W3F1-2024-0038, Response to Request for Additional Information - Proposed Alternative WF3-RR-24-01 for Examinations of Pressurizer Circumferential and Longitudinal Shell-to-Head Welds and Nozzle-to-Vessel Welds

Response to Request for Additional Information - Proposed Alternative WF3-RR-24-01 for Examinations of Pressurizer Circumferential and Longitudinal Shell-to-Head Welds and Nozzle-to-Vessel Welds

ML24268A295
Person / Time
Site:	Waterford
Issue date:	09/24/2024
From:	Pyle S Entergy Operations
To:	Office of Nuclear Reactor Regulation, Document Control Desk
References
W3F1-2024-0038
Download: ML24268A295 (1)

Text

Stephenie Pyle Director Regulatory Compliance 601-368-5516

Entergy Operations, Inc., 1340 Echelon Parkway, Jackson, MS 39213 W3F1-2024-0038 10 CFR 50.55a September 24, 2024 ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, DC 20555-0001

Subject:

Response to Request for Additional Information - Proposed Alternative WF3-RR-24-01 for Examinations of Pressurizer Circumferential and Longitudinal Shell-to-Head Welds and Nozzle-to-Vessel Welds Waterford Steam Electric Station, Unit 3 NRC Docket No. 50-382 Renewed Facility Operating License No. NPF-38 In accordance with 10 CFR 50.55a(z)(1), Entergy Operations, Inc. (Entergy) requested Nuclear Regulatory Commission (NRC) approval of a proposed alternative for Waterford Steam Electric Station, Unit 3 (WF3) (Reference1). Specifically, the proposed alternative concerns Class 1, Examination Category B-B, Pressure-Retaining Welds in Vessels Other Than Reactor Vessels, Item Number B2.11 - Pressurizer, Shell-to-Head Welds, Circumferential, and B2.12 -

Pressurizer, Shell-to-Head Welds, Longitudinal, and Class 1, Examination Category B-D, Full Penetration Welded Nozzles in Vessels, Item Number B3.110 - Pressurizer, nozzle-to-vessel welds.

Entergy received a Request for Additional Information (RAI) from the NRC (Reference 2). The Enclosure to this letter provides Entergy's response to the RAI.

This letter contains no new regulatory commitments.

W3F1-2024-0038 Page 2 of 2 Should you have any questions or require additional information, please contact Phil Couture at 601-368-5102.

Respectfully, Stephenie Pyle SP/chm

Enclosure:

Response to Request for Information

References:

1) Entergy letter to NRC, "Proposed Alternative WF3-RR-24-01 for Examinations of Pressurizer Circumferential and Longitudinal Shell-to-Head Welds and Nozzle-to-Vessel Welds," ML24078A374, dated March 18, 2024

2) NRC email to Entergy, "Request for Additional Information Proposed Alternative WF3-RR-24-01 Examinations of Pressurizer Welds Waterford Steam Electric Station, Unit 3, Entergy Operations, Inc.

Docket No. 50-382," ML24236A140, dated August 26, 2024 cc:

NRC Region IV Regional Administrator NRC Senior Resident Inspector - WF3 NRC Project Manager - WF3 Digitally signed by Stephenie Pyle DN: cn=Stephenie Pyle, c=US, o=Entergy, ou=Director, Fleet Regulatory Assurance, email=spyle@entergy.com Date: 2024.09.24 11:02:20 -05'00' Stephenie Pyle

Enclosure W3F1-2024-0038 Response to Request for Information

W3F1-2024-0038 Enclosure Page 1 of 6 TABLE OF CONTENTS

1.0 BACKGROUND

................................................................................................................. 2 2.0 REGULATORY BASIS....................................................................................................... 2 3.0 ISSUES.............................................................................................................................. 2 4.0 NRC REQUEST AND ENTERGY RESPONSE................................................................. 3 4.1 Request for Additional Information - 1........................................................................... 3 4.1.1 NRC Request.......................................................................................................... 3 4.1.2 Entergy Response................................................................................................... 3 4.2 Request for Additional Information - 2........................................................................... 4 4.2.1 NRC Request.......................................................................................................... 4 4.2.2 Entergy Response................................................................................................... 4 4.3 Request for Additional Information - 3........................................................................... 5 4.3.1 NRC Request.......................................................................................................... 5 4.3.2 Entergy Response................................................................................................... 5 4.4 Request for Additional Information - 4........................................................................... 5 4.4.1 NRC Request.......................................................................................................... 5 4.4.2 Entergy Response................................................................................................... 5

5.0 REFERENCES

................................................................................................................... 6

W3F1-2024-0038 Enclosure Page 2 of 6 RESPONSE TO REQUEST FOR INFORMATION

1.0 BACKGROUND

By letter dated March 18, 2024 (Agencywide Document Access and Management System Accession Number ML24078A374), Entergy Operations, Inc. (Entergy and the licensee) submitted to the United States Nuclear Regulatory Commission (NRC), a proposed alternative to the inservice inspection (ISI) requirements of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code),Section XI, for the examination of pressurizer (PZR) welds at Waterford Steam Electric Station, Unit 3 (WF3).

Specifically, pursuant to Title 10 of the Code of Federal Regulations, Part 50, Section 55a, Paragraph (z)(1) (10 CFR 50.55a(z)(1)), the licensee is proposing to defer the ISI examinations for the listed PZR welds at WF3 from the current ASME Code,Section XI, 10-year requirement to the end of currently licensed operating life, which is scheduled to end on December 18, 2044 as discussed in Proposed Alternative WF3-RR-24-01. The licensee referred to the results of the probabilistic fracture mechanics (PFM) analyses in the following Electric Power Research Institute (EPRI) nonproprietary report as the primary basis for the deferral of the ISI examinations:

EPRI Technical Report 3002015905, "Technical Bases for Inspection Requirements for PWR [Pressurized Water Reactor] Pressurizer Head, Shell-to-Head, and Nozzle-to-Vessel Welds," 2019 (hereinafter referred to as "EPRI report 15905," ML21021A271).

To complete its review, the NRC staff requests for the additional information as discussed below.

2.0 REGULATORY BASIS The NRC has established requirements in 10 CFR Part 50 to protect the structural integrity of structures and components in nuclear power plants. Among these requirements are the ISI requirements of Section XI of the ASME Code incorporated by reference in 10 CFR 50.55a to ensure that adequate structural integrity of PZR vessels (including their welds) is maintained through the service life of the vessels. Therefore, the regulatory basis for the following request for additional information (RAl) has to do with demonstrating that the proposed alternative ISI requirements would ensure structural integrity of the PZR welds of WF3, and thereby would provide an acceptable level of quality and safety per 10 CFR 50. 55a(z)(1) for the welds.

3.0 ISSUES The licensee referenced probabilistic and deterministic analyses in the above EPRI report to estimate potential fatigue crack growth in the subject PZR welds and to justify application of these analyses to the proposed examination deferral for the welds. The licensee presented plant-specific information to demonstrate that the referenced analyses in the EPRI report would bound the subject PZR welds, including the ISI history of the welds.

Leveraging PFM analyses to define the basis for risk-informing inspection requirements requires knowledge of both the current and future behavior of the material degradation and the associated uncertainties applicable to the subject PZR welds. Confidence in the results of these analyses hinges on the assurance that the PFM model adequately represents, and will continue

W3F1-2024-0038 Enclosure Page 3 of 6 to represent, the degradation behavior in the subject PZR welds. The NRC staff has determined that, when considering proposed deferral of examinations, adequate performance monitoring through inspections is needed to ensure that the assumptions of the PFM model remain valid, and that novel or unexpected degradation is detected and dispositioned in a timely fashion. Further, the staff has communicated concepts that licensees can implement on a fleet-wide basis to develop a performance monitoring plan and bolster the technical basis for alternative requests (see slide packages dated January 30, 2023, and April 27, 2023, at ML23033A667 and ML23114A034, respectively).

In Section 5.1.6 of the submittal, the licensee stated that PZR welds05-007 and 05-008 were last examined during the third 10-year ASME Section XI interval and proposed performing the required ASME Code,Section XI examinations prior to the end of currently licensed operating life, which is scheduled to end on December 18, 2044. To provide additional defense in depth to the alternative request, the licensee stated they will adopt a performance monitoring plan during the requested deferral period. Given this inspection scenario, the WF3 inspection history in Attachment 1 to the submittal, and the licensee's proposed extended examination intervals, the staff noted that all subject PZR welds will be in operation for more than 20 years past their last inspection. This inspection plan would not meet the threshold the staff have adopted for performance monitoring because 20 years is too long without validating data.

4.0 NRC REQUEST AND ENTERGY RESPONSE 4.1 Request for Additional Information - 1 4.1.1 NRC Request Describe the performance monitoring that will be implemented with this proposed alternative to ensure that the PFM model adequately represents, and will continue to represent, the degradation behavior in the subject components commensurate with the duration of the requested alternative.

4.1.2 Entergy Response From WF3-RR-24-01, Section 5.1.6 (Reference 1), WF3 requested to utilize a performance monitoring plan for the following components: 05-007,05-008 as these exams have not been completed in the current 4th inspection interval.05-013 has been examined in the current interval and will be inspected in the future as shown below for the B-D, B3.110 sample.

This monitoring plan will be implemented as stated in the Table 1 below. Table 1 shows that three welds out of total population of eleven welds (27% of the required ASME section examinations as identified in Reference 1) for WF3 pressurizer will be inspected in 20 years or less. This is slightly more than the 25% required by the NRC using the binomial distribution model in ML23033A667 (Reference 6) and ML23114A034 (Reference 7) for adequate performance monitoring.

W3F1-2024-0038 Enclosure Page 4 of 6 Table 1 - Inspection History - Monitoring Plan Item No.

Comp ID Exam Date Interval/Period/Outage Future Exam Schedule Outage Current Schedule Approximate Years Between Exams B2.11 05-002 1/12/2019 4th / 1st / RF22 6th Int / 3rd Per 2046 27 B2.11 05-008 10/28/2012 3rd / 2nd / RF18 5th Int /2nd Per 2032 19.5 B2.12 05-003 1/12/2019 4th / 1st / RF22 6th Int / 3rd Per 2046 27 B2.12 05-007 10/28/2012 3rd / 2nd / RF18 5th Int / 2nd Per 2032 19.5 B3.110 05-009 1/13/2019 4th / 1st / RF22 6th Int / 1st Per 2046 27 B3.110 05-010 1/13/2019 4th / 1st / RF22 6th Int / 1st Per 2046 27 B3.110 05-011 1/11/2019 4th / 1st / RF22 6th Int / 1st Per 2046 27 B3.110 05-012 1/11/2019 4th / 1st / RF22 6th Int/ 1st Per 2046 27 B3.110 05-013 1/11/2019 4th / 1st / RF22 6th Int / 1st Per 2039 20 As shown in the Inspection History Table above, a significant number of 4th Interval examinations have been completed at WF3. These 4th Interval examinations utilized approved ASME Section XI methodology.

4.2 Request for Additional Information - 2 4.2.1 NRC Request Explain how this performance monitoring will provide, over the extended examination interval, (1) direct evidence of the presence and extent of degradation, (2) validation and confirmation of the continued adequacy of the PFM model; and (3) timely detection of novel or unexpected degradation.

4.2.2 Entergy Response

1) The performance monitoring plan provided above includes sampled inspections using ASME Section XI exam methods that will provide direct evidence of the presence and extent of any degradation over the extended examination interval for these welds.

2) The WF3 operating history is validation and confirmation of the conservative nature of the PFM and deterministic fracture mechanics (DFM) models used in the EPRI Technical Reports 3002015906 (Reference 3) and 3002014590 (Reference 4) which were referenced in WF3-RR-24-02 (Reference 5). This also shows that the models will predict future behavior conservatively. The proposed performance monitoring plan includes sampling of examinations across the remainder of the WF3 current operating license.

3) The performance monitoring schedule described above will provide timely detection of any novel or unexpected degradation in these components.

W3F1-2024-0038 Enclosure Page 5 of 6 4.3 Request for Additional Information - 3 4.3.1 NRC Request If through this performance monitoring indications are detected that exceed the acceptance standards of ASME Code,Section XI, IWB-3500, confirm that they will be evaluated as required by ASME Code,Section XI (which includes requirements for successive inspections and additional examinations) and describe other actions (if any) specified in the plants corrective action program to ensure that the integrity of the component is adequately maintained.

4.3.2 Entergy Response If during the performance monitoring schedule described above, indications are detected that exceed the applicable ASME Code,Section XI acceptance standards of IWB-3500, then the indications will be addressed as required by ASME Code Section XI, and the WF3 Corrective Action Program. The additional examination and successive inspection requirements of ASME Code,Section XI, also apply during the current outage. The number of additional exams shall be the number required by ASME Section XI, IWB-2430.

4.4 Request for Additional Information - 4 4.4.1 NRC Request If through this performance monitoring indications are detected that exceed the acceptance standards of ASME Code,Section XI, IWB-3500, then scope expansion may be appropriate to assess extent of condition. Furthermore, if this performance monitoring plan or industrywide operating experience indicates that a new or novel degradation mechanism is possible in PZR welds or nozzle inner radii, scope expansion may be appropriate to ensure that no such mechanism is occurring in the subject plants.

Discuss the detailed scope expansion plans for these scenarios.

4.4.2 Entergy Response As stated above, if indications are detected that exceed the applicable ASME Code,Section XI acceptance standards of IWB-3500, then the indications will be addressed as required by ASME Code Section XI, and the WF3 Corrective Action Program. The additional examination and successive inspection requirements of ASME Code,Section XI, also apply during the current outage. The number of additional exams shall be the number required by ASME Section XI, IWB-2430.

In addition to ASME Section XI, Entergy utilizes the Corrective Action Program to review and evaluate industry Operating Experience (OE) to determine the appropriate actions required based upon the specific OE. If the OE indicates that a new or novel degradation mechanism is possible in PZR welds or nozzle inner radii, the appropriate examinations will be performed or considered to ensure that no such mechanism is occurring in the subject plants.

W3F1-2024-0038 Enclosure Page 6 of 6

5.0 REFERENCES

1.

Entergy letter to NRC, "Proposed Alternative WF3-RR-24-01 for Examinations of Pressurizer Circumferential and Longitudinal Shell-to-Head Welds and Nozzle-to-Vessel Welds," ML24078A374, dated March 18, 2024

2.

NRC email to Entergy, "Request for Additional Information Proposed Alternative WF3-RR-24-01 Examinations of Pressurizer Welds Waterford Steam Electric Station, Unit 3, Entergy Operations, Inc. Docket No. 50-382," ML24236A140 dated August 26, 2024

3.

EPRI Technical Report 3002015906, "Technical Bases for Inspection Requirements for PWR Steam Generator Class 1 Nozzle-to-Vessel Welds and Class 1 and Class 2 Vessel Head, Shell, Tubesheet-to-Head and Tubesheet-to-Shell Welds," ML20225A141, EPRI, Palo Alto, CA: 2019

4.

EPRI Technical Report 3002014590, "Technical Bases for Inspection Requirements for PWR Steam Generator Feedwater and Main Steam Nozzle-to-Shell Welds and Inside Radius Sections," ML19347B107, EPRI, Palo Alto, CA: 2019

5.

Entergy letter to NRC, "Proposed Alternative WF3-RR-24-02 for Examinations of Steam Generator Pressure-Retaining Welds and Full Penetration Welded Nozzles,"

ML24078A376, dated March 18, 2024

6.

Constellation slides on Performance Monitoring from NRC Meeting, ML23033A667, January 30, 2023

7.

NRC slides, "Probabilistic Fracture Mechanics and Performance Monitoring,"

ML23114A034, April 27, 2023