ML19203A043

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Phase IV Regulatory Audit of NuScale Neutron Radiation Source Term
ML19203A043
Person / Time
Site: NuScale
Issue date: 07/25/2019
From: Getachew Tesfaye
NRC/NRO/DLSE/LB1
To: Samson Lee
NRC/NRO/DLSE/LB1
Tesfaye G / 415-8013
References
Download: ML19203A043 (14)
v • d • e


Text

July 25, 2019 MEMORANDUM TO: Samuel S. Lee, Chief Licensing Branch 1 Division of Licensing, Siting, and Environmental Analysis Office of New Reactors FROM: Getachew Tesfaye, Senior Project Manager /RA/

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

SUBJECT:

AUDIT

SUMMARY

FOR THE PHASE IV REGULATORY AUDIT OF THE EQUIPMENT QUALIFICATION AND RADIATION PROTECTION NEUTRON SOURCE TERM FOR NUSCALE POWER, LLC DESIGN CERTIFICATION APPLICATION By letter dated December 31, 2016, NuScale Power, LLC (NuScale), submitted to the U.S.

Nuclear Regulatory Commission (NRC), a Design Control Document for its Design Certification Application (DCA) of the NuScale small modular reactor (SMR) design (Agencywide Documents Access and Management System Accession No. ML17013A229). The NRC staff started its detailed technical review of NuScales DCA on March 27, 2017.

The purpose of this focused NRC Phase IV Regulatory Audit was for the NRC staff to obtain additional information related to needed clarifications identified in NuScales application for the type of radiation present; the quantity of radiation present; and the energy of that radiation as it is used to determine the dose rate and total dose from the incident neutron and gamma radiation. The NRC staff examined the induced gamma radiation from incident neutron radiation, gamma radiation resulting from decay of activated materials, and the technical bases for the stated values, in areas inside containment, under the bioshield and areas adjacent to the bioshield. The NRC staffs review included, but was not limited to, the information related to Requests Additional Information (RAI) 9282, 9291, 9447, and 9295. The NRC staffs review scope was communicated in the audit plan (ADAMS Accession No. ML19058A523). The audit process allowed the NRC staff to access information that was identified as potentially significant to the review, such as neutron fluence calculations, activation calculations, shielding calculations, equipment qualification, and other non-docketed information in NuScales Electronic Reading Room (eRR).

CONTACTS: Getachew Tesfaye, NRO/DLSE 301-415-3165

S. Lee 2 This audit took place at NuScales offices, in Rockville, Maryland, and/or via the NRC staffs review of electronic information to which NuScale granted electronic access to via the eRR.

The NRC staff used information available through the audit to examine the calculations for the above items provided by NuScale and, as necessary, held discussions with the applicant. The audit was conducted in accordance with the NRC Office of New Reactors (NRO) Office Instruction, NRO-REG-108, Regulatory Audits (ML081910260). The audit was conducted between February 11, 2019 and April 12, 2019. The audit exit was conducted on April 25, 2019.

Enclosed, are materials relevant to the closure of this audit. The enclosures are as follows: (1)

NuScale DCA Equipment Qualification and Radiation Protection Neutron Source Term Audit Report, (2) Summary of the NRC Staffs Audit Review, (3) Requests for Supplemental Information, and (4) Requests for Additional Information.

Docket No.52-048

Enclosures:

As stated cc w/ncl: DC NuScale Power LLC Listserv

ML19203A043 *via email NRO-002 OFFICE DLSE/RGRB DLSE/LB1: LA DLSE/RGRB: BC DLSE: DD DLSE/LB1: PM NAME RLaVera* MMoore* MDudek* ACampbell* GTesfaye DATE 07/09/2019 07/23/2019 07/20/2019 07/20/2019 07/25/2019 U.S. NUCLEAR REGULATORY COMMISSION NUSCALE POWER, LLC DESIGN CONTROL APPLICATION THE EQUIPMENT QUALIFICATION AND RADIATION PROTECTION NEUTRON SOURCE TERM AUDIT REPORT February 11, 2019- April 12, 2019

Background

The purpose of this U.S. Nuclear Regulatory Commissions (NRC) regulatory audit was to obtain additional information related to needed clarifications identified in NuScales application for the type of radiation present; the quantity of radiation present; and the energy of that radiation as it is used to determine the dose rate and total dose from the incident neutron and gamma radiation. The NRC staff examined the induced gamma radiation from incident neutron radiation, gamma radiation resulting from decay of activated materials, and the technical bases for the stated values, in areas inside containment, under the bioshield and areas adjacent to the bioshield. The NRC staff also:

  • Gained a better understanding of the NuScale Power, LLC., (NuScale) design from the review of calculation packages related to: Neutron fluence and spectra within the reactor vessel, the containment vessel, underneath the bioshield and outside of the bioshield; Gamma fluence within the reactor vessel, the containment vessel, underneath the bioshield and outside of the bioshield; and neutron activation of reactor and containment vessel components;
  • Assessed information submitted on the electronic Reading Room (eRR);
  • Identified information that will require docketing to support the licensing basis and/or regulatory decisions;
  • Reviewed related non-docketed information to allow the NRC staff to better inform their regulatory decision making; and
  • Reviewed the need for follow-up requests for additional information (RAI).

The NRC staff focused its review on information related to the environmental qualification (EQ) resulting from neutron and gamma sources of radiation, and to a lesser extent on some aspects of radiation protection (RP) for occupational workers. The NRC staffs review scope was communicated in the original audit plan was described in (Agencywide Documents Access and Management System Accession (ADAMS) No. ML18348A986). Due to scheduling considerations and the desire of NuScale and the NRC staff to maximize the benefits of the Audit, a revised audit plan (ADAMS No. ML19058A523) was issued.

Enclousre 1

Some of the RAIs with a nexus to the incident neutron and gamma fluence that were under review by the NRC staff included, but were not limited to:

  • RAI 9282 - Neutron Flux and Spectrum in Containment;
  • RAI 9291 - Gamma Fluence Under the Bioshield;
  • RAI 9447 - Bioshield Design;
  • RAI 9295 - Bioshield Wall Shielding The NRC staff also reviewed documents related to the following RAIs to aid with the closure of other open items:
  • RAI 9613, Question 12.02 Reactor Building Airborne activity
  • RAI 9266, Question 12.02 Reactor Building Airborne activity
  • RAI 9270 - Reactor Building Airborne activity
  • RAI 9284 - Smooth Surface Regulatory Basis The NRC staffs acceptance criteria are described in the Design Specific Review Standard (DSRS) Section 12.2, Radiation Sources (ML15350A320); DSRS Sections 12.3-12.4, Radiation Protection Design Features (ML15350A339); and DSRS Section 3.11, Environmental Qualification of Mechanical and Electrical Equipment (ML15355A455), and the SRP are based on meeting the relevant requirements of the following NRC regulations:

Audit Agenda The NRC staff held several meetings with the applicant throughout the audit at the NuScale office in Rockville, Maryland, at NRC Headquarters, or via telephone with NuScale. The NRC staff used these meetings to facilitate an understanding of the NuScale Design Certification Application (DCA), and the information the applicant had made available for review by the NRC staff.

February 11, 2019 Entrance Meeting April 2, 2019 Audit Meeting April 11, 2019 Audit Meeting April 25, 2019 Exit Meeting Audit Participants NRC Staff

Participants:

  • Albert Hathaway (RES, Reactor Systems Engineer)
  • Edward Stutzcage (NRO, Technical Reviewer)

NuScale

Participants:

  • Carrie Fosaaen (NuScale)
  • Mark Shaver
  • Jon Bristol
  • Jim Osborn Information Made Available by NuScale for Review by the NRC Staff During the audit, NuScale provided the NRC staff with electronic access to information used in the review of the equipment qualification and radiation protection neutron and gamma radiation sources. The type of information contained in the eRR included but was not limited to: Neutron fluence and spectra calculation packages, Gamma fluence calculation packages, the supporting design information referenced by the calculation packages, and other non-docketed information used by the NRC staff during the audit.

In the NuScale Rockville office, the NRC staff was given access to calculation files in native format. This included MCNP input/output files, SCALE/ORIGEN input/output files, excel files, and other files that supported the calculation packages provided on the eRR.

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Deviations from the Audit Plan The NRC staffs review scope as communicated in the original audit plan was described in (ADAMS No. ML18348A986). Due to scheduling considerations and the desire of NuScale and the NRC staff to maximize the benefits of the Audit, a revised audit plan (ADAMS No.

ML19058A523) was issued. Due to the rescheduled ACRS Subcommittee hearing, the audit started February 11, 2019, ended April 12, 2019, with the exit meeting held on April 25, 2019.

Audit Activities The DSRS and SRP are not a substitute for NRC regulations and compliance with them is not required. However, as an alternative, an applicant may identify any differences between a DSRS section and the design features, analytical techniques, and procedural measures proposed in an application and discuss how the proposed alternative provides an acceptable method of complying with NRC regulations that underlie the DSRS acceptance criteria. Where the DCA contents differed from the guidance contained in the DSRS, the NRC staff reviewed the associated analytical techniques, data and conclusions, associated with the proposed alternative.

Specifically, the NRC staff focused its review according to the information relayed in the audit plan (ML19058A523). The NRC staff used the supporting information contained in the DCA, eRR, and files provided at the NuScale offices. Where clarification of the information provided was needed, the NRC staff scheduled discussions with the applicant to communicate the NRC staffs review of the information provided on the eRR or in the NuScale Rockville office.

During the audit, the NRC staff used information provided in the NuScale Rockville office, the eRR and discussions with NuScale staff members to assess and hone the responses to RAIs, such as: RAI 9282 - (ML18067A570 and ML18361A905), RAI 9291 - (ML18058A720 and ML18332A397), RAI 9447 - (ML18320A253), RAI 9295 - (ML18128A390 and ML18235A648),

RAI 9613 - (ML18351A390), RAI 9266, Question 12.02 (ML18058A901), RAI 9270 -

(ML18155A622, ML18248A110 and ML18323A288), RAI 9284 - (ML18047A750 and ML18269A363) and RAI-9607 - (ML19129A492).

A summary of the NRC staffs review is found in Enclosure 2. Enclosure 3 contains a listing of the specific supplemental requests that were agreed upon with NuScale during the audit exit meeting. Enclosure 4 contains a listing of the additional RAIs generated as a result of the audit, that were discussed with NuScale during the audit exit meeting.

Audit Exit Summary The audit exit meeting was held on April 25, 2019, via teleconference. During the exit, the NRC staff described the specific areas reviewed during the audit (also found in Enclosure 2). The NRC staff identified one item for which the NRC staff is seeking a supplemental response.

There were no new items for which the NRC staff will be issuing follow-up RAIs. The one item that the NRC staff requested a supplemental response is described in Enclosure 3.

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List of acronyms and abbreviations ADAMS Agencywide Documents Access and Management System CNV Containment Vessel COL Combined Operating License DCA Design Certification Application DSRS NuScale Design Specific Review Standard EQ Environmental Qualification EPA Electrical Penetration Assembly eRR Electronic Reading Room F Fahrenheit FSAR Final Safety Analysis Report GDC General Design Criterion ITAAC Inspections, Tests, Analyses, and Acceptance Criteria keV Kilo Electron Volt LWR Light Water Reactor MeV Mega Electron Volt mR/hr Milli Roentgen per hour NPM Nuclear Power Module NRC U.S. Nuclear Regulatory Commission NRO Office of New Reactors PWR Pressurized Water Reactor P&ID Piping and instrumentation diagrams RAI Request for Additional Information RCS Reactor Coolant System RES/DSA/AAB Office of Research, Division of Systems Analysis, Accident Analysis Branch RG Regulatory Guide RGRB Radiation Protection and Geotechnical Review Branch RP Radiation Protection RPV Reactor Pressure Vessel RRV Reactor Recirculation Valve RXB Reactor Building SG Steam Generator SMR Small Modular Reactor SSC Structures, Systems, and Components SRP Standard Review Plan (NUREG-0800)

TS Technical Specifications UHS Ultimate Heat Sink U.S. United States 10 CFR Title 10 of the Code of Federal Regulations 5

U.S. NUCLEAR REGULATORY COMMISSION NUSCALE POWER, LLC DESIGN CONTROL APPLICATION THE EQUIPMENT QUALIFICATION AND RADIATION PROTECTION NEUTRON SOURCE TERM

SUMMARY

OF THE NRC STAFFS AUDIT REVIEW The discussions provided below are a summary of the U.S. Nuclear Regulatory Commission (NRC) staffs findings made and communicated during the audit exit meeting.

The Audit Plan for the Phase IV Equipment Qualification and Radiation Protection Audit is described in (Agencywide Documents Access and Management System Accession (ADAMS)

No. ML19058A523). The audit started February 11, 2019 and ended April 12, 2019. The audit exit meeting was held on April 25, 2019. The audit focused on the information related to the NRC staff understanding of the kinds and quantities of neutron and gamma radiation potentially affecting some Environmentally Qualified (EQ) structures, systems and components (SSC), as well as some aspects of radiation protection (RP) for occupational workers. This included but was not limited to: source term calculations; shielding and dose rate calculations, and equipment environmental qualification calculations. In addition, the NRC staff and NuScale personnel agreed to change the scope of the audit to facilitate interactions between the NRC staff and the applicant on several open RAIs not directly related to the characterization of neutron and gamma radiation fields.

The Audit team consisted of:

Michael Dudek (NRO/RPAC Branch Chief)

Timothy Drzewiecki (NRO, Technical Reviewer)

Zachary Gran (NRO, Technical Reviewer)

Alfred Hathaway (RES, Reactor Systems Engineer)

Ronald LaVera (NRO, Technical Reviewer)

Edward Stutzcage (NRO, Technical Reviewer)

Getachew Tesfaye (NRO, Senior Project Manager)

Some of the requests for additional information (RAIs) with a nexus to the incident neutron and gamma fluence that are under review by the NRC staff included, but are not limited to:

  • RAI 9282 - Neutron Flux and Spectrum in Containment;
  • RAI 9291 - Gamma Fluence Under the Bioshield;
  • RAI 9447 - Bioshield Design;
  • RAI 9295 - Bioshield Wall Shielding Enclosure 2

The NRC staff also reviewed documents related to the following RAIs to aid with the closure of other open items:

  • RAI 9613, Question 12.02 Reactor Building Airborne activity
  • RAI 9266, Question 12.02 Reactor Building Airborne activity
  • RAI 9270 - Reactor Building Airborne activity
  • RAI 9284 - Smooth Surface During the audit, through the review of calculation packages and the associated input files, output files and other electronic data files, the NRC staff examined the methods, models, and assumptions used by the applicant to determine neutron fluxes, spectra and dose rates; gamma fluxes, spectra and dose rates; and activation rates of some components. The NRC staff also reviewed how the applicant used the calculational methods described to determine the effectiveness of radiation shielding material provided for either the protection of structures, systems or components (SSCs) or for the protection of occupational workers.

During the review, the NRC staff identified some inconsistencies in the information provided in the calculation packages, within the input files provided, and within the electronic data files made available. Through conversations with the applicant, and through independent analysis, the NRC staff determined that the observed inconsistencies had, at most, a minor impact on the results of the analyses reviewed. Specifics regarding the evaluation of RAIs identified in the scope of the audit are listed below:

RAI 9282 - Neutron flux and spectrum inside containment The NRC staff noted that the information requested by the NRC staff is contained in in an MCNP output file listing the neutron fluence values for the Inner Containment Vessel (CNV) upper surface. After further discussions, NuScale agreed to provide a proprietary RAI response listing the identified information. The status of RAI-9282, Question 03.11-17 has been changed to Waiting for Response/Supplemental.

RAI 9447 - Bioshield Design The NRC staff reviewed the shielding analysis performed for the polyethylene neutron shielding provided for the front face of the bioshield cover. The NRC staff is satisfied that the borated polyethylene material and the shielding configuration employed has the capability to provide the dose rate reductions stated in the calculation packages. Based on the borated polyethylene material specification sheets provided by the applicant; conversations with the material vendor, and analysis by the NRC staff, the NRC staff determined that the material has the capability to provide acceptable neutron absorption capability for the design life of the plant, at the current power level. After further discussions, the NRC staff and NuScale personnel agreed on proposed verbiage that addressed the NRC staffs concerns regarding control of environmental conditions that could affect the neutron shielding capability. Based on these discussions, this portion of the RAI is considered confirmatory.

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RAI 9295 - Bioshield Wall Shielding The NRC staff reviewed the shielding and dose rate analysis for those portions of the bioshield area shielding by solid masses of concrete. The NRC staff does did not identify any issues with the shielding analysis of these areas. However, at the time of the conclusion of this audit on April 12, 2019, the NRC staff was awaiting a response to follow-up RAI 9656, Question 12.03-63 (ML19077A285) concerning the design of shielding for the penetrations. This RAI was not discussed during the audit.

RAI 9291 - Gamma Fluence Under the Bioshield The NRC staff reviewed the calculations and the associated input and output files used to calculate gamma dose rates inside containment (between the CNV and the Reactor Pressure Vessel (RPV)) and outside of containment. In general, the NRC staff determined that the calculations performed by the applicant to address n-gamma (gammas produced following the non-fission absorption of a neutron) and fission gammas (gammas produced during neutron induced fissions) were reasonable for: (1) areas above the reactor vessel inside of containment; (2) inside the bioshield above the containment; and (3) inside the lower elevations of the reactor building, adjacent to the Nuclear Power Module (NPM) bay.

However, while the applicant performed activation analysis for specific components (e.g., the reactor head bolts, and the reactor recirculation valves (RRV)), they did not perform activation analysis of materials of interest to the NRC staff, such as: (1) the reactor reflector blocks; (2) the CNV wall, (3) the RPV wall and the Steam Generator (SG) material at the elevation of the SGs; and (4) the upper portions of the CNV). The NRC staff determined through independent analysis that the activation of the reflector block material did not appreciably impact dose rates in either the Reactor Building (RXB) lower elevations, nor through streaming, to the CNV Electrical Penetration Assemblies (EPA). Analysis by the NRC staff indicated that the EPAs would be exposed to approximately an additional 100 milli Roentgen per hour (mR/hr) of gamma radiation due to activation of the upper CNV. During discussions with the applicant, the applicant noted that due to the predominance of the neutron radiation, fission gammas, and water activation gammas, that this value was consider by them to be negligible. In addition, the NRC staff examined how activation of structural materials could impact maintenance activities while the containment vessel is in the dry dock area. Independent analysis by the NRC staff indicated that the gamma dose rate outside of the containment vessel could increase by 50 to 100 mR/hr, due to activation of the CNV and RPV walls near the SGs when the upper containment vessel is located in the dry dock area of the RXB.

Because of the lower significance of the gamma spectrum on the dose rate calculations for equipment, the NRC staff determined that spectrum information was not required. As a result of this review and additional information provided by NuScale, the NRC staff changed the status of RAI-9291, Question 12.02-24, to Confirmatory.

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RXB Tritium Related RAIs As a result of the review of earlier RAI responses, the NRC staff noted that the tritium concentration in the RXB air above the Ultimate Heat Sink (UHS) pool had decrease and was not explained. The NRC staff asked NuScale to provide information that described the basis for the observed change. During the audit, the NRC staff reviewed the neutron fluxes and RCS masses used as the basis for determining the tritium production rate in the Reactor Coolant System (RCS). In addition, NuScale personnel explained how other changes to the assumptions used to model tritium in the RXB had affected the reported results. As a result of other NRC staff actions, the allowable maximum UHS pool temperature has been reduced from 140 °F to 110 °F (see the response to RAI 9482 06.02.01.01.A-18 provided in ML18304A128). The reduced maximum pool temperature, in association with the reduced tritium inventory in the UHS pool results in radiological conditions more amenable to control thoroughly aspects of the radiation protection program, than previously considered. While the NRC staff does not agree with the rationale presented by the applicant in the responses to these RAIs, independent analysis performed by the NRC staff during the audit showed that there was a minimal increase in the radiological hazard. As a result, the NRC staff closed RAI 9613, Question 12.02-33, the follow up question to RAI 9266, Question 12.02 Reactor Building Airborne activity, and changed RAI 9270, Question 12.02-20 to Confirmatory.

RAI-9607 - Crud Burst During the audit, the NuScale personnel and NRC staff personnel discussed proposed resolutions to RAI-9607, Question 12.02-34. As a result of the conversations, the NRC staff and NuScale agreed to specific changes to the FSAR that satisfied the NRC staffs concerns. The NRC staff changed the status of RAI-9607, Question 12.02-34 to Confirmatory.

RAI 9284 - Smooth Surface During the audit, the NuScale personnel and NRC staff personnel discussed proposed resolutions to RAI-9284, Question 12.03-29. As a result of those conversations, the NRC staff has changed RAI-9284, Question 12.03-29 to Confirmatory. Based on internal NRC staff review, the status of RAI-9284, Question 12.03-30 has been changed to Resolved/Closed.

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U.S. NUCLEAR REGULATORY COMMISSION NUSCALE POWER, LLC. DESIGN CONTROL APPLICATION THE EQUIPMENT QUALIFICATION AND RADIATION PROTECTION NEUTRON SOURCE TERM REQUESTS FOR SUPPLEMENTAL INFORMATION The requests for supplemental information listed below is the items identified by the U.S.

Nuclear Regulatory Commission (NRC) staff that did not warrant an additional request for additional information (RAI), but was considered a technical issue that NuScale Power, LLC.

(NuScale), had agreed to supplement. The NRC staff will review the information supplemented in the updated response at that time it is submitted to the NRC on the docket and made available for review.

As agreed during the audit exit meeting, NuScale will submit a supplemental response to the NRC for the following:

Topic Issue Action RAI-9282, Question Neutron Flux and Spectrum NuScale agreed to provide a 03.11-17 inside containment proprietary RAI response that will include the requested information on the docket.

Enclosure 3

U.S. NUCLEAR REGULATORY COMMISSION NUSCALE POWER, LLC. DESIGN CONTROL APPLICATION THE EQUIPMENT QUALIFICATION AND RADIATION PROTECTION NEUTRON SOURCE TERM REQUESTS FOR ADDITIONAL INFORMATION The requests for additional information (RAI) listed below are those items identified by the U.S.

Nuclear Regulatory Commission (NRC) staff that were not resolved during the audit, and were considered technical issues that NuScale Power, LLC. (NuScale) had agreed with the NRC staff on submitting. The NRC staff will review the information provided in the RAI responses at that time they are submitted to the NRC on the docket and made available for review.

There were no new RAIs generated during this audit.

Enclosure 4

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