ML21314A531

Response to Nuclear Energy Institute Comments on Draft Version 1.2 of the Accident Tolerant Fuel Project Plan

ML21314A531
Person / Time
Issue date:	11/19/2021
From:	Joseph Donoghue NRC/NRR/DSS
To:	Ashkeboussi N Nuclear Energy Institute
Wentzel M
References
Download: ML21314A531 (30)

Text

November 19, 2021 Mr. Nima Ashkeboussi Senior Director, Fuel Cycle and Radiation Safety Programs Nuclear Energy Institute 1201 F Street NW, Ste. 1100 Washington, DC 20004

SUBJECT:

RESPONSE TO NUCLEAR ENERGY INSTITUTES COMMENTS ON DRAFT VERSION 1.2 OF THE ACCIDENT TOLERANT FUEL PROJECT PLAN

Dear Mr. Ashkeboussi:

By letter dated August 5, 2021 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML21221A130), the Nuclear Energy Institute provided comments on draft Version 1.2 of the Project Plan to Prepare the U.S. Nuclear Regulatory Commission [NRC] for Efficient and Effective Licensing of Accident Tolerant Fuels (ATF Project Plan). The comments provided in your letter were in addition to or to expand upon the industry comments provided during the July 22, 2021 public meeting to discuss draft Version 1.2 of the ATF Project Plan (ADAMS Accession No. ML21208A152).

Enclosed are the NRC staffs responses to the comments received during the July 22, 2021 public meeting, as well as to those comments included in the August 5, 2021 letter. The comment responses provide a discussion of how the NRC staff considered each comment prior to issuing the final Version 1.2 of the ATF Project Plan (ADAMS Accession No. ML21243A298).

As described within the ATF Project Plan, the NRC staff considers stakeholder engagement one of the key components in preparing to license the ATF-concept, higher burnup, and increased enrichment fuels. As such, the NRC staff appreciates the participation of and feedback from the Nuclear Energy Institute and other industry representatives during the update to the ATF Project Plan. The NRC staff will continue to look for opportunities to engage all stakeholders as the agency continues to prepare for the licensing of these fuels.

Sincerely,

/RA/

Joseph E. Donoghue, Director Division of Safety Systems Office of Nuclear Reactor Regulation

Enclosure:

As stated cc: Listserv

Enclosure Responses to Industry Comments on Draft Version 1.2 of the Accident Tolerant Fuel Project Plan General Comments

1. NRC Should Thoroughly Review and Incorporate Industry Comments into this Revision As indicated by the responses to detailed comments that follow, the NRC staff has fully considered the industrys comments and has made updates throughout the ATF Project Plan, as appropriate.

2. NRC Should Prioritize Efforts to Generically Evaluate Environmental Impacts As discussed in the detailed comment responses, the NRC staff is developing a plan to perform a bounding analysis of the environmental impacts associated with the deployment of ATF technologies, the details of which will be made available to the public, once finalized.

3. The Project Plan Should be More Responsive to the Use of Risk-Informed Application The ATF Project Plan was revised to make clear that the NRC staff will continue to take a risk-informed approach to nuclear fuel licensing; however, the Project Plan is not intended to convey guidance on how to pursue risk-informed licensing of the ATF-concept, higher burnup, and increased enrichment fuels. The NRC staff continues to encourage vendors and licensees considering a risk-informed approach to engage early with the staff to identify and resolve the relevant technical and policy issues.

4. NRC Should Clarify its Inclusion of Doped Pellets Within Appendix A As described in the detailed comment responses, the NRC staff has revised the Regulatory Framework Applicability Analysis table (which was removed as Appendix A from the draft ATF Project Plan to allow the NRC staff to make additional changes) to clarify the inclusion of doped pellets, as appropriate. Although the NRC has previously licensed fuel with doped pellets, it is possible that the agency's current regulatory framework (i.e., guidance documents) may not be fully applicable to all future doped pellet concepts; therefore, the information in the doped pellets column will be retained.

5. NRC Should Clearly Indicate that the Project Plan is Not Regulatory Guidance As discussed in the detailed comment responses, the NRC staff agrees that the ATF Project Plan is not intended to convey regulatory requirements or guidance. The NRC staff has made revisions throughout the ATF Project Plan and the Regulatory Framework Applicability Analysis table to clarify that information that the information presented therein should not be interpreted as new regulatory requirements or guidance.

Detailed Comments Comment Number Location in Plan Comment Commenter Recommended Action NRC Response 1

Pages 9 and 10 Regarding the term Consequences in Tasks 3 and 4 in the PRA sectionadd how the NRC plans to address dispersal and consequences.

N/A The ATF Project Plan is intended to contain the agency's strategy to ensure that the staff is ready to expeditiously review applications for ATF designs, higher burnup, and increased enrichment fuels and is not intended to convey guidance to the industry on how to address specific technical challenges associated with those applications. Consistent with the new paradigm described in the plan, the NRC staff encourages vendors and licensees intending to propose a risk-informed approach to licensing these fuel types to engage with the staff early in the process to facilitate the identification and resolution of issues in a timely manner. No changes were made to the project plan to address this comment.

2 General Recommend word search for "must" to ensure the use is intentional and reflects a requirement (as opposed to allowing the industry to explore other means of justifying a position).

N/A The NRC staff reviewed the use of the word "must" and similar wording in the project plan and Regulatory Framework Applicability Analysis and made revisions in those cases where the action was not intended as a requirement.

Comment Number Location in Plan Comment Commenter Recommended Action NRC Response 3

General The project plan contains no evaluation of risk informed fuel applications such as the Alternative Licensing Strategy described in [Electric Power Research Institute] EPRI 3002018457. [Regulatory Guide] (RG) 1.174 only provides broad guidance related to the evaluation of defense-in-depth and design margins without consideration of the relative risks of the proposed licensing change.

Include more information in the document about the use of risk informed applications for submittals and any special considerations for these types of submissions.

See response to Comment 1.

Comment Number Location in Plan Comment Commenter Recommended Action NRC Response 4

General/Section 7.3, Page 25, Additional Considerations Section 7.3 notes the need to address environmental impacts for increased enrichment and burnup applications and notes that the staff may need to consider if it is possible to generically evaluate the environmental impacts. There is a very clear environmental benefit to deploying higher burnup fuels including the ability to support extended operating cycle lengths, reduced batch reload sizes, fewer fuel shipments, reduced uranium mining, and less spent fuel generated.

We encourage the NRC to begin the evaluation of environmental effects of higher burnup/enrichment promptly on a generic basis and incorporate this into the Project Plan. To maximize generic applicability, the industry is prepared to share expected Burnup and Uranium Enrichment requirements for a range of cycle energy plans and reactor types as needed.

The NRC staff is developing a plan to perform a bounding analysis of the environmental impacts associated with the deployment of ATF technologies, such as the transportation of ATF-concept, higher burnup, and increased enrichment fuels and wastes. As a part of this process, the staff will likely engage stakeholders to seek input on information that should be considered as a part of that review. The NRC staff will make the details of the plan available to the public, once it has been finalized.

5 Page 5 The document makes mention of near-term and long-term burnup thresholds. Industry considers both the move up to 68 [gigawatt-days] GWd and 75 GWd to be near-term activities achievable in the mid-2020s even if we may be implementing them sequentially.

Clarify NRCs definition of long-term or revise terminology.

The NRC staff revised the wording to remove the link to near-term and longer-term ATF concepts.

Comment Number Location in Plan Comment Commenter Recommended Action NRC Response 6

Section 3.2, Pg. 9 How does the risk informed framework for applications within fuel licensing fit within the improved fuel licensing paradigm?

What are the expectations -

discussion on guidance related to a risk informed technical basis may be what is warranted within this section.

The NRC staff added an additional discussion to clarify that agency's existing risk-informed framework can be used to support the licensing of nuclear fuel. Consistent with the new paradigm described in the plan, the NRC staff encourages vendors and licensees intending to propose a risk-informed approach to licensing these fuel types to engage with the staff early in the process to facilitate the identification and resolution of issues in a timely manner.

7 Section 3.2.3.

Page 10, last paragraph The described scope of a

[phenomena identification and ranking table] PIRT extends to the full intended use of a given ATF concept, not just its initial licensing application. This approach may represent a wise use of NRC resources but requires extrapolation to future, as yet undefined industry applications.

Clarify the project plan so that PIRT results related to approval for batch reloads be segregated from those needed to credit enhanced safety performance. This will limit the necessary industry and regulatory resources to address phenomena that are applicable to a given [license amendment request] LAR.

PIRTs are not typically done in response to a specific LAR; rather, they are meant to assess the most important phenomena for a particular concept or application and how well those phenomena are understood.

The staff can then apply that knowledge to a particular LAR, whether that request attempts to credit enhanced safety performance, or not. The NRC staff believes that it is worth anticipating the full, intended use of a concept to avoid unnecessary duplication of effort (e.g., conducting multiple PIRTs on the same topic). No changes were made to the project plan in response to this comment.

Comment Number Location in Plan Comment Commenter Recommended Action NRC Response 8

Section 3.2.4.1 This section outlines the need for high quality submittals to meet review timelines with a footnote defining high quality. That definition refers to quantities of data.

Expand on this a little more to include what a high quality, risk-informed licensing submittal would look like and what quantities of data means.

See response to Comment 1.

9 Section 7, Pg. 23, TASK 1: 10 CFR PART 50, 10 CFR PART 52, AND 10 CFR PART 100 REGULATORY FRAMEWORK, INREACTOR PERFORMANCE This section highlights the

[General Design Criteria] GDC, noting that the intent of these principal design and performance requirements should be satisfied even if verbatim compliance cannot be met.

NRC should clarify the use of exemptions for this space.

The NRC staff deleted the text because it was confusing and not necessary for the purposes of the project plan. Consistent with the new paradigm described in the plan, the NRC staff encourages any vendor or licensee that may have concerns about meeting a General Design Criterion or a plant-specific design criterion to engage staff early in the development process.

Comment Number Location in Plan Comment Commenter Recommended Action NRC Response 10 Section 7, under Task 1, second paragraph The NRC separates batch-loading of ATF from crediting safety enhancements of ATF and states the staff anticipates that such changes will need to be made to address batch loading before making changes needed to credit the safety enhancement of ATF in the licensing basis.

The statement seems to be indicating that the NRC will not be ready to review applications that also contain a request to credit the safety enhancements for ATF materials.

Please clarify whether or not this means safety enhancements for ATF materials can be licensed in the near-term. The NRC should not co-mingle any gaps associated with the implementation of ATF and any potential future requests for safety enhancements.

The NRC staff revised the text to clarify that, although submittals for ATF designs have not yet requested approval for the safety enhancements that these fuel designs could potentially afford, future submittals could seek and obtain those approvals.

Comment Number Location in Plan Comment Commenter Recommended Action NRC Response 11 Section 7.2/Appendix B Under Licensing Pathways we would like to see more information in here and in Appendix B that addresses the use of exemptions in the licensing process and how the staff sees that as part of any submittal.

Provide additional information on the use of exemptions in the licensing pathways and any staff considerations.

The need for an exemption will be guided by the plant-specific licensing basis of a facility and the scope of the request. The NRC staff has updated the project plan to discuss potential rulemaking activities related to the ATF-concept, higher burnup, and increased enrichment fuels.

12 Section 7.3, page 25 This section states each LAR review would need a full description and detailed analysis performed by the staff of the environmental effects of transportation of fuel and waste to and from the reactor for these higher enrichment and burnup levels. Is this an expectation for

[lead test assembly] LTAs in addition to batch reloads? If both, is it possible to apply a graded approach?

Clarify this section for LTAs and, if applicable, provide information on a graded approach for LTAs with increased enrichment and burnup.

The extent of the NRC staff's evaluation of the environmental impacts of a proposed action will be determined by the Commission's regulations in 10 CFR Part 51 and the scope of the request. Consistent with the new paradigm described in the plan, the NRC staff encourages licensees intending to pursue and LAR to install a lead test assembly to engage with the staff early in the process to facilitate the identification and resolution of issues in a timely manner.

13 Section 7.3, Pg. 6, under, Additional Considerations The last sentence in Section 7.3 has a typo hav should be have.

Editorial correction Typo corrected.

Comment Number Location in Plan Comment Commenter Recommended Action NRC Response 14 Section 7.4, Lead Test Assemblies This section discusses the NRC-issued guidance letter relative to performing LTA programs under 10 CFR 50.59. In preparation for higher enrichment and higher burnup, it is recognized that an LAR will be required to support such LTA programs. However, it is not clear if a limited scope higher enriched, higher burnup LTA program will require consideration of many of the other regulatory items identified within the Project Plan such as a revised Environmental Assessment.

Please provide additional clarification on the regulatory expectations for a higher enrichment, higher burnup LTA program.

Licensees pursuing LTA programs should consider the guidance in the NRC staffs June 24, 2019, letter regarding the treatment of regulatory issues associated with LTAs. Should a licensee determine that prior approval of an LTA is necessary or that additional clarification is necessary, the NRC staff encourages those to engage with the staff early in the process to facilitate the identification and resolution of issues in a timely manner. Regarding adding additional detail to the project plan, the ATF Project Plan is intended to contain the agency's strategy to ensure that the staff is ready to expeditiously review applications for ATF designs, higher burnup, and increased enrichment fuels and is not intended to convey guidance to the industry on how to address specific technical or regulatory challenges associated with those applications. As such, no changes were made as a result of this comment.

Comment Number Location in Plan Comment Commenter Recommended Action NRC Response 15 Section 8.1.4.1 Industry intends to leverage the Oak Ridge Report on utilizing the existing certified packages for

[low-enriched uranium plus]

LEU+ transport with a future submittal. The Project Plan should address the need for NRC to collaborate with their foreign counterparts on the issue UF6 shipments greater than 5%.

Project Plan should address the need for coordination with foreign counterparts on LEU+ transport.

That NRC staff is engaged internationally (TRANSSC) and will continue to monitor the situation. As necessary, the NRC staff will interact with the Department of Transportation, as that agency is the competent authority with respect to changes to International Atomic Energy Agency Safety Standards Series No. SSR-6, "Regulations for the Safe Transport of Radioactive Material."

16 Section 8.1.4.1, Page 33, under Challenges for Transportation of Uranium Feed Material and Unirradiated Fuel Paragraph 1, second sentence states Transportation of UF6 enriched to greater than 5 weight percent We believe this sentence is missing the word or and and. The sentence should describe the need for new package designs or modifications of existing designs and exemptions if moderator exclusion credit is sought.

Suggested edit:

Transportation of UF6 enriched to greater than 5 weight percent will require the design and certification of new Packages or the modification of currently existing approved packages and an exemption The NRC staff revised the discussion to clarify that the transportation of UF6 enriched to greater than 5 weight percent will require the design and certification of new packages or the modification of currently existing approved packages. Depending on the staffs safety findings, this may include an exemption from the regulations.

17 General -

Appendix A, Page A-1 The introduction to Appendix A should include a statement that this table is for informational purposes and does not supersede or create any new regulatory requirements, guidance, or NRC expectations.

Added language along the lines provided in the comment.

Added a discussion that the Regulatory Framework Applicability Analysis is for informational purposes and does not supersede any regulations or guidance and that the information presented should not be interpreted as new regulatory requirements or guidance.

Comment Number Location in Plan Comment Commenter Recommended Action NRC Response 18 General -

Appendix A The intent of the Doped UO2 Fuel Pellets column is unclear.

Industry already has chromia and gadolinium doped pellets approved and in-service in US reactors. None of the comments can apply to fuel that has already been approved.

Clarify that this column is for pellets above 5%, for pellets expected to be used for higher burn-up, or both.

The NRC staff has previously licensed doped pellet fuels; however, it is possible that the agency's current regulatory framework (i.e., guidance documents) may not be fully applicable to all future doped pellet concepts. As such, no changes were made in response to this comment.

19 General -

Appendix A Table A.1 provides a priority (high, medium, low, [to be determined] TBD) for the various actions identified for closure by the NRC, and associated expected time frame (near-term, medium-term, long-term) which tends to be inverse of the priority (meaning higher priority actions generally tend to have a more near-term expected closure). Are there estimated durations or time frames associated with the closure of near-term, medium-term and long-term actions?

Provide estimated durations or timeframes associated with the closure of near-term, medium-term and long-term actions.

The NRC staff has added a discussion of the expected timeframes for each of the priority levels.

Comment Number Location in Plan Comment Commenter Recommended Action NRC Response 20 Under Columns Burnup to 68 and Burnup to 75 it states Reason: Fragmentation induced

[fission gas release] FGR of high burnup fuel may change

[maximum hypothetical accident/loss-of-coolant accident]

MHA/LOCA source term and timing of release. EPRI test results showed fragmentation does not significantly increase fission gas release.

Fragmentation reduces non-gaseous fission product release into the coolant in a 24-hour soak in water.

A series of fission product release experiments with local burnup up to 78 GWd/[metric ton of uranium] MTU were conducted. Specimens sealed in capsules at different pressures were heated to LOCA temperatures and fission product release was measured. At approximately 20 bars of pressure, fuel fragmentation can be effectively prevented, even for fuel significantly above the perceived fragmentation threshold. The test results showed fission gas release from fragmented fuel is only slightly higher relative to non-fragmented EPRI can provide NRC-[Office of Nuclear Regulatory Research] RES access to EPRI Technical Reports and associated presentations through the existing MOU Addendum on ATF to increase understanding in this area. If desired by NRC and other stakeholders, the EPRI results may also be discussed with subject matter experts through the Fuel Performance and Testing Technical Experts Group (FPTTEG) of the Collaborative Research on Advanced Fuel Technologies for light-water reactors (LWRs) (CRAFT) framework.

The NRC staff revised the entry to provide reference to the Informal Assistance Request closure memorandum and to state that Informal Assistance Request results will be incorporated in Revision 1 of RG 1.183.

Comment Number Location in Plan Comment Commenter Recommended Action NRC Response fuel of the same burnup but under higher pressure. Additional tests at even higher pressure, where fragmentation is suppressed in both cases, showed fission gas release can be further depressed and thus suggests fission gas release during a LOCA transient may be rod internal pressure dependent, i.e., less fission gas is released at higher rod internal pressure.

Some of the test capsules, along with the fuel debris, were filled with water to evaluate non-gaseous fission product release.

Test samples that severely fragmented released less non-gaseous nuclides into the water after a 24-hr soaking period. The lower release rate may be related to lower wettability of smaller particles, a phenomenon well documented in literature.

Comment Number Location in Plan Comment Commenter Recommended Action NRC Response 21 Appendix A, Item

1. 3 on RG 1.183 and Non-LOCA steady-state and transient releases Under Columns Burnup to 75 and Doped UO2 Fuel Pellets it states Reason: Fragmentation-induced FGR of high burnup fuel pellet may change source term and Reactivity initiated accident (RIA) transient fission gas release is not currently well quantified.

In the last 6 years, JAEA conducted several tests with fuel burnup up 84 GWd/MTU (Ref.:

Udagawa, Yutaka, 2018 JAEA Fuel Safety Research Meeting, Mito, Japan, October 30-31, 2018). There is a steady trend of increased release with burnup, but no sudden jump above the perceived fuel fragmentation threshold.

If desired by NRC and other stakeholders, these JAEA results may be discussed by subject matter experts through the Fuel Performance and Testing Technical Experts Group (FPTTEG) of the Collaborative Research on Advanced Fuel Technologies for LWRs (CRAFT) framework.

The NRC staff suggests that this be handled through the CRAFT framework.

22 Appendix A, Item

1. 3 on RG 1.183 and Non-LOCA steady-state and transient releases Under Column 235U Enrichment beyond 5.0 wt% it states Note:

With respect to Table 4, extent of 235U enrichment in RIA empirical database unknown. This note questions the applicability to Table 4 but no action is identified.

Clarify what, if any, actions are expected.

The NRC staff added additional language to clarify that the analytical procedure can be used in lieu of Table 4.

Comment Number Location in Plan Comment Commenter Recommended Action NRC Response 23 Appendix A, Item

1. 5 on RG 1.236 Under Column Burnup to 75 it states Reason: FFRD as result of HBU and possible loss of coolant geometry during RIA has not been well quantified or understood.

It has not been established high burnup fuel would fragment in the same manner in an RIA versus in a LOCA. Fuel fragmentation has been reported in [Japan Atomic Energy Agency] JAEA [Nuclear Safety Research Reactor] NSRR test of short pulse widths, but not clearly present in realistic longer pulse tests. The duration of the NSRR test does not allow enough time for gas to migrate out of the fuel while it is under compression. The short pulse also results in much higher temperatures in the outer radial locations of the fuel.

Fuel fragmentation is known to be suppressed by compressive stress and once the gas is released the driving force for fragmentation may no longer exist.

If desired by NRC and other stakeholders, these JAEA results may be discussed by subject matter experts through the Fuel Performance and Testing Technical Experts Group (FPTTEG) of the Collaborative Research on Advanced Fuel Technologies for LWRs (CRAFT) framework.

The NRC staff suggests that this be handled through the CRAFT framework.

24 Appendix A, Item

1. 5 Item 5 in Table A.1 indicates that high burnup RIA data is needed with deposited energy beyond cladding damage. However, if operating conditions result in deposited energy less than Revise language to indicate may be needed. Check for similarly used language within the Appendix.

The language has been revised to state, "may be."

Comment Number Location in Plan Comment Commenter Recommended Action NRC Response cladding failure, then such data may not be required.

25 Appendix A, Items #5 and #17 Under 235U Enrichment beyond 5.0 wt% it states that higher enrichment will yield higher rod worth and higher peaking. This is not necessarily true. Reactivity, not enrichment, should be the figure of merit. This is because higher enrichment will be balanced with higher burnable poison. It is thus entirely credible that a 6% enriched assembly could be less reactive than a 5%

enriched assembly. The control rods, reactor power level, boron concentrations, and cycle energy requirements are not changing; thus, the assembly reactivities cant be changing meaningfully.

RIA (CRE and CRDA) analyses already specify rod worth limits.

This section and others similar in nature should be revised to replace enrichment with reactivity where merited.

The statement has been revised to indicate that increased enrichment could potentially lead to higher rod worth and peaking factors.

Comment Number Location in Plan Comment Commenter Recommended Action NRC Response 26 Appendix A, Item

1. 6 on 10 CFR 50.46 Under Columns Burnup to 68 and Burnup to 75, the Project Plan is based on a Draft (unapproved) regulation (50.46c).

Since the proposed draft regulation could be approved prior to the implementation of higher burnup fuel, including the draft in the project plan is informative, however, there are no NRC actions identified that would bring this to closure consistent with the expected burnup implementation timeframe.

The information in this section should be based on and revised to meet the current regulatory requirements, not the draft rulemaking.

The NRC staff deleted the note that referred to the draft regulation.

27 Appendix A, Item

1. 6 Under Doped UO2 Fuel Pellets, it is unclear what an exemption is needed for. The industry has deployed doped pellets in operating reactors.

Provide clarification as needed.

The NRC staff removed the statement that an exemption to 10 CFR 50.46 will be needed for doped pellets and changed applicability to fully applicable.

Comment Number Location in Plan Comment Commenter Recommended Action NRC Response 28 Appendix A, Item

1. 8 on Standard Technical Specifications Under 235U Enrichment beyond 5.0 wt% it states TS 4.2.1 is fully applicable pending the outcome of the following: NRC and TSTF to discuss whether or not the term slightly in TS 4.2.1 includes fuels enriched beyond 5%. If industry is consistent with

[Standard Technical Specifications] STS 4.2.1 and STS 4.2.1 is fully applicable to chrome-coated zirconium cladding and doped UO2 pellets it does not seem necessary to revise the Tech Spec.

Industry meeting the STS should be adequate and this should be reflected in the Project Plan.

The NRC staff revised the entry deleted the text stating, "pending outcome of the following."

Comment Number Location in Plan Comment Commenter Recommended Action NRC Response 29 Appendix A, Items #11 on 10 CFR Part 50 Appendix K &

1. 19 on NUREG-2121 Under Columns Burnup to 68 and Burnup to 75, with regard to thermal conductivity degradation (TCD) in Item #11, closure is listed as TBD and is green color coded to indicate NRC has the action. When will this be determined? Is the NRC planning to expand on the cited Information Notice 2009-23?

Provide additional clarification.

The NRC staff anticipates performing assessments prior to the next revision of the RFAA table for those items in the table with closures categorized as TBD. During this assessment, the staff will identify a suggested closure approach and estimated timeframe for those items. The NRC staff does not plan on expanding on IN 2009-23.

Comment Number Location in Plan Comment Commenter Recommended Action NRC Response 30 Appendix A, Items #11 on 10 CFR Part 50 Appendix K Closure bullet in Item #11 states indicates that industry has the action to determine the impact of fuel particle transport and deposition in terms of coolability and criticality. Previous tests quantified a wide range of fuel fragment/particle size (such as those done by Studsvik, Halden, ORNL, etc.) so clarification on what is meant by fuel particle would be helpful. Item #19 has this listed as only a Note but has industry action to close so should this be reworded to say Closure to be consistent with Item #11?

There may be other instances of this throughout Appendix A so it is suggested that the NRC review for consistency.

Clarification on what is meant by fuel particle, review the wording for Item

1. 19 to be consistent with

1. 11, and review Appendix A for consistency.

The term "fuel particle" was intended to refer to that portion of a fuel pellet that has broken off from the main pellet, exited the rod, and is now capable of being transported throughout the coolant system and possibly deposited. The word "particle" was initially used to refer to this fuel pellet portion, and no attempt to make any delineation between a fuel fragment or a fuel particle was intended. Therefore, the text has been updated to refer to "fuel fragment/particle."

Comment Number Location in Plan Comment Commenter Recommended Action NRC Response 31 Appendix A, Items #11 on 10 CFR 50 Appendix K &

1. 19 on NUREG-2121 Under Columns Burnup to 68 and Burnup to 75, a Burnup Threshold is used. While burnup is a key parameter in the determination of FFRD (namely fragmentation), other factors may be appropriate for an FFRD threshold. Numerous LOCA simulation tests have been performed, both in-pile and out-pile. While most of the tests show a burnup-threshold, some high burnup fuel did not fragment and thus other factors, such as pre-transient power and testing conditions, may be involved.

EPRI test results showed fission gas release occurs with and without fuel fragmentation.

Fission gas release is pressure dependent, with lower release while under pressure/before burst. It is not known if fission gas not released due to rod internal pressure would be released upon rod burst.

Replace Burnup Threshold with Threshold.

The table has been updated to replace the term "Burnup Threshold" with "Threshold."

Comment Number Location in Plan Comment Commenter Recommended Action NRC Response 32 Appendix A, Item

1. 12, 10 CFR 51.21 Environmental Assessment (EA) vs. 51.22 Categorical Exclusion (CATEX)

For the discussion of 10 CFR 51.21 environmental assessment versus 10 CFR 51.22 categorical exclusion, it is unclear if this would apply to a 10 CFR Part 50 (or 52) license holder versus a Part 72 license holder versus a fuel manufacturer/enricher. The second bullet for [burnup] BU and enrichment only discusses performing an environmental assessment for transportation. It is unclear if an LAR (under 50.90) would require an EA based on Project Plan.

Provide clarity.

Clarified that the recommendation applies to the first LAR for a 10 CFR Part 50 or Part 52 licensee.

Comment Number Location in Plan Comment Commenter Recommended Action NRC Response 33 Appendix A, Item

1. 15 Reactivity, not enrichment, should be the figure of merit.

50.68 even alludes to this. It says that [k-effective] keff must be less than 0.95; which makes sense.

But it goes on to limit enrichment to 5%. With the potential need to increase enrichment levels for both existing commercial LWR reactors and advanced reactors, the appropriate action is to remove specific enrichment limits from 10 CFR 50.68. Retention of the necessary enrichment limits in the facility licensing bases, including Technical Specifications, provides adequate protection for criticality safety margins.

The language should be revised to reflect the need to keep keff below 0.95, and let the licensee manage how to do that (enrichment, burnable poison, exposure, spacing, rack inserts etc.).

The facility specific enrichment limit is included in the facility license, so its inclusion in 50.68 is unnecessary.

That language in the table reflects that which is in the Rule. No changes were made in response to this comment.

Comment Number Location in Plan Comment Commenter Recommended Action NRC Response 34 Appendix A, Item

1. 17 on NUREG-0800 SRP Chapter 4.2 Under 235U Enrichment beyond 5.0 wt% it states Note:

Increased enrichment will promote higher rod worth and peaking factors and thus fuel enthalpy rise during RIAs.

Recommend changing will to may. NRC should check for other prescriptive language in the document.

The NRC staff revised the note to state, "Increased enrichment could potentially lead to higher rod worth and peaking factors."

35 Appendix A, #19 on NUREG-2121 Studsvick is misspelled and should be Studsvik Editorial correction.

Typo corrected.

36 Appendix A, Item

1. 23 on RG 1.240 and NEI 12-16 Revision 4 Under Column 235U Enrichment beyond 5.0 wt% it states Criticality codes must be validated with experiments that cover the applicable enrichment range. As itemized in Section 8.1.4.1 (page 33) of the Project Plan, there is more than one way to show that an experiment is applicable to a particular validation. However, the way it is written, this statement can be interpreted as validation has to be done using critical experiments that cover the applicable enrichment range and therefore, new critical experiments are definitely needed.

Recommend revising this sentence (and other similar items for RG 1.240 and NEI 12-16, Revision 4 in the project plan) to be consistent with the listed potential approaches in Section 8.1.4.1 for this item. A recommended revision can be: Criticality code validation needs to demonstrate that validation is applicable to the increased enrichment range (discussion in Section 8.1.4.1). Also - please replace the word must with may need to. Check the document for the use of other prescriptive language.

The NRC staff revised the text to state, "Criticality code validation needs to demonstrate that validation is applicable to the increased enrichment range (discussion in Section 8.1.4.1).

Comment Number Location in Plan Comment Commenter Recommended Action NRC Response 37 Appendix A, Items #23 on RG 1.240 and NEI 12-16 Revision 4 and #24 on NUREG-0800 (Standard Review Plan 9.1.1)

Under Column Doped UO2 Fuel Pellets it states Note:

Experiments for validation of criticality codes may be necessary. Similar to previous comments, the Project Plant should list the alternative approaches (e.g., sensitivity and uncertainty analysis as discussed in Section 8.1.4.1)

Recommend revising this sentence to be consistent with the listed potential approaches in Section 8.1.4.1 for this item.

The NRC staff revised the note to state, "Criticality codes need to be validated for doped fuel." Per Section 7.1.4.1 of the ATF Project Plan, this could potentially be done in numerous ways.

38 Appendix A, Item

1. 23 on RG 1.240 and NEI 12-16 Revision 4 Under Column Doped UO2 Fuel Pellets it states 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.

This note treats doped pellets as a new fuel design; existing work from ORNL (and perhaps others) shows that for [spent fuel pool]

SFP criticality, dopants are of minimal importance.

Recommend a note as in other places in green:

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

The NRC staff understands that for existing dopants that have been approved for use, research indicates that the dopants may have a minimal impact on spent fuel pool criticality.

However, if new dopants are developed, they may not exhibit the same behavior. No changes were made in response to this comment.

39 Appendix A, Item

1. 25 on NUREG-0800 (SRP 9.1.2)

Under Doped UO2 Fuel Pellets it states Note: Higher density fuel may lead to more 235U in the spent fuel pool; experiments for validation of criticality codes may be necessary.

Clarify if the two fragments (separated by semi-colon) are intended to be linked.

The first part of the note is unnecessary and should be removed since criticality analyses must account for fuel density accurately or conservatively. For the Second part - see earlier comment on Items #23 and

1. 24.

The NRC staff deleted this note because it was not necessary.

Comment Number Location in Plan Comment Commenter Recommended Action NRC Response 40 Appendix B Appendix B notes the possibility of [Advisory Committee on Reactor Safeguards] ACRS reviews of industry submittals.

NRC should address the steps that can be taken to avoid ACRS reviews delaying the approval of industry submittals, such as early coordination with ACRS and conducting reviews in parallel.

For topical report reviews, the ACRS review is an inherent part of the timeline. For LAR reviews, it is not certain that ACRS review will be requested. NRC staff will follow current guidance for requests by ACRS to review an LAR, which includes early engagement and coordination with ACRS staff. The additional time needed for an ACRS review is expected to be minimal and should not significantly affect the schedule for approving an LAR.

41 Appendix B Figure B.1-1, blue box says SRP 4.2 RIA testing. The use of the term testing is too prescriptive.

Suggest changing it.

Change testing to evaluation.

The figures have been updated to reflect changes made to the table.

ML21314A531 OFFICE NRR/DORL/LPLII-2/PM NRR/DORL/LPLII-2/LA NRR/DORL/LP2-2/BC NAME MWentzel RButler DWrona DATE 11/12/2021 11/15/2021 11/16/2021 OFFICE NMSS/DFM/D NMSS/REFS/DD NRR/DRA/D NAME SHelton KCoyne MFranovich DATE 11/17/2021 11/17/2021 11/18/2021 OFFICE RES/DSA/D NRR/DORL/D NRR/DSS/D NAME KWebber BPham JDonoghue DATE 11/17/2021 11/18/2021 11/19/2021