ML20153A362
| ML20153A362 | |
| Person / Time | |
|---|---|
| Site: | Watts Bar  |
| Issue date: | 06/22/2020 |
| From: | Kimberly Green Plant Licensing Branch II |
| To: | Jim Barstow Tennessee Valley Authority |
| Green K | |
| References | |
| EPID L-2020-LRM-0031 | |
| Download: ML20153A362 (5) | |
Text
June 22, 2020 LICENSEE:
Tennessee Valley Authority FACILITY:
Watts Bar Nuclear Plant, Units 1 and 2
SUBJECT:
SUMMARY
OF MAY 27, 2020, TELECONFERENCE CALL WITH TENNESSEE VALLEY AUTHORITY REGARDING A PLANNED LICENSE AMENDMENT REQUEST FOR WATTS BAR NUCLEAR PLANT, UNITS 1 AND 2 (EPID L-2020-LRM-0031)
On May 27, 2020, a Category 1 public teleconference call was held between the U.S. Nuclear Regulatory Commission (NRC) staff and representatives of Tennessee Valley Authority (TVA).
The purpose of the meeting was to discuss TVAs planned license amendment request (LAR) for Watts Bar Nuclear Plant (WBN), Units 1 and 2. The LAR would seek to revise WBN Technical Specification (TS) 3.3.2, Table 1 Function 6.e Auxiliary Feedwater Auto -Start from Loss of Main Feedwater Pumps.
The meeting notice and agenda, dated April 24, 2020, are available at Agencywide Documents Access and Management System (ADAMS) Accession No. ML20148M224. TVAs slides for the meeting are available at ADAMS Accession No. ML20148M145. A list of participants is provided as an enclosure to this summary. No regulatory decisions were made at this meeting.
TVA began its presentation by stating that the meeting was not a pre-submittal meeting, but due to the regulatory history of the issue, TVA wanted to seek early NRC staff engagement and feedback on the proposed TS change. TVA will schedule a pre-submittal meeting prior to submitting the LAR for August 2020.
TVA described the function and operation of main feedwater system, including the standby main feedwater pump (SBMFP). The WBN main feedwater supplies a sufficient quantity of feedwater to the steam generator (SG) secondary side during plant normal operating conditions. It consists of two turbine driven main feed pumps (TDMFPs) arranged in parallel with a single SBMFP, two injection water pumps, three (parallel string) high-pressure feedwater heaters, and associated piping and instrumentation. The two TDMFPs, each having a capacity of 67 percent, are capable of delivering feedwater to the four steam generators under all expected operating conditions. The electric motor-driven SBMFP can provide approximately 15 to 18 percent capacity. During certain times of the year, to improve plant efficiency, the SBMFP is used to supplement the TDMFP flow at high plant loads.
As explained by TVA, the original design basis for WBN allowed the SBMFP to be used for normal plant startup and shutdown (up to 15 percent thermal power) while TDMFPs were being placed into or removed from service. This is described in NUREG-0847, Safety Evaluation Report Related to the Operation of Watts Bar Nuclear Plant, Units 1 and 2 Docket Nos. 50-390 and 50-391, (ADAMS Accession No. ML072060490) Section 10.4.7, which states, in part, The use of the standby feedwater pump is the normal means for starting up and shutting down the plant. This pump is also automatically activated in the event of the loss of one main feedwater pump.
TVA reviewed the regulatory history of the SBMFP, which dates back to a 2004 LAR that was subsequently withdrawn in 2006. The LAR sought to allow the auxiliary feedwater (AFW) start upon trip of TDMFP function to be required only when the one or more of TDMFPs are operating. The NRC documented concerns on the use of the SBMFP for reactor startup beginning in 2006 because the SBMFP does not interface to the AFW automatic start logic.
The NRC issued non-cited violations in 2006 and 2008 (NRC Inspection Reports 2006-004 and 2008-003). TVA submitted a LAR in 2008 to address the concerns and requested that the AFW motor driven pumps and the TDMFPs be used for normal plant startup and shutdown. The LAR was approved, which added a note to the current TS 3.3.2, Table 1 Function 6.e to allow the licensee to test, place into, or remove from service the TDMFW pumps without an auto start of the AFW pumps.
TVA explained that it wants to change Function 6.e because controlling SG water level and feedwater control during startup using AFW motor driven pumps at low reactor thermal power can be challenging. Feedwater swings affect temperature and power, which is not ideal at low powers when there are tight control bands. TVA places a TDMFP in service at around 4 percent reactor thermal power (RTP), but the use of the TDMFP is more suitable at a higher reactor thermal power. TVA proposes to use the SBFMP to provide feedwater flow from Mode 3 to Mode 1, or about 15 percent RTP. At approximately 15 RTP, a TDMFP would be placed in service in Mode 1 to control SG water levels, and the SBMFP would be removed from service. TVA stated that the use of the SBMFP during start up activities would simplify startup activities.
To make the change, TVA proposes to revise the AFW auto-start logic by adding a SBMFP power supply breaker contact interface to the AFW auto-start logic. The AFW auto-start logic will initiate from the trip of both TDMFPs and the SBMFP. TVA explained that the SBMFP trip channel will be provided with a manual trip enable switch that allows operators to enable the trip when the SBMFP is the only supply of feedwater to the SGs. When one or more TDMFPs are supplying feedwater to the steam generators, the SBMFP trip enable switch will be taken to the bypass position, which places that channel in the tripped position effectively removing the trip from the circuitry. The revised circuitry will remain as an anticipatory AFW auto-start function and will not be credited in the WBN accident analyses. The NRC staff asked if any of the accident analyses take anticipatory TDMFP tip circuitry into account or only assume AFW start on low-low SG level. TVA stated that analyses only assume a start of the AFW pumps on a low-low SG level. The NRC staff asked if any updated final safety analysis report analyses credit the start function of the SBMFP. TVA stated that no credit is given for the 6.e auto-start function.
TVA plans to submit the LAR in September 2020.
No comments or public meeting feedback were received.
Please direct any inquiries to me at 301-415-1627, or Kimberly.Green@nrc.gov.
/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:
List of Participants cc: Listserv
Enclosure LIST OF PARTICIPANTS MAY 27, 2020, PUBLIC TELECONFERENCE CALL TENNESSEE VALLEY AUTHORITY REGARDING PLANNED LICENSE AMENDMENT REQUEST WATTS BAR NUCLEAR PLANT, UNITS 1 AND 2 Name Organization Kim Green U.S. Nuclear Regulatory Commission (NRC)
Steve Smith NRC Calvin Cheung NRC Bruce Heida NRC Vic Cusumano NRC Brian Wittick NRC Russell Wells Tennessee Valley Authority (TVA)
Tony Langley TVA Tony Brown TVA Roger Scott TVA Andy Taylor TVA James Shea TVA Chris Kerlin TVA Tim Mingus TVA Ron Rogers TVA Jason Gasque TVA Ron Jarrett Member of the Public
- via email OFFICE NRR/DORL/LPL2-2/PM NRR/DORL/LPL2-2/LA* NRR/DORL/LPL2-2/BC* NRR/DORL/LPL2-2/PM NAME KGreen BAbeywickrama UShoop KGreen DATE 06/03/2020 06/01/2020 06/19/2020 06/22/2020