ML18333A221

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Phase 2 Audit Nuscale Reactor Internals Comprehensive Vibration Assessment Program
ML18333A221
Person / Time
Site: NuScale
Issue date: 12/13/2018
From: Vera M
NRC/NRO/DLSE/LB1
To: Samson Lee
NRC/NRO/DLSE/LB1
Vera A M/NRO/5861
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December 13, 2018 MEMORANDUM TO: Samuel S. Lee, Chief Licensing Branch 1 Division of Licensing, Siting, and Environmental Analysis Office of New Reactors FROM: Marieliz Vera, Project Manager /RA/

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

SUBJECT:

U.S. NUCLEAR REGULATORY COMMISSION STAFFS REPORT OF THE REGULATORY AUDIT FOR NUSCALE POWER, LLC.; PHASE 2 AUDIT NUSCALE REACTOR INTERNALS COMPREHENSIVE VIBRATION ASSESSMENT PROGRAM On January 6, 2017, NuScale Power, LLC., (NuScale) submitted a design certification (DC) application, for a Small Modular Reactor, to the U.S. Nuclear Regulatory Commission (NRC)

(Agencywide Documents Access and Management System (ADAMS) Accession No. ML17013A229). The NRC staff started its detailed technical review of NuScales DC application on March 15, 2017.

The NRC staff conducted an audit of component design specifications associated with the NuScale DC application, Final Safety Analysis Report (FSAR), Section 3.9.2. The audit was initiated on September 5, 2018 and ran through October 4, 2018, in accordance with the audit plan in ADAMS (ML18236A533).

The purpose of the audit was to: (1) gain a better understanding of the NuScale design; (2) verify information; (3) identify information that may require docketing to support the basis of the licensing or regulatory decision; and (4) review related documentation and non-docketed information to evaluate conformance with regulatory guidance and compliance with NRC regulations.

The audit was performed to gain a better understanding of the reactor internals comprehensive vibration assessment program (CVAP) and seismic analysis of the NuScale Standard Plant DC application are being performed in accordance with the methodology and criteria described in the NuScale FSAR.

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

S. Lee The NRC staff conducted the audit via access to NuScales electronic reading room. The audit was conducted in accordance with the NRC Office of New Reactors (NRO) Office Instruction NRO-REG-108, Regulatory Audits.

The publicly available version of the audit report and the audit attendee list are enclosed with this memorandum.

Docket No.52-048

Enclosures:

1. Audit Summary - (Non-Proprietary)
2. Attendee List
3. Audit Summary - (Proprietary) cc w/encl.: DC NuScale Power, LLC Listserv (w/o Enclosure 3)

Memo: ML18333A221 Package: ML18333A220 *via email NRO-002 OFFICE NRO/DNRL/LB1: PM NRO/DNRL/LB1: LA NRO/DEI/MEB: BC NRO/DNRL/LB1: PM NAME MVera CSmith TLupold MVera DATE 11/28/2018 12/11/2018 12/13/2018 12/13/2018 U.S. NUCLEAR REGULATORY COMMISSION

SUMMARY

PHASE 2 AUDIT REPORT OF NUSCALE POWER, LLC, REACTOR INTERNALS COMPREHENSIVE VIBRATION ASSESSMENT PROGRAM NRC Audit Team:

  • Stephen Hambric, (NRC Consultant)
  • Marieliz Vera Amadiz, NRO Project Manager (NRC)

1.0 BACKGROUND

Title 10 of the Code of Federal Regulations (10 CFR) Part 52, Section 47, Contents of applications; technical information, states that:

The application must contain a level of design information sufficient to enable the Commission to judge the applicant's proposed means of assuring that construction conforms to the design and to reach a final conclusion on all safety questions associated with the design before the certification is granted. The information submitted for a design certification must include performance requirements and design information sufficiently detailed to permit the preparation of acceptance and inspection requirements by the [U. S. Nuclear Regulatory Commission] NRC, and procurement specifications and construction and installation specifications by an applicant. The Commission will require, before design certification, that information normally contained in certain procurement specifications and construction and installation specifications be completed and available for audit if the information is necessary for the Commission to make its safety determination.

On March 15, 2017, the U.S. Nuclear Regulatory Commission (NRC) accepted and docketed a standard design certification application (DCA) (Reference 1) submitted by NuScale Power, LLC., (NuScale), to certify its small module reactor design.

Between May 16, 2017, and November 2, 2017, the NRC staff completed Phase 1 of the subject audit that included review and examination of NuScales design documents, drawings, test plans, and test reports related to the reactor internals comprehensive vibration assessment program (CVAP). The NRC staffs Phase 1 audit summary report is available in Agencywide Documents Access and Management System (ADAMS) under Accession No. ML18023A091.

The purpose of the Phase 2 audit was to verify that the appropriate updates have been made to the reactor internals CVAP vibration analysis and testing documents that were identified and summarized in the NRC staffs Phase 1 audit report. The NRC staff will also review the vibration analyses and testing data to resolve the outstanding request for Enclosure 1

additional information (RAI) issues including the steam generator (SG) tubes, SG inlet flow restrictors (SGIFR), and initial startup testing.

The NRC staff provided NuScale with the Phase 2 audit plan to facilitate the audit, as documented in ADAMS (ML18236A533). The NRC staff followed the NRO Office Instruction NRO-REG-108 (Revision 0), Regulatory Audits, in performing the audit of the NuScale design specifications.

At the NRC and the NuScale office in Rockville, Maryland, from September 5, 2018 through October 4, 2018, staff members from the Mechanical Engineering Branch (MEB) of the Division of Engineering and Infrastructure in the NRC Office of New Reactors (NRO) and NRC consultant conducted a regulatory audit of the NuScale reactor internals CVAP. The NRC staff reviewed the NuScale design documents, drawings, test plans, and test reports related to the reactor internals CVAP. The NRC staffs observations and findings are documented in the Audit Results section.

2.0 DOCUMENTS REVIEWED

  • ER-A010-6408, Revision A, Steam Generator Inlet Flow Restrictor Preliminary Vibration Test Assessment, September 5, 2018.
  • ER-A014-2377, Revision 0, Test Development Plan for Flow-Induced Vibration of the NuScale Helical Coil Steam Generator.
  • EC-T050-6412, Revision 0, SG FIV Pre-Test Modal Analysis.
  • ER-T050-6540, Revision 0, Evaluation of TF2 Strain Gage Data for Fluid Elastic Instability Content.
  • 02312 RP 14, Revision 0, Electrically Heated Test Facility Final Data Report, July 14, 2014.
  • ECN-A023-6425, Revision 0, Revision of CRAGT PSD Assumption and Equation Correction.
  • ECN-A023-6502, Revision 0, Modifications to Siding Distance used in Wear Calculations.
  • Drawing NP12-01-A011-M-AS-6025, Revision 0, Steam Generator Flow Restrictors.

3.0 AUDIT RESULTS Several NuScale CVAP internal documents were audited by the staff. The major reactor internal components audited were:

A thermal hydraulic test report for SGIFR design concepts (ER-A010-6408) was provided, along with reports for HCSG tubing TF2 testing at the SIET facility in Italy (ER-T050-6540 and 02312 RP 14) and preliminary test plan (ER-A014-2377) and finite element (FE) modal analyses (EC-T050-6412) for future planned TF3 HCSG testing. Primary objectives for initial prototype plant startup testing were also discussed, but no formal documents were provided on this topic. Audit findings are summarized below.

SGIFR design concept testing NuScale made the following report on SGIFR testing available during the audit:

  • ER-A010-6408, Revision A, Steam Generator Inlet Flow Restrictor Preliminary Vibration Test Assessment.

Twelve SGIFR insert design concepts were tested primarily to confirm flow restriction head loss coefficients were sufficiently high to ensure Density Wave Oscillation (DWO) will not occur in the HCSG. The inserts were installed within a mockup of a tube sheet and SG tube inlets in various orientations. The flow tests were designed to match prototypic Reynolds Numbers (product of flow speed and characteristic dimension divided by viscosity). Since much of the flow testing was conducted at room temperature and pressure (and therefore high viscosity), the flow rates were increased significantly to match prototypic Reynolds Numbers.

Three different restrictor design types were tested: a center orifice, threaded bolts with two lengths (with annular flow through the passage between the bolt threads and the wall), and several stepped inserts with variable numbers of steps, step spacing, and diameters (also with annular flow). The center orifice concept allowed leakage flow, and was eliminated from consideration. The two threaded bolts did not provide sufficient head loss and were also eliminated. The bulk of the testing focused on nine stepped insert concepts. Three copies of each design were tested in four different holes to establish consistency of results. Two concepts, including the one chosen for final design development, were also tested with misaligned inserts touching the walls.

Misalignment of some inserts seems likely given the complexity of the assembled SGIFRs and tubesheet structures, allowable tolerances, and the difficulty of installation. Impact is also therefore likely during plant operation, but should be low amplitude based on the test results.

The entire flow restrictor assembly will be removed periodically to allow for SG tube inspections.

The design concepts were tested at various flow rates/Reynolds Numbers. Since the maximum test flow rates are much higher than prototypic flow rate at full power, the devices are effectively tested at much higher speeds than needed to confirm the absence of leakage flow instability (LFI) and other flow-induced vibration (FIV) mechanisms that can lead to rapid degradation and eventual fatigue failure of components. Test flow rates at Reynolds Numbers of 15 and 50 percent bracket the expected flow rates at full power.

The testing is slightly non-prototypic, in that the tubesheet is about half as thick as that of the actual design. This is to allow the restrictors to be inserted into the SG tube mockups, which were instrumented with accelerometers to measure any potential wall impacts (the restrictors themselves are not directly instrumented). Using a thinner tubesheet for these tests does not

affect the flow around the restrictors or onset of LFI, however, and is acceptable. The accelerometer signals were examined for evidence of strong impact with the tube walls which might be indicative of LFI or strong turbulent buffeting response.

The raw test data were also made available to the staff. Time histories and vibration (acceleration) spectra of the stepped designs, including spectrograms computed by the staff, were reviewed and showed no evidence of strong wall impacts indicative of turbulent buffeting or LFI. The data sampling rate was much higher than the first two resonance frequencies of the inserts (which correspond to cantilevered beam modes) which could possibly be part of a LFI response. The root mean square (RMS) vibrations increase with the square of flow velocity as expected of linear response (confirming there was no LFI or other unexpected strong FIV mechanism present during any of the tests). The acceleration measurements were integrated over time to estimate the displacements of the tubes, which is much less than the radial clearance of the inserts for all flow conditions tested. Boroscope inspections of the inner walls of the tubing did not indicate any damage.

The final design is very similar to Concept 6 (which showed the lowest vibration amplitudes of all designs), with the same number of steps (5), same outer diameter, with step spacing about 5 percent wider, and about 10 percent longer. The tip alignment cone is also slightly different, with <10 percent geometry differences. Since other concepts were tested that bracket these design changes and those concepts also did not show any signs of LFI, these design changes are not expected to lead to LFI. Also, the assembly of the final restrictor design to the mounting plate differs from that of the testing configuration. NuScale states that these differences should be evaluated in final design testing.

Testing of the final insert design is deferred to the combined license (COL) holder. Also, the final insert design is still subject to change as manufacturability and installation studies are ongoing. The test requirements for the final design will be included in the CVAP testing document, which NuScale plans to submit during design certification. NuScale provides some plans for final testing in ER-A010-6408, though:

  • Modal testing of the insert will be performed to establish the as-mounted resonance frequencies.
  • Data will be acquired for a longer time history to ensure adequate frequency resolution to measure any LFI behavior.
  • It is recommended that insert vibration be measured directly, but the staff believe that this is not yet confirmed (this should be defined in the final CVAP test document).
  • Test velocities should be based on estimated reduced flow velocities.
  • At least one million vibration cycles will be measured.

When evaluating the final design SGIFR testing requirements, the staff may use a COL item to have a future applicant include license conditions or Inspections, Tests, Analyses, and Acceptance Criteria (ITAAC) in the design certification to ensure planned testing includes multiple misalignment cases, including touching the tube sheet walls. Also, the testing should include accelerometers mounted to the inserts themselves. Finally, any operational biases/uncertainties associated with the final design mounting conditions should be evaluated in final testing. NuScale plans to submit the SGIFR test plan in the Measurement and Inspection

Report for the staff's review during the design certification.

TF1/TF2 Test Data NuScale provided the following test report for TF2:

  • ER-T050-6540, Revision 0, Evaluation of TF2 Strain Gage Data for Fluid-Elastic Instability Content.

NuScale also made available, raw test data acquired from SIET TF1 and TF2 testing, along with the commercial software Matlab so that the staff could compute frequency spectra for several test conditions, along with coherences and relative phasing between sensor locations. The staff confirmed that the internal flow rates in the TF1 and TF2 tubes are similar, with TF2 flow slightly

(~10 percent) lower than that of TF1. Although the TF1 and TF2 tests were primarily to evaluate thermal hydraulic performance, limited data were acquired to also assess FIV behavior, including internal loading due to secondary coolant flow, and external loading due to primary coolant flow which could lead to vortex shedding (VS) lock-in and Fluid-Elastic Instability (FEI).

TF1 testing was of the internal secondary coolant flow in three tubes of different helical sizes (inner, middle, outer in the SG) and included adiabatic and diabatic wall conditions. The internal flow was electrically heated to various temperatures and conditions (ranging from single phase water to two-phase boiling flow), with wall pressures measured at six locations along each tube.

In many test cases, a strong spectral pressure peak appears near [ ] in regions of boiling water flow. A literature search suggests this peak is characteristic of boiling water upward flow through tubing/piping. Literature identified by the staff on this phenomenon has been forwarded to NuScale for their consideration. NuScale has not yet assessed the potential impact of this strong pressure spectral peak on the SG tubing.

TF2 tube vibration data were also analyzed to assess if the [ ] loading existed in those tests. [

] Unfortunately, the TF2 data records are extremely short - [ ] - leading to very high spectral noise floors.

Computing cross-spectra between strain gages reduces the noise floors slightly, but not enough to reveal any [ ] spectral peaks. It is therefore not known if: (a) the [ ] internal loading is present in TF2, or (b) the loading is present, but the resulting tube response is below the noise floor of the measurements.

Some spectral peaks are evident in the TF2 strain spectra, but none are strong, and none increase with speed at a rate consistent with VS or FEI. However, the strain gages may not be close enough to the lower tube regions to discount the possible presence of VS. Also, ER-T050-6540 emphasizes that the TF2 test assembly was never intended to provide FIV data to support the CVAP. Most critically, the tube boundary conditions are significantly different in nature and located differently than those in the current design. After reviewing the TF2 data and reports, the staff has determined that those data are inappropriate for assessing FIV risks associated with VS and FEI. The planned TF3 testing is therefore a critical component of NuScales CVAP.

NuScale plans to simulate the TF2 tube strains using forcing functions which bound the TF1 wall pressure measurements and an FE model of the TF2 test configuration. While this is a

worthwhile exercise, the staff suggested to NuScale to also compute for the actual design the expected tube vibrations and alternating stresses induced by as measured TF1 internal pressures and confirm that these levels are within material acceptance limits.

The staff also analyzed the TF2 data to determine whether internal tube flow is necessary for upcoming TF3 testing. No significant increases in tube vibration response were observed in the presence of boiling secondary internal flow. However, the strain gage signals near the lower tube regions showed strong oscillations at very low frequencies. NuScale speculates these oscillations are due to thermal effects. While unexplained, these oscillations are clearly not associated with VS or FEI (or any other flow-induced mechanism) and are therefore not important. The staff concurs that TF3 testing may be restricted to primary coolant external flow only, provided NuScale computes the tube vibration and alternating stresses induced by internal flow per the paragraph above.

TF3 Testing Requirements Reports NuScale has provided two reports regarding TF3 SG testing plans:

  • ER-A014-2377, Revision 0 Test Development Plan for Flow-Induced Vibration of the NuScale Helical Coil Steam Generator.
  • EC-T050-6412, Revision 0, SG FIV Pre-Test Modal Analysis.

Unlike the TF1 and TF2 tests, the proposed TF3 HCSG testing is intended solely to quantify FIV mechanisms. Extensive instrumentation and testing is planned specifically to show that the

[ ]. While the current test plan seems rigorous, NuScale has proposed that TF3 testing be part of a license condition or ITAAC for the COL holder. NuScale currently plans to conduct many tests, which span ranges of operating conditions as well as mechanical conditions (radial preload, stiff vs. loose tube contact, perhaps others). NuScales goal is to use this database as a digital twin for future health monitoring of the reactor fleet.

The pre-test modal analysis document (EC-T050-6412) describes FE analyses used to determine likely mode shapes and resonance frequencies as well as optimal sensor locations for the TF3 testing. The SG FE models have been refined since the initial DCD submission, and include mesh refinement and boundary condition sensitivity studies. However, the FE document does not yet include results from the recent single tube modal testing which indicate stiffer boundary conditions than expected (stiffer than the original pinned assumptions used in the calculations submitted in the CVAP but not as stiff as fully clamped). The document compares mode shapes for pinned and clamped connections, and establishes FE mesh convergence for resonance frequency simulations.

The staff recommended to NuScale during the audit that they update the SG design calculations for FEI and VS to include SG tube boundary conditions validated using the single tube modal testing and update the CVAP accordingly. The updated boundary conditions should lead to higher tube resonance frequencies and increase margin against VS and FEI.

In the planned TF3 facility five individual tube arrays will be installed and tested. The five middle columns (9-13) of the full 21 column SG array will be installed and welded to the inlet and outlet tubesheets. Prototypic tube supports will be included. Although the largest tubes (column 21) with the lowest resonance frequencies most susceptible to VS and FEI are not

being tested, the testing flow speeds will be sufficiently high to establish conditions where VS and FEI occur. These test results will be used to extrapolate worst-case VS and FEI conditions for the largest tubes in the actual SG.

The specific TF3 test objectives are:

  • measure in-air and in-water natural frequencies, mode shapes, and damping of the tubes, including of the overall tube bundle assembly; and
  • measure primary flow dynamic pressure fluctuations and SG tube and tube support vibrations over a range of flow conditions, including very high flow rates to establish margins against tube VS and FEI.

Flow testing will be at low temperature and pressure, and will not include secondary coolant inside the tubing. Analyses of TF1 and TF2 test data confirm that the mass loading and flow excitation effects of internal secondary coolant may be addressed separately and that high pressure and temperature testing is not necessary to evaluate VS and FEI. The tube arrays will be installed using prototypic supports, and with jacking systems which press the tubes into the support tabs to emulate static preloading induced by thermal expansion effects (the tubes and supports are expected to expand at high temperatures, tightening the connections).

[

]. The preloading levels and their relation to expected thermal expansion effects have not yet been established. It is also not clear what vibration amplitudes will be specified for the damping measurements.

Experimental modal analyses will also be conducted on the full tube array assembly in air and in water. Exciters will be mounted at fixed tube locations in column 11 which will generate either white noise or tonal excitation near resonances. It is not clear if the full assembly modal tests and flow tests will be conducted with the same variable preloading that will be specified for the individual tube tests. NuScale should address this issue. It is critical to establish that thermal expansion effects are: (a) sufficient to preclude the possibility of any inactive tube supports and (b) quantitatively linked to the test preload conditions. If inactive supports cannot be ruled out, these conditions should also be tested in TF3.

Several tests at various primary coolant flow rates will be performed to investigate VS and FEI effects on the SG tubing. [

]. Although not expected, susceptibility of the entire tube assembly to FEI will be evaluated as well (critical velocities for FEI of global modes of the entire tube array are below design flow rates, but the modal masses of the full array modes are so high it is unlikely they can lock in to localized flow instabilities). Sampling rates of [ ] are planned which will be sufficient to measure signals at resonance frequencies up to 500 Hz - much higher than the tubing resonances which could lock in to VS or FEI loading. [ ] of data will be acquired for each test condition, which ensures frequency resolution sufficient to capture sharp peaks which occur at VS and FEI conditions. The staff recommended to NuScale during the audit that longer time records be acquired.

The descriptions of the steady state, VS, and FEI flow tests are unclear. Section 10.4 of the test plan states that flow rates during the VS and FEI tests would be slowly varied upward, with data continuously acquired. Certain flow rates are listed in the test plan where data are to be acquired for constant flow over two minute time intervals. The test document does not seem to mention any contingency for holding flow rates at conditions with unexpectedly high vibration response and acquiring additional datasets. This should be clarified in future documents.

The staff commented to NuScale that flow tests at variable preloading are highly recommended, as are accompanying full SG modal analysis tests (this is implied but not clearly specified in the current test plan). Varying preloading should lead to variable tube damping (presumably with lower preloading causing higher damping due to increased friction at looser supports). Previous VS and FEI tests of tubing arrays documented in the literature rely on varying both flow velocity and damping to establish critical velocities (critical velocity is proportional to damping raised to the power of a configuration dependent constant).

NuScales SG TF3 test planning document (ER-A014-2377), while encouraging, is not yet sufficient to confirm that VS and FEI will not occur in the NuScale SG. The staff should review the upcoming test plan documents scheduled for release later in 2018 to determine whether the test descriptions and commitments are adequate to use in a license condition or ITACC.

During the audit, NuScale stated that updated computational fluid dynamics analyses were conducted on the SG tube array that might be usable to estimate variability of tube gap velocity throughout the SG array. NuScale should provide a discussion of these updated analyses and gap velocities.

NuScale mentioned during the audit that an ovality manufacturing requirement of [ ]

will be specified for the tubes. It is unclear whether this is sufficient to ensure tight contact with the tabs. It is also unclear whether the tubes in TF3 will have a consistency requirement. Note this ovality requirement is not in the current test plan document.

Summarized below is a list of the main criteria that the staff will consider when determining the decision to postpone the SG tube TF3 testing to after design certification:

  • Update the SG design calculations for FEI and VS to include SG tube boundary conditions validated using the ongoing TF3 single tube modal testing and update the CVAP accordingly.
  • Perform quantitative thermal expansion analysis of the SG tubing and supports to demonstrate the lack of inactive tube support during plant operation.
  • Update turbulence buffeting calculations to address appropriate peak velocities for forcing function calculations and application of worst-case secondary coolant [ ]

loads from TF1 measurements to SG tubing.

  • NuScale stated during the audit that updated CFD analyses were performed on the SG tube array that might be usable to estimate variability of tube gap velocity throughout the SG array. Provide a discussion of these updated analyses and gap velocities.
  • Regarding TF3 testing:

o Flow tests at variable preloading are highly recommended, as are accompanying full SG modal analysis tests (this is implied but not clearly specified in the current test plan). The preloading amounts should be quantitatively linked to the SG tubing/support thermal expansion calculations.

o It is not clear if the full assembly modal tests and flow tests will be conducted with the same variable preloading that will be specified for the individual tube tests. Address this issue.

o The descriptions of the steady state, VS, and FEI flow tests are unclear. Section 10.4 of the test plan states that flow rates during the VS and FEI tests would be slowly varied upward, with data continuously acquired. Certain flow rates are listed in the test plan where data are to be acquired for constant flow over two minute time intervals. The test document does not seem to mention any contingency for holding flow rates at any conditions with unexpectedly high vibration response and acquiring additional datasets. This should be clarified in future documents.

o NuScale mentioned during the audit that an ovality manufacturing requirement of

[ ]. NuScale should address whether this requirement will be specified and sufficient to ensure tight contact with the support tabs.

Initial startup testing During the audit, the staff and NuScale engineers discussed primary objectives for possible instrumentation to be installed for initial startup testing. The staff clarified that its main objective is to detect any stronger than expected flow-induced vibration of reactor vessel internals (RVI),

but not benchmarking of NuScale FIV methods and analyses. The staff prioritized internal and external monitoring of vibrations of reactor internals such as the control rod drive shafts (CRDS), in-core instrument guide tubes (ICIGTs), SG, and the entire upper and lower riser structures. NuScale is considering this guidance, and agreed to provide proposals for suggested instrumentation and testing in future submissions, perhaps in the upcoming revisions of CVAP testing documents. During the audit discussions, NuScale mentioned the options of using some conventional sensors (strain gages and/or accelerometers) to detect, and if necessary, identify the location of any unexpected strong FIV in key RVI. NuScale also is considering using fiber optic probes to capture digital images of other components such as the top of SG and top of the upper support plate. Regardless of the types of instrumentation,

NuScale should also define and substantiate acceptance criteria for initial startup measurements.

Other Items NuScale stated that the CVAP and related internal documents will be updated to reflect engineering changes, such as those made to the upper regions of the CRDS and ICIGT to preclude VS; as well as updated FIV calculations.

NuScale is also updating the LFI document which will include more quantitative analyses of selected components (such as defining specific length/diameter (L/D), pressure drops, and flow velocities). The staff should review this document when the update is available.

The staff discussed during the audit that Revision 1 of the CVAP report (TR-0716-50439) does not include an assessment of the possibility of acoustic resonance (AR) within the reactor vent valves (RVVs) or reactor recirculation valves (RRVs) during emergency core cooling system (ECCS) operation. This assessment is needed for the staff to make a safety finding regarding the integrity of the valves, as well as reactor internals, during ECCS operation. The staff reviews dynamic system analysis of the reactor internals under both normal and transient conditions, including ECCS operation. NuScale is requested to provide AR assessments of the RVVs and RRVs during ECCS operation, including initial blowdown conditions where steam from the top of the reactor may be flowing through some valves.

U.S. NUCLEAR REGULATORY COMMISSION

SUMMARY

PHASE 2 AUDIT REPORT OF NUSCALE POWER, LLC, REACTOR INTERNALS COMPREHENSIVE VIBRATION ASSESSMENT PROGRAM LIST OF ATTENDEES September 5, 2018 - October 4, 2018 NRC Staff

Participants:

Yuken Wong, NRO Marieliz Vera Amadiz Stephen Hambric, (NRC Consultant)

NuScale (and other support organization)

Participants:

Olivia Hand JJ Arthur Tamas Liszkai Marty Bryan Renee Martin Edward Heald Wayne Massie Marty Bryan Enclosure 2

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