Text

Issuance of Amendment Regarding Alternating Current Sources
	ML15225A094
Person / Time
Site:	Watts Bar
Issue date:	09/29/2015
From:	Dion J; Watts Bar Special Projects Branch
To:	James Shea; Tennessee Valley Authority
	Dion J, NRR/DORL/LPWB, 415-1349
References
	TAC MF2549
	Download: ML15225A094 (25)
	v • d • e

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 September 29, 2015 Mr. Joseph W. Shea Vice President, Nuclear Licensing Tennessee Valley Authority 1101 Market Street, LP 3R-C Chattanooga, TN 37 402-2801

SUBJECT:

WATTS BAR NUCLEAR PLANT, UNIT 1 - ISSUANCE OF AMENDMENT REGARDING ALTERNATING CURRENT SOURCES (TAC NO. MF2549)

Dear Mr. Shea:

The U.S. Nuclear Regulatory Commission has issued the enclosed Amendment No. 103 to Facility Operating License No. NPF-90 for the Watts Bar Nuclear Plant, Unit 1. This amendment consists of a change to Technical Specification (TS) 3.8.1, "AC [Alternating Current]

Sources - Operating," Surveillance Requirements 3.8.1.1, 3.8.1.8, 3.8.1.22 and the current licensing basis, as described in the Updated Final Safety Analysis Report, in response to your application dated August 1, 2013, as supplemented by letters dated April 21, 2014, January 29, 2015, and June 12, 2015.

A copy of the related Safety Evaluation is also enclosed. The Notice of Issuance will be included in the Commission's biweekly Federal Register notice. If you have any questions regarding this letter, please contact me at (301) 415-1349.

Jeanne A. Dion, Project Manager Watts Bar Special Projects Branch Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-390

Enclosures:

1. Amendment No. 103 to NPF-90

2. Safety Evaluation cc w/encls: Distribution via Listserv

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 TENNESSEE VALLEY AUTHORITY DOCKET NO. 50-390 WATTS BAR NUCLEAR PLANT, UNIT 1 AMENDMENT TO FACILITY OPERATING LICENSE Amendment No. 103 License No. NPF-90

1. The Nuclear Regulatory Commission (the Commission) has found that:

A. The application for amendment by the Tennessee Valley Authority (TVA or the licensee) dated August 1, 2013, as supplemented by letters dated April 21, 2014, January 29, 2015, and June 12, 2015, complies with the standards and requirements of the Atomic Energy Act of 1954, as amended (the Act), and the Commission's rules and regulations set forth in Title 10 of the Code of Federal Regulations (10 CFR) Chapter I; B. The facility will operate in conformity with the application, the provisions of the Act, and the rules and regulations of the Commission; C. There is reasonable assurance (i) that the activities authorized by this amendment can be conducted without endangering the health and safety of the public, and (ii) that such activities will be conducted in compliance with the Commission's regulations; D. The issuance of this amendment will not be inimical to the common defense and security or to the health and safety of the public; and E. The issuance of this amendment is in accordance with 10 CFR Part 51 of the Commission's regulations and all applicable requirements have been satisfied.

Enclosure 1

2. Accordingly, the license is amended as indicated in the attachment to this license amendment.

Paragraph 2.C.(2) of Facility Operating License No. NPF-90 is hereby amended to read as follows:

(2) Technical Specifications and Environmental Protection Plan The Technical Specifications contained in Appendix A as revised through Amendment No. 103 and the Environmental Protection Plan contained in Appendix B, both of which are attached hereto, are hereby incorporated into this license. TVA shall operate the facility in accordance with the Technical Specifications and the Environmental Protection Plan.

3. This license amendment is effective as of the date of its issuance, and shall be implemented after the issuance of the facility operating license for Watts Bar Nuclear Plant (WBN) Unit 2, and prior to WBN Unit 2 entry into Mode 4, "Hot Shutdown."

FOR THE NUCLEAR REGULATORY COMMISSION sie F. Qu1chocho, Chief atts Bar Special Projects Branch Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation

Attachment:

Changes to the Operating License Date of Issuance: September 29, 2015

ATTACHMENT TO LICENSE AMENDMENT NO. 103 FACILITY OPERATING LICENSE NO. NPF-90 DOCKET NO. 50-390 Replace Page 3 of Operating License NPF-90 with the attached Page 3.

Replace the following pages of the Appendix A Technical Specifications with the attached pages. The revised pages are identified by amendment number and contain vertical lines indicating the area of change.

Remove Pages Insert Pages 3.8-1 3.8-1 3.8-2 3.8-2 3.8-2a 3.8-2a 3.8-3 3.8-3 3.8-4 3.8-4 3.8-5 3.8-5 3.8-6 3.8-6 3.8-8 3.8-8 3.8-16 3.8-16

3 (4) TVA, pursuant to the Act and 10 CFR Parts 30, 40 and 70, to receive, possess, and use in amounts as required, any byproduct, source or special nuclear material without restriction to chemical or physical form, for sample analysis, instrument calibration, or other activity associated with radioactive apparatus or components; and (5) TVA, pursuant to the Act and 10 CFR Parts 30, 40 and 70, to possess, but not separate, such byproduct and special nuclear materials as may be produced by the operation of the facility.

C. This license shall be deemed to contain and is subject to the conditions specified in the Commission's regulations set forth in 10 CFR Chapter I and is subject to all applicable provisions of the Act and to the rules, regulations, and orders of the Commission now or hereafter in effect, and is subject to the additional conditions specified or incorporated below.

(1) Maximum Power Level TVA is authorized to operate the facility at reactor core power levels not in excess of 3459 megawatts thermal.

(2) Technical Specifications and Environmental Protection Plan The Technical Specifications contained in Appendix A as revised through Amendment No. and the Environmental Protection Plan contained in Appendix B, both of which are attached hereto, are hereby incorporated into this license. TVA shall operate the facility in accordance with the Technical Specifications and the Environmental Protection Plan.

(3) Safety Parameter Display System (SPDS) (Section 18.2 of SER Supplements 5 and 15)

Prior to startup following the first refueling outage, TVA shall accomplish the necessary activities, provide acceptable responses, and implement all proposed corrective actions related to having the Watts Bar Unit 1 SPDS operational.

(4) Vehicle Bomb Control Program (Section 13.6.9 of SSER 20)

During the period of the exemption granted in paragraph 2.D.(3) of this license, in implementing the power ascension phase of the approved initial test program, TVA shall not exceed 50% power until the requirements of 10 CFR 73.55(c)(7) and (8) are fully implemented. TVA shall submit a letter under oath or affirmation when the requirements of 73.55(c)(7) and (8) have been fully implemented.

Facility License No. NPF-90 Amendment No.103

AC Sources - Operating 3.8.1 3.8 ELECTRICAL POWER SYSTEMS 3.8.1 AC Sources - Operating LCO 3.8.1 The following AC electrical sources shall be OPERABLE:

a. Two qualified circuits between the offsite transmission network and the onsite Class 1E AC Electrical Power Distribution System; and

b. Four diesel generators (DGs) capable of supplying the onsite Class 1E AC Electrical Power Distribution System.

NOTE----------------------------------------------------

The C-S DG may be substituted for any of the required DGs.

APPLICABILITY: MODES 1, 2, 3, and 4.

ACTIONS

NOTE------------------------------------------------------------------

LCO 3.0.4.b is not applicable to DGs.

CONDITION REQUIRED ACTION COMPLETION TIME A. One required offsite circuit A.1 Perform SR 3.8.1.1 for required 1 hour1.157407e-5 days 2.777778e-4 hours 1.653439e-6 weeks 3.805e-7 months inoperable. OPERABLE offsite circuit.

Once per 8 hours9.259259e-5 days 0.00222 hours 1.322751e-5 weeks 3.044e-6 months thereafter A.2 Declare required feature(s) 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months from with no offsite power available discovery of no inoperable when its redundant offsite power to one required feature(s) is train concurrent with inoperable. inoperability of redundant required feature(s)

(continued)

Watts Bar-Unit 1 3.8-1 Amendment 39, 1 03

AC Sources - Operating 3.8.1 ACTIONS CONDITION REQUIRED ACTION COMPLETION TIME A. (continued) A.3 Restore required offsite circuit 72 hours8.333333e-4 days 0.02 hours 1.190476e-4 weeks 2.7396e-5 months to OPERABLE status.

AND 6 days from discovery of failure to meet LCO B. One required DG B.1 Perform SR 3.8.1.1 for the 1 hour1.157407e-5 days 2.777778e-4 hours 1.653439e-6 weeks 3.805e-7 months inoperable. required offsite circuits.

AND Once per 8 hours9.259259e-5 days 0.00222 hours 1.322751e-5 weeks 3.044e-6 months thereafter AND B.2 Declare required feature(s) 4 hours4.62963e-5 days 0.00111 hours 6.613757e-6 weeks 1.522e-6 months from supported by the inoperable discovery of DG inoperable when its Condition B required redundant feature(s) concurrent with is inoperable. inoperability of redundant required feature(s)

AND B.3.1 Determine OPERABLE DGs 12 hours1.388889e-4 days 0.00333 hours 1.984127e-5 weeks 4.566e-6 months are not inoperable due to common cause failure.

OR B.3.2 Perform SR 3.8.1.2 for 12 hours1.388889e-4 days 0.00333 hours 1.984127e-5 weeks 4.566e-6 months OPERABLE DGs.

AND (continued)

Watts Bar-Unit 1 3.8-2 Amendment 39, 103

AC Sources - Operating 3.8.1 ACTIONS CONDITION REQUIRED ACTION COMPLETION TIME B. (continued) B.4 Restore required DG to 14 days OPERABLE status.

AND 17 days from discovery of failure to meet LCO C. Two required DGs in Train C.1 Perform SR 3.8.1.1 for the 1 hour1.157407e-5 days 2.777778e-4 hours 1.653439e-6 weeks 3.805e-7 months A inoperable. required offsite circuits.

AND OR Once per 8 hours9.259259e-5 days 0.00222 hours 1.322751e-5 weeks 3.044e-6 months Two required DGs in Train thereafter B inoperable. AND C.2 Declare required feature(s) 4 hours4.62963e-5 days 0.00111 hours 6.613757e-6 weeks 1.522e-6 months from supported by the inoperable discovery of DGs inoperable when its Condition C required redundant feature(s) concurrent with is inoperable. inoperability of redundant required feature(s)

AND C.3.1 Determine OPERABLE DGs 12 hours1.388889e-4 days 0.00333 hours 1.984127e-5 weeks 4.566e-6 months are not inoperable due to common cause failure.

OR C.3.2 Perform SR 3.8.1.2 for 12 hours1.388889e-4 days 0.00333 hours 1.984127e-5 weeks 4.566e-6 months OPERABLE DGs.

AND (continued)

Watts Bar-Unit 1 3.8-2a Amendment 39, 1 03

AC Sources-Operating 3.8.1 CONDITION REQUIRED ACTION COMPLETION TIME C. (continued) C.4 Restore at least one required 72 hours8.333333e-4 days 0.02 hours 1.190476e-4 weeks 2.7396e-5 months DG to OPERABLE status.

AND 6 days from discovery of failure to meet LCO D. Two required offsite circuits D.1 Declare required feature(s) 12 hours1.388889e-4 days 0.00333 hours 1.984127e-5 weeks 4.566e-6 months from inoperable. inoperable when its redundant discovery of required feature(s) is Condition D inoperable. concurrent with inoperability of redundant required features AND D.2 Restore one required offsite 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months circuit to OPERABLE status.

(continued)

Watts Bar-Unit 1 3.8-3 Amendment 30, 39, 103

AC Sources-Operating 3.8.1 ACTIONS (continued)

CONDITION REQUIRED ACTION COMPLETION TIME E. One required offsite circuit ---------------------NOTE----------------------

inoperable. Enter applicable Conditions and Required Actions of LCO 3.8.9, AND "Distribution Systems- Operating,"

when Condition Eis entered with no One or more required AC power source to any train.

DG(s) in Train A ----------------------------------------------------

inoperable.

E.1 Restore required offsite circuit 12 hours1.388889e-4 days 0.00333 hours 1.984127e-5 weeks 4.566e-6 months OR to OPERABLE status.

One or more required OR DG(s) in Train B inoperable. E.2 Restore required DG(s) to 12 hours1.388889e-4 days 0.00333 hours 1.984127e-5 weeks 4.566e-6 months OPERABLE status.

F. One or more required F.1 Restore required DGs in Train 2 hours2.314815e-5 days 5.555556e-4 hours 3.306878e-6 weeks 7.61e-7 months DG(s) in Train A A to OPERABLE status.

inoperable.

OR AND F.2 Restore required DGs in Train 2 hours2.314815e-5 days 5.555556e-4 hours 3.306878e-6 weeks 7.61e-7 months One or more required B to OPERABLE status DG(s) in Train B inoperable.

G. Required Action and G.1 Be in MODE 3. 6 hours6.944444e-5 days 0.00167 hours 9.920635e-6 weeks 2.283e-6 months Associated Completion Time of Condition A, B, C, AND D, E, or F not met.

G.2 Be in MODE 5. 36 hours4.166667e-4 days 0.01 hours 5.952381e-5 weeks 1.3698e-5 months (continued)

Watts Bar-Unit 1 3.8-4 Amendment 39 1 03

AC Sources-Operating 3.8.1 ACTIONS (continued)

CONDITION REQUIRED ACTION COMPLETION TIME H. Two required offsite circuits H.1 Enter LCO 3.0.3. Immediately inoperable.

AND One or more required DG(s) in Train A inoperable.

OR One or more required DG(s) in Train B inoperable.

I. One required offsite circuit 1.1 Enter LCO 3.0.3. Immediately inoperable.

AND One or more required DG(s) in Train A inoperable.

AND One or more required DG(s) in Train B inoperable.

Watts Bar-Unit 1 3.8-5 ,

Amendment 39 1 03

AC Sources-Operating 3.8.1 SURVEILLANCE REQUIREMENTS SURVEILLANCE FREQUENCY SR 3.8.1.1 Verify correct breaker alignment and indicated power 7 days availability for each required offsite circuit.

SR 3.8.1.2 -------------------------------N 0 TES----------------------------

1. Performance of SR 3.8.1.7 satisfies this SR.

2. A modified DG start involving idling and gradual acceleration to synchronous speed may be used for this SR as recommended by the manufacturer. When modified start procedures are not used, the time, voltage, and frequency tolerances of SR 3.8.1. 7 must be met.

Verify each DG starts from standby conditions and As specified in achieves steady state voltage ;::: 6800 V and ::; 7260 Table 3.8.1-1 V, and frequency;::: 58.8 Hz and ::; 61.2 Hz.

(continued)

Watts Bar-Unit 1 3.8-6 Amendment No. 103

AC Sources-Operating 3.8.1 SURVEILLANCE REQUIREMENTS (continued)

SURVEILLANCE FREQUENCY SR 3.8.1.7 Verify each DG starts from standby condition and 184 days achieves in s 10 seconds, voltage 2 6800 V, and frequency 2 58.8 Hz. Verify after DG fast start from standby conditions that the DG achieves steady state voltage 2 6800 V and s 7260 V, and frequency 2 58.8 Hz and s 61.2 Hz.

SR 3.8.1.8 ------------------------------NOTE§-------------------------------

.1. For the 1A-A and 1B-B Shutdown Boards, this Surveillance shall not normally be performed in MODE 1 or 2. However, this Surveillance may be performed to reestablish OPERABILITY provided an assessment determines the safety of the plant is maintained or enhanced. GQredit may be taken for unplanned events that satisfy this SR.

£. Transfer capability is only required to be met for 6.9 kV shutdown boards that require normal and alternate power supplies.

Verify automatic and manual transfer of each 6.9 kV 18 months shutdown board power supply from the normal offsite circuit to theeaffi alternate offsite circuit.

(continued)

Watts Bar-Unit 1 3.8-8 Amendment 89, 1 03

AC Sources-Operating 3.8.1 SURVEILLANCE REQUIREMENTS (continued)

SURVEILLANCE FREQUENCY SR 3.8.1.21 Verify when started simultaneously from standby 10 years condition, each DG achieves, in::; 10 seconds, voltage 2 6800 V and frequency 2 58.8 Hz. Verify after DG fast start from standby conditions that the DG achieves steady state voltage 2 6800 V and ::;

7260 V, and frequency 2 58.8 Hz and ::; 61.2 Hz.

SR 3.8.1.22 ------------------------------N 0 TES-------------------------------

.1_ For the 1B and 1C Unit Boards. this Surveillance shall not normally be performed in MODE 1 or 2.

However, this surveillance may be performed to reestablish OPERABILITY provided an assessment determines the safety of the plant is maintained or enhanced. Credit may be taken for unplanned events that satisfy this SR.

2. Transfer capability is only required to be met for 6.9 kV unit boards that require normal and alternate power supplies.

Verify automatic transfer of each 6.9 kV Unit Board 18 months 1B, 1C, 2B. and 2C power supply from the normal power supply to the alternate power supply.

Watts Bar-Unit 1 3.8-16 Amendment No.103

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO. 103 TO FACILITY OPERATING LICENSE NO. NPF-90 TENNESSEE VALLEY AUTHORITY WATTS BAR NUCLEAR PLANT. UNIT 1 DOCKET NO. 50-390

1.0 INTRODUCTION

By letter dated August 1, 2013 (Reference 1) and supplemented by letters dated April 21, 2014 (Reference 3), January 29, 2015 (Reference 5), and June 12, 2015 (Reference 7), the Tennessee Valley Authority (TVA, or the licensee), submitted a license amendment request (LAR) for Watts Bar Nuclear Plant (WBN) Unit 1. The purpose of the LAR was to modify the limiting condition for operation (LCO) for the offsite alternating current (AC) power source in Technical Specification (TS) 3.8.1, "AC Sources - Operating," Surveillance Requirements (SRs) and the current licensing basis, as described in the Updated Final Safety Analysis Report (UFSAR), for the available maintenance feeder for Common Station Service Transformers (CSSTs) A and B.

Specifically, the LAR requested a revision to the WBN Unit 1 UFSAR for use of CSSTs A and B as qualified offsite power sources. In addition, the licensee proposed a modification to TS LCO 3.8.1 for the AC Sources - Operating, to provide additional time to restore an inoperable offsite circuit, proposed modifications to SR 3.8.1.1 and SR 3.8.1.8 and proposed a new SR 3.8.1.22. The licensee provided supplemental information in response to several requests for additional information (RAls). The supplemental letters dated April 21, 2014, January 29, and June 12, 2015, provided additional information that clarified the application, and expanded the scope of the application as originally noticed in the Federal Register (FR), 78 FR 64547 on October 29, 2013. The supplements did not change the staffs original proposed no significant hazards consideration determination. A subsequent notice was published in the FR on August 28, 2015 along with the NRC's staff proposed no significant hazards consideration determination (80 FR 52348).

Background

The WBN electrical power system is currently configured for single-unit operation with four CSSTs that provide power from the transmission system to the plant auxiliaries. The safety related Class 1E power system is supplied from CSSTs C and D. CSSTs A and B are used for non-safety-related loads. During operation in Mode 1, 2, 3, or 4 with either CSST C or D out of service, the plant is required to enter LCO 3.8.1 Condition A for not having two qualified offsite Enclosure 2

power sources available for the safety buses. TVA is now preparing to place WBN Unit 2 into commercial operation and the electrical systems are being configured to support dual-unit operation. CSST C and D will also be used to provide offsite power to WBN Unit 2 safety related boards and will be subjected to LCO 3.8.1 when either transformer is not available.

Therefore, when CSST C or D is out of service, both units enter LCO 3.8.1.

By letter dated July 12, 2010 (Reference 10), the U.S. Nuclear Regulatory Commission (NRC) staff requested additional information regarding electrical systems for WBN Unit 2 UFSAR amendments Nos. 95 and 97. The 2010 letter requested TVA to provide a summary of the analyses performed to support dual-unit operation in accordance with the existing and proposed licensing basis constraints and requirements. In response, by letter dated July 31, 2010 (Reference 11 ), TVA provided a summary of a study performed to evaluate the WBN electrical distribution system to determine its adequacy for dual-unit operation. The licensee evaluated the plant for following design requirements:

Dual-unit trip as a result of an abnormal operational occurrence;

Accident in one unit and concurrent shutdown of the second unit (with and without offsite power); and

Accident in one unit and spurious Engineered Safety Feature Actuation in the other unit (with and without offsite power).

The study evaluated existing CSSTs A, B, C, and D used for supplying the plant auxiliary system from offsite power sources. According to the current design basis requirements, CSSTs C and D are dedicated qualified offsite power sources for supplying power to the safe shutdown boards and CSSTs A and Bare used for supporting plant auxiliaries required for normal plant operation.

In the 2010 study, the licensee considered the adequacy of existing CSSTs A and B to determine their acceptability as qualified offsite power sources for the safety related boards when used for safe shutdown of the units under a design-basis loss-of-coolant accident. Based on the results of the study, the licensee upgraded the two transformers and added automatic on load tap changers on the primary side of CSSTs A and B. As a defense-in-depth measure, the upgraded CSSTs A and Bare considered to have adequate capacity to provide an additional source of power to the safety related system. The intent of the upgrade was to allow either CSST A or B to power the shutdown boards while either CSST C or D is out of service for maintenance. CSSTs A and B (only one at a time) can be aligned to safe shutdown boards during short maintenance periods but the plant is currently not licensed to operate in this configuration for an extended duration and, also, is not consistent with offsite power system design basis.

2.0 REGULATORY EVALUATION

2.1 System Description The preferred offsite power for WBN, as described in UFSAR Section 8.2, is supplied from TVA's 161 kiloVolt (kV) transmission grid at Watts Bar Hydro Plant switchyard over two separate transmission lines, each connecting to 161/6.9 kV CSSTs A, B, C, and D.

The low voltage side of CSSTs A and B power non-safety-related 6.9 kV station service buses which include the 6.9 kV common, unit and RCP boards. CSST A is normally aligned to provide offsite power to 6.9 kV common board A and alternate power to 6.9 kV unit boards 1A, 1C, 2A and 2C. When CSST D is not available, CSST A can be aligned manually to provide power to train B, 6.9 kV shutdown boards 1B-B (Unit 1) and 28-B (Unit 2). CSST B provides offsite power, from the secondary Y winding to 6.9 kV common board Band alternate power to 6.9 kV unit boards 1B, 1D, 28 and 2D. When CSST C is not available, CSST B can be aligned manually to provide power to the train A 6.9 kV shutdown boards 1A-A (Unit 1) and 2A-A (Unit 2).

CSST C provides offsite power from the secondary Y winding to 6.9 kV shutdown board 1A-A and from the secondary X winding to 6.9 kV shutdown board 2A-A. In addition, this transformer provides alternate (offsite) power from the secondary X winding to 6.9 kV shutdown board 1B-B and from the secondary Y winding to 6.9 kV shutdown board 28-B. CSST C is normally aligned to power 6.9 kV shutdown boards 1A-A (Unit 1) and 2A-A (Unit 2). CSST D provides offsite power from the secondary X winding to 6.9 kV shutdown board 1B-B and from the secondary Y winding to 6.9 kV shutdown board 28-B. In addition, this transformer provides alternate (offsite) power from the secondary Y winding to 6.9 kV shutdown board 1A-A from the secondary X winding to 6.9 kV shutdown board 2A-A. CSST Dis normally aligned to power 6.9 kV shutdown boards 1B-B (Unit 1) and 28-B (Unit 2). The four 6.9 kV shutdown boards that are arranged electrically into four power trains (two per unit) with two boards associated with each load group in each unit. The balance of Class 1E auxiliary power system is normally aligned to the respective 6.9 kV shutdown board load group.

Hence, each 161 kV line associated with CSST C and D is the normal feed for one train of shutdown boards and the alternate feed for the other train of shutdown boards. The other transformers (CSST A and B) on each line supply power to the 6.9 kV non-safety-related unit boards and can indirectly power the shutdown boards if they are tied to the unit boards through the maintenance feeder. This maintenance feeder path is not currently a qualified General Design Criterion (GDC) 17 source for the shutdown boards and can only be used when the plant is shutdown.

2.2 Description of Proposed Changes 2.2.1 Technical Specifications In the LAR, the licensee has stated that the TS change is needed to support dual-unit operations without requiring a dual-unit shutdown during maintenance on either preferred power CSST C or D. By letter dated January 29, 2015 (Reference 5, Enclosure 2), the licensee provided revised changes to TS 3.8.1 that superseded all the changes previously proposed in the LAR. Specifically, TS 3.8.1 'AC Sources - Operating,' changes include adding the term "required" to applicable references to offsite power in Action statements (as summarized in the table below), revising SRs 3.8.1.1 and 3.8.1.8, and adding a new requirement, SR 3.8.1.22.

CONDITION REQUIRED ACTION A One required offsite circuit inoperable. A.1 Perform SR 3.8.1 .1 for required OPERABLE offsite circuit.

A.3 Restore required offsite circuit to OPERABLE status.

B. One required DG [diesel generator] B.1 Perform SR 3.8.1.1 for the required inoperable. offsite circuits C. Two required DGs in Train A inoperable. C.1 Perform SR 3.8.1.1 for the required offsite circuits.

D. Two required offsite circuits inoperable. D.2 Restore one required offsite circuit to OPERABLE status E. One required offsite circuit inoperable E.1 Restore required offsite circuit to OPERABLE status.

H. Two required offsite circuits inoperable (No change to Required Action H.1)

I. One required offsite circuit inoperable. (No change to Required Action 1.1)

The LAR proposed a revision to SR 3.8.1.1 to read:

Verify correct breaker alignment and indicated power availability for each required offsite circuit.

The LAR would revise SR 3.8.1.8 to state:

NOTES------------------------------------------------------

1) For the 1A-A and 1B-B Shutdown Boards, this Surveillance shall not normally be performed in MODE 1 or 2. However, this Surveillance may be performed to reestablish OPERABILITY provided an assessment determines the safety of the plant is maintained or enhanced. Credit may be taken for unplanned events that satisfy this SR.

2) Transfer capability is only required to be met for 6.9 kV shutdown boards that require normal and alternate power supplies.

Verify automatic and manual transfer of each 6.9 kV shutdown board power supply from the normal offsite circuit to the alternate offsite circuit.

The licensee proposed a new SR, 3.8.1.22, to state:

NOTES------------------------------------------------------

1) For the 1 B and 1 C Unit Boards, this Surveillance shall not normally be performed in MODE 1 or 2. However, this surveillance may be performed to reestablish OPERABILITY provided an assessment determines the safety of the

plant is maintained or enhanced. Credit may be taken for unplanned events that satisfy this SR

2) Transfer capability is only required to be met for 6.9 kV unit boards that require normal and alternate power supplies.

Verify automatic transfer of each 6.9 kV Unit Board 1B, 1C, 2B, and 2C power supply from the normal power supply to the alternate power supply.

Frequency: 18 months 2.2.2 Changes to Updated Final Safety Analysis Report (UFSAR)

By letter dated January 29, 2015 (Reference 5), the licensee provided revised changes to the UFSAR sections that describe the alternate AC power sources through CSSTs A and B.

Specifically, Enclosure 2, Attachment 5, of Reference 5 provided proposed changes to UFSAR Sections 8.1.2, 8.2.1, 8.2.1.2, 8.2.1.3, 8.2.1.5, 8.2.1.6, 8.2.1.7 and 8.2.2. In the original LAR, the licensee had indicated that UFSAR Figures 8.1-2, 8.1-2B, 8.3-5, 8.3-16, 8.3-17, 8.3-18, and

8. 3-19 are affected by the proposed change and will be updated as part of the amendment implementation phase to be included in the subsequent UFSAR update as required by Title 10 of the Code of Federal Regulations (10 CFR) 50.71 (e), "Maintenance of records, making of reports." The licensee did not submit the changes to the UFSAR Figures delineated in the LAR.

2.3 Applicable Regulatory Requirements The NRC staff determined that the following regulatory requirements are applicable in the safety review of the proposed license amendment.

GDC 17, "Electric power systems," of Appendix A, "General Design Criteria for Nuclear Power Plants," to 10 CFR Part 50, requires, in part, that nuclear power plants have an onsite and an offsite electric power system to permit the functioning of structures, systems, and components that are important to safety. The onsite system is required to have sufficient independence, redundancy, and testability to perform its safety function, assuming a single failure. The offsite power system is required to be supplied by two physically independent circuits that are designed and located so as to minimize, to the extent practical, the likelihood of their simultaneous failure under operating and postulated accident and environmental conditions. In addition, this criterion requires provisions to minimize the probability of losing electric power from the remaining electric power supplies as a result of loss of power from the unit, the offsite transmission network, or the onsite power supplies.

GDC 5, "Sharing of structures, systems, and components" states that structures, systems, and components important to safety shall not be shared among nuclear power units unless it can be shown that such sharing will not significantly impair their ability to perform their safety functions, including, in the event of an accident in one unit, an orderly shutdown and cooldown of the remaining units. At WBN, the two units share offsite power sources.

GDC 18, "Inspection and testing of electric power systems," requires that electric power systems that are important to safety must be designed to permit appropriate periodic inspection and testing of important areas and features. At WBN, the paths for offsite power systems must be routinely tested to validate operability.

It states in 10 CFR 50.63, "Loss of all alternating current power," that each light-water-cooled nuclear power plant licensed to operate under Part 50 must be able to withstand for a specified duration and recover from a station blackout (SBO). After a loss of all AC power resulting in SBO, WBN unit(s) may recover from SBO by restoring onsite power systems. The ability to transfer from onsite to offsite power systems should be maintained.

It states in 10 CFR 50.65, "Requirements for monitoring the effectiveness of maintenance at nuclear power plants," that preventive maintenance activities must not reduce the overall availability of the systems, structures, or components.

The requirements related to the content of the TSs are established in 10 CFR 50.36, "Technical specifications." Pursuant to 10 CFR 50.36(c) TSs will include items in the following categories.

(1) safety limits, limiting safety system settings, and limiting control settings, (2) LCOs, (3) SRs, (4) design features, and (5) administrative controls.

The following documents were also considered for guidance during this review.

Regulatory Guide (RG) 1.32 "Criteria for Power Systems for Nuclear Power Plants" (Revision 0),

describes a method acceptable to the NRC staff for complying with the NRC's regulations for the design, operation, and testing of electric power systems in nuclear power plants.

NU REG 0800, "Standard Review Plan for the Review of Safety Analysis Reports for Nuclear Power Plants" (initially issued as NUREG-75/087), Section 8.2 Offsite Power System, Revision 5, May 2010.

NUREG-0847, Supplement No. 22, "Safety Evaluation Report Related to the Operation of Watts Bar Nuclear Plant, Unit 2," Docket No. 50-391.

NRC Generic Letter (GL) 79-36, "Adequacy of Station Electric Distribution Systems Voltages,"

dated August 8, 1979.

3.0 TECHNICAL EVALUATION

3.1 Evaluation The current licensing basis of WBN Unit 1 includes the capability to power each of the shutdown boards 1A-A and 1B-8 from CSSTs C or D. For compliance with GDC 17, each shutdown board has an immediately available normal source, CSST C for 1A-A and CSST D for 18-8. An additional source for the shutdown boards is available by an automatic transfer to the alternate source CSST D for 1A-A and CSST C for 18-8. lfWBN Unit 2 commences commercial operation, the corresponding Unit 2 shutdown boards 2A-A and 28-8 will have a similar arrangement for normal and alternate power sources from CSSTs C and D.

The current licensing basis allows use of CSST A or B (one at a time) as a temporary power source for safe shutdown boards when the normal source CSST C or D is not available due to maintenance activities. The plant enters LCO 3.8.1 Condition A when CSST C or D is unavailable. Action A allows plant operation for 72 hours8.333333e-4 days 0.02 hours 1.190476e-4 weeks 2.7396e-5 months with one offsite power source unavailable. The LAR proposes use of CSSTs A or B (one at a time) as GDC 17 power sources to provide power to the shutdown boards for an extended duration as a replacement source for one of the two normal power sources through CSST C or D. In addition, the original LAR proposed Action A to be revised to allow one qualified offsite circuit to be inoperable for up to 14 days with CSST A or B available, but not connected to the appropriate safe shutdown board.

The TS change request indicated that 14 days would provide adequate time for maintenance of a CSST and will support dual-unit operation without requiring a dual-unit shutdown during maintenance on either preferred power source CSST C or D.

In RAI dated February 26, 2014 (Reference 2), the NRC staff requested clarification related to the information provided in the LAR.

Items No. 1 and No. 6 of the RAI requested information pertaining to plant response during the extended 14-day completion time (CT) when one offsite source (CSST C or D) is unavailable and CSST A or B is available but not necessarily connected to the corresponding shutdown boards. Specifically, the NRC staff was concerned that the time required to manually close the maintenance path breakers may take longer than the time assumed in the accident analysis. As a consequence, the offsite power source through CSST A or B may not be available in sufficient time following a loss of all onsite AC power supplies and the other offsite electric power circuit, to assure that specified acceptable fuel design limits and design conditions of the reactor coolant pressure boundary are not exceeded as required by GDC 17. The staff requested details on the sequence of events following an accident in one unit necessitating shutdown of both units using available offsite power sources.

By letter dated April 21, 2014 (Reference 3), the licensee provided responses to the RAI items.

The response to item No. 1 provided a summary of the information provided during the licensing review of WBN Unit 2 design basis including staff approval of sizing and capability of CSST A and B. The licensee stated in its response to item No. 1 that:

TVA has concluded that based on the upgrades to CSST A and B supported by the electrical studies and engineering calculations, as discussed above and in the references, there exists reasonable assurance that TVA has demonstrated that the requirements of GDC 17 are satisfied and that CSSTs A or B may be used as proposed in the LAR.

In the response to item No. 6, the licensee stated that:

Either CSST C or CSST D is able to supply power for both units within specified limits to components and systems required to ensure that fuel design limits, reactor coolant pressure boundary design conditions, vital functions are maintained, and the core is cooled during postulated accident conditions.

The response also stated that CSST A or B can support safe shutdown after automatic transfer of plant buses from Unit Station Service Transformers (USSTs). The responses did not address the concern related to the time required to manually connect the safe shutdown boards to CSST A or B.

By letter dated June 2, 2014 (Reference 4), the NRC staff provided clarification to the intent of RAI item numbers 1 and 6. The staff noted that WBN Unit 1 current licensing basis provides two immediate power sources to redundant trains of WBN Units 1 and 2. In addition, each power source provides assurance that specified acceptable fuel design limits and design conditions of the reactor coolant pressure boundary are not exceeded, as required by GDC 17.

The NRC staff also noted that the current plant design basis includes a fast transfer to the alternate power source if normal power is not available or degraded (i.e., CSST D, if CSST C is unavailable and vice versa). This configuration provides a defense-in-depth measure to support safe shutdown by providing an 'immediate' power source to redundant trains of WBN Units 1 and 2.

In comparison, the NRC staff noted that the proposed change to be non-conservative when compared to the current licensing basis as;

1. there is a time delay associated with aligning CSSTs A and B compared to CSSTs C and D,

2. CSSTs A and Bare not automatically aligned to the shutdown boards,

3. CSSTs A and B do not have the capacity to supply loads on both units during limiting design basis events, and

4. CSSTs A and B cannot be aligned to more than one shutdown board for dual-unit shutdown.

By letter dated January 29, 2015 (Reference 5), the licensee provided a response to the RAI dated June 2, 2014. The licensee's response stated the following:

The enclosures to this letter provide the TVA response to the Reference 4 RAI, revising and superseding in its entirety the RAI response submitted in Reference 3. Enclosure 1 provides TVA's response to the June 2, 2014 email.

Enclosure 2 provides TVA's revised response to TVA's April 21, 2014 RAI response. Attached to Enclosure 2 are revised proposed TS pages, TS Bases pages, and UFSAR pages.

Note that Attachment 3, "Clean Typed" TS pages, is labeled "For Information Only." These pages reflect the changes requested in this LAR using the TS pages currently implemented at WBN. In License Amendment (LA) 84 (Reference 5) the NRC approved changes to WBN Unit 1, TS Section 3.8.1, to be implemented after the issuance of the Facility Operating License for WBN Unit 2 and prior to WBN Unit 2 entry into Mode 4, "Hot Shutdown." Because WBN Unit 2 is under construction with the projected approval of the Facility Operating License in the first half of 2015, LA 84 may be implemented before approval of this LAR. Therefore, the "Clean Typed" TS pages may require changes to reflect implementation of WBN Unit 1, LA 84.

In Enclosure 1, of the January 29, 2015, letter, the licensee stated, "The change is to align the shutdown boards of the Common Station Service Transformer (CSST) that is out-of-service to the associated unit board and power the unit board from the Unit Station Service Transformer (USST) with either CSST A or B in standby or power the unit board directly from either CSST A or B through the start bus." The intent of the revised response was to eliminate the proposed request for 14-day CT before manually closing the breakers associated with the maintenance feeder from CSSTs A and B to the associated shutdown boards.

The revised amendment proposed:

1. to add an allowance to use CSST A or B to meet the requirements of LCO 3.8.1, with respect to qualified offsite circuits, and

2. add testing of the automatic transfers of Unit Boards 1B, 1C, 28, and 2C from the USST to the start bus. The start bus would be powered from either CSST A or B.

The licensee's revised response to RAI item No. 1, related to the time required for the proposed CSSTs A and B to available to respond to an accident signal, stated that the CSSTs have been upgraded to have adequate capacity and capability to satisfy GDC 17 requirements. TVA also summarized the information provided during the licensing review of WBN Unit 2 design. The capacity and capability of CSSTs A and B were evaluated with respect to loading and voltage drop requirements when used as an alternate maintenance source for safe shutdown boards.

The staff has previously reviewed the adequacy of CSSTs A and B from capacity and capability perspective. The staff did not review these sources as a qualified power sources to replace CSSTs C or D with respect to GDC 17 requirements or the guidance discussed in RG 1.32.

RAI item No. 2 requested information on breakers that need to be operated and applicable SRs to ensure the operability of paths to and from the normal GDC 17 sources, CSSTs C and D, to the proposed sources CSSTs A and B.

In the revised response to RAI item No. 2, the licensee stated the following:

1) The original LAR has been revised to return to existing requirements for two qualified circuits to be operable for unrestricted operation and allowing for one required offsite circuit to be inoperable for a maximum of 72 hours8.333333e-4 days 0.02 hours 1.190476e-4 weeks 2.7396e-5 months .

2) If CSST C or Dis out-of-service, TVA is proposing to use either CSST B or A, respectively, as a replacement qualified offsite circuit to supply the affected 6.9 kV shutdown boards. The path for the replacement qualified circuit would be from the 161 kV system to CSST A or B via the non-safety-related station boards to the appropriate 6.9 kV shutdown boards. No additional surveillance requirements are proposed since the circuit will not be considered operable until the manual actions have been completed.

3) If the plant is operating with CSST A or B as one of the GDC 17 sources, then the main generator provides the power to the unit auxiliary boards through the USSTs. In the event of unit trip, there is a fast automatic transfer of the unit auxiliary boards from the USSTs to the CSST A and B.

TVA is proposing to provide assurance of an operable offsite circuit using the normal at-power unit board power supply by requiring the unit board power supply automatic fast transfer to the start bus to be operable. With an operable automatic fast transfer available, the USST supplying power to the unit board, the unit board supplying power to the shutdown board, and CSST A or B aligned to the unit board, the CSST would be available to supply power to the 6.9 kV shutdown board(s) within a few seconds pf a loss of the USST. The automatic transfer from USST to CSST will require periodic verification that it will perform its intended function and SR 3.8.1.22 is proposed to be added to reflect this verification.

4) Currently Unit 1 SR 3.8.1.8 requires verification of automatic and manual transfer of each 6.9 kV shutdown board power supply from the normal offsite circuit to each alternate offsite circuit. The current definition of

'alternate' offsite circuit implies transfer of safe shutdown boards between CSSTs C and D only when one of these is not available. TVA is proposing to change SR 3.8.1.8 to encompass the automatic and manual transfer of shutdown boards between CSSTs C and D, automatic transfer from USST to CSSTs A and B and manual transfer from CSSTs C and D to corresponding CSSTs A and B. The verification will be performed under SR 3.8.1.8 and the wording of this SR is being revised as follows:

I. Current SR: Verify automatic and manual transfer of each 6.9 kV shutdown board power supply from the normal offsite circuit to each alternate offsite circuit.

II. Revised SR: Verify automatic and manual transfer of each 6.9 kV shutdown board power supply from the normal

offsite circuit to the alternate offsite circuit.

The NRC staff understands that the new definition of 'alternate' includes the proposed use of CSST A or B (one at a time) as a GDC 17 source during maintenance of CSST C or D. The requirement to test each of the automatic and manual transfer capability between CSST C and D as 'alternate' sources also remains as per existing SRs.

The NOTES associated with the proposed change indicate that for CSST A and B, the SRs will not generally be performed with the unit(s) in Modes 1 and 2 unless it is necessary to establish OPERABILITY of the transfer scheme to ensure restoration of power to the shutdown boards.

The NRC staff reviewed the information on the design of WBN bus transfer scheme, as provided by the licensee and the proposed TS SRs, to verify the operability of the proposed transfer schemes for offsite power sources to the safe shutdown boards for WBN. The NRC staff concluded that the proposed SRs for the transfer schemes will provide reasonable assurance that offsite power can be restored to shutdown boards in time commensurate with the existing licensing basis and maintain compliance with guidance provided in RG 1.32 and GDC 17 requirements.

The defense-in-depth concept whereby CSST C or D each can supply the four 6.9 kV safe shutdown boards, is not available when CSST A or B is used as an offsite power source.

RAI item No. 3 requested information on compensatory actions that were planned to reduce plant risk when CSST A or B was used as an offsite power source.

In its response, the licensee stated that CSST A or B, used one at a time, satisfies the requirements of GDC 17. Precautions will be taken to prevent overloading each of the transformers as other non-safety-related loads may be supplied by the same transformers. Due to lack of independence between power and control circuits for CSST A and B, CSST A and B cannot be credited as offsite power circuits simultaneously. No additional compensatory actions are planned when the CSST A or B is being used as a substitute for CSST C or D. The licensee stated, "As part of managing plant risk for maintenance activities, CSST C or D will be protected equipment when one of these CSSTs is taken out of service." The control of protective equipment action is delineated in plant procedure 1-Pl-OPS-1-PE, "Protected Equipment."

The NRC staff has previously reviewed the capacity and capability of CSSTs A and B and finds the proposed precautionary actions taken to prevent overloading of CSSTs A and B when used as an offsite power source appropriate. The limitations and actions taken to minimize plant risk by taking specific actions to protect CSSTs C and D during the period that CSST A or B is used as an offsite power source provide reasonable assurance that unintended actions will not adversely impact the normal power sources that are used for compliance with GDC 17 requirements. The precautions taken to prevent overloading of each transformer and use of only one CSST A or B at a time to supply shutdown boards will provide reasonable assurance that sharing will not significantly impair the ability of CSSTs to perform their safety functions, including, in the event of an accident in one unit, an orderly shutdown and cool down of the remaining unit, as required by GDC 5 Based on operating experience, in 1979, the NRC staff issued GL 79-36, which required all licensees to review the electric power systems at each of their nuclear power plants to determine analytically if, assuming all onsite sources of AC power are not available, the offsite power system and the onsite distribution system is of sufficient capacity and capability to automatically start as well as operate all required safety loads. The GL also recommended that the protection of safety loads from undervoltage conditions must be designed to provide the required protection without causing voltages in excess of maximum voltage ratings of safety loads and without causing spurious separations of safety buses from offsite power.

NU REG 0800, provides additional guidance on requirements for loss of voltage and degraded voltage relay (DVR) setpoints.

RAI item No. 4 requested information on the adequacy of DVR setpoint when CSST A or B is used as an offsite power source. The licensee stated that the methodology for validating the DVR setpoints when CSSTs A and Bare used for providing offsite power to the shutdown boards is similar to the methodology used for evaluating the adequacy of the DVR setpoint when CSSTs C and D are used to supply the shutdown boards. The NRC staff has previously documented its review of the methodology used for DVR setpoint when CSST C and D are used as offsite power sources (Reference 9). The NRC staff finds this approach to be acceptable for meeting the intent of guidance provided in NU REG 0800 for DVR setpoint and GL 79-36 requirements for adequacy of onsite distribution system.

The revised LAR deleted the proposed 14-day CT for restoring power to the shutdown boards using CSST A or B when CSST C or D was being maintained. In response to RAI item No. 5, the licensee stated that the maintenance path through CSST A or B will be aligned within TS provided guideline in LCO 3.8.1, Required Action A.3, "Restore required offsite circuit to OPERABLE status," CT of 72 hours8.333333e-4 days 0.02 hours 1.190476e-4 weeks 2.7396e-5 months or Condition G is entered and a unit shutdown is required.

Plant operators have procedural guidance to transfer the 6.9 kV shutdown board power source from either CSST C or D to the associated unit board via the maintenance feed. In addition, the operability of the automatic transfer required by SR 3.8.1.22, between the unit board's normal power supply (USST) and its alternate power supply (CSST) must be validated. All the actions have to be performed within the 72-hour CT of Required Action A.3. The licensee also stated that in the event of a generator trip due to a protective function, the transfer of power source for the plant auxiliary boards from the USST to CSST occurs immediately. A unit trip will result in a 30-second delay before the generator reverse power relay initiates a generator trip and a fast transfer from USST to CSST. During the 30-second delay, the USST remains energized via the main generator and main transformer.

The proposed methodology to manage the restoration of offsite power to shutdown boards via CSST A or B within the existing allowable CT is acceptable. The NRC staff has concluded that procedural guidance and TS 3.8.1.22 requirement for verification of automatic transfer capability provide reasonable assurance that power to the safe shutdown boards will be restored in a timely manner commensurate with existing licensing basis and, hence, maintain compliance with GDC 17 requirements.

RAI item No. 6 was related to consequences of events during the proposed 14-day CT requested in the original LAR. The licensee has revised the LAR to delete the proposed 14-day CT and provided information on plant configuration and consequences including bus transfers with alignment of shutdown boards to CSST A and B. The staff has concluded that the proposed revision to delete the 14-day CT and retain the existing 3-day CT as reasonable and, therefore, acceptable.

RAI item No. 7 requested information about impact on automatic actions associated with supplying power from onsite DGs during an emergency start with temporary configuration of securing breakers for CSST C or D and manually aligning breakers for CSST A or B. The licensee confirmed that the breaker logic is similar for CSSTs A, B, C, and D and the transfer to the maintenance supply through CSST A or B will not preclude automatic actions of the onsite power sources. The staff has previously reviewed the design of onsite DG operation when the shutdown boards are supplied through CSSTs C and D and, therefore, concluded that the automatic actions required when CSST A or CSST B is aligned to the shutdown boards will not be adversely impacted.

Based on the information and responses provided by the licensee in its letter dated January 29, 2015 (Reference 5) that revised the scope of the manual actions proposed in the original LAR, the staff requested further clarification by RAI dated April 15, 2015 (Reference 6). By letter dated June 12, 2015 (Reference 7), the licensee provided responses to five RAI items (A 1 to A5) as discussed below:

RAI item No. A 1 was related to the limitations of CSSTs A and B. In the January 29, 2015, letter, the licensee confirmed that there are limitations when CSST A or B used as offsite power sources. Specifically, per the current licensing basis, CSST C and D each can support safe shutdown of both units using redundant trains. Thus, in the event of failure of one CSST C or D, four shutdown trains are still available by automatic transfer to the alternate source for a dual-unit shutdown with accident postulated in one unit. CSSTs A and B have non-safety-related loads limiting the total loading capability and there is a lack of separation between the circuits associated with the two transformers. Hence, CSSTs A and B each can support only one train of safe shutdown equipment on each unit. In view of the reduction in defense-in-depth when CSST A or B is used as a GDC 17 source, RAI item No. A 1 requested information on any operational limits that the licensee had considered when CSST A or B is used as a GDC 17 source on extended basis.

In response to RAI item No. A 1, the licensee provided an explanation of the flexibility afforded by the automatic transfer feature available in the design of CSSTs C and D during normal plant operation. The licensee stated that in normal configuration, CSST C and Dare each aligned to provide one train of shutdown equipment for each unit and no automatic transfer is required.

Similarly, if all the boards are aligned to the alternate power source, CSST C and D are capable of supporting one train of safe shutdown boards for each unit and no automatic transfer capability is required. For these cases, two GDC 17 sources are available immediately for each train on both units and the automatic transfer is not required. When one, two, or three 6.9 kV shutdown boards are aligned to their alternate sources, the automatic normal-to-alternate fast transfer is required to comply with GDC 17. TVA provided examples of bus configurations, combined with automatic transfer feature that provide assurance for maintaining compliance with GDC 17 requirements. When CSST A or B is used for compliance with GDC 17 requirements, the automatic transfer capabilities from USST provide offsite power to the shutdown boards after a fast transfer. In this configuration, the flexibility to have more than one shutdown train for each unit is not available for CSST A or B. In summary, the licensee stated, "Under all alignments, WBN maintains compliance with GDC 17 by having two immediate access circuits either aligned directly to their credited offsite circuit or by utilizing a normal to alternate fast transfer. As a result, no additional TS required action limiting the duration when using the maintenance feeds through CSST A or Bis needed."

The NRC staff reviewed the examples of bus configurations provided by the licensee and the required automatic transfer features. The NRC staff agrees that the automatic transfer feature in the design of CSST C and D provides operational flexibility and assurance that two GDC 17 sources are available immediately or after a fast transfer. The staff also reviewed the examples of bus configurations when CSST A or B is substituted as a GDC 17 source and concluded that the automatic transfer feature from USST to CSST A or B coupled with load management provide assurance that two offsite power sources, one for each train of each unit, are available for compliance with GDC 17 requirements and are consistent with guidance provided in RG 1.32 as related to offsite power sources.

RAI item A2 requested information on applicable TS SRs that demonstrate the operability of paths used to restore offsite power to the shutdown boards when recovering from a loss of offsite power or SBO with shutdown boards aligned to CSST A or B. In response, the licensee

stated that WBN Unit 1 TS 3.8.1, contains SRs associated with qualified offsite circuits and on site DGs. Specifically, the licensee stated that:

SR 3.8.1.1, SR 3.8.1.8 (as revised by this LAR) and the new SR 3.8.1.22 will be performed to verify the operability of the proposed paths through CSSTs A and B. For either maintenance preferred offsite power source to be operable, it must be in one of two alignments. One alignment has the associated CSST (A or B) directly connected to the 6.9 kV shutdown board through the 6.9 kV unit board and the maintenance feeder. The other acceptable alignment is for the maintenance preferred offsite power source to be connected to the USST through the 6.9 kV unit board with the automatic 6.9 kV unit board transfer operable from normal (USST) to alternate (CSST) and with the CSST in standby. In either alignment, the circuit from the CSST to the 6.9 kV shutdown board is confirmed (SR 3.8.1.1 and SR 3.8.1.22) before it is considered operable.

SR 3.8.1.16 is performed every 18 months and verifies that each DG :

a) Synchronizes with offsite power source while loaded with emergency loads upon a simulated restoration of offsite power; b) Transfers loads to offsite power source; and c) Returns to ready-to-load operation.

The NRC staff reviewed the proposed plant configurations and associated SRs to demonstrate the operability of the paths between the DGs and offsite power systems. The NRC staff noted that the DG control circuits required to connect the DG to the shutdown board are the same, irrespective of the offsite power supply alignment. The NRC staff concluded that performance of SR 3.8.1.16 coupled with SRs 3.8.1.1, 3.8.1.8 and new SR 3.8.1.22 will validate the path for restoration of offsite power to the shutdown boards when recovering from a loss of offsite power or SBO and maintain compliance with this specific element of 10 CFR 50.63, "Loss of all alternating current power."

The licensee has also stated that the shutdown board normal, alternate supply and maintenance supply breakers have similar maintenance programs. The protective relay calibration testing programs are also similar. In addition, logic circuits and breaker cubicles have a periodic testing program. The licensee has concluded that the existing SRs, including those revised by this LAR, confirm the ability to transfer the 6.9 kV shutdown board and associated loads from the DG to the preferred power source and new SRs are not needed.

The NRC staff reviewed the existing SRs identified in this RAI response, and concluded that when the surveillances are performed within the specified period and conducted with the alignment required for safe shutdown of the unit, provide assurance that the DGs can be tested successfully and provide power for the shutdown boards. There will not be an interruption of power for the shutdown boards when they transfer from the onsite source to the offsite source with CSST A or B as an alternate GDC 17 source. The NRC staff notes that SR 3.8.1.16, referenced by the licensee for DG surveillance, is performed every 18 months. In the event that GDC 17 source is changed after SR 3.8.1.16 has been performed, the licensee must confirm

operability in accordance with 10 CFR 50.65 as well as the TS requirements. Based on the adequacy of existing maintenance program for offsite power system components coupled with the proposed surveillances, the NRC staff concluded that the requirements of GDC 18, as related to testing of plant equipment and 10 CFR 50.65, as related to preventive maintenance for GDC 17 sources, will be maintained.

The NRC published 10 CFR 50.65 (commonly referred to as the "Maintenance Rule") based on the determination that proper maintenance is essential to plant safety. The Maintenance Rule provides guidelines for effective maintenance practices to reduce the number of transients and challenges to safety systems and the associated need for operability, availability, and reliability of safety equipment. The licensee has stated that the components in the offsite power sources from the shutdown boards through CSSTs A, B, C, and D will be subjected to the requirements of the Maintenance Rule. The staff has concluded that inclusion of components in the offsite power system through CSSTs A and B provides assurance that failure of components, that could initiate or adversely affect a transient or accident, is minimized. The monitoring of the performance or condition of offsite power system components against licensee-established goals in a manner sufficient to provide reasonable assurance that such components are capable of fulfilling their intended functions meets the requirements of 10 CFR 50.65 as applicable to CSST A, B, C, and D.

RAI item No. A3 requested confirmation that the components in the circuits associated with CSSTs A and B, 161 kV switchyard and the safety related boards will be subjected to the requirements of the Maintenance Rule as applicable under 10 CFR 50.65. The licensee stated that WBN has monitoring criterion at plant level and specific level. CSSTs A and B are within the scope of the Maintenance Rule system, considered risk significant, and monitored at plant level. After approval of this LAR, CSSTs A and B will be monitored similar to CSSTs C and D at the specific level with criteria established for monitoring unavailability and unreliability. The 161 kV switchyard is not in the scope of 10 CFR 50.65.

RAI item No. A4 requested information on the sequence of events related to accident mitigation when the alternate GDC 17 source through CSST A or B is used and there is a delay in transferring shutdown boards from USST to CSST due to generator coast down. In response, TVA has confirmed that after a reactor trip and subsequent turbine trip, there is a fixed 30-second delay before the main generator is tripped by the reverse power relay. The accident loads will 'block' load and accelerate while connected to the USSTs. After the 30 seconds, the reverse power relay will trip the main generator and transfer the loads to the CSSTs. The fast transfer is accomplished within six cycles and the operating safety related loads will continue operating. The licensee has stated that the transfer scheme will not result in double sequencing.

The licensee has stated that safety related loads will successfully accelerate when connected to the USST following a reactor and turbine trip. The NRC staff has previously reviewed the adequacy and sizing criteria for CSST A and B to support safe shutdown of dual-units assuming a design-basis accident in one unit and simultaneous orderly concurrent shutdown of the other unit. Based on the capacity and capability of USST and CSSTs A and B to provide adequate voltage and power requirements for starting and accelerating accident loads, the staff has concluded that bus transfers from USST to CSST will not adversely impact accident analyses.

RAI item No. AS requested information on circuit breakers associated with isolation and restoration of offsite power. In order to improve the reliability of breaker operations, some designs incorporate redundant coils in the breaker trip and close circuits. The licensee has stated that the breakers associated with normal and alternate offsite sources do not have redundant coils in the trip and close circuits. This design is acceptable as there is no regulatory requirement for redundant coils in these breakers.

The NRC staff reviewed the proposed UFSAR Marked-Up pages for WBN Unit 1 provided in , Attachment 5, of letter dated January 29, 2015. The proposed changes are consistent with the proposed changes in the TSs, which the NRC staff finds are acceptable.

Therefore, the proposed UFSAR changes are acceptable.

3.2 Technical Conclusion The NRC staff has concluded that the existing LCO 3.8.1, which allows 72 hours8.333333e-4 days 0.02 hours 1.190476e-4 weeks 2.7396e-5 months to align an alternate preferred power source to dual-unit operation, is acceptable as it is in alignment with the approved licensing basis. The NRC staff reviewed the system capacity, capability, and timely actions required to restore offsite power to safe shutdown boards through CSST A or B and concluded that the proposed amendment to TS 3.8.1 to use CSST A or B as a GDC 17 source during maintenance of CSST C or D to be acceptable. The proposed SRs for automatic and manual actions necessary to connect two offsite power sources to shutdown boards of two units provide assurance that the proposed paths will restore power for safe shutdown of dual-units in a timely manner consistent with the WBN design basis. The licensee has addressed operability of normal and alternate paths including maintenance requirements. In the event of loss of all the offsite power sources or loss of normal preferred power source, the Class 1E AC buses will be powered from the redundant DGs. The ability to test and use onsite power systems will not be impacted when CSST A or B is aligned as an offsite power source and the transfer capabilities between onsite and offsite power systems are assured by routine surveillances.

The NRC staff concludes that there is reasonable assurance that the equipment required to safely shut down the operating unit(s) and mitigate the effects of a design-basis accident will remain capable of performing the safety function when the alternate preferred power source is connected to the Class 1E buses of the operating unit(s). When one normal preferred power source circuit through CSST C or D is not available, the safety buses of two operating units have two independent offsite power sources, one normal and one alternate, and meet the intent of GDC 17. The NRC staff reviewed the licensee's responses provided to clarify the information provided in the LAR and subsequent communications. Based on the review, the NRC staff concludes that there is reasonable assurance that specific requirements of GDC 5, GDC 18, 10 CFR 50.36, 10 CFR 50.63 and 10 CFR 50.65, as discussed in the evaluation, will continue to be met. Therefore, the staff finds the proposed changes acceptable.

4.0 NO SIGNIFICANT HAZARDS CONSIDERATION The NRC's regulations in 10 CFR 50.92 state that the NRC may make a final determination that a license amendment involves no significant hazards consideration if operation of the facility, in accordance with the amendment, would not: (1) involve a significant increase in the probability

or consequences of an accident previously evaluated; or (2) create the possibility of a new or different kind of accident from any accident previously evaluated; or (3) involve a significant reduction in a margin of safety.

As required by 10 CFR 50.91 (a), an evaluation of the issue of no significant hazards consideration is presented below:

1. Does the proposed change involve a significant increase in the probability or consequences of an accident previously evaluated?

Response: No.

The proposed changes described in this TS amendment request, do not alter the safety functions of the WBN Offsite Power system. Design calculations document that CSSTs A and B have adequate capacity to supply all connected loads including one train of shutdown boards in all allowable alignments and meet the separation requirements for offsite power sources. The consequences of an accident are not changed when using CSST A or B to power the shutdown boards because these CSSTs are rated to carry all required loads for any design basis accidents. The failure of a CSST is not considered to be an initiator of a plant accident and therefore the probability or consequences of accidents or events previously evaluated, as described in the UFSAR, is not changed.

Therefore, this proposed amendment does not involve a significant increase in the probability or consequences of an accident previously evaluated.

2. Does the proposed change create the possibility of a new or different kind of accident from any accident previously evaluated?

Response: No.

As stated above, malfunctions of the CSSTs are not considered to be an initiator for plant accidents and the modifications to the offsite power system do not create a new or different kind of accident. The purpose of the offsite power system is to provide a source of power to the safety related equipment required to mitigate a design basis accident. CSSTs A and B have been physically upgraded and proven by design calculation to meet all required GDC [General Design Criterion] 17 requirements for separation and voltage stability. Using CSSTs A and B as alternate sources of shutdown power does not negatively affect the offsite power systems ability to meet its design function.

Therefore, the proposed amendment does not create the possibility of a new or different kind of accident from any accident previously evaluated.

3. Does the proposed change involve a significant reduction in the margin of safety?

Response: No.

CSSTs A and B have adequate design margin to meet all possible loading scenarios as long as both CSSTs A and B are operational prior to one being used as a source of offsite power. This requirement is added to the control room drawings, plant design criteria and the UFSAR in order to ensure acceptable margin is always available prior to CSSTs A or B being used as a source of offsite power.

Therefore, the proposed changes do not involve a significant reduction in a margin of safety.

Based on the above evaluation, the NRC staff concludes that the three standards of 10 CFR 50.92(c) are satisfied. Therefore, the NRC staff has made a determination that no significant hazards consideration is involved for the proposed amendment and that the amendment should be issued as allowed by the criteria contained in 10 CFR 50.91.

5.0 STATE CONSULTATION

In accordance with the Commission's regulations, the Tennessee State official was notified of the proposed issuance of the amendment on September 3, 2015. The State official had no comments.

6.0 ENVIRONMENTAL CONSIDERATION

The amendment changes a requirement with respect to installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20 and changes surveillance requirements. The NRC staff has determined that the amendment involves no significant increase in the amounts, and no significant change in the types, of any effluents that may be released offsite, and that there is no significant increase in individual or cumulative occupational radiation exposure. The Commission has previously issued a proposed finding that the amendment involves no significant hazards consideration, and there has been no public comment on such finding (80 FR 52348). Accordingly, the amendment meets the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9). Pursuant to 10 CFR 51.22(b),

no environmental impact statement or environmental assessment need be prepared in connection with the issuance of the amendment.

7.0 CONCLUSION

The Commission has concluded, based on the considerations discussed above, that: (1) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, (2) there is reasonable assurance that such activities will be conducted in compliance with the Commission's regulations, and (3) the issuance of the amendment will not be inimical to the common defense and security or to the health and safety of the public.

8.0 REFERENCES

1. Letter from TVA to NRC, "Application to Modify Watts Bar Nuclear Plant, Unit 1 Technical Specifications Regarding AC Sources - Operating (TS WBN-13-02)," dated August 1, 2013 (ADAMS Accession No. ML13220A103)

2. Email from Andrew Hon (NRC) to Joseph W. Shea (TVA), "Watts Bar Nuclear Plant, Unit 1 Request for Additional Information Regarding Application to Modify Technical Specifications Related to AC Sources - Operating (TAC No. MF2549)," dated February 26, 2014 (ADAMS Accession No. ML14056A525)

3. Letter from TVA to NRC, "Response to NRC Request for Additional Information Related to Application to Modify Watts Bar Nuclear Plant, Unit 1 Technical Specifications Related to AC Sources - Operating (TS WBN-13-02)," dated April 21, 2014 (ADAMS Accession No. ML14112A341)

4. Email from Jeanne Dion (NRC) to Gordon Arent (TVA), "RAI 1 for CSST LAR," dated June 2, 2014 (TAC No. MF2549) (ADAMS Accession No. ML14168A613)

5. Letter from TVA to NRC, "Response to NRC Request for Additional Information Related to Application to Modify Watts Bar Nuclear Plant, Unit 1 Technical Specifications Regarding AC Sources - Operating (TS WBN-13-02)," dated January 29, 2015 (ADAMS Accession No. ML15041A732)

6. Email from Anthony Minarik (NRC) to Gordon Arent (TVA), "Final RAls MF2549 WBN, U1 CSST License Amendment Request," dated April 15, 2015 (ADAMS Accession No. ML15105A525)

7. Letter from TVA to NRC, "Response to NRC Request for Additional Information Related to Application to Modify Watts Bar Nuclear Plant, Unit 1 Technical Specifications Regarding AC Sources - Operating (TS-WBN-13-02)" dated June 12, 2015 (ADAMS Accession No. ML15195A600

8. NRC NUREG-0847, Supplement 24, Safety Evaluation Report Related to the Operation of Watts Bar Nuclear Plant, Unit 2, Docket Number 50-391, published September 2011 (ADAMS Accession No. ML11277A148)

9. NRC NUREG-0847, Supplement 28, Safety Evaluation Report Related to the Operation of Watts Bar Nuclear Plant, Unit 2, Docket Number 50-391 dated August 2015 (ADAMS Accession No. ML15229A195)

10. Letter from NRC to TVA, "Watts Bar Nuclear Plant Unit 2 - Request for Additional Information Regarding Licensee's Final Safety Analysis Report Amendment Related to Electrical Engineering Systems (TAC No. ME2731)" dated July 12, 2010 (ADAMS Accession No. ML101530354)

11. Letter from TVA to NRC, "Watts Bar Nuclear Plant (WBN) Unit 2 - Final Safety Analysis Report (FSAR) - Response to Preliminary Requests for Additional Information and Requests for Additional Information," dated July 31, 2010 (ADAMS Accession No. ML102290258).

Contributors: G. Matharu Date: September 29, 2015

September 29, 2015 Mr. Joseph W. Shea Vice President, Nuclear Licensing Tennessee Valley Authority 1101 Market Street, LP 3R-C Chattanooga, TN 37402-2801

SUBJECT:

WATTS BAR NUCLEAR PLANT, UNIT 1 - ISSUANCE OF AMENDMENT REGARDING ALTERNATING CURRENT SOURCES (TAC NO. MF2549)

Dear Mr. Shea:

The U.S. Nuclear Regulatory Commission has issued the enclosed Amendment No. 103 to Facility Operating License No. NPF-90 for the Watts Bar Nuclear Plant, Unit 1. This amendment consists of a change to Technical Specification (TS) 3.8.1, "AC [Alternating Current]

Sources - Operating," Surveillance Requirements 3.8.1.1, 3.8.1.8, 3.8.1.22 and the current licensing basis, as described in the Updated Final Safety Analysis Report, in response to your application dated August 1, 2013, as supplemented by letters dated April 21, 2014, January 29, 2015, and June 12, 2015.

A copy of the related Safety Evaluation is also enclosed. The Notice of Issuance will be included in the Commission's biweekly Federal Register notice. If you have any questions regarding this letter, please contact me at (301) 415-1349.

Sincerely, IRA JPoole for/

Jeanne A. Dion, Project Manager Watts Bar Special Projects Branch Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-390

Enclosures:

1. Amendment No. 103 to NPF-90

2. Safety Evaluation cc w/encls: Distribution via Listserv DISTRIBUTION:

PUBLIC RidsNrrDorlDpr Resource RidsACRS_MailCTR Resource LPWB R/F RidsNrrDorllp_WB Resource RidsRgn2MailCenter Resource RidsNrrDeEeebResource RidsNrrLABClaytonResource RidsNrrPMWattsBar1 Resource RidsNrrDssStsb Resource RidsNrrDorl Resource RidsNrrDe Resource G. Matharu, NRR ADAMS A ccess1on N o.: ML15225A094 *b,,, ema1'I OFFICE NRR/DORL/LPWB/PM NRR/DORL/LPWB/LA NRR/DE/EEEB NRR/DSS/STSB BClayton (RMathew for) (MChernoff for)

NAME JD ion JZimmerman* RElliott DATE 8/26/2015 8/27/2015 8/27/2015 8/28/2015 OFFICE OGC NRR/DORL/LPWB/BC NRR/DORL/LPWB/PM NAME CKanatas JQuichocho (RKuntz for) JDion DATE 9/10/2015 9/29/2015 9/29/2015 OFFICIAL RECORD COPY

v t e Letter Sequence Approval
TAC:MF2549, (Approved, Closed)
Initiation Request, Request Acceptance... Administration Questions 31 March 2015 26 February 2014 16 June 2014 Answers 21 April 2014 29 January 2015 12 June 2015 Results Approval, Approval Other: ML15105A525, ML15232A113, ML15232A116
MONTHYEAR2015-01-29 [Table View]

ML15225A094

Text

SUBJECT:

Dear Mr. Shea:

Enclosures:

Attachment:

1.0 INTRODUCTION

Background

2.0 REGULATORY EVALUATION

3.0 TECHNICAL EVALUATION

5.0 STATE CONSULTATION

6.0 ENVIRONMENTAL CONSIDERATION

7.0 CONCLUSION

8.0 REFERENCES

SUBJECT:

Dear Mr. Shea:

Enclosures:

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