ML24346A300
| ML24346A300 | |
| Person / Time | |
|---|---|
| Site: | 05200050 |
| Issue date: | 12/11/2024 |
| From: | NuScale |
| To: | Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML24346A130 | List:
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| References | |
| LO-175762 | |
| Download: ML24346A300 (1) | |
Text
Response to SDAA Audit Question Question Number: A-15.6.5-14 Receipt Date: 01/08/2024 Question:
Based on the 11-13-2023 LOCA Spectrum Meeting (2023 10 11 Follow-up) response in eRR, the staff requests responses to the following questions which were not completely answers in the documents, and the necessary welding and material related information that was requested should be included in the SDAA460.
a)
The response that flatness requirements on flange face are appliable after welding, including the insert seal welds, does not provide the necessary information. The previous question requested to include the requirements for welding (which would include at least the use of a weld groove, welding process (including filler metal or justification for not using filler metal),
number of weld beads, and the minimum weld thickness in order to determine how it can impact the corrosion barrier and also impact the seating surface. This information should be included in the SDAA460 in addition to that the finish/contour requirements of the flange face is applicable after welding.
b)
The response did not address certified material test report (CMTR).Section III, NCA-3812 and NB-2610 allows a certificate of compliance in lieu of a CMTR. Therefore, the SDAA460 should be updated to specifically require a CMTR is required for the threaded inserts.Section III, NB-2130 and NCA-3862 allows a certificate of compliance in lieu of a CMTR for non-pressure boundary materials, including weld material used for the seal weld. Therefore, the SDAA460 should also be updated to specifically require a CMTR is required for the seal weld material. SDAA460 should be updated to require a CMTR for the threaded insert and seal weld material. Also, the document states that the material was changed from Type 304 to SA-193, Grade B8R. However, the SDA460, Revision 1 includes Type 304 as well as SA-193, Grade 8 Class1, Grade B8M Class 1, Grade B8R, and Grade B8S Carbide Solution Treated. Confirm which material will be used, taking into consideration question (a) above and include it in the SDAA 460. In addition, specify the filler metal material to be used for the threaded insert seal weld in the SDAA 460.
NuScale Nonproprietary NuScale Nonproprietary
Response
The original NuScale response was posted on February 26, 2024. The NRC provided feedback on March 22, 2024 and the feedback was discussed on a clarification call between NuScale and the NRC on April 8, 2024. Following the clarification, NuScale agreed to revise the response to provide supplemental information. The original response below is unchanged. The supplemental information is added at the end of the original response, beginning with the section labeled Supplemental Information Following April 8, 2024 Clarification Call.
a.
Details of the welding for the threaded insert seal welds will be determined later in accordance with the installers welding program. The seal weld of the threaded inserts is only for a corrosion barrier; the weld is not structural. Final Safety Analysis Report (FSAR) Section 3.6.2.7 is revised as shown in the attached markup to require final surface condition penetrant testing (PT) of the threaded insert seal welds. The PT will ensure that the seal welds form an adequate corrosion barrier for the threaded-flange connections of the reactor recirculation valves (RRVs) and reactor vent valves (RVVs) in the final condition after welding and after any subsequent material removal (e.g., machining) operations. FSAR Section 3.6.2.7 is also revised as shown in the attached markup to identify the flatness requirements after welding on the flange faces for these connections.
FSAR Table 5.2-3 identifies allowable weld filler material for the RPV in the category Weld Filler Metals for RPV and CRDM Support Structure, which would include the threaded insert seal weld. Therefore, the weld filler material, when specified, will be one of the stainless steel options identified in FSAR Table 5.2-3.
b.
The threaded inserts are Class 1 components and a Certified Material Test Report (CMTR) is required per ASME Section III, NB-2000. However, ASME Section III does allow a certificate of compliance in lieu of a CMTR. Therefore, FSAR Section 3.6.2.7 is revised as shown in the attached markup to require a CMTR to be provided for the threaded inserts as well as for the material for the threaded insert seal welds.
Regarding the material of the threaded inserts for the RVV and RRV connections, the information provided as a follow-up to the October 11, 2023 meeting identifies the material as NuScale Nonproprietary NuScale Nonproprietary
SA-193, Grade B8R for the Standard Design Approval Application (SDAA) for the US460. In the Design Certification Application (DCA) for the US600, the material was SA-479 Type 304. The rationale for the material change in the SDAA is that the new material provides higher strength to reduce the required threaded length of engagement. The specification for SA-193, Grade B8R for the threaded inserts is identified on drawing ED-121904, Revision 2, RPV Upper Hardware, that was previously provided in the electronic reading room (eRR) as part of the response to audit question A-15.6.5-3. SDAA FSAR Table 5.2-3 identifies allowable materials used for the reactor pressure vessel. A combined table entry for Threaded Inserts; Pipe Reducers: PZR Spray Nozzles lists allowable materials for these components as SA-479 (Type 304) and SA-193 (Grade 8 Class 1, Grade B8M Class 1, Grade B8R, and Grade B8S Carbide Solution Treated). Due to the table structure and the combined component listing, the table does not specifically identify the material of the threaded inserts, only the allowable options.
Because the SA-193, Grade B8R material identified for the threaded inserts on ED-121904 is also included in the list of allowable materials in FSAR Table 5.2-3, the drawing and the FSAR table are consistent. The specific filler material for the threaded insert seal weld is not identified in drawing ED-121904. As described in the response to part a above, FSAR Table 5.2-3 identifies allowable weld filler material for the RPV in the category Weld Filler Metals for RPV and CRDM Support Structure, which would include the threaded insert seal weld. Therefore, the weld filler material, when specified, will be one of the stainless steel options identified in FSAR Table 5.2-3.
Supplemental Information Following April 8, 2024 Clarification Call During the NRC review and approval of the Design Certification Application (DCA) of the US600, information about the seal weld was shown in a drawing that was provided to the NRC but not included in the FSAR. The portion of the DCA figure is shown in Figure 1 below, with highlights pertaining to the seal weld. NuScale does not have an equivalent figure for the US460 design for the Standard Design Approval Application (SDAA) available at this time. However, if the information shown in Figure 1 is sufficient to address the NRC concern regarding the seal weld configuration, NuScale can provide a US460 specific drawing in the electronic reading room in the future. The figure would not be included in the FSAR as it was not included in the FSAR for the DCA.
NuScale Nonproprietary NuScale Nonproprietary
((2(a),(c),ECI Subsequent to the original response, FSAR Table 5.2-3 was revised to separate PZR Spray Nozzles from the table row that also addresses Threaded Inserts. As a result, the current table row only contains Threaded Inserts and Pipe Reducers. The intended materials for these components are different. In addition, the materials for pipe reducers are already included in other table rows. Therefore, to clarify, the existing row of FSAR Table 5.2-3 is deleted and a new row is added as shown in the attached markup so that Threaded Inserts have their own row and are only associated with the SA-193 material. Markups of the affected changes, as described in the response, are provided below: NuScale Nonproprietary NuScale Nonproprietary
NuScale Final Safety Analysis Report Protection against Dynamic Effects Associated with Postulated Rupture of Piping NuScale US460 SDAA 3.6-31 Draft Revision 2 Audit Question A-15.6.5-13, Audit Question A-15.6.5-14 Augmented Examination Requirements Augmented examination requirements are applied to support the application of BTP 3-4 for exclusion of breaks at the bolted-flange connections for the RVVs and RRVs. A Certified Material Test Report is required for the threaded inserts and for the seal weld materials associated with these connections. Visual examination (VT-1) of the threaded inserts and seal welds is required prior to initial plant startup and is performed in accordance with the requirements of ASME Section XI, IWA-2211. In addition, inspection by penetrant testing (PT) of the final surface condition of the threaded insert seal welds is required and is performed in accordance with the requirements of ASME Section III, NB-2546. Flatness requirements on the flange faces of these connections are applicable after welding. Inservice Inspection Audit Question A-15.6.5-13 The BTP 3-4 B.1.(ii)(7) states that a 100 percent volumetric inservice examination of all pipe welds should be conducted during each inspection interval as defined in ASME Code, Section XI, IWA-2400. This requirement is addressed for the RVV and RRV bolting by providing augmented ISI requirements for these bolts that exceed the Code requirements. For inservice inspection, if the connection is disassembled during the interval, a UT inspection is performed on the bolts (Section 3.13.2). If the connection is not disassembled during the inspection interval, a volumetric inspection of the connection is performed in-place. Additionally, exceptions in the ASME code for flanged connections that allow only a sample of bolting to be inspected are not followed, and instead all flange bolts for all RVVs and RRVs are inspected during each inspection interval. Augmented ISI requirements are also applied to the threaded inserts associated with the RVV and RRV connections, including seal welds. If an RVV or RRV connection is disassembled during the interval, a visual (VT-1) examination is performed on the threaded inserts and seal welds associated with the connection and is performed in accordance with the requirements of ASME Section XI, IWA-2211. Threaded Fastener Design The applicable guidelines and recommendations in NUREG-1339 are applicable. Lubricants containing molybdenum sulfide are prohibited for pressure-retaining bolted joints including the RVV and RRV joints. Of the degradation mechanisms in NUREG-1339, only SCC could potentially affect RVV and RRV bolted joints. Alloy 718 is highly resistant to SCC in borated water. To further improve Alloy 718 SCC resistance, the solution treatment temperature range before precipitation hardening treatment is restricted to 1800 degrees F to 1850 degrees F. Additionally, the RRV bolting is submerged in borated water only during refueling, at a much lower temperature than RCS operating temperature, further reducing SCC susceptibility. The RVV bolting materials are not submerged in borated water
NuScale Final Safety Analysis Report Threaded Fasteners (American Society of Mechanical Engineers Code Class 1, 2, and 3) NuScale US460 SDAA 3.13-4 Draft Revision 2 Class 1, 2, and 3 threaded fasteners are retained in accordance with 10 CFR 50.71. 3.13.2 Inservice Inspection Requirements Audit Question A-15.6.5-13 Inservice Inspection for ASME Class 1, 2, and 3 threaded fasteners is in accordance with the ASME BPVC, Section XI (Reference 3.13-5), as required by 10 CFR 50.55a, except where specific written relief is granted by the Nuclear Regulatory Commission. or where augmented inspection requirements that exceed the ASME Code requirements are specified. COL Item 3.13-1: An applicant that references the NuScale Power Plant US460 standard design will provide an inservice inspection program for American Society of Mechanical Engineers Class 1, 2, and 3 threaded fasteners. The program will identify the applicable edition and addenda of American Society of Mechanical Engineers Boiler and Pressure Vessel Code Section XI and ensure compliance with 10 CFR 50.55a. 3.13.3 References 3.13-1 American Society of Mechanical Engineers, Boiler and Pressure Vessel Code, 2017 edition, Section III, Rules for Construction of Nuclear Facility Components, New York, NY. 3.13-2 American Society of Mechanical Engineers, Boiler and Pressure Vessel Code, 2017 edition, Section II, Materials, New York, NY. 3.13-3 McIlree, A.R., Degradation of High Strength Austenitic Alloys X-750, 718 and A286 in Nuclear Power Systems, Proceedings of the 1st International Symposium on Environmental Degradation of Materials in Nuclear Power Systems - Water Reactors, National Association of Corrosion Engineers, 1984. 3.13-4 U.S. Nuclear Regulatory Commission, Resolution of Generic Safety Issue 29: Bolting Degradation or Failure in Nuclear Power Plants, NUREG-1339, June 1990. 3.13-5 American Society of Mechanical Engineers, Boiler and Pressure Vessel Code, 2017 edition, Section XI, Rules for Inservice Inspection of Nuclear Power Plant Components, New York, NY.
NuScale Final Safety Analysis Report Integrity of Reactor Coolant Boundary NuScale US460 SDAA 5.2-31 Draft Revision 2 Audit Question A-4.5.1-3, Audit Question A-5.4-1, Audit Question A-5.4-3, Audit Question A-15.6.5-14 Table 5.2-3: Reactor Coolant Pressure Boundary Component and Support Materials Including Reactor Vessel, Attachments, and Appurtenances Component Specification Grade, Class, or Type Reactor Pressure Vessel Lower Vessel (Lower Head, Shell and Flange) SA-965 FXM-191 Upper Vessel (Flange, Shells including PZRIntegral Steam Plenum Baffle Plate, Upper Head, Steam Plenum and Feed Plenum Access Ports) SA-508 Grade 3 Class 2 SG Tubes SB-163 UNS N06690 Nozzles (Thermowells, Level SensorsRTD Interface, Flow Sensor Interface, Pressure Taps); Steam Plenum Caps SB-166 SB-564 UNS N06690 UNS N06690 Steam Plenum Caps SB-166 SB-168 UNS N06690 UNS N06690 CNV-RPV Lateral Support Lugs; CNV-RPVRPV-CNV Support Ledges Assemblies, Support Ledge Assembly Vertical and Horizontal Shims SB-168 SB-564 UNS N06690 UNS N06690 RPV Seismic Cap SA-693 Type 630, H1100 Safe -Ends, PZR Baffle Plate Bore Sleeves, Upper SG Supports SA-182Pressure-retaining material shall conform to the requirements of one of the specifications for material given in Tables 2A and 2B of ASME BPVC, Section II, Part D, Subpart 1. Type 304F3042 Integral Steam Plenum Bore Sleeves SA-240 Type 3042 Covers for Steam Plenum Access Ports Covers for Feed Plenum Access Ports SA-182Pressure-retaining material shall conform to the requirements of one of the specifications for material given in Tables 2A and 2B of ASME BPVC, Section II, Part D, Subpart 1. Type 304F3042 FXM-19FXM-19 SA-240 Type 3042 FXM-191 LeakClosure Flange Test Ports SA-312 TP316 SMLS2 PZR Heater Bundle Flange SB-168 UNS N06690 PZR Heater Element End Plug SA-479 Type 3042 PZR Heater Element Sheath SA-213 TP3162 Threaded Inserts; Pipe Reducers; PZR Spray Nozzles SA-479 Type 3042
NuScale Final Safety Analysis Report Integrity of Reactor Coolant Boundary NuScale US460 SDAA 5.2-32 Draft Revision 2 Threaded Inserts SA-193 Grade 8 Class 1 Grade B8M Class 1 Grade B8R Grade B8S Carbide Solution Treated Nameplates ASME or ASTM Type 304 Instrument Seal Assembly (ISA) Flange SA-240 Type 304, 304L, 316, 316L (Note 2) ISA Fittings SA-479 Type 316, 316L (Note 2) ISA Studs and Nuts SB-637 UNS N07718 (Note 3) RPV Bolting Main Flange Closure SB-637 UNS N077183 Other Than Main Flange Closure SA-193 Grade B8 Class 1, Grade B8R, Grade B8M Class 1 SA-194 Grade 8 SB-637 UNS N077183 SA-564 Type 630, H1100 RPV Alignment Pins SA-564 or A-564 Type 630, H1100 RPV Lock Plates ASME or ASTM Type 304 CRDM Support Structure Supports SA-240 Type 3042 SA-479 Type 3042 Bolting SA-564 Type 630, H1100 CRDM Pressure Retaining Components CRDM Pressure Housing SA-182 F304 or F304LN2 SA-965 F304LN2 Top Plug Components SA-479 Type 3042 Type 410 Austenitic Stainless Steel Weld Filler Metals SFA-5.4 E3084, E308L, E309L, E316, E316L SFA-5.9 ER3084, ER308L, ER309L, ER316, ER316L4 Weld Filler Metals for RPV and CRDM Support Structure Low-Alloy Steel Weld Filler Metals SFA-5.5 E90XX-X SFA-5.23 F9XX-EXX-XX or F10XX-EXX-XX SFA-5.28 ER90S-X SFA-5.29 E9XTX-XX or E10TX-XX 2XX Austenitic Stainless Steel Weld Filler Metals SFA-5.4 E209, E2401 SFA-5.9 ER209, ER2401 3XX Austenitic Stainless Steel Weld Filler Metals (include filler metals for weld-overlay cladding) SFA-5.4 E308, E308L, E309, E309L, E316, E316L4 SFA-5.9 ER308, ER308L, ER309, ER309L, ER316, ER316L, EQ308L, EQ309L4 SFA-5.22 E308, E308L, E309, E309L, E316, E316L, E308TX, E308LTX, 316TX, 316LTX4 Nickel-Base Alloy Weld Filler Metals SFA-5.11 ENiCrFe-7, ENiCrFe-13 SFA-5.14 ERNiCrFe-7, ERNiCRFE-7A, EQNiCrFe-7, EQNiCrFe-7A, ERNiCrFe-13, EQNiCrFe-13 Table 5.2-3: Reactor Coolant Pressure Boundary Component and Support Materials Including Reactor Vessel, Attachments, and Appurtenances (Continued) Component Specification Grade, Class, or Type}}