ML24137A287

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Pre-Submittal Meetingfor Proposed License Amendment Request for Adoption of Technical Specification Task Force Traveler TSTF-276-A, Revision 2, Regarding TS 3.8.1 AC Sources - Operating to Clarify Requirements for Diesel Generator Testing
ML24137A287
Person / Time
Site: Watts Bar  Tennessee Valley Authority icon.png
Issue date: 05/16/2024
From:
Tennessee Valley Authority
To:
Office of Nuclear Reactor Regulation
Green K
References
EPID L-2024-LRM-0068 TSTF-276-A, TS 3.8.1
Download: ML24137A287 (1)
v • d • e


Text

Watts Bar Nuclear Plant Units 1 & 2

Pre-Submittal Meeting for Proposed License Amendment Request for Adoption of Technical Specification Task Force Traveler TSTF -276-A, Revision 2, Regarding TS 3.8.1 AC Sources -

Operating to Clarify Requirements for Diesel Generator Testing

May 20, 2024 Agenda Introduction

System Design and Operation

Existing Surveillance Requirements

Reason for Proposed Change

Proposed Changes to Technical Specification

Technical Evaluation

Regulatory Precedent

License Amendment Schedule

2 Introduction

  • TVA is submitting a license amendment request (LAR) for Renewed Facility Operating License Nos. NPF-90 and NPF -96 for Watts Bar Nuclear Plant (WBN), Units 1 and 2
  • Proposed revisions to SR 3.8.1.18 to allow for the surveillance to be performed in Modes 1, 2, 3, or 4 to reestablish operability provided an assessment of plant safety is performed
  • Proposed changes are consistent with NUREG-1431, Standard Technical Specifications (STS), Westinghouse Plants, Revision 5, and TSTF-276-A, Revision 2, Revise DG full load rejection test

l 3 System Design and Operation

  • The WBN Units 1 and 2 Alternating Current (AC) Electrical Power Distribution System AC sources consist of the offsite power sources (preferred power sources, normal, and alternate(s)), and the onsite standby power sources (Train A and Train B DGs).
  • As required by Title 10 of the Code of Federal Regulations (10 CFR) 50, Appendix A, General Design Criteria (GDC) 17, the design of the AC electrical power system provides independence and redundancy to ensure an available source of power to the Engineered Safety Feature (ESF) systems.
  • In the event of a loss of preferred power, the 6.9 kV shutdown boards are automatically connected to the DGs in sufficient time to provide for safe reactor shutdown and to mitigate the consequences of a design basis accident (DBA) such as a Loss of Coolant Accident (LOCA).
  • The onsite Class 1E AC Distribution System supplies electrical power to four power trains, shared between the two units, with each train powered by an independent Class 1E 6.9kV shutdown board. Each 6.9 kV shutdown board has two separate and independent offsite sources of power as well as a dedicated onsite DG source.

l 4 System Design and Operation

  • Additional DG capabilities must be demonstrated to meet required surveillances
  • SR 3.8.1.9 DG single largest load rejection test, SR 3.8.1.10 DG full load rejection test, and SR 3.8.1.14 DG endurance and margin test. These surveillances are performed with the DG synchronized with offsite power. When the DG is not synchronized with offsite power, the power factor is determined by plant load and cannot be adjusted.
  • SR 3.8.1.18 demonstrates sufficient load sequence time delay exists for the DG to restore frequency and voltage prior to applying the next load block and that safety analysis assumptions regarding ESF equipment time delays are not violated.

l 5 Existing Surveillance Requirements

  • SR 3.8.1.10 and SR 3.8.1.14 each have a required DG k VA R operating band during performance of the surveillance test.
  • SR 3.8.1.10 band is 2970 k VA R and 3300 k VA R for the entire surveillance test
  • SR 3.8.1.14 band is 3465 k VA R and 3630 k VA R for at least the first 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> and then 2970 k VA R and 3300 k VA R for the remainder of the surveillance test
  • Note for SR 3.8.1.18 states that this surveillance shall not be performed in Mode 1, 2, 3, or 4 and that credit may be taken for unplanned events that satisfy this SR.

l 6 Reason for Proposed Change

  • The k VA R requirements in the WBN Units 1 and 2 SRs 3.8.1.10 and 3.8.1.14 were added during the development of the initial Unit 1 TS
  • k VA R requirements for DG surveillances have never been included in Standard TS
  • When a DG is synchronized with offsite power, a power factor of 0.9 is representative of the inductive loading the DG would experience under design basis accident conditions
  • When the DG is not synchronized with offsite power, the power factor is determined by plant load and cannot be adjusted
  • Under certain grid conditions, the specified power factor may not be achievable
  • The proposed change allows the surveillances to be performed at a power factor as close as practicable to 0.9

l 7 Reason for Proposed Change

  • The proposed Note for SR 3.8.1.18 would allow performance of this the surveillance in Modes 1, 2, 3, or 4 to reestablish operability provided an assessment of plant safety is performed
  • Allows for flexibility in the performance of the surveillance with the appropriate considerations for the potential outcomes and transients associated with a failed surveillance, a successful surveillance, and a perturbation of the offsite or onsite system when they are tied together or operated independently for the surveillance; as well as the operator procedures available to cope with these outcomes.
  • The changes being proposed align the WBN Units 1 and 2 TS with TSTF-276-A, Revision 2, and the NUREG-1431, Revision 5, Standard TS relative to DG surveillance testing

l 8 Proposed Changes to Technical Specification Watts Bar Unit 1 is provided and typical of Watts Bar Unit 2

99 Proposed Change to Technical Specification Watts Bar Unit 1 is provided and typical of Watts Bar Unit 2

1010 Technical Evaluation

  • A power factor of 0.9 is normally achieved when performing this surveillance test while synchronized with offsite power
  • When grid voltage is higher than typical, the additional field excitation current required to achieve a power factor 0.9 results in ESF bus voltage exceeding the maximum steady state voltage limit.
  • Increased grid voltage typically occurs when the plant is shutdown and the loads on the associated ESF transformer are too light to lower the voltage and achieve a 0.9 power factor.
  • Under these conditions, the power factor would be maintained as close as practicable to a 0.9 power factor while still maintaining acceptable voltage limits on the ESF busses.
  • In other circumstances, the grid voltage may be such that the DG excitation levels needed to obtain a power factor of 0.9 may not cause unacceptable voltages on the emergency busses, but the excitation levels are greater than those recommended for the DG.
  • In such cases, the power factor would be maintained as close as practicable to 0.9 without exceeding DG excitation limits.

l 11 Technical Evaluation

  • To confirm that the proposed power factor of 0.9 represents a worst-case power factor for WBN Units 1 and 2, a review was performed of the calculated power factors for each DG during the limiting event of a loss of offsite power (LOOP) coincident with a LOCA.
  • The kW and kVA values associated with the limiting LOOP with a LOCA event time confirm that application of a 0.9 power factor is appropriate for WBN.
  • The change to Note for SR 3.8.1.18 allows performance of this surveillance in Modes 1, 2, 3, or 4 to reestablish operability provided an assessment of plant safety is performed.
  • Measured against the avoided risk of a plant shutdown and startup to determine that plant safety is maintained or enhanced when the surveillance is performed in MODE 1, 2, 3, or 4.

l 12 Regulatory Precedent

  • The following licensees have submitted similar license amendment requests which have been reviewed and approved by the NRC

l 13 License Amendment Schedule

Pre-submittal Meeting with NRC May 20, 2024

Submit LAR to NRC June 28, 2024

Requested NRC Review and Approval June 2025

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