ML082670361

Unit 1 - License Amendment (TS-08-09) to Revise the Technical Specifications (Ts), Bases and Updated Final Safety Analysis Report (UFSAR) for the Unit 2 Vital Inverters

ML082670361
Person / Time
Site:	Watts Bar
Issue date:	09/18/2008
From:	Brandon M Tennessee Valley Authority
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
TS-08-09, WBN-TS-08-09
Download: ML082670361 (36)

Text

Tennessee Valley Authority, Post Office Box 2000, Spring City, Tennessee 37381-2000 September 18, 2008 WBN-TS-08-09 10 CFR 50.90 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D. C. 20555 Gentlemen:

In the Matter of the

)

Docket Nos. 50-390 Tennessee Valley Authority

)

50-391 WATTS BAR NUCLEAR PLANT (WBN) - UNIT 1 - LICENSE AMENDMENT (TS-08-09)

TO REVISE THE TECHNICAL SPECIFICATIONS (TS), BASES AND UPDATED FINAL SAFETY ANALYSIS REPORT (UFSAR) FOR THE UNIT 2 VITAL INVERTERS Pursuant to 10 CFR 50.90, Tennessee Valley Authority (TVA) is submitting a request for an Operating License change (TS-08-09) to license NPF-90 for WBN Unit 1. This letter proposes a revision to WBN Unit 1 Technical Specification (TS).3.8.7, "Inverters -

Operating." The TS currently requires one inverter for each of the four channels. The revision addressed by this amendment changes the requirement to two inverters for each of the four channels. The Bases for TS 3.8.7 and TS 3.8.8, "Inverters - Shutdown," are also updated to reflect the change. The proposed amendment is related to construction completion of the 120V AC Vital Instrument Power System for WBN Unit 2. Unit 1 Updated Final Safety Analysis Report (UFSAR) changes are also provided. provides a complete description and justification of the proposed amendment. The remaining enclosures provide the following information: - Changes Proposed for the Vital AC System - Annotated Technical Specifications and Bases changes for WBN Unit 1 - Annotated FSAR changes for WBN Unit 1

U.S. Nuclear Regulatory Commission September 18, 2008 Page 2 TVA has determined that there are no significant hazards considerations associated with the proposed change and that the TS 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), a copy of this proposed license amendment is being forwarded to the state designee for the State of Tennessee.

TVA plans to implement the changes outlined in this license amendment during the upcoming WBN Unit 1 Cycle 9 refueling outage that is scheduled to begin in late September 2009. Based on this, TVA requests approval of the amendment by September 1, 2009. Implementation of the amendment for WBN Unit 1 is to be completed prior to entry into Mode 4 following the refueling outage.

There are no regulatory commitments in this submittal. If you have any questions about this request, please contact me at (423) 365-1824.

I declare under penalty of perjury that the foregoing is true and correct. Executed on this 18th day of September, 2008.

Sincerely, Michael K. Brandon Manager, Site Licensing and Industry Affairs Enclosures

1.

TVA's Evaluation of the Proposed Change

2.

Outline of Key Changes Proposed for the Vital AC System

3.

Annotated Technical Specifications and Bases

4.

Annotated FSAR changes for WBN Unit 1 cc: See page 3

U.S. Nuclear Regulatory Commission September 18, 2008 Page 3 MKB:JEM Enclosures cc (Enclosures):

NRC Resident Inspector Watts Bar Nuclear Plant 1260 Nuclear Plant Road Spring City, Tennessee 37381 Patrick D. Milano, Senior Project Manager U.S. Nuclear Regulatory Commission Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation MS 0-8 H4 Washington, DC 20555-0001 U.S. Nuclear Regulatory Commission Region II Sam Nunn Atlanta Federal Center 61 Forsyth St., SW, Suite 23T85 Atlanta, Georgia 30303 Mr. Lawrence E. Nanny, Director Division of Radiological Health 3 d Floor L & C Annex 401 Church Street Nashville, Tennessee 37243

ENCLOSURE1 TENNESSEE VALLEY AUTHORITY WATTS BAR NUCLEAR PLANT (WBN)

UNIT 1 DOCKET NUMBER 390 PROPOSED LICENSE AMENDMENT REQUEST WBN-TS-2008-09 DESCRIPTION AND EVALUATION OF THE PROPOSED CHANGE

1.0 DESCRIPTION

This letter proposes a revision to WBN Unit 1 Technical Specification (TS) 3.8.7, "Inverters -

Operating." The WBN Unit 1 TS currently require one inverter for each of the four instrument channels. The revision addressed by this amendment changes the requirement to two inverters for each of the four channels. The Bases for TS 3.8.7 and TS 3.8.8, "Inverters -

Shutdown," are also updated to reflect the change.

The loads on the Unit 2 120V AC Vital Instrument Power Boards are required for Unit 1 operation. The Unit 2 120V AC Vital Instrument Power Boards receive their uninterruptible power supply (UPS) from the 120V AC Vital Inverter supplying the associated Unit 1 120V AC Vital Instrument Power Board through the Unit 1 120V AC Vital Instrument Power Board. The proposed amendment modifies the configuration of the four channels such that each Unit 2 Vital Instrument Power Board receives power from new Unit 2 120V AC Vital Inverters. A simplified diagram of the proposed change is provided below:

Existing Configuration - One Channel Proposed Configuration - One Channel E1-1

The vital inverters are designed to provide the required capacity, capability, redundancy, and reliability to ensure the availability of necessary power to vital instrumentation so that the fuel, reactor coolant system, and containment design limits are not exceeded. Separating the Unit 2 loads from the Unit 1 inverters does not alter the accident analyses. The Unit 1 inverters are capable of handling the Unit 1 loads and channel separation is maintained. Design calculations have been updated and document that the new Unit 2 inverters have the capacity for the Unit 2 operating loads.

2.0 PROPOSED CHANGE

WBN Unit 1 Limiting Condition for Operation (LCO) 3.8.7 " Inverters - Operating" states that one inverter in each of the four channels shall be operable and requires the unit to be shutdown if an inverter is not operable after a 24-hour period. The change proposed in the amendment transfers the power supply for the Unit 2 120V AC Vital Instrument Power Boards to new Unit 2 Vital Inverters. Currently WBN Unit 2 is not an operational unit and therefore, the Unit 2 Vital Instrument Power Boards are very lightly loaded (3 KVA or less). The loads on the Unit 2 120V AC Vital Instrument Power Boards are required for Unit 1 operation. This configuration requires a modification prior to the operation of WBN Unit 2, including the installation of additional Unit 2 inverters. Based on this change, the WBN Unit 1 TS requirements and the associated Bases must be updated to address the operation of the system with four Unit 1 unit inverters, four Unit 2 unit inverters and four spare inverters.

Associated changes to the Unit 1 Updated Final Safety Analysis Report (UFSAR) are also included.

As indicated previously, the change to supply the Unit 2 vital power boards from the Unit 2 inverters is part of the construction completion of WBN Unit 2. Details regarding the specific loads that will be supported by the four Unit 2 inverters are provided in Section 4.0 "Technical Analysis," of this enclosure. Also included in Section 4.0 is the justification for the proposed amendment. Provided in Enclosure 2 are conceptual diagrams of the key changes planned for the vital inverters.

The following discussion details the changes proposed to the WBN Unit 1 TS and Bases. The changes to the text of the WBN Unit 1 TS and Bases are reflected as bold italicized print for text additions and strikethrough for deleted text. An annotated version of the affected WBN Unit 1 TS and Bases is provided in Enclosure 3.

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Proposed Revision to WBN Unit 1 TS 3.8.7, "Inverters - Operatinq:"

The text below reflects the revisions proposed for WBN Unit 1 TS 3.8.7:

LCO 3.8.7 APPLICABILITY:

4,eTwo inverters in each of four channels shall be OPERABLE.

MODES 1, 2, 3, and 4.

ACTIONS CONDITION REQUIRED ACTION COMPLETION TIME A.

One inverter in one channel inoperable.

A.1 -------- NOTE --------

Enter applicable Conditions and Required Actions of LCO 3.8.9, "Distribution S ystems-Ope rating",

with any AC Vital Bus deenergized.

Restore inverter to OPERABLE status.

24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> E1-3

Proposed Revision to WBN Unit 1 TS Bases 3.8.7, "Inverters - Operating:"

The text below reflects the revisions proposed for TS Bases 3.8.7:

Change 1 - "Background" Section:

The inverters are the preferred source of power for the AC vital buses because of the stability and reliability they achieve. There is-e-e are two unit inverters (Unit 1 and Unit 2) and one spare inverter per channel, either each of which is capable of supplying its associated AC vital buses (Unit 1 a*d Unit 2) making a total of eight twelve inverters...

Change 2 - Second Paragraph of "LCO" Section:

Maintaining the required inverters OPERABLE ensures that the redundancy incorporated into the design of the RPS and ESFAS instrumentation and controls is maintained. The eight twelve inverters (one Unit 1, one Unit 2 and one spare per channel) ensure an uninterruptible supply of AC electrical power to the AC vital buses even if the 6.9 kV shutdown boards are de-energized.

Change 3 - First Paragraph of "Action A.1:"

With one inverter in a channel inoperable, its associated AC vital busee-becomes inoperable until it is they-az-e re-energized from itsTher associated regulated transformer bypass source, inverter internal AC source or spare inverters.

Proposed Revision to WBN Unit 1 TS Bases 3.8.8. "Inverters - Shutdown:"

The text below reflects the revisions proposed for TS Bases 3.8-8:

Change 1 - "LCO" Section:

The inverters ensure the availability of electrical power for the instrumentation for systems required to shutdown the reactor and maintain it in a safe condition after an anticipated operational occurrence or a postulated DBA. The battery-powered inverters provide uninterruptible supply of AC electrical power to the AC vital buses even if the 6.9 kV shutdown boards are de-energized. OPERABILITY of the inverters requires that the AC vital buses required by LCO 3.8.10, "Distribution Systems - Shutdown" be powered by the inverter. As a minimum, either the channel I and III or II and IV 4Ri4 inverters for each unit (or spare inverters) shall be OPERABLE to support the distribution systems required by LCO 3.8.10....

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3.0 BACKGROUND

The 120V AC Vital Power System is a Class 1 E system that provides an extremely reliable source of instrument and control power for reactor protection circuits and other critical instrumentation systems and components within the plant. The system is configured and loads arranged to preclude the loss of any redundant essential and/or protective function due to a single failure within the system.

The current WBN 120V Vital AC system has four identical power channels (designated as Channels 1, 11, 111, and IV) with the equipment of each channel 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 the distribution board that facilitates load grouping and provides circuit protection. - Figure 1 depicts one channel of the current AC Vital Power System. Each channel has access to a normal, a standby, and a regulated transformer bypass source supply, as well as a spare inverter. In the current configuration, the four WBN Unit 2 Vital Instrument Power Boards are lightly loaded and are fed by the WBN Unit 1 inverters. The WBN Unit 2 Vital Instrument Power Board loads are required for Unit 1 operation.

AC power for each UPS is derived from the Class 1 E Auxiliary Power System via two 480V AC, 3-phase circuits. The DC input power source is derived from the Class 1 E 125V DC Vital Power System. The normal source to each 120V AC Vital Instrument Power Board is from its associated UPS system.

Each UPS consist of three major subassemblies:

• A DC power supply

" An auctioneering circuit 0 An inverter circuit During normal operation the UPS's DC power supply converts the 480V AC normal UPS input to 125V DC. The auctioneering circuit accepts this DC power supply (normal supply) and the 125V Vital Battery Board input (emergency supply) and is capable of a switchless bi-directional transfer between the two sources in the event of a 480V AC supply failure and restoration. During an emergency in which the 480V AC 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 120V AC output to the Vital Instrument Power Boards. If the unit inverter fails or is overloaded, an automatic static switch will transfer the load to the regulated transformer bypass source.

There is also a manual bypass switch to transfer the load manually to the bypass supply.

Each 120V AC Vital Instrument Power Board supplies the following types of loads: reactor protection system, reactor systems instrumentation, separations and interlock relay panels, and other panels and equipment associated with reactor instrumentation and control systems.

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Four new 20 KVA Unit 2 UPSs will be added that contain regulated rectifiers, auctioneered diodes, inverters, static and manual transfer switches and regulated bypass transformers for the WBN Unit 2 Vial AC Power System. The cross-connections between the Unit 1 and Unit 2 120V AC Vital Instrument Power Boards will be removed. The current spare inverters (20 KVA) will be connected to the new Unit 2 UPSs as installed spare swing inverters--one for each channel. After completion of the modification, each channel of vital power'will have three UPS sources: the Unit 1 UPS, the Unit 2 UPS, and a spare swing UPS that can be substituted for either the Unit 1 or Unit 2 UPS for that channel.

The proposed configuration maintains the required channel separation, and no automatic connections are provided between the four channels.

4.0 TECHNICAL ANALYSIS

The following discussion details the justification for the changes.

Justification for the Proposed TS and Bases Revisions:

As noted above, after completion of the modification, each channel of vital power will have three UPS sources: the Unit 1 UPS, the Unit 2 UPS, and a spare swing UPS that can be substituted for either the Unit 1 or Unit 2 UPS for that channel. The WBN Unit 2 Vital Instrument Power Board loads are required for Unit 1 operation. The TS 3.8.7 WBN Unit 1 LCO 3.8.7, "Inverters - Operating," is revised to require two inverters in each of the four channels to be operable. The Bases for TS 3.8.7 and TS 3.8.8, "Inverters - Shutdown," are also updated to reflect the change.

Channel I

II III IV Unit 1 Inverter Rating (KVA) 20 20 20 20 Maximum Load for Unit 1 Board (KVA) 14 14 10.5 10.5 Unit 2 Inverter Rating (KVA) 20 20 20 20 Maximum Load for Unit 2 Board (KVA) 14 14 10.5 10.5 Spare Inverter Rating (KVA) 20

[

20 1

20 20 E1-6

The initial conditions for the Design Basis Accidents (DBAs) defined in the WBN UFSAR assume the Engineered Safety Feature (ESF) systems are operable. The vital inverters are designed to provide the required capacity, capability, redundancy, and reliability to ensure the availability of necessary power to vital instrumentation so that the fuel, reactor coolant system, and containment design limits are not exceeded. Separating the Unit 2 loads from the Unit 1 inverters does not alter the accident analyses as long as the Unit 1 inverters are capable of handling the Unit 1 loads and channel separation is maintained.

In summary, this proposed amendment revises TS 3.8.7 for the addition of the WBN Unit 2 120V AC Vital Inverters. Both the Unit 1 and Unit 2 120V AC Vital Instrument Power Boards will receive UPS power from their associated unit 120V AC Vital Inverters with channel separation being maintained. Each board can be fed from an installed swing inverter when the normal supply is out of service for maintenance or fault conditions.

5.0 REGULATORY SAFETY ANALYSIS 5.1 No Significant Hazards Consideration The WBN Unit 1 TS 3.8.7, "Inverters - Operating," currently requires one inverter for each of the four channels. The revisions addressed by this amendment change the requirement to two inverters for each of the four channels. The Bases for TS 3.8.7 and TS 3.8.8, "Inverters - Shutdown," are also updated to reflect the change.

The Unit 2 Vital Instrument Power Boards presently receive their uninterruptible power supply from the Unit 1 Vital Inverters. Four new 20 KVA Unit 2 UPSs will be added that contain regulated rectifiers, auctioneered diodes, inverters, static and manual transfer switches, and regulated bypass transformers for the WBN Unit 2 Vital AC Power System. The cross-connections between the Unit 1 and Unit 2 120V AC Vital Instrument Power Boards will be removed. The spare inverters will be connected to the new Unit 2 UPSs as installed spare swing inverters--one for each channel. After completion of the modification, each channel of vital power will have three UPS sources: the Unit 1 UPS, the Unit 2 UPS, and a spare swing UPS that can be substituted for either the Unit 1 or Unit 2 UPS for that channel.

Removal of the cross connections between WBN Unit 1 and Unit 2 120V AC Vital Instrument Power Boards will allow Unit 1 and Unit 2 instrument power boards to be fed from their normal unit inverter power supply for each channel under normal conditions and each board to be fed from an installed swing inverter when the normal supply is out of service for maintenance or fault conditions.

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TVA has evaluated whether or not a significant hazards consideration is involved with the proposed amendment by focusing on the three standards set forth in 10 CFR 50.92, "Issuance of amendment," as discussed below:

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

Response: No. The proposed revisions to WBN's Vital AC Power System do not alter the safety functions of the Vital Inverters or the Unit 1 and Unit 2 120V AC Vital Instrument Power Boards. The initial conditions for the DBAs defined in the WBN UFSAR assume the ESF systems are operable. The vital inverters are designed to provide the required capacity, capability, redundancy, and reliability to ensure the availability of necessary power to vital instrumentation so that the fuel, reactor coolant system, and containment design limits are not exceeded. Separating the Unit 2 loads from the Unit 1 inverters does not alter the accident analyses. Design calculations document that the inverters have adequate capacity to support the loads required for Unit 1 operation and no changes are proposed that will impact the separation of the Vital AC Power System.

The inverters and the associated 120V AC Vital Instrument Power Boards are utilized to support instrumentation that monitor critical plant parameters to aid in the detection of accidents and to support the mitigation of accidents, but are not considered to be an initiator of design basis accidents. Based on this and the preceding information, the proposed amendment does not involve a significant increase in the probability or consequences of an accident previously evaluated.

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

Response: No. When implemented, the proposed TS amendment will allow the Unit 2 Vital Instrument Power Boards to receive their UPS power from new Unit 2 inverters.

Calculations have verified that the loads will not affect the ability of the inverters to perform their intended safety functions. In addition, the inverters and the 120V AC Vital Instrument Power Boards are not considered to be an initiator of a DBA. These components provide power to instrumentation that supports the identification and mitigation of accidents as well as system control functions during normal plant operations. The functions of the inverters are not altered by the proposed TS change and will not create the possibility of a new or different accident. Further, the separation of the Unit 2 loads from the Unit 1 inverters is the principal change to the inverter system, and this change is bounded by previously evaluated accident analyses.

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

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

Response: No. The plant setpoints and limits that are utilized to ensure safe operation and detect accident conditions are not impacted by the proposed TS amendment. The El-8

inverters and the 120V Vital Instrument Power Boards will continue to provide reliable power to safety-related instrumentation for the identification and mitigation of accidents and to support plant operation. Therefore, the margin of safety is not reduced.

Based on the above, TVA concludes that the proposed amendment presents no significant hazards consideration under the standards set forth in 10 CFR 50.92(c), and accordingly, a finding of "no significant hazards consideration" is justified.

5.2 Applicable Regulatory Requirements/Criteria Listed below are the sections of the WBN Unit 1 UFSAR that address the Vital AC System:

0 1.2.2.7, "Plant Electrical System"

• 8.1.2, "Plant Electrical Power System" 0 8.3, "Onsite (Standby) Power System" The review of the WBN 120V AC Vital Power system performed by NRC is documented in the Safety Evaluation Report (SER) Related to the Operation of Watts Bar Nuclear Plant Units 1 and 2 - NUREG-0847 (June 1982), and in Supplement 13 (April 1994) and Supplement 14 (December 1994). This assessment of the Vital AC System is documented in the following sections of the SER and supplements:

SER:

" 7.6.1, "System Description"

" 8.3.2.3, "Availability of the Battery Supplies to Vital Instrument Buses"

" 8.3.2.5, "Nonsafety Loads Powered from the DC Distribution System and Vital Inverters"

° 8.3.3.2, "Compliance with GDC 5" Supplement 13:

• 8.3.1.7, "Possible Interconnection Between Redundant Divisions Through the Normal and Alternate Power to the Battery Charger"

" 8.3.1.11, "Test and Inspection of the Vital Power System"

" 8.3.2.5, "Non-Safety Loads Powered from the DC Distribution System and Vital Inverters" Supplement 14:

• 8.3.2.5, "Non-Safety Loads Powered from the DC Distribution System and Vital Inverters" The discussion provided in the SER sections identified that the following key documents were considered in NRC's assessment:

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" Institute of Electrical and Electronic Engineers (IEEE) 308-1971/1974, "IEEE Standard Criteria for Class 1 E Power Systems for Nuclear Power Generating Stations"

" IEEE-485-1983, "Recommended Practices for Sizing Large Lead Storage Batteries for Generating Stations and Substations"

" Regulatory Guide 1.32, "Criteria for Safety-Related Electric Power Systems for Nuclear Power Plants"

" Regulatory Guide 1.81, "Shared Emergency and Shutdown Electric Systems for Multi-unit Nuclear Power Plants" The proposed changes to the Vital AC system maintain compliance with the requirements in the above listed documents.

WBN Unit 1 TS 3.8.7 was changed to its current, form by a Safety Evaluation dated September 8, 2003. As part of the technical evaluation of that change, the NRC noted that the vital power board configuration would need modification if WBN Unit 2 were to become operational. A paragraph was added to the WBN Unit 1 FSAR to provide assurance that the configuration of the vital AC system would be addressed should action be taken to complete WBN Unit 2.

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

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6.0 ENVIRONMENTAL CONSIDERATION

A review has determined that the proposed amendment would change a requirement with respect to installation or use of a facility component located within the restricted area, as defined in 10 CFR 20, or would change an inspection or surveillance requirement. However, the proposed amendment 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 amendment 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 amendment.

7.0 REFERENCES

1. Institute of Electrical and Electronic Engineers (IEEE) 308-1971, "IEEE Standard Criteria for Class 1 E Power Systems for Nuclear Power Generating Stations"

2. IEEE-485-1983, "Recommended Practices for Sizing Large Lead Storage Batteries for Generating Stations and Substations"

3. Regulatory Guide 1.32, "Criteria for Safety-Related Electric Power Systems for Nuclear Power Plants"

4. Regulatory Guide 1.81, "Shared Emergency and Shutdown Electric Systems for Multi-unit Nuclear Power Plants"

5. NRC letter dated September 8, 2003, "Watts Bar Nuclear Plant, Unit 1 - Issuance of an Amendment for the 120V AC Vital Instrument Power System (TAC NO. MB18749)

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ENCLOSURE2 TENNESSEE VALLEY AUTHORITY WATTS BAR NUCLEAR PLANT (WBN)

UNIT 1 DOCKET NUMBER 390 PROPOSED LICENSE AMENDMENT REQUEST WBN-TS-2008-09 Changes Proposed for the Vital AC System The attached drawings illustrate the current (WBN Unit 1 in operation) configuration of the WBN Vital AC system and the concept for the addition of inverters to support dual unit operation (WBN Unit 1 and Unit 2 in operation). For simplicity, only one of the four channels is shown. The four channels are identical. Channel I is shown as an example.

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Figure 1 - WBN Vital AC System Current Configuration E2-2

WBN Vital AC System Conceptual Diagram for the Addition of Inverters to Support Operation of Unit 2 (Unit 2 in Blue)

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ENCLOSURE3 TENNESSEE VALLEY AUTHORITY WATTS BAR NUCLEAR PLANT (WBN)

UNIT 1 DOCKET NUMBER 390 PROPOSED LICENSE AMENDMENT REQUEST WBN-TS-2008-09 Annotated Technical Specifications and Bases Affected Page List:

3.8-37 B 3.8-81 B 3.8-82 B 3.8-83 B 3.8-86 Note:

For the attached annotated pages, wording additions are shown as bold-italicized text and deletions are shown as strikethrough.

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Inverters-Operating 3.8.7 3.8 ELECTRICAL POWER SYSTEMS 3.8.7 Inverters-Operating LCO 3.8.7 Qpe Two inverters in each of four channels shall be OPERABLE.

APPLICABILITY:

MODES 1, 2, 3, and 4.

ACTIONS CONDITION REQUIRED ACTION COMPLETION TIME A.

One inverter in one A.1 NOTE --------- Enter channel inoperable, applicable Conditions and Required Actions of LCO 3.8.9, "Distribution Systems-Operating", with any AC Vital Bus deenergized.

Restore inverter to OPERABLE status.

24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> B.

Required Action and B.1 Be in MODE 3.

6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> associated Completion Time not met.

AND B.2 Be in MODE 5.

36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br /> Watts Bar-Unit 1 3.8-37 E3-2

Inverters - Operating B 3.8.7 B 3.8 ELECTRICAL POWER SYSTEMS B 3.8.7 Inverters - Operating BASES BACKGROUND The inverters are the preferred source of power for the AC vital buses because of the stability and reliability they achieve. There irsone are two unit inverters (Unit 1 and Unit 2) and one spare inverter per channel, eithe* each of which is capable of supplying twG its associated AC vital buses (Un.it 1 and 1Unit 2) making a total of eigh4t twelve inverters. The function of the inverter 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 vital battery provides an uninterruptible power source for the instrumentation and controls for the Reactor Protective System (RPS) and the Engineered Safety Feature Actuation System (ESFAS). The spare inverters will be used as spare uninterruptible power sources; however they will not have a regulated transformer bypass source. Specific details on inverters and their operating characteristics are found in the Watts Bar FSAR, Section 8 (Ref. 1).

APPLICABLE The initial conditions of Design Basis Accident (DBA) and transient analyses in the FSAR, Section 6 (Ref. 2) and Section 15 (Ref. 2), assume Engineered Safety Feature systems are OPERABLE. The inverters are designed to provide the required capacity, capability, redundancy, and reliability to ensure the availability of necessary power to the RPS and ESFAS instrumentation and controls so that the fuel, Reactor Coolant System, and containment design limits are not exceeded. These limits are discussed in more detail in the Bases for Section 3.2, Power Distribution Limits; Section 3.4, Reactor Coolant System (RCS); and Section 3.6, Containment Systems.

The OPERABILITY of the inverters is consistent with the initial assumptions of the accident analyses and is based on meeting the design basis of the plant.

This includes maintaining required AC vital buses OPERABLE during accident conditions in the event of:

a.

An assumed loss of all offsite AC electrical power or all onsite AC electrical power; and

b.

A worst case single failure.

(continued)

Watts Bar-Unit 1 B 3.8-81 E3-3

Inverters - Operating B 3.8.7 BAS ES APPLICABLE SAFETY ANALYSIS (continued)

Inverters are a part of the distribution systems and, as such, satisfy Criterion 3 of the NRC Policy Statement.

LCO The inverters ensure the availability of AC electrical power for the systems instrumentation required to shut down the reactor and maintain it in a safe condition after an anticipated operational occurrence (AO0) or a postulated DBA.

Maintaining the required inverters OPERABLE ensures that the redundancy incorporated into the design of the RPS and ESFAS instrumentation and controls is maintained. The eigh-t twelve inverters (one Uunit 1, one Unit 2 and one spare per channel) ensure an uninterruptible supply of AC electrical power to the AC vital buses even if the 6.9 kV shutdown boards are de-energized.

OPERABLE inverters require the associated AC vital bus to be powered by the 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. The unit inverters have an associated bypass supply provided by a regulated transformer that is automatically connected to the associated AC vital bus in the event of inverter failure or overload. The bypass supply is not battery-backed and thus does not meet requirements for inverter operability. The spare inverters do not have an associated bypass supply. Additionally, the inverter channel must not be connected to the cross train 480 V power supply.

APPLICABILITY The inverters 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.

Inverter requirements for MODES 5 and 6 are covered in the Bases for LCO 3.8.8, "Inverters - Shutdown."

(continued)

Watts Bar-Unit 1 B 3.8-82 E3-4

Inverters - Operating B 3.8.7 BASES (continued)

ACTIONS A.1 With one inverter in a channel inoperable, its associated AC vital buses becomes inoperable until it ist-hey-are re-energized from its4hei associated regulated transformer bypass source, inverter internal AC source, or spare inverters.

For this reason, a Note has been included in Condition A requiring the entry into the Conditions and Required Actions for LCO 3.8.9, "Distribution Systems-Operating." This ensures that the vital bus is reenergized within 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />.

Required Action A.1 allows 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> to fix the inoperable inverter and return it to service. The 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> limit is based upon engineering judgment, taking into consideration the time required to repair an inverter and the additional risk to which the plant is exposed because of the inverter inoperability. This has to be balanced against the risk of an immediate shutdown, along with the potential challenges to safety systems such a shutdown might entail. When the AC vital bus is powered from its associated regulated transformer bypass source it is relying upon interruptible AC electrical power sources (offsite and onsite). The uninterruptible inverter source to the AC vital buses is the preferred source for

.powering instrumentation trip setpoint devices. Alternatively, an inverter may be restored to OPERABLE status by substituting its spare inverters and performing the required surveillance.

B.1 and B.2 If the inoperable devices or components 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 <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and to MODE 5 within 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br />.

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 1 B 3.8-83 E3-5

Inverters - Shutdown B 3.8.8 BASES (continued)

LCO The inverters ensure the availability of electrical power for the instrumentation for systems required to shutdown the reactor and maintain it in a safe condition after an anticipated operational occurrence or a postulated DBA. The battery powered inverters provide uninterruptible supply of AC electrical power to the AC vital buses even if the 6.9 kV shutdown boards are de-energized.

OPERABILITY of the inverters requires that the AC vital buses required by LCO 3.8.10, "Distribution Systems - Shutdown" be powered by the inverter. As a minimum, either the channel I and Ill or l1 and IV u4At inverters for each unit (or spare inverters) shall be OPERABLE to support the distribution systems required by LCO 3.8.10. The unit inverters have an associated bypass supply provided by a regulated transformer that is automatically connected to the associated AC vital bus in the event of inverter failure or overload. The bypass supply is not battery-backed and thus does not meet requirements for inverter operability.

The spare inverters do not have an associated bypass supply. Additionally, the inverter channel must not be connected to the cross-train 480 V power supply.

This ensures the availability of sufficient inverter power sources to operate the plant in a safe manner and to mitigate the consequences of postulated events during shutdown (e.g., fuel handling accidents).

APPLICABILITY The inverters required to be OPERABLE in MODES 5 and 6 and during movement of irradiated fuel assemblies provide assurance that:

a.

Systems needed to mitigate a fuel handling accident are available;

b.

Systems necessary to mitigate the effects of events that can lead to core damage during shutdown are available; and

c.

Instrumentation and control capability is available for monitoring and maintaining the plant in a cold shutdown condition or refueling condition.

Inverter requirements for MODES 1, 2, 3, and 4 are covered in LCO 3.8.7.

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 (continued)

Watts Bar-Unit 1 B 3.8-86 E3-6

ENCLOSURE 4 TENNESSEE VALLEY AUTHORITY WATTS BAR NUCLEAR PLANT (WBN)

UNIT 1 DOCKET NUMBER 390 PROPOSED AMENDMENT REQUEST WBN-TS-2008-09 Annotated FSAR Changes Affected Page List:

1.2-8 Table 3.2-3 Sheet 3 of 5 8.1-2 8.3-22 8.3-23 8.3-24 8.3-32 8.3-39 8.3-58 8.3-71 Table 8.3-10 Sheet 1 of 1 Table 8.3-11 Sheet 1 of 1 E4-1

WBNP-6 The safety-related plant distribution system receives ac power from CSST C and D through the shutdown boards (which are powered from the offsite power system), or four 4400 kW diesel-generator standby (onsite) power sources, and distributes it to both safety-related and nonsafety-related loads in the plant. The two preferred circuits have access to the TVA transmission network which in turn has multiple interties with other transmission networks.

The safety-related loads for the plant are divided into two redundant load groups. Each redundant load group has access to each of the two preferred offsite sources. One load group with its two associated diesel generators can provide the safety functions. The electrical systems are described in Sections 8.2 and 8.3.

The vital ac and dc control and instrument power system consists of five 125V batteries (fifth vital battery can be switched for any of the other four), six battery chargers (two spares), and

-eighl-120V ac inverters (four spares) with their respective safety-related loads. The 125V dc Distribution System is a safety-related system which receives power from independent battery chargers and 125V dc batteries and distributes it to safety-related loads. The 120V ac Distribution System receives power from ffr inverters and distributes it to the safety-related loads. These systems are described in Sectfons 8.2 and 8.3.

1.2.2.8 Cooling Water The condenser circulating water system (CCW) provides cooling water for the dissipation of waste heat for the power generation cycle while meeting applicable effluent limitations and water quality standards. The CCW includes the circulating water pumps, circulating water conduits, yard holding pond, main condensers, hyperbolic natural draft cooling towers, desilting basin., and the supplemental condenser cooling water (SCCW) system. The SCCW system supplies water from the Watts Bar Reservoir to provide a source of cooler water to the existing Unit I cooling tower discharge flume.

The blowdown from the CCW is used to dilute and dispense low-level radioactive liquid wastes.

The CCW pumping station is located in the yard between the Turbine Building and the cooling towers. There are four circulating water pumps that operate in parallel and circulate water from the cooling tower cold water basin, through the condenser, and back into the heat exchanger section of the tower.

The essential raw cooling water system (ERCW) provides the essential auxiliary support functions to the engineered safety features (ESF) of the plant. The system is designed to provide a continuous flow of cooling water to those systems and components necessary to plant safety either during normal operation or under accident conditions. The ERCW system consists of eight ERCW pumps, four traveling screens, four traveling screen wash pumps, and four strainers located in the intake pumping station.

1.2-8

WBNP-6 TABLE 3.2-3 (Sheet 3 of 5)

ELECTRICAL POWER SYSTEM EQUIPMENT DESIGNED TO OPERATE DURING AND AFTER A "SAFE SHUTDOWN EARTHQUAKE" (Cont'd)

Qualified in Equipment Number Number Conformance (1)

Per Unit / In Plant with IEEE 344-1971 120V AC Vital Plant Control Power System Static Inverter System Components 4/

Ali Yes

a.

Auctioneer unit

b.

A transformer rectifier power supply C. A single phase static inverter with associated equipment for control, voltage, regulation, filtering, and instrumentation

d.

Regulated transformer bypass source with static and manual bypass switches (Unit 1).1 -1, 1-11, 1 -MI, 1I V 1,."

2-*-;

j

-i (Spare) 0-I, 0-I1, 0-n, 0-_IV 120V AC Vital Instrument Power Boards 4/8 Yes (Unit 1) 1 -1, l1-H, I -MI, 1 -IV (Unit 2) 2-1, 2-1, 2-1rn, 2-IV 125V DC Vital Plant Control Power System 480V AC Vital Transfer Switches

-/4 Note (4)

Yes Transfer SW I, II, III, IV 125V DC Vital Battery Chargers

-/6 Note (4)

Yes Chgrs I, II, III, IV, Spare Chgr 6-S and 7-S Transfer Devices for Spare 125V DC Vital Battery Chargers

-/4 Note (4)

Yes DC Transfer Switch 6DC-8 DC Transfer Switch 7DC-S AC Transfer Switch 6AC-S AC Transfer Switch 7AC-S 480V AC Vital Disconnect Panels Panel I, 11, HI, IV

-/4 Note (4)

Yes

WBNP-4 The safety objective for the power system is to fuirnish adequate electric power to ensure that safety related loads function in conformance with design criteria and design bases. Major loads on the electric power system having assigned safety related functions are shown in Table 8.1-1.

The safety objective has been accomplished by: (1) establishing design criteria and bases that conform to regulatory documents and accepted design practice, and (2) implementation of these criteria and bases in a manner that assures a system design and a constructed plant which satisfies all safety requirements. The applicable documents governing the design are shown in' Section 8.1.5.

Figures 8.1-2 and 8.1-2A depict the plant distribution system that receives ac power from:

a.

One nuclear power unit.

b.

The two independent preferred (offsite) power circuits, which have access to the TVA transmission network, and in turn have multiple interties with other transmission networks.

c.

The four 4400-kW diesel generator standby (onsite) power sources.

d.

The 4400-kW additional diesel generator unit, which may be used as a replacement for any one of the four existing diesel generators. (Not required for Unit 1 operation.)

The power received from the above sources is distributed to both safety related and nonsafety related loads in the plant.

The safety related loads are arranged electrically into four power trains. Power trains IA and 2A comprise load group A. Power trains IB and 2B comprise load group B. Two diesel generators and one load group can provide all safety related functions to mitigate a LOCA. Each power train has access to a diesel generator (standby source) and each of the two preferred offsite sources.

Figure 8.1-3 depicts the vital ac and de controJ power distribution systems that connect four

.125V batteries, four battery chargers an urw 1 20V ac uninterruptable power systems (UPS) with their respective safety related loads and non safety related loads. The 125V dc distribution system is a safety related system which receives power fi'oit four independent battery chargers and four 125V dc batteries and distributes it to safety rla ted loads and nonsafety related loads.

The 120V ac distribution system receives power fron*7alIndependent UPSs mad distributes it to the safety related and non-safety related loads. These systems are described in Sections 8.2 and 8.3.

8.1-2

WBNP-6 Peak Voltage Change %

Historical Information 72-Hour Tests -Historical Information g

Demonstration of Equivalent Reliability - Historical Information 120V Vital AC System

{tL0o (W& jV-%

vv4e-S The configuration of the ac ontrol power system is shown in Figure 8.1-3..itrhas four identical power channels (dLsignated as Channels I, II, III and IV), with the'equipment of each channel being electrically physically independent from the equipment of other channels.

Each channel consists ofa r and the distribution panels (one per unit) which facilitates load grouping and provides circuit protection. Each channel has access to a normal, a standby, and a regulated transformer bypass source supply, as well as a spare inverter. The ac control power system is grounded.

InthisGnit 2 distrib8.3-on panels (Vital22Ument Po oards) aref

{by th Ui mi i support f operation. T~ieonfijgurat~io~l rqi r

Smo i, io mv

'rs.

t_

• .*,8.3-22

W I P WBNP-6 The spare inverters may be used as an alternate uninterruptible power supply for the distribution panels and may be shared between unit inverters of the same channel.

Physical Arrangement of Components The inverters are located in the Auxiliary Building at Elevation 772. The Channels I and II inverters are located in the Unit 1 area and the Channels III and IV inverters are located in the Unit 2 area. The Channels I and II inverters are separated from Channels III and IV inverters by an 8-inch reinforced concrete wall, extending to the ceiling. The Channel I and the Channel III inverters are separated from the Channel II and the Channel IV inverters respectively by a distance of 60 feet. The physical arrangement of the inverters is shown on Figure 8.3-36.

System Reliability

&IlA0 The system incorporates features which serve o increa e overall reliability. Each channel has access to four power sources: two 480V sourc a 125V dc source, and a 120V ac regulated transformer bypass source. There unit and a spare inverter for each channel capable of receiving power from either the 480V ac source or the 125V dc source. Each inverter has an auctioneered solid-state transfer between the 480V ac and 125V dc input sources. The unit inverter output has an automatic make-before-break solid-state transfer to the regulated bypass source in the event of inverter failure or overload. An automatically synchronized manual transfer between the output of the unit inverter and the 120V regulated transformer bypass source and between the unit inverter system output and the spare inverter is provided so that the inverters may be taken out of service for maintenance without interrupting power to the loads.. Spare inverters do not have a regulated transformer bypass source. The current limiting feature of the inverters provide self-protection from load faults. The inverters and instrumentation power boards are monitored to alert the operator of abnormalities. The distribution bus is sectionalized with coordinated fuses to prevent losing the entire board due to failure of a single branch circuit breaker.

Loads Each channel supplies the following types of loads: reactor protection system, reactor systems instrumentation, separations and interlock relay panels, and other panels and equipment associated with reactor instrumentation, and control systems. Figures 8.3-37 through 8.3-40 list the loads on each instrument power board and identify the safety and nonsafety-related loads.

The capability of the inverter to supply its connected load is discussed in Section 8.3.1.2.

Nonsafety-related loads are supplied from Class 1E circuit breakers located on the Class IE instrument power board to provide qualified fault isolation.

Loads are assigned to each channel according to its divisional separation requirement. Those loads requiring four divisions of separation are assigned to the four channels. Those loads requiring two divisions of separation are assigned to Channels I and II (Trains A and B, respectively) for Unit 1 and Channels III and IV (Trains A and B, respectively) for Unit 2. The auxiliary feedwater pump turbines' components powered by this system, receive power from either Channel III or IV for Unit 1 and Channels I and II for Unit 2. Loads which do not require divisional separation are assigned among the four channels of each unit.

8.3-23

WBNP-6 Inverter The normal supply of ac power to the distribution panels is from the unit inverter for each channel. The unit inverter system consists of four major subassemblies: a dc power supply, an auctioneering circuit, a regulated transformer bypass source circuit, and an inverter circuit. The alternate supply of ac power to the distribution panels is from the spare inverter for each channel Which have all the same subassemblies except for the regulated transformer bypass source circuit.

The de power supply converts the 480V ac normal inverter input to direct current. The auctioneering circuit accepts the de power supply (normal supply) and battery (emergency supply) inputs and permits a switchless bidirectional transfer between them in the event of 480V ac supply failure and restoration. The dc output of the auctioneering circuit is converted to ac by the inverter circuit. The regulated transformer bypass source circuit on the unit inverters provides 120V ac output to the distribution panels by bypassing the inverter via an automatic static switch or manual transfer switch.

AC power input for each inverter is derived from the station auxiliary power system (see Figure 8.1-3) via two physically and electrically independent circuits. Each circuit has access to a.

preferred (offsite) and a standby (onsite) source. If the normal circuit supplying an inverter is unavailable, the other circuit is selected by a manual transfer. The emergency dc power input for each inverter is from the corresponding channel dc distribution panel.

The inverters are a solid-state type which converts 3-phase 480V ac and 125V dc inputs to a nominal 120V ac output having a rated capacity of 167 amperes for load power factors from 0.8 to 1.0. Over this output current range, the ac output voltage does not vary more than 2.0% for normal 480V ac supply voltage amplitude variations of +10/-15% and frequency variations of 2.0%, and an emergency supply voltage variation from 100V dc to 140V dc. The output frequency regulation is 60 Hz +0.5 Hz with a maximum harmonic distortion of 5% and a maximum rate of change of 1.0 Hz per second.

Some operational features of the inverters are: (1) an output voltage adjustable over the range of 11 5V to 125V, (2) synchronization of the unit inverter to the internal 120V ac regulated transformer bypass source and synchronization of the spare inverter to the output of the unit inverter, (3) automatic transfer with no loss of load from the unit inverter output to the regulated transformer bypass source upon unit inverter failure or overload through a static switch, (4) a current-limit feature which limits short circuit currents to 200% rated output, (5) protection devices which prevent a failed inverter from loading its associated normal and emergency power sources, and (6) metering and alarm circuits to monitor the inverter output.

Vital Instrument Power Board The eight vital instrument power boards (four per unit) are located in four separate rooms in the Auxiliary Building at Elevation 757. Mounted on each of these boards are: the distribution bus, subdistribution bus fuses, distribution bus disconnect switch, high speed branch circuit breakers, and various instruments for monitoring distribution bus ac voltage. On each of the Unit 1 boards, there is an alternate supply transfer switch that aligns the spare inverter as the alternate power supply for tlc ietzrc-,ncctesW Unit 1 and Unit 2 boards on each channel.

0- 1 4-AC.-

or, 8.3-24

WBNP-6 Availability IEEE Std 308-1971 The standby power supply is available following the loss of both preferred power supplies within a time consistent with the requirements of the engineered safety features and the shutdown system under normal and accident conditions.

8.3.1.2,2 Analysis of Vital 120V ac Control Power Systems AC Distribution Boards and Inverters General The 120V ac Class 1E electrical systems were designed, components fabricated, and have been or will be installed meeting the requirements of the NRC 10 CFR 50 Appendix A General Design Criteria 1-5, 17 and 18, IEEE Std 308-1971, NRC Regulatory Guide 1.6, IEEE Std 336-197 1, and other applicable criteria as referenced herein.

The system for each unit consists of eight uninterruptible power supply (UPS) systems (one unit and one spare per channel) and distribution boards, cable, and other hardware. -Fr at f

uit,-erlY7Ife Unit 1 and Unit 2 Vital Instrument Power Boards for each channel are ie-%&f

".eea and supplied from a.igle UPS or regulated transformer bypass source. 4n-thi

~oniguito~,theony la~isuplid ow the board&re those reoquied-for eperaficn cf4Unit.

The distribution boards and UPS system are grouped into four divisions of separation. The boards of each division are located in separate rooms at Elevation 757 of the Auxiliary Building which is designed as a Seismic Category I structure. Likewise, the inverters are located at Elevation 772 and are divisionally separated. Refer to Section 8.3.1.4.2 for separation confornance.

Since this equipment is outside the primary containment area, it will not be exposed to hostile environments or significant radiation due to a LOCA. The system design, equipment location, separation, and redundancy assure ability to meet the requirements for the applicable accident in Chapter 15 are in full compliance with NRC General Design Criteria 17 and Regulatory Guide 1.6, Revision 0.

120V AC Distribution Boards All load output circuit breakers used on the boards are high-speed hydraulic-magnetic type having the unique characteristic of high-speed tripping at low-fault currents. This type breaker is capable of providing low-fault current selective tripping when the board power source is from the inverter which has a low-fault current capability. The breakers are fed in groups from a stub bus with a current-limiting fuse and are capable of interrupting the fault currents available from all power sources. The fuses and breakers have current-time tripping characteristics which are coordinated with the load cable thermal characteristics to provide selective clearing of all faults.

The exact board distribution circuit and loads can be seen by referring to Figures 8.3-37 through Figure 8.3-40.

8.3-32

WBNP-6 Sump pumps with level switches for automatic pump operation are located in the manholes to prevent water accumulation due to leakage into the manhole. Manholes will be included in the plant maintenance program and will be inspected every 12 montlhs for sump pump operability and flooding.

Cables are designed to operate in wet conditions. The Class IE cables required to operate the plant in the flooded condition are continuous or provided with a waterproof splice in a manhole.

Cables have been tested at the factory by the manufacturer according to TVA specifications, which invoke ICEA (formerly IPCEA) standards for cables installed in wet environments.

Each manhole or cable pull point is accessible for periodic visual inspection of cables during normal operations or preflood conditions for the life of the plant. The duct runs are designed suchthat inundated testing of redundant cables can be conducted, TVA does not use directly buried conduit for any Class lE cable installation. This avoids possible adverse effects if such conduit were to be buried under a roadway.

8.3.1.3 Physical Identification of SafetV-Related Equipment in AC Power Systems The onsite power system equipment and associated field wiring is identified so that two factors are physically apparent to plant operating and maintenance personnel:

1.

That equipment and wiring is safety-related, and

2.

That equipment and wiring is properly identified as part of a particular division of separation.

The scheme used to physically identify safety-related ac electrical equipment employs a suffix label. The suffix label added to the equipment name is -A, or -B, which represents, train A or train B diesel-generator power source. For example, 6900V shutdown board IA-A is safety-related equipment, where the I indicates Unit I, the A represents board A, and the -A is assigned to train A.

The 125V de vital system is shared between both units and divided into four channels. The 125V vital charger, 125V vital battery board, and 125V vital battery of each channel is physically identified in its label by I, 11, Ill, or IV, In addition, 125V Vital Battery V, physically identified in its label by "S", may serve as a temporary replacement for either Battery I, I1, 111, or IV.

The 120V ac vital instrumentation and control power systenmis divided into four channels. The 120V ac vital inverters and vital instrument power boards are identified by a unit prefix and a -I, *

-II, -III, or -IV suffix, respectively. For example, 120V ac vital instrument power 1-I is safety-related equipment, where the 1 indicates Unit 1, and the I is assigned to Channel I. The spare inverters have a Unit 0 prefix.

8.3-39

WBNP-4 The 125V dc vital power system shall be composed of the four redundant channels (designated as Channels 1, 11, 111, and 1V) and consists of four lead-acid-calcium batteries, sixbattery chargers (including two spare chargers), four distribution boards, battery racks, and the required cabling, instrumentation and protective features. Each channel is electrically and physically independent from the equipment of all other channels so that a single failure in one channel will not cause a failure in another channel. Each channel consists of a battery charger which supplies normal dc power, a battery for emergency dc power, and a battery board which facilitates load grouping and provides circuit protection. These four channels are used to provide emergency power to the 120V ac vital power system which furnishes control power to the reactor protection system. No automatic connections are used between the four redundant channels.

Battery Boards 1, 11, 111, and IV have a charger normally connected to them and also have mauial access to a spare (backup) charger for use upon loss of the normal charger, Additionally, Battery Boards I, II, i11, and IV have manual access to the fifth vital battery system. The fifth 125V dc Vital Battery System is intended to serve as a replacement for any one of the four 125V do vital batteries during their testing, maintenance, and outages with no loss of system reliability under any mode of operation. See Figure 8.3-56.

The process for substituting the fifth vital battery for a primary battery is administratively controlled through plant operating procedures.

In this mode of operation -the fifth vital battery shall be maintained at the required nominal voltage level by the appropriate spare vital battery charger and shall be available, as needed, to supply all loads connected to the primary vital battery board. The substitution of Vital Battery V for a primary vital battery shall in no manner degrade either the reliability or the capacity of the 125V dc vital power system: all system requirements shall be satisfied and all parameters unchanged. (Note: to fulfill these requirements, the fifth vital battery and all associated cabling shall be sized such that the minimum primary vital battery board voltage with fifth vital battery connected is, under all circumstances, greater than or equal to the primary battery board voltage with the primary vital battery connected.)

System Design Reqtuirements The requirements described below wer-e implemented in the design of the Vital dc Power System.

Redundancy The system is composed of four redundant channl, The four channels are used to provide emergency power to the four vital I 20V tere i

rs~wch supply control power to the reactor protection system, Other loads are either two divisional or nondivisional loads, No automatic connections are used between the four redundant channels.

8.3-58

WBNP-4 8.3.2.4 Independence of Redundant DC Power Systems The treatment of the redundant onsite do power systems is included in Section 8.3,1.4 with the onsite ac power systems.

The 125-V do power required for engineered safety features is arranged as follows:

Unit I 'A' Train - Vital Battery I Unit I 'B' Train - Vital Battery I1 Unit 2 'A' Train - Vital Battery tII Unit 2 'B' Train - Vital Battery IV Four channel 120V ac vital instrumen t power p supplied fr'om four uninterruptable power y

rits The normal input to thesIO-,is sppl1ied from the 480V shutdown system with backup p-y coming from the vital batteries. The 480V ac input is rectified and biased against the do by means of an auctioneered diode circuit to permit use of the battery source if the ac input voltage is lost.

The safety loads supplied from these units have been grouped as follows:

Unit 1, Channel I Unit I RPS Channel I input relays, ESF 'A' Train output relays.

Unit 1, Channel II Unit I RPS Channel II input relays, ESF 'B' Train output relays.

Unit 1. Channel III Unit I RPS Channel III input relays, Unit I, Channel IV Unit I RPS Channel IV input relays.

The limiting conditions studies was the loss of offsite power concurrent with the failure of one battery. Table 8.3-13 shows the results of this study.

Conformance with General Design Criteria, Regulatory Guides, and Branch Technical Positioin.

GDC 5-The failure of a vital battery does not significantly impair the ability of systems and components important to safety to perform their safety functions, including, in the event of an accident in one unit an orderly shutdown and cooldown of the remaining unit.

RG 1.6, There are no provisions for automatically connecting one Revision 0 load group to another load group. There are no provisions for automatically transferring loads between redundant load groups.

8.3-71

WBNP-4 Table 8.3-10 (Sheet I of 1)

-COMPONENTS HAVING MANUAL',RANSFER BETWEEN POWER DIVISIONS I

Component

! 25V Bat Chgr I & lnverteriý)

125V Bat Chgy II & Inverter@

125V Bat Chgr III & Inverter@

125V Bat Chgr IV & Inverte 125V Spare Bat Chgr 6 125V Spare Bat Chgr 7 Component Cooling System Ptmlp C-S Spent Fuel Pit Pump C-S Unit I 125V Aux Feedwater Turbine (AFWT), DC Control Power Unit 1 120V AFWT, AC Control Power Unit 2 125 AFWT, DC Control Power Unit 2 120V AFWT, AC Control Power Spare 125V DC Charger DC (6-s)

Spare 125V DC Charger DC (7-S)

Normal Supply.

480V Shutdown Bd 1A2-A 480V Shutdown Bd 1B2-B 480V Shutdown Bd 2A2-A 480V Shutdown Bd 2B2-B Reactor MOV Bd 1A2-A*

Reactor MOV Bd 2A2-A*

480V Shutdown Bd 2B2-B 480V Shutdown Bd lAI-A 125V DC Vital Battery Board I11"*

120V AC Vital Instrument Power Board l-I1 125V DC Vital Battery Board I**

120V AC Vital Instrument Power Board 2-I 125V DC Vital Battery Board I***

125V DC Vital Battery Board III***

Alte&nate Supply 480V Shutdown Bd lB I-B 480V Shutdown Bd IAI-A 480V Shutdown Bd 2B1-B 480V Shutdown Bd 2A I-A Reactor MOV Bd IB2-B*

Reactor MOV Bd 2B2-B*

480V Shutdown Bd 1A2-A 480V Slutdown Bd 2BI-B 125V DC Vital Battery Board IV**

120V AC Vital Instrument Power Board I -IV 125V DC Vital Battery Board ll**

120V AC Vital Instrument Power Board 2-11 125V Vital Battery Board 1I***

125 DC Vital Battery, Board IV***

I.

These boards are neither the normal nor alternate supply but are the available boards from whicl the loads can be supplied.

• During station blackout, the 125V AFWT DC control power manual transfer switch (unit 1) must be placed and maintained in the normal position.

These boards are neither the normal nor alternate supply but are boards (loads) which can be conmected via these switches to the spare battery chargers.

WBNP-4 TABLE 8.3-11 (Sheet I of 1) 120V A.C. Vital Instrument Power Board Load Data Channel 1-I 1-H 1-Iff 1-V2 (KVA)__

I Load Lmito J,7 4

-K 5

,o (KVA)I o

1,0 1 5 D5

'4 1ý