ML18248A101
| ML18248A101 | |
| Person / Time | |
|---|---|
| Site: | Watts Bar  |
| Issue date: | 09/05/2018 |
| From: | Tennessee Valley Authority |
| To: | Shea J W, Skaggs M D Tennessee Valley Authority |
| References | |
| Download: ML18248A101 (25) | |
Text
Watts Bar Nuclear Plant (WBN)Pre-Submittal Meeting for Proposed License Amendment Adoption of TSTF-500 September 6, 2018
- Opening Remarks*Watts Bar Vital Direct Current (DC) Electrical Design
- Proposed Technical Specification (TS) Changes
- Variations from TSTF-500 and Model Safety Evaluation
- TSTF-500 Options
- Commitments
- Schedule for Submittal
- Summary and Closing Remarks Agendal 2 Opening Remarks*Due to WBN Unit 1 and Unit 2 sharing the DC electrical power system, performing maintenance on an Alternating Current (AC) electrical power distribution subsystem (6.9 kilovolt (kV) shutdown board and associated 480 volt (V) shutdown boards) for a shutdown unit also affects the operating unit.*Irrespective of inverter operability, the current two-hour completion time for an inoperable vital battery subsystem does not support maintenance on a set of 6.9 kV/480 V shutdown boards. *The license amendment request (LAR) will adopt TSTF-500, thereby providing a separate Condition for an inoperable vital battery charger.
This change will extend the completion time for restoring an inoperable vital battery charger from two hours to seven days.
l 3 Watts Bar Vital DC Electrical Design*The onsite Class 1E AC electrical distribution system supplies electrical power to two power trains shared between the two units.*The 125 VDC vital control power system is composed of four channels (Channels I, II, III, and IV) in two trains (Channels I and III in Train A and Channels II and IV in Train B.*Vital Battery Boards I, II, III, and IV have manual access to two spare (backup) chargers for use upon loss of the normal charger.*Vital Battery Boards I, II, III, and IV have manual access to a fifth 125 VDC Vital Battery System, that serves as a replacement for any one of the four 125 VDC vital batteries during testing, maintenance, and outages with no loss of system reliability under any mode of
operation.
l 4 Watts Bar Vital DC Electrical Design l 5 Watts Bar DG DC Subsystems*A DG battery subsystem is provided for each DG. Each subsystem is comprised of a battery, dual battery charger assembly, distribution center, and cabling. The DG battery provides DC control power and field-flash when the charger
is unavailable.*If 480V AC is available, the charger supplies the normal DC loads, maintains the battery in a fully charged condition, and recharges the battery while supplying the required loads regardless of the status of the plant.*Each DG battery has sufficient capacity when fully charged to supply the required loads for a minimum of four-hours following a loss of normal power.
l 6 Watts Bar DG DC Subsystems (Cont.)*Each of the chargers (normal and alternate) in the dual charger assembly has a dedicated AC source from two respective 480 VAC Diesel Generator Auxiliary Boards. If the normal charger is unavailable, the alternate charger is selected by the 125 VDC transfer switch included in the assembly.l 7 Proposed WBN 1 TS 3.8.4 Changes (similar for WBN 2) l 8 Proposed WBN 1 TS 3.8.4 Changes (Continued) (same for WBN 2) l 9 Proposed WBN 1 TS 3.8.4 Changes (Continued) (same for WBN 2)l 10 Proposed WBN 1 TS 3.8.4 Changes (Continued) (same for WBN 2)l 11 Proposed WBN 1 TS 3.8.5 Changes (same for WBN 2)l 12 Proposed WBN 1 TS 3.8.5 Changes (Continued) (same for WBN 2)l 13 Proposed WBN 1 TS 3.8.6 Changes (same for WBN 2)l 14 Proposed WBN 1 TS 3.8.6 Changes (Continued) (same for WBN 2)l 15 Proposed WBN 1 TS 3.8.6 Changes (Continued) (same for WBN 2)l 16 Proposed WBN 1 TS 3.8.6 Changes (Continued) (same for WBN 2)l 17 Proposed New WBN 1 TS, "Battery Monitoring and Maintenance Program" (same for WBN 2)l 18 Variations from TSTF-500 and Model SE*Current Limiting Condition for Operation (LCO) 3.8.4 refers to 'four Channels of vital DC.' The proposed change refers to 'Train A and Train B vital DC electrical power subsystems' to align the WBN TS to TSTF-500 and NUREG-1431. The proposed changes also make the LCO consistent with current Action statements that refer to subsystems.*WBN TS includes requirements for DG DC electrical power subsystems. The proposed changes also apply the TSTF-500 changes to the DG DC electrical power subsystems. This variation requires separate Actions and Surveillance Requirements where necessary to reflect the design differences.*WBN Units 1 and 2 designed with a fifth qualified vital battery. Therefore, proposed changes include addition of the word "required" to indicate that only four of the five vital batteries are required to be operable in Modes 1 through 4.*WBN Unit 1 LCO 3.8.4 and LCO 3.8.5 Notes refer to substituting the C-S DG and associated DC subsystems for any required DG and associated DC subsystem. These notes are being removed, consistent with WBN Unit 2 TS and change made to WBN Unit 1 LCO 3.8.1 Note in Amendm ent 84 (dated July 6, 2010).*These variations do not affect the applicabilit y of the published Model Safety Evaluation (SE).l 19 TSTF-500 Options*TVA is proposing a Completion Time longer than 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> for restoring an inoperable vital battery charger to operable status.*TVA is notrequesting a Completion Time longer than 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> for restoring an inoperable DG battery charger to operable status.*TVA is notrequesting a Completion Time longer than 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> to restore battery float current with one or two required battery chargers on one subsystem inoperable.*TVA is notrequesting a Completion Time longer than 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> for one or two batteries on one subsystem inoperable.*TVA is requesting adoption of new LCO 3.8.5, Condition A, as the potential exists to require both vital DC electrical power subsystems during a portion of the LCO 3.8.5 Applicability.*These variations do not affect the applicability of the published Model SE.l 20 CommitmentsTVA is planning to include the following regulatory commitments in the LAR, as prescribed in TSTF-500, Revision 2:*Include in the FSAR a requirement to maintain a 2 percent design margin for the vital batteries which corresponds to a 2 amp fl oat current value that is an indication that the battery is 98 percent charged.*Include in the FSAR a requirement to maintain a 2 percent design margin for the DG batteries which corresponds to a 1 amp float current value that is an indication that the battery is 98 percent charged.*The licensee-controlled program, required and described in TS Section 5.7.2, "Programs and Manuals," and titled, "Battery Monitoring and Maintenance Program," will require verification of the selection of the pilot cell or cells when performing SR 3.8.6.5.*A licensee-controlled program will require the availability of a means to charge the batteries that is capable of being supplied power from a power source that is independent of the offsite power supply.l 21 Schedule for Submittal*September 2018 -Pre-submittal meeting with NRC*October 2018 -Submit LAR to NRC
- Request NRC approval by October 2019 with a 90-day implementation period to support the WBN Unit 1 outage scheduled for Spring 2020 (U1R16).*December 2018 -Telecon or meeting to discuss any NRC questionsl 22 Summaryl 23The proposed TS adopts TSTF-500 and adds completion times for inoperable vital and DG DC
battery chargers.
Closing Remarks*Proposed LAR is needed to support a two-unit operating site at WBN.*Due to the commonality of the AC electrical power systems, performing maintenance on 6.9 kV (and associated 480 V) shutdown boards for a shutdown unit affects operability on the
operating unit.*The LAR will extend the completion times for inoperable vital and DG DC battery chargers and moves the battery preventative maintenance requirements to the Battery Monitoring and
Maintenance Program.*This LAR is needed to support the WBN Unit 1 outage scheduled for Spring 2020.l 24