ML23250A311

From kanterella
Jump to navigation Jump to search

Request to Revise Reactor Vessel Material Surveillance Capsule Withdrawal Schedules
ML23250A311
Person / Time
Site: Summer South Carolina Electric & Gas Company icon.png
Issue date: 09/20/2023
From: Markley M
NRC/NRR/DORL/LPL2-2
To: Carr E
South Carolina Electric & Gas Co
References
EPID L-2023-LLL-0002
Download: ML23250A311 (1)


Text

September 20, 2023 Mr. Eric S. Carr Senior Vice President and Chief Nuclear Officer Innsbrook Technical Center 5000 Dominion Blvd.

Glen Allen, VA 23060-6711

SUBJECT:

VIRGIL C. SUMMER NUCLEAR STATION, UNIT NO. 1 - RE: REQUEST TO REVISE REACTOR VESSEL MATERIAL SURVEILLANCE CAPSULE WITHDRAWAL SCHEDULES (EPID L-2023-LLL-0002)

Dear Mr. Carr:

By letter dated January 23, 2023 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML23024A154), Dominion Energy South Carolina (Dominion) requested approval to revise the reactor vessel materials surveillance capsule withdrawal schedules.

The U.S. Nuclear Regulatory Commission (NRC) staff has reviewed the subject request and concludes, as set forth in the enclosed safety evaluation, that Dominion has demonstrated that the proposed schedule revision remains consistent with the intent and requirements found in Appendix H to Title 10 of the Code of Federal Regulations (10 CFR), Part 50. Therefore, the NRC staff approves the requested change.

If you have any questions, please contact the Project Manager, Ed Miller at (301) 415-2481 or via e-mail at Ed.Miller@nrc.gov.

Sincerely, Michael T. Digitally signed by Michael T. Markley Date: 2023.09.20 15:47:02 -04'00' Markley Michael T. Markley, Chief Plant Licensing Branch 2-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-395

Enclosure:

Safety Evaluation cc: Listserv

SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION REVISION TO REACTOR VESSEL MATERIALS SURVEILLANCE CAPSULE WITHDRAWAL SCHEDULE DOMINION ENERGY SOUTH CAROLINA VIRGIL C. SUMMER NUCLEAR STATION, UNIT NO. 1 DOCKET NO. 50-395

1.0 INTRODUCTION

By letter dated January 23, 2023 (Reference 1), Dominion Energy South Carolina (a subsidiary of Dominion Energy [the licensee]) submitted for U.S. Nuclear Regulatory Commission (NRC) staffs review a request to revise the reactor pressure vessel (RPV) surveillance capsule withdrawal schedule for the RPV surveillance capsules at Virgil C. Summer Nuclear Station, Unit 1 (VCSNS). Specifically, the licensee requests NRC staff approval of a revision to current capsule withdrawal schedule described in Updated Final Safety Analysis Report (UFSAR)

Section 5.4.3.6.2.3 (Reference 2) in order to support the licensees anticipated operations of VCSNS through 80 years of planned operations, if the licensee decides to pursue a subsequent license renewal application of the unit in accordance with the requirements in 10 CFR Part 54 (Reference 3).

The licensees submittal indicates that its objective is to revise the capsule withdrawal schedule in a manner that aligns with the recommendations in NUREG-2191, Generic Aging Lessons Learned for Subsequent License Renewal (GALL-SLR) Report, including Aging Management Program Section XI.M31, Reactor Vessel Material Surveillance, (Reference 4) and (Reference 5), while still meeting the criteria specified in American Society for Testing and Materials (ASTM) Standard E185-82 (Reference 6), as referenced for implementation in Appendix H to 10 CFR Part 50 (Reference 7).

2.0 REGULATORY EVALUATION

The regulations and guidance pertinent to this request include the regulatory requirements summarized in the safety evaluation (SE) Section 2.1 and the applicable NRC guidelines summarized in SE Section 2.2:

Enclosure

2.1 Regulatory RequirementsSection I of Appendix H to 10 CFR Part 50 states, in part:

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 Appendix H to 10 CFR Part 50 states, in part:

The design of the surveillance program and the withdrawal schedule must meet the requirements of the edition of ASTM E 185 [an industry standard by ASTM International, formerly known as American Society for Testing and Materials] 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 Appendix H to 10 CFR Part 50 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.

NRC Administrative Letter 97-04, NRC Staff Approval for Changes to 10 CFR Part 50, Appendix H, Reactor Vessel Surveillance Specimen Withdrawal Schedules, dated September 30, 1997, (Reference 8) which states, in part:

The 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 NRC staff verification of such conformance.

2.2 Regulatory Guidance NUREG-2191, Volume 2 (GALL-SLR, Volume 2). GALL-SLR Chapter XI, Aging Management Program (AMP)Section XI.M31 (GALL-SLR XI.M31), Reactor Vessel Material Surveillance, (Reference 5) provides guidance for implementing an RPV surveillance program as an aging management program for managing loss of fracture toughness due to neutron irradiation embrittlement during the subsequent period of extended operation. Specifically, the guidance in the Parameters Monitored or Inspected program element of GALL-SLR XI.M31 states the program includes withdrawal and testing of at least one capsule addressing the subsequent

period of extended operation with a neutron fluence of the capsule between one and two times the peak neutron fluence of interest at the end of the subsequent period of extended operation.

3.0 TECHNICAL EVALUATION

Capsule Y is the only remaining untested capsule. The licensee stated that the capsules already tested (i.e., Capsules U, V, W, X, Z) satisfy the requirements under the current 60-year operating license.

The licensee stated that Capsule Y was withdrawn at 17.71 Effective Full Power Year (EFPY)

(and placed into spent fuel pool storage with an accumulated fluence exposure of 7.01 x 1019 n/cm2 [E > 1.0 MeV]) and proposed to reinsert Capsule Y back into the RPV and irradiate it further. Specifically, the licensee proposes that Capsule Y be withdrawn a second time after being exposed to a minimum of 10.5 additional EFPY of irradiation in order to experience the minimum 100-year fluence of 1.14 x 1020 n/cm2. The licensee explained that since the plant has experienced 32.38 EFPY at the end of cycle 26, Capsule Y is projected to be reinserted at 37.7 EFPY and projected to be removed (a second time) at 48.2 EFPY. However, the licensee emphasizes that these dates are only intended to be an estimate, and the actual dates will be based on withdrawing Capsule Y during the refueling outage nearest to, but following, the times when the reactor would achieve 37.7 EFPY and when Capsule Y would achieve a neutron fluence of 1.14 x 1020 n/cm2 for the subsequent Capsule Y removal objective.

Table 3-1 in this SE summarizes the timing of the past capsule withdrawals (and other data for capsule withdrawals), as currently specified in Section 5.4.3.6.2.3 of the VCSNS Final Safety Analysis Report (FSAR) and the proposed changes to the data in the submittal of January 23, 2023.

Table 3-1 Current FSAR-Defined RPV SC Withdrawal Times and Data And Proposed Changes to the Withdrawal Time and Data in the FSAR Capsule Azimuthal Location Capsule Lead Removal Time Calculated (SC) (Radial º) Factor (b) (Years/End of Fluence (n/cm2; Cycle [EOC]) (a) E > 1.0 MeV) (b)

Current Withdrawal Times and Data U 343 3.32 1.12 (EOC-1) 6.542 x 1018 V 107 3.72 2.93 (EOC-3) 1.538 x 1019 X 287 3.84 5.03 (EOC-5) 2.543 x 1019 W 110 3.40 10.78 (EOC-10 4.664 x 1019 Z 340 3.40 16.67 (EOC-14) 6.712 x 1019 Y 290 3.40 17.28 (EOC-15) (c)

Proposed Changes to the Data U 343 3.04 1.13 (EOC-1) 6.75 x 1018 V 107 3.34 2.93 (EOC-3) 1.54 x 1019 X 287 3.54 5.04 (EOC-5) 2.51 x 1019 W 110 3.21 11.21 (EOC-10 4.63 x 1019 Z 340 3.10 16.36 (EOC-14) 6.53 x 1019 Y 290 3.09 17.71 (EOC-15) 7.01 x 1019 107 ~3.5 48.2 1.14 X 1020 Notes: (a) Reported in effective full power years (EFPY) at the time of withdrawal. Note a core thermal power uprate from 2775 to 2900 mega-watts thermal (MWth) was implemented starting and Cycle 10.

(b) Capsule fluences and lead factors as previously reported and re-evaluated in WCAP-16298-NP, Revision 0, based on the Capsule Z dosimetry data.

(c) Capsule placed in storage for potential future use based on conformance with GALL AMP XI.M31 (Ref. 10) recommendations. (Reference 9) (Reference 10), and (Reference 11)

3.2 NRC Staff Review of the Proposed RPV Surveillance Capsule Withdrawal Schedule for VCSNS As shown in SE Table 3-1, the licensees proposed RPV surveillance capsule withdrawal schedule involves its change related to Capsule Y in addition to revisions of the prior data reported for Capsules U, V, X, W, and Z in in FSAR Section 5.4.3.6.2.3 based on the updated RPV fluence analysis reported in Westinghouse Non-Proprietary Class 3 Report No. WCAP-18728-NP, Rev. 3 (Reference 12); Enclosure 1 in the licensees letter of January 23, 2023). The report confirmed that neutron fluence values were determined using NRC-approved methods that meet RG 1.190 guidance (Reference 13).

The NRC staff noted that Capsule Y (currently a standby capsule) was initially removed at end-of cycle 15 (i.e., at 17.71 EFPY for EOC-15) with an accumulated capsule fluence exposure of 7.01 x 1019 n/cm2 (E > 1.0 MeV) and was then stored in the spent fuel pool. The licensee explained that, based on the latest RPV neutron fluence projections in WCAP-18728-NP, Rev. 3, the VCSNS RPV will achieve a peak, inside radius neutron fluence exposure of 6.74 x 1019 n/cm2 n/cm2 (E > 1.0 MeV) at 54 EFPY and 9.06 x 1019 n/cm2 (E > 1.0 MeV) at 72 EFPY; these fluence values include a 10% fluence bias added in for peripheral and re-entrant corner assembly relative powers. Without inclusion of the 10% fluence bias, the licensee reports that the RPV will achieve a peak, inside radius fluence of 6.52 x 1019 n/cm2 (E > 1.0 MeV) at 54 EPFY and 8.64 x 1019 n/cm2 (E > 1.0 MeV) at 72 EFPY. The NRC staff noted that the neutron exposure for Capsule Y (i.e., 7.01 x 1019 n/cm2 [E > 1.0 MeV)]) during its initial removal at 17.71 EFPY is greater than the peak, inside radius fluence projected for the RPV at 54 EFPY, but less than the peak, inside radius fluence projected for the RPV after 72 EFPY of operations.

The licensee explains that, when Capsule Y is reinserted into the RPV for an additional fluence exposure, the capsule will need at least 4.9 EFPY and no more than 22.4 EFPY of additional fluence exposure to meet the guidance in GALL-SLR XI.M31 for plant operations through 80-years. Thus, the licensee proposes to reinsert Capsule Y into the 107º azimuthal location (or into an equivalent 287º or 343º azimuthal location) of RPV during refueling outage 30 (i.e., in the fall of 2027 or at 37.7 EFPY of reactor operations) and to re-expose the capsule for an additional 10.5 EFPY of irradiation. This additional amount of irradiation time is based on an average fuel cycle of 1.33 EFPY/cycle and a conservative 90 percent capacity factor for the unit operating at critical power operations, where the capsule would be removed a second time at 48.2 EFPY with a projected capsule exposure of 1.14 x 1020 n/cm2 (E > 1.0 MeV) at the time of capsule withdrawal.

The NRC staff evaluated the proposed capsule withdrawal schedule for Capsule Y in terms of determining whether the proposed withdrawal at 48.2 EFPY would meet the GALL-SLR XI.M31 guidance (as described above) for the period of applicability associated with the current, first renewed operating license for VCSNS (i.e., 54 EFPY for first renewed license NPF-12).1 For the 54 EFPY evaluation consideration, the NRC staff verified that the proposed reinsertion of Capsule Y in 2027 (i.e., during RO 30, as identified in Table 7-1 of WCAP-18728-NP, Rev. 3) and second withdrawal of Capsule Y at 48.2 EFPY (i.e., at a projected fluence of 1.14 x 1020 1 The NRC staff acknowledges that, in the letter of January 23, 2023, the licensee also evaluated the proposed withdrawal schedule for Capsule Y in terms of meeting the GALL-SLR AMP XI.M31 criteria for potential 80 year (i.e., 72 EFPY) and 100 year (90 EFPY) subsequent license renewal periods. The NRC staff will evaluate the impacts of the proposed Capsule Y withdrawal schedule for 80-year or 100-year subsequent license renewal considerations should the licensee decide to pursue license extension for those periods in accordance with the license renewal application requirements specified in 10 CFR Part 54.

Thus, the NRC staff is not including the 80 year and 100 year considerations within the scope of this evaluation.

n/cm2 [E > 1.0 MeV]) will meet the GALL-SLR XI.M31 withdrawal time objective for the RPV surveillance program at 54 EFPY because the licensee: (1) will be using an approved RAPTOR-based neutron fluence methodology for the Capsule Y fluence projections (at withdrawal), and (2) has demonstrated the capsule will achieve a capsule fluence exposure that is between one and two times the peak, projected inside radius fluence for the RPV at 54 EFPY (i.e., the Capsule Y exposure will be between 6.52 x 1019 n/cm2 to 1.304 x1020 n/cm2 [E > 1.0 MeV; no fluence bias included] at the time of capsule withdrawal).

Thus, the NRC staff finds the proposal to reinsert Capsule Y into the RPV at 37.7 EFPY and to withdraw Capsule Y a second time at 48.2 EFPY to be acceptable because: the NRC staff has verified that the additional 10.5 EFPY of irradiation exposure and projected neutron fluence exposure for Capsule Y at 48.2 EFPY will meet the intent of the capsule withdrawal schedule criteria in ASTM Standard Practice E185-82 and the guidance in GALL-SLR XI.M31 for removing a RPV surveillance capsule with a projected neutron fluence exposure that is between one and two times the peak, projected inside radius neutron fluence for the RPV at the end of the licensed life of the unit (i.e., at 54 EFPY, as associated with the end of the first renewed operating term for Renewed Operating License NPF-12).

4.0 CONCLUSION

The NRC staffs review is limited only to the information in the licensees letter of January 23, 2023, and the licensees updated RPV surveillance capsule withdrawal schedule information and data that were reported for the VCSNS RPV surveillance program in Chapter 7 and Table 7-1 of WCAP-18728-NP, Rev. 3 (i.e., as enclosed in Enclosure 1 of the letter of January 23, 2023). The scope of the NRC staffs review does not include the remaining chapters, tables or figures in the WCAP-18728-NP, Rev. 3 report. Therefore, the report sections for the updated RPV adjusted reference temperature, pressurized thermal shock, upper shelf energy, and pressure and temperature limit evaluations in WCAP-18728-NP, Rev. 3, are not within the scope of or part of the NRC staffs approval basis in this safety evaluation.

Based on the NRC staffs review, it has determined that the licensee has already fulfilled its RPV surveillance requirements for VCSNS during the term in the current operating license (i.e.,

first renewed license covering a cumulative 60-year operational period) with the withdrawal and testing of Capsules in U, V, W, X and Z. The NRC staff also determined the proposed surveillance capsule schedule Capsule Y is acceptable because: (1) the timing of the proposed reinsertion and subsequent withdrawal activities for Capsule Y will achieve a capsule fluence exposure that is between one and two times the peak projected inside radius fluence of the VCSNS RPV at 54 EFPY (as recommended in GALL-SLR AMP XI.M31), and (2) the proposed withdrawal schedule for Capsule Y will meet the intent of the capsule material testing and withdrawal schedule criteria in ASTM Standard Practice E-185-82, as implemented in accordance with the RPV surveillance program to monitor changes in the fracture toughness properties of ferritic materials in the beltline of the RPV. Therefore, the NRC staff finds the licensees proposed withdrawal schedule for Capsule Y (i.e., capsule reinsertion during refueling outage 30 and subsequent withdrawal during the refueling outage nearest to, but following, the Capsule Y achieving neutron fluence exposure of 1.14 x 1020 n/cm2 [E > 1.0 MeV] - currently estimated to occur at approximately 48.2 EFPY, with subsequent capsule specimen testing occurring after capsule withdrawal) is acceptable.

The NRC staff notes that, when Capsule Y is removed from the RPV at approximately 48.2 EFPY, a summary report containing the test results for Capsule Y must be submitted to the NRC within 18 months of the capsule withdrawal, as required by the reporting requirements

specified in Section IV.A of Appendix H to 10 CFR Part 50. The NRC staff further notes that the fluence values were only reviewed for the purpose of evaluating the schedule change.

5.0 REFERENCES

1 Dominion Energy South Carolina letter to U.S. Nuclear Regulatory Commission (NRC),

Virgil C. Summer Nuclear Station Unit 1 - Proposed Reactor Vessel Surveillance Capsule Withdrawal Schedule to Support Potential Subsequent License Renewal Activity.,

January 23, 2023 (ML23024A154).

2 U.S. Nuclear Regulatory Commission, Updated Safety Analysis Report (UFSAR), Chapter 5, Reactor Coolant System., May 25, 2016 (ML16166A114).

3 Title 10 of the Code of Federal Regulations, Part 54 - Requirements for Renewal of Operating Licenses for Nuclear Power Plants., May 8, 1995.

4 U.S. Nuclear Regulatory Commission (NRC), NUREG-2191, Volume 1 - Generic Aging Lessons Learned for Subsequent License Renewal (GALL-SLR) Report, Final Report.,

July 2017 (ML17187A031).

5 U. S. Nuclear Regulatory Commission (NRC), NUREG-2191, Volume 2 - Generic Aging Lessons Learned for Subsequent License Renewal (GALL-SLR) Report, Final Report.,

July 2017 (ML17187A204).

6 American Society for Testing and Materials, ASTM E185 Standard Practice for Conducting Surveillance Tests for Light-Water Cooled Nuclear Power Reactor Vessels.,

July 1, 1982.

7 Title 10 of the Code of Federal Regulations, Part 50, Appendix H - Reactor Vessel Material Surveillanc Program Requirements., January 1, 2016.

8 U.S. Nuclear Regulatory Commission (NRC), NRC Administrative Letter 97-04: NRC Staff Approval for Changes to 10 CFR Part 50, Appendix H, Reactor Vessel Surveillance Specimen Withdrawal Schedules., September 30, 1997 (ML031210296).

9 U.S. Nuclear Regulatory Commission (NRC), NUREG-1801, Vol. 1 - Generic Aging Lessons Learned (GALL) Report - Summary., July 2001 (ML012060392).

10 U.S. Nuclear Regulatory Commission (NRC), NUREG-1801, Vol. 2 - Generic Aging Lessons Learned (GALL) Report - Tabulation of Results., July 2001 (ML012060514).

11 U.S. Nuclear Regulatory Commission (NRC), NUREG-1801, Vol. 2 - [Pages IV A2-1 to VII F3-4] Generic Aging Lessons Learned (GALL) Report - Tabulation of Results., July 2001 (ML012060539).

12 Dominion Energy South Carolina and Westinghouse Electric Company, LLC, Enclosure 1 - WCAP-18728-NP, Rev. 3, V.C. Summer Nuclear Station Unit 1 - Subsequent License Renewal: Evaluation of Reactor Vessel INtegrity Time-Limiting Aging Analysis.,

August 2022 (Enclosure 1 to ML23024A154).

13 U.S. Nuclear Regulatory Commission (NRC), Regulatory Guide (RG) 1.190 - Calculational and Dosimetry Methods for Determining Pressure Vessel Neutron Fluence., March 2001 (ML010890301).

14 Title 10 of the Code of Federal Regulations, Part 50.60 - Acceptance Criteria for Fracture Prevention Measures for Lightwater Nuclear Power Reactors for Normal Operation.,

July 29, 1996.

15 U.S. Nuclear Regulatory Commission (NRC), NUREG-1787 - Safety Evaluation Report - Related to the License Renewal of the Virgil C. Summer Nuclear Station., March 2004 (ML041040070).

16 Westinghouse Electric Company, LLC, WCAP-18124-NP-A, Revision 0, Fluence Determination with RAPTOR-M3G and FERRET., July 2018 (ML18204A010).

Principal Contributor: J. Medoff, NRR J. Messina, NRR Date: September 20, 2023

ML23250A311 *Via SE Input NRR-043 OFFICE NRR/DORL/LPL2-1/PM NRR/DORL/LPL2-1/LA NRR/DSS/SFNB NAME GEMiller KGoldstein SKrepel DATE 9/13/2023 9/8/2023 9/13/2023 OFFICE NRR/DNRL/NVIB NRR/DORL/LPL2-1/BC NAME ABuford* MMarkley DATE 8/30/2023 9/20/2023