ML19218A028

NRR E-mail Capture - Watts Bar Nuclear Plant - Draft Second-Round Request for Additional Information Related to Application to Revise Technical Specifications Regarding DC Electrical Systems, TSTF-500, Revision 2

ML19218A028
Person / Time
Site:	Watts Bar
Issue date:	07/25/2019
From:	Robert Schaaf Plant Licensing Branch II
To:	Wells R Tennessee Valley Authority
References
L-2018-LLA-0494
Download: ML19218A028 (7)

Text

NRR-DRMAPEm Resource From: Schaaf, Robert Sent: Thursday, July 25, 2019 10:18 AM To: 'Wells, Russell Douglas' Cc: Hulvey, Kimberly Dawn; 'Edmondson, Carla'; Shoop, Undine; Wentzel, Michael; Saba, Farideh

Subject:

Watts Bar Nuclear Plant - Draft Second-Round Request for Additional Information Related to Application to Revise Technical Specifications Regarding DC Electrical Systems, TSTF-500, Revision 2 (EPID L-2018-LLA-0494)

Attachments: Watts Bar TSTF-500 Draft Second Round RAIs (L-2018-LLA-0494).pdf

Russ, By letter dated November 29, 2018 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML18334A389), as supplemented by letter dated June 7, 2019 (ADAMS Accession No. ML19158A394), the Tennessee Valley Authority (TVA) submitted a license amendment request for the Watts Bar Nuclear Plant (Watts Bar), Units 1 and

2. The requested amendments would modify TS requirements related to direct current (DC) electrical systems in accordance with Technical Specification Task Force (TSTF) Traveler TSTF-500, Revision 2, DC Electrical Rewrite - Update to TSTF-360.

The licensees letter dated June 7, 2019, responded to a U.S. Nuclear Regulatory Commission (NRC) staff request for additional information (RAI) dated May 3, 2019 (ADAMS Accession No. ML19126A121). The staff has reviewed the licensees responses and has determined that additional information, as described in the attached second-round RAI, is needed to complete the review of the Watts Bar license amendment request.

This RAI is identified as draft at this time to confirm your understanding of the information that the NRC staff needs to complete its evaluation. The NRC staff proposes that TVA respond to this RAI within approximately 30 days of the date of this request (i.e, by August 23, 2019).

The staff is evaluating the effect of this second-round RAI on the current planned completion date for the review of November 2019 and may determine that additional time is needed to complete the review. We will inform TVA promptly of any review schedule impact determination.

Please call me at 301-415-6020 or Michael Wentzel at 301-415-6459 to set up a teleconference to clarify this request or to discuss an alternative schedule for TVAs response, as needed. If TVA determines that a clarification teleconference regarding the draft second-round RAI is needed, it should be requested to occur within approximately 5 business days of this e-mail transmittal.

Regards, Robert G. Schaaf Senior Project Manager

====================

U.S. Nuclear Regulatory Commission Office of Nuclear Reactor Regulation Division of Operating Reactor Licensing Mail Stop O-8B1A

====================

301-415-6020 Robert.Schaaf@nrc.gov 1

2 Hearing Identifier: NRR_DRMA Email Number: 157 Mail Envelope Properties (BY5PR09MB4309FAE537A7FEF4CED2E6CBF9C10)

Subject:

Watts Bar Nuclear Plant - Draft Second-Round Request for Additional Information Related to Application to Revise Technical Specifications Regarding DC Electrical Systems, TSTF-500, Revision 2 (EPID L-2018-LLA-0494)

Sent Date: 7/25/2019 10:18:12 AM Received Date: 7/25/2019 10:18:16 AM From: Schaaf, Robert Created By: Robert.Schaaf@nrc.gov Recipients:

"Hulvey, Kimberly Dawn" <kdhulvey@tva.gov>

Tracking Status: None

"'Edmondson, Carla'" <cedmondson@tva.gov>

Tracking Status: None "Shoop, Undine" <Undine.Shoop@nrc.gov>

Tracking Status: None "Wentzel, Michael" <Michael.Wentzel@nrc.gov>

Tracking Status: None "Saba, Farideh" <Farideh.Saba@nrc.gov>

Tracking Status: None

"'Wells, Russell Douglas'" <rdwells0@tva.gov>

Tracking Status: None Post Office: BY5PR09MB4309.namprd09.prod.outlook.com Files Size Date & Time MESSAGE 2310 7/25/2019 10:18:16 AM Watts Bar TSTF-500 Draft Second Round RAIs (L-2018-LLA-0494).pdf 119376 Options Priority: Standard Return Notification: No Reply Requested: No Sensitivity: Normal Expiration Date:

Recipients Received:

DRAFT REQUEST FOR ADDITIONAL INFORMATION REGARDING LICENSE AMENDMENT REQUEST TO ADOPT TECHNICAL SPECIFICATIONS TASK FORCE (TSTF) TRAVELER TSTF-500, REVISION 2, DC ELECTRICAL REWRITE - UPDATE TO TSTF-360 TENNESSE VALLEY AUTHORITY WATTS BAR NUCLEAR PLANT, UNITS 1 AND 2 DOCKET NOS. 50-390 AND 50-391

Background

By letter dated November 29, 2018 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML18334A389), as supplemented by letter dated June 7, 2019 (ADAMS Accession No. ML19158A394), Tennessee Valley Authority (the licensee), requested an amendment to Facility Operating Licenses NPF-90 and NPF-96 for Watts Bar Nuclear Plant (WBN), Units 1 and 2. The proposed license amendment request would revise the WBN Units 1 and 2 Technical Specifications (TSs) to adopt Technical Specifications Task Force (TSTF) Traveler TSTF-500, Revision 2, "DC [direct current] Electrical Rewrite - Update to TSTF-360 (ADAMS Accession No. ML092670242). Specifically, the licensee proposed changes to the TS requirements related to DC electrical power systems in TS 3.8.4, DC sources - Operating, TS 3.8.5, DC Sources - Shutdown, and TS 3.8.6, Battery Cell Parameters. Additionally, the licensee proposed to add to the TS Section 5.7, Procedures, Programs, and Manuals, a new program titled Battery Monitoring and Maintenance Program.

The licensees letter dated June 7, 2019, responded to the Electrical Engineering Operating Reactors Branch (EEOB) staffs request for additional information (RAI) dated May 3, 2019 (ADAMS Accession No. ML19126A121). The EEOB staff has reviewed the licensees responses and has determined that the following additional information is needed to complete the review of the WBN license amendment request.

Regulatory Requirements Title 10 of the Code of Federal Regulations (10 CFR), Section 50.36, Technical Specifications, requires, in part, that the operating license of a nuclear production facility include TSs.

Section 50.36(c)(2) of 10 CFR requires that the TS include limiting conditions for operation (LCOs) which are the lowest functional capability or performance levels of equipment required for safe operation of the facility. When an LCO of a nuclear reactor is not met, the licensee shall shut down the reactor or follow any remedial action permitted by the technical specifications until the condition can be met.

Appendix A, General Design Criteria [GDC] for Nuclear Power Plants, to 10 CFR Part 50.

GDC-17, Electric power systems, states, in part:

An onsite electric power system and an offsite electric power system shall be provided to permit functioning of structures, systems, and components important to safety. [] The 1

onsite electric power supplies, including the batteries, and the onsite electric distribution system, shall have sufficient independence, redundancy, and testability to perform their safety functions assuming a single failure.

Regulatory Guidance TSTF-500, Revision 2.

EEOB RAI-7.b.01 In its June 7, 2019, letter, in response to EEOB RAI-7, the licensee proposed to revise the TS LCO 3.8.4 statement for the diesel generator (DG) DC electrical power subsystems from four DG DC electrical power subsystems to Train A and Train B DG DC electrical power subsystems; and to revise the TS 3.8.4 and TS 3.8.6 conditions related to the DG electrical power subsystems. The licensee stated that the proposed change to the LCO 3.8.4 with respect to the DG DC electrical power subsystem supports the redundancy of the standby electrical power subsystem. The licensee provided the following explanation (emphasis added):

Each DG DC electrical power system is independent and dedicated to its respective DG.

The DGs that are supported by the DG DC electrical power systems are arranged in redundant trains (i.e., DG 1A-A and DG 2A-A are in Train A, and DG 1B-B and DG 2B-B are in Train B). When one or two DGs in a train are inoperable, that train of standby electrical power is incapable of performing the safety function and must rely on the redundant DG train to mitigate an event. Likewise, if one or two of the DG DC trains that support the DGs in that train are inoperable, that train of standby electrical power is incapable of performing the safety function and must rely on the redundant train to mitigate an event. Therefore, the LCO requires Train A and Train B DG DC electrical power subsystems to be OPERABLE to support the redundancy of the standby electrical power system.

In its November 29, 2018, letter, Enclosure 1, Section 2.0, Assessment, the licensee states (emphasis added):

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 NRC staff has identified the following apparent discrepancies:

x It appears that the DC power for a DG is provided by a DG DC electrical power system in the June 7, 2019, letter but by a DG battery subsystem in the November 29, 2018, letter.

x It appears that a discussion provided in the June 7, 2019, letter did not describe the relationship between the DG DC trains and the DG DC subsystems.

The NRC staff requests the following information to address these discrepancies:

1- Clarify whether a DG DC subsystem or DG DC system supports each DG.

2- Clarify the relationship between the DG DC trains and the DG DC electrical power subsystems in the above-mentioned paragraph in the June 7, 2019, letter.

2

EEOB RAI-9 In its June 7, 2019, letter, the licensee proposed a revised TS 3.8.4 Condition D and associated Required Actions D.1, D.2, and D.3 to state:

CONDITION REQUIRED ACTION COMPLETION TIME D. One or two DG DC D.1 Restore DG battery 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> battery charger(s) on terminal voltage to one train inoperable greater than or equal to the minimum established float voltage.

AND D.2 Verify battery float Once per 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> cuUUHQWDPS

AND D.3 Restore DG battery 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> charger(s) to OPERABLE status.

In its November 29, 2018, letter, Enclosure 1, Section 2.0, the licensee states:

A DG battery subsystem is provided for each DG. Each subsystem is comprised of a battery, dual battery charger assembly, distribution center, and cabling. [] Each of the chargers (normal and alternate) in the dual charger assembly has a dedicated AC source from two respective 480V AC Diesel Generator Auxiliary Boards. If the normal charger is unavailable, the alternate charger is selected by the 125V DC transfer switch included in the assembly.

The TSTF-500, Revision 2, allows for a 72-hour CT for an inoperable battery charger based on the condition that an alternate means (e.g. spare battery charger) of restoring battery terminal voltage to greater than or equal to the minimum established float voltage has been used.

The NRC staff has identified the following apparent discrepancies:

x If the WBN DG dual battery charger for each DG battery subsystem on one train is designed such that the alternate battery charger is selected automatically when the normal battery charger becomes inoperable, TS 3.8.4 Condition D will be entered only after both the normal and alternate battery chargers become inoperable. In this case, it appears that there would be no alternate charger that would be used to restore the DG battery terminal voltage to greater than or equal to the minimum established float voltage within 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> (Required Action D.1); and thus, the proposed 72-hour CT for restoring the inoperable DG battery charger to operable status (Required Action D.3) could not be used.

3

The NRC staff requests the following information

1. Discuss the TS requirements for an operable DG battery subsystem and an operable DG DC train. Include in the discussion the number of operable battery charger in the dual assembly that is required for an operable DG battery subsystem and for an operable DG DC train.

2. Discuss the case(s) when Condition D will be entered and provide the alternate means that will be used to restore DG battery terminal voltage to greater than or equal to the minimum established float voltage within 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> to allow the 72-hour CT for the inoperable DG battery charger in each case.

4