Text

Application to Revise Watt Bar Nuclear Plant, Units 1 & 2, Technical Specifications 3.8.1, 3.8.7, 3.8.8, and 3.8.9, Regarding Electrical Power Systems (WBN-TS-1808)
	ML18331A134
Person / Time
Site:	Watts Bar
Issue date:	11/26/2018
From:	Henderson E; Tennessee Valley Authority
To:	; Document Control Desk, Office of Nuclear Reactor Regulation
References
	CNL-18-119, WBN-TS-18-08
	Download: ML18331A134 (126)
	v • d • e

Tennessee Valley Authority, 1101 Market Street, Chattanooga, Tennessee 37402 CNL-18-119 November 26, 2018 10 CFR 50.90 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D.C. 20555-0001 Watts Bar Nuclear Plant, Unit 1 Facility Operating License No. NPF-90 Docket No. 50-390 Watts Bar Nuclear Plant, Unit 2 Facility Operating License No. NPF-96 Docket No. 50-391

Subject:

Application to Revise Watts Bar Nuclear Plant, Units 1 and 2, Technical Specifications 3.8.1, 3.8.7, 3.8.8, and 3.8.9, Regarding Electrical Power Systems (WBN-TS-18-08)

In accordance with the provisions of Title 10 of the Code of Federal Regulations (10 CFR) 50.90, "Application for amendment of license, construction permit, or early site permit," Tennessee Valley Authority (TVA) is submitting a request for an amendment to the technical specifications (TS) for Watts Bar Nuclear Plant (WBN), Units 1 and 2.

The proposed amendment revises the WBN Unit 1 and Unit 2 TS 3.8.1, AC Sources -

Operating, TS 3.8.7, Inverters - Operating, TS 3.8.8, Inverters - Shutdown, and TS 3.8.9, Distribution Systems - Operating, to support performance of the 6.9 kiloVolt (kV) and 480 Volt (V) shutdown board (SDBD) maintenance. The proposed changes will allow greater operational flexibility for two-unit operation at WBN. Because WBN Unit 2 is now operational, current limitations for the alternating current (AC) electrical power system and associated SDBDs will restrict maintenance with one unit operating. Longer completion times for certain conditions will allow the necessary flexibility to perform the maintenance with one unit defueled, while minimizing risk to the operating unit. Without this proposed change, a dual unit outage would be required to perform breaker and SDBD maintenance activities.

In addition to this proposed license amendment, other changes will be required to facilitate SDBD maintenance. A design change is in progress to add a swing auxiliary air compressor, a separate license amendment request (LAR) is being submitted to adopt Technical Specification Task Force (TSTF) Traveler TSTF-500, Revision 2, DC Electrical Rewrite - Update to TSTF-360, and another LAR submittal is planned for early 2019 to request extension of the Completion Time for an inoperable Essential Raw Cooling Water System train. The requested changes within each LAR do not rely on the approval of the changes contained in the other LARs.

U.S. Nuclear Regulatory Commission CNL-18-119 Page 2 November 26, 2018 provides a description and assessment of the proposed change including the requested confirmation of applicability and plant-specific verifications, technical analyses, regulatory analyses, and environmental considerations. Enclosure 2 provides a simplified drawing of the WBN AC electrical distribution system and a figure indicating the WBN Units 1 and 2 safety-related load distribution across the shared 6.9 kV shutdown boards and associated 480 V shutdown boards. Enclosure 3 provides markups of the existing TS and Bases pages to show the proposed changes. Enclosure 4 provides revised (clean) TS and Bases pages.

The WBN Plant Operations Review Committee has reviewed this proposed change and determined that operation of WBN Units 1 and 2 in accordance with the proposed change will not endanger the health and safety of the public.

TVA .has determined that there are no significant hazard considerations associated with the proposed change and that the change qualifies for a categorical exclusion from environmental review pursuant to the provisions of 10 CFR 51.22(c)(9). Additionally, in accordance with 10 CFR 50.91 (b)(1 ), TVA is sending a copy of this letter and the enclosures to the Tennessee Department of Environment and Conservation.

TVA requests approval of the proposed license amendment within one year from the date of this submittal with implementation of the amendment within 90 days.

There are no new regulatory commitments associated with this submittal. Please address any questions regarding this request to Michael A. Brown at (423) 751-3275.

I declare under penalty of perjury that the foregoing is true and correct. Executed on this 26th day of November 2018.

_lld/ ~

Erin K. Henderson Director, Nuclear Regulatory Affairs

Enclosures:

1. Description and Assessment of Proposed Change

2. Simplified Drawing of the WBN AC Electrical Distribution System

3. Markups of Technical Specification and Bases Changes

4. Clean Technical Specification and Bases Changes cc: See Page 3

U.S. Nuclear Regulatory Commission CNL-18-119 Page 3 November 26, 2018 cc (Enclosures):

NRC Regional Administrator - Region II NRC Project Manager - Watts Bar Nuclear Plant NRC Senior Resident Inspector - Watts Bar Nuclear Plant Director, Division of Radiological Health - Tennessee State Department of Environment and Conservation

Enclosure 1 Description and Assessment of Proposed Change

Subject:

Application to Revise Watts Bar Nuclear Plant, Units 1 and 2, Technical Specifications 3.8.1, 3.8.7, 3.8.8, and 3.8.9, Regarding Electrical Power Systems (WBN-TS-18-08)

TABLE OF CONTENTS 1.0

SUMMARY

DESCRIPTION ............................................................................................. 2 2.0 DETAILED DESCRIPTION.............................................................................................. 2 2.1 Need for Proposed Change ......................................................................................... 2 2.2 Proposed Change ........................................................................................................ 3 2.3 Condition Intended to Resolve ..................................................................................... 5

3.0 TECHNICAL EVALUATION

............................................................................................. 5 3.1 Description of Electrical Power Distribution System ..................................................... 5 3.2 Evaluation .................................................................................................................... 8 3.2.1 TS 3.8.1 Changes ................................................................................................. 8 3.2.2 TS 3.8.7 and TS 3.8.8 Changes ............................................................................ 9 3.2.3 TS 3.8.9 Changes ................................................................................................10 3.3 Conclusion ..................................................................................................................11

4.0 REGULATORY ANALYSIS

............................................................................................11 4.1 Applicable Regulatory Requirement Criteria................................................................11 4.2 Precedent ...................................................................................................................12 4.3 No Significant Hazards Consideration Determination ..................................................12

4.0 ENVIRONMENTAL CONSIDERATION

..........................................................................15

5.0 REFERENCES

...............................................................................................................15 CNL-18-119 E1-1 of 19

Enclosure 1 Description and Assessment of Proposed Change 1.0

SUMMARY

DESCRIPTION The Tennessee Valley Authority (TVA) is requesting a license amendment to the Watts Bar Nuclear Plant (WBN) Unit 1 and Unit 2 Technical Specifications (TS) 3.8.1, AC Sources - Operating, TS 3.8.7, Inverters - Operating, TS 3.8.8, Inverters - Shutdown, and TS 3.8.9, Distribution Systems - Operating, to support performance of 6.9 kilovolt (kV) and 480 volt (V) shutdown board (SDBD) maintenance.

Because WBN Units 1 and 2 share the Class 1E electrical power distribution system, the TS do not provide sufficient time to perform the 15-year preventive maintenance on the 6.9kV SDBDs and the associated 480V SDBDs. Maintenance on a 6.9kV SDBD associated with a unit defueled cannot be performed, because the Limiting Condition for Operation (LCO) for the unit operating in Mode 1, 2, 3, or 4 requires the 6.9kV SDBDs and 480V SDBDs associated with the other unit to be operable. Therefore, dual unit outages are required in order to perform this maintenance. TVA does not currently have any plans to conduct dual unit outages for WBN Units 1 and 2. A seven-day allowed outage time would permit maintenance to be performed on the 6.9kV and 480V SDBDs for the unit defueled, while the opposite unit is operating in Mode 1, 2, 3, or 4.

The license amendment is similar to the Sequoyah Nuclear Plant (SQN) Units 1 and 2 changes that were included in the Improved Technical Specification (ITS) submittal that were approved by the Nuclear Regulatory Commission (NRC) in Reference 1.

The WBN Units 1 and 2 TS 3.8.9 and Bases markups and clean typed TS and markups in Enclosures 3 and 4 reflect the proposed changes provided in Reference 2 that are currently under NRC review.

2.0 DETAILED DESCRIPTION 2.1 NEED FOR PROPOSED CHANGE The operability requirements for the 6.9 kV and 480 V SDBDs are defined in WBN Units 1 and 2 LCO 3.8.9 for Modes 1, 2, 3, and 4, and LCO 3.8.10 for Modes 5 and 6.

LCO 3.8.9 requires the four 6.9 kV SDBDs and eight 480 V SDBDs whenever a unit is in Modes 1, 2, 3, and 4. LCO 3.8.10 requires two 6.9 kV SDBDs (either 6.9k V SDBDs 1A-A and 2A-A or 1B-B and 2B-B), and the four associated 480 V SDBDs to be operable whenever a unit is in Modes 5 and 6. If a 6.9 kV or 480 V SDBD is inoperable or de-energized while either unit is in Mode 1, 2, 3, or 4, LCO 3.8.9, Condition A, requires the inoperable SDBD to be restored to an operable status within eight hours or actions taken to place the unit in a Mode that the LCO does not apply.

Preventive maintenance (PM) to clean and inspect the 6.9 kV and 480 V SDBDs is required every 15 years to ensure the reliability of the Standby AC Power System. PM activities associated with the switchgear include:

Insulation resistance testing (megger)

Inspection and micro-ohm resistance measurements

Inspecting, cleaning, and lubricating primary stabs

Cleaning rear compartments by vacuuming and wiping buses and insulators with alcohol and rags CNL-18-119 E1-2 of 19

Enclosure 1 Description and Assessment of Proposed Change

Pulling rear panels of potential transformer cabinets, inspecting components, and lubricating bus connections, and

Performing additional work orders to address equipment issues (e.g., cell switch replacements, fuse block replacements) as allowed within the Completion Times The duration that the SDBDs will be inoperable to perform the PM includes the following time estimates based on past performance of the maintenance, with additional time allowed for unforeseen circumstances that require a total of seven days:

12 hours1.388889e-4 days 0.00333 hours 1.984127e-5 weeks 4.566e-6 months for clearance placement and removal

Nine hours for ground placement and removal

42 hours4.861111e-4 days 0.0117 hours 6.944444e-5 weeks 1.5981e-5 months for inspections of compartments (21 compartments) o E-16 light resistor replacements o pull-out fuse block tension o relay and instrument o potential transformer drawer operation

34 hours3.935185e-4 days 0.00944 hours 5.621693e-5 weeks 1.2937e-5 months for circuit breaker interface inspections and adjustments (17 breakers) o primary/secondary disconnects o shutters o breaker position and interface measurements and adjustments

Eight hours for bus inspection and tests o as-found and as-left megger o DLRO o torque checks Prior to commercial operation of WBN Unit 2, the PM for the 6.9 kV and 480 V SDBDs could be performed during a WBN Unit 1 scheduled refueling outage. Because WBN Units 1 and 2 share the Class 1E electrical power distribution system, de-energizing the SDBDs to perform the PM affects both units. The current TS for an operating unit do not provide sufficient time to perform the 15-year PM on the 6.9 kV and 480 V SDBDs. Therefore, the current TS would require a dual outage to perform the PM. The PM is normally performed over several refueling outages with one set of 6.9 kV and 480 V SDBDs being cleaned and inspected during a refueling outage. The next planned performance of the PM is during refueling outage U1R16 (Spring 2020).

Therefore, an extension of the LCO Action Completion Times to seven days for the affected systems would permit performance of the PM while one unit is in Modes 1, 2, 3, or 4 and the other unit is defueled.

2.2 PROPOSED CHANGE

The proposed change extends the LCO 3.8.9 Completion Time for one or more inoperable 6.9 kV and 480 V SDBDs in a subsystem by separating the existing Condition A into two Conditions. One Condition would apply to one or more inoperable associated unit SDBDs in a subsystem and the other Condition would apply to one or more inoperable opposite unit SDBDs in a subsystem. The Condition that applies to the associated unit's SDBDs would retain the current TS requirements. The Condition that applies to the opposite unit's SDBDs would require that the associated required features be declared inoperable. Therefore, the associated Conditions and Required Actions of the required features would be entered. (See Tables 1 - 4 in this enclosure for a listing CNL-18-119 E1-3 of 19

Enclosure 1 Description and Assessment of Proposed Change of the major safety-related loads powered from each set of 6.9 kV and 480 V SDBDs and the current TS Completion Time associated with declaring each required feature inoperable.)

The proposed change will apply required actions commensurate with the safety significance of the affected systems.

As shown in Tables 1 - 4, the current TS required actions would limit the Completion Time for one or more inoperable 6.9 kV and 480 V SDBDs in a subsystem to two hours for an inoperable vital battery subsystem. Therefore, TVA is proposing adoption of TSTF-500, in a separate license amendment request to allow a vital battery charger to be inoperable for seven days.

WBN Units 1 and 2 TS 3.8.1, 3.8.7, 3.8.8, and 3.8.9 are being revised as shown in Enclosures 3 and 4. A description of the changes in this LAR is provided below:

TS 3.8.1

Added a new Condition D for when one offsite circuit is inoperable solely due to an offsite power source to an opposite unit's 6.9 kV SDBD is inoperable. The Condition is modified by two notes that establish an applicability of during planned maintenance of an opposite unit AC electrical distribution subsystem when the opposite unit is defueled.

Revised Condition A to indicate that it applies when an offsite circuit is inoperable for reasons other than the new Condition D.

Revised Condition F (currently Condition E) to apply when an offsite circuit is inoperable for reasons other than Condition D. The note modifying Required Action F.1 (formerly Required Action E.1) has been modified as shown below and moved to the Actions Notes for TS 3.8.1 such that the note applies when any LCO 3.8.1 Condition is entered:

"2. Enter applicable Conditions and Required Actions of LCO 3.8.9, 'Distribution Systems - Operating,' when any Condition(s) is entered with no AC power source to any shutdown board resulting in a de-energized shutdown board."

Renumbered subsequent Conditions and Required Actions accordingly.

TS 3.8.7 and TS 3.8.8

Revised SR 3.8.7.1 and SR 3.8.8.1 to remove the details that correct inverter voltage, frequency, and alignment to the required AC vital bus includes verification from associated vital battery board and 480 V shutdown board.

CNL-18-119 E1-4 of 19

Enclosure 1 Description and Assessment of Proposed Change TS 3.8.9

Added a new Condition F for when one or more AC electrical distribution subsystems inoperable due to one or more opposite unit shutdown boards inoperable. The Required Action is immediately declaring the associated required features inoperable. The Condition is modified by two notes that establish an applicability of during planned maintenance of an opposite unit AC electrical distribution subsystem when the opposite unit is defueled.

Added a new Condition G to address when one or more AC electrical distribution subsystems inoperable due to one or more opposite unit shutdown boards inoperable for reasons other than Condition F. The Required Action is to restore the opposite unit electrical power distribution subsystems to an operable status within 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months .

Revised Condition A to indicate that it applies when one or more AC electrical power distribution subsystems are inoperable due to one or more associated units AC shutdown boards inoperable.

Renumbered subsequent Conditions and Required Actions accordingly.

Enclosure 3 provides the existing WBN Units 1 and 2 TS and Bases pages marked-up to show the proposed changes. Enclosure 4 provides the clean typed TS and Bases pages with the proposed changes incorporated. The marked up and clean typed TS and Bases reflect the proposed changes provided in Reference 2 for NRC review and approval.

The proposed Bases changes are provided for information only.

2.3 CONDITION INTENDED TO RESOLVE The proposed changes will allow greater operational flexibility for two-unit operation at WBN. Because WBN Unit 2 is now operational, current limitations for the associated SDBDs will restrict maintenance with one unit operating. Longer completion times for certain conditions will allow the necessary flexibility, while minimizing risk to the operating unit. Without this proposed change, a dual unit outage would be required to perform breaker and SDBD maintenance.

3.0 TECHNICAL EVALUATION

3.1 DESCRIPTION

OF ELECTRICAL POWER DISTRIBUTION SYSTEM 6.9 kV and 480 Electrical Power Distribution System The WBN electrical power distribution system AC sources consist of the offsite power sources (preferred power sources) and the onsite standby power sources [Train A and Train B diesel generators (DGs)]. The onsite Class 1E AC electrical power distribution system is divided into two redundant and independent load groups (i.e., A and B) with two 6.9 kV SDBDs in each load group (i.e., 1A-A and 2A-A in load group A, and 1B-B CNL-18-119 E1-5 of 19

Enclosure 1 Description and Assessment of Proposed Change and 2B-B in load group B) and the associated 480 V SDBDs (see Figures 1 and 2).

Each 6.9 kV SDBD is connected to one of the preferred offsite power sources or to a DG in case the preferred offsite power source is lost. Two DGs associated with one load group (e.g., 1A-A and 2A-A) can provide all safety-related functions to mitigate a loss-of-coolant accident (LOCA) in one unit and safely shut down the other unit. The Train A and Train B engineered safety features (ESF) systems each provide for the minimum safety functions necessary to shut down the plant and maintain it in a safe shutdown condition.

Offsite power is supplied to the Watts Bar 161 kV transformer yard by two dedicated lines from the Watts Bar Hydro Plant switchyard. From the 161 kV transformer yard, two electrically and physically separated circuits provide AC power through stepdown common station service transformers (CSSTs) C and D to the 6.9 kV SDBDs. The two offsite AC electrical power sources are designed and located to minimize to the extent practical the likelihood of their simultaneous failure under operating and postulated accident and environmental conditions.

The onsite standby power source for each 6.9 kV SDBD is a dedicated DG. DGs 1A-A, 1B-B, 2A-A, and 2B-B are separate and independent and are dedicated to 6.9 kV SDBDs 1A-A, 1B-B, 2A-A, and 2B-B, respectively. Each DG set consists of two diesel engines in tandem driving a common generator. A DG starts automatically on a safety injection (SI) signal (e.g., low pressurizer pressure, high containment pressure, or low steam line pressure signals), a 6.9 kV SDBD degraded voltage, or a loss-of-voltage signal. After a DG has started, it can automatically tie to its respective 6.9 kV SDBD after offsite power is tripped as a consequence of a 6.9 kV SDBD degraded voltage or loss-of-voltage signal, independent of or coincident with an SI signal.

Following the trip of offsite power, a loss-of-voltage signal strips most of the non-permanent loads from the 6.9 kV SDBD. After the DG is tied to the 6.9 kV SDBD, loads are sequentially connected to its respective 6.9 kV SDBD by individual load sequence timers. The DGs are automatically connected to the 6.9 kV SDBDs in sufficient time to provide for safe reactor shutdown and to mitigate the consequences of a design basis accident (DBA). The required loads needed to recover the unit or maintain it in a safe condition are returned to service in a predetermined sequence in order to prevent overloading the DG in the process.

The onsite electrical power distribution system is divided into two redundant and independent trains. The core cooling systems and containment systems [e.g., SI, auxiliary feedwater (AFW), residual heat removal (RHR), centrifugal charging (CC),

containment spray, and air return system] are unitized (i.e., not shared among the units).

However, some safety related systems [e.g., essential raw cooling water (ERCW),

component cooling water (CCW) system, emergency gas treatment (EGTS), auxiliary building gas treatment, (ABGTS), control room emergency ventilation (CREVS), and control room air conditioning (CRACS)] are shared by the two units. The AC sources for these shared loads are distributed across all four 6.9 kV SDBDs, and associated downstream 480 V SDBDs. See Tables 1 - 4 for a list of major safety-related loads powered from each 6.9 kV SDBD and associated 480 V SDBDs.

CNL-18-119 E1-6 of 19

Enclosure 1 Description and Assessment of Proposed Change 120 VAC Vital Power System The 120 VAC vital power system is a Class 1E system, which provides a reliable source of instrument and control power for reactor protection circuits and other critical instrumentation systems and components within the plant. The system configuration and the load arrangement preclude the loss of any redundant essential and/or protective function due to a single failure within the system.

The system for each unit consists of four uninterruptible power supplies (UPS) with distribution boards and associated cabling, instrumentation, and protective devices.

Each unit has four identical power channels (designated as Channels I, II, III, and IV),

with the equipment of each channel being electrically and physically independent from the equipment of other channels, so that a failure in one channel will not cause a failure in another channel. Each channel consists of a unit UPS, a spare UPS, and a distribution board that facilitates load grouping and provides circuit protection.

Each 120 VAC vital channel has access to several power sources: Two 480 VAC sources, a 125 V DC source, and a 120 VAC regulated transformer bypass source.

Alternating current power for each UPS is derived from the Class 1E auxiliary power system via two 480 VAC circuits. If the normal 480 VAC circuit supplying a UPS is unavailable, the alternate circuit may be selected by a manual transfer. The DC input power source is derived from the Class 1E 125 VDC vital power system. The normal source to each 120 VAC vital instrument power board is from its associated unit UPS system, the alternate source is from its associated spare UPS system. Input power from the alternate source is delivered to the 120 VAC vital instrument boards loads via a manually-operated transfer switch. The spare UPS may be substituted for either unit UPS on the same channel.

A regulated transformer bypass source is also available from the unit UPS and is derived from the 480 VAC shutdown board system. The input power is delivered to the 120 VAC vital instrument power board via the same cable as the normal unit inverter output. This source provides a temporary power supply while the boards inverter source is unavailable or out of service.

The unit UPSs consist of four major subassemblies: a DC power supply, an auctioneering circuit, a regulated transformer bypass source circuit, and an inverter circuit. During normal operation, the UPS's DC power supply converts the 480 VAC normal UPS input to 125 VDC. The auctioneering circuit accepts this DC power supply (normal supply) and the 125 V vital battery board input (emergency supply) and provides a switchless bidirectional transfer between the two sources in the event of a 480 VAC supply failure and restoration. Thus, during an emergency in which all 480 VAC power is lost to the UPS, the auctioneering circuit will automatically switch to the battery board input. The DC output at the auctioneering circuit is then converted by the inverter circuitry to a regulated 120 VAC output to the distribution boards.

CNL-18-119 E1-7 of 19

Enclosure 1 Description and Assessment of Proposed Change 3.2 EVALUATION 3.2.1 TS 3.8.1 Changes A new Condition D is being added to TS 3.8.1 for when one offsite circuit is inoperable solely due to an inoperable offsite power source to an opposite unit's 6.9 kV SDBD.

Condition D considerations are required because the 6.9 kV SDBDs of the opposite unit feed some systems shared between the units. This change will provide completion times commensurate with the affected shared systems to support performance of maintenance activities when the opposite unit is defueled and planned maintenance is being performed on an opposite unit AC electrical power distribution subsystem.

The associated actions and completion times for the new TS 3.8.1 Condition D require:

Perform SR 3.8.1.1 for the required operable offsite circuit in 1 hour1.157407e-5 days 2.777778e-4 hours 1.653439e-6 weeks 3.805e-7 months .

Declare the required feature(s), with no offsite power available inoperable when its redundant required feature(s) is inoperable, in 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months from discovery of no offsite power to the opposite unit's 6.9 kV SDBDs.

Restore the offsite circuit to operable status in seven days.

In conjunction with the new TS 3.8.1 Condition D, TS 3.8.1 Condition A is being modified to apply when one offsite circuit is inoperable for reasons other than Condition D. This change also requires the 24 hour2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months completion time to be modified by specifying that the required features are declared inoperable with regard to the discovery of no offsite power to the associated units 6.9 kV SDBD. TS 3.8.1 Conditions A and D are being evaluated together to assess the effect of an inoperable offsite circuit on one 6.9 kV SDBD and both 6.9 kV SDBDs in a train.

The purpose of the new Condition D and changes to Condition A is to create separate actions that address the reduced risk to the associated unit when the loss of offsite power only affects the opposite units 6.9 kV SDBD during planned maintenance with the opposite unit in the defueled condition, versus the loss of an offsite circuit for other reasons.

TS 3.8.1 Required Actions A.1 and A.2 and new D.1 and D.2 are consistent with the current TS. The completion time of Required Action A.3 remains unchanged at 72 hours8.333333e-4 days 0.02 hours 1.190476e-4 weeks 2.7396e-5 months . The seven-day completion of new Required Action D.3 for restoring the offsite circuit to operable status takes into account the capacity and capability of the remaining AC sources providing electrical power to the required feature(s), a reasonable time for repairs and the low probability of a DBA occurring during this period of time. This completion time also allows for the performance of maintenance that will ensure continued system reliability. The completion time takes into consideration the shared systems powered from the opposite unit's 6.9 kV SDBD, that the shared systems are fully redundant, and that the affected 6.9 kV SDBD does not provide power to core cooling or containment cooling loads for the associated unit (see Tables 1 - 4).

Therefore, the proposed changes to TS 3.8.1 Condition A are acceptable, because there are no changes to the actions or completion times for an inoperable offsite circuit for CNL-18-119 E1-8 of 19

Enclosure 1 Description and Assessment of Proposed Change reasons other than Condition D. The proposed new TS 3.8.1 Condition D fully addresses the loss of an offsite power source affecting the opposite units 6.9 kV SDBD during planned maintenance with the opposite unit defueled. The new TS 3.8.1 Condition D is acceptable because the completion times for Required Action D.1 and Required Action D.2 are consistent with the current TS requirements. Additionally, the completion time for Required Action D.3 applies an appropriate completion time for the restoration of systems shared between the units that do not include core cooling and containment cooling loads for the associated unit.

3.2.2 TS 3.8.7 and TS 3.8.8 Changes TS 3.8.7, SR 3.8.7.1, and TS 3.8.8, SR 3.8.8.1, are being changed to remove the details that the vital inverter is aligned to its associated vital battery and 480 V shutdown board.

The details that the inverter has an input from the 125 VDC vital battery are included in the TS Bases 3.8.7.

The function of the vital inverters is to provide AC electrical power to the AC vital buses.

The inverters can be powered from an internal AC source/rectifier or from the vital battery. The design basis of the vital inverters is to provide the required capacity, capability, redundancy, and reliability to ensure the availability of necessary power to the Reactor Protective System (RPS) and the Engineered Safety Feature Actuation System (ESFAS) instrumentation and controls so that the fuel, Reactor Coolant System, and containment design limits are not exceeded. The operability requirements of the inverters are consistent with the initial assumptions of the accident analyses and are based on meeting the design basis of the plant. This includes maintaining required AC vital buses operable during accident conditions in the event of an assumed loss of all offsite AC electrical power or all onsite AC electrical power and a worst-case single failure.

As described in TS Bases 3.8.7, LCO Section, "OPERABLE inverters require the associated AC vital bus to be powered by an inverter with output voltage and frequency within tolerances and power input to the inverter from a 125 VDC vital battery.

Alternatively, power supply may be from an internal AC source via rectifier as long as the vital battery is available as the uninterruptible power supply."

Therefore, the proposed change to SR 3.8.7.1 and SR 3.8.8.1 to remove the details that the vital inverter is aligned to its associated vital battery and 480 V shutdown board is acceptable, because it is the vital batteries that provide the uninterruptible power source to the safety-related 120 VAC loads. During an emergency in which all 480 VAC power is lost to the UPS, the auctioneering circuit automatically switches to the battery board input. Alignment of the 480 V power supply to the inverters is allowed when the vital battery is available as the uninterruptible power supply. Therefore, removing the requirement for the vital inverters to be aligned to its associated 480 V power supply is consistent with the design basis of the plant. This change also aligns SR 3.8.7.1 and SR 3.8.8.1 with NUREG-1431.

CNL-18-119 E1-9 of 19

Enclosure 1 Description and Assessment of Proposed Change 3.2.3 TS 3.8.9 Changes The proposed changes to TS 3.8.9 make distinctions between the WBN Unit 1 and the WBN Unit 2 electrical distribution system to support a two-unit electrical distribution system.

Condition A The proposed change to Condition A requires restoration of one or more inoperable AC electrical power distribution subsystems due to one or more AC SDBDs on the associated unit within the eight hours. The proposed change retains the current requirement for an inoperable AC electrical power distribution subsystem due to inoperable AC SDBDs on the associated unit and does not change the completions time associated with the action. Required actions for inoperable AC electrical power distribution subsystems due to inoperable AC SDBDs on the opposite unit are addressed in the proposed new Conditions F and G as discussed below.

Condition F The proposed Condition F requires that when one or more AC electrical power distribution subsystems is inoperable due to one or more SDBDs on the opposite unit being inoperable, to immediately declare associated required feature(s) inoperable.

Proposed Condition F is modified by two notes. Note 1 states the Condition is only applicable during planned maintenance of an opposite unit's AC electrical distribution subsystem. Note 2 states the Condition is only applicable when the opposite unit is defueled. This changes the TS by providing an action to declare the required supported feature(s) powered from the inoperable SDBD inoperable and thereby follow the Conditions and Required Actions for the affected systems.

As discussed in Section 3.1 and indicated in Tables 1 - 4 of this enclosure, an opposite unit's SDBDs provide electrical power to systems shared by the units and do not provide electrical power to reactor core cooling or containment cooling systems on the operating unit. Therefore, the proposed Condition D addresses the effects on the operating unit of inoperable shared features while the opposite unit is under specific mode restrictions for maintenance. The shared features are fully redundant. If a redundant train of an affected feature becomes inoperable, TS 3.8.1, Condition B and proposed Condition D, would require the inoperable DG or inoperable offsite circuit, respectively, to be restored to an operable status within the specified Completion Times.

The Conditions and Required Actions of the affected shared features ensure appropriate risk management for the operating unit while placing limitations on the length of time the opposite units AC electrical power distribution subsystem can be inoperable. This proposed change provides an extended timeframe for the performance of maintenance activities such as SDBD inspections and cleaning that ensure AC electrical power distribution subsystem reliability.

This proposed Condition F is acceptable because there are a limited number of shared features, there is adequate redundancy provided by the shared features, and the associated unit TS restrictions are being maintained. This change establishes independent conditions for the shared features apart from their tied AC electrical CNL-18-119 E1-10 of 19

Enclosure 1 Description and Assessment of Proposed Change distribution subsystem, such that the associated unit is able to continue to operate safely and within Technical Specification requirements.

Condition G Proposed Condition G requires that when one or more AC electrical power distribution subsystems are inoperable due to one or more of the opposite units SDBDs inoperable for reasons other than Condition F, that the opposite units electrical power distribution system is to be restored to operable status in 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months . This proposed change recognizes the impacts of the shared features and systems on a dual unit site where both units are operating above the mode restrictions of proposed Condition F.

The Required Action associated with the required features are used to establish remedial measures that must be taken in response to the degraded conditions in order to minimize risk associated with continued operation, while providing time to address an inoperable condition. If the individual features completion time cannot be met, the applicable conditions for the affected shared system LCOs establish the required actions to either restore the feature to an operable status or exit the mode of applicability for that inoperable require feature. The provided actions effect restoration of the opposite units AC electrical power distribution subsystem commensurate with the importance of maintaining these AC electrical power subsystems capable of supporting the associated units required features.

3.3 CONCLUSION

The proposed changes are consistent with the design and operation of the WBN units.

The changes maintain the current requirements for the SDBDs associated with each unit. The changes allow an opposite unit SDBD providing power to shared systems to be inoperable for a duration that is consistent with the allowed outage time for the shared systems. This change will allow greater operational flexibility for two-unit operation and allow the performance of maintenance on the 6.9 kV and 480 V SDBDs without requiring a dual unit outage while minimizing risk to the operating unit.

4.0 REGULATORY ANALYSIS

4.1 APPLICABLE REGULATORY REQUIREMENT CRITERIA Title 10 of the Code of Federal Regulations (10 CFR) Part 50, Appendix A, General Design Criterion (GDC) 17, Electric power systems, states, in part, that:

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 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. Electric power from the transmission network to the onsite electric distribution system shall be supplied by two physically independent circuits (not necessarily on separate rights of way) 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. Provisions shall be included to minimize the probability of losing electric power from any of the remaining CNL-18-119 E1-11 of 19

Enclosure 1 Description and Assessment of Proposed Change supplies as a result of, or coincident with, the loss of power generated by the nuclear power unit, the loss of power from the transmission network, or the loss of power from the onsite electric power supplies.

GDC 18, Inspection and testing of electric power systems, states, in part, electric power systems important to safety shall be designed to permit appropriate periodic inspection and testing of important areas and features.

GDC 5, Sharing of structures, systems, and components, requires 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.

GDC 1, Quality standards and records, requires that structures, systems, and components important to safety shall be designed, fabricated, erected, and tested to quality standards commensurate with the importance of the safety functions to be performed.

Regulatory Guide 1.93, Revision 0, Availability of Electrical Power Sources, provides guidance with respect to operating procedures and restrictions acceptable to the NRC that should be implemented if the available electric power sources are less than the LCO for a facility.

4.2 PRECEDENT The proposed changes are consistent with the SQN ITS (Reference 1) and the Westinghouse Standard TS (NUREG-1431).

4.3 NO SIGNIFICANT HAZARDS CONSIDERATION DETERMINATION Tennessee Valley Authority (TVA) has evaluated the proposed changes to the Technical Specifications (TS) using the criteria in Section 50.92 to Title 10 of the Code of Federal Regulations (10 CFR) and has determined that the proposed changes do not involve a significant hazards consideration.

The proposed amendment would revise TS requirements related to alternating current (AC) electrical systems in TS limiting condition for operation (LCO) 3.8.1, AC Sources -

Operating, LCO 3.8.7, Inverters - Operating, LCO 3.8.8, Inverters - Shutdown, and LCO 3.8.9, Distribution Systems - Operating.

The proposed changes will allow greater operational flexibility for two-unit operation at the Watts Bar Nuclear Plant (WBN). Because WBN Unit 2 is now operational, current limitations for the vital power and associated shutdown boards (SDBDs) will restrict maintenance with one unit operating. Longer completion times for certain conditions will allow the necessary flexibility, while minimizing risk to the operating unit. Without this proposed change, a dual unit outage would be required to perform breaker and SDBD maintenance.

CNL-18-119 E1-12 of 19

Enclosure 1 Description and Assessment of Proposed Change The safety function of the Standby AC Power System is to supply power to support the functioning of components and systems required to assure that (1) fuel design limits and reactor coolant pressure boundary design conditions are not exceeded due to anticipated operational occurrences, and (2) the core is cooled and vital functions are maintained in the event of postulated accidents, subject to loss of the Preferred Power System and subject to any single failure in the Standby Power System. To accomplish its safety function, the onsite Class 1E AC distribution system supplies electrical power to two power trains for each unit. Each power train includes two Class 1E 6.9 kV SDBDs powered from one of two separate and independent offsite power lines or a dedicated onsite DG. Two DGs in one train can provide the safety related functions to mitigate a loss-of-coolant accident (LOCA) in one unit and safely shut down the other unit.

The core cooling and containment cooling system loads are unitized to the respective unit's 6.9 kV SDBDs. Although the core cooling systems and containment systems credited in the mitigation of an anticipated operational occurrence (AOO) or postulated Design Basis Accident (DBA) are unitized (not shared with the opposite unit) and powered from the associated unit's SDBDs, some safety related systems [e.g., Essential Raw Cooling Water (ERCW), Component Cooling (CCS), Emergency Gas Treatment (EGTS), Auxiliary Building Gas Treatment, (ABGTS), Control Room Emergency Ventilation (CREVS), and Control Room HVAC (CRACS)] are shared between the units.

The AC sources for these loads are distributed across both units SDBDs. Therefore, in addition to requiring the associated unit's boards to be operable, the opposite unit's boards supplying power to a required shared system component is also required to be operable.

The proposed changes are consistent with Improved Technical Specifications (ITS) as outlined in NUREG-1431, "Standard Technical Specifications, Westinghouse Plants,"

and the Sequoyah Nuclear Plant (SQN) ITS. The proposed new Required Actions are consistent with safe operation under the specified Condition, considering the operable status of the redundant systems or features. This includes the capacity and capability of remaining systems or features, a reasonable time for repairs or replacement, and the low probability of a design basis accident occurring during the repair period. These changes are acceptable because the Required Actions associated with the required features are used to establish remedial measures that must be taken in response to the degraded conditions in order to minimize risk associated with continued operation, while providing time to repair the inoperable features. If the necessary repairs cannot be made within the established Completion Time, the applicable Conditions for the affected shared system limiting conditions for operation establish the Required Actions to exit the Mode of Applicability for that inoperable required feature. This change is acceptable because the provided actions effect restoration of the opposite unit's AC boards commensurate with the importance of maintaining these AC boards capable of supporting the associated unit's required feature(s).

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

CNL-18-119 E1-13 of 19

Enclosure 1 Description and Assessment of Proposed Change

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

Response: No.

The proposed change modifies the required actions for the opposite unit's onsite and offsite AC power sources and electrical distribution system. The opposite unit's AC power sources, electrical distribution system are required to be operable to support the associated unit's required features. In addition, a change is proposed to remove the details regarding the required input power to the vital inverters. This change will not affect the probability of an accident, since the AC power sources, vital inverters, and electrical distribution system are not initiators of any accident sequence analyzed in the WBN dual-unit Updated Final Safety Analysis Report (UFSAR). Rather, the AC power sources, vital inverters, and electrical distribution system support equipment used to mitigate accidents. The consequences of an analyzed accident will not be significantly increased since the minimum requirements for AC power sources, vital inverters, and electrical distribution system will be maintained to ensure the availability of the required power to mitigate accidents assumed in the UFSAR. Operation in accordance with the proposed TS will ensure that sufficient AC power sources, vital inverters, and electrical distribution subsystems are operable, as required to support the unit's required features.

Therefore, the mitigating functions supported by the AC power sources, vital inverters, and electrical distribution system will continue to provide the protection assumed by the accident analysis. The integrity of fission product barriers, plant configuration, and operating procedures as described in the UFSAR will not be affected by the proposed changes. Thus, the consequences of previously analyzed accidents will not increase by implementing these changes. Therefore, the proposed changes do not involve a significant increase in the probability or consequences of an accident previously evaluated.

Therefore, the proposed change 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 previously evaluated?

Response: No The proposed changes involve restructuring the TS for the AC electrical power system to provide more flexibility in performing maintenance on electrical system components.

The AC electrical power system is not an initiator to any accident sequence analyzed in the UFSAR. Rather, the AC electrical power system supports equipment used to mitigate accidents. The proposed changes to modify the required actions associated with inoperable opposite unit AC power sources and shutdown boards and proposed changes to the details of the required power supplies to the vital inverters will maintain the same level of equipment performance required for mitigating accidents assumed in the UFSAR. Therefore, operation of the facility in accordance with this proposed change will not create the possibility of a new or different kind of accident from any accident previously evaluated.

CNL-18-119 E1-14 of 19

Enclosure 1 Description and Assessment of Proposed Change

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

Response: No.

The margin of safety is established through equipment design, operating parameters, and the setpoints at which automatic actions are initiated. The equipment margins will be maintained in accordance with the plant-specific design bases as a result of the proposed changes. The proposed changes will not adversely affect operation of plant equipment. These changes will not result in a change to the setpoints at which protective actions are initiated. Sufficient AC capability to support operation of mitigation equipment is ensured. The equipment fed by the AC electrical sources will continue to provide adequate power to safety-related loads in accordance with analysis assumptions. The proposed TS changes maintain the same level of equipment performance stated in the UFSAR and the current TSs. Therefore, the proposed changes do not involve a significant reduction of safety.

4.0 ENVIRONMENTAL CONSIDERATION

The proposed TS change would change 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 would change an inspection or surveillance requirement. However, the proposed change does not involve (i) a significant hazards consideration, (ii) a significant change in the types or significant increase in the amounts of any effluent that may be released offsite, or (iii) a significant increase in individual or cumulative occupational radiation exposure. Accordingly, the proposed TS change meets the eligibility criterion for categorical exclusion set forth in 10 CFR 51.22(c)(9). Therefore, pursuant to 10 CFR 51.22(b), no environmental impact statement or environmental assessment need be prepared in connection with the proposed TS change.

5.0 REFERENCES

1. NRC Letter to TVA, "Sequoyah Nuclear Plant, Units I and 2 - Issuance of Amendments for the Conversion to the Improved Technical Specifications with Beyond Scope Issues (TAC Nos. MF3128 AND MF3129)," dated September 30, 2015 (ML15238B460)

2. TVA letter to NRC, CNL-17-119, Application to Modify Watts Bar Nuclear Plant, Units 1 and 2 Technical Specifications 3.8.9 Regarding Alternating Current (AC) Vital Buses (WBN-TS-17-19), dated February 28, 2018 (ML18060A337)

CNL-18-119 E1-15 of 19

Enclosure 1 Description and Assessment of Proposed Change Table 1 Affected Major Loads - De-energize 6.9 kV SDBD 1A-A and Associated 480 V SDBDs Unit 1 Systems Required Modes U1 / U2 TS CT1 Safety Injection pump 1A-A 1, 2, 3 NA / NA AFW pump 1A-A 1, 2, 3, 4 NA / NA RHR pump 1A-A 1, 2, 3, 4, 5, 6 NA / NA Charging pump 1A-A 1, 2, 3, 4 NA / NA Cont. Spray pump 1A-A 1, 2, 3, 4 NA / NA Air Return System fan 1A-A 1, 2, 3, 4 NA / NA Pressurizer Heater Groups 1A, 1D 1, 2, 3 NA / NA Shared Systems Required Modes U1 / U2 TS CT1 Proposed U2 TS CT ERCW pumps A-A, C-A 1, 2, 3, 4, 5 NA / 72 hours8.333333e-4 days 0.02 hours 1.190476e-4 weeks 2.7396e-5 months 7 days3 CCS pump 1A-A 1, 2, 3, 4, 5 NA / NA2 CCS pump C-S (Alternate Feeder) 1, 2, 3, 4, 5 NA / NA2 EGTS fan A-A 1, 2, 3, 4 NA / 7 days Control Room AHU A-A 1, 2, 3, 4, 5, 6, Irrad. Fuel Movement 30 days / 30 days CREVS fan A-A 1, 2, 3, 4, 5, 6, Irrad. Fuel Movement 7 days / 7 days CREVS radiation monitor 1, 2, 3, 4, 5, 6, Irrad. Fuel Movement 7 days / 7 days 125 V Vital Battery Charger I 1, 2, 3, 4, 5, 6, Irrad. Fuel Movement NA2 / 2 hours2.314815e-5 days 5.555556e-4 hours 3.306878e-6 weeks 7.61e-7 months 7 days3 120 V Vital Inverters 1-I, 2-I 1, 2, 3, 4, 5, 6, Irrad. Fuel Movement NA2 / 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months NA AC electrical power distribution boards 1, 2, 3, 4, 5, 6, Irrad. Fuel Movement NA2 / 8 hours9.259259e-5 days 0.00222 hours 1.322751e-5 weeks 3.044e-6 months IAW required features CT4 DG 1A-A 1, 2, 3, 4, 5, 6, Irrad. Fuel Movement NA2 / 10 days Offsite circuit 1, 2, 3, 4, 5, 6, Irrad. Fuel Movement NA2 / 72 hours8.333333e-4 days 0.02 hours 1.190476e-4 weeks 2.7396e-5 months 7 days DG 1A-A & one offsite circuit 1, 2, 3, 4, 5, 6, Irrad. Fuel Movement NA2 / 12 hours1.388889e-4 days 0.00333 hours 1.984127e-5 weeks 4.566e-6 months 7 days5 Notes:

1. Assumes Unit 1 is defueled, Unit 2 in Mode 1, 2, 3, or 4.

2. With appropriate system lineup.

3. Provided in a separate license amendment request.

4. The Completion Time (CT) for returning to the SDBDs to an operable status would be limited to the shortest Completion Time for an associated required feature.

5. The proposed TS change requires entry into TS 3.8.1 Conditions B and D (new).

CNL-18-119 E1-16 of 19

Enclosure 1 Description and Assessment of Proposed Change Table 2 Affected Major Loads - De-energize 6.9 kV SDBD 1B-B and Associated 480 V SDBDs Unit 1 Systems Required Modes U1 / U2 TS CT1 Safety Injection pump 1B-B 1, 2, 3 NA / NA AFW pump 1B-B 1, 2, 3, 4 NA / NA RHR pump 1B-B 1, 2, 3, 4, 5, 6 NA / NA Charging pump 1B-B 1, 2, 3, 4 NA / NA Cont. Spray pump 1B-B 1, 2, 3, 4 NA / NA Air Return System fan 1B-B 1, 2, 3, 4 NA / NA Pressurizer Heater Groups 1B, 1C 1, 2, 3 NA / NA Shared Systems Required Modes U1 / U2 TS CT1 Proposed U2 TS CT ERCW pumps E-B, G-B 1, 2, 3, 4, 5 NA / 72 hours8.333333e-4 days 0.02 hours 1.190476e-4 weeks 2.7396e-5 months 7 days3 CCS pump 1B-B 1, 2, 3, 4, 5 NA / NA2 EGTS fan B-B 1, 2, 3, 4 NA / 7 days Control Room AHU B-B 1, 2, 3, 4, 5, 6, Irrad. Fuel Movement 30 days / 30 days CREVS fan B-B 1, 2, 3, 4, 5, 6, Irrad. Fuel Movement 7 days / 7 days CREVS radiation monitor 1, 2, 3, 4, 5, 6, Irrad. Fuel Movement 7 days / 7 days 125 V Vital Battery Charger II 1, 2, 3, 4, 5, 6, Irrad. Fuel Movement NA2 / 2 hours2.314815e-5 days 5.555556e-4 hours 3.306878e-6 weeks 7.61e-7 months 7 days3 120 V Vital Inverters: 1-II, 2-II 1, 2, 3, 4, 5, 6, Irrad. Fuel Movement NA2 / 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months NA AC electrical power distribution boards 1, 2, 3, 4, 5, 6, Irrad. Fuel Movement NA2 / 8 hours9.259259e-5 days 0.00222 hours 1.322751e-5 weeks 3.044e-6 months IAW required features CT4 DG 1B-B 1, 2, 3, 4, 5, 6, Irrad. Fuel Movement NA2 / 10 days Offsite circuit 1, 2, 3, 4, 5, 6, Irrad. Fuel Movement NA2 / 72 hours8.333333e-4 days 0.02 hours 1.190476e-4 weeks 2.7396e-5 months 7 days DG 1B-B & one offsite circuit 1, 2, 3, 4, 5, 6, Irrad. Fuel Movement NA2 / 12 hours1.388889e-4 days 0.00333 hours 1.984127e-5 weeks 4.566e-6 months 7 days5 Notes:

1. Assumes Unit 1 is defueled, Unit 2 in Mode 1, 2, 3, or 4.

2. With appropriate system lineup.

3. Proposed change provided in a separate license amendment request.

4. The Completion Time for returning to the SDBDs to an operable status would be limited to the shortest Completion Time for an associated required feature.

5. The proposed TS change requires entry into TS 3.8.1 Conditions B and D (new).

CNL-18-119 E1-17 of 19

Enclosure 1 Description and Assessment of Proposed Change Table 3 Affected Major Loads - De-energize 6.9 kV SDBD 2A-A and Associated 480 V SDBDs Unit 1 Systems Required Modes U2 / U1 TS CT1 Safety Injection pump 2A-A 1, 2, 3 NA / NA AFW pump 2A-A 1, 2, 3, 4 NA / NA RHR pump 2A-A 1, 2, 3, 4, 5, 6 NA / NA Charging pump 2A-A 1, 2, 3, 4 NA / NA Containment Spray pump 2A-A 1, 2, 3, 4 NA / NA Air Return System fan 2A-A 1, 2, 3, 4 NA / NA Pressurizer Heater Groups 2A, 2D 1, 2, 3 NA / NA Shared Systems Required Modes U2 / U1 TS CT1 Proposed U1 TS CT ERCW pumps B-A, D-A 1, 2, 3, 4, 5 NA / 72 hours8.333333e-4 days 0.02 hours 1.190476e-4 weeks 2.7396e-5 months 7 days3 CCS pump 2A-A 1, 2, 3, 4, 5 NA / NA2 ABGTS exhaust fan 1A-A 1, 2, 3, 4 NA / 7 days 125 V Vital Battery Charger III 1, 2, 3, 4, 5, 6, Irrad. Fuel Movement NA2 / 2 hours2.314815e-5 days 5.555556e-4 hours 3.306878e-6 weeks 7.61e-7 months 7 days3 120 V Vital Inverters: 1-III, 2-III 1, 2, 3, 4, 5, 6, Irrad. Fuel Movement NA2 / 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months NA AC electrical distribution boards 1, 2, 3, 4, 5, 6, Irrad. Fuel Movement NA2 / 8 hours9.259259e-5 days 0.00222 hours 1.322751e-5 weeks 3.044e-6 months IAW required features CT4 DG 2A-A 1, 2, 3, 4, 5, 6, Irrad. Fuel Movement NA2 / 10 days Offsite circuit 1, 2, 3, 4, 5, 6, Irrad. Fuel Movement NA2 / 72 hours8.333333e-4 days 0.02 hours 1.190476e-4 weeks 2.7396e-5 months 7 days DG 2A-A & one offsite circuit 1, 2, 3, 4, 5, 6, Irrad. Fuel Movement NA2 / 12 hours1.388889e-4 days 0.00333 hours 1.984127e-5 weeks 4.566e-6 months 7 days5 Auxiliary Air Compressor 1, 2, 3, 4 (with SGs relied on for heat removal) NA / 72 hours8.333333e-4 days 0.02 hours 1.190476e-4 weeks 2.7396e-5 months NA6 Notes:

1. Assumes Unit 2 is defueled, Unit 1 in Mode 1, 2, 3, or 4.

2. With appropriate system lineup that meets the associated LCO.

3. Proposed change provided in a separate license amendment request.

4. The Completion Time for returning to the SDBDs to an operable status would be limited to the shortest Completion Time for an associated required feature.

5. The proposed TS change requires entry into TS 3.8.1 Conditions B and D (new).

6. Design change DCN 60937 is in progress to install another auxiliary air compressor to preclude the loss of auxiliary air with SDBD 2A-A de-energized.

CNL-18-119 E1-18 of 19

Enclosure 1 Description and Assessment of Proposed Change Table 4 Affected Major Loads - De-energize 6.9 kV SDBD 2B-B and Associated 480 V SDBDs Unit 1 Systems Required Modes U2 / U1 TS CT1 Safety Injection pump 2B-B 1, 2, 3 NA / NA AFW pump 2B-B 1, 2, 3, 4 NA / NA RHR pump 2B-B 1, 2, 3, 4, 5, 6 NA / NA Charging pump 2B-B 1, 2, 3, 4 NA / NA Cont. Spray pump 2B-B 1, 2, 3, 4 NA / NA Air Return System fan 2B-B 1, 2, 3, 4 NA / NA Pressurizer Heater Groups 2B, 2C 1, 2, 3 NA / NA Shared Systems Required Modes U2 / U1 TS CT1 Proposed U1 TS CT ERCW pumps F-B, H-B 1, 2, 3, 4, 5 NA / 72 hours8.333333e-4 days 0.02 hours 1.190476e-4 weeks 2.7396e-5 months 7 days3 CCS pump 2B-B 1, 2, 3, 4, 5 NA / NA2 CCS pump C-S 1, 2, 3, 4, 5 NA / NA2 ABGTS exhaust fan 2B-B 1, 2, 3, 4 NA / 7 days 125 V Vital Battery Charger IV 1, 2, 3, 4, 5, 6, Irrad. Fuel Movement NA2 / 2 hours2.314815e-5 days 5.555556e-4 hours 3.306878e-6 weeks 7.61e-7 months 7 days3 120 V Vital Inverters: 1-IV, 2-IV 1, 2, 3, 4, 5, 6, Irrad. Fuel Movement NA2 / 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months NA AC electrical distribution boards 1, 2, 3, 4, 5, 6, Irrad. Fuel Movement NA2 / 8 hours9.259259e-5 days 0.00222 hours 1.322751e-5 weeks 3.044e-6 months IAW required features CT4 DG 2B-B 1, 2, 3, 4, 5, 6, Irrad. Fuel Movement NA2 / 10 days Offsite circuit 1, 2, 3, 4, 5, 6, Irrad. Fuel Movement NA2 / 72 hours8.333333e-4 days 0.02 hours 1.190476e-4 weeks 2.7396e-5 months 7 days DG 2B-B & one offsite circuit 1, 2, 3, 4, 5, 6, Irrad. Fuel Movement NA2 / 12 hours1.388889e-4 days 0.00333 hours 1.984127e-5 weeks 4.566e-6 months 7 days5 Auxiliary Air Compressor 1, 2, 3, 4 (with SGs relied on for heat removal) NA / 72 hours8.333333e-4 days 0.02 hours 1.190476e-4 weeks 2.7396e-5 months NA6 Notes:

1. Assumes Unit 2 is defueled, Unit 1 in Mode 1, 2, 3, or 4.

2. With appropriate system lineup.

3. Proposed change provided in a separate license amendment request.

4. The Completion Time for returning to the SDBDs to an operable status would be limited to the shortest Completion Time for an associated required feature.

5. The proposed TS change requires entry into TS 3.8.1 Conditions B and D (new).

6. Design change DCN 60937 is in progress to install another auxiliary air compressor to preclude the loss of auxiliary air with SDBD 2B-B de-energized.

CNL-18-119 E1-19 of 19

Enclosure 2 Simplified Drawing of WBN AC Electrical Distribution System CNL-18-119 E2-1

6.9 kV Shutdown Bd 1B-B Figure 1 - Simplified Diagram WBN Units 1 and 2 6.9 kV Shutdown Boards 161 KV BUS 151 KV eus I CXM40N STA I NC) NC) : SWIT~EAft D L--- ------- ___ J

- - , 6900V JMW 6.9 kV Shutdown Bd 2A-A 1

) 81 1 f"LEX DIESCL ctl'tltR.-.TOA ltl

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Figure 2 - WBN Units 1 and 2 Safety Related Load Distribution With Both Units in Operation Enclosure 3 Markups of Technical Specification and Bases Changes CNL-18-119 E3-1

WBN Unit 1 Markups of Technical Specification and Bases Changes CNL-18-119 E3-2

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.

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

ACTIONS

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

1. LCO 3.0.4.b is not applicable to DGs.

2. Enter applicable Conditions and Required Actions of LCO 3.8.9, Distribution Systems - Operating, when any Condition(s) is entered with no AC power source to any shutdown board resulting in a de-energized shutdown board.

CONDITION REQUIRED ACTION COMPLETION TIME A. One required offsite circuit A.1 Perform SR 3.8.1.1 for 1 hour1.157407e-5 days 2.777778e-4 hours 1.653439e-6 weeks 3.805e-7 months inoperable for reasons required OPERABLE offsite other than Condition D. circuit. AND Once per 8 hours9.259259e-5 days 0.00222 hours 1.322751e-5 weeks 3.044e-6 months thereafter AND 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)

AND (continued)

Watts Bar-Unit 1 3.8-1 Amendment 55, 84, 103

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 13 days from discovery of failure to meet LCO B. One DG inoperable. 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 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 Evaluate availability of 6.9 kV 2 hours2.314815e-5 days 5.555556e-4 hours 3.306878e-6 weeks 7.61e-7 months FLEX DG.

AND Once per 12 hours1.388889e-4 days 0.00333 hours 1.984127e-5 weeks 4.566e-6 months thereafter AND B.3 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 (continued)

Watts Bar-Unit 1 3.8-2 Amendment 39, 84, 103, 110

AC Sources-Operating 3.8.1 ACTIONS (continued)

CONDITION REQUIRED ACTION COMPLETION TIME B. (continued) B.4.1 Determine OPERABLE DGs 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months are not inoperable due to common cause failure.

OR B.4.2 Perform SR 3.8.1.2 for 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months OPERABLE DGs.

AND B.5 Restore DG to OPERABLE 72 hours8.333333e-4 days 0.02 hours 1.190476e-4 weeks 2.7396e-5 months from status. discovery of unavailability of 6.9 kV FLEX DG AND 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months from discovery of Condition B entry 48 hours5.555556e-4 days 0.0133 hours 7.936508e-5 weeks 1.8264e-5 months concurrent with unavailability of 6.9 kV FLEX DG AND 10 days AND 13 days from discovery of failure to meet LCO (continued)

Watts Bar-Unit 1 3.8-2a Amendment 39, 84, 103, 110

AC Sources-Operating 3.8.1 ACTIONS (continued)

CONDITION REQUIRED ACTION COMPLETION TIME C. Two DGs in Train A 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 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 DGs in Train B thereafter 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 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months are not inoperable due to common cause failure.

OR C.3.2 Perform SR 3.8.1.2 for 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months OPERABLE DGs.

AND C.4 Restore DGs to OPERABLE 72 hours8.333333e-4 days 0.02 hours 1.190476e-4 weeks 2.7396e-5 months status.

AND 6 days from discovery of failure to meet LCO (continued)

Watts Bar-Unit 1 3.8-2b Amendment 30, 39, 84, 103, 110

AC Sources-Operating 3.8.1 ACTIONS (continued)

CONDITION REQUIRED ACTION COMPLETION TIME

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

1. Only applicable during planned maintenance of a Unit 2 AC electrical power distribution subsystem.

2. Only applicable when Unit 2 is defueled.

D. One required offsite circuit D.1 Perform SR 3.8.1.1 for 1 hour1.157407e-5 days 2.777778e-4 hours 1.653439e-6 weeks 3.805e-7 months inoperable solely due to an required OPERABLE offsite offsite power source to circuit. AND 6.9 kV Shutdown Board 2A-A or 2B-B inoperable. Once per 8 hours9.259259e-5 days 0.00222 hours 1.322751e-5 weeks 3.044e-6 months thereafter AND D.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 required feature(s) is 6.9 kV Shutdown inoperable. Board 2A-A or 2B-B concurrent with inoperability of redundant required feature(s)

AND D.3 Restore required offsite circuit 7 days to OPERABLE status.

(continued)

Watts Bar-Unit 1 3.8-3 Amendment 39, 84, 103, 110

AC Sources-Operating 3.8.1 ACTIONS (continued)

CONDITION REQUIRED ACTION COMPLETION TIME DE. Two required offsite circuits DE.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 E inoperable. concurrent with inoperability of redundant required features.

AND DE.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.

EF. One required offsite circuit ----------------------NOTE---------------------

inoperable for reasons Enter applicable Conditions and other than Condition D. Required Actions of LCO 3.8.9, Distribution Systems - Operating, AND when Condition E is entered with no AC power source to any train.

One or more DG(s) in ----------------------------------------------------

Train A inoperable.

EF.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 DG(s) in OR Train B inoperable.

EF.2 Restore DG(s) to OPERABLE 12 hours1.388889e-4 days 0.00333 hours 1.984127e-5 weeks 4.566e-6 months status.

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

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

(continued)

Watts Bar-Unit 1 3.8-4 Amendment 39, 84, 103, 110

AC Sources-Operating 3.8.1 ACTIONS (continued)

CONDITION REQUIRED ACTION COMPLETION TIME GH. Required Action and GH.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, F, or F G not met.

GH.2 Be in MODE 5. 36 hours4.166667e-4 days 0.01 hours 5.952381e-5 weeks 1.3698e-5 months HI. Two required offsite circuits HI.1 Enter LCO 3.0.3. Immediately inoperable.

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

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

IJ. One required offsite circuit IJ.1 Enter LCO 3.0.3. Immediately inoperable.

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

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

Watts Bar-Unit 1 3.8-5 Amendment 39, 84, 103, 110

Inverters-Operating 3.8.7 SURVEILLANCE REQUIREMENTS SURVEILLANCE FREQUENCY SR 3.8.7.1 Verify correct inverter voltage, frequency, and 7 days alignment to required AC vital bus and from associated vital battery board and 480 V shutdown board.

Watts Bar-Unit 1 3.8-38

Inverters-Shutdown 3.8.8 SURVEILLANCE REQUIREMENTS SURVEILLANCE FREQUENCY SR 3.8.8.1 Verify correct inverter voltage, frequency, and 7 days alignments to required AC vital bus and from associated vital battery board and 480 V shutdown board.

Watts Bar-Unit 1 3.8-40

Distribution Systems-Operating 3.8.9 3.8 ELECTRICAL POWER SYSTEMS 3.8.9 Distribution Systems - Operating LCO 3.8.9 Train A and Train B AC, vital DC, and AC vital bus electrical power distribution subsystems shall be OPERABLE.

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

ACTIONS CONDITION REQUIRED ACTION COMPLETION TIME A. One or more AC electrical A.1 Restore Unit 1 AC electrical 8 hours9.259259e-5 days 0.00222 hours 1.322751e-5 weeks 3.044e-6 months power distribution power distribution subsystem subsystems inoperable to OPERABLE status. AND due to one or more Unit 1 AC shutdown boards 16 hours1.851852e-4 days 0.00444 hours 2.645503e-5 weeks 6.088e-6 months from inoperable. discovery of failure to meet LCO B. One or more Unit 1 AC B.1 Restore AC vital bus(es) to 2 hours2.314815e-5 days 5.555556e-4 hours 3.306878e-6 weeks 7.61e-7 months vital buses in one channel OPERABLE status.

inoperable. AND 16 hours1.851852e-4 days 0.00444 hours 2.645503e-5 weeks 6.088e-6 months from discovery of failure to meet LCO

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

1. Only applicable during planned maintenance of a Unit 2 AC vital bus.

2. Only applicable when Unit 2 is in MODE 5, MODE 6, or defueled.

C. One Unit 2 AC vital bus in C.1 Restore the Unit 2 AC vital bus 8 hours9.259259e-5 days 0.00222 hours 1.322751e-5 weeks 3.044e-6 months one channel inoperable. to OPERABLE status.

(continued)

Watts Bar-Unit 1 3.8-41

Distribution Systems-Operating 3.8.9 ACTIONS (continued)

CONDITION REQUIRED ACTION COMPLETION TIME D. One or more Unit 2 AC vital D.1 Restore the Unit 2 AC vital 2 hours2.314815e-5 days 5.555556e-4 hours 3.306878e-6 weeks 7.61e-7 months buses in one channel bus(es) to OPERABLE inoperable for reasons other status. AND than Condition C.

16 hours1.851852e-4 days 0.00444 hours 2.645503e-5 weeks 6.088e-6 months from discovery of failure to meet LCO E. One or more vital DC E.1 Restore DC electrical power 2 hours2.314815e-5 days 5.555556e-4 hours 3.306878e-6 weeks 7.61e-7 months electrical power distribution distribution bus to buses inoperable. OPERABLE status. AND 16 hours1.851852e-4 days 0.00444 hours 2.645503e-5 weeks 6.088e-6 months from discovery of failure to meet LCO

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

1. Only applicable during planned maintenance of a Unit 2 AC electrical power distribution subsystem.

2. Only applicable when Unit 2 is defueled.

F. One or more AC electrical F.1 Declare associated required Immediately power distribution feature(s) inoperable.

subsystems inoperable due to one or more Unit 2 AC shutdown boards inoperable.

G. One or more AC electrical G.1 Restore Unit 2 AC electrical 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months power distribution power distribution subsystems inoperable due subsystem(s) to OPERABLE to one or more Unit 2 AC status.

shutdown boards inoperable for reasons other than Condition F.

(continued)

Watts Bar-Unit 1 3.8-42

Distribution Systems-Operating 3.8.9 ACTIONS (continued)

CONDITION REQUIRED ACTION COMPLETION TIME FH. Required Action and FH.1 Be in MODE 3. 6 hours6.944444e-5 days 0.00167 hours 9.920635e-6 weeks 2.283e-6 months associated Completion Time not met. AND FH.2 Be in MODE 5. 36 hours4.166667e-4 days 0.01 hours 5.952381e-5 weeks 1.3698e-5 months GI. Two trains with one or GI.1 Enter LCO 3.0.3. Immediately more inoperable distribution subsystems that result in a loss of safety function.

SURVEILLANCE REQUIREMENTS SURVEILLANCE FREQUENCY SR 3.8.9.1 Verify correct breaker alignments and voltage to 7 days required AC, vital DC, and AC vital bus electrical power distribution subsystems.

Watts Bar-Unit 1 3.8-43

AC Sources - Operating B 3.8.1 BASES (continued)

APPLICABILITY The AC sources are required to be OPERABLE in MODES 1, 2, 3, and 4 to ensure that:

a. Acceptable fuel design limits and reactor coolant pressure boundary limits are not exceeded as a result of AOOs or abnormal transients; and

b. Adequate core cooling is provided and containment OPERABILITY and other vital functions are maintained in the event of a postulated DBA.

The AC power requirements for MODES 5 and 6 are covered in LCO 3.8.2, AC Sources - Shutdown.

ACTIONS A Note The ACTIONS are modified by a Note that prohibits the application of LCO 3.0.4.b to an inoperable DG. There is an increased risk associated with entering a MODE or other specified condition in the Applicability with an inoperable DG and the provisions of LCO 3.0.4.b, which allow entry into a MODE or other specified condition in the Applicability with the LCO not met after performance of a risk assessment addressing inoperable systems and components, should not be applied in this circumstance.

A second Note provides the appropriate restrictions for a de-energized shutdown board. Pursuant to LCO 3.0.6, the Distribution System ACTIONS would not be entered even if all AC sources to it were inoperable, resulting in de-energization.

Therefore, the ACTIONS are modified by a Note to indicate that when any Condition(s) is entered with no AC power source to any shutdown board resulting in a de-energized shutdown board, the Conditions and Required Actions for LCO 3.8.9, "Distribution Systems - Operating," must be immediately entered. This allows LCO 3.8.1 Conditions to provide requirements for the loss of any combination of AC Sources, without regard to whether a shutdown board is de-energized and LCO 3.8.9 to provide the appropriate restrictions for a de-energized shutdown board.

A.1 To ensure a highly reliable power source remains with one required offsite circuit inoperable for reasons other than Condition D, it is necessary to verify the OPERABILITY of the remaining required offsite circuit on a more frequent basis.

Since the Required Action only specifies perform, a failure of SR 3.8.1.1 acceptance criteria does not result in a Required Action not met. However, if a second required circuit fails SR 3.8.1.1, the second offsite circuit is inoperable, and Condition DE, for two required offsite circuits inoperable, is entered.

A.2 Required Action A.2, which only applies if the train cannot be powered from a required offsite source, is intended to provide assurance that an event coincident (continued)

Watts Bar-Unit 1 B 3.8-5 Revision 68, 116, 125 Amendment 55, 103

AC Sources - Operating B 3.8.1 BASES ACTIONS C.4 (continued)

The AND connector between the 72 hour8.333333e-4 days 0.02 hours 1.190476e-4 weeks 2.7396e-5 months and 6 day Completion Times means that both Completion Times apply simultaneously, and the more restrictive Completion Time must be met.

As in Required Action C.2, the Completion Time allows for an exception to the normal time zero for beginning the allowed outage time clock. This will result in establishing the time zero at the time that the LCO was initially not met, instead of at the time Condition C was entered.

D.1, D.2, and D.3 Condition D is modified by two notes that limit the conditions that allow entry into Condition D. The first note states that Condition D is only applicable during planned maintenance. This will allow the plant configuration to be aligned to minimize features being inoperable when the opposite unit shutdown board is made inoperable. The second note limits the applicability of Condition D to the time period when the opposite unit is defueled. This note limits the time period allowing Condition D to be entered, minimizing when the allowance can be utilized.

Condition D is entered for an offsite circuit inoperable solely due to an inoperable power source to 6.9 kV Shutdown Board 2A-A or 2B-B. Required Action D.1 verifies the OPERABILITY of the remaining offsite circuit within an hour of the inoperability and every 8 hours9.259259e-5 days 0.00222 hours 1.322751e-5 weeks 3.044e-6 months thereafter. Since the Required Action only specifies "perform," a failure of the SR 3.8.1.1 acceptance criteria does not result in a Required Action not met.

The Completion Time for Required Action D.2 is intended to allow the operator time to evaluate and repair any discovered inoperabilities. This Completion Time also allows for an exception to the normal "time zero" for beginning the allowed outage time "clock." In this Required Action, the Completion Time only begins on discovery that both:

a. 6.9 kV Shutdown Board 2A-A or 2B-B has no offsite power; and

b. A required feature on the other train is inoperable.

If at any time during the existence of Condition D a redundant required feature subsequently becomes inoperable, this Completion Time begins to be tracked.

A Completion Time of 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months is acceptable, because it minimizes risk while allowing time for restoration before subjecting the unit to transients associated with shutdown. The remaining OPERABLE offsite circuit and DGs are adequate to support these functions. The Completion Time takes into account the (continued)

Watts Bar-Unit 1 B 3.8-10a Revision 132 Amendment 110

AC Sources - Operating B 3.8.1 BASES ACTIONS D.1, D.2, and D.3 (continued) component OPERABILITY of the remaining redundant feature(s), a reasonable time for repairs, and the low probability of a DBA occurring during this period.

Operation may continue in Condition D for a period of 7 days. With one offsite circuit inoperable, the reliability of the functions is degraded. The potential for the loss of offsite power to the redundant feature(s) is increased, with the attendant potential for a challenge to their safety functions.

The required offsite circuit must be returned to OPERABLE status within 7 days.

The 7 days Completion Time takes into account the capacity and capability of the remaining AC sources providing electrical power to the required feature(s), a reasonable time for repairs and the low probability of a DBA occurring during this period of time.

ED.1 and ED.2.

Required Action ED.1, which applies when two required offsite circuits are inoperable, is intended to provide assurance that an event with a coincident single failure will not result in a complete loss of redundant required safety functions. The Completion Time for this failure of redundant required features is reduced to 12 hours1.388889e-4 days 0.00333 hours 1.984127e-5 weeks 4.566e-6 months from that allowed for one train without offsite power (Required Action A.2). The rationale for the reduction to 12 hours1.388889e-4 days 0.00333 hours 1.984127e-5 weeks 4.566e-6 months is that Regulatory Guide 1.93 (Ref. 6) allows a Completion Time of 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months for two required offsite circuits inoperable, based upon the assumption that two complete safety trains are OPERABLE. When a concurrent redundant required feature failure exists, this assumption is not the case, and a shorter Completion Time of 12 hours1.388889e-4 days 0.00333 hours 1.984127e-5 weeks 4.566e-6 months is appropriate. These features are powered from redundant AC safety trains. This includes motor driven auxiliary feedwater pumps. Single train features, such as the turbine driven auxiliary pump, are not included in the list.

The Completion Time for Required Action ED.1 is intended to allow the operator time to evaluate and repair any discovered inoperabilities. This Completion Time also allows for an exception to the normal time zero for beginning the allowed outage time clock. In this Required Action the Completion Time only begins on discovery that both:

a. All required offsite circuits are inoperable; and

b. A required feature is inoperable.

If at any time during the existence of Condition ED (two required offsite circuits inoperable) a required feature becomes inoperable, this Completion Time begins to be tracked.

(continued)

Watts Bar-Unit 1 B 3.8-11 Revision 50, 65, 125, 132 Amendment 39, 84, 110

AC Sources - Operating B 3.8.1 BASES ACTIONS ED.1 and ED.2 (continued)

According to Regulatory Guide 1.93 (Ref. 6), operation may continue in Condition ED for a period that should not exceed 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months . This level of degradation means that the offsite electrical power system does not have the capability to effect a safe shutdown and to mitigate the effects of an accident; however, the onsite AC sources have not been degraded. This level of degradation generally corresponds to a total loss of the immediately accessible offsite power sources.

Because of the normally high availability of the offsite sources, this level of degradation may appear to be more severe than other combinations of two AC sources inoperable (e.g., combinations that involve an offsite circuit and one DG inoperable, or one or more DGs in each train inoperable). However, two factors tend to decrease the severity of this level of degradation:

a. The configuration of the redundant AC electrical power system that remains available is not susceptible to a single bus or switching failure; and

b. The time required to detect and restore an unavailable required offsite power source is generally much less than that required to detect and restore an unavailable onsite AC source.

With both of the required offsite circuits inoperable, sufficient onsite AC sources are available to maintain the plant in a safe shutdown condition in the event of a DBA or transient. In fact, a simultaneous loss of offsite AC sources, a LOCA, and a worst case single failure were postulated as a part of the design basis in the safety analysis. Thus, the 24 hour2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months Completion Time provides a period of time to effect restoration of one of the offsite circuits commensurate with the importance of maintaining an AC electrical power system capable of meeting its design criteria.

According to Reference 6, with the available offsite AC sources, two less than required by the LCO, operation may continue for 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months . If two offsite sources are restored within 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months , unrestricted operation may continue. If only one offsite source is restored within 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months , power operation continues in accordance with Condition A or Condition D, as applicable.

(continued)

Watts Bar-Unit 1 B 3.8-12 Revision 50, 125, 132 Amendment 39, 84, 103, 110

AC Sources - Operating B 3.8.1 BASES ACTIONS FE.1 and FE.2 (continued)

Pursuant to LCO 3.0.6, the Distribution System ACTIONS would not be entered even if all AC sources to it were inoperable, resulting in de-energization.

Therefore, the Required Actions of Condition E are modified by a Note to indicate that when Condition E is entered with no AC source to any train, the Conditions and Required Actions for LCO 3.8.9, Distribution Systems - Operating, must be immediately entered. This allows Condition E to provide requirements for the loss of one offsite circuit and one or more DGs in a train, without regard to whether a train is de-energized. LCO 3.8.9 provides the appropriate restrictions for a de-energized train.

According to Regulatory Guide 1.93 (Ref. 6), operation may continue in Condition FE for a period that should not exceed 12 hours1.388889e-4 days 0.00333 hours 1.984127e-5 weeks 4.566e-6 months .

In Condition FE, individual redundancy is lost in both the offsite electrical power system and the onsite AC electrical power system. Since power system redundancy is provided by two diverse sources of power, however, the reliability of the power systems in this Condition may appear higher than that in Condition ED (loss of both required offsite circuits). This difference in reliability is offset by the susceptibility of this power system configuration to a single bus or switching failure. The 12 hour1.388889e-4 days 0.00333 hours 1.984127e-5 weeks 4.566e-6 months Completion Time takes into account the capacity and capability of the remaining AC sources, a reasonable time for repairs, and the low probability of a DBA occurring during this period.

GF.1 and GF.2 With one or more DGs in Train A inoperable simultaneous with one or more DGs in Train B inoperable, there are no remaining standby AC sources. Thus, with an assumed loss of offsite electrical power, insufficient standby AC sources are available to power the minimum required ESF functions. Since the offsite electrical power system is the only source of AC power for this level of degradation, the risk associated with continued operation for a very short time could be less than that associated with an immediate controlled shutdown (the immediate shutdown could cause grid instability, which could result in a total loss of AC power). Since any inadvertent generator trip could also result in a total loss of offsite AC power, however, the time allowed for continued operation is severely restricted. The intent here is to avoid the risk associated with an immediate controlled shutdown and to minimize the risk associated with this level of degradation.

According to Reference 6, with one or more DGs in Train A inoperable simultaneous with one or more DGs in Train B inoperable, operation may continue for a period that should not exceed 2 hours2.314815e-5 days 5.555556e-4 hours 3.306878e-6 weeks 7.61e-7 months .

(continued)

Watts Bar-Unit 1 B 3.8-13 Revision 50, 125, 132 Amendment 39, 84, 103, 110

AC Sources - Operating B 3.8.1 BASES ACTIONS HG.1 and HG.2 (continued)

If the inoperable AC electric power sources cannot be restored to OPERABLE status within the required Completion Time, the plant must be brought to a MODE in which the LCO does not apply. To achieve this status, the plant must be brought to at least MODE 3 within 6 hours6.944444e-5 days 0.00167 hours 9.920635e-6 weeks 2.283e-6 months and to MODE 5 within 36 hours4.166667e-4 days 0.01 hours 5.952381e-5 weeks 1.3698e-5 months .

The allowed Completion Times are reasonable, based on operating experience, to reach the required plant conditions from full power conditions in an orderly manner and without challenging plant systems.

IH.1 and JI.1 Condition IH and Condition JI corresponds to a level of degradation in which all redundancy in the AC electrical power supplies cannot be guaranteed. At this severely degraded level, any further losses in the AC electrical power system will cause a loss of function. Therefore, no additional time is justified for continued operation. The plant is required by LCO 3.0.3 to commence a controlled shutdown.

SURVEILLANCE The AC sources are designed to permit inspection and testing of all important REQUIREMENTS areas and features, especially those that have a standby function, in accordance with 10 CFR 50, Appendix A, GDC 18 (Ref. 8). Periodic component tests are supplemented by extensive functional tests during refueling outages (under simulated accident conditions). The SRs for demonstrating the OPERABILITY of the DGs are in accordance with the recommendations of Regulatory Guide 1.9 (Ref. 3) and Regulatory Guide 1.137 (Ref. 9), as addressed in the FSAR.

Where the SRs discussed herein specify voltage and frequency tolerances, the following is applicable. 6800 volts is the minimum steady state output voltage and the 10 second transient value. 6800 volts is 98.6% of the nominal bus voltage of 6900 V corrected for instrument error and is the upper limit of the minimum voltage required for the DG supply breaker to close on the 6.9 kV shutdown board. The specified maximum steady state output voltage of 7260 V is 110% of the nameplate rating of the 6600 V motors. The specified 3 second transient value of 6555 V is 95% of the nominal bus voltage of 6900 V. The specified maximum transient value of 8880 V is the maximum equipment withstand value provided by the DG manufacturer. The specified minimum and maximum frequencies of the DG are 58.8 Hz and 61.2 Hz, respectively. The steady state minimum and maximum frequency values are 59.8 Hz and 60.1 Hz.

These values ensure that the safety related plant equipment powered from the DGs is capable of performing its safety functions.

(continued)

Watts Bar-Unit 1 B 3.8-14 Revision 50, 125, 132 Amendment 39, 84, 110

Inverters - Operating B 3.8.7 BASES (continued)

SURVEILLANCE SR 3.8.7.1 REQUIREMENTS This Surveillance verifies that the inverters are functioning properly with all required circuit breakers closed including those from the associated vital battery boards and 480 V shutdown boards, and AC vital buses energized from the inverter. The verification of proper voltage and frequency output ensures that the required power is readily available for the instrumentation of the RPS and ESFAS connected to the AC vital buses. Upon placing a spare inverter in service, the spare inverter is considered inoperable until this surveillance is completed. The 7 day Frequency takes into account the redundant capability of the inverters and other indications available in the control room that alert the operator to inverter malfunctions.

REFERENCES 1. Watts Bar FSAR, Section 8.3.1, "AC Power System."

2. Watts Bar FSAR, Section 15, "Accident Analysis," and Section 6 "Engineered Safety Features."

Watts Bar-Unit 1 B 3.8-84 Revision 75

Inverters - Shutdown B 3.8.8 BASES ACTIONS A.1, A.2.1, A.2.2, A.2.3, and A.2.4 (continued) restrictions will be implemented in accordance with the affected required features LCOs' Required Actions. In many instances, this option may involve undesired administrative efforts. Therefore, the allowance for sufficiently conservative actions is made (i.e., to suspend CORE ALTERATIONS, movement of irradiated fuel assemblies, and operations involving positive reactivity additions). The Required Action to suspend positive reactivity additions does not preclude actions to maintain or increase reactor vessel inventory, provided the required SDM is maintained.

Suspension of these activities shall not preclude completion of actions to establish a safe conservative condition. These actions minimize the probability of the occurrence of postulated events. It is further required to immediately initiate action to restore the required inverters and to continue this action until restoration is accomplished in order to provide the necessary inverter power to the plant safety systems.

The Completion Time of immediately is consistent with the required times for actions requiring prompt attention. The restoration of the required inverters should be completed as quickly as possible in order to minimize the time the plant safety systems may be without power or powered from its associated regulated transformer bypass source.

SURVEILLANCE SR 3.8.8.1 REQUIREMENTS This Surveillance verifies that the required inverters are functioning properly with all required circuit breakers closed including those from the associated vital battery boards and 480 V shutdown boards and AC vital buses energized from the inverter. The verification of proper voltage and frequency output ensures that the required power is readily available for the instrumentation connected to the AC vital buses. The 7 day Frequency takes into account the redundant capability of the inverters and other indications available in the control room that alert the operator to inverter malfunctions. Upon placing a spare inverter in service, the spare inverter is considered inoperable until this surveillance is completed.

(continued)

Watts Bar-Unit 1 B 3.8-87 Revision 67, 75

Distribution Systems - Operating B 3.8.9 BASES (continued)

ACTIONS A.1 With one or more required AC shutdown boards, load centers, motor control centers, or distribution panels, except AC vital buses, in one train inoperable due to one or more inoperable Unit 1 AC shutdown boards, and a loss of function has not occurred, the remaining AC electrical power distribution subsystem in the other train is capable of supporting the minimum safety functions necessary to shut down the reactor and maintain it in a safe shutdown condition, assuming no single failure. The overall reliability is reduced, however, because a single failure in the remaining power distribution subsystems could result in the minimum required ESF functions not being supported. Therefore, the required Unit 1 AC shutdown boards, load centers, motor control centers, and distribution panels must be restored to OPERABLE status within 8 hours9.259259e-5 days 0.00222 hours 1.322751e-5 weeks 3.044e-6 months .

Condition A worst scenario is one train of Unit 1 boards without AC power (i.e.,

no offsite power to the train and the associated DG inoperable). In this Condition, the plant is more vulnerable to a complete loss of AC power. It is, therefore, imperative that the plant operator's attention be focused on minimizing the potential for loss of power to the remaining Unit 1 train by stabilizing the plant, and on restoring power to the affected train. The 8 hour9.259259e-5 days 0.00222 hours 1.322751e-5 weeks 3.044e-6 months time limit before requiring a plant shutdown in this Condition is acceptable because of:

a. The potential for decreased safety if the plant operator's attention is diverted from the evaluations and actions necessary to restore power to the affected train, to the actions associated with taking the plant to shutdown within this time limit; and

b. The potential for an event in conjunction with a single failure of a redundant component in the train with AC power.

The second Completion Time for Required Action A.1 establishes a limit on the maximum time allowed for any combination of required distribution subsystems to be inoperable during any single contiguous occurrence of failing to meet the LCO. If Condition A is entered while, for instance, a DC bus is inoperable and (continued)

Watts Bar-Unit 1 B 3.8-92

Distribution Systems - Operating B 3.8.9 BASES ACTIONS E.1 (continued)

This 2 hour2.314815e-5 days 5.555556e-4 hours 3.306878e-6 weeks 7.61e-7 months limit is more conservative than Completion Times allowed for the vast majority of components that would be without power. Taking exception to LCO 3.0.2 for components without adequate DC power, which would have Required Action Completion Times shorter than 2 hours2.314815e-5 days 5.555556e-4 hours 3.306878e-6 weeks 7.61e-7 months , is acceptable because of:

a. The potential for decreased safety by requiring a change in plant conditions (i.e., requiring a shutdown) while allowing stable operations to continue;

b. The potential for decreased safety by requiring entry into numerous applicable Conditions and Required Actions for components without DC power and not providing sufficient time for the operators to perform the necessary evaluations and actions for restoring power to the affected train; and

c. The potential for an event in conjunction with a single failure of a redundant component.

The 2 hour2.314815e-5 days 5.555556e-4 hours 3.306878e-6 weeks 7.61e-7 months Completion Time for DC buses is consistent with Regulatory Guide 1.93 (Ref. 2).

The second Completion Time for Required Action E.1 establishes a limit on the maximum time allowed for any combination of required distribution subsystems to be inoperable during any single contiguous occurrence of failing to meet the LCO. If Condition E is entered while, for instance, an AC bus is inoperable and subsequently returned OPERABLE, the LCO may already have been not met for up to 8 hours9.259259e-5 days 0.00222 hours 1.322751e-5 weeks 3.044e-6 months . This could lead to a total of 10 hours1.157407e-4 days 0.00278 hours 1.653439e-5 weeks 3.805e-6 months , since initial failure of the LCO, to restore the DC distribution system. At this time, an AC train could again become inoperable, and DC distribution restored OPERABLE. This could continue indefinitely.

This Completion Time allows for an exception to the normal "time zero" for beginning the allowed outage time "clock." This will result in establishing the "time zero" at the time the LCO was initially not met, instead of the time Condition E was entered. The 16 hour1.851852e-4 days 0.00444 hours 2.645503e-5 weeks 6.088e-6 months Completion Time is an acceptable limitation on this potential to fail to meet the LCO indefinitely.

F.1 With one or more AC electrical power distribution subsystems (except AC vital instrument boards) inoperable due to one or more inoperable Unit 2 AC shutdown boards and a loss of function has not occurred, the remaining AC electrical power distribution subsystems are capable of supporting the minimum (continued)

Watts Bar-Unit 1 B 3.8-97

Distribution Systems - Operating B 3.8.9 BASES ACTIONS F.1 (continued) safety functions necessary to shut down the reactor and maintain it in a safe shutdown condition, assuming no single failure. The overall reliability is reduced, however, because a single failure in the remaining power distribution subsystems could result in the minimum required ESF functions not being supported.

Therefore, the associated required feature(s) must be declared inoperable immediately and the corresponding Condition(s) entered. The Required Action(s) of these Condition(s) will determine the impact of the inoperable Unit 2 AC shutdown board(s).

Condition F is modified by two notes that limit the conditions and parameters that allow entry into Condition F. The first note states that Condition F is only applicable during planned maintenance. This will allow the plant configuration to be aligned to minimize features being inoperable when the opposite unit shutdown board is made inoperable. The second note limits the applicability of Condition F to the time period when the opposite unit is defueled. This note limits the time period allowing Condition F to be entered, minimizing when the allowance can be utilized. The allowance for Condition F is acceptable based on the following:

a. The opposite unit's AC shutdown boards are not as critical to the operating unit (fewer operating unit loads) as the operating unit's AC shutdown boards.

b. Performing maintenance on these components will increase the reliability of the Class 1E AC Electrical Power Distribution System.

c. The Required Actions associated with the features declared inoperable provide compensatory measures during the performance of the planned maintenance.

d. The limited opportunities that allow the planned maintenance to occur.

During the planned maintenance of the Unit 2 AC shutdown boards, if a condition is discovered on these boards requiring corrective maintenance, this maintenance may be performed under Condition F.

G.1 With one or more AC electrical power distribution subsystems (except AC vital instrument boards) inoperable due to one or more inoperable Unit 2 AC shutdown boards for reasons other than Condition F and a loss of function has not occurred, the remaining AC electrical power distribution subsystems are capable of supporting the minimum safety functions necessary to shut down the reactor and maintain it in a safe shutdown condition, assuming no single failure.

(continued)

Watts Bar-Unit 1 B 3.8-98

Distribution Systems - Operating B 3.8.9 BASES ACTIONS G.1 (continued)

The overall reliability is reduced, however, because a single failure in the remaining power distribution subsystems could result in the minimum required ESF functions not being supported. Therefore, the inoperable Unit 2 AC electrical power distribution subsystem(s) must be returned to OPERABLE status within 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months . The 24 hour2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months time limit before requiring a unit shutdown in this Condition is acceptable because the opposite unit's AC shutdown boards are not as critical to the operating unit (fewer operating unit loads) as the operating unit's AC shutdown boards.

FH.1 and FH.2 If the inoperable distribution subsystem cannot be restored to OPERABLE status within the required Completion Time, the plant must be brought to a MODE in which the LCO does not apply. To achieve this status, the plant must be brought to at least MODE 3 within 6 hours6.944444e-5 days 0.00167 hours 9.920635e-6 weeks 2.283e-6 months and to MODE 5 within 36 hours4.166667e-4 days 0.01 hours 5.952381e-5 weeks 1.3698e-5 months . The allowed Completion Times are reasonable, based on operating experience, to reach the required plant conditions from full power conditions in an orderly manner and without challenging plant systems.

GI.1 With two trains with one or more inoperable distribution subsystems that result in a loss of safety function, adequate core cooling, containment OPERABILITY, and other vital functions for DBA mitigation would be compromised, and immediate plant shutdown in accordance with LCO 3.0.3 is required.

(continued)

Watts Bar-Unit 1 B 3.8-99

WBN Unit 2 Markups of Technical Specification and Bases Changes CNL-18-119 E3-27

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.

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

ACTIONS

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

1. LCO 3.0.4.b is not applicable to DGs.

2. Enter applicable Conditions and Required Actions of LCO 3.8.9, Distribution Systems - Operating, when any Condition(s) is entered with no AC power source to any shutdown board resulting in a de-energized shutdown board.

CONDITION REQUIRED ACTION COMPLETION TIME A. One required offsite circuit A.1 Perform SR 3.8.1.1 for 1 hour1.157407e-5 days 2.777778e-4 hours 1.653439e-6 weeks 3.805e-7 months inoperable for reasons other required OPERABLE than Condition D. offsite circuit. AND Once per 8 hours9.259259e-5 days 0.00222 hours 1.322751e-5 weeks 3.044e-6 months thereafter AND (continued)

Watts Bar - Unit 2 3.8-1

AC Sources - Operating 3.8.1 ACTIONS CONDITION REQUIRED ACTION COMPLETION TIME A. (continued) A.2 Declare required 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months from feature(s) with no offsite discovery of no offsite power available power to one train inoperable when its concurrent with redundant required inoperability of feature(s) is inoperable. redundant required feature(s)

AND A.3 Restore required offsite 72 hours8.333333e-4 days 0.02 hours 1.190476e-4 weeks 2.7396e-5 months circuit to OPERABLE status. AND 13 days from discovery of failure to meet LCO B. One DG inoperable. 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 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 Evaluate availability of 6.9 2 hours2.314815e-5 days 5.555556e-4 hours 3.306878e-6 weeks 7.61e-7 months kV FLEX DG.

AND Once per 12 hours1.388889e-4 days 0.00333 hours 1.984127e-5 weeks 4.566e-6 months thereafter AND (continued)

Watts Bar - Unit 2 3.8-2 Amendment 5

AC Sources - Operating 3.8.1 ACTIONS CONDITION REQUIRED ACTION COMPLETION TIME B. (continued) B.3 Declare required 4 hours4.62963e-5 days 0.00111 hours 6.613757e-6 weeks 1.522e-6 months from feature(s) supported by discovery of Condition the inoperable DG B concurrent with inoperable when its inoperability of required redundant redundant required feature(s) is inoperable. features(s)

AND B.4.1 Determine OPERABLE 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months DGs are not inoperable due to common cause failure.

OR B.4.2 Perform SR 3.8.1.2 for 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months OPERABLE DGs.

AND B.5 Restore DG to 72 hours8.333333e-4 days 0.02 hours 1.190476e-4 weeks 2.7396e-5 months from OPERABLE status. discovery of unavailability of the 6.9 kV FLEX DG AND 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months from discovery of Condition B entry 48 hours5.555556e-4 days 0.0133 hours 7.936508e-5 weeks 1.8264e-5 months concurrent with unavailability of the 6.9 kV FLEX DG.

AND 10 days AND 13 days from discovery of failure to meet LCO (continued)

Watts Bar - Unit 2 3.8-2a Amendment 5

AC Sources - Operating 3.8.1 ACTIONS (continued)

CONDITION REQUIRED ACTION COMPLETION TIME C. Two DGs in Train A C.1 Perform SR 3.8.1.1 for 1 hour1.157407e-5 days 2.777778e-4 hours 1.653439e-6 weeks 3.805e-7 months inoperable. the required offsite circuits. AND OR Once per 8 hours9.259259e-5 days 0.00222 hours 1.322751e-5 weeks 3.044e-6 months Two DGs in Train B thereafter inoperable.

AND C.2 Declare required 4 hours4.62963e-5 days 0.00111 hours 6.613757e-6 weeks 1.522e-6 months from feature(s) supported by discovery of the inoperable DGs Condition C inoperable when its concurrent with required redundant inoperability of feature(s) is inoperable redundant required feature(s)

AND C.3.1 Determine OPERABLE 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months DGs are not inoperable due to common cause failure.

OR C.3.2 Perform SR 3.8.1.2 for 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months OPERABLE DGs.

AND C.4 Restore DGs to 72 hours8.333333e-4 days 0.02 hours 1.190476e-4 weeks 2.7396e-5 months OPERABLE status.

AND 6 days from discovery of failure to meet LCO (continued)

Watts Bar - Unit 2 3.8-2b Amendment 5

AC Sources - Operating 3.8.1 ACTIONS (continued)

CONDITION REQUIRED ACTION COMPLETION TIME

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

1. Only applicable during planned maintenance of a Unit 1 AC electrical power distribution subsystem.

2. Only applicable when Unit 1 is defueled.

D. One required offsite circuit D.1 Perform SR 3.8.1.1 for 1 hour1.157407e-5 days 2.777778e-4 hours 1.653439e-6 weeks 3.805e-7 months inoperable solely due to an required OPERABLE offsite power source to offsite circuit. AND 6.9 kV Shutdown Board 1A-A or 1B-B inoperable. Once per 8 hours9.259259e-5 days 0.00222 hours 1.322751e-5 weeks 3.044e-6 months thereafter AND D.2 Declare required 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months from feature(s) supported by discovery of no offsite the inoperable DG(s) power to 6.9 kV inoperable when its Shutdown Board required redundant 1A-A or 1B-B feature(s) is inoperable concurrent with inoperability of redundant required feature(s)

AND D.3 Restore required offsite 7 days circuit to OPERABLE status.

Watts Bar - Unit 2 3.8-3 Amendment 5

AC Sources - Operating 3.8.1 ACTIONS (continued)

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

EF. One required offsite circuit --------------------NOTE-------------------

inoperable for reasons other Enter applicable Conditions and than Condition D. Required Actions of LCO 3.8.9, "Distribution Systems - Operating,"

AND when Condition E is entered with no AC power source to any train.

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

OR EF.1 Restore required offsite 12 hours1.388889e-4 days 0.00333 hours 1.984127e-5 weeks 4.566e-6 months circuit to OPERABLE One or more DG(s) in Train status.

B inoperable.

OR EF.2 Restore DG(s) to 12 hours1.388889e-4 days 0.00333 hours 1.984127e-5 weeks 4.566e-6 months OPERABLE status.

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

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

(continued)

Watts Bar - Unit 2 3.8-4 Amendment 5

AC Sources - Operating 3.8.1 ACTIONS (continued)

CONDITION REQUIRED ACTION COMPLETION TIME GH. Required Action and GH.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, F, or F G not met.

GH.2 Be in MODE 5. 36 hours4.166667e-4 days 0.01 hours 5.952381e-5 weeks 1.3698e-5 months HI. Two required offsite circuits HI.1 Enter LCO 3.0.3. Immediately inoperable.

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

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

IJ. One required offsite circuit IJ.1 Enter LCO 3.0.3. Immediately inoperable.

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

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

Watts Bar - Unit 2 3.8-4 Amendment 5

Inverters - Operating 3.8.7 SURVEILLANCE REQUIREMENTS SURVEILLANCE FREQUENCY SR 3.8.7.1 Verify correct inverter voltage, frequency, and 7 days alignment to required AC vital bus and from associated vital battery board and 480 V shutdown board.

Watts Bar - Unit 2 3.8-34

Inverters - Shutdown 3.8.8 SURVEILLANCE REQUIREMENTS SURVEILLANCE FREQUENCY SR 3.8.8.1 Verify correct inverter voltage, frequency, and 7 days alignments to required AC vital bus and from associated vital battery board and 480 V shutdown board.

Watts Bar - Unit 2 3.8-36

Distribution Systems - Operating 3.8.9 3.8 ELECTRICAL POWER SYSTEMS 3.8.9 Distribution Systems - Operating LCO 3.8.9 Train A and Train B AC, vital DC, and AC vital bus electrical power distribution subsystems shall be OPERABLE.

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

ACTIONS CONDITION REQUIRED ACTION COMPLETION TIME A. One or more AC electrical A.1 Restore Unit 2 AC 8 hours9.259259e-5 days 0.00222 hours 1.322751e-5 weeks 3.044e-6 months power distribution electrical power subsystems inoperable due distribution subsystem to AND to one or more Unit 2 AC OPERABLE status.

shutdown boards 16 hours1.851852e-4 days 0.00444 hours 2.645503e-5 weeks 6.088e-6 months from inoperable. discovery of failure to meet LCO B. One or more AC vital buses B.1 Restore AC vital bus(es) 2 hours2.314815e-5 days 5.555556e-4 hours 3.306878e-6 weeks 7.61e-7 months in one channel inoperable. to OPERABLE status.

AND 16 hours1.851852e-4 days 0.00444 hours 2.645503e-5 weeks 6.088e-6 months from discovery of failure to meet LCO

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

1. Only applicable during planned maintenance of a Unit 1 AC vital bus.

2. Only applicable when Unit 1 is in MODE 5, MODE 6, or defueled.

C. One Unit 1 AC vital bus in one C.1 Restore the Unit 2 AC 8 hours9.259259e-5 days 0.00222 hours 1.322751e-5 weeks 3.044e-6 months channel inoperable. vital bus to OPERABLE status.

(continued)

Watts Bar - Unit 2 3.8-37

Distribution Systems - Operating 3.8.9 ACTIONS (continued)

CONDITION REQUIRED ACTION COMPLETION TIME D. One or more Unit 1 AC vital D.1 Restore the Unit 1 AC vital 2 hours2.314815e-5 days 5.555556e-4 hours 3.306878e-6 weeks 7.61e-7 months buses in one channel bus(es) to OPERABLE inoperable for reasons other status AND than Condition C.

16 hours1.851852e-4 days 0.00444 hours 2.645503e-5 weeks 6.088e-6 months from discovery of failure to meet LCO E. One or more vital DC E.1 Restore DC electrical 2 hours2.314815e-5 days 5.555556e-4 hours 3.306878e-6 weeks 7.61e-7 months electrical power distribution power distribution bus to buses inoperable. OPERABLE status. AND 16 hours1.851852e-4 days 0.00444 hours 2.645503e-5 weeks 6.088e-6 months from discovery of failure to meet LCO

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

1. Only applicable during planned maintenance of a Unit 1 AC electrical power distribution subsystem.

2. Only applicable when Unit 1 is defueled.

F. One or more AC electrical F.1 Declare associated required Immediately power distribution subsystems feature(s) inoperable.

inoperable due to one or more Unit 1 AC shutdown boards inoperable.

G. One or more AC electrical G.1 Restore Unit 1 AC electrical 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months power distribution subsystems power distribution inoperable due to one or more subsystem(s) to OPERABLE Unit 1 AC shutdown boards status.

inoperable for reasons other than Condition F.

(continued)

Watts Bar - Unit 2 3.8-38

Distribution Systems - Operating 3.8.9 ACTIONS (continued)

CONDITION REQUIRED ACTION COMPLETION TIME F.H.Required Action and FH.1 Be in MODE 3. 6 hours6.944444e-5 days 0.00167 hours 9.920635e-6 weeks 2.283e-6 months associated Completion Time not met. AND FH.2 Be in MODE 5. 36 hours4.166667e-4 days 0.01 hours 5.952381e-5 weeks 1.3698e-5 months G.I.Two trains with one or more GI.1 Enter LCO 3.0.3. Immediately inoperable distribution subsystems that result in a loss of safety function.

SURVEILLANCE REQUIREMENTS SURVEILLANCE FREQUENCY SR 3.8.9.1 Verify correct breaker alignments and voltage to 7 days required AC, vital DC, and AC vital bus electrical power distribution subsystems.

Watts Bar - Unit 2 3.8-39

AC Sources - Operating B 3.8.1 BASES (continued)

ACTIONS The ACTIONS are modified by a Note that A Note prohibits the application of LCO 3.0.4.b to an inoperable DG. There is an increased risk associated with entering a MODE or other specified condition in the Applicability with an inoperable DG and the provisions of LCO 3.0.4.b, which allow entry into a MODE or other specified condition in the Applicability with the LCO not met after performance of a risk assessment addressing inoperable systems and components, should not be applied in this circumstance.

A second Note provides the appropriate restrictions for a de-energized shutdown board. Pursuant to LCO 3.0.6, the Distribution System ACTIONS would not be entered even if all AC sources to it were inoperable, resulting in de-energization. Therefore, the ACTIONS are modified by a Note to indicate that when any Condition(s) is entered with no AC power source to any shutdown board resulting in a de-energized shutdown board, the Conditions and Required Actions for LCO 3.8.9, "Distribution Systems - Operating," must be immediately entered. This allows LCO 3.8.1 Conditions to provide requirements for the loss of any combination of AC Sources, without regard to whether a shutdown board is de-energized and LCO 3.8.9 to provide the appropriate restrictions for a de-energized shutdown board.

A.1 To ensure a highly reliable power source remains with one required offsite circuit inoperable for reasons other than Condition D, it is necessary to verify the OPERABILITY of the remaining required offsite circuit on a more frequent basis. Since the Required Action only specifies perform, a failure of SR 3.8.1.1 acceptance criteria does not result in a Required Action not met. However, if a second required circuit fails SR 3.8.1.1, the second offsite circuit is inoperable, and Condition CE, for two required offsite circuits inoperable, is entered.

A.2 Required Action A.2, which only applies if the train cannot be powered from a required offsite source, is intended to provide assurance that an event coincident with a single failure of the associated DG will not result in a complete loss of safety function of critical redundant required features. These features are powered from the redundant AC electrical power trains. This includes motor driven auxiliary feedwater pump.

Single train systems, such as the turbine driven auxiliary feedwater pump, may not be included.

The Completion Time for Required Action A.2 is intended to allow the operator time to evaluate and repair any discovered inoperabilities. This Completion Time also allows for an exception to the normal time zero for beginning the allowed outage time clock. In this Required Action, the Completion Time only begins on discovery that both:

(continued)

Watts Bar - Unit 2 B 3.8-8

AC Sources - Operating B 3.8.1 BASES ACTIONS D.1, D.2, and D.3 (continued)

Condition D is modified by two notes that limit the conditions that allow entry into Condition D. The first note states that Condition D is only applicable during planned maintenance. This will allow the plant configuration to be aligned to minimize features being inoperable when the opposite unit shutdown board is made inoperable. The second note limits the applicability of Condition D to the time period when the opposite unit is defueled. This note limits the time period allowing Condition D to be entered, minimizing when the allowance can be utilized.

Condition D is entered for an offsite circuit inoperable solely due to an inoperable power source to 6.9 kV Shutdown Board 1A-A or 1B-B.

Required Action D.1 verifies the OPERABILITY of the remaining offsite circuit within an hour of the inoperability and every 8 hours9.259259e-5 days 0.00222 hours 1.322751e-5 weeks 3.044e-6 months thereafter.

Since the Required Action only specifies "perform," a failure of the SR 3.8.1.1 acceptance criteria does not result in a Required Action not met.

The Completion Time for Required Action D.2 is intended to allow the operator time to evaluate and repair any discovered inoperabilities. This Completion Time also allows for an exception to the normal "time zero" for beginning the allowed outage time "clock." In this Required Action, the Completion Time only begins on discovery that both:

a. 6.9 kV Shutdown Board 1A-A or 1B-B has no offsite power; and

b. A required feature on the other train is inoperable.

If at any time during the existence of Condition D a redundant required feature subsequently becomes inoperable, this Completion Time begins to be tracked.

A Completion Time of 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months is acceptable, because it minimizes risk while allowing time for restoration before subjecting the unit to transients associated with shutdown. The remaining OPERABLE offsite circuit and DGs are adequate to support these functions. The Completion Time takes into account the component OPERABILITY of the remaining redundant feature(s), a reasonable time for repairs, and the low probability of a DBA occurring during this period.

Operation may continue in Condition D for a period of 7 days. With one offsite circuit inoperable, the reliability of the functions is degraded. The potential for the loss of offsite power to the redundant feature(s) is increased, with the attendant potential for a challenge to their safety functions.

(continued)

Watts Bar - Unit 2 B 3.8-12b Revision 5 Amendment 5

AC Sources - Operating B 3.8.1 BASES ACTIONS D.1, D.2, and D.3 (continued)

The required offsite circuit must be returned to OPERABLE status within 7 days. The 7 days Completion Time takes into account the capacity and capability of the remaining AC sources providing electrical power to the required feature(s), a reasonable time for repairs and the low probability of a DBA occurring during this period of time.

DE.1 and DE.2 Required Action DE.1, which applies when two required offsite circuits are inoperable, is intended to provide assurance that an event with a coincident single failure will not result in a complete loss of redundant required safety functions. The Completion Time for this failure of redundant required features is reduced to 12 hours1.388889e-4 days 0.00333 hours 1.984127e-5 weeks 4.566e-6 months from that allowed for one train without offsite power (Required Action A.2). The rationale for the reduction to 12 hours1.388889e-4 days 0.00333 hours 1.984127e-5 weeks 4.566e-6 months is that Regulatory Guide 1.93 (Ref. 6) allows a Completion Time of 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months for two required offsite circuits inoperable, based upon the assumption that two complete safety trains are OPERABLE. When a concurrent redundant required feature failure exists, this assumption is not the case, and a shorter Completion Time of 12 hours1.388889e-4 days 0.00333 hours 1.984127e-5 weeks 4.566e-6 months is appropriate. These features are powered from redundant AC safety trains. This includes motor driven auxiliary feedwater pumps.

Single train features, such as the turbine driven auxiliary pump, are not included in the list.

The Completion Time for Required Action DE.1 is intended to allow the operator time to evaluate and repair any discovered inoperabilities. This Completion Time also allows for an exception to the normal "time zero" for beginning the allowed outage time "clock." In this Required Action the Completion Time only begins on discovery that both:

a. All required offsite circuits are inoperable; and

b. A required feature is inoperable.

If at any time during the existence of Condition D E (two required offsite circuits inoperable) a required feature becomes inoperable, this Completion Time begins to be tracked.

According to Regulatory Guide 1.93 (Ref. 6), operation may continue in Condition D E for a period that should not exceed 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months . This level of degradation means that the offsite electrical power system does not have the capability to effect a safe shutdown and to mitigate the effects of an accident; however, the onsite AC sources have not been degraded. This level of degradation generally corresponds to a total loss of the immediately accessible offsite power sources.

(continued)

Watts Bar - Unit 2 B 3.8-13 Revision 5 Amendment 5

AC Sources - Operating B 3.8.1 BASES ACTIONS DE.1 and DE.2 (continued)

Because of the normally high availability of the offsite sources, this level of degradation may appear to be more severe than other combinations of two AC sources inoperable (e.g., combinations that involve an offsite circuit and one DG inoperable, or one or more DGs in each train inoperable). However, two factors tend to decrease the severity of this level of degradation:

a. The configuration of the redundant AC electrical power system that remains available is not susceptible to a single bus or switching failure; and

b. The time required to detect and restore an unavailable required offsite power source is generally much less than that required to detect and restore an unavailable onsite AC source.

With both of the required offsite circuits inoperable, sufficient onsite AC sources are available to maintain the plant in a safe shutdown condition in the event of a DBA or transient. In fact, a simultaneous loss of offsite AC sources, a LOCA, and a worst case single failure were postulated as a part of the design basis in the safety analysis. Thus, the 24 hour2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months Completion Time provides a period of time to effect restoration of one of the offsite circuits commensurate with the importance of maintaining an AC electrical power system capable of meeting its design criteria.

According to Reference 6, with the available offsite AC sources, two less than required by the LCO, operation may continue for 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months . If two offsite sources are restored within 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months , unrestricted operation may continue. If only one offsite source is restored within 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months , power operation continues in accordance with Condition A or Condition D, as applicable.

EF.1 and EF.2 Pursuant to LCO 3.0.6, the Distribution System ACTIONS would not be entered even if all AC sources to it were inoperable, resulting in de-energization. Therefore, the Required Actions of Condition E are modified by a Note to indicate that when Condition E is entered with no AC source to any train, the Conditions and Required Actions for LCO 3.8.9, Distribution Systems - Operating, must be immediately entered. This allows Condition E to provide requirements for the loss of one offsite circuit and one or more DGs in a train, without regard to whether a train is de-energized. LCO 3.8.9 provides the appropriate restrictions for a de-energized train.

According to Regulatory Guide 1.93 (Ref. 6), operation may continue in Condition E F for a period that should not exceed 12 hours1.388889e-4 days 0.00333 hours 1.984127e-5 weeks 4.566e-6 months .

(continued)

Watts Bar - Unit 2 B 3.8-14 Revision 5 Amendment 5

AC Sources - Operating B 3.8.1 BASES ACTIONS EF.1 and EF.2 (continued)

In Condition EF, individual redundancy is lost in both the offsite electrical power system and the onsite AC electrical power system. Since power system redundancy is provided by two diverse sources of power, however, the reliability of the power systems in this Condition may appear higher than that in Condition D E (loss of both required offsite circuits).

This difference in reliability is offset by the susceptibility of this power system configuration to a single bus or switching failure. The 12 hour1.388889e-4 days 0.00333 hours 1.984127e-5 weeks 4.566e-6 months Completion Time takes into account the capacity and capability of the remaining AC sources, a reasonable time for repairs, and the low probability of a DBA occurring during this period.

FG.1 and FG.2 With one or more DG(s) in Train A inoperable simultaneous with one or more DG(s) in Train B inoperable, there are no remaining standby AC sources. Thus, with an assumed loss of offsite electrical power, insufficient standby AC sources are available to power the minimum required ESF functions. Since the offsite electrical power system is the only source of AC power for this level of degradation, the risk associated with continued operation for a very short time could be less than that associated with an immediate controlled shutdown (the immediate shutdown could cause grid instability, which could result in a total loss of AC power). Since any inadvertent generator trip could also result in a total loss of offsite AC power, however, the time allowed for continued operation is severely restricted. The intent here is to avoid the risk associated with an immediate controlled shutdown and to minimize the risk associated with this level of degradation.

According to Reference 6, with one or more DG(s) in Train A inoperable simultaneous with one or more DG(s) in Train B inoperable, operation may continue for a period that should not exceed 2 hours2.314815e-5 days 5.555556e-4 hours 3.306878e-6 weeks 7.61e-7 months .

GH.1 and GH.2 If the inoperable AC electric power sources cannot be restored to OPERABLE status within the required Completion Time, the plant must be brought to a MODE in which the LCO does not apply. To achieve this status, the plant must be brought to at least MODE 3 within 6 hours6.944444e-5 days 0.00167 hours 9.920635e-6 weeks 2.283e-6 months and to MODE 5 within 36 hours4.166667e-4 days 0.01 hours 5.952381e-5 weeks 1.3698e-5 months . The allowed Completion Times are reasonable, based on operating experience, to reach the required plant conditions from full power conditions in an orderly manner and without challenging plant systems.

(continued)

Watts Bar - Unit 2 B 3.8-15 Revision 5 Amendment 5

AC Sources - Operating B 3.8.1 BASES ACTIONS HI.1 and IJ.1 (continued)

Condition H I and Condition I J correspond to a level of degradation in which all redundancy in the AC electrical power supplies cannot be guaranteed. At this severely degraded level, any further losses in the AC electrical power system will cause a loss of function. Therefore, no additional time is justified for continued operation. The plant is required by LCO 3.0.3 to commence a controlled shutdown.

SURVEILLANCE The AC sources are designed to permit inspection and testing of all REQUIREMENTS important areas and features, especially those that have a standby function, in accordance with 10 CFR 50, Appendix A, GDC 18 (Ref. 8).

Periodic component tests are supplemented by extensive functional tests during refueling outages (under simulated accident conditions). The SRs for demonstrating the OPERABILITY of the DGs are in accordance with the recommendations of Regulatory Guide 1.9 (Ref. 3) and Regulatory Guide 1.137 (Ref. 9), as addressed in the FSAR.

Where the SRs discussed herein specify voltage and frequency tolerances, the following is applicable. 6800 volts is the minimum steady state output voltage and the 10 seconds transient value. 6800 volts is 98.6% of the nominal bus voltage of 6900 V corrected for instrument error and is the upper limit of the minimum voltage required for the DG supply breaker to close on the 6.9 kV shutdown board. The specified maximum steady state output voltage of 7260 V is 110% of the nameplate rating of the 6600 V motors. The specified 3 second transient value of 6555 V is 95% of the nominal bus voltage of 6900 V. The specified maximum transient value of 8880 V is the maximum equipment withstand value provided by the DG manufacturer. The specified minimum and maximum transient frequencies of the DG are 58.8 Hz and 61.2 Hz, respectively.

The steady state minimum and maximum frequency values are 59.8 Hz and 60.1 Hz. These values ensure that the safety related plant equipment powered from the DGs is capable of performing its safety functions.

SR 3.8.1.1 This SR ensures proper circuit continuity for the offsite AC electrical power supply to the onsite distribution network and availability of offsite AC electrical power. The breaker alignment verifies that each breaker is in its correct position to ensure that distribution buses and loads are connected to their preferred power source, and that appropriate independence of offsite circuits is maintained. The 7 day Frequency is adequate since breaker position is not likely to change without the operator being aware of it and because its status is displayed in the control room.

(continued)

Watts Bar - Unit 2 B 3.8-16 Revision 5 Amendment 5

Inverters - Operating B 3.8.7 BASES (continued)

SURVEILLANCE SR 3.8.7.1 REQUIREMENTS This Surveillance verifies that the inverters are functioning properly with all required circuit breakers closed including those from the associated vital battery boards and 480 V shutdown boards, and AC vital buses energized from the inverter. The verification of proper voltage and frequency output ensures that the required power is readily available for the instrumentation of the RPS and ESFAS connected to the AC vital buses. Upon placing a spare inverter in service, the spare inverter is considered inoperable until this surveillance is completed. The 7 day Frequency takes into account the redundant capability of the inverters and other indications available in the control room that alert the operator to inverter malfunctions.

REFERENCES 1. Watts Bar FSAR, Section 8.3.1, AC Power System.

2. Watts Bar FSAR, Section 15, Accident Analysis, and Section 6, Engineered Safety Features.

Watts Bar - Unit 2 B 3.8-81

Inverters - Shutdown B 3.8.8 BASES (continued)

ACTIONS A.1, A.2.1, A.2.2, A.2.3, and A.2.4 If two trains are required by LCO 3.8.10, the remaining OPERABLE Inverters may be capable of supporting sufficient required features to allow continuation of CORE ALTERATIONS, fuel movement, and operations with a potential for positive reactivity additions. By the allowance of the option to declare required features inoperable with the associated inverter(s) inoperable, appropriate restrictions will be implemented in accordance with the affected required features LCOs' Required Actions. In many instances, this option may involve undesired administrative efforts. Therefore, the allowance for sufficiently conservative actions is made (i.e., to suspend CORE ALTERATIONS, movement of irradiated fuel assemblies, and operations involving positive reactivity additions). The Required Action to suspend positive reactivity additions does not preclude actions to maintain or increase reactor vessel inventory, provided the required SDM is maintained.

Suspension of these activities shall not preclude completion of actions to establish a safe conservative condition. These actions minimize the probability of the occurrence of postulated events. It is further required to immediately initiate action to restore the required inverters and to continue this action until restoration is accomplished in order to provide the necessary inverter power to the plant safety systems.

The Completion Time of immediately is consistent with the required times for actions requiring prompt attention. The restoration of the required inverters should be completed as quickly as possible in order to minimize the time the plant safety systems may be without power or powered from its associated regulated transformer bypass source.

SURVEILLANCE SR 3.8.8.1 REQUIREMENTS This Surveillance verifies that the required inverters are functioning properly with all required circuit breakers closed including those from the associated vital battery boards and 480 V shutdown boards and AC vital buses energized from the inverter. The verification of proper voltage and frequency output ensures that the required power is readily available for the instrumentation connected to the AC vital buses. The 7 day Frequency takes into account the redundant capability of the inverters and other indications available in the control room that alert the operator to inverter malfunctions. Upon placing a spare inverter in service, the spare inverter is considered inoperable until this surveillance is completed.

Watts Bar - Unit 2 B 3.8-84 (continued)

Distribution Systems - Operating B 3.8.9 BASES LCO require the associated buses to be energized to their proper voltage from (continued) the associated unit or spare inverter via inverted DC voltage, unit or spare inverter using internal AC source, or the regulated transformer bypass source.

In addition, tie breakers between redundant safety related AC, vital DC, and AC vital bus power distribution subsystems, if they exist, must be open. This prevents any electrical malfunction in any power distribution subsystem from propagating to the redundant subsystem that could cause the failure of a redundant subsystem and a loss of essential safety function(s). If any tie breakers are closed, the affected redundant electrical power distribution subsystems are considered inoperable. This applies to the onsite, safety related redundant electrical power distribution subsystems. It does not, however, preclude redundant 6.9 kV shutdown boards from being powered from the same offsite circuit.

APPLICABILITY The electrical power distribution subsystems are required to be OPERABLE in MODES 1, 2, 3, and 4 to ensure that:

a. Acceptable fuel design limits and reactor coolant pressure boundary limits are not exceeded as a result of AOOs or abnormal transients; and

b. Adequate core cooling is provided, and containment OPERABILITY and other vital functions are maintained in the event of a postulated DBA.

Electrical power distribution subsystem requirements for MODES 5 and 6 are covered in the Bases for LCO 3.8.10, Distribution Systems -

Shutdown.

ACTIONS A.1 With one or more required AC shutdown boards, load centers, motor control centers, or distribution panels, except AC vital buses, in one train inoperable due to one or more inoperable Unit 2 AC shutdown boards, and a loss of function has not occurred, the remaining AC electrical power distribution subsystem in the other train is capable of supporting the minimum safety functions necessary to shut down the reactor and maintain it in a safe shutdown condition, assuming no single failure. The overall reliability is reduced, however, because a single failure in the remaining power distribution subsystems could result in the minimum required ESF functions not being (continued)

Watts Bar - Unit 2 B 3.8-88

Distribution Systems - Operating B 3.8.9 BASES ACTIONS A.1 (continued) supported. Therefore, the required Unit 2 AC shutdown boards, load centers, motor control centers, and distribution panels must be restored to OPERABLE status within 8 hours9.259259e-5 days 0.00222 hours 1.322751e-5 weeks 3.044e-6 months .

Condition A worst scenario is one train of Unit 2 boards without AC power (i.e., no offsite power to the train and the associated DG inoperable). In this Condition, the plant is more vulnerable to a complete loss of AC power. It is, therefore, imperative that the plant operator's attention be focused on minimizing the potential for loss of power to the remaining Unit 2 train by stabilizing the plant, and on restoring power to the affected train. The 8 hour9.259259e-5 days 0.00222 hours 1.322751e-5 weeks 3.044e-6 months time limit before requiring a plant shutdown in this Condition is acceptable because of:

a. The potential for decreased safety if the plant operator's attention is diverted from the evaluations and actions necessary to restore power to the affected train, to the actions associated with taking the plant to shutdown within this time limit; and

b. The potential for an event in conjunction with a single failure of a redundant component in the train with AC power.

The second Completion Time for Required Action A.1 establishes a limit on the maximum time allowed for any combination of required distribution subsystems to be inoperable during any single contiguous occurrence of failing to meet the LCO. If Condition A is entered while, for instance, a DC bus is inoperable and subsequently restored OPERABLE, the LCO may already have been not met for up to 2 hours2.314815e-5 days 5.555556e-4 hours 3.306878e-6 weeks 7.61e-7 months . This could lead to a total of 10 hours1.157407e-4 days 0.00278 hours 1.653439e-5 weeks 3.805e-6 months , since initial failure of the LCO, to restore the AC distribution system. At this time, a DC circuit could again become inoperable, and AC distribution restored OPERABLE. This could continue indefinitely.

The Completion Time allows for an exception to the normal time zero for beginning the allowed outage time clock. This will result in establishing the time zero at the time the LCO was initially not met, instead of the time Condition A was entered. The 16 hour1.851852e-4 days 0.00444 hours 2.645503e-5 weeks 6.088e-6 months Completion Time is an acceptable limitation on this potential to fail to meet the LCO indefinitely.

(continued)

Watts Bar - Unit 2 B 3.8-89

Distribution Systems - Operating B 3.8.9 BASES ACTIONS E.1 (continued)

The second Completion Time for Required Action E.1 establishes a limit on the maximum time allowed for any combination of required distribution subsystems to be inoperable during any single contiguous occurrence of failing to meet the LCO. If Condition E is entered while, for instance, an AC bus is inoperable and subsequently returned OPERABLE, the LCO may already have been not met for up to 8 hours9.259259e-5 days 0.00222 hours 1.322751e-5 weeks 3.044e-6 months . This could lead to a total of 10 hours1.157407e-4 days 0.00278 hours 1.653439e-5 weeks 3.805e-6 months , since initial failure of the LCO, to restore the DC distribution system. At this time, an AC train could again become inoperable, and DC distribution restored OPERABLE. This could continue indefinitely.

This Completion Time allows for an exception to the normal time zero for beginning the allowed outage time clock. This will result in establishing the time zero at the time the LCO was initially not met, instead of the time Condition C was entered. The 16 hour1.851852e-4 days 0.00444 hours 2.645503e-5 weeks 6.088e-6 months Completion Time is an acceptable limitation on this potential to fail to meet the LCO indefinitely.

F.1 With one or more AC electrical power distribution subsystems (except AC vital instrument boards) inoperable due to one or more inoperable Unit 1 AC shutdown boards and a loss of function has not occurred, the remaining AC electrical power distribution subsystems are capable of supporting the minimum safety functions necessary to shut down the reactor and maintain it in a safe shutdown condition, assuming no single failure. The overall reliability is reduced, however, because a single failure in the remaining power distribution subsystems could result in the minimum required ESF functions not being supported. Therefore, the associated required feature(s) must be declared inoperable immediately and the corresponding Condition(s) entered. The Required Action(s) of these Condition(s) will determine the impact of the inoperable Unit 1 AC shutdown board(s).

Condition F is modified by two notes that limit the conditions and parameters that allow entry into Condition F. The first note states that Condition F is only applicable during planned maintenance. This will allow the plant configuration to be aligned to minimize features being inoperable when the opposite unit shutdown board is made inoperable.

The second note limits the applicability of Condition F to the time period when the opposite unit is defueled. This note limits the time period allowing Condition F to be entered, minimizing when the allowance can be utilized. The allowance for Condition F is acceptable based on the following:

(continued)

Watts Bar - Unit 2 B 3.8-94

Distribution Systems - Operating B 3.8.9 BASES ACTIONS F.1 (continued)

a. The opposite unit's AC shutdown boards are not as critical to the operating unit (fewer operating unit loads) as the operating unit's AC shutdown boards.

b. Performing maintenance on these components will increase the reliability of the Class 1E AC Electrical Power Distribution System.

c. The Required Actions associated with the features declared inoperable provide compensatory measures during the performance of the planned maintenance.

d. The limited opportunities that allow the planned maintenance to occur.

During the planned maintenance of the Unit 2 AC shutdown boards, if a condition is discovered on these boards requiring corrective maintenance, this maintenance may be performed under Condition F.

G.1 With one or more AC electrical power distribution subsystems (except AC vital instrument boards) inoperable due to one or more inoperable Unit 1 AC shutdown boards for reasons other than Condition F and a loss of function has not occurred, the remaining AC electrical power distribution subsystems are capable of supporting the minimum safety functions necessary to shut down the reactor and maintain it in a safe shutdown condition, assuming no single failure.

The overall reliability is reduced, however, because a single failure in the remaining power distribution subsystems could result in the minimum required ESF functions not being supported. Therefore, the inoperable Unit 1 AC electrical power distribution subsystem(s) must be returned to OPERABLE status within 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months . The 24 hour2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months time limit before requiring a unit shutdown in this Condition is acceptable because the opposite unit's AC shutdown boards are not as critical to the operating unit (fewer operating unit loads) as the operating unit's AC shutdown boards.

Watts Bar - Unit 2 B 3.8-95

Distribution Systems - Operating B 3.8.9 BASES ACTIONS FH.1 and FH.2 (continued)

If the inoperable distribution subsystem cannot be restored to OPERABLE status within the required Completion Time, the plant must be brought to a MODE in which the LCO does not apply. To achieve this status, the plant must be brought to at least MODE 3 within 6 hours6.944444e-5 days 0.00167 hours 9.920635e-6 weeks 2.283e-6 months and to MODE 5 within 36 hours4.166667e-4 days 0.01 hours 5.952381e-5 weeks 1.3698e-5 months . The allowed Completion Times are reasonable, based on operating experience, to reach the required plant conditions from full power conditions in an orderly manner and without challenging plant systems.

GI.1 With two trains with one or more inoperable distribution subsystems that result in a loss of safety function, adequate core cooling, containment OPERABILITY, and other vital functions for DBA mitigation would be compromised, and immediate plant shutdown in accordance with LCO 3.0.3 is required.

SURVEILLANCE SR 3.8.9.1 REQUIREMENTS This Surveillance verifies that the required AC, vital DC, and AC vital bus electrical power distribution systems are functioning properly, with the correct circuit breaker alignment. The correct breaker alignment ensures the appropriate separation and independence of the electrical trains is maintained, and the appropriate voltage is available to each required bus.

The verification of proper voltage availability on the buses ensures that the required voltage is readily available for motive as well as control functions for critical system loads connected to these buses. The 7 day Frequency takes into account the redundant capability of the AC, vital DC, and AC vital bus electrical power distribution subsystems, and other indications available in the control room that alert the operator to subsystem malfunctions.

REFERENCES 1. Watts Bar FSAR, Section 6 Engineering Safety Features, Section 8 Electric Power, and Section 15 Accident Analysis.

2. Regulatory Guide 1.93, Availability of Electric Power Sources, U.S. Nuclear Regulatory Commission, December 1974.

Watts Bar - Unit 2 B 3.8-96

Enclosure 4 Clean Technical Specification and Bases Changes CNL-18-119 E4-1

WBN Unit 1 Clean Technical Specification and Bases Changes CNL-18-119 E4-2

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.

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

ACTIONS

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

1. LCO 3.0.4.b is not applicable to DGs.

2. Enter applicable Conditions and Required Actions of LCO 3.8.9, Distribution Systems - Operating, when any Condition(s) is entered with no AC power source to any shutdown board resulting in a de-energized shutdown board.

CONDITION REQUIRED ACTION COMPLETION TIME A. One required offsite circuit A.1 Perform SR 3.8.1.1 for 1 hour1.157407e-5 days 2.777778e-4 hours 1.653439e-6 weeks 3.805e-7 months inoperable for reasons required OPERABLE offsite other than Condition D. circuit. AND Once per 8 hours9.259259e-5 days 0.00222 hours 1.322751e-5 weeks 3.044e-6 months thereafter AND 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)

AND (continued)

Watts Bar-Unit 1 3.8-1 Amendment XX

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 13 days from discovery of failure to meet LCO B. One DG inoperable. 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 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 Evaluate availability of 6.9 kV 2 hours2.314815e-5 days 5.555556e-4 hours 3.306878e-6 weeks 7.61e-7 months FLEX DG.

AND Once per 12 hours1.388889e-4 days 0.00333 hours 1.984127e-5 weeks 4.566e-6 months thereafter AND B.3 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 (continued)

Watts Bar-Unit 1 3.8-2 Amendment XX

AC Sources-Operating 3.8.1 ACTIONS CONDITION REQUIRED ACTION COMPLETION TIME B. (continued) B.4.1 Determine OPERABLE DGs 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months are not inoperable due to common cause failure.

OR B.4.2 Perform SR 3.8.1.2 for 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months OPERABLE DGs.

AND B.5 Restore DG to OPERABLE 72 hours8.333333e-4 days 0.02 hours 1.190476e-4 weeks 2.7396e-5 months from status. discovery of unavailability of 6.9 kV FLEX DG AND 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months from discovery of Condition B entry 48 hours5.555556e-4 days 0.0133 hours 7.936508e-5 weeks 1.8264e-5 months concurrent with unavailability of 6.9 kV FLEX DG AND 10 days AND 13 days from discovery of failure to meet LCO (continued)

Watts Bar-Unit 1 3.8-2a Amendment XX

AC Sources-Operating 3.8.1 ACTIONS (continued)

CONDITION REQUIRED ACTION COMPLETION TIME C. Two DGs in Train A 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 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 DGs in Train B thereafter 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 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months are not inoperable due to common cause failure.

OR C.3.2 Perform SR 3.8.1.2 for 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months OPERABLE DGs.

AND C.4 Restore DGs to OPERABLE 72 hours8.333333e-4 days 0.02 hours 1.190476e-4 weeks 2.7396e-5 months status.

AND 6 days from discovery of failure to meet LCO (continued)

Watts Bar-Unit 1 3.8-2b Amendment XX

AC Sources-Operating 3.8.1 ACTIONS (continued)

CONDITION REQUIRED ACTION COMPLETION TIME

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

1. Only applicable during planned maintenance of a Unit 2 AC electrical power distribution subsystem.

2. Only applicable when Unit 2 is defueled.

D. One required offsite circuit D.1 Perform SR 3.8.1.1 for 1 hour1.157407e-5 days 2.777778e-4 hours 1.653439e-6 weeks 3.805e-7 months inoperable solely due to an required OPERABLE offsite offsite power source to circuit. AND 6.9 kV Shutdown Board 2A-A or 2B-B inoperable. Once per 8 hours9.259259e-5 days 0.00222 hours 1.322751e-5 weeks 3.044e-6 months thereafter AND D.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 required feature(s) is 6.9 kV Shutdown inoperable. Board 2A-A or 2B-B concurrent with inoperability of redundant required feature(s)

AND D.3 Restore required offsite circuit 7 days to OPERABLE status.

(continued)

Watts Bar-Unit 1 3.8-3 Amendment XX

AC Sources-Operating 3.8.1 ACTIONS (continued)

CONDITION REQUIRED ACTION COMPLETION TIME E. Two required offsite circuits E.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 E inoperable. concurrent with inoperability of redundant required features.

AND E.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.

F. One required offsite circuit F.1 Restore required offsite circuit 12 hours1.388889e-4 days 0.00333 hours 1.984127e-5 weeks 4.566e-6 months inoperable for reasons to OPERABLE status.

other than Condition D.

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

Train A inoperable.

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

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

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

(continued)

Watts Bar-Unit 1 3.8-4 Amendment XX

AC Sources-Operating 3.8.1 ACTIONS (continued)

CONDITION REQUIRED ACTION COMPLETION TIME H. Required Action and H.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, F, or G not met.

H.2 Be in MODE 5. 36 hours4.166667e-4 days 0.01 hours 5.952381e-5 weeks 1.3698e-5 months I. Two required offsite circuits I.1 Enter LCO 3.0.3. Immediately inoperable.

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

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

J. One required offsite circuit J.1 Enter LCO 3.0.3. Immediately inoperable.

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

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

Watts Bar-Unit 1 3.8-5 Amendment XX

Inverters-Operating 3.8.7 SURVEILLANCE REQUIREMENTS SURVEILLANCE FREQUENCY SR 3.8.7.1 Verify correct inverter voltage, frequency, and 7 days alignment to required AC vital bus.

Watts Bar-Unit 1 3.8-38 Amendment XX

Inverters-Shutdown 3.8.8 SURVEILLANCE REQUIREMENTS SURVEILLANCE FREQUENCY SR 3.8.8.1 Verify correct inverter voltage, frequency, and 7 days alignments to required AC vital bus.

Watts Bar-Unit 1 3.8-40 Amendment XX

Distribution Systems-Operating 3.8.9 3.8 ELECTRICAL POWER SYSTEMS 3.8.9 Distribution Systems - Operating LCO 3.8.9 Train A and Train B AC, vital DC, and AC vital bus electrical power distribution subsystems shall be OPERABLE.

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

ACTIONS CONDITION REQUIRED ACTION COMPLETION TIME A. One or more AC electrical A.1 Restore Unit 1 AC electrical 8 hours9.259259e-5 days 0.00222 hours 1.322751e-5 weeks 3.044e-6 months power distribution power distribution subsystem subsystems inoperable to OPERABLE status. AND due to one or more Unit 1 AC shutdown boards 16 hours1.851852e-4 days 0.00444 hours 2.645503e-5 weeks 6.088e-6 months from inoperable. discovery of failure to meet LCO B. One or more Unit 1 AC B.1 Restore AC vital bus(es) to 2 hours2.314815e-5 days 5.555556e-4 hours 3.306878e-6 weeks 7.61e-7 months vital buses in one channel OPERABLE status.

inoperable. AND 16 hours1.851852e-4 days 0.00444 hours 2.645503e-5 weeks 6.088e-6 months from discovery of failure to meet LCO

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

1. Only applicable during planned maintenance of a Unit 2 AC vital bus.

2. Only applicable when Unit 2 is in MODE 5, MODE 6, or defueled.

C. One Unit 2 AC vital bus in C.1 Restore the Unit 2 AC vital bus 8 hours9.259259e-5 days 0.00222 hours 1.322751e-5 weeks 3.044e-6 months one channel inoperable. to OPERABLE status.

(continued)

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Distribution Systems-Operating 3.8.9 ACTIONS (continued)

CONDITION REQUIRED ACTION COMPLETION TIME D. One or more Unit 2 AC vital D.1 Restore the Unit 2 AC vital 2 hours2.314815e-5 days 5.555556e-4 hours 3.306878e-6 weeks 7.61e-7 months buses in one channel bus(es) to OPERABLE inoperable for reasons other status. AND than Condition C.

16 hours1.851852e-4 days 0.00444 hours 2.645503e-5 weeks 6.088e-6 months from discovery of failure to meet LCO E. One or more vital DC E.1 Restore DC electrical power 2 hours2.314815e-5 days 5.555556e-4 hours 3.306878e-6 weeks 7.61e-7 months electrical power distribution distribution bus to buses inoperable. OPERABLE status. AND 16 hours1.851852e-4 days 0.00444 hours 2.645503e-5 weeks 6.088e-6 months from discovery of failure to meet LCO

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

1. Only applicable during planned maintenance of a Unit 2 AC electrical power distribution subsystem.

2. Only applicable when Unit 2 is defueled.

F. One or more AC electrical F.1 Declare associated required Immediately power distribution feature(s) inoperable.

subsystems inoperable due to one or more Unit 2 AC shutdown boards inoperable.

G. One or more AC electrical G.1 Restore Unit 2 AC electrical 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months power distribution power distribution subsystems inoperable due subsystem(s) to OPERABLE to one or more Unit 2 AC status.

shutdown boards inoperable for reasons other than Condition F.

(continued)

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Distribution Systems-Operating 3.8.9 ACTIONS (continued)

CONDITION REQUIRED ACTION COMPLETION TIME H. Required Action and H.1 Be in MODE 3. 6 hours6.944444e-5 days 0.00167 hours 9.920635e-6 weeks 2.283e-6 months associated Completion Time not met. AND H.2 Be in MODE 5. 36 hours4.166667e-4 days 0.01 hours 5.952381e-5 weeks 1.3698e-5 months I. Two trains with one or I.1 Enter LCO 3.0.3. Immediately more inoperable distribution subsystems that result in a loss of safety function.

SURVEILLANCE REQUIREMENTS SURVEILLANCE FREQUENCY SR 3.8.9.1 Verify correct breaker alignments and voltage to 7 days required AC, vital DC, and AC vital bus electrical power distribution subsystems.

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AC Sources - Operating B 3.8.1 BASES (continued)

APPLICABILITY The AC sources are required to be OPERABLE in MODES 1, 2, 3, and 4 to ensure that:

a. Acceptable fuel design limits and reactor coolant pressure boundary limits are not exceeded as a result of AOOs or abnormal transients; and

b. Adequate core cooling is provided and containment OPERABILITY and other vital functions are maintained in the event of a postulated DBA.

The AC power requirements for MODES 5 and 6 are covered in LCO 3.8.2, AC Sources - Shutdown.

ACTIONS The ACTIONS are modified by a Note that prohibits the application of LCO 3.0.4.b to an inoperable DG. There is an increased risk associated with entering a MODE or other specified condition in the Applicability with an inoperable DG and the provisions of LCO 3.0.4.b, which allow entry into a MODE or other specified condition in the Applicability with the LCO not met after performance of a risk assessment addressing inoperable systems and components, should not be applied in this circumstance.

A second Note provides the appropriate restrictions for a de-energized shutdown board. Pursuant to LCO 3.0.6, the Distribution System ACTIONS would not be entered even if all AC sources to it were inoperable, resulting in de-energization.

Therefore, the ACTIONS are modified by a Note to indicate that when any Condition(s) is entered with no AC power source to any shutdown board resulting in a de-energized shutdown board, the Conditions and Required Actions for LCO 3.8.9, "Distribution Systems - Operating," must be immediately entered. This allows LCO 3.8.1 Conditions to provide requirements for the loss of any combination of AC Sources, without regard to whether a shutdown board is de-energized and LCO 3.8.9 to provide the appropriate restrictions for a de-energized shutdown board.

A.1 To ensure a highly reliable power source remains with one required offsite circuit inoperable for reasons other than Condition D, it is necessary to verify the OPERABILITY of the remaining required offsite circuit on a more frequent basis.

Since the Required Action only specifies perform, a failure of SR 3.8.1.1 acceptance criteria does not result in a Required Action not met. However, if a second required circuit fails SR 3.8.1.1, the second offsite circuit is inoperable, and Condition E, for two required offsite circuits inoperable, is entered.

A.2 Required Action A.2, which only applies if the train cannot be powered from a required offsite source, is intended to provide assurance that an event coincident (continued)

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AC Sources - Operating B 3.8.1 BASES ACTIONS C.4 (continued)

The AND connector between the 72 hour8.333333e-4 days 0.02 hours 1.190476e-4 weeks 2.7396e-5 months and 6 day Completion Times means that both Completion Times apply simultaneously, and the more restrictive Completion Time must be met.

As in Required Action C.2, the Completion Time allows for an exception to the normal time zero for beginning the allowed outage time clock. This will result in establishing the time zero at the time that the LCO was initially not met, instead of at the time Condition C was entered.

D.1, D.2, and D.3 Condition D is modified by two notes that limit the conditions that allow entry into Condition D. The first note states that Condition D is only applicable during planned maintenance. This will allow the plant configuration to be aligned to minimize features being inoperable when the opposite unit shutdown board is made inoperable. The second note limits the applicability of Condition D to the time period when the opposite unit is defueled. This note limits the time period allowing Condition D to be entered, minimizing when the allowance can be utilized.

Condition D is entered for an offsite circuit inoperable solely due to an inoperable power source to 6.9 kV Shutdown Board 2A-A or 2B-B. Required Action D.1 verifies the OPERABILITY of the remaining offsite circuit within an hour of the inoperability and every 8 hours9.259259e-5 days 0.00222 hours 1.322751e-5 weeks 3.044e-6 months thereafter. Since the Required Action only specifies "perform," a failure of the SR 3.8.1.1 acceptance criteria does not result in a Required Action not met.

The Completion Time for Required Action D.2 is intended to allow the operator time to evaluate and repair any discovered inoperabilities. This Completion Time also allows for an exception to the normal "time zero" for beginning the allowed outage time "clock." In this Required Action, the Completion Time only begins on discovery that both:

a. 6.9 kV Shutdown Board 2A-A or 2B-B has no offsite power; and

b. A required feature on the other train is inoperable.

If at any time during the existence of Condition D a redundant required feature subsequently becomes inoperable, this Completion Time begins to be tracked.

A Completion Time of 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months is acceptable, because it minimizes risk while allowing time for restoration before subjecting the unit to transients associated with shutdown. The remaining OPERABLE offsite circuit and DGs are adequate to support these functions. The Completion Time takes into account the (continued)

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AC Sources - Operating B 3.8.1 BASES ACTIONS D.1, D.2, and D.3 (continued) component OPERABILITY of the remaining redundant feature(s), a reasonable time for repairs, and the low probability of a DBA occurring during this period.

Operation may continue in Condition D for a period of 7 days. With one offsite circuit inoperable, the reliability of the functions is degraded. The potential for the loss of offsite power to the redundant feature(s) is increased, with the attendant potential for a challenge to their safety functions.

The required offsite circuit must be returned to OPERABLE status within 7 days.

The 7 days Completion Time takes into account the capacity and capability of the remaining AC sources providing electrical power to the required feature(s), a reasonable time for repairs and the low probability of a DBA occurring during this period of time.

E.1 and E.2 Required Action E.1, which applies when two required offsite circuits are inoperable, is intended to provide assurance that an event with a coincident single failure will not result in a complete loss of redundant required safety functions. The Completion Time for this failure of redundant required features is reduced to 12 hours1.388889e-4 days 0.00333 hours 1.984127e-5 weeks 4.566e-6 months from that allowed for one train without offsite power (Required Action A.2). The rationale for the reduction to 12 hours1.388889e-4 days 0.00333 hours 1.984127e-5 weeks 4.566e-6 months is that Regulatory Guide 1.93 (Ref. 6) allows a Completion Time of 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months for two required offsite circuits inoperable, based upon the assumption that two complete safety trains are OPERABLE. When a concurrent redundant required feature failure exists, this assumption is not the case, and a shorter Completion Time of 12 hours1.388889e-4 days 0.00333 hours 1.984127e-5 weeks 4.566e-6 months is appropriate. These features are powered from redundant AC safety trains. This includes motor driven auxiliary feedwater pumps. Single train features, such as the turbine driven auxiliary pump, are not included in the list.

The Completion Time for Required Action E.1 is intended to allow the operator time to evaluate and repair any discovered inoperabilities. This Completion Time also allows for an exception to the normal time zero for beginning the allowed outage time clock. In this Required Action the Completion Time only begins on discovery that both:

a. All required offsite circuits are inoperable; and

b. A required feature is inoperable.

If at any time during the existence of Condition E (two required offsite circuits inoperable) a required feature becomes inoperable, this Completion Time begins to be tracked.

(continued)

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AC Sources - Operating B 3.8.1 BASES ACTIONS E.1 and E.2 (continued)

According to Regulatory Guide 1.93 (Ref. 6), operation may continue in Condition E for a period that should not exceed 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months . This level of degradation means that the offsite electrical power system does not have the capability to effect a safe shutdown and to mitigate the effects of an accident; however, the onsite AC sources have not been degraded. This level of degradation generally corresponds to a total loss of the immediately accessible offsite power sources.

Because of the normally high availability of the offsite sources, this level of degradation may appear to be more severe than other combinations of two AC sources inoperable (e.g., combinations that involve an offsite circuit and one DG inoperable, or one or more DGs in each train inoperable). However, two factors tend to decrease the severity of this level of degradation:

a. The configuration of the redundant AC electrical power system that remains available is not susceptible to a single bus or switching failure; and

b. The time required to detect and restore an unavailable required offsite power source is generally much less than that required to detect and restore an unavailable onsite AC source.

With both of the required offsite circuits inoperable, sufficient onsite AC sources are available to maintain the plant in a safe shutdown condition in the event of a DBA or transient. In fact, a simultaneous loss of offsite AC sources, a LOCA, and a worst case single failure were postulated as a part of the design basis in the safety analysis. Thus, the 24 hour2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months Completion Time provides a period of time to effect restoration of one of the offsite circuits commensurate with the importance of maintaining an AC electrical power system capable of meeting its design criteria.

According to Reference 6, with the available offsite AC sources, two less than required by the LCO, operation may continue for 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months . If two offsite sources are restored within 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months , unrestricted operation may continue. If only one offsite source is restored within 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months , power operation continues in accordance with Condition A or Condition D, as applicable.

(continued)

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AC Sources - Operating B 3.8.1 BASES ACTIONS F.1 and F.2 (continued)

According to Regulatory Guide 1.93 (Ref. 6), operation may continue in Condition F for a period that should not exceed 12 hours1.388889e-4 days 0.00333 hours 1.984127e-5 weeks 4.566e-6 months .

In Condition F, individual redundancy is lost in both the offsite electrical power system and the onsite AC electrical power system. Since power system redundancy is provided by two diverse sources of power, however, the reliability of the power systems in this Condition may appear higher than that in Condition E (loss of both required offsite circuits). This difference in reliability is offset by the susceptibility of this power system configuration to a single bus or switching failure. The 12 hour1.388889e-4 days 0.00333 hours 1.984127e-5 weeks 4.566e-6 months Completion Time takes into account the capacity and capability of the remaining AC sources, a reasonable time for repairs, and the low probability of a DBA occurring during this period.

G.1 and G.2 With one or more DGs in Train A inoperable simultaneous with one or more DGs in Train B inoperable, there are no remaining standby AC sources. Thus, with an assumed loss of offsite electrical power, insufficient standby AC sources are available to power the minimum required ESF functions. Since the offsite electrical power system is the only source of AC power for this level of degradation, the risk associated with continued operation for a very short time could be less than that associated with an immediate controlled shutdown (the immediate shutdown could cause grid instability, which could result in a total loss of AC power). Since any inadvertent generator trip could also result in a total loss of offsite AC power, however, the time allowed for continued operation is severely restricted. The intent here is to avoid the risk associated with an immediate controlled shutdown and to minimize the risk associated with this level of degradation.

According to Reference 6, with one or more DGs in Train A inoperable simultaneous with one or more DGs in Train B inoperable, operation may continue for a period that should not exceed 2 hours2.314815e-5 days 5.555556e-4 hours 3.306878e-6 weeks 7.61e-7 months .

(continued)

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AC Sources - Operating B 3.8.1 BASES ACTIONS H.1 and H.2 (continued)

If the inoperable AC electric power sources cannot be restored to OPERABLE status within the required Completion Time, the plant must be brought to a MODE in which the LCO does not apply. To achieve this status, the plant must be brought to at least MODE 3 within 6 hours6.944444e-5 days 0.00167 hours 9.920635e-6 weeks 2.283e-6 months and to MODE 5 within 36 hours4.166667e-4 days 0.01 hours 5.952381e-5 weeks 1.3698e-5 months .

The allowed Completion Times are reasonable, based on operating experience, to reach the required plant conditions from full power conditions in an orderly manner and without challenging plant systems.

I.1 and J.1 Condition I and Condition J corresponds to a level of degradation in which all redundancy in the AC electrical power supplies cannot be guaranteed. At this severely degraded level, any further losses in the AC electrical power system will cause a loss of function. Therefore, no additional time is justified for continued operation. The plant is required by LCO 3.0.3 to commence a controlled shutdown.

SURVEILLANCE The AC sources are designed to permit inspection and testing of all important REQUIREMENTS areas and features, especially those that have a standby function, in accordance with 10 CFR 50, Appendix A, GDC 18 (Ref. 8). Periodic component tests are supplemented by extensive functional tests during refueling outages (under simulated accident conditions). The SRs for demonstrating the OPERABILITY of the DGs are in accordance with the recommendations of Regulatory Guide 1.9 (Ref. 3) and Regulatory Guide 1.137 (Ref. 9), as addressed in the FSAR.

Where the SRs discussed herein specify voltage and frequency tolerances, the following is applicable. 6800 volts is the minimum steady state output voltage and the 10 second transient value. 6800 volts is 98.6% of the nominal bus voltage of 6900 V corrected for instrument error and is the upper limit of the minimum voltage required for the DG supply breaker to close on the 6.9 kV shutdown board. The specified maximum steady state output voltage of 7260 V is 110% of the nameplate rating of the 6600 V motors. The specified 3 second transient value of 6555 V is 95% of the nominal bus voltage of 6900 V. The specified maximum transient value of 8880 V is the maximum equipment withstand value provided by the DG manufacturer. The specified minimum and maximum frequencies of the DG are 58.8 Hz and 61.2 Hz, respectively. The steady state minimum and maximum frequency values are 59.8 Hz and 60.1 Hz.

These values ensure that the safety related plant equipment powered from the DGs is capable of performing its safety functions.

(continued)

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Inverters - Operating B 3.8.7 BASES (continued)

SURVEILLANCE SR 3.8.7.1 REQUIREMENTS This Surveillance verifies that the inverters are functioning properly with all required circuit breakers closed and AC vital buses energized from the inverter.

The verification of proper voltage and frequency output ensures that the required power is readily available for the instrumentation of the RPS and ESFAS connected to the AC vital buses. Upon placing a spare inverter in service, the spare inverter is considered inoperable until this surveillance is completed. The 7 day Frequency takes into account the redundant capability of the inverters and other indications available in the control room that alert the operator to inverter malfunctions.

REFERENCES 1. Watts Bar FSAR, Section 8.3.1, "AC Power System."

2. Watts Bar FSAR, Section 15, "Accident Analysis," and Section 6 "Engineered Safety Features."

Watts Bar-Unit 1 B 3.8-84 Revision XX

Inverters - Shutdown B 3.8.8 BASES ACTIONS A.1, A.2.1, A.2.2, A.2.3, and A.2.4 (continued) restrictions will be implemented in accordance with the affected required features LCOs' Required Actions. In many instances, this option may involve undesired administrative efforts. Therefore, the allowance for sufficiently conservative actions is made (i.e., to suspend CORE ALTERATIONS, movement of irradiated fuel assemblies, and operations involving positive reactivity additions). The Required Action to suspend positive reactivity additions does not preclude actions to maintain or increase reactor vessel inventory, provided the required SDM is maintained.

Suspension of these activities shall not preclude completion of actions to establish a safe conservative condition. These actions minimize the probability of the occurrence of postulated events. It is further required to immediately initiate action to restore the required inverters and to continue this action until restoration is accomplished in order to provide the necessary inverter power to the plant safety systems.

The Completion Time of immediately is consistent with the required times for actions requiring prompt attention. The restoration of the required inverters should be completed as quickly as possible in order to minimize the time the plant safety systems may be without power or powered from its associated regulated transformer bypass source.

SURVEILLANCE SR 3.8.8.1 REQUIREMENTS This Surveillance verifies that the required inverters are functioning properly with all required circuit breakers closed and AC vital buses energized from the inverter. The verification of proper voltage and frequency output ensures that the required power is readily available for the instrumentation connected to the AC vital buses. The 7 day Frequency takes into account the redundant capability of the inverters and other indications available in the control room that alert the operator to inverter malfunctions. Upon placing a spare inverter in service, the spare inverter is considered inoperable until this surveillance is completed.

(continued)

Watts Bar-Unit 1 B 3.8-87 Revision XX

Distribution Systems - Operating B 3.8.9 BASES (continued)

ACTIONS A.1 With one or more required AC shutdown boards, load centers, motor control centers, or distribution panels, except AC vital buses, in one train inoperable due to one or more inoperable Unit 1 AC shutdown boards, and a loss of function has not occurred, the remaining AC electrical power distribution subsystem in the other train is capable of supporting the minimum safety functions necessary to shut down the reactor and maintain it in a safe shutdown condition, assuming no single failure. The overall reliability is reduced, however, because a single failure in the remaining power distribution subsystems could result in the minimum required ESF functions not being supported. Therefore, the required Unit 1 AC shutdown boards, load centers, motor control centers, and distribution panels must be restored to OPERABLE status within 8 hours9.259259e-5 days 0.00222 hours 1.322751e-5 weeks 3.044e-6 months .

Condition A worst scenario is one train of Unit 1 boards without AC power (i.e.,

no offsite power to the train and the associated DG inoperable). In this Condition, the plant is more vulnerable to a complete loss of AC power. It is, therefore, imperative that the plant operator's attention be focused on minimizing the potential for loss of power to the remaining Unit 1 train by stabilizing the plant, and on restoring power to the affected train. The 8 hour9.259259e-5 days 0.00222 hours 1.322751e-5 weeks 3.044e-6 months time limit before requiring a plant shutdown in this Condition is acceptable because of:

a. The potential for decreased safety if the plant operator's attention is diverted from the evaluations and actions necessary to restore power to the affected train, to the actions associated with taking the plant to shutdown within this time limit; and

b. The potential for an event in conjunction with a single failure of a redundant component in the train with AC power.

The second Completion Time for Required Action A.1 establishes a limit on the maximum time allowed for any combination of required distribution subsystems to be inoperable during any single contiguous occurrence of failing to meet the LCO. If Condition A is entered while, for instance, a DC bus is inoperable and (continued)

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