ML19170A370

LLC Supplemental Response to NRC Request for Additional Information No. 232 (Erai No. 9113) on the NuScale Design Certification Application

ML19170A370
Person / Time
Site:	NuScale
Issue date:	06/19/2019
From:	Rad Z NuScale
To:	Document Control Desk, Office of New Reactors
References
RAIO-0619-65997
Download: ML19170A370 (5)

Text

RAIO-0619-65997 June 19, 2019 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 Supplemental Response to NRC Request for Additional Information No. 232 (eRAI No. 9113) on the NuScale Design Certification Application

REFERENCES:

1. U.S. Nuclear Regulatory Commission, "Request for Additional Information No. 232 (eRAI No. 9113)," dated September 21, 2017

2. NuScale Power, LLC Response to NRC "Request for Additional Information No. 232 (eRAI No.9113)," dated July 23, 2018 The purpose of this letter is to provide the NuScale Power, LLC (NuScale) supplemental response to the referenced NRC Request for Additional Information (RAI).

The Enclosure to this letter contains NuScale's supplemental response to the following RAI Question from NRC eRAI No. 9113:

03.06.03-2 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, Zackary W. Rad Director, Regulatory Affairs NuScale Power, LLC Distribution: Gregory Cranston, NRC, OWFN-8H12 Samuel Lee, NRC, OWFN-8H12 Marieliz Vera, NRC, OWFN-8H12 : NuScale Supplemental Response to NRC Request for Additional Information eRAI No. 9113 NuScale Power, LLC 1100 NE Circle Blvd., Suite 200 Corvalis, Oregon 97330, Office: 541.360.0500, Fax: 541.207.3928 www.nuscalepower.com

RAIO-0619-65997 :

NuScale Supplemental Response to NRC Request for Additional Information eRAI No. 9113 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.: 9113 Date of RAI Issue: 09/21/2017 NRC Question No.: 03.06.03-2 FSAR Section 3.6.3.1.2 states that The use of cold worked austenitic stainless steel is generally avoided, however, if used, the yield strength as determined by the 0.2 percent offset method does not exceed 90 ksi. Fabrication practices, for example the cold bending of small-diameter piping, can affect the material properties of the piping and potential make it more susceptible to stress corrosion cracking (SCC), raise the strength and lower the toughness.

Provide clarification regarding whether any stainless steel (SS) piping systems will have cold bent piping which NuScale proposes to qualify for LBB. If it will be cold bent, state the magnitude of the strain induced from the cold bending. Please state if the cold-worked piping will be solution-annealed after bending. If not solution annealed then justify the magnitude of the cold-bending strain on SCC susceptibility. Also if the pipe material is to be left in the cold bent condition, determine how the toughness changes and revise the LBB analyses, if necessary. The limit-load evaluation for TP304 stainless steel is only applicable to solution annealed TP304.

NuScale Response:

The initial response to RAI 9113 Question 03.06.03-2 was submitted by NuScale letter RAIO-0718-60989, dated July 23, 2018. In a follow-up public meeting with NRC on August 23, 2018, the staff requested that NuScale provide additional information about the Dimensional Plastic Zone Parameter (DPZP) screening parameter used to select the population of cold-worked pipes to be followed by a solution annealing process.

In another follow-up public meeting with NRC on November 7, 2018, the requested DPZP information was discussed. The staff stated that in order to confirm that the DPZP reaches limit-load conditions, NuScale must have both toughness and tensile test data for the TP304 material NuScale Nonproprietary

as a function of cold working at service temperatures, to use in this criterion. If the toughness is reduced into the elastic plastic fracture mechanics (EPFM) range, then secondary stresses (thermal expansion and seismic anchor motion) must be included in the leak-before-break (LBB) analysis. Moreover, any data used for this criterion is to be limited to materials that are at or below the sulfur content value of the TP304 material tested. Finally, once the amount of cold-working for maintaining limit-load conditions is reached (or an EPFM analysis shows sufficient margins for LBB), it is to be demonstrated that the level of cold-working will not lead to higher susceptibility to stress corrosion cracking (SCC) for the TP304 material.

In addition, the staff stated the following, As indicated previously, if NuScale intends to solution anneal all cold-worked austenitic piping applicable to LBB, both issues - applicability of limit-load analysis and avoiding SCC susceptibility - would be resolved, and this RAI Question No. 2 may be closed.

Due to the concerns identified above, NuScale has revised the applicability of the solution annealing process to include all LBB pipes that undergo cold bending, and not just the pipes that do not pass the DPZP screening criterion. The FSAR Section 3.6.3.1.2 has been changed to read:

The use of cold worked austenitic stainless steels is generally avoided; however, if used, the cold worked LBB pipes are followed by a solution annealing process.

Impact on DCA:

The FSAR Tier 2, Section 3.6.3.1.2 has been revised as described in the response above and as shown in the markup provided in this response.

NuScale Nonproprietary

Protection against Dynamic Effects Associated with Postulated Rupture NuScale Final Safety Analysis Report of Piping temperature of the water on the outside of the piping is maintained near room temperature, which prevents SCC initiation in conjunction with minimizing chlorides in solution. Water chemistry conditions during shutdown conditions are controlled to preclude SCC initiation from the outer surface of the piping, using water treatment methods discussed in Section 10.3.5.

RAI 03.06.03-2, RAI 03.06.03-2S1, RAI 03.06.03-9S2 SA-312 TP304/304L dual certified stainless steel is also resistant to SCC given adequate control of dissolved oxygen levels. The alloy contains 0.03 maximum weight percent carbon, which mitigates sensitization. The use of cold worked austenitic stainless steels is generally avoided; however, if used, the cold worked LBB pipes are followed by a solution annealing process if the fracture toughness reduction affects the applicability of the limit load analysis methodology.

Based on the above, the LBB piping is not susceptible to SCC.

3.6.3.1.3 Creep and Creep Fatigue The design temperature for the MSS and FWS lines is 650 degrees F and normal operating temperatures are 585 degrees F and 300 degrees F respectively. Creep and creep fatigue are not a concern for austenitic steel piping below 800 degrees F.

Because the design and operating temperatures of the piping systems are below these limits, creep and creep fatigue are not a concern.

3.6.3.1.4 Water Hammer/Steam Hammer The potential for water hammer and relief valve discharge loads are considered and their effects minimized in the design of the main steam system. Utilizing drain pots, proper line sloping, and drain valves minimize this potential. The dynamic loads such as those caused by main steam isolation valve closure or Turbine Stop Valve closure due to water hammer and steam hammer are analyzed and accounted for in the design and analysis of the main steam piping. Therefore, the main steam piping is not susceptible to effects of water hammer.

The FWS and SG contain design features and operating procedures that minimize the potential for and effect of water hammer. The SG and FWS features are designed to minimize or eliminate the potential for water hammer in the steam generator FWS. The dynamic loads such as those caused by feedwater isolation valve closure and turbine trip due to water hammer are analyzed and accounted for in the design and analysis of the FWS piping. Therefore, the feedwater system LBB piping is not susceptible to water hammer.

RAI 03.06.02-6, RAI 03.06.03-3 The safe shutdown earthquake loading used for the LBB evaluations bounds the water hammer loading for both the feedwater lines and the main steam lines.

3.6.3.1.5 Fatigue Low-cycle Fatigue Tier 2 3.6-48 Draft Revision 3