ML24204A265

Regulatory Audit Summary Related to Request to Revise Technical Specification Surveillance Requirement 3.9.5.1 to Reduce the Residual Heat Removal Flow Rate

ML24204A265
Person / Time
Site:	Watts Bar
Issue date:	07/25/2024
From:	Kimberly Green NRC/NRR/DORL/LPL2-2
To:	Jim Barstow Tennessee Valley Authority
Green K, NRR/DORL/LPL2-2
References
EPID L-2023-LLA-0152
Download: ML24204A265 (1)

Text

July 25, 2024

James Barstow Vice President, Nuclear Regulatory Affairs and Support Services Tennessee Valley Authority 1101 Market Street, LP 4A-C Chattanooga, TN 37402-2801

SUBJECT:

WATTS BAR NUCLEAR PLANT, UNITS 1 AND 2 - REGULATORY AUDIT

SUMMARY

RELATED TO REQUEST TO REVISE TECHNICAL SPECIFICATION SURVEILLANCE REQUIREMENT 3.9.5.1 TO REDUCE THE RESIDUAL HEAT REMOVAL FLOW RATE (EPID L-2023-LLA-0152)

Dear James Barstow:

By letter to the U.S. Nuclear Regulatory Commission (NRC) dated October 30, 2023, as supplemented by letter dated January 10, 2024, the Tennessee Valley Authority (TVA) submitted a license amendment request to revise Watts Bar Nuclear Plant, Units 1 and 2, Technical Specification Surveillance Requirement 3.9.5.1 to revise the minimum required flow rate for circulating reactor coolant with one residual heat removal loop in operation from 2,500 gallons per minute (gpm) to 2,000 gpm.

To enhance the review of TVAs request, the NRC staff conducted an audit of supporting documents from April 29 to May 2, 2024. The staff audited the requested documents to confirm certain information relied upon in the license a mendment request. A summary of the regulatory audit is enclosed.

J. Barstow - 2 -

The NRC staff did not identify any significant iss ues during the audit; however, it identified the need for additional information related to the topic of the audit.

Sincerely,

/RA/

Kimberly J. Green, Senior Project Manager Plant Licensing Branch II-2 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation

Docket Nos. 50-390 and 50-391

Enclosure:

Regulatory Audit Summary

cc: Listserv REGULATORY AUDIT

SUMMARY

RELATE D TO LIC ENSE AMENDMENT REQUEST

REGARDING TEC HNICAL SPECIFICATION SURVEILLANCE REQUIRE MENT 3.9.5.1 TO

REDUCE THE RESIDUAL HEAT REMOVAL FLOW RATE

TENNESSEE VALLEY AUTHORITY

WATTS BAR NUCLEAR PLANT, UNITS 1 AND 2

DOCKET NOS. 50-390 AND 50-391

1.0 BACKGROUND

A regulatory audit is a planned license or regulation-related activity that includes the examination and evaluation of docketed and non-docketed information. The audit was conducted with the intent to gain understanding, to verify information, and to identify information that will require docketing to support the basis of a licen sing or regulatory decision.

By application dated October 30, 2023 (Agencywide Documents Access and Management System Accession No. ML23303A095), as supplemented by letter dated January 10, 2024 (ML24010A064), pursuant to Section 50.90 of Title 10 of the Code of Federal Regulations (10 CFR), the Tennessee Valley Authority (TVA) submitted a license amendment request (LAR) to amend Facility Operating License Nos. NPF-90 and NPF-96 for Watts Bar Nuclear Plant (Watts Bar), Units 1 and 2, respectively. The proposed amendments would revise Watts Bar, Units 1 and 2, Technical Specification (TS) Surveillance Requirement (SR) 3.9.5.1 to revise the minimum required flow rate for circulating reactor coolant with one residual heat removal (RHR) loop in operation from 2,500 gallons per minute (gpm) to 2,000 gpm.

The Nuclear Regulatory Commission (NRC) staff performed a preliminary review of the LAR and determined that a regulatory audit would assist in the timely completion of the review. The regulatory audit was performed consistent with NRC Office of Nuclear Reactor Regulation Office Instruction LI C-111, Revision 1, Regulatory A udits, d ated October 3 1, 2 019 ( ML19226A274).

2.0 AUDIT ACTIVITIES AND OBSERVATIONS

The NRC staff conducted a remote regulatory audit from April 29 to May 2, 2024, using an online portal. An audit plan was provided to TVA on March 7, 2024 (ML24071A098). The list of documents requested by the NRC staff is provided in Section 4.0 below. The documents were uploaded to a portal by Westinghouse Electric Company, LLC, on behalf of TVA.

The purpose of the audit was to (1) gain a better understandi ng of the supporting calculations, analyses, and bases underlying the LAR and confir m the NRC staffs understanding of the LAR, and (2) identify any information that would be required from the licensee to be provided on the docket for the NRC to render a staff finding to support the safety evaluation.

Enclosure

- 2 -

The NRC staff examined the documents identified in Section 4.0 below. The NRC staff audited the documents to confirm that TVA had conducted specific technical evaluations of the potential effects on the performance of the associated components in support of the LAR for the proposed reduction of the required minimum RHR system flow rate. The technical evaluations contained in the documents addressed such performance aspects as decay heat removal, thermal stratification, boron mixing and stratification, potential control valve cavitation, check valve chattering, and RHR pump motor thrust bearing seismic capability and life. A brief description of the documents that were audited is provided below.

1. Memorandum from NATD Fluid System & Suppo rt Engineering, FSSE/CWBS-1145,

Subject:

RHRS Operation During Midloop at Watts Bar, dated December 7, 1989.

This document includes an evaluation of operation of the RHR system at Watts Bar during mid-loop operation. The document also includes comments by Westinghouse on the evaluation.

2. Letter from Westinghouse Electric Company, Outage & Maintenance Services, LTR-RES-21-76, to Mark Balsemo,

Subject:

Watts Bar Residual Heat Removal (RHR)

Pump Motor Bearing Life, dated July 6, 2021. Westinghouse Proprietary Class 2.

This document provides an evaluation of the bearing L-10 lif e for the Watts Bar pump motors under qualified design loads.

3. Seismic Analysis of Residual Heat Removal Pump Motors for Watts Bar No. 1 & No. 2 Nuclear Stations, Tennessee Valley Authority, by Buffalo - Large Motor Division, dat ed May 30, 1975.

This document provides an analysis to qualify the RHR pu mp motors for seismic conditions. The document includes the determination of the natural frequencies for t he RHR pump motors and indicates margin for stress and rotor deflection.

4. Westinghouse Electric Company, WAT-D-8252, Tennessee Valley Authority, Wa tts Bar Nuclear Plant, Unit Numbers 1 and 2, Minimum RHRS Flowrate Reduction During Midloop Operation Safety Evaluatio n (SECL-89-893), dated June 11, 19 90.

Westinghouse Proprietary Class 2C.

This document provides a safety evaluation of the reduction in minimum RHR system flowrate during mid-loop operation. T he document provides recommendati ons for monitoring components during the in itial implementation of the lower RHR flowrates, and replacement intervals for the motor thrust bearings.

5. Equipment Specification 678815, Class 2 Pu mps-Based on [American Society of Mechanical Engineers] ASME Boiler and Pressure Vessel Code Section III - Rules for Construction of Nuclear Power Plant Components, Revision 2, dated September 6, 1973. Westinghouse Proprietary Class 2.

This document provides the specification t hat establishes the design, performance, manufacture, inspection, testing, packaging, shipping, and installation re quirements for ASME Boiler and Pressure Vessel Code, Class 2 pumps.

- 3 -

6. Westinghouse Electric Company, WNEP-8402, Generic Stress Report of 3 Loop XL Reactor Core Support Structures - S tructural and Fatigue Analysis, Revision 0, Westinghouse Proprietary Class 2.

This document provides generic structural and fatigue analyses of nuclear reactor core support structures for 3-Loop XL plants. The document describes the analysis perform ed and documented in accordance with the ASME Boiler and Pr essure Vessel Code,Section III, Division 1, and design specificat ions.

The NRC staff held an audit exit call with members of TVA and Westinghouse on May 2, 2024.

At the conclusion of the audit, the NRC staff determined that additional information would be needed for the staff to complete the review of the LAR. The request for additional information was transmitted to TVA by email dated May 29, 2024 (ML24155A137).

3.0 AUDIT PARTICIPANTS

NRC TVA Westinghouse

Jo Ambrosini Russell Wells James Smith Ahsan Sallman Stuart Rymer Michael Francis Thomas Scarbrough Sara Nolan Gary Whiteman Matthew Hamm Christopher Kerlin Mike Asztalos Kim Green Jonathan Durfee

4.0 DOCUMENTS PROVIDED IN ELECTRONIC READING ROOM

1. Memo from NATD Fluid System & Support Engineering, FSSE/CWBS-1145,

Subject:

RHRS Operation During Midloop at Watts Bar, dated December 7, 1989.

a. Memo from Commercial Fuel Division, THFL-89-546, to G.G. Konopka,

Subject:

Watts Bar Reduced RHR Flow Du ring Midloop Operation, dated September 6, 1989. Westinghouse Proprietary Class 2.

b. Memo from Mechanical Equipment Design, MED-AEE-291 3, to L. Tomasic,

Subject:

Evaluation of Mid Loop Operation on Valves at WA T, dated October 5, 1989.

2. Letter from Westinghouse Electric Company, Outage & Maintenance Services, LTR-RES-21-76, to Mark Balsemo,

Subject:

Watts Bar Residual Heat Removal (RHR)

Pump Motor Bearing Life, dated July 6, 2021. Westinghouse Proprietary Class 2.

3. Seismic Analysis of Residual Heat Removal Pump Motors for Watts Bar No. 1 & No. 2 Nuclear Stations, Tennessee Valley Authority, by Buffalo - Large Motor Division, dat ed May 30, 1975.

4. Westinghouse Electric Company, WAT-D-8252, Tennessee Valley Authority, Wa tts Bar Nuclear Plant, Unit Numbers 1 and 2, Minimum RHRS Flowrate Reduction During Midloop Operation Safety Evaluatio n (SECL-89-893), dated June 11, 19 90.

Westinghouse Proprietary Class 2C.

5. Equipment Specification 678815, Class 2 Pumps-Based on ASME Boiler and Pressure Vessel Code Section III - Rules for Construction of Nuclear Power Plant Components, Revision 2, dated September 6, 1973. Westinghouse Proprietary Class 2.

6. Westinghouse Electric Company, WNEP-8402, Generic Stress Report of 3 Loop XL Reactor Core Support Structures - Structural and Fatigue Analysis, Revision 0.

Westinghouse Proprietary Class 2.

ML24204A265 *via email NRR-106 OFFICE NRR/DORL/LPL2-2/PM* NRR/DORL/LPL2-2/LA NRR/DSS/SNSB/BC NAME KGreen ABaxter PSahd DATE 07/22/2024 07/23/2024 07/23/2024 OFFICE NRR/DEX/EMIB/BC NRR/DORL/LPL2-2/BC NRR/DORL/LPL2-2/PM NAME SBailey DWrona (BPurnell for) KGreen DATE 07/22/2024 07/24/2024 07/25/2024