ML20272A227

Audit Summary: Proposed License Amendment Request for the Addition of Westinghouse Topical Report

ML20272A227
Person / Time
Site:	Surry, North Anna
Issue date:	10/23/2020
From:	Vaughn Thomas Plant Licensing Branch II
To:	Stoddard D Dominion Energy Virginia
Thomas V, NRR/DORL/LPL2-1, 415-5897
References
EPID L-2019-LLA-0236, EPID L-2019-LLA-0243
Download: ML20272A227 (6)

Text

October 23, 2020 Mr. Daniel G. Stoddard Senior Vice President and Chief Nuclear Officer Innsbrook Technical Center 5000 Dominion Boulevard Glen Allen, VA 23060-6711

SUBJECT:

SURRY NUCLEAR POWER STATION, UNITS 1 AND 2 AND NORTH ANNA POWER STATION UNITS 1 AND 2 - AUDIT

SUMMARY

PROPOSED LICENSE AMENDMENT REQUEST FOR THE ADDITION OF WESTINGHOUSE TOPICAL REPORT WCAP-16996-P-A, REVISION 1, TO THE CORE OPERATING LIMITS REPORT (EPID L-2019-LLA-0243 AND EPID L-2019-LLA-0236)

Dear Mr. Stoddard:

By letters dated October 30, 2019 (Agencywide Documents Access and Management System (ADAMS) Accession Nos. ML19309D196 and ML19309D197), Dominion Energy Virginia (Dominion), submitted license amendment requests for Surry Nuclear Power Station (Surry),

Units 1 and 2, and North Anna Power Station (North Anna), Units 1 and 2, respectively. The proposed amendments request to add Westinghouse Topical Report WCAP-16996-P-A, Revision 1, to the list of analytical methods included in the Core Operating Limits Report for each plant.

To support its review of the LAR, the U.S. Nuclear Regulatory Commission (NRC) staff conducted a regulatory audit via internet-based portal from June 10 to August 10, 2020, to verify information needing to be submitted on the docket supporting the amendment requests. The regulatory audit summary is provided as an attachment to this letter.

If you have any questions, please contact me by telephone at (301) 415-5897 or by e-mail at Vaughn.Thomas@nrc.gov.

Sincerely,

/RA/

Vaughn V. Thomas, Project Manager Plant Licensing Branch II-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket Nos. 50-280 and 50-281; 50-338 and 50-339

Enclosure:

Audit Summary cc: Listserv

REGULATORY AUDIT

SUMMARY

FOR THE JUNE 10 - AUGUST 10, 2020 AUDIT IN SUPPORT OF THE REVIEW OF LICENSE AMENDMENT REQUEST FOR USE OF FULL SPECTRUM LOSS-OF-COOLANT ACCIDENT METHODOLOGY DOMINION ENERGY VIRGINIA SURRY POWER STATION, UNITS 1 AND 2 DOCKET NOS. 50-280 AND 50-281 AND NORTH ANNA POWER STATION, UNITS 1 AND 2 DOCKETS NOS. 50-338 AND 50-339

1.0 BACKGROUND

By letters dated October 30, 2019 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML19309D196), and (ADAMS Accession No. ML19309D197),

Dominion Energy (the licensee) submitted license amendment requests (LARs) for Surry Power Station (Surry), Units 1 and 2, and the North Anna Power Station (North Anna), Units 1 and 2, respectively. The proposed amendments request to add Westinghouse Topical Report WCAP-16996-P-A, Revision 1, Realistic LOCA [Loss-of-Coolant Accident] Evaluation Methodology Applied to the Full Spectrum of Break Sizes (FULL SPECTRUM LOCA

[FSLOCA'] Methodology), (ADAMS Accession No. ML17277A130) to the list of analytical methods included in Core Operating Limits Report (COLR) for each plant.

The scope of the audit was focused primarily on the review of the licensees calculations related to its FSLOCA TM methodology to determine if the licensee needs to submit any additional information contained in the analyses performed in support of the requested change to support or develop conclusions for the NRC staffs safety evaluation. The proposed amendment would revise the Technical Specifications (TSs) for both Surry and North Anna for the use of the FSLOCA' methodology. The U. S. Nuclear Regulatory Commission (NRC) staff reviewed the calculations associated with the FSLOCA' analysis in support of this amendment via an internet-based portal. An audit plan was issued by the NRC staff by letter dated April 17, 2020, (ADAMS Accession No. ML20099F873).

Enclosure

2.0 AUDIT DATES AND LOCATION The regulatory audit was conducted via internet portal from June 10, 2020to August 10, 2020.

3.0 AUDIT TEAM MEMBERS The NRC audit team members consisted of:

• Mr. Vaughn Thomas, Project Manager, NRR

• Mr. Ed Miller, Project Manager, NRR

• Mr. Fred Forsaty, Reactor Engineer, NRR 4.0 DOCUMENTS AUDITED The calculation notes and supporting calculations for the proposed Technical Specification (TS) change were reviewed as part of the audit. A list of the topics discussed during the audit are provided as an Attachment to the audit plan. The NRC staff did not review any additional documents during the audit and did not remove or download any documents from the audit portal site and/or electronic document reading room.

5.0 AUDIT ACTIVITIES During the audit, the NRC staff discussed the information requested in the audit plan with the licensee. The technical discussions focused on two major areas:

1. Separability of Regions I and II of the FSLOCA'- The Surry and North Anna analyses were performed by the licensee in accordance with the NRC-approved methodology in the Westinghouse Topical Report, WCAP-16996-P-A, Revision 1 (ADAMS Accession No. ML17277A130). The analyses were performed assuming scenarios involving (1) the loss of outside power (LOOP) and (2) the offsite power available (OPA). The NRC approval of the FSLOCA' EM implicitly dictates that the normal approach is to perform analyses for both Small Break LOCA (Regions I) and Large Break LOCA (Region II.) However, the FSLOCA' methodology divides the break spectrum into two regions, and independent analyses are performed to determine results within each region. Therefore, given that the FSLOCA' analyses for Region I and Region II are separable, and do not influence each other.

2. North Anna, Units 1 and 2 - Limitation and Condition 2 - Applicability with Regard to Type of PWR Plants - the error impacting the gamma redistribution multiplier causing a power increase in the hot rod and the hot assembly.

In its letter dated October 30, 2019 (ADAMS Accession No. ML19309D197) the licensee stated that North Anna, Units 1 and 2, are Westinghouse-designed 3-loop pressurized water reactors (PWRs) with cold-side injection, so they are within the NRC-approved methodology. The analysis for North Anna utilizes the NRC-approved FSLOCA' methodology, with the following exceptions.

After completion of the analysis for North Anna three errors were discovered in the WCOBRA/TRAC-TF2 Code. The first error was regarding the calculation of radiation heat transfer to liquid. The second error was regarding vapor temperature resetting.

Here, the vapor temperature could incorrectly be reset to the saturation temperature for heat transfer calculations. The licensee stated in the LAR (ADAMS Accession No. ML19309D197) that these two errors were found to have a negligible impact on analysis results. In the Audit, the NRC staff confirmed independently those error corrections.

The third error impacted the gamma energy redistribution multiplier and was identified after completion of the analysis for North Anna. The Gamma ray error was not originally identified in the LAR. In response to the audit finding, the licensee voluntarily submitted a supplement (ADAMS Accession No ML20244A336) indicating that this error has been resolved. The treatment for the uncertainty in the gamma energy redistribution is discussed on pages 29-75 and 29-76 of the Westinghouse Topical Report, WCAP-16996-P-A, Revision 1 (ADAMS Accession No. ML17277A130). The power increase in the hot rod and hot assembly due to energy redistribution in the application of the FSLOCA' to North Anna was not initially calculated correctly by the licensee.

This error resulted in up to about a 5% deficiency in the hot rod and hot assembly rod linear heat rates on a run-specific basis, depending on the as-sampled value for the multiplier uncertainty.

During the audit and in its supplemental response (ADAMS Accession No ML20244A336), the licensee stated that this error only had a limited impact on the power modeled for a single assembly in the core and the error correction had a negligible impact on the system thermal-hydraulic response during the postulated LOCA for the Region II analysis. The PCT (peak clad temperature) impact from the error correction was found by the licensee to be different for the transient phases (i.e., blowdown versus reflood) based on parametric PWR sensitivity studies. The correction of the error was estimated to increase the Region II analysis PCT by 31 °F, leading to a final PCT analysis result of about 1893 °F for the North Anna Region II. The NRC staff reviewed the Region II analysis and additional information that were provided by the licensee during the audit and confirmed that the analysis results, with inclusion of the error correction, continue to demonstrate compliance with the 10 CFR 50.46 acceptance criteria.

In addition, the NRC staff also reviewed the major plant parameter and analysis assumptions used in the Surry and North Anna FSLOCA' EM.

6.0 AUDIT

SUMMARY

Based on the review of the calculations performed in support of the proposed change and provided for the NRC staff review via the internet portal, the NRC staff did not identify the need for the licensee to submit any additional information on the docket for Surry. Based on the above, a supplement (ADAMS Accession No ML20244A336) was submitted for North Anna.

7.0 EXIT BRIEFING The audit was performed via internet-based portal. Therefore, there was no need of a formal exit briefing.

ML20272A227 *via e-mail OFFICE NRR/DORL/LPL2-1/PM* NRR/DORL/LPL2-1/LA* NRR/DSS/SNSB/BC*

NAME VThomas KGoldstein SKrepel DATE 09/25/2020 09/29/2020 09/25/2020 OFFICE NRR/DORL/LPL2-1/BC* NRR/DORL/LPL2-1/PM*

NAME MMarkley VThomas DATE 10/23/2020 10/23/2020