ML22014A112

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Regulatory Framework Applicability Assessment and Licensing Pathway Diagram for the Licensing of ATF-Concept, Higher Burnup, and Increased Enrichment Fuels
ML22014A112
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Issue date: 05/04/2022
From: Michael Wentzel
Licensing Processes Branch
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Wentzel M
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Regulatory Framework Applicability Assessment and Licensing Pathway Diagram for the Licensing of ATF-Concept, Higher Burnup, and Increased Enrichment Fuels MAY, 2022

ML22014A112 OFFICE NRR/DORL/LP2-2/PM NRR/DORL/LP2-2/LA NRR/DORL/LP2- OGC - NLO NAME MWentzel RButler DWrona NMertz DATE 2/1/2022 1/24/2022 2/9/2022 4/27/2022 OFFICE NMSS/DFM/D NMSS/REFS/D NRR/DRA/D RES/DSA/D NAME Shelton JTappert MFranovich KWebber DATE 2/9/2022 2/16/2022 2/4/2022 2/4/2022 OFFICE NRR/DSS/D NRR/DORL/D NAME JDonoghue BPham DATE 5/2/2022 5/4/2022

1. Background In preparation for forthcoming submittals of topical reports (TRs) and license amendment requests (LARs) from vendors and licensees requesting the approval of near-term ATF concept, higher burnup, and increased enrichment fuels, the staff performed an assessment of the applicability of existing regulations and guidance for the licensing of these fuel types. Near-term ATF concepts are those for which the agency can largely rely on existing data, models, and methods for its safety evaluations. Coated cladding and doped UO2 pellets are the current near-term ATF concepts. This document contains the results of this assessment, referred to as the Regulatory Framework Applicability Assessment (RFAA), as shown in Table 2-1, below.

The U.S. Nuclear Regulatory Commission (NRC) staff does not consider the RFAA table to be exhaustive and will update it, as necessary, as more information is developed.

In conjunction with the RFAA table, the NRC staff has developed a licensing pathway diagram that provides a potential approach to licensing these fuel types.

2. Regulatory Framework Applicability Assessment As stated in Section 1, the NRC staff determined the applicability of existing regulations and guidance for near-term ATF concept, higher burnup, and increased enrichment fuels. The NRC staff assessed each regulation and guidance document listed in the table for whether it was fully applicable to ATF, higher burnup, and increased enrichment fuels. If the NRC staff determined that a regulation or guidance did not account for a particular phenomenon, the RFAA table identifies this fact and provides an explanation for the determination. In the RFAA table, a regulation or guidance document that is listed as not being not fully applicable means that the staff foresees potential hurdles if the regulation or guidance is applied to a particular concept in the table. For example, some guidance may not address phenomena unique to high burnup, increased enrichment, or near-term ATF concept fuels and some regulations or guidance have stated limits of applicability that would be challenged if the regulation or guidance were used for these concepts. In some instances, the applicability of the regulation or guidance document is irrelevant because other regulations or guidance replace or supersede it. In other instances, other regulations and guidance documents do not supersede the relevant regulation or guidance document but the efficiency of the NRCs review does not depend on the evaluated regulation or guidance document being fully applicable. For some cases where the regulation or guidance document is not fully applicable, but full applicability will increase NRC review efficiency, the NRC staff has already discussed the matter in public meetings and has determined a path towards achieving full applicability. In those cases, the RFAA table will state the relevant closure path. In other cases, a closure path has not yet been determined upon and the table will indicate as such. The RFAA table also makes note of some information an applicant could consider to ensure they correctly apply the regulation or guidance while developing a submittal. Finally, the NRC staff notes that the RFAA table is provided for informational purposes only. The RFAA table is intended to inform discussions at meetings between the NRC, industry, and the public. The results of the staffs assessment do not supersede any regulations or guidance and the information presented in the table should not be interpreted as new regulatory requirements or guidance.

Table 2-1 Key Green: actions for NRC Fully applicable: the document can be applied to the concept Not fully applicable: the staff foresees potential hurdles if the document or parts of the document in its current form are applied to the concept, reasons for which are detailed. Staff may recommend changes to the document or supplemental information to justify the use of the document with a particular concept the concept.

Priority: items listed as high priority; near-term are items the NRC staff is currently working on and are estimated to be completed within a 1.5 year timeframe. The NRC staff estimates that actions listed as medium priority; medium-term will be completed within a 5-year timeframe and that actions listed as low priority; long-term will take longer than 5 years to complete.

AST: alternate source term B&W: Babcock and Wilcox BU: burnup CATEX: categorical exclusion CE: Combustion Engineering GE: General Electric EA: environmental assessment FFRD: fuel fragmentation, relocation, and dispersal FGR: fission gas release GWd/MTU: gigawatt day per metric ton of uranium HBU: higher burnup (i.e., burnup that exceeds current licensing limits of 62 GWd/MTU. In this document two proposed burnup limits above 62 GWd/MTU are examined, 68 and 75 GWd/MTU)

LAR: license amendment request LOCA: loss of coolant accident MHA: maximum hypothetical accident RES: the NRCs Office of Research RG: regulatory guide RIA: reactivity-initiated accident RIL: research information letter RXA: recrystallized annealed SRP: NRC standard review plan STS: standard technical specifications TS: technical specifications Wt%: weight-percent 2

Table 2-1: Regulatory Framework Applicability Assessment 235 Guidance Burnup to Burnup to U Enrichment Chromium-coated Doped UO2 Fuel

  1. Document beyond 5.0 wt% Zirconium Cladding Pellets Regulation 68 GWd/MTU 75 GWd/MTU RG 1.183ASTs for Fully applicable Fully applicable Fully applicable Fully applicable Fully applicable Evaluating Design No data gaps No data gaps No data gaps No data gaps No data gaps Basis Accidents at Nuclear Power Reactors 1 Draft Revision 1 (ML21204A065)

Analytical guidance for predicting dose RG 1.183ASTs for Not fully applicable Not fully applicable Fully applicable Fully applicable Fully applicable Evaluating Design Reason: Reason: SAND- No data gaps No data gaps No data gaps Basis Accidents at Fragmentation- 2011-0128 is not Nuclear Power induced FGR of validated to Reactors high burnup fuel 75 GWd/MTU pellets may change Closure: Re-analysis Draft Revision 1 MHA/LOCA source of SAND-2011-0128 (ML21204A065) term and timing of to higher BU is being releases conducted by RES 2 Closure: Informal and Sandia National MHA/LOCA source assistance request Laboratory through terms to RES addresses 75 GWd/MTU this (available in Priority: High; near-ADAMS at term accession number Reason:

ML21197A062); Fragmentation-insights from this induced FGR of informal assistance high burnup fuel request to be pellets may change MHA/LOCA source 3

235 Guidance Burnup to Burnup to U Enrichment Chromium-coated Doped UO2 Fuel

  1. Document beyond 5.0 wt% Zirconium Cladding Pellets Regulation 68 GWd/MTU 75 GWd/MTU incorporated in term and timing of RG 1.183 Rev. 1 releases Priority: High; near- Closure: Informal term assistance request to RES addresses this (available in ADAMS at accession number ML21197A062);

insights from this informal assistance request to be incorporated in RG 1.183 Rev. 1 Priority: High; near-term RG 1.183 ASTs for Not fully applicable Not fully applicable Analytical Fully applicable Not fully Evaluating Design Reason: Analytical procedure procedure remains No data gaps applicable Basis Accidents at Fragmentation- remains applicable applicable Analytical Nuclear Power induced FGR of Tables 3 and 4 not Table 3 remains procedure Reactors high burnup fuel applicable applicable remains pellets may change Note: The FAST Note: With respect applicable Draft Revision 1 non-LOCA steady to Table 4, extent Tables 3 and 4 not (Fuel Analysis under (ML21204A065) state and transient of 235U enrichment applicable Steady-state and source term Transients) code is in RIA empirical Note: FAST is not 3 Closure: Revision 1 not validated up to database unknown. validated for Non-LOCA steady- of RG 1.183 will 75 GWd/MTU. RES Analytical doped fuel. RES state and transient address this. is working on the procedure can be is working on releases Priority: High; near- validation of FAST used in lieu of validation of FAST term models to higher Table 4. models to doped burnup. A data fuel. A data needs report has needs report has been issued from been issued from RES to examine RES to examine what specifically is what specifically is needed to expand needed to expand 4

235 Guidance Burnup to Burnup to U Enrichment Chromium-coated Doped UO2 Fuel

  1. Document beyond 5.0 wt% Zirconium Cladding Pellets Regulation 68 GWd/MTU 75 GWd/MTU the FAST the FAST capabilities to capabilities to 75 GWd/MTU doped pellets Reason: Reason: RIA Fragmentation- transient FGR for induced FGR of doped fuel has not high burnup fuel been well pellets may change quantified source term Closure: RIA Closure: Revision 1 transient FGR data of RG 1.183 will for doped fuel are address this. likely necessary Priority: High; near-term Reason: RIA transient FGR is not currently well quantified up to 75 GWd/MTU Closure: RIA transient FGR data may be helpful for quantifying HBU FGR 5

235 Guidance Burnup to Burnup to U Enrichment Chromium-coated Doped UO2 Fuel

  1. Document beyond 5.0 wt% Zirconium Cladding Pellets Regulation 68 GWd/MTU 75 GWd/MTU RG 1.195 Methods Not fully applicable Not fully applicable Fully applicable Not fully applicable Not fully and Assumptions for Reason: Validated Reason: Validated No data gaps Reason: Non- applicable Evaluating only up to only up to 62 LOCA accident Reason: Non-Radiological 62 GWd/MTU for GWd/MTU for non- release fractions LOCA accident Consequences of non-LOCA LOCA accidents are not validated release fractions Design Basis accidents Closure: No closure for rods with are not validated Accidents at Light- Closure: No closure necessary. HBU coated cladding for doped fuel Water Power necessary. HBU release fractions Closure: No pellets 4 Reactors release fractions and source term to closure necessary. Closure: No (ML03490640) and source term to be addressed by Analytical closure Release fractions be addressed by RG 1.183 Rev. 1. procedure outlined necessary.

from TID-14844 RG 1.183 Rev. 1. in RG 1.183 Rev. 1 Analytical can be applied to procedure coated cladding. outlined in RG 1.183 Rev. 1 can be applied to doped fuel.

RG 1.236 PWR Fully applicable Not fully applicable Not fully applicable Not fully applicable Not fully Control Rod Ejection No data gaps Note: Empirical Reason: Stated Reason: Stated applicable and BWR Control database limited applicability limited applicability is Reason: Stated Rod Drop Accidents beyond 68 to 5.0 wt%. limited to current applicability is (ADAMS Accession GWd/MTU. Increased LWR fuel rod limited to current No. ML20055F490) Reason: FFRD as a enrichment could designs LWR fuel rod result of HBU and potentially lead to Closure: Thin designs and possible loss of higher rod worth coating not doped fuel RIA 5 coolable geometry and peaking expected to performance has during RIA has not factors significantly alter not been well been well quantified Closure: RIA fuel rod response. quantified.

or understood experimental data Cladding failure Closure: Data for Closure: RIA data for fuel with thresholds and irradiated, doped on HBU fuel rod increased damaged core UO2 fuel pellets segments with enrichment may be coolability limits and integral fuel deposited energy helpful to remain applicable. burnable absorber beyond predicted demonstrate the No data gaps fuel pellets may be cladding damage helpful to better 6

235 Guidance Burnup to Burnup to U Enrichment Chromium-coated Doped UO2 Fuel

  1. Document beyond 5.0 wt% Zirconium Cladding Pellets Regulation 68 GWd/MTU 75 GWd/MTU may be helpful to RG 1.236 limits Note: Guidance understand impact investigate FFRD remain applicable states that coated of additive agents and loss of coolable Note: Extent of 235U claddings will be (e.g., larger grain geometry. Ideally, enrichment in RIA addressed on a size, retained these data would empirical database case-by-case basis fission gas, grain also include unknown. boundary hold-up, transient FGR. thermal conductivity) on Reason: HBU cladding failure effects on RIA not thresholds, FFRD, well quantified. transient FGR, and HBU cladding coolable geometry.

failure thresholds Note: Guidance should be defined. states that doped Closure: RIA data pellets will be on HBU fuel rod addressed on a segments, case-by-case especially RXA basis.

cladding, with low corrosion may be helpful to better understand burnup-effects and define cladding failure thresholds.

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235 Guidance Burnup to Burnup to U Enrichment Chromium-coated Doped UO2 Fuel

  1. Document beyond 5.0 wt% Zirconium Cladding Pellets Regulation 68 GWd/MTU 75 GWd/MTU 10 CFR 50.46 Fully applicable Fully applicable Fully applicable Not fully applicable Fully applicable LOCA Prescriptive Note: 50.46 does Note: 50.46 does No data gaps Reason: No data gaps Analytical not address recent not address recent 50.46(a)(1)(i) only Requirements HBU LOCA findings HBU LOCA findings speaks to zircaloy documented in documented in and ZIRLO cladded NUREG/CR-7219. NUREG/CR-7219. fuel. Closure: An 50.46c rulemaking 50.46c rulemaking applicant will need is being conducted is being conducted to meet the to address HBU to address HBU analytical 6

phenomena in the phenomena in the requirements.

regulations. Ideally, regulations. Ideally, Exemption industry submittals industry submittals requests may have should discuss the should discuss the to be submitted.

recent LOCA recent LOCA Refer to coated findings in findings per cladding interim NUREG/CR-7219. NUREG/CR-7219. staff guidance (ML19343A121).

8

235 Guidance Burnup to Burnup to U Enrichment Chromium-coated Doped UO2 Fuel

  1. Document beyond 5.0 wt% Zirconium Cladding Pellets Regulation 68 GWd/MTU 75 GWd/MTU LOCA Embrittlement Fully applicable Fully applicable Fully applicable Fully applicable Fully applicable Research Findings Large population of Large population of No data gaps Rate for oxidation Large population fuel rods beyond fuel rods beyond and embrittlement of fuel rods threshold for threshold for different from bare beyond threshold cladding inner cladding inner zirconium for cladding inner

- Draft RG 1.222 Measuring diameter oxygen diameter oxygen Note: Single sided diameter oxygen embrittlement. embrittlement. steam oxidation embrittlement Breakaway Oxidation Behavior data and Note: Hot cell post (ML15281A170) subsequent irradiation mechanical data as examination data 7 - Draft RG 1.223 well as double may be helpful to Determining Post sided integral define threshold Quench Ductility steam oxidation for fuel-clad bond (ML15281A188) data and layer.

subsequent

- Draft RG 1.224 mechanical data Establishing are necessary to Analytical Limits for establish post Zirconium-Alloy quench ductility Cladding Material limits.

(ML15281A192) 9

235 Guidance Burnup to Burnup to U Enrichment Chromium-coated Doped UO2 Fuel

  1. Document beyond 5.0 wt% Zirconium Cladding Pellets Regulation 68 GWd/MTU 75 GWd/MTU Standard Technical TS 4.2.1 and 4.3.1 TS 4.2.1 and 4.3.1 TS 4.2.1 is fully TS 4.2.1 is fully TS 4.2.1 is fully Specifications (STS) are fully applicable are fully applicable applicable applicable applicable No data gaps No data gaps NRC and TSTF to Note: Licensees Note: Licensees NUREG-1430, Rev. 5 discuss whether or should specify should specify STS - B&W Plants not the term chromium coated doped pellets in TS (ML21272A363): Figure 3.7.16-1, Figure 3.7.16-1, slightly in TS 4.2.1 cladding in TS 4.2.1 4.2.1 with LAR.

Figure 3.7.16-1 3.7.17-1, and 3.7.18- 3.7.17-1, and 3.7.18- includes fuels with LAR.

4.2.1 1 are fully applicable 1 are fully applicable enriched beyond 5%

4.3.1 Note: Licensees Note: Licensees should provide plant- should provide plant-NUREG-1431, Rev. 4 specific figure for TS specific figure for TS STS - Westinghouse with LAR. with LAR.

Plants (ML12100A222):

Figure 3.7.17-1 4.2.1 8 4.3.1 NUREG-1432, Rev. 4 STS CE Plants (ML12102A165):

Figure 3.7.18-1 4.2.1 4.3.1 NUREG-1433 and -

NUREG-1434, Rev. 4 STS GE Plants (ML12104A192 and ML12104A195, respectively):

4.2.1 4.3.1 10 CFR 50.67 9 Accident Source Potential impacts to accident source term described above for RG 1.183 Revision 1.

Term 10

235 Guidance Burnup to Burnup to U Enrichment Chromium-coated Doped UO2 Fuel

  1. Document beyond 5.0 wt% Zirconium Cladding Pellets Regulation 68 GWd/MTU 75 GWd/MTU 10 CFR 50.68 Fully applicable Fully applicable Fully applicable Fully applicable Fully applicable Criticality Accident No data gaps No data gaps Note: 5 wt% No data gaps No data gaps Requirements enrichment limit (without criticality monitoring system) explicitly stated, thus, licensees can submit exemption requests or, as stated in 50.68, adopt 70.24. See below for a discussion of 70.24s applicability.

In December 2021, NRC staff issued SECY-21-0109, 10 Rulemaking plan on Use of Increased Enrichment of Conventional and Accident Tolerant Fuel Designs for Light Water Reactors" (ML21232A237).

As a part of this rulemaking plan, the NRC stated plans to amend the 5 wt%

enrichment limit in 50.68.

Note: Criticality analyses may need to be updated.

11

235 Guidance Burnup to Burnup to U Enrichment Chromium-coated Doped UO2 Fuel

  1. Document beyond 5.0 wt% Zirconium Cladding Pellets Regulation 68 GWd/MTU 75 GWd/MTU 10 CFR Part 50 Fully applicable Fully applicable Fully applicable Not fully applicable Fully applicable Appendix K: ECCS Note: Appendix K Note: Appendix K No data gaps Reason: The Baker- No data gaps Evaluation Models does not address does not address Just metal-water recent updates to recent updates to reaction rate physical phenomena. physical phenomena. correlation is not For example, thermal For example, thermal applicable to coated conductivity conductivity cladding, as it was degradation (TCD) is degradation (TCD) is developed for bare not addressed. TCD not addressed. TCD zircaloy cladding occurs under HBU occurs under HBU Closure: An conditions. More conditions. More oxidation kinetics information on TCD information on TCD model based on is available in is available in chromium-coated Information Notice Information Notice cladding should be 2009-23 2009-23 developed. If the (ML091550527 and (ML091550527 and benefits of the ML121730336). ML121730336). coating are not to be Note: FFRD is not Note: FFRD is not realized and the 11 addressed. FFRD addressed. FFRD Baker-Just should be addressed should be addressed correlation is used, it in LOCA evaluation in LOCA evaluation should be methodologies. If methodologies. If demonstrated that it burst and, thus, burst and, thus, bounds the coated FFRD is expected to FFRD is expected to cladding oxidation occur, technical occur, technical kinetics.

justification for the justification for the Note: Coated threshold (e.g., BU) threshold (e.g., BU) cladding may have for which FFRD is to for which FFRD is to an impact on be considered may be considered may thermal-hydraulics, be helpful, as well as be helpful, as well as e.g., changes in a technical a technical wettability and justification for when justification for when hydraulic diameter the effect of the effect of can affect the critical fragmentation- fragmentation- heat flux/critical induced FGR is to be induced FGR is to be power correlation.

considered. The considered. The Emissivity also has limiting condition for limiting condition for the potential to be rupture with rupture with significantly 12

235 Guidance Burnup to Burnup to U Enrichment Chromium-coated Doped UO2 Fuel

  1. Document beyond 5.0 wt% Zirconium Cladding Pellets Regulation 68 GWd/MTU 75 GWd/MTU fragmentation should fragmentation should different, so be analyzed as well. be analyzed as well. consideration to this Additionally, Additionally, and other surface examining the impact examining the impact conditions is of fuel of fuel important when fragment/particle fragment/particle modeling coated transport and transport and cladding. Although deposition on deposition on thermal-hydraulic coolability and coolability and impact of coated criticality, including criticality, including cladding is expected addressing potential addressing potential to be minimal, this sump blockage sump blockage should be justified to caused by fuel caused by fuel confirm the fragments/particles in fragments/particles in continued the coolant may be the coolant may be applicability of helpful to better helpful to better thermal-hydraulic understand the understand the models.

effects of FFRD. effects of FFRD.

Note: The NRCs Note: The NRCs understanding of understanding of recent FFRD recent FFRD research is research is documented in RIL documented in RIL 2021-13 2021-13 (ML21313A145). (ML21313A145).

Applicants may Applicants may potentially find this potentially find this document useful document useful when addressing when addressing FFRD in LOCA FFRD in LOCA evaluation evaluation methodologies. methodologies.

13

235 Guidance Burnup to Burnup to U Enrichment Chromium-coated Doped UO2 Fuel

  1. Document beyond 5.0 wt% Zirconium Cladding Pellets Regulation 68 GWd/MTU 75 GWd/MTU 10 CFR 51.21 10 CFR 51.21 is fully applicable Environmental 10 CFR 51.22 lists the NRCs CATEXs. CATEXs are for categories of actions that the Commission has found do not Assessment (EA) individually or cumulatively have a significant effect on the human environment.

and 51.22 It is premature to decide now to apply a CATEX for nuclear power plant LARs due to the range of different ATF Categorical technologies and our uncertainty about what the licensees will submit. For example, the staff is expecting changes 12 Exclusion (CATEX) - to the source term to be applied in various safety analyzes (e.g., RG 1.183 calculations) with results that cannot yet NMSS be determined. Given this situation, the NRC staff is currently considering a path forward on the environmental reviews of ATF licensing actions.

Note: Due to plant changes and unanalyzed environmental impacts (i.e., effluent releases, accidents, and transportation of fuel and waste) as a result of adopting fuels with increased enrichment and higher burnup levels, it is expected that the NRC staff will perform an EA in the first LAR application for this ATF type.

10 CFR 51.51, Fully applicable Uranium fuel cycle Several aspects of the uranium fuel cycle are expected to remain unchanged from current processes (e.g., uranium environmental data recovery and conversion).

- Table S NMSS Note: Fuel cycle facility changes necessary for use of ATF may require NRC approval. For example, fuel fabricators will have to determine whether they can manufacture the fuel assemblies under their existing licenses or whether 13 they will require NRC authorization in the form of LARs. At the time of an ATF LAR from a nuclear power plant licensee, these associated fuel cycle impacts will be evaluated and, where appropriate, analysis from prior environmental reviews may be incorporated by reference into the LAR NEPA review. NEPA analyses may also tier off previous analyses.

Priority: High; near-term 14

235 Guidance Burnup to Burnup to U Enrichment Chromium-coated Doped UO2 Fuel

  1. Document beyond 5.0 wt% Zirconium Cladding Pellets Regulation 68 GWd/MTU 75 GWd/MTU 10 CFR 51.52, Not fully applicable Environmental Note: The proposed enrichment and burnup levels are beyond the conditions specified in 10 CFR 51.52(a) and effects of analyzed in the License Renewal GEIS (NUREG-1437 Revision 1). Further, chromium-coated cladding falls outside transportation of fuel of the conditions described in 10 CFR 51.52(a)(2) because 10 CFR 51.52(a)(2) only speaks to zircaloy-clad fuel.

and waste - Table The staff would need to assess the impacts with regard to enrichment, burnup, and cladding by conducting a full S NMSS description and detailed analysis of the environmental effects of transportation of fuel and waste to and from the reactor, including values for the conditions of transport and for the environmental risks from accidents in transport 14 (see 10 CFR 51.52(b)).

Priority: High; near-term Note: NUREG/CR-6703 (ML010310298) did attempt to analyze BU levels greater than 62 GWd/MTU but found there was too much uncertainty in changes in the gap-release fraction associated with increasing fuel BU. NUREG/CR-6703recommends that the staff re-evaluate this as the methods for assessing fission gas releases are validated with data for higher BUs (see page 52 of NUREG/CR-6703). The NRC staff are performing an analysis of transportation impacts based on the aspects of NUREG/CR-6703 and other transportation assessments for higher BU levels.

10 CFR 70.24 Fully applicable Fully applicable Fully applicable Fully applicable Fully applicable 15 Criticality Accident No data gaps No data gaps No data gaps No data gaps No data gaps Requirements NUREG-0630 Not fully applicable Not fully applicable Fully applicable Not fully applicable Fully applicable Cladding Swelling Reason: NUREG- Reason: NUREG- No data gaps Reason: Cladding No data gaps and Rupture Models 0630 models are 0630 models are swelling and burst for LOCA Analysis hot-rod models and hot-rod models and data presented is (ML053490337) thus do not consider thus do not consider from bare zircaloy interactions interactions cladding, so should between rods. between rods. not be used if the Interactions Interactions benefits of coated 16 between rods affect between rods affect cladding are to be swelling and rupture swelling and rupture credited.

behavior, which may behavior, which may Closure: As stated impact the amount impact the amount in coated cladding of fragmented fuel of fragmented fuel interim staff that may disperse, that may disperse, guidance and should, thus, and, should, thus, (ML19343A121), if not be neglected. not be neglected. NUREG-0630 is used, it would be 15

235 Guidance Burnup to Burnup to U Enrichment Chromium-coated Doped UO2 Fuel

  1. Document beyond 5.0 wt% Zirconium Cladding Pellets Regulation 68 GWd/MTU 75 GWd/MTU Closure: Interactions Closure: Interactions useful for licensees between rods should between rods should to show that data be considered for be considered for bounds the swelling and rupture swelling and rupture performance of the modelling. modelling. coated cladding, or Reason: HBU rod Reason: HBU rod if new burst stress internal pressures internal pressures and ballooning may exceed the rod may exceed the rod strain limits are internal pressures of internal pressures of proposed, a the data provided in the data provided in significant body of NUREG-0630. NUREG-0630. data would be Closure: If the Closure: If the useful to NUREG-0630 data is NUREG-0630 data is demonstrate that desired to be used, desired to be used, the degree of licensees should licensees should swelling will not be show that HBU rod show that HBU rod underestimated.

internal pressures internal pressures Framework/approa are bounded by the are bounded by the ch described for data provided in data provided in modeling swelling NUREG-0630. NUREG-0630. and rupture remains fully applicable.

16

235 Guidance Burnup to Burnup to U Enrichment Chromium-coated Doped UO2 Fuel

  1. Document beyond 5.0 wt% Zirconium Cladding Pellets Regulation 68 GWd/MTU 75 GWd/MTU NUREG-0800 SRP Not fully applicable Not fully applicable Not fully applicable Not fully applicable Not fully applicable Chapter 4.2 Fuel Reason: Interim RIA Reason: Interim RIA Reason: Interim RIA Note: Coated Reason: Interim RIA System Design guidance provided in guidance provided in guidance in Appendix cladding interim staff guidance in (ML070740002) Appendix B does not Appendix B does not B does not match the guidance Appendix B does match the most recent match the most recent current RIA guidance (ML19343A121) not match the guidance given in RG guidance given in RG in RG 1.236. created to current RIA 1.236. 1.236. RG 1.236 is also not supplement SRP guidance in Closure: Appendix B Closure: Appendix B applicable to fuel Section 4.2 in coated RG 1.236.

should be updated, should be updated, enriched to greater cladding reviews. RG 1.236 is also not and readers should be and readers should be than 5.0 wt%. Reason: Interim RIA applicable to doped directed to RG 1.236. directed to RG 1.236. Closure: See guidance in Appendix fuel.

Priority: Low (this is Note that RG 1.236 is discussion on B does not match the Closure: See administrative in not fully applicable to RG 1.236 current RIA guidance discussion on nature as RG 1.236 75 GWd/MTU. Note: Increased in RG 1.236. Note RG 1.236 has been published to Priority: Low; long- enrichment could that RG 1.236 is also Reason: Impact of address RIA guidance term potentially lead to not applicable to additives on fuel up to 68 GWd/MTU); Reason: FFRD not higher rod worth and coated cladding. performance has long-term thoroughly addressed. peaking factors. Closure: See not been extensively 17 Reason: FFRD not Closure: Potential Sections 2.1.4 and discussion on quantified.

thoroughly addressed. addition of vendor 2.2.1.3 of RG 1.236 RG 1.236 and coated Closure: Data on Closure: Potential requirements for state that the effect cladding interim staff irradiated, doped addition of vendor submittals if rod burst of rod worth and guidance UO2 fuel pellets and requirements for is assumed to occur. power peaking limits (ML19343A121). integral fuel submittals where rod Priority: TBD should be considered burnable absorber burst is assumed to in RIA analyses. fuel pellets may be occur. helpful to better Priority: TBD understand impact of additive agents (e.g., larger grain size, retained fission gas, grain boundary hold-up, thermal conductivity) on cladding failure thresholds, FFRD, transient FGR, and coolable geometry.

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235 Guidance Burnup to Burnup to U Enrichment Chromium-coated Doped UO2 Fuel

  1. Document beyond 5.0 wt% Zirconium Cladding Pellets Regulation 68 GWd/MTU 75 GWd/MTU NUREG-1465 Accident Source Terms for Light Potential impacts to accident source term described above for RG 1.183 Revision 1.

18 Water Reactor Nuclear Power Plants (ML041040063)

NUREG-2121 FFRD Not fully applicable Not fully applicable Not fully applicable Not fully applicable Not fully applicable During the LOCA Reason: Published in Reason: Published in Note: The effect of Reason: Only Reason: Only (ML12090A018) 2012, so does not 2012, so does not enrichment on uncoated cladding traditional UO2 fuel include recent FFRD include recent FFRD FFRD phenomena considered in tests considered in the research findings research findings was not a part of described in the tests described in Closure: Recent Closure: Recent NUREG-2121 NUREG. the NUREG.

FFRD research FFRD research Note: INL Power Closure: Impact of additives findings are covered findings are covered Burst Facility tests Justification for the on fuel in RIL 2021-13 in RIL 2021-13 included fuel application of the performance has (ML21313A145) (ML21313A145) enriched to 9.6 wt%. NUREG-2121 data not been Note: Halden tests Note: Halden tests to coated cladding extensively described in the described in the may be necessary quantified.

NUREG include NUREG include Closure: Data for several tests at > several tests at > irradiated, doped 19 75 GWd/MTU 75 GWd/MTU UO2 fuel pellets Note: Studsvik tests Note: Studsvik tests and integral fuel described in the described in the burnable absorber NUREG include NUREG include fuel pellets may be several tests at > several tests at > helpful to better 70 GWd/MTU 70 GWd/MTU understand impact Note: More data may Note: More data may of additive agents be helpful to properly be helpful to properly (e.g., larger grain address FFRD if the address FFRD if size, retained burst is predicted to burst is predicted to fission gas, grain occur. If burst and, occur. If burst and, boundary hold-up, thus, FFRD is thus, FFRD is thermal expected to occur, expected to occur, conductivity) on technical justification technical justification cladding failure for the threshold for the threshold thresholds, FFRD, (e.g., BU) for which (e.g., BU) for which 18

235 Guidance Burnup to Burnup to U Enrichment Chromium-coated Doped UO2 Fuel

  1. Document beyond 5.0 wt% Zirconium Cladding Pellets Regulation 68 GWd/MTU 75 GWd/MTU FFRD is to be FFRD is to be transient FGR, and considered may be considered may be coolable geometry.

helpful, as well as a helpful, as well as a technical justification technical justification for when the effect of for when the effect of fragmentation- fragmentation-induced FGR is to be induced FGR is to be considered. considered.

Additionally, Additionally, examining the impact examining the impact of fuel of fuel fragment/particle fragment/particle transport and transport and deposition on deposition on coolability and coolability and criticality, including criticality, including addressing potential addressing potential sump blockage sump blockage caused by fuel caused by fuel fragments/particles in fragments/particles in the coolant may be the coolant may be helpful to better helpful to better understand the understand the effects of FFRD. effects of FFRD.

The NRCs The NRCs understanding of understanding of recent FFRD recent FFRD research is research is documented in documented in RIL 2021-13 RIL 2021-13 (ML21313A145). (ML21313A145).

Applicants may Applicants may potentially find this potentially find this document useful document useful when addressing when addressing FFRD in LOCA FFRD in LOCA evaluation evaluation methodologies. methodologies.

19

235 Guidance Burnup to Burnup to U Enrichment Chromium-coated Doped UO2 Fuel

  1. Document beyond 5.0 wt% Zirconium Cladding Pellets Regulation 68 GWd/MTU 75 GWd/MTU NUREG/CR-7219 Fully applicable Fully applicable Fully applicable Not fully applicable Not fully Cladding Behavior No data gaps Note: Section 3.3.2 No data gaps Reason: Data only Applicable During Postulated details current post included bare Reason: BU LOCA quench ductility zirconium. Rate of threshold for the (ML16211A004) results for only up to oxidation and formation of fuel-70 GWd/MTU embrittlement clad bond layer expected to be has not been well different quantified in most Closure: TBD doped fuel.

Note: Zircaloy Closure: Hot cell embrittlement post irradiation mechanisms examination may presented in be helpful to NUREG/CR-7219 define threshold may remain for fuel-clad bond applicable due to layer 20 presence of base zircaloy cladding.

Note: Single sided steam oxidation data and subsequent mechanical data as well as double sided integral steam oxidation data and subsequent mechanical data may be helpful to establish post quench ductility limits 20

235 Guidance Burnup to Burnup to U Enrichment Chromium-coated Doped UO2 Fuel

  1. Document beyond 5.0 wt% Zirconium Cladding Pellets Regulation 68 GWd/MTU 75 GWd/MTU RG 1.157 Best- Not fully applicable Not fully applicable Fully applicable Not fully applicable Not fully Estimate Reason: RG 1.157 Reason: RG 1.157 No data gaps Reason: Cathcart- applicable Calculations of is not fully is not fully Pawel correlation Reason:

ECCS Performance applicable to the applicable to the and associated Section 3.2.1 on (ML003739584) current BU limit of current BU limit of data is referenced initial stored 62 GWd/MTU 62 GWd/MTU as acceptable for energy in the fuel because it does not because it does not calculating the is out of date. It address recent address recent rates of energy also references an updates to physical updates to physical release, hydrogen acceptable initial phenomena. For phenomena. For generation, and stored energy example, thermal example, thermal cladding oxidation, model. This conductivity conductivity but was developed model was degradation (TCD) degradation (TCD) for bare zircaloy developed for UO2 is not addressed. is not addressed. cladding. Use of and is not TCD occurs under TCD occurs under the Cathcart-Pawel acceptable HBU conditions. HBU conditions. correlation would currently for More information on More information on not realistically doped fuel.

21 TCD is available in TCD is available in model oxidation Closure:

Information Information kinetics. Licensees should Notice (IN) 2009-23 Notice (IN) 2009-23 Chromium-coated show that the (ML091550527 and (ML091550527 and cladding is stored energy ML121730336). ML121730336). expected to have does not change Closure: The staff Closure: The staff better oxidation much from a has been aware of has been aware of performance than vendors current issues such as TCD issues such as TCD bare zirconium UO2 models, or for some time and for some time and cladding. new models plans to update plans to update Closure: An should be RG 1.157 in the RG 1.157 in the oxidation kinetics proposed.

medium term. medium term. model based on Priority: Medium; Priority: Medium; chromium-coated medium term medium term cladding should be Reason: FFRD is Reason: FFRD is developed. If the not addressed not addressed licensee is not Closure: FFRD Closure: FFRD crediting the should be should be benefits of the addressed in LOCA addressed in LOCA coating and the 21

235 Guidance Burnup to Burnup to U Enrichment Chromium-coated Doped UO2 Fuel

  1. Document beyond 5.0 wt% Zirconium Cladding Pellets Regulation 68 GWd/MTU 75 GWd/MTU evaluation evaluation Cathcart-Pawel methodologies. If methodologies. If correlation is used, burst and thus burst and thus it should be FFRD is expected to FFRD is expected to demonstrated that it occur, technical occur, technical bounds the coated justification for the justification for the cladding oxidation threshold (e.g., BU) threshold (e.g., BU) kinetics.

for which FFRD is to for which FFRD is to Note: this RG be considered may be considered may provides a means be helpful, as well be helpful, as well of meeting the as a technical as a technical 50.46 prescriptive justification for when justification for when analytical the effect of the effect of requirements; fragmentation- fragmentation- those requirements induced FGR is to induced FGR is to are not applicable be considered. The be considered. The for fuel rods with limiting condition for limiting condition for coated cladding rupture with rupture with due to the wording fragmentation fragmentation of 50.46(a)(1)(i), so should be analyzed should be analyzed this RG is fully as well. as well. applicable pending Additionally, Additionally, an approved examining the examining the exemption to impact of fuel impact of fuel 50.46.

fragment/particle fragment/particle transport and transport and deposition on deposition on coolability and coolability and criticality, including criticality, including addressing potential addressing potential sump blockage sump blockage caused by fuel caused by fuel fragments/particles fragments/particles in the coolant may in the coolant may be helpful to better be helpful to better 22

235 Guidance Burnup to Burnup to U Enrichment Chromium-coated Doped UO2 Fuel

  1. Document beyond 5.0 wt% Zirconium Cladding Pellets Regulation 68 GWd/MTU 75 GWd/MTU understand the understand the effects of FFRD. effects of FFRD.

Note: The NRCs Note: The NRCs understanding of understanding of recent FFRD recent FFRD research is research is documented in documented in RIL 2021-13 RIL 2021-13 (ML21313A145). (ML21313A145).

Applicants may Applicants may potentially find this potentially find this document useful document useful when addressing when addressing FFRD in LOCA FFRD in LOCA evaluation evaluation methodologies. methodologies.

Reason: The limiting Reason: The limiting rod may not be the rod may not be the hot rod when hot rod when considering swelling considering swelling and rupture (see and rupture (see NUREG-0630 NUREG-0630 discussion) discussion)

Closure: Rod-to-rod Closure: Rod-to-rod interactions should interactions should be considered for be considered for swelling and rupture swelling and rupture in LOCA analyses. in LOCA analyses.

23

235 Guidance Burnup to Burnup to U Enrichment Chromium-coated Doped UO2 Fuel

  1. Document beyond 5.0 wt% Zirconium Cladding Pellets Regulation 68 GWd/MTU 75 GWd/MTU RG 1.203 Transient Fully applicable Fully applicable Fully applicable Fully applicable Fully applicable and Accident Note: Vendors may Note: Vendors may Note: Vendors may Note: RG 1.203 Note: Vendors Analysis Methods need to validate need to validate need to validate discusses 50.46 may need to (ML053500170) their evaluation their evaluation their evaluation requirements, so update and models to higher models to higher models to higher this RG is only fully validate their BU. BU. enrichments applicable pending evaluation models an accepted to consider doped exemption to fuel 50.46. See 22 discussion on 50.46 for more details.

Note: Vendors will likely need to update and validate their evaluation models to consider coated cladding 24

235 Guidance Burnup to Burnup to U Enrichment Chromium-coated Doped UO2 Fuel

  1. Document beyond 5.0 wt% Zirconium Cladding Pellets Regulation 68 GWd/MTU 75 GWd/MTU RG 1.240 Fresh and Not fully Applicable Not fully applicable Not fully applicable Fully applicable Not fully applicable Spent Fuel Pool Reason: Cites use of Reason: Cites use of Reason: Mentions No data gaps Reason: Mentions Criticality Analysis gap release fractions gap release fractions gap release gap release (ML20182A788) from RG 1.183 and from RG 1.183 and fractions from fractions from PNNL-18212 Rev 1. PNNL-18212 Rev 1. RG 1.183 Rev. 0, RG 1.183 Rev. 0, RG 1.183 Rev 0 is RG 1.183 Rev 0 is which is not fully which is not fully only applicable up to only applicable up to applicable. applicable.

NEI 12-16, Rev. 4 62 GWd/MTU and 62 GWd/MTU and RG 1.183, Rev. 1 RG 1.183, Rev. 1 (ML18269E069)

PNNL-18212 Rev 1 PNNL-18212 Rev 1 will not be fully will not be fully is only applicable up is only applicable up applicable, but the applicable, but the to 65 GWd/MTU. to 65 GWd/MTU. analytical procedure analytical Closure: Will be fully Closure: Will be fully remains applicable. procedure remains applicable upon the applicable upon the Closure RG 1.183 applicable.

publication of publication of Rev 1 will provide Closure: RG 1.183 RG 1.183 Rev 1, RG 1.183 Rev 1, an analytical Rev 1, will provide which will provide which will provide an procedure for an analytical tables for gap analytical procedure calculating gap procedure for release fractions for calculating gap release fractions calculating gap 23 release fractions that that is applicable. release fractions is applicable. Note: Criticality that is applicable.

code validation will Note: Section 9.3 ideally demonstrate of NEI 12-16, that validation is Rev. 4 describes applicable to the how to approach increased new fuel designs.

enrichment range Note: If dopant (Section 7.1.4.1 of increases density, Version 1.2 of the higher density fuel ATF Project Plan may lead to more (ML21243A298 235U in the spent discusses various fuel pool ways of Note: Criticality benchmarking codes may need to criticality analyses be validated for that could be used doped fuel. Per to validate criticality Section 7.1.4.1 of codes)) version 1.2 of the ATF Project Plan 25

235 Guidance Burnup to Burnup to U Enrichment Chromium-coated Doped UO2 Fuel

  1. Document beyond 5.0 wt% Zirconium Cladding Pellets Regulation 68 GWd/MTU 75 GWd/MTU Note: Criticality (ML21243A298),

analyses may need discusses various to be updated to ways of show adherence to benchmarking the k-effective criticality analyses.

regulatory limits. These methods may be used for validating codes.

Note: RG 1.240 Section C paragraph o states that for new fuel designs, justification for continued use of the assumptions presented in NEI 12-16 Rev. 4 may be necessary.

26

235 Guidance Burnup to Burnup to U Enrichment Chromium-coated Doped UO2 Fuel

  1. Document beyond 5.0 wt% Zirconium Cladding Pellets Regulation 68 GWd/MTU 75 GWd/MTU NUREG-0800 SRP Fully applicable Fully applicable Fully applicable Fully applicable Fully applicable Chapter 9.1.1 No data gaps No data gaps Note: Compliance No data gaps Note: Criticality Criticality Safety of with 10 CFR 50.68 codes may need Fresh and Spent is a part of the to be validated for Fuel Storage and stated review doped fuel.

Handling procedures. Section 7.1.4.1 of (ML070570006) Note: Criticality version 1.2 of the code validation will ATF Project Plan ideally demonstrate (ML21243A298),

that validation is discusses various applicable to the ways of increased benchmarking enrichment range criticality (Section 7.1.4.1 of analyses. These version 1.2 of the methods may be 24 ATF Project Plan used for validating (ML21243A298) codes.

discusses various ways of benchmarking criticality analyses that could be used to validate criticality codes)

Note: Criticality analyses may need to be updated to show adherence to the k-effective regulatory limits.

27

235 Guidance Burnup to Burnup to U Enrichment Chromium-coated Doped UO2 Fuel

  1. Document beyond 5.0 wt% Zirconium Cladding Pellets Regulation 68 GWd/MTU 75 GWd/MTU NUREG-0800 SRP Fully applicable Fully applicable Fully applicable Fully applicable Fully applicable Chapter 9.1.2 New No data gaps No data gaps Note: Compliance No data gaps No data gaps and Spent Fuel with 10 CFR 50.68 25 Storage is a part of the (ML070550057) stated review procedures.

NUREG-1520 SRP Not applicable Not applicable Fully applicable Fully applicable Fully applicable for Fuel Cycle Reason: HBU is not Reason: HBU is not No data gaps No data gaps No data gaps Facilities License relevant to uranium relevant to uranium Applications conversion, conversion, 26 (ML15176A258) - enrichment, fuel enrichment, fuel NMSS fabrication, or fabrication or greater-than-critical greater-than-critical mass facilities. mass facilities.

Closure: No closure Closure: No closure necessary necessary NUREG-1065 Not applicable Not applicable Fully applicable Fully applicable Fully applicable Acceptable Reason: HBU is not Reason: HBU is not No data gaps No data gaps No data gaps Standard Format relevant to fuel relevant to fuel and Content for the fabrication. fabrication.

Fundamental Closure: No closure Closure: No closure Nuclear Material necessary necessary.

27 Control (FNMC)

Plan Required for Low-Enriched Uranium Facilities (ML031340288) -

NMSS 28

235 Guidance Burnup to Burnup to U Enrichment Chromium-coated Doped UO2 Fuel

  1. Document beyond 5.0 wt% Zirconium Cladding Pellets Regulation 68 GWd/MTU 75 GWd/MTU NUREG/CR-5734 Not applicable Not applicable Fully applicable Fully applicable Fully applicable Recommendations Reason: HBU is not Reason: HBU is not No data gaps No data gaps No data gaps to the NRC on relevant to fuel relevant to fuel Acceptable enrichment. fabrication.

Standard Format Closure: No closure Closure: No closure and Content for the necessary. necessary.

Fundamental Nuclear Material 28 Control (FNMC)

Plan Required for Low-Enriched Uranium Enrichment Facilities (ML15120A354) -

NMSS 29

235 Guidance Burnup to Burnup to U Enrichment Chromium-coated Doped UO2 Fuel

  1. Document beyond 5.0 wt% Zirconium Cladding Pellets Regulation 68 GWd/MTU 75 GWd/MTU NUREG-2214, Not fully applicable Not fully applicable Not fully applicable Not fully Managing Aging Reason: The evaluations of aging Reason: Increased Reason: The applicable Processes in mechanisms for spent fuel cladding need to use of burnable evaluations of Reason: Doped Storage (MAPS) be extended to burnups greater than absorbers may aging mechanisms fuel pellets may Report 62 GWd/MTU. This higher BU may influence affect cladding for spent fuel affect cladding (ML19214A111) - which aging mechanisms are credible during hoop stresses and cladding do not hoop stresses (via NMSS extended storage and may warrant unique the associated consider the pellet-clad recommended preventive actions (e.g., fuel aging mechanisms. potential effects of interactions or drying criteria) and other aging management Closure: Fuel Cr coating. fission gas approaches. performance Closure: release) and the Closure: Fuel performance modeling and modeling and Characterization of associated aging 29 characterization of irradiated cladding with characterization of irradiated Cr- mechanisms.

higher BU (e.g., mechanical testing, irradiated cladding coated cladding Closure: Fuel microstructure characterization) may be with increased (e.g., mechanical performance needed to assess credible aging enrichment (e.g., testing, modeling and mechanisms. mechanical testing) microstructure characterization of may be needed to analysis) may be irradiated cladding assess credible needed to assess with doped pellets aging mechanisms. credible aging (e.g., mechanical mechanisms, such testing) may be as hydrogen needed to assess effects, thermal credible aging creep, and mechanisms.

corrosion.

NUREG-2215, SRP Not fully applicable Not fully applicable Under review Under review for Spent Fuel Dry Reason: Guidance provided is limited to BU Reason: Guidance Note: Guidance Note: Staff is Storage Systems up to 60 GWd/MTU. is limited to provides evaluating the and Facilities Closure: TBD enrichments up to information on Zr need to address (ML20321A086) - Note: Shielding discussions in submissions 5wt%. alloy cladding. No potential validation 30 NMSS may need to consider HBUs and fuel Closure: TBD discussion of variations and fuel composition to account for increase source Note: Shielding unique dopant effect on term. Literature reviews and research will discussion in considerations for fuel density.

provide information on this technical issue. submissions may Cr coating on Note: Guidance Note: Criticality discussion in submissions need to consider cladding does not address may need to consider higher BUs for BU higher enrichments performance. Staff potential unique credit analyses, as well as benchmark the to account for will assess this considerations of 30

235 Guidance Burnup to Burnup to U Enrichment Chromium-coated Doped UO2 Fuel

  1. Document beyond 5.0 wt% Zirconium Cladding Pellets Regulation 68 GWd/MTU 75 GWd/MTU criticality analysis and address bounding increase burnable impact when lead fuel dopants on profiles for HBU fuels. Literature reviews and absorber use and test assembly data cladding hoop research will provide information on this impact on source becomes available. stresses. Staff will technical issue. term. Literature Applicants could assess this impact Note: Materials evaluation in submissions reviews and also provide this when lead test may need to consider higher BUs effect on research will information. assembly data cladding performance. Staff will assess this provide information becomes impact when lead test assembly data on this technical available.

becomes available. Applicants could also issue. Applicants could provide this information. Note: Criticality also provide this discussion in information.

submissions may need to consider higher enrichment as well as benchmark the criticality analysis and address bounding profiles for higher enrichment fuels.

Literature reviews and research will provide information on this technical issue.

Note: Materials discussion in submissions may need to consider if an increase in burnable absorber use which may affect cladding hoop stress and, consequently, the 31

235 Guidance Burnup to Burnup to U Enrichment Chromium-coated Doped UO2 Fuel

  1. Document beyond 5.0 wt% Zirconium Cladding Pellets Regulation 68 GWd/MTU 75 GWd/MTU recommended fuel drying criteria to support adequate cladding performance.

Literature reviews and research will provide information on this technical issue.

NUREG-2216, SRP Not fully applicable Not fully applicable Under review Under review for Transportation Reason: Guidance provided is limited to Reason: Guidance Note: Guidance Note: Staff is Packages for Spent burnups up 60 GWd/MTU. is limited to provides evaluating the Fuel and Closure: TBD enrichments up to information on Zr- need to address Radioactive Material Note: Shielding discussion in submissions 5 wt%. alloy cladding. No potential validation (ML20234A651) - may need to consider HBUs and fuel Closure: TBD discussion of variations and fuel NMSS composition to account for increase source Note: Shielding unique dopant effect on term. Literature reviews and research will discussion in considerations for fuel density.

provide information on this technical issue. submissions may Cr coated on Note: Guidance Note: Criticality discussion in submissions need to consider cladding does not address may need to consider HBUs for BU credit higher enrichments performance. Staff potential unique analyses, as well as benchmark the criticality to account for will assess this considerations of 31 impact when lead analysis and address bounding profiles for increase burnable fuel dopants on HBU fuels. Literature reviews and research absorber use and test assembly data cladding hoop will provide information on this technical impact on source becomes available. stresses. Staff will issue. term. Literature Applicants could assess this impact Note: Materials evaluation in submissions reviews and also provide this when lead test may need to consider HBUs effect on research will information. assembly data cladding performance. Staff will assess this provide information becomes impact when lead test assembly data on this technical available.

becomes available. Applicants could also issue. Applicants could provide this information. Note: Criticality also provide this discussion in information.

submissions may need to consider 32

235 Guidance Burnup to Burnup to U Enrichment Chromium-coated Doped UO2 Fuel

  1. Document beyond 5.0 wt% Zirconium Cladding Pellets Regulation 68 GWd/MTU 75 GWd/MTU higher enrichments as well as benchmark criticality analysis, address additional isotopic depletion, and address bounding profiles.

Literature reviews and research will provide information on this technical issue.

Note: Materials discussion in submissions may need to consider if an increase in burnable absorber use which may affect cladding hoop stress and, consequently, the recommended fuel drying criteria.

Literature reviews and research will provide information on this technical issue.

33

235 Guidance Burnup to Burnup to U Enrichment Chromium-coated Doped UO2 Fuel

  1. Document beyond 5.0 wt% Zirconium Cladding Pellets Regulation 68 GWd/MTU 75 GWd/MTU NUREG-2224, Dry Not fully applicable Not fully applicable Not fully applicable Not fully Storage and Reason: The evaluations of fuel cladding Reason: Increased Reason: The applicable Transportation of performance and recommended licensing use of burnable evaluations of fuel Reason: Doped High Burnup Spent approaches need to be extended to higher absorbers may cladding fuel pellets may Nuclear Fuel BU (greater than 62 GWd/MTU). BU above affect cladding performance do not affect cladding (ML20191A321) - 62 GWd/MTU may influence cladding internal hoop stresses and consider the hoop stresses (via NMSS pressure, mechanical properties, and the the associated potential effects of pellet-clad credible aging mechanisms during extended cladding behavior. Cr coating (e.g., interactions or storage. The increased BU may also warrant Closure: Fuel cladding oxidation, fission gas revised recommended fuel drying practices to performance hydrogen pickup). release) and the maximize cladding performance. modeling and Revised fuel drying associated Closure: Fuel performance modeling and characterization of criteria to consider cladding characterization of irradiated cladding with irradiated cladding effects of reduced performance HBU (e.g., mechanical testing, microstructure with increased hydrogen pickup in Closure: Fuel 32 characterization) may be needed to enrichment (e.g., the reactor may be performance demonstrate adequate cladding performance. mechanical testing) warranted. modeling and may be needed to Closure: characterization of demonstrate Characterization of irradiated cladding adequate cladding irradiated Cr- with doped pellets performance. coated cladding (e.g., mechanical (e.g., mechanical testing) may be testing, needed to microstructure demonstrate analysis) may be adequate cladding needed to performance.

demonstrate adequate cladding performance.

34

235 Guidance Burnup to Burnup to U Enrichment Chromium-coated Doped UO2 Fuel

  1. Document beyond 5.0 wt% Zirconium Cladding Pellets Regulation 68 GWd/MTU 75 GWd/MTU RG 3.48 Standard Fully applicable Fully applicable Fully applicable Fully applicable Fully applicable Format and Content No data gaps No data gaps No data gaps No data gaps No data gaps for the Safety Analysis Report for an Independent Spent Fuel Storage 33 Installation or Monitored Retrievable Storage Installation (Dry Storage)

(ML19141A092) -

NMSS RG 7.9 Standard Fully applicable Fully applicable Fully applicable Fully applicable Fully applicable Format and Content No data gaps No data gaps No data gaps No data gaps No data gaps of Part 71 Applications for 34 Approval of Packages for Radioactive Material (ML050530321) -

NMSS 35

235 Guidance Burnup to Burnup to U Enrichment Chromium-coated Doped UO2 Fuel

  1. Document beyond 5.0 wt% Zirconium Cladding Pellets Regulation 68 GWd/MTU 75 GWd/MTU RG 3.71 Nuclear Not applicable Not applicable Fully applicable Fully applicable Fully applicable Criticality Safety Reason: HBU is not Reason: HBU is not No data gaps No data gaps No data gaps Standards for relevant to fuel relevant to fuel Nuclear Materials enrichment or enrichment or Outside Reactor fabrication. RG fabrication.

Cores 3.71 endorses ANS Closure: No closure (ML18169A258) - Standard 8.27 for necessary NMSS use of burnup credit in storage and transportation 35 criticality. The ANS standard does not limit enrichment or burnup. NRC action would be to review, and if appropriate, endorse a new standard.

Closure: No closure necessary RG 3.67 Standard Not applicable Not applicable Fully applicable Fully applicable Fully applicable Format and Content Reason: This RG is Reason: This RG No data gaps No data gaps No data gaps for Emergency specific to format is specific to format Plans for Fuel Cycle and content of and content of and Materials emergency plans emergency plans Facilities for fuel cycle and for fuel cycle and 36 (ML103360487) material facilities material facilities and does not and does not reference specific reference specific burnup criteria. burnup criteria.

Closure: No closure Closure: No closure necessary necessary 36

235 Guidance Burnup to Burnup to U Enrichment Chromium-coated Doped UO2 Fuel

  1. Document beyond 5.0 wt% Zirconium Cladding Pellets Regulation 68 GWd/MTU 75 GWd/MTU NUREG-0800 SRP Fully Applicable Fully applicable Fully applicable Fully applicable Fully applicable Chapter 4.3 Nuclear No data gaps No data gaps No data gaps No data gaps No data gaps 37 Design (ML070740003) 37
3. Licensing Pathway Diagram As discussed in Section 1, the NRC staff has developed the below licensing pathway diagram to serve as a companion to the information presented in the RFAA table in Section 2. Based on its current understanding of vendor and licensee plans, the NRC staff has chosen to limit the scope of the diagram to the licensing of HBU and increased enrichment fuels. Should circumstances change such that additional diagrams may be beneficial, the NRC staff will evaluate the potential benefit and develop additional diagrams, as necessary.

The licensing pathway diagram is intended to show a potential plan or path forward, given the current state of technical and regulatory progress for the given fuel concept. This diagram does not identify all of the issues or requirements that may need to be addressed as a part of the review of a given TR or LAR for in-reactor use. The NRC staff encourages vendors and licensees to engage with the staff early in the process of developing a TR or LAR to help support the early identification and resolution of any technical and policy issues associated with a given approach.

Following the same color scheme from the RFAA table, green colored boxes in the diagrams are items to be addressed by NRC staff and blue colored boxes are items that may need to be addressed by a fuel vendor or a licensee. This is also illustrated by items above the horizontal line (NRC actions) and below the horizontal line (potential fuel vendor or licensee information needs).

The dashed border around the Advisory Committee on Reactor Safeguards (ACRS) Review box on the plant-specific LAR review pathway indicates the possibility of an ACRS review. Should the Commission refer a plant-specific LAR to the ACRS for review, the NRC staff will endeavor to minimize the impact on the LAR review schedule by engaging with the ACRS early in the review.

38

3.1: Higher Burnup and Increased Enrichment Licensing Pathways Figure 3.1-1 Potential Pathway for Licensing Higher Burnup and Increased Enrichment Fuels for In-Reactor Use 39

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