ML17345B219
| ML17345B219 | |
| Person / Time | |
|---|---|
| Site: | NuScale |
| Issue date: | 12/11/2017 |
| From: | Rad Z NuScale |
| To: | Document Control Desk, Office of New Reactors |
| References | |
| RAIO-1217-57599 | |
| Download: ML17345B219 (10) | |
Text
RAIO-1217-57599 December 11, 2017 Docket No.52-048 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.
253 (eRAI No. 9184) on the NuScale Design Certification Application
REFERENCE:
U.S. Nuclear Regulatory Commission, "Request for Additional Information No.
253 (eRAI No. 9184)," dated October 13, 2017 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 NuScale's response to the following RAI Questions from NRC eRAI No. 9184:
06.01.01-8 06.01.01-9 This letter and the enclosed response make no new regulatory commitments and no revisions to any existing regulatory commitments.
If you have any questions on this response, please contact Marty Bryan at 541-452-7172 or at mbryan@nuscalepower.com.
Sincerely, Z ckary W. Rad Za Zackary Director Regulatory Affairs
- Director, NuScale Power, LLC Distribution: Gregory Cranston, NRC, OWFN-8G9A Omid Tabatabai, NRC, OWFN-8G9A Samuel Lee, NRC, OWFN-8G9A : NuScale Response to NRC Request for Additional Information eRAI No. 9184 NuScale Power, LLC 1100 NE Circle Blvd., Suite 200 Corvalis, Oregon 97330, Office: 541.360.0500, Fax: 541.207.3928 www.nuscalepower.com
NuScale Response to NRC Request for Additional Information eRAI No. 9184 NuScale Power, LLC 1100 NE Circle Blvd., Suite 200 Corvalis, Oregon 97330, Office: 541.360.0500, Fax: 541.207.3928 www.nuscalepower.com
Response to Request for Additional Information Docket No.52-048 eRAI No.: 9184 Date of RAI Issue: 10/13/2017 NRC Question No.: 06.01.01-8 Regulatory Basis:
Appendix A, General Design Criteria for Nuclear Power Plants, to Title 10 of the Code of Federal Regulations (10 CFR) Part 50, Domestic Licensing of Production and Utilization Facilities, General Design Criteria (GDC) 1, requires that structures, systems, and components (SSCs) important to safety shall be designed, fabricated, erected, and tested to quality standards commensurate with the importance of the safety functions to be performed.
GDC 4, Environmental and dynamic effects design bases, requires that SSCs important to safety shall be designed to accommodate the effects of and to be compatible with the environmental conditions associated with normal operation, maintenance, testing, and postulated accidents, including loss-of-coolant accidents (LOCAs).
GDC 14, Reactor coolant pressure boundary, requires that the reactor coolant pressure boundary (RCPB) shall be designed, fabricated, erected, and tested so as to have an extremely low probability of abnormal leakage, of rapidly propagating failure, and of gross rupture.
GDC 31, Fracture prevention of reactor coolant pressure boundary, requires that the RCPB shall be designed with sufficient margin to assure that when stressed under operating, maintenance, testing, and postulated accident conditions (1) the boundary behaves in a nonbrittle manner and (2) the probability of rapidly propagating fracture is minimized.
Applicant PDC 35, Emergency core cooling, requires a system to provide abundant emergency core cooling. The system safety function shall be to transfer heat from the reactor core following any loss of reactor coolant at a rate such that (1) fuel and clad damage that could interfere with continued effective core cooling is prevented and (2) clad metal-water reaction is limited to negligible amounts.
10 CFR Part 50, Appendix B, Criteria IX, Control of Special Processes, and XIII, Handling, Storage, and Shipping, require establishing measures to: (1) assure that special processes are controlled and accomplished in accordance with applicable codes, standards, specifications, criteria, and other special requirements; and (2) control cleaning of material and equipment in accordance with work and inspection instructions to prevent damage or degradation.
NuScale Nonproprietary
DCD Tier 2, FSAR, Section 6.1.1.1 states that the pressure-retaining bolting and stud materials
for connection of the upper and lower containment vessel (CNV) shell flanges, top head, and
reactor pressure vessel (RPV)-to-CNV support ledge shell are fabricated out of Alloy 718.
The supplement to DCD Tier 2, FSAR, Section 3.13 dated August 10, 2017 [ADAMS
ML17222A218] states that all uses of Alloy 718 receive the same heat treatment and that this
heat treatment will mitigate stress corrosion cracking (SCC). However, DCD Tier 2, FSAR,
Section 6.1.1 does not reference Section 3.13.
Revise DCD Tier 2, FS$5, Section 6.1.1 to reference Section 3.13 related to the Alloy 718
threaded fastener design requirements for the mitigation of SCC.
NuScale Response:
NuScale uses Alloy 718 for both RPV and CNV vessel closure bolting with identical heat treatment. Section 3.13.1.1 discusses RG 1.65 with respect of its applicability to Alloy 718 RPV vessel closure bolting.
RG 1.65 states: "This regulatory guide provides guidance for use in selecting reactor vessel closure stud bolting materials and properties, conducting a preservice inspection, and conducting an ISI."
Because NuScale CNV is not a reactor pressure vessel, RG 1.65 is not applicable to any bolting for CNV. The reference to RG 1.65 in Section 6.1.1.1 and the reference to Section 6.1 in RG 1.65 portion of Table 1.9-2 is incorrect and the FSAR is revised accordingly.
Impact on DCA:
FSAR Section 6.1 and Table 1.9-2 have been revised as described in the response above and as shown in the markup provided in this response.
NuScale Nonproprietary
Response to Request for Additional Information Docket No.52-048 eRAI No.: 9184 Date of RAI Issue: 10/13/2017 NRC Question No.: 06.01.01-9 DCD Tier 2, FSAR, Table 1.9-2, Conformance with Regulatory Guides, states that RG 1.65, Materials and Inspections for Reactor Vessel Closure Studs, is applicable to Section 6.1, which describes the containment vessel (CNV). The CNV closure studs are part of the CNV and also described in Section 6.1.
The supplement to the DCD dated July 11, 2017 [ADAMS ML17192A869] revises DCD Tier 2, FSAR, Section 6.1.1.1 to state that the concerns addressed by RG 1.65, Revision 1, Position 2(b) do not apply to Alloy 718 due to its resistance to general corrosion. As written, this sentence is unclear since it does not refer to the specific CNV closure studs. There are other threaded fasteners that are manufactured out of Alloy 718 that are used within the CNV. Furthermore, the proposed wording of Section 6.1.1.1 does not address the applicability of the remaining positions of RG 1.65 to the Alloy 718 CNV closure studs.
Revise DCD Tier 2, FSAR, Section 6.1.1 to discuss all of the applicable positions of RG 1.65, Revision 1, for the specific CNV closure studs.
NuScale Response:
NuScale uses Alloy 718 for both RPV and CNV closure bolting with identical heat treatment.
Section 3.13.1.1 discusses RG 1.65 with respect of its applicability to Alloy 718 RPV vessel closure bolting.
RG 1.65 applies to "reactor vessel closure stud bolting". The NuScale CNV is not a reactor pressure vessel, therefore RG 1.65 is not applicable to any bolting for CNV and the reference to RG 1.65 in Section 6.1.1.1 and the reference to Section 6.1 in RG 1.65 portion of Table 1.9-2 is incorrect and the FSAR is revised accordingly.
However, the NuScale CNV is designed and fabricated as a Class 1 vessel and therefore the containment vessel closure stud bolting materials and properties, pre-service and in-service inspection meets all ASME code requirements that are applied to other Class 1 vessels (e.g.
reactor vessels). Design considerations in FSAR for Class 1 threaded fastener components, NuScale Nonproprietary
except those specifically addressing RG 1.65 compliance for RPV studs, nuts and washers, are applicable to the CNV closure bolting. FSAR Section 3.13 is revised to delete the last sentence of first paragraph, in order to make it clear that CNV fasteners are within the scope or requirements of Section 3.13.
Impact on DCA:
FSAR Section 3.13 has been revised as described in the response above and as shown in the markup provided in this response.
NuScale Nonproprietary
Tier 2 NuScale Final Safety Analysis Report RAI 02.03.01-5, RAI 05.02.03-13, RAI 05.03.01-3, RAI 06.01.01-8, RAI 06.01.01-9, RAI 08.01-1, RAI 08.01-1S1, RAI 08.02-4, RAI 08.02-6, RAI 08.03.02-1, RAI 09.02.06-1 Table 1.9-2: Conformance with Regulatory Guides RG Division Title Rev. Conformance Sta- COL Applicabil- Comments Section tus ity 1.3 Assumptions Used for Evalu- 2 Not Applicable Not Applicable This guidance is only applicable to BWRs. Not Applicable ating the Potential Radiologi-cal Consequences of a Loss of Coolant Accident for Boiling Water Reactors 1.4 Assumptions Used for Evalu- 2 Not Applicable Not Applicable This RG pertains to existing reactors; RG 1.183 Not Applicable ating the Potential Radiologi- is specified in SRP Section 15.0.3 to be used for cal Consequences of a Loss of new reactors.
Coolant Accident for Pressur-ized Water Reactors 1.5 Safety Guide 5 - Assumptions - Not Applicable Not Applicable This guidance is only applicable to BWRs. Not Applicable Used for Evaluating the Potential Radiological Conse-quences of a Steam Line 1.9-5 Break Accident for Boiling Water Reactors 1.6 Safety Guide 6 - Indepen- - Partially Conforms Applicable The onsite electrical AC power systems do not 8.3 dence Between Redundant contain any Class 1E distribution systems. The Standby (Onsite) Power EDSS design conforms to the guidance for Sources and Between Their independence of standby power sources and Distribution Systems their distribution systems.
1.7 Control of Combustible Gas 3 Not Applicable Not Applicable The containment vessel design is such that its 6.2 Concentrations in Contain- integrity does not rely on combustible gas Conformance with Regulatory Criteria ment control systems.
1.8 Qualification and Training of 3 Not Applicable Applicable Site-specific programmatic and operational Not Applicable Personnel for Nuclear Power activities are the responsibility of the COL Plants applicant.
1.9 Application and Testing of 4 Not Applicable Not Applicable Based on reduced reliance on AC power, the 8.3 Safety-Related Diesel Genera- design does not require or include safety-tors in Nuclear Power Plants related emergency diesel generators.
Draft Revision 1 1.11 Instrument Lines Penetrating 1 Not Applicable Not Applicable No lines penetrate the NPM containment. 6.2 the Primary Reactor Contain-ment
Table 1.9-2: Conformance with Regulatory Guides (Continued)
Tier 2 NuScale Final Safety Analysis Report RG Division Title Rev. Conformance Sta- COL Applicabil- Comments Section tus ity 1.60 Design Response Spectra for 2 Not Applicable Not Applicable The Certified Seismic Design Response Spectra 3.7 Seismic Design of Nuclear (CSDRS) was not developed using RG 1.60.
Power Plants However, it is demonstrated that the design envelops the RG 1.60 spectra anchored to 0.1g.
1.61 Damping Values for Seismic 1 Conforms Applicable In accordance with the guidance of RG 1.61, an 3.7 Design of Nuclear Power alternative damping value for the NPM sub- 3.12 Plants structure was determined. The NPM subsys-Appendix 3A tem is comprised of vessels, bearing joints, cables, internals, friction surfaces, etc. 5.3 1.62 Manual Initiation of Protec- 1 Conforms Applicable This RG refers to Point 4 of BTP 7-19, Revision 7.1 tive Actions 5, dated March 2007. NuScale intends to apply 7.2 BTP 7-19, Revision 6 (including Point 4).
1.63 Electric Penetration Assem- 3 Partially Conforms Applicable IEEE 741-1997 is used for external circuit pro- 3.113.8.2 blies in Containment Struc- tection of electrical penetration assemblies. 3.11 tures for Nuclear Power Plants Although IEEE 741-1997 is not endorsed by RG 8.1 1.63 (endorsing IEEE 317-1983) the design phi-8.3 1.9-14 losophy does not deviate from RG 1.63.The portion of the RG 1.63 guidance that endorses IEEE-317-1983 is applicable. IEEE 741-1997 is used for external circuit protection of electrical penetration assemblies instead of IEEE 741-1986 as endorsed by RG 1.63. The 1997 version, including the additional design enhancements, is consistent with RG 1.63.
1.65 Materials and Inspections for 1 Partially Conforms Applicable This RG provides guidance for use in selecting 3.13 Conformance with Regulatory Criteria Reactor Vessel Closure Studs reactor vessel closure stud bolting materials 5.3 and properties, and conducting preservice and 6.1 inservice inspection of the closure studs. Per-formance of inservice inspection is the respon-sibility of the COL applicant. The reactor pressure vessel (RPV) bolting material uses SB-637 UNS N07718 (alloy 718). Because of the Draft Revision 1 material properties of alloy 718, the concerns addressed by RG 1.65 Positions 1(a)(i) and 2(b) do not apply to the RPV bolting material. Refer to Section 3.13.1.1.
NuScale Final Safety Analysis Report Threaded Fasteners (ASME Code Class 1, 2, and 3) 3.13 Threaded Fasteners (ASME Code Class 1, 2, and 3)
RAI 06.01.01-8, RAI 06.01.01-9 This section addresses the application of the American Society of Mechanical Engineers (ASME)
Boiler and Pressure Vessel Code (BPVC),Section III, Division 1 (Reference 3.13-1), to the design of Class 1, 2, and 3 pressure-retaining threaded fasteners. Threaded fasteners and bolted connections, herein called threaded fasteners unless specified differently, include the bolts, studs, nuts, and washers that are associated with Class 1, 2, and 3 pressure retaining joints.
Fasteners used for the containment vessel (CNV) are addressed in Section 6.1.
The selection, design, fabrication, installation and inspection of threaded fasteners in the Class 1, 2 and 3 systems meet the criteria of 10 CFR 50.55a, including 10 CFR 50.55a(b)(4). There are no , which permits the use of code cases per Regulatory Guide (RG) 1.84 Revision 36 used in the design of threaded fasteners in Class 1, 2, and 3 systems.
The threaded fastener design complies with General Design Criteria (GDCs) 1, 4, 14, 30 and 31.
Further discussion of compliance with the GDCs are provided in this section.
- GDCs 1 and 30 require that structures, systems, and components (SSC) be designed to quality standards commensurate with the importance of the safety function to be performed. GDCs 1 and 30 are met as the bolting design is in conformance with the criteria of ASME BPVC,Section III and RG 1.65 Revision 1 as described below.
- GDC 4 requires that SSC accommodate the effects of, and that they are compatible with, the environmental conditions of normal and accident conditions. GDC 4 is met by protecting the ASME Class 1, 2, and 3 threaded fasteners from the adverse impacts from lubricants and sealants and by using stainless steels or nickel-base alloys that are resistant to boric acid corrosion.
- GDC 14 is met by designing the threaded fasteners to ASME Class 1 criteria.
- GDC 31 is met by conformance with the requirements of 10 CFR 50, Appendix G, which establishes fracture toughness requirements. Thus the probability of a rapid fracture of the threaded fasteners is minimized satisfying the requirements of GDC 31.
10 CFR 50, Appendix B, Criterion XIII, requires that measures be established to control the cleaning of material and equipment to prevent damage or deterioration. RG 1.28 Revision 4 provides quality assurance criteria for cleaning fluid systems and associated components that comply with 10 CFR 50 Appendix B. The design for threaded fasteners meets the cleaning criteria in RG 1.28.
3.13.1 Design Considerations The design and analysis of pressure boundary threaded fasteners complies with ASME Class 1, 2 and 3 requirements. Class 1 pressure boundary threaded fasteners are designed in accordance with ASME BPVC,Section III (Reference 3.13-1), Subsection NB. Class 2 and 3 threaded fasteners are designed in accordance with Subsection NC and ND requirements, respectively.
Tier 2 3.13-1 Draft Revision 1
NuScale Final Safety Analysis Report Engineered Safety Feature Materials To avoid cracking of the base material, the stainless steel weld overlay cladding process conforms to the guidelines of RG 1.43 and the underlying low alloy steel satisfies fine grain requirements. The weld cladding processes are qualified in accordance with ASME Code Section III, Subsection NB-4300 and the low-alloy steel forgings that have cladding applied are manufactured to an ASTM grain size of 5 or finer. Electroslag welding is not used other than for austenitic stainless steel cladding of low alloy steel.
Implementation of RG 1.44 guidelines minimizes the potential for stainless steel intergranular stress corrosion cracking. Prior to fabrication, unstabilized austenitic stainless steel of the AISI Type 3XX series is solution treated per the guidance of RG 1.44, which describes acceptable criteria for preventing intergranular corrosion of stainless steel components. Where austenitic stainless steel materials are subjected to sensitizing temperatures for greater than 60 minutes during post weld heat treatment, non-sensitization of the materials is verified by testing in accordance with ASTM A262, Practice A or E. Furnace-sensitized austenitic stainless steel is not used in NuScale ESF components.
Delta ferrite content of stainless steel weld filler material conforms to the guidelines stipulated in ASME BPV Code,BPVC,Section III, Subsections NB-2433, NC-2433 or NF-2433 and RG 1.31 to ensure sufficient ferrite content to avoid microfissures in welds, offset dilution and reduce thermal aging. The delta ferrite content in stainless steel weld metal is controlled between ferrite number 5 and 20. Ni-Cr-Fe filler metals used for Alloy 690 to low alloy material welds are made with Alloy 52/152/52M filler metal to provide a high level of corrosion resistance.
The guidelines of RG 1.31 or ASME BPV Code,BPVC,Section III, Subsection NB-2433 for determining the delta ferrite of stainless steel welds do not apply to the filler materials used for depositing cladding because the cladding is deposited as a corrosion resistant layer and does not have a structural function. The delta ferrite content in the austenitic stainless steel weld cladding is controlled between ferrite number 5 and 20.
The chemical composition of low-alloy steel filler metals used for the ESF components meets the requirements of the ASME BPV Code,BPVC,Section II material specifications.
The weld metal filler metals are listed in Table 6.1-1.
RAI 06.01.01-5, RAI 06.01.01-8, RAI 06.01.01-9 Pressure retaining bolting and stud materials (studs, nuts and flat washers) used in ESF systems are fabricated of corrosion resistant alloys; SB-637, Alloy 718 (UNS N07718) for connection of the upper and lower CNV shell flanges, top head and reactor pressure vessel (RPV) to CNV support ledge shell; and, SA-564, Grade 630, heat treated at 1100
°FCondition H1100 for CNV appurtenance flanges, and manways and inspection or access ports. These bolting and stud materials are consistent with ASME BPV CodeBPVC,Section III, Subsection NB-2128 and are inspected to the requirements of NB-2580.
Threaded inserts for CNV bolting are fabricated of corrosion resistant alloy SA-479, Type 304/304L.
Tier 2 6.1-3 Draft Revision 1