ML20230A051
| ML20230A051 | |
| Person / Time | |
|---|---|
| Site: | Prairie Island  |
| Issue date: | 09/03/2020 |
| From: | Nancy Salgado Plant Licensing Branch III |
| To: | Sharp S Northern States Power Co |
| Kuntz R | |
| References | |
| EPID L-2020-LLL-0016 | |
| Download: ML20230A051 (7) | |
Text
September 3, 2020 Mr. Scott Sharp Site Vice President Prairie Island Nuclear Generating Plant Northern States Power Company - Minnesota 1717 Wakonade Drive East Welch, MN 55089
SUBJECT:
PRAIRIE ISLAND NUCLEAR GENERATING PLANT, UNITS 1 AND 2 -
REACTOR VESSEL MATERIAL SURVEILLANCE CAPSULE WITHDRAWAL SCHEDULES (EPID L-2020-LLL-0016)
Dear Mr. Sharp:
By letter dated July 28, 2020 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML20210M353), Northern States Power Company, a Minnesota corporation, doing business as Xcel Energy (Xcel, the licensee) requested revision of the reactor vessel material surveillance capsule withdrawal schedules for Prairie Island Nuclear Generating Plant (Prairie Island), Units 1 and 2. The revised schedule was submitted in accordance with Title 10 of the Code of Federal Regulations (10 CFR) Part 50, Appendix H, Reactor Vessel Material Surveillance Program Requirements, III.B.3 and as required by Prairie Island, Units 1 and 2, License Condition 2.C(8)(c).
The U.S. Nuclear Regulatory Commission (NRC) staff has reviewed the subject request and concludes, as set forth in the enclosed safety evaluation, that the modified surveillance capsule withdrawal schedule for Prairie Island, Units 1 and 2, are acceptable for implementation and satisfies the requirements of Appendix H to 10 CFR Part 50 and Prairie Island, Units 1 and 2, License Condition 2.C(8)(c), for the current 60-year license term.
S. Sharp If you have any questions, please contact the Project Manager, Robert Kuntz at 301-415-3733 or via e-mail at Robert.Kuntz@nrc.gov.
Sincerely, Nancy L. Salgado, Chief Plant Licensing Branch III Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket Nos. 50-282 and 50-306
Enclosure:
Safety Evaluation cc: Listserv Nancy L.
Salgado Digitally signed by Nancy L. Salgado Date: 2020.09.03 13:01:53 -04'00'
Enclosure SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION REQUEST FOR REVISION TO REACTOR VESSEL MATERIAL SURVEILLANCE CAPSULE REMOVAL SCHEDULES FOR NORTHERN STATES POWER COMPANY PRAIRIE ISLAND NUCLEAR GENERATING PLANT, UNITS 1 AND 2 DOCKET NOS. 50-282 AND 50-306
1.0 INTRODUCTION
By letter dated July 28, 2020 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML20210M353), Northern States Power Company, a Minnesota corporation, doing business as Xcel Energy (Xcel, the licensee) requested revision of the reactor vessel material surveillance capsule withdrawal schedules for Prairie Island Nuclear Generating Plant (Prairie Island), Units 1 and 2. The revised schedule was submitted in accordance with Title 10 of the Code of Federal Regulations (10 CFR) Part 50, Appendix H, Reactor Vessel Material Surveillance Program Requirements, III.B.3 and as required by Prairie Island, Units 1 and 2, License Condition 2.C(8)(c).
The licensee proposed to withdraw Standby Capsule T or Planned Capsule N in Prairie Island, Unit 1, and Standby Capsule S or Planned Capsule N in Prairie Island, Unit 2. The licensee stated that this proposal provides additional flexibility for removal of surveillance capsules due to plant-specific circumstances. Specifically, the licensee explained that a previous attempt to remove Capsule T in Prairie Island, Unit 1, was not successful.
2.0 REGULATORY EVALUATION
The regulations and guidance relevant to this request include:
Section I of 10 CFR 50, Appendix H, Reactor Vessel Material Surveillance Program Requirements, states, in part, that:
The purpose of the reactor vessel material surveillance program required by this appendix is to monitor changes in the fracture toughness properties of ferritic materials in the reactor vessel beltline region of light water nuclear power reactors which result from exposure of these materials to neutron irradiation and the thermal environment. Under the program, fracture toughness test data are obtained from material specimens exposed in surveillance capsules, which are withdrawn periodically from the reactor vessel.
Section III.B.1 of 10 CFR 50, Appendix H, states, in part:
The design of the surveillance program and the withdrawal schedule must meet the requirements of the edition of ASTM E 185 that is current on the issue date of the ASME Code to which the reactor vessel was purchased. Later editions of ASTM E 185 may be used, but including only those editions through 1982.
Section III.B.3 of 10 CFR 50, Appendix H, states:
A proposed withdrawal schedule must be submitted with a technical justification as specified in 10 CFR 50.4. The proposed schedule must be approved prior to implementation.
Prairie Island, Units 1 and 2, License Condition 2.C(8)(c) state:
All capsules in the reactor vessel that are removed and tested must meet the test procedures and reporting requirements of American Society for Testing and Materials (ASTM) E 185-82 to the extent practicable for the configuration of the specimens in the capsule. Any changes to the capsule withdrawal schedule, including spare capsules, must be approved by the NRC prior to implementation.
All capsules placed in storage must be maintained for future insertion. Any changes to storage requirements must be approved by the NRC.
Administrative Letter 97-04, states, in part, that:
The Commission [U.S. Nuclear Regulatory Commission (NRC or Commission)]
found that while 10 CFR Part 50, Appendix H, II.B.3 requires prior NRC approval for all withdrawal schedule changes, only certain changes require license amendments as the process to be followed for such approval. Specifically, those changes that do not conform to the ASTM standard referenced in Appendix H (ASTM E-185, Standard Practice for Conducting Surveillance Tests for Light-Water Cooled Nuclear Power Reactor Vessels) will require approval by the license amendment process, whereas changes that conform to the ASTM standard require only staff verification of such conformance.
3.0 TECHNICAL EVALUATION
3.1 Proposal for Prairie Island, Unit 1 Table 3 of the submittal provided the proposed revision to the reactor vessel surveillance capsule removal schedules for Prairie Island, Unit 1. The proposed change adds Withdrawal effective full power years (EFPY) and Fluence data for the Standby Capsule T, adds a label of Planned to Capsule N, and a new note that allows removal of the Standby Capsule T if unforeseen circumstances preclude removal of the Planned Capsule N. Specifically, the submittal proposed to withdraw Planned Capsule N at 39.90 to 43.60 EFPY of operation from plant startup. As stated in the submittal, this corresponds to a neutron fluence of between 7.54 x 1019 and 8.11 x 1019 n/cm2 (E > 1 MeV). Further, the licensee proposed to withdraw Standby Capsule T at 39.90 to 43.60 EFPY of operation from plant startup, which corresponds to a neutron fluence of between 8.05 x 1019 and 8.66 x 1019 n/cm2 (E > 1 MeV).
3.2 Proposal for Prairie Island, Unit 2 Table 4 of the submittal provides the proposed revision to the reactor vessel surveillance capsule removal schedules for Prairie Island, Unit 2. The proposed change adds Withdrawal EFPY and Fluence data for the Standby Capsule S, adds a label of Planned to Capsule N, and a new note that allows removal of the Standby Capsule S if unforeseen circumstances preclude removal of the Planned Capsule N. Specifically, the submittal proposed to withdraw Planned Capsule N at 40.59 to 44.29 EFPY from plant startup, which corresponds to a neutron fluence of between 7.32 x 1019 and 7.88 x 1019 n/cm2 (E > 1 MeV). Further, the licensee proposed to withdraw Standby Capsule S at 40.59 to 44.29 EFPY from plant startup, which corresponds to a neutron fluence of between 7.32 x 1019 and 7.88 x 1019 n/cm2 (E > 1 MeV).
3.3 NRC Staff Review Surveillance capsules are withdrawn and tested periodically as designated in the withdrawal schedule.Section III.B.3 of Appendix H to 10 CFR Part 50 requires that the proposed schedule be approved prior to implementation.
ASTM E185-82 defines End of Life (EOL) as the design lifetime in terms of years, EFPY, or neutron fluence. Table 1 in ASTM E185-82 lists the minimum recommended number of surveillance capsules and their withdrawal schedule. Table 1, Note E indicates that the final surveillance capsule to be withdrawn should be withdrawn not less than once or greater than twice the peak EOL vessel fluence. The NRC staff noted that for Prairie Island, Units 1 and 2, the 60-year renewed operating license corresponds to 54 EFPY of operation from plant startup, which is based on an assumed 90 percent capacity factor. The licensee indicated that after capsule removal, the surveillance specimens will be tested in accordance with ASTM E185-82, Standard Practice for Conducting Surveillance Tests for Light-Water Cooled Nuclear Power Reactor Vessels, which is consistent with the requirements for testing outlined in Section III.B.1 of Appendix H to 10 CFR Part 50.
The NRC staff noted that that the licensees proposal to withdraw Standby Capsule T or Planned Capsule N in Prairie Island, Unit 1, and Standby Capsule S or Planned Capsule N in Prairie Island, Unit 2, provides the licensee with additional flexibility for removal of surveillance capsules due to plant-specific circumstances. Specifically, the licensee explained that a previous attempt to remove Capsule T in Prairie Island, Unit 1, was not successful.
However, due to advances in tooling used to remove capsules, the licensee may attempt to remove Capsule T if Capsule N on Prairie Island, Unit 1, is stuck.
For Prairie Island, Unit 1, the submittal indicated that the maximum reactor vessel fluence at 54 EFPY is projected to be 5.162 x 1019 n/cm2 (E > 1.0 MeV). The NRC staff noted that none of the previously removed Prairie Island, Unit 1, capsules have been subjected to neutron fluence equal to or greater than the maximum reactor vessel fluence projected for 54 EFPY. The submittal proposes removing Capsule N at a fluence of between 7.54 x 1019 and 8.11 x 1019 n/cm2 (E > 1 MeV), or Capsule T at a fluence of between 8.05 x 1019 and 8.66 x 1019 n/cm2 (E > 1 MeV). In order to achieve these proposed fluences, the licensee stated that a capsule (i.e., Planned Capsule N or Standby Capsule T) will be removed for testing from Prairie Island, Unit 1, during refueling outage 1R32 (2020), 1R33 (2022) or 1R34 (2024).
The NRC staff noted that Planned Capsule N or Capsule T from Prairie Island, Unit 1, is scheduled to be withdrawn not less than once nor greater than twice the 60-year renewed operating license neutron peak fluence. The NRC staff finds the licensees proposal for Prairie Island, Unit 1, to withdraw and test either Planned Capsule N or Standby Capsule T provides reasonable assurance that sufficient material data and dosimetry to monitor irradiation embrittlement of the reactor vessel for the current 60-year license term is available, consistent with the purpose of Appendix H to 10 CFR Part 50.
For Prairie Island, Unit 2, the submittal indicated that the maximum reactor vessel fluence at 54 EFPY is projected to be 5.196 x 1019 n/cm2 (E > 1.0 MeV). The NRC staff noted that none of the previously removed Prairie Island, Unit 2, capsules have been subjected to neutron fluence equal to or greater than the maximum reactor vessel fluence projected for 54 EFPY. The submittal proposes removing Planned Capsule N at a fluence of between 7.32 x 1019 and 7.88 x 1019 n/cm2 (E > 1 MeV), or Standby Capsule S at a fluence of between 7.32 x 1019 and 7.88 x 1019 n/cm2 (E > 1 MeV). In order to achieve these proposed fluences, the licensee stated that a capsule (i.e., Capsule N or Capsule S) will be removed for testing from Prairie Island, Unit 2, during refueling outage 2R32 (2021), 2R33 (2023) or 2R34 (2025). The NRC staff noted that Planned Capsule N or Standby Capsule S from Prairie Island, Unit 2, is scheduled to be withdrawn not less than once nor greater than twice the 60-year renewed operating license neutron peak fluence. The NRC staff finds the licensees proposal for Prairie Island, Unit 2, to withdraw and test either Planned Capsule N or Standby Capsule S provides reasonable assurance that sufficient material data and dosimetry to monitor irradiation embrittlement of the reactor vessel for the current 60-year license term is available, consistent with the purpose of Appendix H to 10 CFR Part 50.
4.0 CONCLUSION
Based on the above evaluation, the NRC staff concludes that the revised surveillance capsule withdrawal schedule for Planned Capsule N or Standby Capsule T (Prairie Island, Unit 1),
and Planned Capsule N or Standby Capsule S (Prairie Island, Unit 2) ensures sufficient material data and dosimetry to monitor irradiation embrittlement of the reactor vessel for the current 60-year license term is available. Therefore, the NRC staff concludes that the licensee's modified surveillance capsule withdrawal schedule for Planned Capsule N or Standby Capsule T (Prairie Island, Unit 1), and Planned Capsule N or Standby Capsule S (Prairie Island, Unit 2) is acceptable for implementation and satisfies the requirements of Appendix H to 10 CFR Part 50 and Prairie Island, Units 1 and 2, License Condition 2.C(8)(c).
Principal Contributor: On Yee, NRR Date of issuance: September 3, 2020
S. Sharp
SUBJECT:
PRAIRIE ISLAND NUCLEAR GENERATING PLANT, UNITS 1 AND 2 -
REACTOR VESSEL MATERIAL SURVEILLANCE CAPSULE WITHDRAWAL SCHEDULES (EPID L-2020-LLL-0016) DATED SEPTEMBER 3, 2020 DISTRIBUTION:
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NAME RKuntz SRohrer HGonzalez NSalgado DATE 8/17/2020 8/17/2020 8/20/2020 9/3/2020