L-MT-25-002, Request for Exemption from 10 CFR 50.55a(a)(3)(ii) for Adopting ASME Code Case N-921 and 10 CFR 50.55a(v)

Request for Exemption from 10 CFR 50.55a(a)(3)(ii) for Adopting ASME Code Case N-921 and 10 CFR 50.55a(v)

ML25097A091
Person / Time
Site:	Monticello
Issue date:	04/04/2025
From:	Hafen S Northern States Power Co, Xcel Energy
To:	Office of Nuclear Reactor Regulation
References
L-MT-25-002
Download: ML25097A091 (1)

Text

2807 West County Road 75 Monticello, MN 55362 April 4, 2025 L-MT-25-002 10 CFR 50.12 ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, DC 20555-0001 Monticello Nuclear Generating Plant Docket No. 50-263 Subsequent Renewed Facility Operating License No. DPR-22 Request for Exemptions from 10 CFR 50.55a(a)(3)(ii) for Adopting ASME Code Case N-921, and 10 CFR 50.55a(y)

In accordance with 10 CFR 50.12, "Specific exemptions," Northern States Power Company, a Minnesota corporation, doing business as Xcel Energy (hereafter "NSPM") requests NRC approval of exemptions from 10 CFR 50.55a(y) and 10 CFR 50.55a(a)(3)(ii), which incorporates by reference Regulatory Guide 1.147, "Inservice Inspection Code Case Acceptability, ASME Code Section XI, Division 1," Revision 21. Table 2 of the regulatory guide, "Conditionally Acceptable Section XI Code Cases," contains a provision limiting adoption of the American Society of Mechanical Engineers (ASME) Code Case N-921, "Alternative 12-yr Inspection Interval Duration Section XI, Division 1," to only at the beginning of an Inservice Inspection (ISI) interval as part of a routine update of the ISI program. NSPM requests an exemption for the Monticello Nuclear Generating Plant (MNGP) ISI Program 6th Interval due to Code Case N-921 not being applied at the beginning of the interval routine update. The MNGP ISI Program 6th Interval started prior to the issuance of Regulatory Guide 1.147, Revision 21.

NSPM's exemption request also extends to the definition of Inservice Inspection Interval of 10 CFR 50.55a(y). This exemption is being submitted as reflected in the Final Rule noticed in the Federal Register that incorporated Regulatory Guide 1.147, Revision 21, into 10 CFR 50.55a.

The exemption is requested for the duration of the MNGP ISI Program 6th Interval. Details for this exemption request are enclosed.

NSPM requests the approval of this request by September 30, 2025.

Summary of Commitments This letter makes no new commitments and no revisions to existing commitments.

If you should have any questions regarding this submittal, please contact Ron Jacobson by phone (612) 330-6542 or email: ronald.g.jacobson@xcelenergy.com.

fl Xcel Energy

Document Control Desk L-MT-25-002 Page 2 Sha Hafen Site Vice P sident, Monticello Nuclear Generating Plant Northern States Power Company - Minnesota Enclosure cc:

Administrator, Region Ill, USNRC Project Manager, Monticello, USNRC Resident Inspector, Monticello, USNRC

L-MT-25-002 NSPM Enclosure Page 1 of 11 REQUEST FOR AN EXEMPTION FROM 10 CFR 50.55a(a)(3)(ii)

FOR THE ADOPTION OF ASME CODE CASE N-921, AND 10 CFR 50.55a(y) 1.0 SPECIFIC EXEMPTION REQUEST In accordance with 10 CFR 50.12, "Specific Exemptions," Northern States Power Company, a Minnesota corporation, doing business as Xcel Energy (hereafter "NSPM") requests NRC approval of an exemption from 10 CFR 50.55a(y) and 10 CFR 50.55a(a)(3)(ii), which incorporates by reference Regulatory Guide 1.147, Revision 21 (Reference 1). Table 2 of the regulatory guide, "Conditionally Acceptable Section XI Code Cases," contains a provision limiting adoption of the American Society of Mechanical Engineers (ASME) Code Case N-921, "Alternative 12-yr Inspection Interval Duration Section XI, Division 1," to only at the beginning of an Inservice Inspection (ISI) interval as part of a routine update of the ISI program. NSPM requests an exemption for the Monticello Nuclear Generating Plant (MNGP) ISI Program 6th Interval due to Code Case N-921 not being applied at the beginning of the interval routine update. The MNGP ISI Program 6th Interval started prior to the issuance of Regulatory Guide 1.147, Revision 21. NSPM's exemption request also extends to the definition of Inservice Inspection Interval of 10 CFR 50.55a(y), which defines the ISI interval as 10 years by reference to IWA-2431. This exemption is being submitted as reflected in the Final Rule (Reference 3) noticed in the Federal Register that incorporated Regulatory Guide 1.147, Revision 21, into 10 CFR 50.55a. The exemption is requested for the duration of the MNGP ISI Program 6th Interval.

2.0 BACKGROUND

On July 17, 2024, the NRC issued a final rule that included new approved code cases and update frequencies. The Final Rule became effective on August 16, 2024, and updated 10 CFR 50.55a(a)(3)(ii) to incorporate by reference Regulatory Guide 1.147, Revision 21, into the regulation. Regulatory Guide 1.147, Revision 21, conditionally approved Code Case N-921.

Regulatory Guide 1.147, Revision 21, Table 2, approves the use of Code Case N-921 under four conditions:

(1) The licensees code of record for the ISI program must be the 2017 Edition of Section XI or later, in order to apply this code case.

(2) The code case can only be implemented at the beginning of an ISI interval as part of a routine update of the ISI program.

(3) The code case cannot be used to modify the examination schedules for augmented inspections under 10 CFR 50.55a(g)(6)(ii).

L-MT-25-002 NSPM Enclosure Page 2 of 11 (4) The exceptions of IWB-2411(a), IWC-2411(a), and IWD-2411(a) also apply to Table 1 of the N-921 code case.

As discussed in Reference 3, Regulatory Guide 1.147 Condition (2) for Code Case N-921 was added in response to an anonymous public comment (Reference 4). The specific comment that led to the inclusion of Condition (2) is provided below for reference (Reference 5).

B-6 Code Case N-921 Implementation Comment Summary B-6: A commenter suggested that the NRC add a condition to require implementation of Code Case N-921 at the beginning of an ISI interval. The commenter stated that implementing the code case mid-ISI interval could lead to extra burden for the NRC and the industry. Specifically, existing alternatives would likely need to be reauthorized by the NRC. The commenter suggested that the NRC should add a condition requiring that Code Case N-921 only be implemented at the start of a new interval, to eliminate these requests. The commenter stated that NRCs regulatory analysis did not provide or address the additional costs associated with updating to the code cases mid-interval for licensees submitting new alternative requests. (13-2, 13-3)

NRC Response:

The NRC agrees with the commenter and has added a condition to only allow implementation of Code Case N-921 to occur at the beginning of an ISI interval, rather than allowing implementation during a mid-ISI interval. The NRC agrees that mid-ISI interval implementation of Code Case N-921 would create a significant burden for both the NRC and licensees because of the ongoing schedule for ISI activities and the need to resubmit requests for alternatives authorized based on a 10-year ISI interval. The NRC notes that the ASME BPV Code currently allows a 1-year extension of the 10-year ISI interval with certain conditions, which makes the necessary burden to achieve an extra 1-year ISI interval extension to be of questionable resource value. Licensees wishing to implement Code Case N-921 during a mid-ISI interval should submit an exemption request in accordance with 10 CFR 50.12, Specific exemptions, and should review all NRC-authorized alternative requests to determine whether they need to be resubmitted to the NRC for review and authorization.

As a result of this comment, the NRC added a condition to Regulatory Guide 1.147, Revision 21, to only allow implementation of Code Case N-921 at the beginning of a new ISI interval.

The NRC Final Rule noticed in the Federal Register reiterated the rationale underlying Regulatory Guide 1.147, Table 2, Code Case N-921 Condition (2):

There are complications associated with extending the ISI interval mid-interval. For instance, licensees wanting to extend the ISI interval mid-interval would need to evaluate all NRC-approved alternatives to determine if they should be resubmitted, especially considering that NRC may have granted the alternative assuming a 10-year ISI interval. Further, Code Case N-921 specifies requirements in terms of three 4-year periods, so licensees would need to reconcile their inspection schedules

L-MT-25-002 NSPM Enclosure Page 3 of 11 accordingly. Therefore, this final rule specifies that Code Case N-921 can only be implemented following a routine update of the ISI program (i.e., cannot be implemented mid-interval) and requires the licensees ISI code of record to be the 2017 Edition, or later, of the BPV Code.

In summary, the NRC identified two distinct concerns with allowing mid-cycle implementation of Code Case N-921:

• licensees would need to evaluate all NRC-approved alternatives to determine if they should be resubmitted, and

• licensees would need to reconcile their inspection schedules to conform with the three 4-year periods specified in Code Case N-921.

Additionally, 10 CFR 50.55a(y) was also revised, adding a definition of Inservice Inspection Interval to state the inspection interval described in Article IWA-2432 of ASME BPV Code,Section XI, 1989 Edition with 1991 Addenda through the 2008 Addenda, or Article IWA-2431 of ASME BPV Code,Section XI, 2009 Addenda and later. This definition creates an inconsistency with application of Code Case N-921.

3.0 TECHNICAL JUSTIFICATION OF ACCEPTABILITY The MNGP ISI Program 6th Interval started on June 1, 2023, prior to the incorporation of Regulatory Guide 1.147, Revision 21 into 10 CFR 50.55a. NSPM had intended to use Code Case N-921 once incorporated by reference via the regulatory guide and took specific actions during the interval update to facilitate future adoption. However, addition of Condition (2) after the public comment period prevented NSPM from obtaining the benefit of Code Case N-921.

Implementation of Code Case N-921 will allow NSPM to gain the benefits of the code case for the MNGP ISI Program 6th Interval without any significant burden on the NRC or NSPM.

During the MNGP ISI Program 6th Interval update, NSPM proactively acted based on the information publicly available anticipating implementation of Code Case N-921. This included revision of the period start and end dates to accommodate outage schedules and adjusting examination schedules accordingly while maintaining compliance with periodic distribution requirements.

The exemption requested herein will not apply to the MNGP Containment Inservice Inspection (CISI) program (Metal Containment, IWE).

All other conditions for Regulatory Guide 1.147, Table 2, required for using Code Case N-921 with the MNGP ISI Program 6th Interval are, and will remain, applicable. Specifically, the conditions required for use of Code Case N-921 as specified by Table 2 of Regulatory Guide 1.147, Revision 21, are met for the MNGP ISI Program 6th Interval except for Condition (2).

(1) The licensees code of record for the ISI program must be the 2017 Edition of Section XI or later, in order to apply this code case.

L-MT-25-002 NSPM Enclosure Page 4 of 11 The MNGP ISI Program 6th Interval began on June 1, 2023 using ASME BPV Section XI 2019 Edition as the Code of Record.

Table 1: MNGP ISI Program 6th Interval Plant Program Interval ASME Section XI Code Edition Interval Start Date Current Interval End Date Proposed 12-yr Interval End Date MNGP ISI 6th 2019 Ed.

6/1/2023 5/31/2033 5/31/2035 Note: The MNGP CISI program will remain on a 10-year interval.

(2) This code case can only be implemented at the beginning of an ISI interval as part of a routine update of the ISI program.

The MNGP ISI Program 6th Interval began on June 1, 2023. The first and second inspection periods were established in anticipation of Code Case N-921 authorization and are each 4 years in length; the 3rd Period is currently 2 years.

When planning the 6th interval, the adoption of Code Case N-921 was factored into the interval periods and inspection schedule. As shown in Table 2, the net change to the interval will result in a second refueling outage added to the third inspection period; the first and second inspection periods will be unchanged. The program is currently in the 1st Period and the first refueling outage is scheduled to start in April 2025.

Table 2: MNGP ISI Program 6th Interval Inspection Periods Interval Periods Outages Start Date to End Date Start Date to End Date Outage Numbers 6th ISI Interval 6/1/2023 to 5/31/2033 5/31/2035*

1st 6/1/2023 to 5/31/2027 1R32 Spring 2025 1R33 Spring 2027 2nd 6/1/2027 to 5/31/2031 1R34 Spring 2029 1R35 Spring 2031 3rd 6/1/2031 to 5/31/2033 5/31/2035* #

1R36 Spring 2033 1R37**

Spring 2035 Notes:

• Proposed interval end date for implementation of a 12-year interval via Code Case N-921.

• • Proposed last outage for implementation of a 12-year interval via Code Case N-921.

1. No extension beyond 12-years per IWA-2430(c)(1) as the allowance was used with the MNGP ISI Program 5th interval.

There are only two existing approved 10 CFR 50.55a(z)(1) or (z)(2) requests for the MNGP ISI Program 6th Interval:

I I

L-MT-25-002 NSPM Enclosure Page 5 of 11 (1) RR-017 (Reference 6) was approved by the NRC to for permanent relief from volumetric examination of the reactor pressure vessel (RPV) shell circumferential welds, as required by 10 CFR 50.55a(g) (i.e., by ASME Section Xl, Table IWB-2500-1, Examination Category B-A, Item B1.11, Circumferential Shell Welds) for the term of the renewed operating license. This alternative covered portions of the MNGP ISI program 4th Interval, the entire 5th Interval, and a portion of the 6th Interval. It expires at the end of the MNGP Renewed Facility Operating License on September 8, 2030.

Note that this alternative is identified as RR-001 starting with the 5th ISI interval as reflected in Reference 7. That identification, RR-001, is maintained for this authorized alternative into the 6th ISI interval.

This approved alternative was active prior to the start of the current 6th interval thus would have been active if Code Case N-921 had been adopted at the start of the 6th interval.

(2) In RR-002, NSPM proposed an ISI alternative to the ASME Boiler and Pressure Vessel Code Section XI, 2019 Edition, IWB-2500(f)(8) and IWB-2500(f)(9) for the MNGP ISI 6th Interval that allows reducing the number of volumetric inspections planned for MNGP reactor pressure vessel (RPV) nozzle-to-vessel (NV) welds and nozzle inner blend radius (IR) locations. Specifically, NSPM proposed that the use of IWB-2500(f) be permitted even though the maximum fluence cited in IWB-2500(f)(8) and the number of heatup/cooldown cycles cited in IWB-2500(f)(9) are exceeded during the 6th ISI Interval. (Reference 8). Following a response to additional information (RAI) (Reference 9), NSPM received approval of the proposed alternative (Reference 10).

Both alternatives expire at the end of the period of the MNGP Renewed Facility Operating License on September 8, 2030, in the second inspection period.

Providing an exemption to allow adoption of Code Case N-921 and extending the MNGP ISI 6th Interval from 10 to 12 years will not change the remaining period of applicability for authorized alternatives RR-001 and RR-002. Extension of both of these alternatives beyond the period of the term of the Renewed Facility Operating License into the Subsequent License Renewal term (which includes the second refueling outage of the second inspection period and the entire third inspection period) will require resubmission of alternative requests for both RR-001 and RR-002 independent of this exemption.

Application of ASME Code Case N-921 to the MNGP ISI 6th Interval will have no consequence to either of these active authorized alternatives.

(3) This code case [Code Case N-921] cannot be used to modify the examination schedules for augmented inspections under 10 CFR 50.55a(g)(6)(ii).

L-MT-25-002 NSPM Enclosure Page 6 of 11 The MNGP augmented inspection examination schedules will remain unchanged.

(4) The exceptions of IWB-2411(a), IWC-2411(a), and IWD-2411(a) also apply to Table 1 of this code case.

The exceptions of IWB-2411(a), IWC-2411(a) and IWD-2411(a) will be applied to Table 1 of Code Case N-921 when implemented.

4.0 JUSTIFICATION OF EXEMPTION AND SPECIAL CIRCUMSTANCES 10 CFR 50.12, Specific Exemptions, states that the NRC may grant exemptions from the requirements of the regulations of this part provided three conditions are met. They are:

(1) The exemptions are authorized by law, (2) The exemptions will not present an undue risk to the public health and safety, and (3) The exemptions are consistent with the common defense and security.

NSPM has evaluated the requested exemption for the MNGP against the criteria of 10 CFR 50.12 and determined the criteria are satisfied as described below.

(1) This exemption is authorized by law.

The exemption will allow NSPM to implement ASME Code Case N-921 at MNGP during the current ISI interval. The NRC acknowledged the appropriateness of submitting an exemption in its response to the public comment. Granting of the request does not result in a violation of the Atomic Energy Act of 1954, as amended.

(2) This exemption will not present an undue risk to the public health and safety.

The proposed exemption will allow NSPM to extend the current MNGP ISI 6th Interval Third Period from 2 to 4 years. ISI program activities will not change for the items covered by the two active program approved alternatives, RR-001 and RR-002; all other MNGP ISI activities for the 6th Interval will conform to the conditions of Regulatory Guide 1.147 Table 2 for Code Case N-921 as if adopted at the interval's start. The probability and consequences of postulated accidents are not increased, and an acceptable ISI program schedule is maintained for the MNGP 6th Interval. Therefore, there is no undue risk to public health and safety.

(3) This exemption is consistent with the common defense and security.

This exemption has no relation to security issues; the common defense and security will not be affected by this exemption.

L-MT-25-002 NSPM Enclosure Page 7 of 11 In addition to the three conditions discussed above, 10 CFR 50.12(a)(2) specifies that the NRC will not consider granting an exemption unless special circumstances are present.

(ii), application of the regulation in the particular circumstances would not serve the underlying purpose of the rule or is not necessary to achieve the underlying purpose of the rule.

As outlined above, the NRC expressed concerns that allowing mid-cycle implementation of Code Case N-921 would result in a significant burden and identified two specific concerns underlying this assertion:

• licensees would need to evaluate all NRC-approved alternatives to determine if they should be resubmitted, and

• licensees would need to reconcile their inspection schedules to conform with the three 4-year periods specified in Code Case N-921.

With respect to the need to evaluate previously approved alternates that were based on a 10-year ISI interval, this would not be a significant burden and in fact NSPM has already performed this evaluation. NSPM performed a review, as described in Section 3 above, of all previously authorized alternatives (relief requests) for the MNGP ISI Program 6th Interval and assessed the impact of extending the interval by 2 years to implement Code Case N-921 on the technical basis supporting each alternative. The results of this assessment determined that there is no impact to the technical basis supporting any of the previously approved alternatives.

Regarding the second concern that significant burden would result from licensees needing to reconcile their inspection schedules to conform with the three 4 year periods specified in Code Case N-921, this also does not create any particular challenge. NSPM regularly revises the ISI examination schedule mid-interval. Reasons for revising the ISI examination schedule mid-interval include, but are not limited to, dose, availability of examination equipment and personnel, availability of personnel for required support tasks (e.g. insulation, scaffold, weld preparation), outage schedules, outage duration, changes in operating strategy, etc. Maintaining the ISI examination schedule, including mid-interval changes, is core business for ISI program owners and implementation of Code Case N-921 mid-interval does not result in a significant burden, contrary to the commenters assertion. As previously mentioned, during the most recent ISI interval update, NSPM took specific actions in anticipation of implementation of Code Case N-921 in the new interval. This includes establishing of the period start and end dates and adjusting examination schedules accordingly.

Regarding 10 CFR 50.12(a)(2)(ii), the MNGP ISI program meets the intent of the conditions applicable to ASME Code Case N-921 since it is early in the interval and that the two approved alternatives are not affected by extending the 6th interval to twelve years. Both RR-001 and RR-002 require renewal during the MNGP ISI Program 6th Interval prior to reaching the interval extension period

L-MT-25-002 NSPM Enclosure Page 8 of 11 allowed by Regulatory Guide 1.147 with ASME Code Case N-921. Currently both approved alternatives end during the MNGP ISI 6th Interval 2nd period with the expiration of the MNGP Renewed License, on September 8, 2030. Each of the first two Interval periods are for four years and do not change with the adoption of Code Case N-921.

Therefore, because the concerns identified by the NRC in establishing Condition (2) for Code Case N-921 are not applicable to NSPM or can be easily mitigated, the underlying purpose of the rule would continue to be achieved when allowing implementation of Code Case N-921 during the current MNGP ISI interval, the special circumstance of 10 CFR 50.12(a)(2)(ii) is present.

(iii) Compliance would result in undue hardship or other costs that are significantly in excess of those contemplated when the regulation was adopted, or that are significantly in excess of those incurred by others similarly situated.

The Commission has explained that the application of Criterion iii, undue hardship, is narrow. As the Commission stated in the 1985 rule adopting the current exemption criteria, this special circumstance was intended to provide equitable treatment to applicants or licensees who, because of some unusual circumstance, are affected in a manner different than that of other similarly situated licensees or applicants. (Reference 11) Here, however, NSPM will, in fact, be subjected to an undue hardship as a result of the application of Condition (2) to Code Case N-921. Specifically, limiting NSPM from being able to adopt Code Case N-921 for the MNGP ISI Program 6th Interval would result in inequitable treatment because it would be done on a basis that does not apply to the facility. As explained above, none of the concerns regarding midcycle adoption of Code Case N-921 that underlie Condition (2) are applicable to NSPM or can be easily mitigated. Therefore, it would be fundamentally unfair to preclude NSPM's ability to implement the enhancements that Code Case N-921 permits to the MNGP ISI Program 6th Interval.

Therefore, compliance with Section 50.55a(a)(3)(ii) and the related condition imposed on the implementation of Code Case N-921 would result in undue hardship and thus Special Circumstance 50.12(a)(2)(iii) is present.

(vi) There is present any other material circumstance not considered when the regulation was adopted for which it would be in the public interest to grant an exemption.

There are material circumstances that are present and not considered when the NRC modified 10 CFR 50.55a(a)(3)(ii) and adopted the related Condition (2) for implementation of Code Case N-921. Specifically, the NRC adopted Condition (2) based on a single comment without an opportunity for the industry to provide additional input on whether, in fact, mid-cycle implementation of Code Case N-921 would result in the significant burden asserted. Had such input been provided, it would have been understood that a mid-cycle implementation of

L-MT-25-002 NSPM Enclosure Page 9 of 11 Code Case N-921 would not create a significant burden. As explained in this exemption request, the concerns underlying this condition do not exist for NSPM with the MNGP ISI Program 6th Interval.

Therefore, there are material circumstances that are present and not considered when the NRC modified 10 CFR 50.55a(a)(3)(ii) and adopted the related Condition (2) for implementation of Code Case N-921 and Special Circumstance 50.12(a)(2)(vi) is present.

5.0 ENVIRONMENTAL ASSESSMENT NSPM has determined that the requested exemption meets the categorical exclusion of 10 CFR 51.22(c)(25). The following information is provided in support of a determination that no environmental assessment or an environmental impact statement is required in accordance with 10 CFR 51.22(b) and 10 CFR 51.22(c)(9) to grant the requested exemption.

The exemption does not make any changes to the facility or operating procedures and does not:

a) Involve a significant hazards consideration under the standards set forth in 10 CFR 50.92(c), in that it does not:

• Alter the design, function or operation of any plant equipment. Therefore, granting this exemption will not increase the probability or consequence of any previously evaluated accident.

• Create any new accident initiators. Therefore, granting this exemption does not create the possibility of a new or different kind of accident from any accident previously evaluated.

• Exceed or alter a design basis or safety limit. Therefore, granting this exemption does not involve a significant reduction in a margin of safety.

Therefore, a finding of no significant hazards considerations is justified.

b) Involve any changes that would introduce any change to effluent types, affect any plant radiological or non-radiological effluent release quantities, or affect any effluent release paths or the functionality of any design or operational features that are credited with controlling the release of effluents during plant operation. Therefore, it is concluded that the proposed exemption does not involve a significant change in the types or a significant increase in the amounts of any effluents that may be released offsite.

c) Affect any plant radiation zones, nor change any controls required under 10 CFR Part 20 that preclude a significant increase in occupational radiation exposure.

Therefore, it is concluded that the proposed exemption does not involve a significant increase in individual or cumulative occupational radiation exposure.

L-MT-25-002 NSPM Enclosure Page 10 of 11 d) Involve any facility changes or change any construction activities. Therefore, there is no significant construction impact.

e) Alter the design, function, or operation of any plant equipment. Therefore, there is no significant increase in the potential for or consequences from radiological accidents.

Accordingly, the proposed exemption meets the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(25). Pursuant to 10 CFR 51.22(b), no environmental impact statement or environmental assessment need be prepared in connection with the issuance of this exemption.

6.0 CONCLUSION

Based on current ISI program examination and testing requirements, the exemption requested will allow NSPM to better levelize distribution of the remaining examinations and tests across future outages and inspection periods within the 12-year ISI interval while still meeting the underlying purpose of the rule. NSPM will continue to meet the ASME Section XI requirements to distribute examinations among the three inspection periods. The added flexibility of Code Case N-921 allows NSPM to better align periodic examinations and tests with scheduled outages and maintenance work windows, while ensuring a continuous stream of examination data throughout the remainder of the extended ISI interval.

NSPM considers that this exemption request is in accordance with the criteria of 10 CFR 50.12. Specifically, the requested exemption is authorized by law, will not present an undue risk to the public health and safety, is consistent with the common defense and security, and special circumstances are present.

7.0 REFERENCES

1) Regulatory Guide 1.147, Inservice Inspection Code Case Acceptability, ASME Section XI, Division 1, Revision 21 (ADAMS Accession No. ML23291A003)

2) American Society of Mechanical Engineer's (ASME), Boiler and Pressure Vessel Code,Section XI, Code Case N-921, "Alternative 12-yr Inspection Interval Duration Section XI, Division 1"

3) Federal Register Volume 89, No. 137, page 58039, "American Society of Mechanical Engineers Code Cases and Update Frequency - Final Rule," published July 17, 2024 (ADAMS Accession No. ML23291A338)

4) Public Submission comment on American Society of Mechanical Engineers Code Cases and Update Frequency dated June 14, 2023 (ADAMS Accession No. ML23235A158)

L-MT-25-002 NSPM Enclosure Page 11 of 11

5) NRC Responses to Public Comments. Final Rule: American Society of Mechanical Engineers Code Cases and Update Frequency, dated March 2024 (ADAMS Accession No. ML23291A328)

6) NRC letter to NSPM, "Monticello Nuclear Generation Plant (MNGP) - Request for Relief No. 17 Regarding Examination of Reactor Pressure Vessel Shell Circumferential Welds," dated February 8, 2011 (ADAMS Accession No. ML110200700)

7) NSPM letter to NRC, "Fifth Ten-Year Inservice Inspection Plan," dated February 28, 2012 (ADAMS Accession No. ML12060A298)

8) NSPM submission to NRC, "10 CFR 50.55a Request Associated with the Monticello Sixth Inservice Inspection (ISI) Interval, RR-002 (L-MT-23-024)," dated July 20, 2023 (ADAMS Accession No. ML23193A799)

9) NSPM letter to NRC, "Response to NRC Request for Additional Information on Proposed Inservice Inspection Alternative RR-002 for the Sixth Ten-Year ISI Interval,"

dated February 15, 2024 (ADAMS Accession No. ML24046A132)

10) NRC letter to NSPM, "Monticello Nuclear Generating Plant - Authorization and Safety Evaluation for 10 CFR 50.55a(z)(1) Inservice Inspection Alternative Request No.

RR-002," dated July 2, 2024 (ADAMS Accession No. ML24138A121)

11) Federal Register Volume 50, No. 239, page 50764, "Specific Exemptions; Clarification of Standards," published December 12, 1985