ML18254A340
| ML18254A340 | |
| Person / Time | |
|---|---|
| Site: | NuScale |
| Issue date: | 09/13/2018 |
| From: | Rani Franovich NRC/NRO/DLSE/LB1 |
| To: | Samson Lee NRC/NRO/DLSE/LB1 |
| Franovich R / 415-7334 | |
| References | |
| Download: ML18254A340 (7) | |
Text
September 13, 2018 MEMORANDUM TO:
Samuel S. Lee, Chief Licensing Branch 1 Division of Licensing, Siting and Environmental Analysis Office of New Reactors FROM:
Rani Franovich, Project Manager
/RA/
Licensing Branch 1 Division of Licensing, Siting and Environmental Analysis Office of New Reactors
SUBJECT:
U.S. NUCLEAR REGULATORY COMMISSION AUDIT OF THE PROBABILISTIC RISK ASSESSMENT AND SEVERE ACCIDENT EVALUATION OF THE NUSCALE POWER, LLC DESIGN As part of its safety review of the design certification application from NuScale Power, LLC (NuScale), the U.S. Nuclear Regulatory Commission (NRC) staff performed an audit of information supporting Chapters 19 and 17.4 of the final safety analysis report (FSAR) submitted with the application. In particular, the purpose of the audit was for the NRC staff to examine and evaluate documents that support responses to the staffs requests for additional information (RAIs) in Table 1. This examination and evaluation was intended to inform the NRC staffs review of the responses to the RAIs.
The audit commenced on March 6, 2018, and was originally scheduled to end on April 3, 2018.
Subsequently, the audit was extended to April 24, 2018, to provide additional time to complete the audit. The audit was conducted via the NuScale electronic reading room (ERR), in NuScales Rockville office, and through periodic telephone conversations between appropriate NRC and NuScale staff. An exit meeting was conducted on April 24, 2018, where the overall results of the audit were reported, and the ERR stayed open through May 18, 2018.
The audit was conducted per the audit plan issued March 5, 2018 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML18053A216).
CONTACT: Rani Franovich, NRO/DLSE (301) 415-7334
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Members of the audit team included the following NRC staff:
Mark Caruso (Office of New Reactors (NRO), Audit Lead)
Rani Franovich (NRO, Project Manager)
Michelle Hayes (NRO, Acting Chief of Probabilistic Risk Assessment and Severe Accidents Branch)
Jason Schaperow (NRO, Severe Accident Phenomenology)
Marie Pohida (NRO, Probabilistic Risk Analysis)
Tony Nakanishi (NRO, Probabilistic Risk Analysis)
Alissa Neuhausen (NRO, Seismic/Structural)
Shawn Campbell (Office of Nuclear Regulatory Research (RES), Severe Accident Phenomenology)
Hossein Esmaili (RES, Severe Accident Phenomenology)
Brad Harvey (NRO, Meteorology)
Keith Compton (RES, Accident Analysis)
Greg Makar (NRO, Materials/Structural)
Leslie Terry (NRO, Materials/Structural)
Patrick Purtscher (RES, Materials/Structural)
BP Jain (NRO, Seismic/Structural)
Audit Activities In accordance with the audit plan, the NRC staff examined documents supporting the RAI responses in Table 1. The complete list of documents examined by the NRC during the audit is provided in Table 2. During the course of the audit staff reviewed documents and asked questions for purposes of clarifying the information being reviewed.
The staff interacted with the following NuScale staff during audit discussions:
James Curry (Project Manager For Audit)
William Galyean (Probabilistic Risk Analysis)
Sarah Bristol (Probabilistic Risk Analysis)
Etienne Mullin (Probabilistic Risk Analysis)
Scott Weber (Probabilistic Risk Analysis)
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Luke Mcsweeney (Probabilistic Risk Analysis)
Grant Buster (Probabilistic Risk Analysis)
Audit Results For four of the RAIs, the document review and the dialogue between the staff and the applicant obviated the need for a formal supplemental RAI. For six of the RAIs, the applicant provided supplemental RAI responses to address the staffs outstanding information needs. For two of the RAIs, the staff is considering alternative approaches to resolve the issue. The audit results for each of the twelve RAIs included in the audit are provided in the last column of Table 1.
These results were discussed with the applicant during the audit exit meeting on April 24, 2018.
DATE 9/13/2018 9/13/2018
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Table 1: Summary of Audit Topics and Results NRC RAI Number NuScale RAI Response Number FSAR Section Audit topic Results 8882 RAIO-0817-55372 (ML17222A683) 19.2 Scrubbing of fission product aerosols by the reactor pool for a module drop accident.
NuScale issued supplemental RAI response RAIO-0618 (ML18165A438) to resolve outstanding issues.
8903 RAIO-0917-55876 (ML17251B163) 19.2 Bi-directional flow through reactor recirculation valves arresting core damage.
No outstanding issues.
8977 RAIO-1017-56550 (ML17284A652) 19.2 Large release definitions for at-power and shutdown (module drop) accidents.
NuScale issued supplemental RAI responses RAIO-0318-59269 (ML18085A516) and RAIO-0518-60189 (ML18145A136) to resolve outstanding issues.
9043 RAIO-1017-56516 (ML17283A413) 19.2 Corium retention in the reactor pressure vessel (RPV) lower plenum and the containment lower plenum by external cooling by water in the containment and in the reactor pool.
Due to phenomenological uncertainties, the staff continues to evaluate NuScales conclusion that core debris retention is assured.
8889 RAIO-0118-58186 (ML18016A240) 19.1 The probability of severe accident induced steam generator tube failure.
No outstanding issues.
91121 RAIO-1017-56897 (ML17303A578) 19.2 The potential for high pressure melt ejection of corium from the RPV to the containment to cause direct containment heating.
Due to phenomenological uncertainties, the staff is continues to evaluate this topic for resolution.
93672 Not applicable 19.2 The NRC staffs independent MELCOR confirmatory analysis.
No outstanding issues.
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NRC RAI Number NuScale RAI Response Number FSAR Section Audit topic Results 8899 RAIO-0118-58237 (ML18018B375) 19.1.5 Fragility calculations for reactor bay wall, reactor building (RBX) exterior wall, and RXB roof.
Bases for screening structures, systems, and components with fragilities below the plant-level high confidence of low probability of failure.
NuScale issued a supplemental RAI response to resolve outstanding issues.
8840 RAIO-0717-55003 (ML17262B215) 19.1.4 Containment isolation for loss of coolant accidents inside containment.
NuScale issued supplemental RAI responses RAIO-0518-59975 (ML18135A269) and RAIO-0718-60731 (ML18183A554) to resolve outstanding issues.
8926 RAIO-0917-56321 (ML17272B031) 19.1.6 Dropped module consequence analysis.
NuScale issued supplemental RAI response RAIO-0518-60115 (ML18141A882) to resolve outstanding issues.
91281 RAIO-0218-58534 (ML18036B203) 19.1 Module drop accident.
NuScale issued supplemental RAI response RAIO-0618-60457 (ML18165A431) to resolve outstanding issues.
8879 RAIO-0817-55698 (ML17241A139) 17.4 Expert panel decision-making process.
No outstanding issues.
Footnotes to Table 1:
1The applicants responses to RAIs 9128 and 9112 were added to the audit subsequent to issuing the audit plan.
2The issues identified in draft RAI 9112 were resolved as a result of the audit, so the RAI was not issued as final.
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Table 2: Documents in the Applicants Electronic Reading Room CFD SSC Classification Report - Rev2.pdf CFDS (B191) Data Sheet - Expert Panel Approved 10-27-16 Revised 12-8-16.pdf COR Energy Balance.pdf CVC (B010) 2019 Data Sheet - EP Approved 9-7-17 Revised 2-8-18.pdf CVCS SSC Classification Report Rev4.pdf Documents Supporting PRA Audit 2_042518.pdf ECN-P000-6271_R0_Evaluation of Additional MACCS Sensitivity Cases.pdf ER-P010-5689_R0.pdf ER-P020-3536_R0 with ECN.pdf ER-P020-4450_R0 with ECN.pdf ER-P060-5441_Rev_0.pdf ER-P060-5441_Rev_1.pdf ER-P060-7035 Rev 0.pdf ER-P060-7048 Rev 0.pdf ER-P060-7082_Rev_1_NRELAP5 Base Model.pdf ER-P060-7085 Revision 1, Dropped Module Consequence Analysis ECN P060-6053 Air as Fill Gas during Module Drop, Revision 0 ER_P030_5150_R0.pdf ER_P040_5858_R0.pdf List of Design Data Requested - Modified 3-27-2018.pdf NuScale IVR Discussion Slides.pdf PRA Audit 2_Question 0309-1.pdf PRA Audit 2_Question 0315-1.pdf PRA Audit 2_Question 0424-1 re. RAI 8977.pdf RAI_8840_Cl_Fail_Audit_Slides 2018-04-19.pdf RBC (F011) 2109 datasheet - Expert Panel Approved 9-21-2017.pdf RBC SSC Classification Report Rev 2-Signed.pdf Slides - SMA_042418.pdf TI-SGTF discussion slides Ver 3.pdf PRA_Audit_UHS_Modeling_8840.pdf PRA_Audit_HPME_Discussion.pdf RAI 8926 Air as Fill Gas Slides.pdf ECN-P060-6411, Aerosol Contribution to Dropped Module Dose Consequence