ML18340A013

July 24, 2018, Summary of Category 1 Public Teleconference with Nuscale Power, LLC, Design Certification Application Section 3.7, Seismic Design, and 3.8, Design of Category I Structures.

ML18340A013
Person / Time
Site:	NuScale
Issue date:	04/17/2019
From:	Vera M NRC/NRO/DLSE/LB1
To:	Samson Lee NRC/NRO/DLSE/LB1
Vera A M/NRO/5861
References
Download: ML18340A013 (9)

Text

April 17, 2019 MEMORANDUM TO: Samuel S. Lee, Chief Licensing Branch 1 Division of Licensing, Sitting, and Environmental Analysis Office of New Reactors FROM: Marieliz Vera, Project Manager /RA/

Licensing Branch 1 Division of Licensing, Sitting, and Environmental Analysis Office of New Reactors

SUMMARY

OF THE JULY 24, 2018, CATEGORY 1 PUBLIC TELECONFERENCE WITH NUSCALE POWER, LLC., DESIGN CERTIFICATION APPLICATION SECTION 3.7, "SEISMIC DESIGN," AND SECTION 3.8, "DESIGN OF CATEGORY I STRUCTURES" The U.S. Nuclear Regulatory Commission (NRC) held a Category 1 public teleconference on July 24, 2018, to discuss Final Safety Analysis Report (FSAR) Tier 2, Chapter 3, Design of Structures, Systems, Components and Equipment, Section 3.7, Seismic Design and Section 3.8, Designs of Category I Structures, of the NuScale Power, LLC., (NuScale) Design Certification. Participants included personnel from NuScale and members of the public.

The public meeting notice can be found in the Agencywide Documents Access and Management Systems under Accession Number ML18218A109. This meeting notice was also posted on the NRC public Website.

The Meeting Agenda and List of Attendees can be found in Enclosures 1 and 2, respectively.

The technical issues discussed are included in Enclosure 3.

The purpose of this meeting was to discuss the responses for Request for Additional Information (RAI) 8966, Question 03.08.04-3 (ML18031B317, ML18164A409); RAI 8936, Question 03.07.02-10 (ML18176A154); and RAI 8934, Question 03.07.02-15 (ML17355A678, ML18127B711, ML18180A343).

CONTACT: Marieliz Vera, NRO/DLSE 301-415-5861

S. Lee The applicant will provide a supplement to the RAI response reflecting the NRC staffs feedback (Enclosure 3) for RAI 8966, Question 03.08.04-3; RAI 8936, Question 03.07.02-10 and RAI 8934, Question 03.07.02-15.

Docket No.52-048

Enclosures:

As stated cc w/encls.: DC NuScale Power, LLC Listserv

ML18340A013 *via email NRC-002 OFFICE NRO/DLSE/LB1: PM NRO/DLSE/LB1: LA NRO/DNRL/LB1: PM NAME MVera CSmith MVera DATE 12/06/2018 12/18/2018 04/17/2019 U.S. NUCLEAR REGULATORY COMMISSION CATEGORY 1 PUBLIC TELECONFERENCE WITH NUSCALE POWER, LLC.

DESIGN CERTIFICATION APPLICATION SECTION 3.7, "SEISMIC DESIGN," AND SECTION 3.8, "DESIGN OF CATEGORY I STRUCTURES" July 24, 2018 10:30 a.m. - 12:00 p.m.

Meeting Agenda Time Topic 10:30 a.m. - 10:35 a.m. Welcome and Introductions 10:35 a.m. - 11:55 a.m. Discussion of the Request for Additional Information 11:55 a.m.- 12:00 p.m. Public - Questions and Comments 12:00 p.m. Adjourn Enclosure 1

U.S. NUCLEAR REGULATORY COMMISSION CATEGORY 1 PUBLIC TELECONFERENCE WITH NUSCALE POWER, LLC DESIGN CERTIFICATION APPLICATION SECTION 3.7, "SEISMIC DESIGN," AND SECTION 3.8, "DESIGN OF CATEGORY I STRUCTURES" LIST OF ATTENDEES July 24, 2018 NAME AFFILIATION Marieliz Vera U.S. Nuclear Regulatory Commission (NRC)

Manas Chakravorty NRC Sunwoo Park NRC Robert Roche NRC Pravin Patel NRC Alissa Neuhausen NRC Ata Istar NRC Samuel Lee NRC Marty Bryan NuScale Power, LLC (NuScale)

Josh Parker NuScale Nick Brown NuScale Tom Ryan NuScale Kirsten McKay NuScale Evren Ulku NuScale Hadi Razavi NuScale Mohsin Khan NuScale Kyra Perkins NuScale Sarah Fields Public Enclosure 2

U.S. NUCLEAR REGULATORY COMMISSION CATEGORY 1 PUBLIC TELECONFERENCE WITH NUSCALE POWER, LLC DESIGN CERTIFICATION APPLICATION SECTION 3.7, "SEISMIC DESIGN," AND 3.8, "DESIGN OF CATEGORY I STRUCTURES" The Staffs Feedback on Request Additional for Information (RAI) 8966 Question 03.08.04-03 In its response dated January 31, 2018, the applicant stated that beams used for construction purposes are planned to be left in place, but are not considered as part of the roof design.

Subsequently, in its response dated June 13, 2018, the applicant stated that the details of the roof construction are not yet finalized. Further, the applicant indicated that the construction aids to be utilized including light weight Q-decking and steel supporting beams and stated that these are to be removed after concrete is cured. Also, the applicant clarified that the construction aids will not be used to provide direct or indirect load path for the final roof design. Additionally, the applicant stated that in the case that a construction aid element cannot be removed, its presence will be evaluated on a case-by-case basis.

While the construction aid elements are not used to provide direct or indirect load path for the final roof design, the construction aids that may be left in place may affect the mass and stiffness properties of the roof and associated seismic demands. Therefore, the staff requested the applicant to clarify if the details of the roof construction and related evaluation of the effects of the construction aid elements left in place is to be completed for review as part of the Design Certification Application (DCA) review or to be completed by the combined license (COL) applicant. If the former, the staff requests the applicant to provide a date by which a supplemental response, with such details, will be provided for the staffs review. If the latter, the staff requests the applicant to include a COL item in the DCA addressing such finalization of construction details and respective evaluation of the effects of the construction aid elements left in place.

The Staffs Feedback on RAI 8936 Question 03.07.02-10 In its June 25, 2018, response to RAI 8936, Question 03.07.02-10, the applicant provided a comparison of reaction forces at the skirt and lug restraints from the 3D NPM (ANSYS) model with NuScale Power Module (NPM) beam (SASSI) model, which indicates that results from ANSYS 3D model exceed those from SASSI beam model at certain locations.

1) The applicant provided Table 1 in the RAI response that summarizes the comparison of maximum reaction forces between the 3D detailed model and simplified beam model.

However, in its proposed markup, the applicant did not indicate that this table will be included in the FSAR. Currently, FSAR Table 3B-27 includes only the force demands from the SASSI beam model and associated D/C ratios. Since the envelope of the 3D and beam model results is intended to be used as the design basis demands for NPM Enclosure 3

support design, Table 1 should be included in the FSAR or existing Table 3B-27 should be expanded to include ANSYS 3D results.

2) In the RAI response, the applicant stated that three analysis cases (involving different combinations of concrete cracking and NPM frequency shifting) are considered in the enveloping of SASSI and ANSYS analysis results.

(a) Based on the RAI response, it appears that the design-basis seismic demands for NPM skirt and lug supports are determined by enveloping the results from the SASSI and ANSYS analyses for the three analysis cases described in the RAI response. Each ANSYS analysis case covers two different NPM configurations (NPM1 and NPM6). Please confirm if that is a correct understanding. FSAR Table 3.7.2-34 provides seismic analysis identification codes for key Category I Structure System and Components (SSCs). Since the NPM supports are important structural elements and its seismic demands are determined in a manner distinctive from other structural elements, the applicant should consider expanding Table 3.7.2-34 to include the NPM supports (skirt and lug restraints).

(b) The third analysis case (Case 3) introduced in the RAI response involves the frequency of NPM reduced by 15 percent. The staff understands that design-basis Reactor Building (RXB) SASSI analysis cases discussed in FSAR Section 3.7.2; all use an NPM beam model with its nominal frequency (100 percent) and no analysis cases involved an NPM with reduced frequency. Please clarify if the applicant ran SASSI analysis with a 15 percent reduced-frequency NPM beam model in establishing the seismic demand envelope for NPM support design.

(c) Please provide a comparison of the SASSI results from analysis Case 1 (cracked concrete and 100 percent NPM frequency) and Case 3 (cracked concrete and 85 percent NPM frequency) introduced in the RAI response.

(d) If the comparison in (c) indicates significant differences, please discuss the potential impact of a reduced-frequency NPM beam model on RXB design-basis seismic demand calculations discussed in FSAR Section 3.7.2.4.

(e) The staff notes that FSAR Table 3B-52 indicates NPM stiffness reduction to 77 percent, which would correspond to 12 percent reduction in frequency (compared to 15 percent mentioned in the RAI response). Please check for consistency.

3) In an FSAR markup (Section 3.7.2.1.2.2, Page 3.7-118, Draft Revision 2), the applicant proposed to include a statement, At the interface between the NPM and the RXB, the design loads for the skirt and lug supports are defined as the envelope between the SASSI2010 building model and the 3-D model discussed in Appendix 3A. The staff notes that the analysis cases considered in the enveloping are not specified in this statement. In the context of Section 3.7.2, SASSI2010 building model could imply the 612 analysis cases considered in establishing the RXB design basis envelope. The applicant should include an adequate qualifier indicating what analysis cases are involved in the enveloping; e.g., the three analysis cases described in the RAI response could be included or referred to in the markup statement.

4) In its RAI response and associated FSAR markups, the applicant indicated that the design loads for the Containment Vessel (CNV) skirt support and NPM bay wall lug restraints are defined as the envelop between the SASSI2010 building model and the 3-D model discussed in Appendix A. While the RAI response provided updated D/C ratios for both the CNV skirt support and NPM bay wall lug restraints, only the updated D/C ratios for the CNV skirt support were addressed in the FSAR markups. The staff requests the applicant to provide FSAR markups addressing the updated D/C ratios for all modes of failure of the NPM bay wall lug restraints based on the aforementioned envelop design loads.

5) The staff requests the applicant to clarify whether the updated seismic demands and associated D/C ratios have been considered in the seismic margin evaluation discussed in FSAR Chapter 19 and describe associated updates or provide the basis for the seismic margin evaluation remaining unaffected as applicable.

6) In its RAI response, the applicant provided a proposed markup for TR-0916-51502-P (Page 26, Pages 168-169; Draft Revision 1). However, it appears that page(s) are missing after Page 26 in the markup. Please check.

The Staffs Feedback on RAI 8934 Question 03.07.02-15 In its June 29, 2018, response to RAI 8934, Question 03.07.02-15, the applicant provided an evaluation which shows that an additional gravity loading by a factor of .28g creates load demands in the pool walls and foundation that are higher than the demands from the 4.2 psi average hydrostatic pressure. The applicant also provided FSAR markups to address staffs concerns communicated during the May 29, 2018, public meeting.

1) The staff reviewed Page 3.7-124 (FSAR Draft Revision 2) in the markup provided in the RAI response and the following is an excerpt from the first and second paragraphs on that page:

.. Based on these results, an average pressure of 4.20 psi was added as static pressure to the SAP2000 RXB model. This added pressure accounts for the missing 3D effects of fluid-impulsive pressure on the pool walls and foundation.

The pressure at the bottom of the pool due to gravity loading of the water is approximately 30 psi (62.4 lb/ft3

• 69 ft depth *1/144 ft2/in2). Consequently, the average pressure on the wall is half this amount, or 15 psi. The pressure of 4.20 psi is 28 percent of the average pressure (4.20 psi/15 psi = 0.28). Therefore, a 1.28g vertical static loading was added to the SAP2000 model to ensure this additional pressure is accounted for in the design. See Figure 3.7.2-129.

Increasing the downward acceleration by a factor of 1.28 corrects for the underestimated fluid pressure, due to mass lumping, in the SSI model.

Horizontal hydrostatic load is a function of fluid density and depth. Fluid density can be altered by changing the acceleration due to gravity.

Increasing the vertical gravitational acceleration increases the horizontal hydrostatic pressure.

(a) It appears that the two underlined statements above conflict each other. The applicant should consider rewording and streamlining the affected paragraphs to avoid potential confusion and enhance clarity. As the applicant stated in the RAI response, it was determined that an average pressure of 4.2 psi must be applied to the walls to correct for the underestimated hydrodynamic pressure. Then, this additional pressure was added to the SAP2000 model by amplifying the gravity load by a factor of 1.28.

(b) The purpose of the last two sentences (bold faced) in the quoted paragraph above are not clear to the staff. Also, the phrase Fluid density can be altered by changing... does not appear to be a correct statement.

2) Clarify in the RAI response, whether the Cr, To, and Ro loads from ACI Equation 9-6 have been considered in establishing the design basis demands for the RXB or otherwise provide basis for not including these demands as applicable.

3) The applicant should include in the FSAR (preferably in FSAR Section 3.8.4.3.2), a statement that captures the applicants response to staff follow-up Question #4 with respect to the hydrostatic pressure distribution being applied as a surface pressure to all wetted area elements in the SAP2000 model.

4) The applicant should include in the FSAR, a statement stating that amplifying the gravity load by a factor of 1.28 generates more conservative load demands for the pool walls and foundation than the 4.2 psi average hydrostatic pressure, or to that effect.

5) The staff notes that the RAI response references Figure 2-2 which is not identified in the document. Also in Section 2 of the discussion, the figure numbers start at 2-5 (with 2-1 to 2-4 missing). Since RAI response is an official document docketed, the applicant should maintain correctness and acceptable styles of the document provided.