ML22045A480

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Supplement - Application to Implement an Alternate Defense-in-Depth Categorization Process, an Alternate Pressure Boundary Categorization Process, and an Alternate Seismic Categorization Process in Accordance with
ML22045A480
Person / Time
Site: Limerick  Constellation icon.png
Issue date: 02/14/2022
From: David Helker
Constellation Energy Generation, Exelon Generation Co
To:
Document Control Desk, Office of Nuclear Reactor Regulation
References
Download: ML22045A480 (14)
v • d • e


Text

200 Exelon Way Kennett Square, PA 19348 www.ConstellationEnergy.com

10 CFR 50.90 10 CFR 50.69

February 14, 2022

U.S. Nuclear Regulatory Commission Washington, DC 20555-0001 ATTN: Document Control Desk

Limerick Generating Station, Units 1 and 2 Renewed Facility Operating License Nos. NPF-39 and NPF-85 NRC Docket Nos. 50-352 and 50-353

Subject:

Supplement - Application to Implement an Alternate Defense-in-Depth Categorization Process, an Alternate Pressure Boundary Categori zation Process, and an Alternate Seismic Categorization Process in Acc ordance with the Requirements of 10 CFR 50.69, "Risk-Informed Categoriz ation and Treatment of Structures, Systems and Components for Nuclear Pow er Reactors"

References:

1. Exelon Generation Company, LLC letter to the U.S. Nuclear Regulatory Commission, Limerick Generating Station, Units 1 and 2, "Applic ation to Implement an Alternate Defense-in-Depth Categorization Process, an Alternate Pressure Boundary Categorization Process, and an Alternate Seismic Tier 1 Categorization Process in Accordance with the Requirements of 10 CFR 50.69, 'Risk-Informed Categorization and Treatment of Structures, Systems and Components for Nuclear Pow er Reactors,'" dated March 11, 2021 (ADAMS Accession No. ML21070A412).
2. Exelon Generation Company, LLC letter to the U.S. Nuclear Regulatory Commission, Limerick Generating Station, Units 1 and 2, Supplem ent -

Application to Implement an Alternate Defense-in-Depth Categori zation Process, an Alternate Pressure Boundary Categorization Process, and an Alternate Seismic Categorization Process in Accordance with the Requirements of 10 CFR 50.69, "Risk-Informed Categorization and Treatment of Structures, Systems and Components for Nuclear Pow er Reactors'," dated December 15, 2021 (ADAMS Accession No. ML21349B364).

3. Alternative Approaches for Addressing Seismic Risk in 10 CFR 50.69 Risk-Informed Categorization, EPRI, Palo Alto, CA: 2020. 300201 7583.
4. Email from A. Klett (U.S. Nuclear Regulatory Commission) to G. Stewart (Exelon Generation Company, LLC), "Audit Plan Supplement for LI M 50.69 LAR (L-2021-LLA-0042)," dated January 24, 2022 (ADAMS Accession No. ML22028A183).

Supplement - License Amendment Request 10 CFR 50.69 Alternate Categorization Processes Docket Nos. 50-352 and 50-353 February 14, 2022 Page 2

In Reference [1], Exelon Generation Company, LLC (Exelon) submi tted an application for amendment of the Renewed Facility Operating License Nos. NPF-39 and NPF-85 for Limerick Generating Station (Limerick), Units 1 and 2, respecti vely. The proposed amendments would modify the licensing basis by revising the related License Condition in Appendix C to allow the use of an alternate defense-in-depth categorization process, an alternate pressure boundary categorization process, and an alte rnate seismic categorization process for implementation of the risk-informed categorization and treatment of structures, systems, and components for Limerick in accordance with the req uirements of 10 CFR 50.69.

By letter dated December 15, 2021 (Reference [2]), Exelon submi tted a supplement to pursue the alternate Seismic Tier 2 categorization process described in Electric Power Research Institute (EPRI) Report 3002017583, "Alternative Approaches for Addressing Seismic Risk in 10 CFR 50.69 Risk-Informed Categorization," dat ed February 2020 (Reference [3]) rather than the alternate Seismic Tier 1 catego rization process described in the same EPRI Report as originally proposed in Reference [1].

By email dated January 24, 2022 (Reference [4]), the NRC sent a supplement to NRCs Audit Plan dated October 1 and 21, 2021 (ADAMS Accession Nos. ML21263A248 and ML21295A036), which included a new set of audit questions perta ining to the supplement dated December 15, 2021. This letter supplements the Reference [2] letter and provides the responses to the new audit questions included in the NRC's emai l (see Attachment 1). In addition, as a result of responding to the audit questions, a change is required to the Facility Operating License (FOL) Appendix C License Condition wording th at was proposed in the Reference [2] supplement letter. Attachment 2 to this letter p rovides the revised FOL Appendix C License Condition markups.

Note: On November 16, 2021, NRC issued an Order approving Exelo ns application for the indirect transfer of Limericks Renewed Facility Operating Lice nse Nos. NPF-39 and NPF-85 for Units 1 and 2, respectively, to Constellation Energy Generation, LLC (CEG). By letter dated January 24, 2022, Exelon informed the NRC that all requir ed regulatory approvals necessary to close the transfer had been received and that the transfer would close on February 1, 2022. On February 1, 2022, NRC issued the conformin g license amendments following completion of the transfer to CEG.

CEG has reviewed the information supporting the No Significant Hazards Consideration and the Environmental Consideration that was previously provide d to the NRC in Reference [1] and Reference [2]. The information in this LAR s upplement does not impact the conclusion that the proposed license amendments do not involve a significant hazards consideration. The information also does not impact the conclus ion that there is no need for an environmental assessment to be prepared in support of the proposed amendments.

There are no regulatory commitments contained in this supplement.

In accordance with 10 CFR 50.91, "Notice for public comment; State consultation,"

paragraph (b), CEG is notifying the Commonwealth of Pennsylvani a of this license Supplement - License Amendment Request 10 CFR 50.69 Alternate Categorization Processes Docket Nos. 50-352 and 50-353 February 14, 2022 Page 3

amendment request supplement by transmitting a copy of this letter to the designated State Official.

If you have any questions regarding this submittal, then please contact Glenn Stewart at 610-765-5529.

I declare under penalty of perjury that the foregoing is true and correct. Executed on this 14th day of February 2022.

Respectfully,

David P. Helker Sr. Manager - Licensing and Regulatory Affairs Constellation Energy Generation, LLC

Supplement - License Amendment Request, Applicati on to Implement Alternate Categorization Processes in Accordance with the Requi rements of 10 CFR 50.69. : Revised Proposed FOL Appendix C License Condition Markups

cc: Regional Administrator - NRC Region I w/ attachments NRC Senior Resident Inspector - Limerick Generating Station "

NRC Project Manager, NRR - Limerick Generating Station "

Director, Bureau of Radiation Protection - Pennsylvania Departm ent of Environmental Protection "

ATTACHMENT 1

Supplement - License Amendment Request

Limerick Generating Station, Units 1 and 2 NRC Docket Nos. 50-352 and 50-353

Application to Implement an Alternate Defense-in-Depth Categori zation Process, an Alternate Pressure Boundary Categorization Process, and an Alternate Seismic Categorization Process in Accordance with the Requirements of 10 CFR 50.69, "Risk-Informed Categorization and Treatment of Structures, Systems and Components for Nuclear Power Reactor s"

Supplement - License Amendment Request Attachment 1 10 CFR 50.69 Alternate Categorization Processes Page 1 of 5 Docket Nos. 50-352 and 50-353

In Reference [1], Exelon Generation Company, LLC (Exelon) [now Constellation Energy Generation, LLC (CEG)] submitted an application for amendment o f the Renewed Facility Operating License Nos. NPF-39 and NPF-85 for Limerick Generating Station (Limerick), Units 1 and 2, respectively.

The proposed amendments would modify the licensing basis by rev ising the related License Condition in Appendix C to allow the use of an alternate defense-in-depth categorization process, an alternate pressure boundary categorization process, and an alternate seismic categorization process for implementation of the risk-informed categorization and treatment of structures, systems, and components for Limerick in accordance with the requirements of 10 CFR 50.69.

By letter dated December 15, 2021 (Reference [2]), Exelon [CEG] submitted a supplement to pursue the alternate Seismic Tier 2 categorization process described in Electric Power Research Institute (EPRI) Report 3002017583, "Alternative Appro aches for Addressing Seismic Risk in 10 CFR 50.69 Risk-Informed Categorization," dated Febru ary 2020 (Reference [3])

rather than the alternate Seismic Tier 1 categorization process described in the same EPRI Report as originally proposed in Reference [1].

By email dated January 24, 2022 (Reference [4]), the NRC sent a supplement to NRCs Audit Plan dated October 1 and 21, 2021 (ADAMS Accession Nos. ML21263A248 and ML21295A036), which included a new set of audit questions perta ining to the supplement dated December 15, 2021. This letter supplements the Reference [2] l etter and provides the responses to the new audit questions included in the NRC's emai l. A restatement of the NRC questions along with the responses are provided below.

In addition, as a result of responding to the audit questions, a change is required to the Facility Operating License (FOL) Appendix C License Condition wording th at was proposed in the Reference [2] supplement letter. Attachment 2 to this letter p rovides the revised FOL Appendix C License Condition markups.

APLC Use of Different Approaches for Seismic Risk Consideration in 10 CFR 50.69 Categorization

The proposed license condition in Section 2.2 of Attachment 1 to the supplement dated December 15, 2021 (Agencywide Document Accession and Management System (ADAMS)

Accession No. ML21349B364) states that categorization of system s can be performed using either the previously approved Seismic Margins Analysis (SMA) a pproach or the proposed alternative seismic approach. Section 3.1.1 of Enclosure 1 to the submittal dated March 11, 2021 (ADAMS Accession No. ML21070A412), discusses the overall categorization process. Based on the available information in the original submittal and subsequent supplements, including the supplement dated December 15, 2021, it is unclear to the NRC staff which approach will be used for categorizing an entire system.

The discussion of the Tier 1 approach in Sections 3.1.1 and 4.1 of Enclosure 1 to the submittal dated March 11, 2021, is not changed by the supplement dated December 15, 2021. The purpose of retaining the mention of the Tier 1 approach, whic h is no longer being requested or reviewed per the supplement dated December 15, 2021, in these s ections is unclear to the NRC staff.

Supplement - License Amendment Request Attachment 1 10 CFR 50.69 Alternate Categorization Processes Page 2 of 5 Docket Nos. 50-352 and 50-353

Table 1 in Attachment 1 to the supplement dated December 15, 20 21, has two different entries under seismic in the Risk (Non-modeled) element. It is unc lear to the NRC staff whether the first entry is for the previously approved SMA approach. Theref ore:

i. Confirm that the licensee proposes to use a single approach (i.e., either SMA or, if approved, the proposed alternative seismic approach described i n the supplement dated December 15, 2021) for categorization of an entire system. If t he licensee proposes to use different approaches for different components of the same s ystem, then justify the validity of such an implementation given the differences in the underlying basis for the approaches and the guidance in NEI 00-04, Revision 0 (ADAMS Acc ession No. ML052910035), which indicates the use of a single approach for categorizing a system.

Response

Limerick will use a single approach (i.e., either SMA or, if approved, the proposed Tier 2 alternative seismic approach described in the supplement dated December 15, 2021) for categorization of an entire system.

ii. Clarify whether not changing the mention of Tier 1 approa ch from Sections 3.1.1 and 4.1 of Enclosure 1 to the submittal dated March 11, 2021, via the supplement dated December 15, 2021, is an oversight. If it is, then provide the updated text for those sections. If it is not, then provide the justification, given that the Tier 1 approach is no longer being requested by the licensee or reviewed by the NRC s taff.

Response

Not changing the mention of the Tier 1 [to Tier 2] approach from Sections 3.1.1 and 4.1 of Enclosure 1 to the submittal dated March 11, 2021, via the supplement dated December 15, 2021, was an oversight. Updated text for those se ctions is provided below.

3.1.1 Overall Categorization Process

(NOTE: The only change was to replace Tier 1 with Tier 2 in the first and second paragraphs.)

The alternate defense-in-depth categorization process, the alte rnate pressure boundary categorization process, and the alternate Seismic Tier 2 catego rization process are discussed in the following sections.

The alternate defense-in-depth categorization process, the alte rnate pressure boundary categorization process, and/or the alternate Seismic Tier 2 cat egorization process may be implemented for any system that was previously categorized o r systems that will be categorized. However, any system that has been previously cate gorized is not required to be re-categorized with the alternate defense-in-depth catego rization process, the alternate pressure boundary categorization process, or the alte rnate Seismic Tier 2 Supplement - License Amendment Request Attachment 1 10 CFR 50.69 Alternate Categorization Processes Page 3 of 5 Docket Nos. 50-352 and 50-353

categorization process. The processes identified in the current License Condition Appendix C may continue to be used.

No assignments of Risk-Informed Safety Class (RISC) to SSCs are completed until a system is individually categorized, since categorization must b e performed for entire systems and structures, not for selected components within a system or structure.

4.1 APPLICABLE REGULATORY REQUIREMENTS/CRITERIA

(NOTE: The only change was to replace Tier 1 with Tier 2 in the last paragraph.)

The following NRC requirements and guidance documents are applicable to the proposed change:

  • The regulations in Title 10 of the Code of Federal Regulations (10 CFR)

Part 50.69, "Risk-Informed Categorization and Treatment of Stru ctures, Systems and Components for Nuclear Power Reactors."

  • NRC Regulatory Guide 1.201, "Guidelines for Categorizing Struc tures, Systems, and Components in Nucle ar Power Plants According to their Safety Significance," Revision 1, May 2006.

The alternate defense-in-depth categorization process, the alte rnate pressure boundary categorization process, and the alternate Seismic Tier 2 categorization process continue to meet the above regulation and regulatory guidance.

iii. Confirm that only the Tier 2 alternative seismic approach is being requested for use in the licensees 10 CFR 50.69 program, clarifying the intent of m ultiple instances of statements such as Exelon considers the Limerick site to be a Tier 1 site in the context of the NRC staffs review of the Tier 2 approach and the prop osed license condition (see APLC-02).

Response

As noted in the response to sub-part i above and the response t o APLC-02 below, other than the use of SMA, only the Tier 2 alternative seismic approa ch is being requested for use in the Limerick 10 CFR 50.69 program.

iv. Confirm that the first entry under seismic in the Risk ( Non-modeled) element in Table 1 in Attachment 1 to the supplement dated December 15, 20 21, applies to the Supplement - License Amendment Request Attachment 1 10 CFR 50.69 Alternate Categorization Processes Page 4 of 5 Docket Nos. 50-352 and 50-353

previously approved SMA approach. If such confirmation cannot be provided, then explain the intent, purpose, and use of this entry in the conte xt of the supplement dated December 15, 2021, and the licensees approved 10 CFR 50.69 pro gram.

Response

The first entry under seismic in the Risk (Non-modeled) element in Table 1 in Attachment 1 to the supplement dated December 15, 2021, applies to the previously approved SMA approach.

APLC RAI 02 - Proposed Changes to License Condition

The proposed license condition in Section 2.2 of Attachment 1 to the supplement dated December 15, 2021, states, in part:

In addition, Exelon is approved to implement 10 CFR 50.69 using any of the following alternate processes for categorization of RISC-1, RIS C-2, RISC-3, and RISC-4 SSCs: the defense-in-depth approach contained in PWROG-2 0015-NP; the passive pressure boundary categorization approach described in EPRI 3002015999; and the alternative seismic approach as described i n Exelon's submittal letter dated March 11, 2021, and associated supplemen ts, as specified in Unit [1] License Amendment No. [XXX] dated [DATE].

While the licensee states in Attachment 1 to the supplement dated December 15, 2021, that the information in each section of the supplement supersedes the in formation in the corresponding section of the submittal dated March 11, 2021, in its entirety, the NRC staff identified instances from the submittal dated March 11, 2021, where the Tier 1 appr oach does not appear to be superseded (see APLC-01 (ii)). Further, the supplement dated December 15, 2021, includes language such as Exelon considers the Limerick site to be a Ti er 1 site (see APLC-01 (iii)).

Therefore, the dated March 11, 2021, and associated supplements, portion of the proposed license condition is ambiguous. The use of and associated supplements in the proposed license condition could be misinterpreted to mean that the NRC would be approving both the approach (i.e., the Tier 1 approach) in the submittal dated March 11, 2021, and the approach (i.e., the Tier 2 approach) in the supplement dated December 15, 2021. This is inconsistent with the licensees request in, and the NRC staff s review of the supplement dated December 15, 2021. The NRC staff notes that the use of and as sociated supplements language in previous NRC-approved amendments (e.g., ADAMS Acces sion Nos. ML19330D909 and ML21082A422) was appropriate for those cas es because the supplements clarified or updated the same approach that was pro posed in the corresponding LAR submittals. However, Limeri cks situation is different in that the supplement dated December 15, 2021, proposes an approach which is different from that in the LAR submittal (i.e., the submittal dated March 11, 2021).

Please revise the license condition to reference only the suppl ements that include the Tier 2 approach (e.g., the December 15 supplement and any subsequent relevant supplement(s)) or revise the license in some other way to make it unambiguous tha t only the Tier 2 alternative seismic approach is approved for use in Limericks 10 CFR 50.69 program.

Supplement - License Amendment Request Attachment 1 10 CFR 50.69 Alternate Categorization Processes Page 5 of 5 Docket Nos. 50-352 and 50-353

Response

The proposed license condition will be revised to reference only the supplements that include the Tier 2 approach as noted below:

In addition, Constellation Energy Generation, LLC (CEG) is approved to implement 10 CFR 50.69 using any of the following alternative processes for categorization of RISC-1, RISC-2, RISC-3, and RISC-4 SSCs as specified in Unit [1] License Amendment No. [XXX] dated

[DATE]:

  • the alternative defense-in-depth approach contained in PWROG-20015-NP,
  • the alternative passive pressure boundary categorization approach described in EPRI 3002015999, and
  • the alternative seismic approach as described in the licensee's letters dated December 15, 2021, and February 14, 2022.

The revised proposed license condition markups reflecting the r esponse above are provided in.

6. REFERENCES

[1] Exelon Generation Company, LLC letter to the U.S. Nuclear R egulatory Commission, Limerick Generating Station, Units 1 and 2, "Application to Implement an Alternate Defense-in-Depth Categorization Process, an Alternate Pressure Boundary Categorization Process, and an Alternate Seismic Tier 1 Categorization Process [...]," dated March 11, 2021 (ADAMS Accession No. ML21070A412).

[2] Exelon Generation Company, LLC letter to the U.S. Nuclear R egulatory Commission, Limerick Generating Station, Units 1 and 2, "Supplement - Application to Implement an Alternate Defense-in-Depth Categorization Process, an Alternate Pressure Boundary Categorization Process, and an Alternate Seismic Categorization Process [...]," dated December 15, 2021 (ADAMS Accession No. ML21349B364).

[3] Alternative Approaches for Addressing Seismic Risk in 10 CF R 50.69 Risk-Informed Categorization, EPRI, Palo Alto, CA: 2020. 3002017583.

[4] Email from A. Klett (U.S. Nuclear Regulatory Commission) to G. Stewart (Exelon Generation Company, LLC), "Audit Plan Supplement for LIM 50.69 LAR (L-2021-LLA-0042)," dated January 24, 2022 (ADAMS Accession No. ML22028A183 ).

Attachment 2

Supplement - License Amendment Request

Limerick Generating Station, Units 1 and 2 Docket Nos. 50-352 and 50-353

Application to Implement an Alternate Defense-in-Depth Categori zation Process, an Alternate Pressure Boundary Categorization Process, and an Alternate Seismic Categorization Process in Accordance with the Requireme nts of 10 CFR 50.69, "Risk-Informed Categorization and Treatment of S tructures, Systems and Components for Nuclear Power Reactors"

Revised Proposed FOL Appendix C License Condition Markups

APPENDIX C

ADDITIONAL CONDITIONS OPERATING LICENSE NO. NPF-39

Constellation Energy Generation, LLC shall comply with the following conditions on the schedule noted below:

Amendment No. Additional Conditions

230, 255, [XXX] Constellation Energy Generation, LLC is approved to implement 10 CFR 50.69 using the processes for categorization of Risk-Informed Safety Class (RISC)-1, RISC-2, RISC-3, and RISC-4 structures, systems, and components (SSCs) using:

Probabilistic Risk Assessment (PRA) models to evaluate risk associated with internal events, including internal flooding, and internal fire; the shutdown safety assessment process to assess shutdown risk; the Arkansas Nuclear One, Unit 2 (ANO-2) passive categorization method to assess passive component risk for Class 2 and Class 3 SSCs and their associated supports; and the results of non-PRA evaluations that are based on the IPEEE Screening Assessment for External Hazards, i.e., seismic margin analysis (SMA) to evaluate seismic risk, and a screening of other external hazards updated using the external hazard screening significance process identified in ASME/ANS PRA Standard RA-Sa-2009; as specified in Unit 1 License Amendment No. 230 dated July 31, 2018.

Constellation Energy Generation, LLC will complete the implementation items listed in Attachment 2 of Exelon letter to NRC dated April 23, 2018 prior to implementation of 10 CFR 50.69. All issues identified in the attachment will be addressed and any associated changes will be made, focused-scope peer reviews will be performed on changes that are PRA upgrades as defined in the PRA standard (ASME/ANS RA-Sa-2009, as endorsed by RG 1.200, Revision 2), and any findings will be resolved and reflected in the PRA of record prior to implementation of the 10 CFR 50.69 categorization process.

Prior NRC approval, under 10 CFR 50.90, is required for a change to the categorization process specified above (e.g., change from a seismic margins approach to a seismic probabilistic risk assessment approach).

Renewed License No. NPF-39 Amendment No. 128, 131, 147, 184, 230, 255 UNIT 1 FOL INSERT

In addition, Constellation Energy Generation, LLC (CEG) is appr oved to implement 10 CFR 50.69 using any of the following alternative processes for cate gorization of RISC-1, RISC-2, RISC-3, and RISC-4 SSCs as specified in Unit 1 License Amendmen t No. [XXX] dated [DATE]:

  • the alternative defense-in-depth approach contained in PWROG-2 0015-NP,
  • the alternative passive pressure boundary categorization appro ach described in EPRI 3002015999, and
  • the alternative seismic approach as described in the licensee' s letters dated December 15, 2021, and February 14, 2022.

APPENDIX C

ADDITIONAL CONDITIONS OPERATING LICENSE NO. NPF-85

Constellation Energy Generation, LLC shall comply with the following conditions on the schedule noted below:

Amendment No. Additional Conditions

193, 217, [YYY] Constellation Energy Generation, LLC is approved to implement 10 CFR 50.69 using the processes for categorization of Risk-Informed Safety Class (RISC)-1, RISC-2, RISC-3, and RISC-4 structures, systems, and components (SSCs) using:

Probabilistic Risk Assessment (PRA) models to evaluate risk associated with internal events, including internal flooding, and internal fire; the shutdown safety assessment process to assess shutdown risk; the Arkansas Nuclear One, Unit 2 (ANO-2) passive categorization method to assess passive component risk for Class 2 and Class 3 SSCs and their associated supports; and the results of non-PRA evaluations that are based on the IPEEE Screening Assessment for External Hazards, i.e., seismic margin analysis (SMA) to evaluate seismic risk, and a screening of other external hazards updated using the external hazard screening significance process identified in ASME/ANS PRA Standard RA-Sa-2009; as specified in Unit 2 License Amendment No. 193 dated July 31, 2018.

Constellation Energy Generation, LLC will complete the implementation items listed in Attachment 2 of Exelon letter to NRC dated April 23, 2018 prior to implementation of 10 CFR 50.69. All issues identified in the attachment will be addressed and any associated changes will be made, focused-scope peer reviews will be performed on changes that are PRA upgrades as defined in the PRA standard (ASME/ANS RA-Sa-2009, as endorsed by RG 1.200, Revision 2), and any findings will be resolved and reflected in the PRA of record prior to implementation of the 10 CFR 50.69 categorization process.

Prior NRC approval, under 10 CFR 50.90, is required for a change to the categorization process specified above (e.g., change from a seismic margins approach to a seismic probabilistic risk assessment approach).

Renewed License No. NPF-85 Amendment No. 193, 217 UNIT 2 FOL INSERT

In addition, Constellation Energy Generation, LLC (CEG) is appr oved to implement 10 CFR 50.69 using any of the following alternative processes for cate gorization of RISC-1, RISC-2, RISC-3, and RISC-4 SSCs as specified in Unit 2 License Amendmen t No. [YYY] dated [DATE]:

  • the alternative defense-in-depth approach contained in PWROG-2 0015-NP,
  • the alternative passive pressure boundary categorization appro ach described in EPRI 3002015999, and
  • the alternative seismic approach as described in the licensee' s letters dated December 15, 2021, and February 14, 2022.
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