ML24346A299
| ML24346A299 | |
| 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: ML24346A299 (1) | |
Text
Response to SDAA Audit Question Question Number: A-15.6.5-13 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 inspection information that was requested should be included in the SDAA460.
a)
Document states inspection during construction of the threaded insert seal weld will be visual examination, but this inspection is not specified in SDAA460. Therefore, this should be included in SDAA460, and include the inspection acceptance criteria. In addition, the document also states that inservice inspection in the DCA was removed from SDAA460 because it is not required by code and the weld is non-structural. However, the NRC staff notes that the threaded insert is a different material (high strength stainless steel with carbide solution treatment) that when welded could be more susceptible to stress corrosion cracking. In addition, the threaded insert provides a corrosion barrier for the reactor vessel head, and the weld and the affected threaded insert material will have an increase susceptibility to degradation. Therefore, this inservice inspection of the threaded insert seal weld should be included in the SDAA 460 to determine that the structural integrity of the threaded insert weld has been maintained. Also, the construction inspection and the inservice inspection of the threaded insert was not provided as requested, but the staff notes that the information provided for the weld of the threaded insert should also apply to the threaded insert because the basis for the inspection also applies to the threaded insert. Therefore, the inspection method, frequency and inspection criteria should be provided and included in SDAA460.
b)
Your response to the question on augmented inservice inspection of the bolts states that Section 3.6.2.7 of SDAA460 sets the augmented inservice inspection regardless of whether the information is also included in Section 3.13 and Chapter 5 of SDAA460. However, the NRC staff notes that Section 3.6.2.7 of SDAA460 specifies that the augmented ultrasonic testing of NuScale Nonproprietary NuScale Nonproprietary
bolts is in accordance with paragraph 3.13.2 of SDAA460. Therefore, if there is no augmented inservice inspection in Section 3.13, then it can be interpreted that augmented is not required. In addition, Section 3.6 of the SDAA460 does not provide the inspection requirements, because inspections are typically specified in Section 3.13 and/or Chapter 5 of SDA460. Without this augmented inspection in these chapters, the augmented inspection may be lost when developing the inservice inspection program. Therefore, the required augmented inservice inspection of the bolting should be provided in a coherent manner in an appropriate section of the SDAA 460 which should include the inspection method, frequency, and acceptance criteria.
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.
Consistent with the approach used in the Design Certification Application (DCA) of the US600, the Standard Design Approval Application (SDAA) for the US460 is revised as shown in the attached markup to add augmented requirements for inspection of the threaded inserts and the threaded insert seal welds associated with the reactor vent valve (RVV) and reactor recirculation valve (RRV) connections. The augmented requirements consist of visual examination (VT-1) of the threaded inserts and seal welds associated with an RVV or RRV connection if the connection is disassembled during the inservice inspection interval.
Corresponding preservice inspections will also be performed. Final Safety Analysis Report (FSAR) Section 3.6.2.7 is revised as shown in the attached markup to include these augmented requirements. As described further in the response to part b below, inclusion of augmented requirements in one section of the FSAR (Section 3.6.2.7 in this case) is adequate; repetition of the requirements elsewhere is not required.
NuScale Nonproprietary NuScale Nonproprietary
b.
The discussion in the Inservice Inspection part of Section 3.6.2.7, as revised in this response, includes the augmented requirements that are applied to the connections of the RVVs and RRVs to the reactor vessel. The discussion of augmented requirements currently includes a cross-reference to Section 3.13.2. However, Section 3.13.2 does not contain any discussion of the augmented requirements that are applied to the connections of the RVVs and RRVs to the reactor vessel. Rather, Section 3.13.2 provides general information about Inservice Inspection Requirements. Therefore, to prevent confusion, NuScale is deleting the cross-reference to Section 3.13.2 from Section 3.6.2.7 as shown in the attached markup.
The current discussion in Section 3.13.2 identifies that inspection of threaded fasteners will be in accordance with ASME requirements. Although this is correct, there are instances where additional augmented requirements are applied that exceed the ASME requirements. Section 3.6.2.7 is an example of where augmented requirements are applied. Therefore, to prevent confusion, NuScale is revising Section 3.13.2 as shown in the attached markup to identify that augmented inspection requirements that exceed ASME requirements are applied in some cases. The specific cases are not identified in Section 3.13.2, but are specified elsewhere in the FSAR, like in Section 3.6.2.7 described above. It is not necessary for Section 3.13.2 to provide a cross-reference back to Section 3.6.2.7 or to repeat the augmented requirements. It is sufficient that the augmented requirements be described at least once in the FSAR (as is done in Section 3.6.2.7).
The clarification to Section 3.13.2 to identify that augmented requirements exist in general is adequate to address the NRC concern that the augmented requirements not be missed when developing the inservice inspection program as required by COL Item 3.13-1. It is ultimately the responsibility of the COL applicant to ensure that all FSAR requirements, regardless of numerical section they are contained within, are appropriately reflected in the inservice inspection program.
NuScale Nonproprietary NuScale Nonproprietary
Supplemental Information Following April 8, 2024 Clarification Call Note that the augmented requirements to be applied are dependent on whether or not the RVV and RRV connections are disassembled during the inspection interval. Disassembly of connections is based on the need to access the associated valves and is therefore performed per the following:
Valve manufacturer recommendations
Requirements of the inservice testing program required by COL Item 3.9-8 If issues are identified during inspections, whether the inspections are those performed with or without disassembly, the licensees corrective action program (CAP) required by 10 CFR 50 Appendix B would require evaluation of the condition, including assessment of extent of condition. Through this formal process, a single inspection can generate inspection scope expansion and additional recurring inspection requirements.
Note that during the deep dive meeting to discuss bolted connections on May 7 and 8, 2024, in Rockville, Maryland, NuScale proposed inspections of threaded inserts and seal welds of other connections that are disassembled each inspection interval (e.g., feedwater and main steam plenum access covers are regularly removed to support steam generator inspections). The inspections for these other bolted connections in a similar environment will allow for any conditions to be identified that may impact the RVV and RRV connections even if the RVV and RRV connections themselves are not regularly disassembled. The proposed inspections for other connections are outside the scope of this audit question.
The preservice and inservice inspection visual examination (VT-1) is to be performed according to the criteria in ASME Section XI, IWA-2211. Penetrant testing (PT) during fabrication is to be performed according to the criteria in ASME Section III, NB-2546. Identification of the specific ASME references is added to the FSAR as shown in the attached markup.
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