ML15147A029

Proposed License Amendment Request (Lar), TS 3.8.1 - AC Sources - Operating, Revised Surveillance Requirement

ML15147A029
Person / Time
Site:	North Anna
Issue date:	05/22/2015
From:	Mark D. Sartain Virginia Electric & Power Co (VEPCO)
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
15-065
Download: ML15147A029 (28)

Text

VIRGINIA ELECTRIC AND POWER COMPANY RICHMOND, VIRGINIA 23261 May 22, 2015 U.S. Nuclear Regulatory Commission Serial No.15-065 Attn: Document Control Desk NL&OS/RAP Washington, DC 20555 Docket No. 50-339 License No. NPF-7 VIRGINIA ELECTRIC AND POWER COMPANY (DOMINION)

NORTH ANNA POWER STATION UNIT 2 PROPOSED LICENSE AMENDMENT REQUEST (LAR)

TS 3.8.1 - AC SOURCES - OPERATING REVISED SURVEILLANCE REQUIREMENT In a September 10, 2013 letter (Serial No.13-423), Dominion requested an amendment, in the form of a change to the Technical Specifications (TS) to the Facility Operating License Number NPF-7 for North Anna Power Station Unit 2 to modify Surveillance Requirement (SR) 3.8.1.8. The proposed amendment was subsequently withdrawn in an April 16, 2014 letter (Serial No. 14-423A). This letter submits an updated proposed amendment request that provides additional supporting information.

Pursuant to 10 CFR 50.90, Dominion herewith re-submits an amendment request, in the form of a change to the TS to the Facility Operating License Number NPF-7 for North Anna Power Station Unit 2. TS 3.8.1, "AC Sources - Operating", contains SR 3.8.1.8, which requires verification of the capability to manually transfer Unit 1 4.16 kV ESF bus AC power sources from the normal offsite circuit to the alternate required offsite circuit. As currently stated in SR 3.8.1.8 Note 1 and the TS Bases, this SR is only applicable to Unit 1 because it does not have an alternate offsite power feed for the ESF buses. However, Dominion is developing a plant modification to install an alternate offsite power feed to each of the Unit 2 4.16 kV ESF buses such that the final configuration for Unit 2 will be similar to the existing Unit 1 configuration. Therefore, a change is proposed to delete SR 3.8.1.8 Note 1, thereby eliminating the limitation that excludes Unit 2 from the manual transfer verification requirement of SR 3.8.1.8. This TS change will be implemented after the Unit 2 modification is installed. Following implementation of the proposed TS change, the Unit 2 SR 3.8.1.8 manual transfer verification will be performed consistent with the verification currently performed for Unit 1.

A discussion of the proposed change is provided in Attachment 1. The marked-up and typed TS pages affected by the proposed amendment are provided in Attachments 2 and 3, respectively. A mark-up of the TS Bases affected by the proposed amendment is provided in , for information only.

Serial No.15-065 Docket No. 50-339 TS 3.8.1, AC Sources - Operating Page 2 of 3 Dominion has evaluated the proposed amendment and determined that it does not involve a significant hazards consideration as defined in 10CFR50.92. The basis for this determination is included in Attachment 1. The evaluation also determined that operation with the proposed change will not result in a significant increase in the amount of effluents that may be released offsite or a significant increase in individual or cumulative occupational radiation exposure. Therefore, the proposed amendment is eligible for categorical exclusion from an environmental assessment as set forth in 10 CFR 51.22(c)(9). Pursuant to 10 CFR 51.22(b), no environmental impact statement or environmental assessment is needed in connection with approval of the proposed change. The basis for this determination is also included in Attachment 1. The proposed amendment has been reviewed and approved by the Facility Safety Review Committee.

Dominion requests approval of the proposed amendment by March 1, 2016. Once approved, the amendment will be implemented during the Unit 2 outage in March of 2016, after installation of the plant modification.

If you have any questions or require additional information, please contact Ms. Diane Aitken at (804) 273-2694.

Very truly yours, Mark D. Sartain Vice President - Nuclear Engineering Vicki L.Hull i- NOTARY PUBLIC 4 Commonwealth of Virginia Reg. # 140542 MyCoisso Expires May 31, 2016 COMMONWEALTH OF VIRGINIA Iy COUNTY OF HENRICO The foregoing document was acknowledged before me, in and for the County and Commonwealth aforesaid, today by Mark D. Sartain, who is Vice President - Nuclear Engineering of Virginia Electric and Power Company.

He has affirmed before me that he is duly authorized to execute and file the foregoing document in behalf of that Company, and that the statements in the document are true to the best of his knowledge and belief.

2 Acknowledged before me this (,_ day of, 2015.

My Commission Expires: 5 3 I - I.

Notary Public Commitments made in this letter: None Attachments:

1. Discussion of Change

2. Marked-up Technical Specifications Page

3. Proposed Technical Specifications Page

4. Marked-up Technical Specifications Bases (For Information Only)

Serial No.15-065 Docket No. 50-339 TS 3.8.1, AC Sources - Operating Page 3 of 3 cc: U.S. Nuclear Regulatory Commission Marquis One Tower 245 Peachtree Center Avenue, NE Suite 1200 Atlanta, Georgia 30303-1257 Mr. J. E. Reasor, Jr.

Old Dominion Electric Cooperative Innsbrook Corporate Center 4201 Dominion Blvd.

Suite 300 Glen Allen, Virginia 23060 State Health Commissioner Virginia Department of Health James Madison Building - 7th floor 109 Governor Street Suite 730 Richmond, Virginia 23219 NRC Senior Resident Inspector North Anna Power Station Dr. V. Sreenivas NRC Project Manager U. S. Nuclear Regulatory Commission One White Flint North Mail Stop 08 G-9A 11555 Rockville Pike Rockville, Maryland 20852-2738 Ms. K. R. Cotton-Gross NRC Project Manager U. S. Nuclear Regulatory Commission One White Flint North Mail Stop 08 G-9A 11555 Rockville Pike Rockville, Maryland 20852-2738

Attachment 1 (Serial No.15-065)

Discussion of Change North Anna Power Station Unit 2 Virginia Electric and Power Company (Dominion)

Serial No.15-065 Docket No. 50-339 Attachment 1 Page 2 of 11

1.0 INTRODUCTION

Pursuant to 10 CFR 50.90, Virginia Electric and Power Company (Dominion) requests an Amendment to Facility Operating License Number NPF-7 in the form of a change to the Technical Specifications (TS) for North Anna Power Station Unit 2. The proposed change deletes Note 1 to Surveillance Requirement (SR) 3.8.1.8 to remove the limitation that excludes Unit 2 from the SR 3.8.1.8 verification test requirement.

SR 3.8.1.8 requires verification of the capability to manually transfer AC power sources for the Unit 1 emergency buses from the normal offsite circuit to the alternate required offsite circuit.

The current Technical Specifications were established prior to alternate required offsite circuits being available to Unit 2. However, Dominion is developing a plant modification to install an alternate offsite circuit for each Unit 2 emergency bus and, as a result, the verification test will need to be performed for Unit 2.

Technical Specification Bases changes reflecting the proposed change are included in for information only. The Technical Specification Bases will be revised in accordance with the Technical Specification Bases Control Program, TS 5.5.13, following approval of the proposed Technical Specification changes.

2.0 PROPOSED CHANGE

SR 3.8.1.8 is to be revised to delete the limitation in Note 1. Deleted text is shown with a double strikethrough.

SR 3.8.1.8 ----------------------- NOTES-----------------------

1.This Su.olonoi nly applisablo to Unit 1.

2= This Surveillance shall not normally be performed in MODE 1 or 2.

However, this Surveillance may be performed to reestablish OPERABILITY provided an assessment determines the safety of the unit is maintained or enhanced.

Verify manual transfer of AC power sources from the normal offsite circuit to the alternate required offsite circuit.

3.0 BACKGROUND

As described in North Anna Power Station UFSAR Chapter 8, the station service power system sources are the station service transformers (SSTs), the reserve station service transformers (RSSTs), the Alternate AC Diesel Generator, and the Emergency Diesel Generators. The SSTs are also referred to as the normal sources; the RSSTs are referred to as the preferred sources, and the Emergency Diesel Generators as the standby sources. Reserve station service power for start-up and emergency use is supplied by three 3-phase 34.5/4.16-kV RSSTs, via the 4.16 kV normal and transfer buses. The RSSTs supply preferred power to the 4.16 kV emergency buses via Transfer Buses D, E, and F (UFSAR Figure 8.2-1). In addition to the normal alignment, Transfer Buses D and E can be cross-tied via 4160 V Bus OL. The 4.16 kV

Serial No.15-065 Docket No. 50-339 Attachment 1 Page 3 of 11 emergency buses are arranged in two separate systems designated H and J. The H bus is associated with train A Reactor Protection System, while the J bus is associated with train B Reactor Protection System.

On Unit 1, normal to emergency bus ties are also provided that function as an alternate offsite AC circuit, such that two independent offsite power sources are provided to each emergency bus. These additional bus ties exist between Emergency Bus 1H and Normal 4.16 kV Bus 1B and between Normal 4.16 kV Bus 2B and Emergency Bus 1J. These bus ties have a normally open breaker at each bus.

Unit 2 does not have additional normal to emergency bus ties that provide an alternate offsite AC circuit to each emergency bus similar to Unit 1. On Unit 2, the 4.16 kV 2H and 2J Emergency Buses may be interconnected by a breaker that is normally removed from its cubicle located on Bus 2H. The breaker on Unit 2 is under strict operational supervision and is provided for maintenance purposes.

Improved Standard Technical Specifications (ISTS) SR 3.8.1.8 requires verification of the automatic or manual transfer of the AC power sources from the normal offsite circuit to each alternate offsite circuit every 18 months. As described above, the Unit 2 design does not have alternate circuits from the offsite AC sources. Therefore, at the time North Anna implemented the ISTS, Note 1 was added to TS SR 3.8.1.8 to state: "The Surveillance is only applicable to Unit 1."

Dominion is currently developing a plant modification to install an alternate offsite AC circuit to each Unit 2 Emergency Bus 2H and 2J. In addition, the existing manual cross-tie between Buses 2H and 2J will be permanently removed. The plant modification will be evaluated in accordance with 10 CFR 50.59. The additional offsite circuits will require testing in accordance with TS SR 3.8.1.8. As a result, the limitation in SR 3.8.1.8, Note 1, is no longer necessary and Dominion proposes that it be removed.

4.0 TECHNICAL ANALYSIS

AND SAFETY CONSIDERATIONS 4.1 Design Description The design function of the alternate required offsite circuit is the same as the preferred offsite power source. It provides sufficient power to support all Class 1 E systems, structures, and components (SSCs), and station auxiliaries in the event of a loss of the normal offsite AC power source. Therefore, the additional circuits that will feed the Unit 2 emergency buses from offsite AC power will be designed in accordance with 10 CFR 50, Appendix A, General Design Criteria (GDC) 17.

The modified Unit 2 configuration will be similar to the existing Unit 1 configuration.

Interconnections will be provided between normal and emergency buses such that each emergency bus is capable of being powered from: (a) the preferred offsite source (normally assigned RSST), (b) the alternate required offsite circuit (assigned normal bus which can be powered from either an SST or from an RSST which is different than the normally assigned RSST), or (c) the assigned Emergency Diesel Generator. An important difference between the Units 1 and 2 electrical design configurations is that the Unit 1 design includes a Generator Output Breaker (GOB), whereas Unit 2 does not. The proposed plant modification described

Serial No.15-065 Docket No. 50-339 Attachment 1 Page 4 of 11 above does not install a GOB for Unit 2. This design difference has been accounted for in determination of acceptable alternate offsite power supply configurations for Unit 2.

A normally open cross-tie connection will be provided from Unit 1 Normal Bus 1A to Unit 2 Emergency Bus 2J and a separate normally open cross-tie connection will be provided from Normal Bus 2C to Emergency Bus 2H. The assigned alternate supply from each normal bus is associated with an RSST that is different from the existing emergency bus preferred RSST supply. This will allow maintenance on an RSST without the need for an outage and allow greater electrical bus configuration flexibility. The transfer of each 4.16 kV emergency bus to the 4.16 kV normal bus is a manual action that requires interlocks and permissives to be met for the connection to be made. This connection to the alternate required offsite circuit for each Unit 2 emergency bus will be analogous to the preferred offsite power source.

Breakers will be provided to prevent fault current propagating through the system and to provide equipment protection in case of a fault. Relaying will ensure breakers trip for various conditions such as overcurrent or directional overcurrent. Breaker control will be provided in the Control Room.

4.2 Design Analysis As required by TS 3.8.1 .a, a minimum of two independent qualified offsite sources connecting the 230/500 kV switchyard to each unit's ESF (emergency) buses must be operable for Unit operation. The 500-34.5 kV and 230-34.5 kV Station Reserve Transformers (SRTs) supply preferred power to the RSSTs, which then supply power to the emergency buses. Buses 2H and 2J are not supplied simultaneously from the same preferred offsite power source. In addition, there are two qualified 500 kV lines from the switchyard to the Units 1 and 2 generator step-up transformers (GSUs) and SSTs. The new preferred alternate offsite power supply cross-ties and the backup alternate alignment, which utilizes existing Bus OL, provide for connecting additional qualified power sources to Buses 2H and 2J. The qualified circuits between the offsite transmission network and the onsite Class 1E AC electrical power distribution system, as described in TS 3.8.1, are identified in the table below. Also identified are the new preferred alternate circuits, which are added by the proposed plant modification, and the backup alternate circuit, which uses Bus OL to interconnect plant Transfer Buses D and E.

Emergency Alignment Unit Status Transmission Offsite Station Bus (Note 1) Network Transformer Transformer Bus 2H Normal Unit 1 Online or Offline, 500kV Switchyard SRT-2 to Bus 4 RSST B (Existing) Unit 2 Online or Offline 230kV Switchyard SRT-3 to Bus 5 Preferred Unit 1 Online or Offline, Unit 2 Generator / Unit 2 GSU SST 2C Alternate Unit 2 Online 500kV Switchyard (Note 2) 500kV Switchyard

__ ___ ____ __ I_

SRT-1 to Bus 3]

___ ___ _ J (Note 2)

RSST C

Serial No.15-065 Docket No. 50-339 Attachment 1 Page 5 of 11 Emergency Alignment Unit Status Transmission Offsite Station Bus (Note 1) Network Transformer Transformer 230kV Switchyard SRT-3 to Bus 5 Unit 1 Online or Offline, 500kV Switchyard Unit 2 GSU SST 2C Unit 2 Offline ]

(Links Removed) 500kV Switchyard SRT-1 to Bus 3

I_ ] RSST C (Note 2) 230kV Switchyard SRT-3 to Bus 5 Backup Alternate Unit 1 Online or Offline, Unit 2 Online or Offline 500kV Switchyard 1 SRT-2 to Bus 4 RSST A 1 (through OL Bus) 230kV Switchyard SRT-3 to Bus 5 Bus 2J Normal Unit 1 Online or Offline, 500kV Switchyard SRT-1 to Bus 3 RSST C (Existing) Unit 2 Online or Offline 1 _

230kV Switchyard SRT-3 to Bus 5 Preferred Unit 1 Online, Unit 1 Generator/ Unit 1 GSU SST 1A Alternate Unit 2 Online or Offline 500kV Switchyard 500kV Switchyard SRT-2 to Bus 4 RSST A (Note 2) 230kV Switchyard SRT-3 to Bus 5 Unit 1 Offline, 500kV Switchyard Unit 1 GSU SST 1A Unit 2 Online or Offline 500kV Switchyard SRT-2 to Bus 4 RSST A (Note 2) 230kV Switchyard SRT-3 to Bus 5 Note 1: The alternate alignments will be established using the new Unit 2 bus cross-tie (preferred alternates) and the backup alternate alignment will be established utilizing Bus OL to interconnect plant transfer buses. These do not replace the Normal (existing) alignment.

Note 2: When the specified alternate alignment to the emergency bus is placed in service, the other emergency bus must also be placed in an alternate alignment for both buses (2H and 2J) to be considered operable. This satisfies the requirement for two qualified circuits between the offsite transmission network and the onsite Class 1E AC electrical power distribution system per TS 3.8.1.a.

Serial No.15-065 Docket No. 50-339 Attachment 1 Page 6 of 11 The proposed Unit 2 alternate offsite power supply alignments have been evaluated for conformance with GDC 17. When the preferred alternate offsite power supplies are in service and an accident or a trip on Unit 2 occurs, Station Service Bus 2C will auto-transfer to RSST C, which is supplied by a qualified offsite source, while Bus 2J will continue to be supplied by the Unit 1 Main Generator (or the 500 kV switchyard) through Station Service Bus 1A. If an accident or a trip on Unit 1 occurs, the Unit 1 GOB opens allowing Bus 2J to continue to be fed from the Unit 1 Station Service Transformer 1A via the 500 kV switchyard, while Bus 2H will continue to be supplied by the Unit 2 Main Generator through Station Service Bus 2C.

With the backup alternate alignment, which utilizes Bus OL to interconnect the transfer buses, the emergency buses will continue to be supplied by the RSSTs. Hence, a trip of either Unit will not result in a loss of power from any of the interconnected transfer buses or downstream emergency buses.

To assess the effects on auxiliary power system voltages, bounding analyses were performed using the ETAP computer program with the proposed cross-ties implemented, and Bus OL utilized to interconnect plant transfer buses.

For evaluation of the new bus cross-ties, the first analysis modeled a Unit 2 Containment Depressurization Actuation (CDA) followed by a Unit 2 Station Service Bus auto-transfer at 30 seconds. In this analysis, emergency Bus 2H was loaded on SST 2C (which is auto-transferred to RSST C at 30 seconds), while emergency Bus 2J was loaded on Station Service Bus 1A. The second analysis modeled a Unit 2 trip event with the cross-ties in pl'ace followed by a Unit 2 Station Service Bus 2C auto-transfer to RSST C at 30 seconds. Based on the analyses performed, sufficient margins exist to allow the cross-ties to be used during these bounding scenarios and the proposed new paths are sufficient to satisfy GDC 17 safety function requirements.

For evaluation of the Bus OL interconnection of the transfer buses, bounding ETAP analyses were also developed to determine if voltages are adequate for various motor starts and various modes of operation with the OL interconnection utilized. Several ETAP analyses modeling Unit 2 CDA after a Unit I Trip, Unit 1 CDA after a Unit 2 Trip, and a Unit 2 Trip were developed. Based on the analyses performed, sufficient margins exist to allow the cross-ties to be used during these bounding scenarios and are sufficient to satisfy GDC 17 safety function requirements.

In addition, as described in UFSAR Section 8.3.1.1.1, a load shedding scheme is currently implemented to alleviate potential low-voltage profile conditions during combined Units 1 and 2 operation using the RSSTs, only. The existing load shedding scheme is not altered by the proposed use of the new bus cross-ties or use of Bus OL to interconnect plant transfer buses.

The load shedding discussed in UFSAR Section 8.3.1.1.1 is applicable to station service loads, only. Based on the results of the developed ETAP analysis, no additional load shedding scheme is necessary. However the following restrictions will be imposed when the new bus cross-ties are placed in service, or when Bus OL is used to interconnect plant transfer buses. These are similar to the existing restrictions implemented for the Unit 1 cross-ties:

1) The station service buses for Units 1 and 2 will be limited to 3000 amps at all times except when Station Service Bus 1A is carrying Bus 2J (Bus 1A will be limited to 2500 amps to allow additional emergency bus load).

Serial No.15-065 Docket No. 50-339 Attachment 1 Page 7 of 11

2) If Bus 2H is cross-tied to Station Service Bus 2C, then the Unit 2 Main Generator MVAR will be limited to +300 MVAR Out (lagging) to ensure adequate Bus 2H voltage in accordance with GDC17. If Bus 2J is cross-tied to Station Service Bus 1A, then the Unit 1 Main Generator MVAR will be limited to +300MVAR Out (lagging) to ensure adequate Bus 2J voltage in accordance with GDC17.

3) When the OL Bus is utilized to interconnect plant transfer buses and normally open Intake Structure Bus 1G/2G cross-tie breaker 15G10 is closed to link Intake Structure Buses 1G and 2G, main feedwater and condensate pump motors will be prohibited from starting.

Therefore, depending on the Bus OL alignment, a condensate pump motor and feedwater pump motor will need to be confirmed to be running or in pull-to-lock.

4) With respect to station service bus loading, there are existing limits on both Units pertaining to what motors are allowed to auto-start depending on the alignment of the station service buses. The table below summarizes the loads that are proposed to be inhibited or are already inhibited from auto-starting based on the breaker configuration. For the OL Bus breaker configurations, loads that are proposed to be inhibited from auto-starting based on the breaker configuration are shown below. For the remaining breaker configurations the loads listed are automatically inhibited by the load shed logic circuitry during an event such as a CDA or LOCA with and without the cross-ties in place.

Breaker(s) Closed Load Inhibited - Unit I Load Inhibited -

(Note 1) Unit 2 (Note 1) 25H11 None 2-CN-P-1C 2-FW-P-1C1 2-BC-P-1 B 2-FW-P-1 C2 25H1, 25C1, and 15C1 1-CN-P-1C 2-CN-P-1C 1-FW-P-1C1 2-FW-P-1C1 1-BC-P-1 B 2-BC-P-1 B 1-FW-P-1C2 2-FW-P-1 C2 25J4 1-CN-P-1A None 1-FW-P-iAl 1-FW-P- 1A2 25J4, 25A1, and 15A1 1-CN-P-lA 2-CN-P-1A 1-FW-P-iA1 2-FW-P-1A1 1-FW-P-iA2 2-FW-P-1A2 05L1, 05L3 None 2-FW-P-1A1 2-FW-P-1A2 2-CN-P-1A 2-FW-P-1C1 2-FW-P-1 C2 2-CN-P-1C Note 1: Equipment tag nomenclature: CN-P is condensate pump; FW-P is main feedwater pump; BC-P is bearing cooling water pump.

Serial No.15-065 Docket No. 50-339 Attachment 1 Page 8 of 11 4.3 Surveillance Testing The existing Unit 1 SR 3.8.1.8 is addressed in periodic test procedure 1-PT-80.2, Testing of the Emergency Bus Alternate Power Supply. This Unit 1 procedure transfers emergency Buses 1 H and 1J from RSSTs C and A to Station Service Buses 1 B and 2B, respectively, per operating procedure 1-OP-26.1, Transferring 4160-Volt Buses.

Because the new Unit 2 alternate offsite AC power source configuration will be similar to the Unit 1 configuration in both design and fault protection, the new Unit 2 circuits may be tested in the same manner and on the same frequency as the Unit 1 circuits. A new periodic test procedure (similar to 1 -PT-80.2) will be developed for the Unit 2 emergency bus alternate power supply testing. The periodic test procedure will transfer emergency Buses 2H and 2J from RSSTs B and C to Station Service Buses 2C and 1A, respectively, per a proposed revision to operating procedure 2-OP-26.1, Transferring 4160-Volt Buses. The new Unit 2 Periodic Test procedure will detail the primary and alternate 4.16kV connections, similar to the existing Unit 1 periodic test procedure. The procedure will include testing of the backup alternate alignment, which utilizes Bus OL to interconnect transfer buses D and E. The verification test will consist of a manual transfer between two offsite power circuits. The conditions under which the manual transfer is verified will be limited to those that will not challenge steady state operation or challenge the safety of the Unit consistent with the conditions applied to manual transfer for Unit 1.

Therefore, the proposed change to SR 3.8.1.8 that will subject the Unit 2 alternate required offsite circuits to the same manual transfer Surveillance Requirement as the Unit 1 alternate required offsite circuits is considered acceptable. TS Bases Section 3.8.1.8, which currently describes the plant conditions under which manual transfer testing is conducted for Unit 1, will be revised to apply to Unit 2, as well.

5.0 REGULATORY EVALUATION

No Significant Hazards Consideration The proposed change deletes Note 1 to SR 3.8.1.8 to remove the limitation that excludes Unit 2 from the SR 3.8.1.8 verification test requirement. Dominion has evaluated the proposed changes to the Technical Specifications (TS) using the criteria in 10 CFR 50.92 and has determined that the proposed changes do not involve a significant hazards consideration.

Serial No.15-065 Docket No. 50-339 Attachment 1 Page 9 of 11

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

Response: No The previously evaluated accident that could be affected is a complete loss of offsite power (LOOP). Analyses have been performed to confirm that power distribution system voltages and currents with both of the new Unit 2 alternate normal to emergency bus ties in service are adequate during a Unit trip scenario. The conditions under which the Unit 2 manual transfer capability is verified are the same as Unit 1. The verification test may only be performed under conditions that will not challenge steady state operation or challenge the safety of the Unit. Therefore, the Unit 2 verification test (manual transfer between Unit 2 normal offsite circuit and alternate required offsite circuit) will not significantly increase the probability of a LOOP.

Once a LOOP has occurred, the consequences are unaffected by availability of offsite power (normal offsite circuit and alternate required offsite circuit). Therefore, the Unit 2 verification test (normal offsite circuit and alternate required offsite circuit) will not affect the 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 The purpose of the surveillance test is to verify the capability to manually transfer AC power sources from the normal offsite circuit to the alternate required offsite circuit.

The only effect of the change is to permit the new Unit 2 required offsite circuits to be tested in the same manner and frequency as the corresponding Unit 1 circuits. Since the Unit 2 circuits are similar to the Unit 1 circuits, and the Unit 1 test is a required TS Surveillance to demonstrate operability of the alternate offsite circuits, permitting the Unit 2 circuits to undergo the same Surveillance test will 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 proposed change enables SR testing of the new Unit 2 alternate offsite AC circuits to verify the capability to manually transfer AC power sources from the normal offsite circuit to the alternate required offsite circuit.

The margin of safety is related to the confidence in the ability of the fission product barriers to perform their design functions during and following an accident situation.

These barriers include the fuel cladding, the reactor coolant system, and the containment system. The proposed change does not directly affect these barriers, nor does it involve any adverse impact on the Class 1 E circuits or SSCs supplied by Class 1E power. Therefore, the proposed change will not involve a significant reduction in a margin of safety.

Serial No.15-065 Docket No. 50-339 Attachment 1 Page 10 of 11 Regulatory Requirements 10 CFR 50.36(c)(2)(ii) requires that a technical specification limiting condition for operation must be established for each item meeting one or more of the following criteria.

1. Installed instrumentation that is used to detect, and indicate in the control room, a significant abnormal degradation of the reactor coolant pressure boundary.

2. A process variable, design feature, or operating restriction that is an initial condition of a design basis accident or transient analysis that either assumes the failure of, or presents a challenge to the integrity of a fission product barrier.

3. A structure, system, or component that is part of the primary success path and which functions or actuates to mitigate a design basis accident or transient that either assumes the failure of or presents a challenge to the integrity of a fission product barrier.

4. A structure, system, or component which operating experience or probabilistic risk assessment has shown to be significant to public health and safety.

North Anna Power Station Unit 2 was issued construction permit No. CPPR-78 dated February 1971, based on the station design being in conformance with the General Design Criteria for Nuclear Power Plants, published in 1966. However, to facilitate review by the AEC, the FSAR discussed the design of the station relative to the new design criteria published in 1971. The General Design Criteria that are relevant to the TS SR change include Criterion 17 - Electric Power Systems, and Criterion 18 - Inspection and Testing of Electric Power Systems.

Criterion 17 - Electric Power Systems, requires 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 safety function for each system (assuming the other system is not functioning) shall be to provide sufficient capacity and capability to assure that (1) specified acceptable fuel design limits and design conditions of the reactor coolant pressure boundary are not exceeded as a result of anticipated operational occurrences and (2) the core is cooled and containment integrity and other vital functions are maintained in the event of postulated accidents. 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. A switchyard common to both circuits is acceptable.

Each of these circuits shall be designed to be available in sufficient time following a loss of all onsite ac power supplies and the other offsite electric power circuits, to ensure that specified acceptable fuel design limits and design conditions of the reactor coolant pressure boundary are not exceeded. One of these circuits shall be designed to be available within a few seconds following a LOCA to ensure that core cooling, containment integrity, and other vital safety functions are maintained. Provisions shall be included to minimize the probability of losing electric power from any of the remaining supplies as a result of or coincident with, the loss of power from the transmission network, or the loss of power from the onsite electric power supplies.

Serial No.15-065 Docket No. 50-339 Attachment 1 Page 11 of 11 Criterion 18 - Inspection and Testing of Electric Power systems, requires that electric power systems important to safety shall be designed to permit appropriate periodic inspection and testing of important areas and features, such as wiring, insulation, connections, and switchboards, to assess the continuity of the systems and the condition of their components.

The systems shall be designed with a capability to test periodically (1) the operability and functional performance of the components of the systems, such as onsite power sources, relays, switches, and buses, and (2) the operability of the systems as a whole and, under conditions as close to design as practical, the full operation sequence that brings the systems into operation, including operation of applicable portions of the protection system, and the transfer of power among the nuclear power Unit, the offsite power system, and the onsite power system.

The proposed change will enable TS SR testing of the new Unit 2 alternate offsite AC circuits to verify the capability to manually transfer AC power sources from the normal offsite circuit to the alternate required offsite circuit. The proposed change will not remove any TS SR requirements for test criteria or test schedules. Thus, General Design Criteria 17 and 18 continue to be met.

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.

6.0 CONCLUSION

Based on the above discussion, Dominion concludes that the proposed amendment does not involve a 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.

Also, based on the considerations discussed above, Dominion concludes that: (1) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, (2) 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.

7.0 PRECEDENT North Anna Power Station is unique in that the emergency bus power feed configuration is different for Units 1 and 2. A directly applicable similar precedent was not identified.

Attachment 2 (Serial No.15-065)

Marked-up Technical Specifications Page North Anna Power Station Unit 2 Virginia Electric and Power Company (Dominion)

- NUCLEAR DESIGN INFORMATION PORTAL -

AC Sources-Operating 3.8.1 SURVEILLANCE REQUIREMENTS SURVEILLANCE FREQUENCY

+

SR 3.8.1.7 ----------------- NOTE------------

All EDG starts may be preceded by an engine prelube period.

Verify each required EDG starts from In accordance standby condition and achieves with the Surveillance

a. In

• 10 seconds, voltage 2 3960 V and Frequency Control frequency Ž 59.5 Hz; and Program

b. Steady state voltage Ž 3740 V and 4580 V, and frequency ; 59.5 Hz and 60.5 Hz.

SR 3.8.1.8 NOTES-----------

1 . T! 1 . UI tvV W2i1b U1 I!y dPP1 lLod!]! L-t i 11l

-.2-This Surveillance shall not normally be performed in MODE 1 or 2. However, this Surveillance may be performed to reestablish OPERABILITY provided an assessment determines the safety of the unit is maintained or enhanced.

Verify manual transfer of AC power sources In accordance from the normal offsite circuit to the with the alternate required offsite circuit. Surveillance Frequency Control Program North Anna Units 1 and 2 3.8.1-10 Amendmerfts 262

Attachment 3 (Serial No.15-065)

Proposed Technical Specifications Page North Anna Power Station Unit 2 Virginia Electric and Power Company (Dominion)

AC Sources-Operating 3.8.1 SURVEILLANCE REQUIREMENTS SURVEILLANCE FREQUENCY SR 3.8.1.7 ------------------ NOTE ------------

All EDG starts may be preceded by an engine prelube period.

Verify each required EDG starts from In accordance standby condition and achieves with the Surveillance

a. In

• 10 seconds, voltage Ž 3960 V and Frequency Control frequency Ž 59.5 Hz; and Program

b. Steady state voltage Ž 3740-V and

• 4580 V, and frequency Ž 59.5 Hz and

• 60.5 Hz.

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

This Surveillance shall not normally be performed in MODE I or 2. However, this Surveillance may be performed to reestablish OPERABILITY provided an assessment determines the safety of the unit is maintained or enhanced.

Verify manual transfer of AC power sources In accordance from the normal offsite circuit to the with the alternate required offsite circuit. Surveillance Frequency Control Program North Anna Units I and 2 3.8.1-10 Amendments

Attachment 4 (Serial No.15-065)

Marked-up Technical Specifications Bases Pages (For Information Only)

North Anna Power Station Unit 2 Virginia Electric and Power Company (Dominion)

- NUCLEAR DESIGN INFORMATION PORTAL -

AC Sources-Operating B 3.8.1 BASES LCO availability of the required power to shut down the reactor (continued) and maintain it in a safe shutdown condition after an anticipated operational occurrence (AOO) or a postulated DBA.

Qualified offsite circuits include the two 500-34.5 kV transformers and one 230-34.5 kV transformers (collectively referred to as the SRTs) that feed three independent 34.5 kV buses which supply the RSSTs. In addition, there are two 500 kV lines from the switchyard to the Unit 1 and Unit 2 generator step-up transformers and SSTs. These circuits are described in the UFSAR and are part of the licensing basis for the unit.

In addition, the required automatic load sequencing timing relays must be OPERABLE. A "required" load sequencing timing relay is one whose host component is capable of automatically loading onto an emergency bus.

Each independent qualified offsite source must be capable of maintaining rated frequency and voltage, and accepting required loads during an accident, while connected to the ESF buses.

Normally, the qualified offsite sources for the Unit 1 and 2 ESF buses are from the 34.5 kV buses 3, 4, and 5 which supply the RSSTs which feed the transfer buses. RSSTs A and B may be fed from the same 34.5 kV bus, but RSST C must be fed from a different 34.5 kV bus than RSST A and RSST B. The D, E, and F transfer buses supply the onsite electrical power to the four ESF buses for the two units. In addition to the normal alignment, the D and E transfer buses can be tied together Replace via the 4160 V bus OL installed as part of the AAC with modifications.

Insert A E- s 1H is normally fed through the F transfer bus from RSST C. -.. bus 1J is normally fed through the D transfer bus from RSST tSation service bus LB can provide an alternate preferred - for the ESF IH bus, while the ESF 1J has an alternate preferrea-fe-0 from station service bus 2B.

ESF bus 2H is normally fed throue9 E transfer bus from RSST B. In addition, ESF bus 2H can a ls-be fed through E transfer bus from RSST A with breakers 05L1'a I0O5L3 on AAC bus OL closed. ESF bus 2J is normally fed through F transfer bus from RSST C.

(continued)

North Anna Units 1 and 2 .B 3.8. 1-4 Revision

Insert A for page B3.8.1-4 ESF bus 1H is normally fed through the F transfer bus from RSST C. Station service bus 1B can provide an alternatepreferred feed for the bus ESF 1H.

ESF bus 1J is normally fed through the D transfer bus from RSST A. Bus IJ has an alternate preferred feed from station service bus 2B. In addition, ESF bus UJ can be fed through D transfer bus from RSST B with breakers 05L1 and 05L3 on AAC bus OL closed (backup alternate feed).

ESF bus 2H is normally fed through the E transfer bus from RSST B. Station service bus 2C can provide an alternate preferred feed for bus 2H. In addition, ESF bus 2H can be fed through E transfer bus from RSST A with breakers 05L1 and 05L3 on AAC bus OL closed (backup alternate feed).

ESF bus 2J is normally fed through the F transfer bus from RSST C. Station service bus 1A can provide an alternate preferred feed for Bus 2J.

- NUCLEAR DESIGN INFORMATION PORTAL -

AC Sources-Operating B 3.8.1 BASES LCO The two 500 kV lines connecting each unit's main step-up and (continued) SSTs with the switchyard are the remaining qualified sources of offsite (preferred) power.that are available to power ESF buses. For Unit 1, this source is normally available following a unit trip since there is an installed main generator breaker. T,,e,,,fut, S.alu,, ... ,vl buS iB, WIiIch ds.. the alr*r zte- p*1*ferred f... J .- tLL H EE rf L.,

Therefore, station service -,1not

.

ill nrmolbo _affoctd ' For Unit 2, where there is no buses IA and 1B, which installed main generator breaker, 9+,i;. ,;, = bu 20, provide the preferred . Lzdh ds.thea!

t t etttc prefeed fJ d tf ESFr es. 1J, alternate feeds to the 2J and IH ESF buses, Eac EDG must be capable of starting, accelerating to rated respectively, normally will spe d and voltage, and connecting to its respective ESF bus not be affected. on detection of bus undervoltage or degraded voltage. This w 11 be accomplished within 10 seconds. Each EDG must also e capable of accepting required loads within the assumed loading sequence intervals, and continue to operate until offsite power can be restored to the ESF buses. These capabilities are required to be met from a variety of initial conditions such as EDG in standby with the engine hot and EDG station service buses 2B and in standby with the engine at ambient conditions. Additional EDG capabilities must be demonstrated to meet required 2C, which provide the Surveillances.

preferred alternate feeds to ESF buses 1J and 2H, Proper sequencing of loads is a required function for EDG respectively, will automatically OPERABILITY.

transfer to RSST B and RSST In the event of a loss of offsite (preferred) power supply to Cfollowing a unit trip. the emergency bus, the EDG will auto start and re-energize its associated bus. In this configuration the EDG will become inoperable due to the defeat of load sequencing timers. Upon completion of guidance in abnormal procedures for reconfiguration of the affected electrical bus to control loads, TS 3.8.1 Condition K may be exited as sequencing timing relays are no longer required as long as the associated emergency bus is not subsequently paralleled to another bus. The diesel can be considered operable which would allow exiting TS 3.8.1 Conditions B and H and remaining in TS 3.8.1 Condition A.

The other unit's offsite circuit(s) and EDG(s) are required to be OPERABLE to support the SW, MCR/ESGR EVS, Auxiliary Building central exhaust, and CC functions needed for this unit. These functions share components, pump or fans, which are electrically powered from both units.

(continued)

North Anna Units I and 2 B 3.8.1-5 Revi sion

- NUCLEAR DESIGN INFORMATION PORTAL -

AC Sources-Operating B 3.8.1 BASES SURVEILLANCE SR 3.8.1.1 REQUIREMENTS (continued) 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 the preferred or alternate power sources for Unit 1 or tlhe pit!e ,f,

,d p , sau,[e fu, Unit 2, and that appropriate independence of offsite circuits is maintained.

The Surveillance Frequency is based on operating experience, equipment reliability, and plant risk and is controlled under the Surveillance Frequency Control Program.

SR 3.8.1.2 and SR 3.8.1.7 These SRs help to ensure the availability of the standby electrical power supply to mitigate DBAs and transients and to maintain the unit in a safe shutdown condition.

To minimize the wear on moving parts that do not get lubricated when the engine is not running, these SRs are modified by a Note (Note 1 for SR 3.8.1.2) to indicate that all EDG starts for these Surveillances may be preceded by an engine prelube period and followed by a warmup period prior to loading.

For the purposes of SR 3.8.1.2 and SR 3..8.1.7 testing, the EDGs are started from standby conditions. Standby.conditions for an EDG mean that the diesel engine coolant and oil are being continuously circulated, as required, and temperature is being maintained consistent with manufacturer recommendations.

In order to reduce stress and wear on diesel engines, the manufacturer recommends a modified start in which the starting speed of EDGs is limited, warmup is limited to this lower speed, and the EDGs are gradually accelerated to synchronous speed prior to loading. These start procedures are the intent of Note 2.

SR 3.8.1.7 requires that the EDG starts from standby I conditions and achieves required voltage and frequency within 10 seconds. The 10 second start requirement supports the assumptions of the design basis LOCA analysis in the UFSAR, Chapter 15 (Ref. 5).

(continued)

North Anna Units 1 and 2 B 3.8.1-22 Revi sion

TS SR and Basis Mark up for - NUCLEAR DESIGN INFORMATION PORTAL -

DC NA-13-00016 Page 2 of 3 AC Sources-Operating B 3.8.1 BASES SURVEILLANCE SR 3.8.1.5 (continued)

REQUIREMENTS oil system. The Surveillance Frequency is based on operating experience, equipment reliability, and plant risk and is controlled under the Surveillance Frequency Control Program.

This SR is for preventative maintenance. The presence of water does not necessarily represent failure of this SR, provided the accumulated water is removed during the performance of this Surveillance.

SR 3.8.1.6 This Surveillance demonstrates that each required fuel oil transfer pump operates and transfers fuel oil from its associated storage tank to its associated day tank. This is required to support continuous operation of standby power sources. This Surveillance provides assurance that the fuel oil transfer pump is OPERABLE, the fuel oil piping system is intact, the fuel delivery piping is not obstructed, and the controls and control systems for fuel transfer systems are OPERABLE. Only one fuel oil transfer subsystem is required to support an OPERABLE EDG.

The Surveillance Frequency is based on operating experience, equipment reliability, and plant risk and is controlled under the Surveillance Frequency Control Program.

SR 3.8.1.7 See SR 3.8.1.2.

SR 3.8.1.8 Transfer of each 4.16 kV ESF bus power supply from the normal offsite circuit to the alternate offsite circuit demonstrates the OPERABILITY of the alternate circuit distribution network to power the shutdown loads-fr-Umit I e4y: The Surveillance Frequency is based on operating experience, equipment reliability, and plant risk and is controlled under the Surveillance Frequency Control Program.

(continued)

North Anna Units 1 and 2 B 3.8. 1-25 Revision

TS SR and Basis Mark up for - NUCLEAR DESIGN INFORMATION PORTAL -

DC NA-13-00016 Page 3 of 3 AC Sources-Operating B 3.8.1 BASES SURVEILLANCE SR 3.8.1.8 (continued)

REQUIREMENTS T:hic SA i: madifi@d by t.;z PNzte. Note 1 States thet the. SR is app; Wik I to Unit- 1 only.1 4hz 93 4r. Rot Opp!lieable to Unit a beeatuzz it dees met haye aii aolite,,t offr 3 b Fee For This SR is modified -the enjergornzy buges. ;he reasen far Noete 2 4s that, during operation with the reactor critical, performance of this SR bya Note. The could cause perturbations to the electrical distribution reason for the Note systems that could challenge continued steady state is that, during operation and, as a result, unit safety systems. This restriction from normally performing the Surveillance in MODE 1 or 2 is further amplified to allow the Surveillance to be performed for the purpose of reestablishing OPERABILITY (e.g., post work testing following corrective maintenance, corrective modification, deficient or incomplete surveillance testing, and other unanticipated OPERABILITY concerns) provided an assessment determines unit safety is maintained or enhanced. This assessment shall, as a minimum, consider the potential outcomes and transients associated with a failed Surveillance, a successful Surveillance, and a perturbation of the offsite or onsite system when they are tied together or operated independently for the Surveillance; as well as the operator procedures available to cope with these outcomes. These shall be measured against the avoided risk of a unit shutdown and startup to determine that unit safety is maintained or enhanced when the Surveillance is performed in MODE 1 or 2.

Risk insights or deterministic methods may be used for this assessment.

SR 3.8.1.9 Each EDG is provided with an engine overspeed trip to prevent damage to the engine. Recovery from the transient caused by the loss of a large load could cause diesel engine overspeed, which, if excessive, might result in a trip of the engine.

This Surveillance demonstrates the EDG load response characteristics and capability to reject the largest single load without exceeding predetermined voltage and frequency and while maintaining a specified margin to the overspeed trip. For this unit, the single load for each EDG is 610 kW.

This Surveillance may be accomplished by:

a. Tripping the EDG output breaker with the EDG carrying greater than or equal to its associated single largest post-accident load while paralleled to offsite power, or while solely supplying the bus; or (continued)

North Anna Units 1 and 2 B 3.8. 1-26 Revi s~ion

- NUCLEAR DESIGN INFORMATION PORTAL -

AC Sources-Shutdown 8 3.8.2 BASES LCO powered from offsite power. An OPERABLE EDG, associated with (continued) the distribution system trains required to be OPERABLE by LCO 3.8.10, ensures a diverse power source is available to provide electrical power support, assuming a loss of the offsite circuit. Together, OPERABILITY of the required offsite circuit and EDG ensures the availability of sufficient AC sources to operate the unit in a safe manner and to mitigate the consequences of postulated events during shutdown (e.g., fuel handling accidents involving handling recently irradiated fuel).

The qualified offsite circuit must be capable of maintaining rated frequency and voltage, and accepting required loads during an accident, while connected to the Engineered Safety Feature (ESF) bus(es). Qualified offsite circuits are those that are described in the UFSAR and are part of the licensing basis for the unit.

Offsite circuits consist of 34.5 kV buses 3, 4, and 5 supplying the Reserve Station Service Transformer(s) (RSST) which feed the transfer buses. The D, E, and F transfer buses supply the onsite electrical power to the four emergency buses for the two units. Unit 1 emergency bus H is fed through the F transfer bus from the C RSST. Unit 1 emergency bus J is fed through the D transfer bus from the A RSST.

Unit 2 station service bus 2C can Unit 1 station service bus 1B can be an alternate feed for be an alternate feed for Unit 2 H Unit 1 H emergency bus, while Unit 1 J bus may be fed from emergency bus, while Unit 2 J Unit 2 station service bus 28. Unit 2 emergency bus H is fed bus may be fed from Unit I through the E transfer bus from the B RSST. Unit 2 emergency station service bus IA. In bus J is fed through the F transfer bus from the C RSST-,The RSSTs can be fed by any 34.5 kV bus (3, 4, or 5) provided addition, E transfer bus can be a RSSTs A and B are fed from a different 34.5 kV bus than backup alternate feed to Unit 2 H RSST C.

bus (fed from RSST A through the D transfer bus and OL bus). The EDG must be capable of starting, accelerating to rated speed and voltage, and connecting to its respective ESF bus on detection of bus undervoltage or degraded voltage. The EDG must be capable of accepting required loads within the assumed loading sequence intervals, and continue to operate until offsite power can be restored to the ESF bus. These capabilities are required to be met from a variety of initial conditions such as EDG in standby with the engine hot and the EDG in standby at ambient conditions.

Proper sequencing of loads is a required function for EDG OPERABILITY.

(continued)

North Anna Units I and 2 B 3.8.2-3 Revision

- NUCLEAR DESIGN INFORMATION PORTAL -

Diesel Fuel Oil and Starting Air B 3.8.3 BASES ACTIONS In addition, the following compensatory measure will be (continued) established and implemented prior to entry and while in the extended AOT:

1. The condition of the offsite power supply and switchyard will be evaluated prior to entering the extended EDG UFOST CT for elective maintenance.

2. Determine acceptable grid conditions for entering an extended EDG UFOST CT to perform elective maintenance.

An extended EDG.UFOST CT will not be.entered to perform elective maintenance when grid stress conditions are high.

3. No elective maintenance will be scheduled in the switchyard that would challenge offsite power availability and no elective maintenance will be scheduled on the main, auxiliary [station service], or startup [reserve station service] transformers associated with the unit during the proposed extended EDG UFOST CT.

4. The system dispatcher will be contacted once per day to ensure no significant grid perturbations are expected during the extended EDG UFOST CT.

5. The turbine-driven AFW pump will not be removed from service for planned maintenance activities during the extended EDG UFOST CT.

6. Operating crews will be briefed on the EDG UFOST work plan and procedural actions regarding:

LOOP and Station Black Out 4 kV 3CftuUtld bLzo ,u-VLI [UnI Ei2 L ,,eMULMInY buN Reactor Coolant System bleed and feed

7. Weather conditions will be evaluated prior to entering the extended EDG CT for elective maintenance. An extended EDG UFOST CT will not be entered for elective maintenance purposes if official weather forecasts are predicting severe conditions (tornado or thunderstorm warnings).'

8. No elective maintenance will be scheduled for the plant DC system.

(continued)

North Anna Units 1 and 2 B 3.8.3-5 Revi si on

- NUCLEAR DESIGN INFORMATION PORTAL -

4 Distribution Systems-Operating B 3.8.9 B 3.8 ELECTRICAL POWER SYSTEMS B 3.8.9 Distribution Systems-Operating BASES BACKGROUND The onsite Class 1E AC, DC, and AC vital bus electrical power distribution systems are divided by train into two redundant and independent AC, DC, and AC vital bus electrical power land Unit.2 each have d-.istributio subsyst,,,s.

The electrical power subsystem for each train consists of a primar ineered Safety Feature (ESF) 4.16 kV bus and secondary 480 ses and load centers. Each 4.16 kV ESF bus has at least one sep e and independent offsite source of power as well as a dedica nsite emergency diesel generator (EIG) source. Unit T-&a a normal offsite source and an alternate offsite source. Transfer to the alternate offsite source is a manual operation. brit 2 hn *= noal

-ffsit ....... , andi..

-- eitzrmt zr;. In the event of a loss of offsite power, the EDGs for the affected buses will start and load. The EDGs for Unit will continue to run until (a) the safety bus is transferred to the alternate offsite source, or (b) the normal offsite source is restored. 4e U-it 2 ED: %;il ..... tie.u t rum. . until -

ma; effsid* ur. i ........ ed If offsite sources are unavailable, the onsite EDG supplies power to the 4.16 kV ESF bus. Control power for the 4.16 kV breakers is supplied from the Class 1E batteries. Additional description of this system may be found in the Bases for LCO 3.8.1, "AC Sources-Operating," and the Bases for LCO 3.8.4, "DC Sources-Operating."

The secondary AC electrical power distribution subsystem for each train includes the safety related buses and load centers shown in Table B 3.8.9-1.

The 120 VAC vital buses are arranged in two load groups per train and are normally powered from the inverters. The alternate power supply for the vital buses are constant voltage source transformers powered from the same train as the associated inverter, and its use is governed by LCO 3.8.7, "Inverters-Operating." Each constant voltage source transformer is powered from a Class 1E AC bus.

There are two independent 125 VDC electrical power distribution subsystems for each train.

(continued)

North Anna Units I and 2 B 3.8.9-1 Revi sion