary

Figure 10: Reactor Pressure Vessel Closure Mating Surfaces (( }}2(a),(c),ECI Table 11: Reactor Pressure Vessel Fatigue Limiting Location Results (( }}2(a),(c),ECI NuScale Nonproprietary NuScale Nonproprietary

Figure 11: Stud Stress Classification Lines (( }}2(a),(c),ECI Table 12: Reactor Pressure Vessel Stud Service Summary of Results (( }}2(a),(c),ECI NuScale Nonproprietary NuScale Nonproprietary

Supplemental Results Information - Geometry The upper reactor pressure vessel flange is a cladded SA-508 Grade 3 Class 2 pressure vessel. Figure 12 displays images with relevant geometric features of the upper reactor pressure vessel flange. The upper reactor pressure vessel flange is simple (i.e., it is a flat surface). The lower reactor pressure vessel flange is a SA-965 Grade FXM-19 pressure vessel. Figure 13 displays images with relevant geometric features of the upper reactor pressure vessel flange. The lower reactor pressure vessel flange is complex (i.e., has the detailed machined regions for the seal interfaces and the mating surfaces). Figure 14 displays the reactor pressure vessel closure stud in detail. The closure stud includes a variety of features for lifting and engaging with tensioners. The stud is a 4.250-4 UNC 2A threaded region with a 4.250-inch center diameter section with no threads. Locking plates are attached to the upper reactor pressure vessel closure flange and engage with the upper reactor pressure vessel flange nut to ensure the closure stud is always located in the same location. Clearance between the outer diameter of the stud and the holes in the upper and lower flanges mitigates any contact between the inner surfaces of the through holes in the flanges and the outer diameter of the closure studs. NuScale Nonproprietary NuScale Nonproprietary

Figure 12: Upper Reactor Pressure Vessel Flange Geometric Details (( }}2,(a),(c),ECI NuScale Nonproprietary NuScale Nonproprietary

Figure 13: Lower Reactor Pressure Vessel Flange Geometric Details (( }}2,(a),(c),ECI NuScale Nonproprietary NuScale Nonproprietary

Figure 14: Reactor Pressure Vessel Flange Closure Stud, Nut, and Associated Hardware Geometric Details (( }}2,(a),(c),ECI NuScale Nonproprietary NuScale Nonproprietary

Supplemental Results Information - Bearing Stress Table 13 and Table 14 contain the maximum and minimum bearing stress results, respectively, for all Service Level Conditions as a function of time. Figure 15 displays the four bearing stress evaluation locations. The results consider both thermal and pressure loadings. Figure 15: Bearing Stress Locations (( }}2(a),(c),ECI NuScale Nonproprietary NuScale Nonproprietary

Table 13: Maximum Bearing Stress Results (( }}2(a),(c),ECI NuScale Nonproprietary NuScale Nonproprietary

(( }}2(a),(c),ECI NuScale Nonproprietary NuScale Nonproprietary

Table 14: Minimum Bearing Stress Results (( }}2(a),(c),ECI NuScale Nonproprietary NuScale Nonproprietary

(( }}2(a),(c),ECI NuScale Nonproprietary NuScale Nonproprietary

The maximum bearing stress at any of the four interface locations displayed in Figure 15 is for the inadvertent opening of a reactor safety valve transient at the mating surface interface location (see Table 13, maximum bearing stress equal to (( }}2(a),(c)). The minimum bearing stress at any of the four interface locations displayed in Figure 15 is for the inadvertent main steam isolation valve closure transient at the mating surface bearing interface location (see Table 14, minimum bearing stress equal to (( }}2(a),(c)). Each of the four interfaces exhibit bearing stresses for every transient condition at the contact location represented as a friction contact. Figure 16 and Figure 17 display the ANSYS contact status at the upper to lower RPV flange mating interface for the minimum and maximum bearing stress transient times, respectively. Sticking contact presents for both the minimum and maximum bearing stress transient times. For the minimum bearing stress time the sticking contact is inboard of the first seal, whereas, for the maximum bearing stress time the sticking contact is at nearly the entire mating surface in the seals region. NuScale Nonproprietary NuScale Nonproprietary

Figure 16: ANSYS Contact Status for Mating Surface Reactor Pressure Vessel Flange Interface for MC2 Transient for Time with Minimal Bearing Stress (( }}2(a),(c),ECI NuScale Nonproprietary NuScale Nonproprietary

Figure 17: ANSYS Contact Status for Mating Surface Reactor Pressure Vessel Flange Interface for RSV Transient for Time with Maximum Bearing Stress (( }}2(a),(c),ECI NuScale Nonproprietary NuScale Nonproprietary

Supplemental Results Information - Model Comparison The primary stress due to design pressure (2200 psi) generated at the stress classification lines (SCLs) for the Upper Flange Shell 1 and Lower Flange 1 locations, shown in Figure 18, are compared to results at identical locations from a full two-dimensional axisymmetric representation of the reactor pressure vessel represented in Figure 19. The results provided in the two-dimensional calculation are for a 1000 psi unit pressure case. Stress results are obtained at equivalent locations as those for the Upper Flange Shell 1 and Lower Flange 1 SCL locations are scaled to represent the design pressure (2200 psi) by multiplying the stress results by 2.2. Table 15 reports the stress results and percent difference between them. The results demonstrate good correlation between the full model and the model utilized in RPV closure flange evaluation. Figure 18: Stress Classification Lines at the Upper and Lower Shell (( }}2(a),(c),ECI NuScale Nonproprietary NuScale Nonproprietary

Figure 19: Stress Classification Lines at the Upper and Lower Shell for Two-Dimensional Axisymmetric Model (( }}2(a),(c),ECI NuScale Nonproprietary NuScale Nonproprietary

Table 15: Pressure Stress Comparison (( }}2(a),(c),ECI NuScale Nonproprietary NuScale Nonproprietary

Supplemental Results Information - Preload Computation Methodology The ASME reactor pressure vessel design specification defines multiple requirements associated with bolted locations with seals. Two of the reactor pressure vessel design specification requirements are:

Bolted joints shall be designed to remain sealed during all level A and B events. In this context, sealed means flange separation less than or equal to the elastic spring back capability of the seal.

The main closure flange shall include a leakage test path and connection port to permit a leakage test between concentric seals. The maximum diameter of the test port connection shall be restricted to a size such that any break is less than the 40 gallons per minute (gpm) makeup capacity of the RCS system. NuScale Nonproprietary Final computations of the closure flange preload incorporate information in an iterative process. ASME Design Reports finalize the information associated with flange closure as associated with these design functions of maintaining closure within acceptable stress limits. This includes generating minimal, nominal, and maximum preloads along with the operating capacity of tensioners to ensure the flange remains sealed during plant operations. Pressurized-water reactor (PWR) operating experience demonstrates there may be leakage past the first seal location. The limit of 40 gpm maintains a safe threshold of pressurization for the flange connection. In the event of leakage, the flange cannot move radially outward to such an extent that the through holes in the upper or lower reactor pressure vessel flanges would contact the outer diameter of the closure studs resulting in a challenge to the structural integrity of pressure boundary components. Conclusion The upper to lower reactor pressure vessel flange bolted connection meets the American Society of Mechanical Engineers Section III criteria. Considerations in accordance with the ASME Section III criteria include thermal loadings, including differential thermal expansion, and the applicable load combinations. The comprehensive consideration of stresses including combined shear and normal stresses for the flange connection and components provide assurance that the FSAR accurately represents the RPV design, ASME requirements, and Appendix XIII-4000 acceptance criteria without modification. NuScale Nonproprietary

RAIO-175678 NuScale Power, LLC 1100 NE Circle Blvd., Suite 200 Corvallis, Oregon 97330 Office 541.360.0500 Fax 541.207.3928 www.nuscalepower.com Affidavit of Mark W. Shaver, AF-175679

AF-175679 Page 1 of 2

NuScale Power, LLC AFFIDAVIT of Mark W. Shaver I, Mark W. Shaver, state as follows: (1) I am the Director of Regulatory Affairs of NuScale Power, LLC (NuScale), and as such, I have been specifically delegated the function of reviewing the information described in this Affidavit that NuScale seeks to have withheld from public disclosure, and am authorized to apply for its withholding on behalf of NuScale. (2) I am knowledgeable of the criteria and procedures used by NuScale in designating information as a trade secret, privileged, or as confidential commercial or financial information. This request to withhold information from public disclosure is driven by one or more of the following: (a) The information requested to be withheld reveals distinguishing aspects of a process (or component, structure, tool, method, etc.) whose use by NuScale competitors, without a license from NuScale, would constitute a competitive economic disadvantage to NuScale. (b) The information requested to be withheld consists of supporting data, including test data, relative to a process (or component, structure, tool, method, etc.), and the application of the data secures a competitive economic advantage, as described more fully in paragraph 3 of this Affidavit. (c) Use by a competitor of the information requested to be withheld would reduce the competitors expenditure of resources, or improve its competitive position, in the design, manufacture, shipment, installation, assurance of quality, or licensing of a similar product. (d) The information requested to be withheld reveals cost or price information, production capabilities, budget levels, or commercial strategies of NuScale. (e) The information requested to be withheld consists of patentable ideas. (3) Public disclosure of the information sought to be withheld is likely to cause substantial harm to NuScales competitive position and foreclose or reduce the availability of profit-making opportunities. The accompanying Request for Additional Information response reveals distinguishing aspects about the response by which NuScale develops its NuScale Power, LLC Response to NRC Request for Additional Information (RAI No. 10150 R1, Question 3.9.3-11) on the NuScale Standard Design Approval Application. NuScale has performed significant research and evaluation to develop a basis for this response and has invested significant resources, including the expenditure of a considerable sum of money. The precise financial value of the information is difficult to quantify, but it is a key element of the design basis for a NuScale plant and, therefore, has substantial value to NuScale. If the information were disclosed to the public, NuScales competitors would have access to the information without purchasing the right to use it or having been required to undertake a similar expenditure of resources. Such disclosure would constitute a misappropriation of NuScales intellectual property, and would deprive NuScale of the opportunity to exercise its competitive advantage to seek an adequate return on its investment. (4) The information sought to be withheld is in the enclosed response to NRC Request for Additional Information RAI 10150 R1, Question 3.9.3-11. The enclosure contains the designation Proprietary at the top of each page containing proprietary information. The information considered by NuScale to be proprietary is identified within double braces, (( }} in the document.

AF-175679 Page 2 of 2 (5) The basis for proposing that the information be withheld is that NuScale treats the information as a trade secret, privileged, or as confidential commercial or financial information. NuScale relies upon the exemption from disclosure set forth in the Freedom of Information Act (FOIA), 5 USC § 552(b)(4), as well as exemptions applicable to the NRC under 10 CFR §§ 2.390(a)(4) and 9.17(a)(4). (6) Pursuant to the provisions set forth in 10 CFR § 2.390(b)(4), the following is provided for consideration by the Commission in determining whether the information sought to be withheld from public disclosure should be withheld: (a) The information sought to be withheld is owned and has been held in confidence by NuScale. (b) The information is of a sort customarily held in confidence by NuScale and, to the best of my knowledge and belief, consistently has been held in confidence by NuScale. The procedure for approval of external release of such information typically requires review by the staff manager, project manager, chief technology officer or other equivalent authority, or the manager of the cognizant marketing function (or his delegate), for technical content, competitive effect, and determination of the accuracy of the proprietary designation. Disclosures outside NuScale are limited to regulatory bodies, customers and potential customers and their agents, suppliers, licensees, and others with a legitimate need for the information, and then only in accordance with appropriate regulatory provisions or contractual agreements to maintain confidentiality. (c) The information is being transmitted to and received by the NRC in confidence. (d) No public disclosure of the information has been made, and it is not available in public sources. All disclosures to third parties, including any required transmittals to NRC, have been made, or must be made, pursuant to regulatory provisions or contractual agreements that provide for maintenance of the information in confidence. (e) Public disclosure of the information is likely to cause substantial harm to the competitive position of NuScale, taking into account the value of the information to NuScale, the amount of effort and money expended by NuScale in developing the information, and the difficulty others would have in acquiring or duplicating the information. The information sought to be withheld is part of NuScales technology that provides NuScale with a competitive advantage over other firms in the industry. NuScale has invested significant human and financial capital in developing this technology and NuScale believes it would be difficult for others to duplicate the technology without access to the information sought to be withheld. I declare under penalty of perjury that the foregoing is true and correct. Executed on November 08, 2024. Mark W. Shaver}}