ML21130A363

Preparedness for Accident Tolerant Fuel Licensing, Including Higher Burnup and Enrichment - a Report for the Senate Committee on Appropriations and the House Committee on Appropriations Enclosure

ML21130A363
Person / Time
Issue date:	06/25/2021
From:	Christopher Hanson NRC/Chairman
To:	Delauro R, Leahy P US Congress, US HR (House of Representatives), US SEN (Senate)
Orenak M
Shared Package
ML21155A171	List: ML21130A363 ML21155A162
References
CORR-21-0043, SRM-OGC201228-2
Download: ML21130A363 (8)

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PREPAREDNESS FORACCIDENT TOLERANT FUELLICENSING, INCLUDING HIGHER BURNUP ANDENRICHMENT A Report forthe Senate Committee onAppropriations andthe House Committee onAppropriations pS REG(ff DA co 09 2.

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4AAAC BytheU.S. Nuclear Regulatory Commission Enclosure

Introduction TheU.S. Nuclear RegulatoryCommission (NRC) developed this report asdirected bythe explanatory statement accompanying the Consolidated Appropriations Act, 2021(Public Law 116-260). The explanatory statement directed theNRCtoreport ontheNRC's preparedness for licensingthe use of accidenttolerant fuel(ATF) with a focus onthose steps thatarebeing taken bythestaff to ensure that theagency isprepared toreview theexpected licensing requests, including those for higher burnup andincreased limits, enrichment levels.

Applicants aremovingforward with plans toseek approval tobatch load' fuel assemblies with twoATFtechnologies (coated cladding and doped p ellets)that mayhave h igher burnup limits andincreased enrichment by the mid-2020s. Theenrichment, fabrication, transportation, and useoftheATFfuel assembliesrequires NRClicensing review andapproval. TheNRChas already received somelicensing action requests for theuseofATF,including higher burnup limits andincreased enrichment levels. The current list ofthese submittals andtheir approvals, ifapplicable, canbefound ontheNRC's ATF public Webpage(Ref. 1).

TheNRCstaff assessed itsregulatory framework andfound the existing regulations and guidance aresuitable for reviews ofthe ATFconcepts (i.e., coated cladding anddoped pellets) expected tobesubmitted inthe near-term. TheNRC also considers the existing regulatory framework tobegenerally acceptable for licensingfuel with increased enrichment (from 5to approximately 10percent uranium-235 byweight) andhigher fuel burnup limits (from 62 to75 gigawatt-days permetric tonofuranium (GWd/MTU), rodaverage) inthe near-term. While the NRC's existing regulations andguidance support the reviewof ATF licensing actions, requests for enrichment limits higher than 5 percent uranium-235 byweight will require license amendments andexemptions. TheNRCwill continue tolook forways toenhance the regulatory framework through guidance andpossible rulemaking activities.

TheNRCcompleted orisperforming the activitiesdetailed inthis report to support the NRC's efforts tocomplete the licensing ofATF,including higher burnup limits andincreased enrichment, inparallel with theindustry's research anddevelopment efforts while maintaining reasonable assurance ofadequate protection ofpublic health andsafety, promoting the commondefense andsecurity, andprotecting theenvironment.

Accident Tolerant Fuel Project Plan While theNRCisready toreview andlicense ATF,higher burnup, andincreased enrichment submittals under the current regulatory framework, theNRCisalso taking steps tomakeagency processes moreefficient andeffective. TheNRChasdeveloped theATFProject Plan (Ref. 2) toprepare for reviews ofboth near-term andlonger-term ATFdesigns. TheProject Plan, revised inOctober 2019, addresses thecomplete nuclear fuelcycle, including fuel fabrication, fresh fuel transport, in-reactor requirements, andspent fuel storage andtransportation. The NRCstaff engaged extensively with stakeholders its inthedevelopment oftheplan, including licensees, nuclear fuel vendors, industry groups, nongovernmental organizations, and international counterparts, consistent with theNRC's Principles ofGoodRegulation and statutory requirements.

1 A batch load isthereplacement ofapproximately ofthefuel one-third assembles inthereactor coreaftereach operating cycle.

The Project Plan outlines anewapproach tofuel licensing inwhich theNRCengages with applicants earlierintheir research anddevelopment phase, inpart toidentify andresolve potential safety issues promptly. TheProject Plan also considers operational flexibilities that licensees may seekbased uponATFdesigns. Increased communication andengagement occur onmany fronts, including routine vendor status meetings, attendance atindustry conferences, and a significant increase inthe number andfrequency ofpresubmittal meetings.

These meetings allow the NRCandstakeholders toexchange information andincrease the efficiency ofthereview process. Additionally,theNRCholds meetings andissues communications tofurther support dialogue with stakeholders over specific technical or administrative issues.One valuable set ofmeetings isheld monthly with theU.S. Department ofEnergy (DOE). Inthese meetings, DOEshares information onATFstatus andresearch, which helps theNRCstaff toanticipate what reviews maybeneeded.

InApril 2021(Ref. 3), theNRCissued a finalreport based upon information gathering activities including, phenomena identification and ranking tables (PIRT) and seven f uelperformance literature reviews concerning near-term ATF concepts, including spent fuel transportation and storage, andreactor operating andaccident conditions. NRC-issued ATF-related documents canbefound ontheNRC's ATFpublic Webpage (Ref.4).

TheNRCisalso developing orrevising existing codes tobeused for independent confirmatory calculations. These confirmatory calculations provide insight into fuel andreactor systems behavior aswell aspotential consequences oftransient and accident scenarios andthe identification ofrisk-significant factors. TheNRCwill update its codes asdata andinformation arereceived.

Other General Preparatory Activities TheNRCisactively involved intwoElectric Power Research Instituteindustry research frameworks/groups that arecoordinating research onATF,higher burnup, and increased enrichment limits.Thefirst istheCollaborative Research onAdvanced Fuel Technologies (CRAFT) for L ight Water Reactors. Thesecond is theExtended Storage Collaboration Program. Participation inboth ofthese research frameworks/groups allows theNRC tobe better prepared toreview future licensing submittals duetoits heightened awareness of vendor plans andresearch activitiesandprovides theNRCthe opportunity tooffer feedback to stakeholders asappropriate.

TheNRCfrequently interacts with international counterparts andsubject matter experts through Nuclear Energy Agency (NEA) working groups-most notably theWorking Group on Fuel Safety-and through international cooperative research programs toexpand ourtechnical database andmaintain awareness ofrelevant policy andtechnical issues with ATF.Some notable international activitiesinclude:

TheOrganisation for Economic Co-operation andDevelopment (OECD)/NEA-supported Studsvik Cladding Integrity Project led byStudsvik inSweden hasprovided data onhigh burnup fuelandcladding performance during a simulated loss-of-coolant accident.

• TheJapan Atomic Energy Agency hasprovided data onchromia doped fuel performance during a reactivity-initiated accident conducted inits Nuclear Safety Research Reactor.

e TheNRCstaff participates intheCabri International Project,led bytheInstitute for Radiological Protection andNuclear Safety inFrance, which studies thebehavior of nuclear fuelandcladding during reactivity-initiated accidents.

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a TheNRCstaff isparticipating inthe OECD/NEA's QUENCH-ATF project through which it obtains data oncoated cladding behavior indesign-basis andbeyond-design-basis loss-of-coolant-accident conditions. TheNRCstaff isparticipating intheOECD/NEA Framework for Irradiation Experiments that waslaunched tocontinue the spiritof international cooperation andhighly-leveraged access tonuclear safety, fuels,and materials research that hasbeenlost with the2018closure oftheHalden reactor in Norway.

These international research programs enhance theNRC's understanding ofsafety significant fuel andthermal-hydraulic system behaviorandprovide valuable data todevelop andvalidate independent models for the NRC's confirmatory analysis codes.

Coated cladding, doped pellets, higher burnup limits, andincreased enrichments levelsare expected tobethefirst setoftechnologies submitted toNRCfor licensing review. Thenext sections describe theNRC's preparations for each ofthese technologies.

Coated Cladding Nuclear fuel vendors arecurrently researchingand testing fuel that uses a zirconium alloy cladding with a thin outer coating ofeither chromium or a proprietary material. This thincoating isintended toprovide resistance tocorrosion andwear and additional operational flexibilityfor power reactors. TheNRChasnotyetreceived anyin-reactor topical reports or license amendment applications for batch loads ofcoated cladding but hasactively engaged with stakeholders.

TheNRCisprepared toreview licensing submittals forcoated fuel rod cladding. Togetready, theNRCcontracted with nuclear fuels experts from DOE's PacificNorthwest National Laboratory (PNNL) toperform a literature review (Ref. 5)ondegradation and failure phenomena related totheATFconcept ofchromium-coated fuel rodcladding andtoconduct a PlRT exercise onthe topic. TheNRCthen published aninterim staffguidance (ISG) on the subject (Ref.6). This ISGisavailable for vendors toconsult inpreparing their topical report submittals, whichshould help toreduce thepotential for schedule uncertainty anddelays caused by submitting incomplete documents for review.

Withregard tolicensing thefront-end (i.e.,

enrichment, fuelfabrication, andfresh fuel transportation) andtheback-end fuel cycle(i.e., spent fuel transportation andstorage) for coated cladding, theNRCstaff hasreviewed theapplicable regulations andguidance andhasissued twoliterature reviews (Refs. 7 and8). Fromthese reports,theNRCdetermined that no additions ormodifications tothe front-end andback-end regulatory framework areneeded.

Therefore, theNRCisprepared toreview coated cladding front-end andback-end licensing actionsconsistent with theagency's safety-and-security mission andinparallel with the industry's efforts. TheNRChasalready reviewed andapproved twosubmittals (Refs.9 and10) that allow fuel vendors totransport fresh fuel with coated cladding.

DopedPellets Fuelvendors areresearching andtesting fuel pellets thatmixother materials, knownas dopants, into thepellet during themanufacturing process. These dopants change thephysical properties oftheresulting fuel pellet with thegoal ofproviding both operational andaccident condition benefits for power reactors.

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The NRC hasalready reviewed andapproved twodoped pellet topical reports forboiling water reactor fuels (Refs. 11 and 12) and a license amendment (Ref. 13), and the industry is currently researching doped pellets forpressurized water reactor fuels. Additionally, thestaff has reviewed NRC regulations andguidance for the front-end andback-end licensing ofdoped pellets and determined that noadditions ormodifications areneeded. Therefore, theNRCstaff isprepared to review pressurized water reactor doped pellet submittals anticipated from vendors Todate, the NRChasreviewed andapproved a request (Ref. 9)that allows a fuel vendor totransport fresh fuel with doped pellets.

Higher Burnup Thecurrent fuel burnup limits differ slightly among fuel vendors andfuel products, but fuel assemblies aregenerally limited to a maximum rod-average burnup of62GWd/MTU. Thereare potential applicants interested inraising this limit toaround 75GWd/MTU rodaverage. Burnup limits arenotspecified inanyregulations, butinsteadareincorporated intopower reactor licenses onceapproved intopical reports. Therefore, rulemaking isnotneeded inthis areaand thestaff will only need to review topical reports and license amendment in requests to order approve increased burnup limits.

Thephenomenon called fuel fragmentation, relocation, anddispersal (FFRD) andits possible resolutions areofsignificant interest tothe NRC.FFRD isthe fragmentation offuel pelletsdue toexpanding fission gasbubbles under accident conditions. Thehigher theburnup ofthe fuel during accidents, the smaller each fuel fragment becomes. These smallerpieces offuel may axially relocate within thefuel rodif therodballoons outward and may beejected into the reactor coolant flow if therodbursts. Thefuel vendors andlicensees mayaddress FFRDinthe licensing process toadopt higher burnup levels through modeling. Other possible methods for addressing FFRDarecurrently under development. Tobeaware ofthe progress inboth technical andlicensing areas ofFFRD,theNRCstaff isencouraging fuel vendors tohave preapplication meetings ontheir licensing approaches toFFRD,which three vendors have done todate. TheNRCstaff expects additional preapplication meetings oncevendors have further refined their approaches. Additionally, theNRC's participation inCRAFTwill allow theagency tounderstand potential applicants' approaches tofilling data gapsandthenewapproaches to licensing requests thatarebeing developed for FFRD.Finally, theNRCstaff isdeveloping a research information letter thatwill summarize theNRCstaff's understanding ofavailable research information related toFFRDandhowthe information canbeused todefine conservative limits fortheextent offuel fragmentation during a reactor accident, the amountof fuel that could potentially bereleased from the andthe rod, impact offragmentation onthe release ofgaseous radionuclides. TheNRCstaff currently plans toissue theresearch information letter bylate 2021for usebystakeholders.

Inaddition totheProject Plan, theNRChasproactively reached outtopotential applicants on higher burnup limits through twoNRC-led public workshops. Thefirst, which washeld on July 30,2020, included anoverview ofhigher burnup limits andincreased enrichment for levels thepublic andanexchange ofinformation focusing onthecomponents ofa quality submittal.

During thefollow-up workshop onJune10,2021, theNRCdiscussed theproposed research information letter, the environmental aspects ofhigher burnup limits, andhigher burnup spent fuel storage andtransportation issues. These twoworkshops provided a valuable exchange of information with a variety ofstakeholders.

TheNRCstaff hasreviewed theregulations andguidance fortheback-end licensing ofhigher burnup fuel anddetermined that noadditions ormodifications areneeded. Therefore, NRCis 4 -

prepared toreview these expected submittals. TheNRCdid notneed toreview theregulations and guidance for the front-endlicensing ofhigher burnup fuel because, from thefront-end perspective, higherburnup fuelisnodifferent from other fuel.

Increased Enrichment Asstated earlier in this report,the NRCconsiders theexisting regulatory framework tobe generally acceptable for licensing fuel with increased enrichment levels (from 5 to approximately 10percent uranium-235 byweight) inthe near-term using license amendments andexemptions.

Amendments would beneeded tochange the enrichment limit inindividual licenses, and exemptions would beneeded byeachlicensee that wishes toexceed the enrichment limits in theregulations.

Toefficiently support expected requests for increased enrichment levels, theNRCisexploring theregulatory options, includingthepossibility ofinitiating a rulemaking. Specifically, theNRC ispreliminarily exploring whether a rulemaking toamendTitle 10oftheCodeofFederal Regulations 50.68, "Criticality accident requirements," which places anenrichment of limit 5 percent onfresh fuel orrequires a criticality monitor tobeinuse,would becost beneficial.

TheNRCisstill inthe earlystages ofthis process and will continue toexplore potential regulatory options focusing onenrichments upto10 percent, which istherange ofinterest currently being expressed bypotential applicants. Enrichments upto20percent mayalso be given someconsideration asthe staff looks atpotentialregulatory changes.Depending onthe level ofpreapplication andother activities tangible interest expressed bypotential applicants, a rulemaking could possibly becompleted consistent with theindustry's plans toseek approval to batch load fuel with increased enrichment inthe mid-2020s, and licensees could request exemptions until thecompletion oftherulemaking. TheNRCwillcontinue togauge interestin pursuing higher enrichment levels andadjust its efforts aswarranted.

A keyelement for licensing increased fuel enrichment levels willbethe front-end ofthefuel cycle. TheNRCstaff reviewed theregulations andguidance forfront-end licensing for increased enrichment anddetermined that noadditions ormodifications areneeded. Therefore, theNRCisprepared toreview front-end licensing actions for increased enrichment levels and hasreviewed andapproved several licensing actions that serve aspreparatory steps to allow a fuel facility toachieve enrichments above 5weight percent (Refs. 15).addition, the 14and In NRChasissued oneapproval (Ref. 9) that allows a fuel vendor totransport fresh fuelrods with enrichments above 5 weight percent uranium-235.

Toensure that potential applicants understand theNRC's timelines for reviewing front-end licensing actions for increased enrichments, theNRCidentified enrichment facility path critical items for approving batch loadings in2023anddiscussed themina public letter totheNuclear Energy Institute (Ref. 16).

Iron-Chromium-Aluminum (FeCrAI) Cladding andLonger-Term Accident Tolerant Fuel Concepts TheNRCmonitors progress onthe development ofFeCrAl cladding andlonger-term ATF concepts. TheNRCstaff frequently engages with DOEandfuel vendors tounderstand the current status andfuture directionofthese concepts.

TheNRChasnotyetbeenprovided with relevant detailed schedules, specific physical characteristics, ortechnical data from vendors for FeCrAl orother longer-term ATFconcepts.

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The NRC staff has, however, begun preliminary research toprepare forthese reviews andto determine whether, andtowhat extent, changes totheexisting regulatory framework maybe needed to license these ATFtechnologies. With uncertainsubmittal timelines for these technologies, itwouldbepremature for theNRCtoundertake moreintensive preparatory activities at this time.

Conclusion TheNRCcontinuesto maximize its preparednesstolicense near-term ATFtechnologies (i.e.,coated cladding and doped pellets),higher burnup limits,andincreased enrichment levels, andisprepared toreviewrequested licensingactions forbatch loads. TheNRCwill continue to engage with potential applicants, licensees, andother external stakeholders toensure thatthe appropriate steps aretaken sothat ATF, higher burnup, andincreased enrichment licensing reviews areboth timely andcomplete, consistent with maintaining reasonable assurance of adequate protection ofpublic healthand safety, promotingthecommondefense andsecurity, andprotecting theenvironment.

References 1 NRCATFPublic Webpage, "ATF-relatedLicensing Actions,"

https://www.nrc.gov/reactors/atf/licensing-actions.html.

2. NRCATFProject Plan, Version 1.1,"Project Planto Prepare the U.S. Nuclear Regulatory Commission for EfficientandEffective Licensing ofAccidentTolerant Fuels,"

October 2019(Agencywide Documents Access andManagement System (ADAMS)

Accession No.ML19301B166).

3. NUREG/CR-7283, ERI/NRC 21-204, "Phenomena Identification Ranking Tables for Accident Tolerant Fuel Designs Applicable toSevere Accident Conditions," preparedfor theU.S. Nuclear Regulatory Commission byEnergy Research Inc.,April 2021 (ADAMS Accession No.ML21113A277).

4. NRCATFPublic Webpage, "ATF-related Documents,"

https://www.nrc.gov/reactors/atf/related-docs.htmi.

5. PNNL-28437, "Degradation andFailure Phenomena ofAccident Tolerant Fuel Concepts:

Chromium Coated zirconium Alloy Cladding," prepared fortheU.S. Department of Energy bythePacific Northwest National Laboratory, January 2019(ADAMS Accession No.ML19036A716) andPNNL-28437, Revision 1,June2019(ADAMS Accession No.

19172A154).

6. ATF-ISG-2020-01, "Supplemental Guidance Regarding theChromium-Coated zirconium Alloy Fuel Cladding Accident Tolerant Fuel Concept," January 2020(ADAMS Accession No.ML19343A121).

7. PNNL-29773, "Fresh Fuel Transportation ofAccident Tolerant Fuel Concepts -

Chromium Coated zirconium Alloy Cladding," prepared for theU.S. Department of Energy bythePacific Northwest National Laboratory, March 2020(ADAMS Accession No.ML20134H981).

8. PNNL-30451, "Spent Fuel Storage andTransportation ofAccident Tolerant Fuel Concepts -

Cr-Coated zirconium AlloyandFeCrAl Cladding," prepared fortheU.S.

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Department ofEnergy bythePacific Northwest National Laboratory, March 2020 (ADAMS Accession No. ML20274A250).

9. Letter fromJohn McKirgan, NRC,toTanya Sloma, Westinghouse Electric Company, LLC, "Revision No.12ofCertificate ofCompliance No.9297for theModel Nos.

Traveller STD, TravellerXL,andTraveller VVERPackages," September 15,2020 (ADAMS Accession No.ML20255A297).

10. Letter from John McKirgan, NRC,toTimothy J.Tate, Framatome Inc.,"Revision No.11 ofCertificate ofCompliance No.9319, for theModel Nos. MAP-12 andMAP-13 Transportation Packages," January 10,2019 (ADAMS Package Accession No.

ML19011A011).

11 Letter from Mirela Gavrilas, NRC, toJerald Head,General Electric-Hitachi, "Final Safety Evaluation for General Electric Hitachi Nuclear Energy Americas, LLCTopical Report NEDC-33406P, Revision 2,'Additive FuelPellets ForGNFFuel Designs' (TAC No.ME3082)" November 9,2015(ADAMS PackageAccession No.ML15195A459).

12. ANP-10340P-A, Revision 0,Incorporation ofChromia-Doped Fuel Properties inAREVA Approved Methods," Framatome Inc., May 2018 (ADAMS Accession No.

ML18171A119).

13. Letter from Andrew Hon,NRC,toJohn A.Krakuszeski, DukeEnergy Progress, LLC, "Brunswick Steam Electric Plant, Units 1and2 Issuance ofAmendment Nos.

299and 327toRevise Technical Specification 5.6.5b toAllowApplication ofAdvanced Framatome Atrium 11Fuel Methodologies (EPID L-2018-LLA-0273)," March 6,2020 (ADAMS Accession No.ML20073F186).

14. Letter from Jacob zimmerman, NRCtoWyatt Padgett, Louisiana Energy Services LLC, "U.S. Louisiana Energy Services -

Amendment 85,Change toLicense Condition 6band Enrichment Limit (Enterprise Project Identification Number L-2019-LLA-0264)," May19, 2020(ADAMS Package Accession No.ML20119A040).

15. Letter from Tyrone D.Naquin, NRC,toScott P.Murray, Global Nuclear Fuels-America, "Global Nuclear FuelAmericas LLC:Review oftheMinimum Margin ofSubcriticality for upto8 Weight Percent Enrichment ofUranium-235 andAmendment 16(Enterprise Project Identifier L-2020-LNS-0002)," August 13,2020(ADAMS Package AccessionNo.

ML20219A463).

16. Letter from Kathryn M.Brock, NRC,toJanet R.Schlueter, Nuclear Energy Institute, "Preparing for EfficientandEffective Licensing ofAccident Tolerant Fuel with Higher Enrichment," August 26,2019(ADAMS Package Accession No.ML19235A261).

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