0CAN022502, Supplement to Response to Request for Additional Information - Proposed Alternatives ANO1-ISI-24-01 and ANO2-ISI-24-01 for Examinations of Steam Generator Pressure-Retaining Welds and Full Penetration Welded Nozzles
| ML25051A292 | |
| Person / Time | |
|---|---|
| Site: | Arkansas Nuclear  |
| Issue date: | 02/20/2025 |
| From: | Couture P Entergy Operations |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| 0CAN022502 | |
| Download: ML25051A292 (1) | |
Text
Entergy Operations, Inc., 1340 Echelon Parkway, Jackson, MS 39213 0CAN022502 10 CFR 50.55a February 20, 2025 ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, DC 20555-0001
Subject:
Supplement to Response to Request for Additional Information - Proposed Alternatives ANO1-ISI-24-01 and ANO2-ISI-24-01 for Examinations of Steam Generator Pressure-Retaining Welds and Full Penetration Welded Nozzles Arkansas Nuclear One - Units 1 and 2 NRC Docket Nos. 50-313 and 50-368 Renewed Facility Operating License Nos. DPR-51 and NPF-6
References:
- 1. Entergy letter to NRC, "Proposed Alternatives ANO1-ISI-24-01 and ANO2-ISI-24-01 for Examinations of Steam Generator Pressure-Retaining Welds and Full Penetration Welded Nozzle," (ADAMS Accession Number ML24158A389, (0CAN062402), dated June 6, 2024
- 2. Entergy letter to NRC, "Response to Request for Additional Information -
Proposed Alternatives for Examinations of SG Pressure Retaining Welds and Full Penetration Welded Nozzles," (ADAMS Accession Number ML24290A098), (0CAN102401), dated October 16, 2024
- 3. "Topics of Discussion - Proposed Alternatives for Examinations of SG Pressure Retaining Welds and Full Penetration Welded Nozzles", (ADAMS Accession Number ML25003A039), dated January 28, 2025 In accordance with 10 CFR 50.55a(z)(1), Entergy Operations, Inc. (Entergy), requested Nuclear Regulatory Commission (NRC) approval of proposed alternatives for Arkansas Nuclear One, Units 1 and 2 (ANO-1 and -2) (Reference 1). Specifically, the proposed alternatives are to defer the inservice inspection (ISI) examinations for select examination categories and item numbers for the steam generators (SG) at ANO-1 and ANO-2 from the current American Society of Mechanical Engineers (ASME) Code,Section XI 10-year requirements to the end of licensed operating life, which is scheduled to end on May 20, 2034, and July 17, 2038, respectively.
Phil Couture Senior Manager Fleet Regulatory Assurance - Licensing Tel 601-368-5102
0CAN022502 Page 2 of 2 Entergy responded to a Request for Additional Information (RAI) from the NRC (Reference 2).
The NRC requested a public meeting to discuss Reference 2. The topics of discussion are provided in Reference 3.
Based on the discussion, Entergy is supplementing the response provided in Reference 2. The Enclosure to this letter provides Entergy's supplemental response to the RAI.
This letter contains no new regulatory commitments.
If there are any questions or if additional information is needed, please contact Riley Keele, Manager, Regulatory Assurance, Arkansas Nuclear One, at 479-858-7826.
Respectfully, Phil Couture PC/rwc
Enclosure:
Supplement to Response to Request for Additional Information cc:
NRC Region IV Regional Administrator NRC Senior Resident Inspector - Arkansas Nuclear One NRC Project Manager - Arkansas Nuclear One Digitally signed by Philip Couture DN: cn=Philip Couture, c=US, o=Entergy, ou=Regulatory Assurance, email=pcoutur@entergy.com Date: 2025.02.20 14:12:47 -06'00' Philip Couture
ENCLOSURE 0CAN022502 SUPPLEMENT TO RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION
0CAN022502 Enclosure Page 1 of 9 SUPPLEMENT TO RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION BACKGROUND By letter dated June 6, 2024 (Agencywide Documents Access and Management System Accession No. ML24158A389), Entergy Operations, Inc. (Entergy, the licensee) requested Nuclear Regulatory Commission (NRC) approval of proposed alternatives for Arkansas Nuclear One, Units 1 and 2 (ANO-1 and ANO-2, respectively). Alternative Requests ANO1-ISI-24-01 and ANO2-ISI-24-01 are to defer the inservice inspection (ISI) examinations for select examination categories and item numbers for the steam generators (SG) at ANO-1 and ANO-2 from the current inspection requirements of the American Society of Mechanical Engineers (ASME) Code,Section XI to the end of operating licenses.
By [[letter::0CAN102401, Response to Request for Additional Information - Arkansas Nuclear One – Units 1 and 2, Proposed Alternatives ANO1-ISI-24-01 and ANO2-ISI-24-01 for Examinations of Steam Generator Pressure-Retaining Welds and Full Penetration Welded Nozzle|letter dated October 16, 2024]] (ML24290A098), the licensee responded to NRC Request for Additional Information (RAI).
Below are topics of discussion regarding the licensees supplemental information dated October 16, 2024.
REGULATORY BASIS The SG pressure-retaining welds and nozzles are ASME Code Class 1 and Class 2 components, with inservice inspections (ISIs) performed in accordance with the applicable edition of Section XI, "Rules for Inservice Inspection of Nuclear Power Plant Components," of the ASME Code, as required by 10 CFR 50.55a(g).
The regulations in 10 CFR 50.55a(g)(4) state, in part, components that are classified as ASME Code Class 1, 2, and 3 must meet the requirements, except the design and access provisions and the preservice examination requirements, set forth in the ASME Code,Section XI, to the extent practical within the limitations of design, geometry, and materials of construction of the components.
The regulations in 10 CFR 50.55a(z) state, in part, that alternatives to the requirements in paragraphs (b) through (h) of 10 CFR 50.55a may be used when authorized by the NRC if the licensee demonstrates that: (1) the proposed alternative would provide an acceptable level of quality and safety, or (2) compliance with the specified requirements would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety.
DISCUSSION TOPIC 1 In its response to RAI Question 2(a), in [[letter::0CAN102401, Response to Request for Additional Information - Arkansas Nuclear One – Units 1 and 2, Proposed Alternatives ANO1-ISI-24-01 and ANO2-ISI-24-01 for Examinations of Steam Generator Pressure-Retaining Welds and Full Penetration Welded Nozzle|letter dated October 16, 2024]], the licensee proposed a performance monitoring plan for the requested alternative for ANO-1 and ANO-2 that includes crediting inspections at Waterford. The licensee proposed inspection sample is not sufficient to justify the requested alternative because the number of proposed inspections would be less than 25% of the examinations required to be conducted over the length of the requested alternatives at all units. In its RAI response, the licensee stated that its performance monitoring
0CAN022502 Enclosure Page 2 of 9 plan will examine 6 of 15 components totaling 40% of the entire population of the welds of interest. The staff noted that the licensees approach is not consistent with the staffs position for performance monitoring plans. The staffs position is that the performance monitoring plan (i.e., examined welds) needs to be linked and converted to the SG Equivalent as described in the approved alternative requests for other nuclear plants that result in inspections of at least 25% of SG welds. The number of welds that are proposed to be examined and the required number of welds to be examined for the numbers of the intervals should have been converted to the SG Equivalent. Based on the staff calculation, the proposed welds to be examined are less than 25% of the required sample population. The staffs position on performance monitoring was discussed during a January 30, 2023, public meeting (meeting summary in ML23033A666 and presentation slides in ML23033A667). The examples of an adequate inspection sample size based on whole components (i.e., whole SGs) for similar alternative requests that the staff has approved in the past are documented in NRC safety evaluations for Duke Energy and Constellation fleet submittals in ML23256A088 and ML24179A326, respectively.
The staff determined that the licensee needs to provide a technical justification describing the minimum sample size, utilizing calculations of SG Equivalents according to the staff position, or other methodology as least as conservative as the staff position, in the proposed performance monitoring plan that is necessary to provide a 25% or greater sampling. That justification should include a description of how the sample size is consistent with - or if using a different methodology, at least as conservative as - the documented staff position for acceptable levels of performance monitoring demonstrated by the precedents previously provided, as noted above.
Response to DISCUSSION TOPIC 1 The performance monitoring (PM) plan for ANO-1 and ANO-2 begins with the ongoing 5th interval inspections. The PM plan for Waterford begins with the ongoing 4th interval inspections.
Table 1 below provides the number of Class 1 and Class 2 SG components inspected in the 5th interval at ANO-1 and ANO-2 and the 4th interval at Waterford, broken down by ASME Item Number. Table 1 also provides the number of components to be examined in the 6th interval inspections at ANO-1 and ANO-2 as well as in the 5th and 6th interval inspections at Waterford as part of the PM plan proposed by Entergy.
0CAN022502 Enclosure Page 3 of 9 Table 1. PM Examinations at ANO-1, ANO-2 and Waterford ASME Category ASME Item Number ANO-1 Babcock &
Wilcox (B&W)
ANO-2 Combustion Engineering (CE)
Waterford (CE)
Current 5th Interval 6th Interval Current 5th Interval 6th Interval Current 4th Interval 5th and 6th Intervals B-B B2.31 2
0 Not applicable (N/A) per design N/A per design N/A per design N/A per design B-B B2.40 2
0 0
0 0
1 B-D B3.130 N/A per design N/A per design 0
2 N/A per design N/A per design C-A C1.20 N/A per design N/A per design 0
0 0
1 C-A C1.30 1
0 0
0 1
1 C-B C2.21 Not Selected 0
0 0
0 1
C-B C2.22 1
0 0
0 0
1 Total Number of PM Exams 6
0 0
2 1
5 ASME Code Required Exams 10 10 11 11 5
5 Table 2 shows the determination of the SG Equivalent examinations at all three units using an approach similar to that used by the NRC in the Duke and Constellation Safety Evaluations (ML23256A088 and ML24179A326, respectively). The ANO-2 SG has 8 components per SG.
The code requires 8 exams on 1 SG and 3 exams on the other SG (8/8 + 3/8 = 1.375).
Table 2. ASME Code Required SGs for ANO-1, ANO-2 and Waterford Plant Unit(s)
= Unit(s) x Intervals ANO-1 1
1 2
(5th and 6th) 2 ANO-2 1
1.375 2
(5th and 6th) 2.75 Waterford 1
1 3
(4th, 5th, and 6th) 3 Through binomial statistics and Monte Carlo methods, the NRC staff determined that a 25%
sample of the ASME Code required number of SGs would be an adequate sample size for PM purposes over the subject alternative period. Table 3 shows the determination of this sample size for the three units:
0CAN022502 Enclosure Page 4 of 9 Table 3. Required SG Equivalent Examinations Based on 25% Sampling for ANO-1, ANO-2 and Waterford Plant Required SG Equivalent Examinations
= 0.25 x (ASME Code Required SGs from Table 2)
ANO-1 0.50 ANO-2 0.69 Waterford 0.75 Table 4 shows the number of PM SG Equivalent examinations for the three units.
Table 4. PM SG Equivalent Exams for ANO-1, ANO-2 and Waterford Plant ASME Code Required Examinations PM Examinations (From Table 1)
= PM Examinations / ASME Code Required Examinations ANO-1 10 6
0.60 ANO-2 11 2
0.18 Waterford 5
6 1.20 Table 5 provides the PM SG Equivalent examinations compared to the required SG Equivalent examinations for various scenarios.
Table 5. PM and Required SG Equivalent Exams for Various Cases Case PM SG Equivalent Examinations (from Table 4)
Required SG Equivalent Examinations Based on 25% Sampling (from Table 3)
ANO-1 (only) 0.60 0.50 ANO-2 (only) 0.18 0.69 Waterford (only) 1.20 0.75 ANO-2 and Waterford 1.38 1.44 All 3 Units 1.98 1.94 It can be seen from Table 5 that by considering the Entergy fleet approach, the PM SG Equivalent examinations exceed those required by the binomial distribution 25% sampling criterion and will result in inspections of at least 25% of SG welds.
0CAN022502 Enclosure Page 5 of 9 DISCUSSION TOPIC 2 In its response to RAI Question 2(a) dated October 16, 2024, the licensee proposed to use the SG weld examinations at Waterford Unit 3 as part of the performance monitoring plan for Alternative Requests ANO1-ISI-24-01 and ANO2-ISI-24-01. By letter dated March 18, 2024, (ML24078A376), the licensee submitted alternative request WF3-RR-24-02 for SG weld examination at Waterford. By letter dated September 24, 2024 (ML24268A296), the licensee stated that it plans to examine a total of five SG welds and nozzle inner radii (NIR) at Waterford during the fifth and sixth ISI intervals. The NRC noted that the Waterford SG examination plan is not part of the original ANO alternative request submittal. The Waterford and ANO alternative requests are reviewed and decided separately by the staff.
The staff determined that the licensee needs to provide a description of the SG examination plans at ANO-1 and ANO-2 should, for any reason, the referenced Waterford examinations do not occur as planned or the Waterford examination information is not available.
Response to DISCUSSION TOPIC 2 As can be seen in Table 6, examinations have been completed on six SG components during the ongoing 5th interval at ANO-1. No examinations have been performed during the ongoing 5th interval at ANO-2. The following contingency plan has been prepared in the event the fleet approach in Discussion Topic 1 is not approved. Examinations of seven components will be selected for ANO-2 during the 5th and 6th intervals.
0CAN022502 Enclosure Page 6 of 9 Table 6. Contingency PM Examinations at ANO-1 and ANO-2 ASME Category ASME Item Number ANO-1 (B&W)
ANO-2 (CE)
Current 5th Interval 6th Interval Current 5th Interval 6th Interval B-B B2.31 2
0 N/A per design N/A per design B-B B2.40 2
0 0
1 B-D B3.130 N/A per design N/A per design 0
2 C-A C1.20 N/A per design N/A per design 0
1 C-A C1.30 1
0 0
1 C-B C2.21 Not Selected 0
0 1
C-B C2.22 1
0 0
1 Total Number of PM Exams 6
0 0
7 ASME Code Required Exams 10 10 11 11 Table 7 shows the determination of the SG Equivalent examinations at ANO-1 and ANO-2 using an approach similar to that used by the NRC in ML23256A088 and ML24179A326.
Table 7. ASME Code Required SGs for ANO-1 and ANO-2 Plant Unit(s)
= Unit(s) x Intervals ANO-1 1
1 2
(5th and 6th) 2 ANO-2 1
1.375 2
(5th and 6th) 2.75 Through binomial statistics and Monte Carlo methods, the NRC staff determined that a 25%
sample of the ASME Code required number of SGs would be an adequate sample size for PM purposes over the subject alternative period. Table 8 shows the determination of this sample size for both units:
0CAN022502 Enclosure Page 7 of 9 Table 8. Required SG Equivalent Examinations Based on 25% Sampling for ANO-1 and ANO-2 Plant Required SG Equivalent Examinations
= 0.25 x (ASME Code Required SGs from Table 7)
ANO-1 0.50 ANO-2 0.69 Table 9 shows the number of PM SG Equivalent exams for ANO-1 and ANO-2.
Table 9. PM SG Equivalent Examinations for ANO-1 and ANO-2 Plant ASME Code Required Examinations PM Examinations (From Table 6)
= PM Exams/ASME Code Required Examinations ANO-1 10 6
0.60 ANO-2 11 7
0.64 Table 10 provides the PM SG Equivalent examinations compared to the required SG Equivalent examinations for various scenarios.
Table 10. PM and Required SG Equivalent Examinations for ANO-1 and ANO-2 Case PM SG Equivalent Examinations (from Table 9)
Required SG Equivalent Examinations Based on 25%
Sampling (from Table 8)
ANO-1 (only) 0.60 0.50 ANO-2 (only) 0.64 0.69 ANO-1 and ANO-2 1.24 1.19 It can be seen from Table 10 that by considering ANO-1 and ANO-2 together, and without crediting examinations performed at Waterford, the PM SG Equivalent examinations exceed those required by the binomial distribution 25% sampling criterion and will result in inspections of at least 25% of SG welds.
0CAN022502 Enclosure Page 8 of 9 DISCUSSION TOPIC 3 In its response to RAI Questions 2(c) and 2(d) dated October 16, 2024, the licensee stated that additional examinations will be conducted according to the rules of the ASME Code,Section XI, IWB-2430. These Section XI paragraphs provide rules regarding selecting additional examination locations during the same outage and for the reactor unit when/where the flaw was discovered. However, the licensees response does not address potentially expanding examination scope beyond the reactor unit where the original flaw is found. If unacceptable flaws were detected during examinations at Waterford, which the licensee proposes to credit for the ANO alternative request, the underlying premise that degradation is appropriately modeled in the EPRI reports as referenced in the alternative request cannot be verified for ANO without further information. Scope expansion is an important part of demonstrating an acceptable level of quality and safety to support the licensees alternative requests because scope expansion establishes extent of condition for any unexpected degradation discovered during the proposed alternative examination schedules. Examples of previously approved inspection sample expansion scope beyond the reactor unit can be found in the following references (1). Duke Energy response to staffs RAI-1 (c) and (d) in its letter dated July 20, 2023 (ML23201A140),
(2) NRC safety evaluation for Duke Energy fleet (ML23256A088), (3). NRC safety evaluation for Vogtle nuclear plant (ML20352A155), and (4) NRC safety evaluation for Constellation fleet (ML24179A326).
The staff determined that the licensee needs to provide clarification regarding whether it intends to perform additional examinations of the subject SG welds and NIR beyond the reactor unit where unexpected degradation was found as part of the proposed alternative examination schedules. If the licensee does intend to expand scope to other reactor units, the licensee needs to describe the timing and number of additional examinations. If the licensee does not intend to expand scope of inspection to other reactor units, the staff determined that the licensee needs to provide justification on how the proposed alternative requests address extent of condition for unexpected degradation.
Response to DISCUSSION TOPIC 3 If a flaw is found as a part of any PM plan provided in this submittal, Entergy will expand scope to the other units for the Category and Item Number for which the flaw was found as applicable per plant design within the first to second scheduled refueling outages of discovery of the indication. Scope expansion will be performed in accordance with IWB-2430, IWB-3500, IWC-2430 and IWC-3500 as applicable.
DISCUSSION TOPIC 4 In its response to RAI Questions 2(c) and 2(d) dated October 16, 2024, the licensee stated that it will address indications that exceed the applicable ASME Code,Section XI acceptance standards of IWB-3500, and the number of additional examinations will be the number required by ASME Section XI, IWB-2430. The licensee also proposed to include the inspection of SG components at Waterford to support the ANO proposed alternative which include Class 2 components. The NRC staff noted that IWB-2430 and IWB-3500 are applicable to Class 1 components only. The ASME Code,Section XI, IWC-2430 and IWC-3500 are applicable to Class 2 components.
0CAN022502 Enclosure Page 9 of 9 The staff determined that the licensee needs to confirm that it will follow the requirements of the ASME Code,Section XI, IWC-2430 and IWC-3500 for the examination of the SG welds and nozzle inner radii that are ASME Class 2 components.
Response to DISCUSSION TOPIC 4 Entergy confirms that the requirements of the ASME Code,Section XI, IWC-2430 and IWC-3500 for the examination of the SG welds and nozzle inner radii that are ASME Class 2 components will be followed.