ML21131A024

Review of Reactor Pressure Vessel Capsule Y Analysis Report

ML21131A024
Person / Time
Site:	Beaver Valley
Issue date:	05/17/2021
From:	Jennifer Tobin Plant Licensing Branch 1
To:	Grabnar J Energy Harbor Nuclear Corp
Tobin J
Shared Package
ML21131A044	List: ML21131A024
References
EPID L-2020-LLL-0023
Download: ML21131A024 (7)

Text

May 17, 2021 Mr. John J. Grabnar Site Vice President Energy Harbor Nuclear Corp.

Beaver Valley Power Station Mail Stop P-BV-SSB P.O. Box 4, Route 168 Shippingport, PA 15077

SUBJECT:

BEAVER VALLEY POWER STATION, UNIT 2 - REVIEW OF REACTOR PRESSURE VESSEL CAPSULE Y ANALYSIS REPORT (EPID L-2020-LLL-0023)

Dear Mr. Grabnar:

By letter dated October 28, 2020 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML20302A376), Energy Harbor Nuclear Corp. (Energy Harbor) submitted a technical summary of the results of the mechanical property tests conducted on the fifth capsule withdrawn from the Beaver Valley Power Station, Unit No. 2 reactor pressure vessel. The report was provided in accordance with Title 10 of the Code of Federal Regulations (10 CFR) Part 50 Appendix H,Section IV. Testing was performed in accordance with American Society for Testing and Materials Standard ASTM E 185-82, Standard Practice for Conducting Surveillance Tests for Light-Water Cooled Nuclear Power Reactor Vessels, as specified in 10 CFR Part 50, Appendix H, paragraph III.B.1.

The U.S. Nuclear Regulatory Commission (NRC) staff has completed its review of Energy Harbors submittal, as documented in the enclosed evaluation. The NRC staff concludes that Energy Harbor has provided the information required by the regulations and that no additional follow-up is required at this time. This completes the NRC staffs efforts for EPID L-2020-LLL-0023.

J. Grabnar If you have any questions, please contact me at 301-415-2328 or Jennifer.Tobin@nrc.gov.

Sincerely,

/RA/

Jennifer C. Tobin, Project Manager Plant Licensing Branch I Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-412

Enclosure:

Review of the Reactor Pressure Vessel Capsule Y Analysis Report cc: Listserv

ML21131A024 *by memo dated OFFICE NRR/DORL/LPL1/PM NRR/DORL/LPL1/LAiT NRR/DORL/LPL1/LA NRR/DNRL/NCSG/BC*

NAME JTobin KZeleznock JBurkhardt DWidrevitz (A)

DATE 5/10/2021 5/11/2021 5/14/2021 4/30/2021 OFFICE NRR/DSS/SFNB/BC* NRR/DORL/LPL1/BC NRR/DORL/LPL1/PM NAME RLukes JDanna JTobin DATE 5/14/2021 5/17/2021 5/17/2021 OFFICE OF NUCLEAR REACTOR REGULATION REVIEW OF REACTOR PRESSURE VESSEL CAPSULE Y ANALYSIS REPORT ENERGY HARBOR NUCLEAR CORP.

BEAVER VALLEY POWER STATION, UNIT 2 DOCKET NO. 50-412

1.0 INTRODUCTION AND BACKGROUND

By letter dated October 28, 2020 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML20302A376), Energy Harbor Nuclear Corporation (the licensee),

submitted an evaluation of Beaver Valley Power Station (Beaver Valley), Unit 2, Surveillance Capsule Y. The details of the evaluation are addressed in Westinghouse Electric Company, LLCs technical report WCAP-18558-NP, Revision 0, Analysis of Capsule Y from the Beaver Valley Unit 2 Reactor Vessel Radiation Surveillance Program, June 2020. The evaluation was submitted in accordance with the requirements of Title 10 of the Code of Federal Regulations (10 CFR) Part 50, Appendix H, Reactor Vessel Material Surveillance Program Requirements.

The regulations in 10 CFR Part 50, Appendix H require that nuclear power plants install and, at certain intervals, remove and analyze the changes in fracture toughness of the reactor vessel (RV) materials contained in the surveillance capsules. Irradiation surveillance of the RV is necessary to assure that the vessel material will maintain its fracture toughness throughout the service life of the plant. The surveillance capsule contains both dosimeters as well as archival material samples to be irradiated to levels comparable to those expected to be accrued by the RV at the end of its licensed period. This is accomplished by mounting the surveillance capsule in a location closer to the core to accelerate its exposure rate. The metric used for material embrittlement is the reference temperature for nil-ductility transition temperature (RTNDT).

Five surveillance capsules in the Beaver Valley, Unit 2 RV material surveillance program, designated as U, V, W, X, and Y, were inserted before reactor startup between the thermal shield and the vessel wall, at various azimuthal locations. Capsules U, V, W, and X have been removed and analyzed. This review addresses Capsule Y, mounted at an azimuthal angle of 290 degrees with a lead factor of 2.97, and is limited to the requirements in Section IV, Report of Test Results, of Appendix H to 10 CFR Part 50.

2.0 REGULATORY REQUIREMENTS The RV surveillance program for Beaver Valley, Unit 2, was established in accordance with 10 CFR Part 50, Appendix H, which requires licensees to monitor changes in the fracture toughness properties of ferritic materials in the RV beltline region of light-water nuclear power reactors. Appendix H states that the design of the RV surveillance program must meet the requirements of the edition of the American Society for Testing and Materials (ASTM)

Standard E185, Standard Practice for Conducting Surveillance Test for Light-Water Cooled Nuclear Power Reactor Vessels, that was current on the issue date of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code) to which the RV was purchased; however, the licensee may choose to use later editions through 1982 of the ASTM Enclosure

standard. The requirements for the reporting of test results are described in Section IV of Appendix H to 10 CFR Part 50.

The U.S. Nuclear Regulatory Commission (NRC) staffs review was performed in consideration of the applicable requirements contained Appendix A, General Design Criteria for Nuclear Power Plants, to 10 CFR Part 50. Specifically, General Design Criteria (GDC) 14, Reactor coolant pressure boundary, 30, Quality of reactor coolant pressure boundary, and 31, Fracture prevention of reactor coolant pressure boundary, apply. These GDCs require the design, fabrication, and maintenance of the reactor coolant pressure boundary with adequate margin to assure that the probability of rapidly propagating failure of the boundary is minimized.

In particular, GDC 31 explicitly requires consideration of the effects of irradiation on material properties.

NRC Regulatory Guide (RG) 1.190, Calculational and Dosimetry Methods for Determining Pressure Vessel Neutron Fluence, March 2001 (ADAMS Accession No. ML010890301),

provides guidance on methods for determining reactor pressure vessel fluence that are acceptable to the NRC staff, based on the requirements identified above.

3.0 TECHNICAL EVALUATION

3.1 Neutron Fluence The neutron fluence evaluation supporting the Capsule Y dosimetry analysis is described in Chapter 6 of WCAP-18558-NP, Analysis of Capsule Y from the Beaver Valley, Unit 2 Reactor Vessel Radiation Surveillance Program, which was enclosed with the licensees submittal dated October 28, 2020. The fluence was estimated using the methods described in NRC-approved topical report WCAP-18124-NP-A, Fluence Determination with RAPTOR-M3G and FERRET, July 2018 (ADAMS Accession No. ML18204A010). The NRC staffs safety evaluation approving WCAP-18124-NP-A documents the technical basis that fluence calculations performed using RAPTOR-M3G are adherent to RG 1.190 and hence acceptable.

For the Capsule Y analysis, the licensee used a model that reflected octant-symmetric geometry of Beaver Valley, Unit 2, using nominal design dimensions. The licensee also assumed core power distributions reflective of the actual operating characteristics through Cycle 20, and projected future cycles using an average of Cycles 17, 18, and 19. Similarly, cycle-specific coolant densities were modeled. These plant-specific aspects of the Beaver Valley, Unit 2 analysis are consistent with RG 1.190, which (1) indicates that planar-octant modeling is acceptable; (2) permits the use of nominal design dimensions; (3) recommends accounting for actual core operating history for the core neutron source; and (4) recommends accounting for the variations in water density. Since the plant-specific modeling is consistent with RG 1.190 recommendations, the NRC staff determined that it is acceptable.

The licensee provided comparisons of measured to calculated (M/C) activity rates for the set of dosimetry materials contained in Capsule Y. The M/C agreement of the iron dosimeter was 0.88, representing the least good agreement, and the copper dosimeter indicated the best agreement at 0.94. These comparisons demonstrate that the agreement between measured and calculated activities is consistent with the 13 percent estimated uncertainty of the RAPTOR-M3G fluence methodology, and well within the 20 percent agreement recommended by RG 1.190. Because the M/C agreement shown by the dosimetry analysis is both consistent with the estimated uncertainty of the methodology and the agreement is consistent with

RG 1.190 recommendations, the NRC staff determined that the evaluation results are acceptable.

The NRC staffs safety evaluation for WCAP-18124-NP-A contains two limitations and conditions, which the licensee discussed in Chapter 6 of WCAP-18558-NP. The first limitation and condition relates to the qualification of RAPTOR-M3G to perform fluence estimates in the extended beltline region, which is the region of the reactor vessel located axially distant (i.e., above or below) from the active fuel in the core. Because Capsule Y is axially collocated with the active fuel, the licensee stated that the limitation does not apply. The second limitation and condition relates to the use of the FERRET least squares variance reduction methodology to adjust the estimated fluence values. The licensee stated that the comparison provided in WCAP-18558-NP used unadjusted fluence values, such that the second limitation and condition is also not applicable. Since the licensee explained why neither condition and limitation was applicable, the NRC staff determined that the licensee acceptably addressed both conditions and limitations.

Based on the considerations discussed above: (1) the licensee used an NRC-approved fluence methodology that is adherent to RG 1.190 guidance; (2) plant-specific assumptions used in the fluence analysis are similarly adherent to RG 1.190; (3) the licensee demonstrated acceptable agreement between measured and calculated activity rates for the dosimetry materials; and (4) the licensee dispositioned the limitations and conditions on WCAP-18124-NP-A acceptably; therefore, the NRC staff determined that the fluence analysis supporting Capsule Y was acceptable. Based on the consistency with RG 1.190 recommendations, the NRC staff determined that the calculations are consistent with the NRC requirements contained in GDCs 14, 30, and 31.

3.2 Review of 10 CFR 50, Appendix H Reporting Requirements Paragraph IV.A of Appendix H to 10 CFR Part 50 specifies that a summary technical report for each capsule withdrawal and the associated test results must be submitted within 1 year of the date of capsule withdrawal, unless an extension is granted by the Director, Office of Nuclear Reactor Regulation. The NRC staff finds that the licensees submittal of WCAP-18558-NP, Revision 0, has fulfilled the reporting requirements of Paragraph IV.A of 10 CFR Part 50, Appendix H.

Paragraph IV.B of Appendix H to 10 CFR Part 50 specifies that the report must include the data required by ASTM E 185, as specified in paragraph III.B.1 of this appendix, and the results of all fracture toughness tests conducted on the beltline materials in the irradiated and unirradiated conditions. The base metal in the Beaver Valley, Unit 2, RV material surveillance program is Intermediate Shell Plate (Heat# B9004-2). The Beaver Valley, Unit 2 surveillance plate data (Heat# B9004-2) is deemed to be non-credible, whereas the surveillance weld (Heat# 83642) data is deemed to be credible. This credibility evaluation can be found in Appendix D. Based on its review of ASTM E 185-82 and the licensees report, the NRC staff confirmed that the report includes all of the data and test results that are required by Paragraph IV.B of 10 CFR Part 50, Appendix H and ASTM E 185-82. The staff noted that Capsule Y had received fluence representative of 60 years of licensee. Furthermore, the licensee had installed ex-vessel dosimetry for future measurement of RV neutron fluence.

4.0 CONCLUSION

By letter dated October 28, 2020, the licensee transmitted WCAP-18558-NP, Revision 0. The NRC staffs review was limited to determining compliance with the requirements in Section IV of 10 CFR Part 50, Appendix H, and evaluating the acceptability of the supporting fluence analysis. The NRC staff concludes that the fluence analysis supporting the Capsule Y test results is acceptable and consistent with the requirements of GDCs 14, 30, and 31. The staff also concludes that the licensees submittal meets the reporting requirements in Section IV of 10 CFR Part 50, Appendix H and noted that as a result of the Capsule Y test results for Beaver Valley, Unit 2, a revised pressure-temperature limits report is expected to be provided to NRC prior to the expiration of the current pressure-temperature limits.

Principal Contributors: G. Cherunveki B. Parks