ML17346A519

LLC Response to NRC Request for Additional Information No. 251 (Erai No. 9188) on the NuScale Design Certification Application

ML17346A519
Person / Time
Site:	NuScale
Issue date:	12/12/2017
From:	Rad Z NuScale
To:	Document Control Desk, Office of New Reactors
References
RAIO-1217-57618
Download: ML17346A519 (8)

Text

RAIO-1217-57618 December 12, 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.

251 (eRAI No. 9188) on the NuScale Design Certification Application

REFERENCE:

U.S. Nuclear Regulatory Commission, "Request for Additional Information No.

251 (eRAI No. 9188)," 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 Question from NRC eRAI No. 9188:

05.03.01-3 The response to question 05.03.01-4 will be provided by March 30, 2018.

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 Carrie Fosaaen at 541-452-7126 or at cfosaaen@nuscalepower.com.

Sincerely, Za Zackary W. Rad Director, Regulatory Affairs Director NuScale Power, LLC Distribution: Gregory Cranston, NRC, OWFN-8G9A Samuel Lee, NRC, OWFN-8G9A Bruce Bavol, NRC, OWFN-8G9A : NuScale Response to NRC Request for Additional Information eRAI No. 9188 NuScale Power, LLC 1100 NE Circle Blvd., Suite 200 Corvalis, Oregon 97330, Office: 541.360.0500, Fax: 541.207.3928 www.nuscalepower.com

RAIO-1217-57618 :

NuScale Response to NRC Request for Additional Information eRAI No. 9188 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.: 9188 Date of RAI Issue: 10/13/2017 NRC Question No.: 05.03.01-3 During the NRC staffs audit of DCD Tier 2, FSAR, Section 3.13, the staff reviewed the use of threaded inserts in the NuScale design. The audit team identified that threaded inserts are used for all threaded fasteners except for the main containment vessel (CNV) and reactor pressure vessel (RPV) flange studs. The threaded inserts provide a corrosion barrier to the base metal, and have a weld connecting them to the base metal. Degradation of these welds may cause degradation of the underlying base metal. Depending on their location, the threaded insert welds may be subject to stresses during normal operation, refueling tensioning and de-tensioning, and ECCS actuation. The DCD does not discuss the installation and inspection (construction and inservice) of these welds.

DCD Tier 2, FSAR, Chapter 5 does not describe the use of threaded inserts for the RPV threaded fasteners. While Table 5.2-4 lists the RPV flange stud threaded inserts, the wording seems to describe the RPV main flange, which is clad and does not use a threaded insert.

Therefore, this statement is unclear and does not encompass all uses of threaded inserts for the RPV as identified by the audit team.

Revise the DCD Tier 2, FSAR, Table 5.2-4 and Section 5.3.1 to state the locations that threaded inserts will be used for the RCPB.

Revise the DCD to describe the welding procedures and inspections that will be performed on the threaded insert welds during fabrication/installation.

Provide justification that the threaded insert welds will not degrade during service. If justification cannot be provided, revise the DCD to describe augmented inspections to provide reasonable assurance that the welds will remain intact during operation.

NuScale Response:

FSAR, Table 5.2-4 and FSAR Section 5.3.1.7 have been updated to state the locations at which threaded inserts will be used for the reactor coolant pressure boundary (RCPB) threaded fasteners.

Welding procedures and inspections that will be performed on the threaded insert welds for threaded fasteners during fabrication and installation are in accordance with applicable ASME NuScale Nonproprietary

Code, Sections III and XI requirements as described in FSAR Sections 5.3.1.4 and 5.2.3.4.

The threaded inserts used for threaded fasteners are externally threaded in addition to being internally threaded such that the inserts are threaded into the associated base metal. As such, the external threads on the inserts and internal threads in the flange bolt holes carry mechanical loads during normal and off-normal operations, including ECCS actuation. During tensioning and de-tensioning the threaded inert seal weld will experience a mechanical load. To provide reasonable assurance that the welds remain intact, a VT-1 visual inspection of the welds will be performed when the associated flange is removed. This augmented inspection has been added to FSAR Table 5.2-6.

Impact on DCA:

FSAR Section 5.3.1.7 and FSAR Tables 5.2-4 and 5.2-6 have been revised as described in the response above and as shown in the markup provided in this response.

NuScale Nonproprietary

NuScale Final Safety Analysis Report Integrity of Reactor Coolant Boundary RAI 05.02.03-9, RAI 05.03.01-3, RAI 06.01.01-3 Table 5.2-4: Reactor Coolant Pressure Boundary Component and Support Materials Including Reactor Vessel, Attachments, and Appurtenances Component Specification Alloy Designation (Grade, Class, or Type)

Reactor Vessel Lower RPV section flange shell SA-508 Grade 3, Class 1 RPV bottom head Core support blocks RPV top head SA-508 Grade 3, Class 2 PZR Shell Integral Steam Plenum Upper RPV flanged transition shell Steam plenum access ports Upper RPV SG shell Lower RPV SG shell Feed plenum access ports Upper and lower RPV steam generator shells RPV support gussets SA-533 Type B, Class 2 RPV support plates Core barrel guides SA-193SA-479 or Type 304/304L; Grade B8, Class 1 with 0.03% max SA-240 carbon Vessel alignment pins SA-479 Type 304/304L RPV flange stud threaded insertsPressure instrument tap swagelok reducers Threaded inserts for:

RSV flanges Instrumentation and controls (I&C) access ports PZR heater access ports Steam plenum access ports Feed plenum access ports Pressure instrument tap swagelok reducers Instrumentation and Controls (I&C) access port covers SA-240 Type 304/304L I&C access port cover threaded fasteners SB-637 Alloy 718 (UNS N07718)

RPV flange leak detection tube SA-312 Type 316L; Seamless RPV flange closure stud bolts, nuts, and washers SB-637 Alloy 718 (UNS N07718)

RSV flange threaded fasteners, nuts, and washersThreaded fasteners, nuts, and washers for:

Main RPV flange RSV flanges I&C access ports PZR heater access ports Steam plenum access ports Feed plenum access ports I&C swagelok male connectors SA-479 Type 316/316L PZR pressure taps SB-166 Alloy 690 (UNS N06690)

Thermowell nozzles Tier 2 5.2-35 Draft Revision 1

NuScale Final Safety Analysis Report Integrity of Reactor Coolant Boundary RAI 05.02.04-3, RAI 05.03.01-3, RAI 06.06-3 Table 5.2-6: Reactor Pressure Vessel Inspection Elements Description Examination Examination Notes Category Method RPV Shell and Head Welds Lower RPV flange shell to RPV bottom head B-A Volumetric Upper RPV flanged transition shell to lower SG shell Lower SG shell to upper SG shell Upper SG shell to integral steam plenum Integral steam plenum to PZR shell PZR shell to RPV top head Steam plenum cap to integral steam plenum RPV Internal Welds Core support block to RPV bottom head B-N-2 VT-3 Core support block to latch Core barrel guide to lower RPV flange shell Upper tube support bar to lower RPV integral steam plenum Lower tube support cantilever to upper RPV Instrumentation and Controls Sleeve Welds None None These welds are part of the cladding.

Flow diverter to RPV lower head B-N-1 VT-3 B-N-1 is for the space above and RPV interior surfaces and attachment welds below the core made accessible by removal of components during a normal refueling outage RPV External Welds RPV support plate to RPV support gussets F-A VT-3 RPV support plate to upper RPV SG shell 1-4 RPV support plate to upper RPV SG shell B-K Surface or RPV support gussets to upper RPV SG shell Volumetric RPV lateral support lug RPV Nozzle to Shell and Head Welds Reactor recirc valves B-D Volumetric Inside corner. All welds Feedwater nozzles examination requirement IWB-2500-7(d).

RCS discharge Main steam nozzles B-D Volumetric Examination requirement IWB-2500-7(d)

RCS injection B-D N/A No inside corner PZR spray supply lines Tier 2 5.2-39 Draft Revision 1

NuScale Final Safety Analysis Report Integrity of Reactor Coolant Boundary Table 5.2-6: Reactor Pressure Vessel Inspection Elements (Continued)

Description Examination Examination Notes Category Method Reactor vent valves B-D None Inside corner region examinations Reactor safety valves are not required for pressurizer nozzles by ASME BPV C,Section XI.

RPV high point degasification Therefore, these nozzles are CRDM nozzles exempted from inspection given the nozzles have the same functionality and consequences as traditional pressurizer nozzles region of the vessel.

PZR heater access ports B-D Not required See ASME BPVC,Section XI, Table I&C - Channels IWB-2500-1 (B-D) Note 1.

Feedwater plenum access ports B-D Volumetric No inside cornerExamination requirement IWB-2500-7(b)

Main steam plenum access ports Examination requirement IWB-2500-7(c)

All welds, no inside corner PZR pressure taps B-D Volumetric No inside corner, shell side exam onlyExamination requirement IWB-2500-7(a)

T-Hot thermowells Examination requirement IWB-2500-7(a)

PZR liquid temp thermowells Examination requirement IWB-2500-7(a)

PZR T-Hot thermowells Examination requirement IWB-2500-7(a)

Ultrasonic testing sensor nozzles Examination requirement IWB-2500-7(b)

All welds, no inside corner, shell side exam only Nozzle-to-Safe End Dissimilar Metal Welds RRV safe ends B-F Surface and Feedwater nozzle safe ends Volumetric Main steam nozzle safe ends RVV safe ends RCS injection safe end (inner and outer)

RCS discharge safe end B-F Surface PZR spray supply safe end (outer)

RPV high point degasification safe end PZR spray supply safe end (inner) None None Open ended pipe CRDM nozzle safe ends B-O Volumetric or Surface Threaded Fastener Threaded Insert Welds RSV flanges None VT-1 No inspection requirement.

I&C access ports Augmented to VT-1 when bolts are removed.

PZR heater access ports Steam plenum access ports Feed plenum access ports Tier 2 5.2-40 Draft Revision 1

NuScale Final Safety Analysis Report Reactor Vessel Furthermore, because Alloy 718 is not a ferritic material, the fracture toughness requirements of NB-2333 are not required. Further information is provided in Section 3.13.

RAI 05.03.01-3 Threaded inserts are used for all RPV threaded fasteners except for the main RPV flange studs and steam generator inlet flow restrictor hardware. See Table 5.2-4 for threaded insert materials and applicable specifications.

5.3.2 Pressure-Temperature Limits, Pressurized Thermal Shock, and Charpy Upper-Shelf Energy Data and Analyses Analyses The information provided in this section describes the bases for setting operational limits on pressure and temperature for the RCPB and ensures the requirements of 10 CFR 50, Appendices G and H, and 10 CFR 50.61 are complied with throughout the 60-year life of the plant.

5.3.2.1 Limit Curves Using the methodology provided in ASME BPVC Section XI, Appendix G, and the requirements in 10 CFR 50 Appendix G, a generic set of pressure-temperature limits at 57 EFPY is calculated for various conditions. The methodology also accounts for vessel embrittlement due to neutron fluence in accordance with RG 1.99. The pressure-temperature limits for normal heatup and criticality conditions, normal cooldown, and inservice leak and hydrostatic tests are provided in Figure 5.3-3, Figure 5.3-4, and Figure 5.3-5, respectively. The corresponding numerical values are listed in Table 5.3-6 and Table 5.3-7. These pressure-temperature curves meet all the pressure and temperature requirements for the RPV listed in Table 1 of 10 CFR 50, Appendix G. The RCS pressure should be maintained below the limit of the pressure-temperature limit curves to ensure protection against non-ductile failure. Acceptable pressure and temperature combinations for reactor vessel operation are below and to the right of the applicable pressure-temperature curves. These pressure-temperature curves do not include any location correction or instrument uncertainty. For the purpose of location correction, the allowable pressure in the pressure-temperature curves can be taken as the pressure at the RPV bottom. The reactor is not permitted to be critical until the pressure-temperature combinations are to the right of the criticality curve shown in Figure 5.3-3.

The RTNDT at the 1/4 -T adjusted reference temperature at end of life is provided in Table 5.3-3, as described in Section 5.3.1.5.

Further information on the specific methodology is provided in NuScale Technical Report TR-1015-18177, "Pressure and Temperature Limits Methodology" (Reference 5.3-8).

Tier 2 5.3-6 Draft Revision 1