ML16013A444

From kanterella
Jump to navigation Jump to search

(NAPS) - Issuance of Amendment for Changes to Technical Specification (TS) 3.8.1 - AC Sources, Operating Revised Surveillance Requirement
ML16013A444
Person / Time
Site: North Anna Dominion icon.png
Issue date: 02/22/2016
From: V Sreenivas
Plant Licensing Branch II
To: Heacock D
Virginia Electric & Power Co (VEPCO)
Sreenivas V, NRR/DORL/LPLII-1
References
CAC MF6261
Download: ML16013A444 (17)
v • d • e


Text

. -~-

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 R:bru3I:y 22, 2016 Mr. David A. Heacock President and Chief Nuclear Officer Virginia Electric and Power Company 5000 Dominion Boulevard Glen Allen, VA 23060-6711

SUBJECT:

NORTH ANNA POWER STATION, UNIT NO. 2 - ISSUANCE OF AMENDMENT REGARDING CHANGES TO TECHNICAL SPECIFICATION 3.8.1 - "AC SOURCES-OPERATING" REVISED SURVEILLANCE REQUIREMENT (CAC NO. MF6261)

Dear Mr. Heacock:

The U.S. Nuclear Regulatory Commission has issued the enclosed Amendment No. 260 to Renewed Facility Operating License No. NPF-7 for the North Anna Power Station, Unit 2. This amendment revises Technical Specification 3.8.1, "AC Sources-Operating," in response to your application dated May 22, 2015, and as supplemented by letter dated October 13, 2015.

The amendment revised Surveillance Requirement 3.8.1.8 to remove the limitation in Note 1 that states that the surveillance is only applicable to Unit 1. The revised Surveillance Requirement 3.8.1.8 is applicable to both units.

A copy of our related safety evaluation is also enclosed. The Notice of Issuance will be included in the Commission's biweekly Federal Register notice.

Sincerely,

r. V. Sreenivas, Project Manager Plant Licensing Branch 11-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-339

Enclosures:

1. Amendment No. 260 to NPF-7
2. Safety Evaluation cc w/encls: Distribution via Listserv

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 VIRGINIA ELECTRIC AND POWER COMPANY DOCKET NO. 50-339 NORTH ANNA POWER STATION, UNIT NO. 2 AMENDMENT TO RENEWED FACILITY OPERATING LICENSE Amendment No. 260 Renewed License No. NPF-7

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

A. The application for amendment by Virginia Electric and Power Company et al.,

(the licensee) dated May 22, 2015, as supplemented by letter dated October 13, 2015, complies with the standards and requirements of the Atomic Energy Act of 1954, as amended (the Act), and the Commission's rules and regulations set forth in 10 CFR Chapter I; B. The facility will operate in conformity with the application, the provisions of the Act, and the rules and regulations of the Commission; C. There is reasonable assurance (i) that the activities authorized by this amendment can be conducted without endangering the health and safety of the public, and (ii) that such activities will be conducted in compliance with the Commission's regulations; D. The issuance of this amendment will not be inimical to the common defense and security or to the health and safety of the public; and E. The issuance of this amendment is in accordance with 10 CFR Part 51 of the Commission's regulations and all applicable requirements have been satisfied.

Enclosure 1

2. Accordingly, the license is amended by changes to paragraph 2.C(2) of Renewed Facility Operating License No. NPF-7, as indicated in the attachment to this license amendment, and is hereby amended to read as follows:

(2) Technical Specifications The Technical Specifications contained in Appendix A, as revised through Amendment No. 260, are hereby incorporated in the renewed license. The licensee shall operate the facility in accordance with the Technical Specifications.

3. This license amendment is effective as of its date of issuance and shall be implemented 1

within 30 days of issuance.

  • FOR THE NUCLEAR REGULATORY COMMISSION

~~A7 Michael T. Markley, Chief Plant Licensing Branch 2-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation

Attachment:

Changes to License No. NPF-7 Date of Issuance: FEbnary 22, 2016

ATTACHMENT TO LICENSE AMENDMENT NO. 260 RENEWED FACILITY OPERATING LICENSE NO. NPF-7 DOCKET NO. 50-339 Replace the following pages of the Licenses with the enclosed pages as indicated. The revised pages are identified by amendment number and contain vertical lines indicating the areas of change.

Remove License Pages License Pages License No. NPF-7, page 3 License No. NPF-7, page 3 TS TS Page 3.8.1-10 Page 3.8.1-1 O

(3) Pursuant to the Act and 10 CFR Parts 30, 40, and 70, VEPCO to receive, possess, and use at any time any byproduct, source, and special nuclear material as sealed neutron sources for reactor startup, sealed sources for reactor instrumentation and radiation monitoring equipment calibration, and as fission detectors in amounts as required; (4) Pursuant to the Act and 10 CFR Parts 30, 40, and 70, VEPCO to receive, possess, and use in amounts as required any byproduct, source, or special nuclear material, without restriction to chemical or physical form, for sample analysis or instrument calibration or associated with radioactive apparatus or components; and (5) Pursuant to the Act and 10 CFR Parts 30, 40, and 70, VEPCO to possess, but not separate, such byproduct and special nuclear materials as may be produced by the operation of the facility.

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

(1) Maximum Power Level VEPCO is authorized to operate the facility at steady state reactor core power levels not in excess of 2940 megawatts (thermal).

(2) Technical Specifications The Technical Specifications contained in Appendix A, as revised through Amendment No. 260, are hereby incorporated in the renewed license. The licensee shall operate the facility in accordance with the Technical Specifications.

(3) Additional Conditions The matters specified in the following conditions shall be completed to the satisfaction of the Commission within the stated time periods following the issuance of the condition or within the operational restrictions indicated. The removal of these conditions shall be made by an amendment to the renewed license supported by a favorable evaluation by the Commission:

a. If VEPCO plans to remove or to make significant changes in the normal operation of equipment that controls the amount of radioactivity in effluents from the North Anna Power Station, the NORTH ANNA - UNIT 2 Renewed License No. NPF-7 Amendment No. 260

AC Sources-Operating 3.8.1 SURVEILLANCE REQUIREMENTS SURVEILLANCE FREQUENCY SR 3.8.1. 7 -~-----------------NOTE----------------

Al l EOG starts may be preceded by an engine prelube period.

Verify each required EOG starts from In accordance standby condition and achieves i'li th the Surveillance

a. Ins 10 seconds, voltage~ 3960 V and Frequency Centro l frequency ~ 59.5 Hz; and Program
b. Steady state voltage~ 3740 V and s 4580 V, and frequency~ 59.5 Hz and s 60.5 Hz.

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

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 manua 1 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 Amendments 262 arrl 260 I

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO. 260 TO RENEWED FACILITY OPERATING LICENSE NPF-7 VIRGINIA ELECTRIC AND POWER COMPANY NORTH ANNA POWER STATION UNIT NO. 2 DOCKET NO. 50-339

1.0 INTRODUCTION

By application dated May 22, 2015 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML15147A029), Virginia Electric and Power Company (the licensee, Dominion) submitted a request for amendment to the Technical Specifications (TS) for North Anna Power Station (NAPS) Unit 2. The license amendment request (LAR) proposed changes to TS 3.8.1, "AC Sources-Operating." Specifically, the proposed change deletes Note 1 to Surveillance Requirement (SR) 3.8.1.8, which requires verification of the capability to manually transfer Unit 1 emergency safety features (ESF) 4.16 kilovolt (kV) alternating current (AC) power sources from the normal offsite circuit to an alternate offsite circuit. The amendment revises SR 3.8.1.8 to remove the limitation in Note 1 that states that the surveillance is only applicable to Unit 1. Revised SR 3.8.1.8 is applicable to both Units.

The U.S. Nuclear Regulatory Commission (NRC) staff requested additional information (RAI) by letter dated September 9, 2015 (ADAMS Accession No. ML15257A299). The licensee submitted responses to the staff's' RAI by letter dated October 13, 2015 (ADAMS Accession No. ML15292A214). The supplemental letter provided additional information that clarified the application, but did not change the scope of the application as originally noticed in the Federal Register (FR) on July 21, 2015 (80 FR 43131 ).

2.0 REGULATORY EVALUATION

2.1 System Description In its letter dated May 22, 2015, the licensee provided the following system description:

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 servipe 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

-2 ~

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 emergency buses are arranged in two separate systems designated Hand 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 off site 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 off site 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.

2.2 Proposed Change The proposed revision to SR 3.8.1.8 would delete the applicability of the first note to Unit 1. The text that has to be deleted is shown below:

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

1. This Surveillance is only applicable to Unit 1.

a,. 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 offsit.e circuit.

2.3 Applicable Regulatory Requirements The NRC staff applied the below listed regulatory requirements in its review of this application.

The NRC staff notes however, that North Anna Power Statior:i, Units 1 and 2 was licensed for construction was issued construction permit Nos. CPPR-77 and CPPR-78 dated February 1971, based on the station design being in conformance with the General Design Criteria for Nuclear Power Plants (GDC), published in 1966. Chapter 3 of North Anna Updated Final Safety Analysis Report (UFSAR) provides general design criteria, and explanations of how the ,

structures, systems, and components meet the intent of the~ GDC.

UFSAR Chapter 3, "Design Criteria - Structure, Components, Equipment, and Systems," of tfile NAPS UFSAR provides the AEC General Design Criteria for the plant. Below is the list of the AEC Criteria applicable to the review of this LAR.

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

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

AEC 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.

10 CFR 50.36, "Technical specifications," establish the requirements related to the content of the TS. Pursuant to 10 CFR 50.36(c) TSs include: (1) safety limits, limiting safety system settings, and limiting control settings; (2) limiting conditions for operations (LCOs); (3) surveillance requirements (SRs); (4) design features; and (5) administrative controls. The proposed changes to TS, discussed in this amendment, are within the SRs category.

10 CFR 50.65, "Requirements for monitoring the effectiveness of maintenance at nuclear power plants," states that, "adjustments shall be made where necessary to ensure that the objective of preventing failures of structures, systems, and components through maintenance is appropriately balanced against the objective of minimizing unavailability of structures, systems, and components due to monitoring or preventive maintenance."

Regulatory Guide 1.32, "Criteria for Class 1E Electric Systems for Nuclear Generating Stations" (Revisions 0), describes a method acceptable to the NRC staff for complying with the NRC's regulations for the design, operation, and testing of electric power systems in nuclear power plants.

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

3.0 TECHNICAL EVALUATION

The NRC staff notes that at NAPS, Unit 1, alternate supplies (bus ties) from the Station Service Bus to Emergency Bus, can be used to provide an alternate offsite AC circuit. However, Unit 2 does not have Station Service Bus to Emergency Bus ties breakers that provide an alternate offsite AC circuit to each emergency bus similar to Unit 1. Instead, the Emergency Buses (2H and 2J) may be interconnected by a breaker that is normally removed from its cubicle located on Bus 2H. The breaker on Bus 2H is under strict operational supervision and is provided for maintenance purposes.

The licensee plans to implement a plant modification to install an alternate offsite AC circuit to each Unit 2 Emergency Bus 2H and 2J and permanently remove the existing manual cross-tie between buses 2H and 2J. The proposed changes are required because currently 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. Currently, SR 3.8.1.8, Note 1, states that the surveillance is only applicable to Unit 1. The plant modifications to provide an alternate path to offsite circuits will require testing in accordance with TS SR 3.8.1.8, and, therefore, the limitation in Note 1 will no longer be necessary and Dominion proposes that it be removed.

In Attachment 1 to letter dated May 22, 2015, the licensee provided a discussion of the proposed changes to TS Section 4.0, "Technical Analysis and Safety Considerations," which provides the design and analysis description of the proposed changes to TS SR 3.8.1.8.

The licensee stated that:

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."

This normally open cross-tie connection will be designated as alternate required offsite circuit.

The licensee also stated that:

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 1E structures, systems, 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, (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.

By letter dated September 9, 2015, the NRC staff submitted a RAI to the licensee requesting a description and drawings of the proposed changes in order to remove Note 1 from SR 3.8.1.8.

In its letter dated October 13, 2015, the licensee responded and provided drawings that illustrate the proposed Unit 2 bus preferred alternate supplies (bus ties) and backup alternate supply. The licensee also provided a tabulated list of the proposed configurations of the plant during all modes of operation with the new Unit 2 Bus ties installed.

The NRC staff noted since Generator Output Breaker is not planned for the Unit 2 main generator, the RSSTs or alternate offsite power sources may be used to power the auxiliaries.

During this period, the SSTs and the RSSTs or alternate paths are paralleled prior to transfer to maintain uninterrupted power to the plant busses. In response to RAl-4, the licensee stated, that:

The transfer of the auxiliary busses from the SSTs to the RSSTs will occur in the same manner that it presently does after the Unit 1 preferred alternate offsite power supplies are utilized. During the manual transfer, for a short duration, the SSTs and RSSTs are paralleled. During this short period of time it is plausible that the circuit breaker interrupting ratings at the 2J or 2H buses are exceeded. As stated in IEEE Std 666-2007 it is an acceptable practice to design for the single-source condition if the duration of parallel operation is short. The proposed manual transfer to the preferred alternative feed is controlled by procedures and occurs in a short amount of time, thus meeting this practice. There are no other electrical transients expected during the manual transfer.

The system conditions following the transfer have been previously evaluated and no short circuit or load flow concerns have been determined to exist with the alternate offsite power supplies being utilized.

The licensee confirmed that fault conditions or no other electrical transients expected during this period. The NRC staff finds the proposed configuration is acceptable based on the requirements of AEC criterion 17, as it relates to adequate independency, redundancy, and ability of offsite power systems to perform their intended safety functions.

In its response to RAl-2, the licensee stated, in part, that the proposed Unit 2 alternate offsite power supply alignments have been evaluated for conformance with GDC 17. To assess the effects on auxiliary power system voltages, bounding analyses were performed using the ETAP computer program with the proposed modifications implemented. In its letter dated October 13, 2015, the licensee concluded that, For evaluation of the new bus preferred alternate offsite power supplies, 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 Cat 30 seconds), while emergency Bus 2J was loaded on Station Service Bus IA. The second analysis modeled a Unit 2 trip event with the preferred alternate offsite power supplies in place 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 preferred alternate offsite power supplies to be used during these bounding scenarios and the proposed new paths are sufficient to satisfy GDC 17 safety function requirements.

The NRC staff reviewed the summary of plant bus voltages at the onset of the event, during load sequencing and steady state conditions. The NRC staff considers the degraded voltage relay (DVR) setpoint as the limiting minimum voltage acceptable for equipment starting and operation. In its letter dated October 13, 2015, the licensee has stated that "during the load sequencing on to the offsite power sources, there are a few instances where bus voltages drop below the DVR setpoint but recover within the allowable time delay (6 seconds)."

The NRC staff has evaluated the summary of safety bus voltages provided by the licensee.

Based on the AEC Criterion 17, the NRC staff finds the response provided by the licensee is acceptable.

In its letter dated May 22, 2015, the licensee stated that UFSAR Section 8.3.1.1.1 describes a load shedding scheme that 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

[Electrical Transient Analyzer Program] analysis, no additional load shedding scheme is necessary. However, the licensee has proposed restrictions that will be imposed when the new bus cross-ties are placed in service, or when Bus OL is used to interconnect plant transfer buses." The proposed restrictions are similar to the existing restrictions implemented for the Unit 1 cross-ties and include limitations on:

  • 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).
  • 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.
  • 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.

  • 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.
1. Large non-safety related motor starts. 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 LAR provides a summary of the loads that are proposed to be inhibited or are already inhibited from auto-starting based on the breaker configuration.
2. Total continuous current flow of 3000 amps in station services busses 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).

The restrictions and limitations are related to non-safety related loads and are part of the existing load management scheme. Management of non-essential loads provides assurance that the equipment required for safe shutdown of the plant has adequate voltage. The NRC staff, therefore, concludes that the limitations are acceptable for the proposed configurations for Unit 2 operation.

The NRC staff also requested information about mega-volts-amps reactive (MVAR) power limitations imposed on the Main Generator when Bus 2H or 2J is connected to the corresponding Bus 2C or 1A respectively. In its letter dated October 13, 2015, the licensee stated that the MVAR output limitation for Unit 1 or 2 with the preferred alternate offsite power supplies in place is "added in order to ensure adequate Bus 2J and Bus 2H voltage in accordance with GDC 17." Reactive power limitations provide assurance that the nuclear power plant is not critical for supporting transmission system voltages, such that post unit trip, the loss of power from the plant does not result in degraded grid conditions resulting in inadequate voltages at the plant safety busses. The licensee's procedural controls for reactive power generation ensure that plant busses have adequate voltages. The NRC staff finds these controls acceptable for maintaining safety bus voltages post unit trip meet AEC Criterion 17 and is, therefore, acceptable.

The intent of the proposed plant modification is to provide flexibility during all modes of plant operation to ensure that two qualified offsite power sources are available for compliance with the licensing basis. The NRC staff requested clarification on the paths that will be tested after the plant modifications have been implemented. In its letter dated October 13, 2015, the licensee stated that the paths that will be periodically tested are:

1. The preferred alternate path from Unit 1 Station Service Bus 1A to Unit 2 Emergency Bus 2J,
2. The preferred alternate path from Unit 2 Station Service Bus 2C to Unit 2 Emergency Bus 2H, and
3. Backup alternate path from RSST A to "D" Transfer bus through OL bus to "E" Transfer bus to Emergency Bus 2H.

The licensee also stated that, "All tests are performed per procedures which prevent alignments that are not in accordance with GDC 17."

The NRC staff reviewed the licensee proposed paths that will be periodically tested. The NRC staff finds the licensee's response maintains compliance with AEC 18 requirements and is, therefore, acceptable. The proposed modifications will allow appropriate inspection, testing and maintenance of the RSST, and alternated preferred sources.

Because of the interconnections between Unit 1 and 2 Normal Bus 1A with Emergency Bus 2J, the NRC staff requested the licensee to provide a summary of the analysis performed to demonstrate that degraded or fault conditions in one path will not adversely impact safe shutdown of dual units. In its letter dated October 13, 2015, the licensee stated, that, "With the new Unit 2 preferred alternate offsite power supplies utilized, in the event of an accident on either unit, the two emergency busses on each unit continue to be supplied by a separate RSST or SST. Hence, the addition of the new Unit 2 preferred alternate offsite power supplies does not add an additional failure method nor does it impair the safety functions or the ability to safely shutdown or cooldown either unit." The NRC staff finds this meets the AEC criterion 5 and is, therefore, acceptable.

UFSAR Chapter 8, Section 8.3.1.1.2.2, "Compliance with IEEE Criteria," states that, "In accordance with IEEE Standard 308, the station service power system and its components are designed to operate during and after a design-basis event, retain its safety features, and keep its parameters within their specified limits. The safety-related systems are redundant systems so that a loss of one will not endanger personnel or structures." Station service power systems are designed in accordance with IEEE Standard 308-1971, "IEEE Standard Criteria for Class IE Electric Systems for Nuclear Power Generating Stations." This Standard is endorsed in Regulatory Guide 1.32. Appendix 3A, "Compliances with Safety Guides," of NAPS UFSAR, Section 3A.28 states that, "the design is in accordance with the staff position in Regulatory Guide 1.32." In addition, NRC staff reviewed IEEE Standard 666-2007 "IEEE Design Guide for Electric Power Service Systems for Generating Stations" as guidance for design and operation of station service systems that supply electric power to auxiliary loads for electric power generating stations. Section 4.6 of this standard discusses auxiliary bus transfer schemes. For manual transfers, where two (or more) power sources may be paralleled momentarily, the major concern is fault current due to different sources. The standard states in part, that switchgear design for the single-source condition is acceptable if the duration of parallel operation is short.

The system faults during the short interval that the NAPS busses are paralleled during manual transfer is minimal and, therefore, the NRC staff finds that the design rating of circuit breakers for 2J and 2H busses is acceptable. Based on these evaluations, the NRC staff concludes the SSTs and RSSTs that are paralleled for a short duration during the manual transfer is acceptable and meets the requirements of AEC Criterion 17 that onsite electric power supplies have sufficient independence, redundancy, and testability to perform their safety functions and that the probability of loss of power is minimized.

In its letter dated October 13, 2015, the licensee stated, that:

Each unit at North Anna Power Station has redundant emergency buses which are able to safely shutdown each unit. An electrical fault or degraded condition at the points common to both units in the system are detected by plant specific undervoltage relays at

the Emergency buses. The Emergency bus relaying then separates the impacted bus (es) from the offsite supply and starts the associated diesel generators to provide emergency bus power. All redundant emergency busses would have power, either offsite power or diesel power.

The licensee has concluded that each unit can be safely shutdown using the onsite or offsite power system. The NRC staff evaluated the proposed configurations of offsite power system required for dual unit shutdown and finds that the two emergency busses on each unit will be supplied by a separate RSST or SST source. The failure in one source on one unit will not adversely impact safe shutdown capability of the second unit. The licensee has demonstrated that this will not significantly impair their ability to perform their safety functions including, in the event of an accident in one unit, an orderly shutdown and cooldown of the other unit. The NRC staff has concluded that the proposed plant modification and plant configurations will maintain compliance with AEC 5 requirements.

4.0 NRC STAFF CONCLUSION The NRC staff has reviewed the licensee's proposed changes to TS 3.8.1, SR 3.8.1.8, as delineated in its letter dated May 22, 2015, and supplemental information provided in letter dated October 13, 2015. The NRC staff finds that the proposed amendment to TS 3.8.1 to delete Note 1 to SR 3.8.1.8, to be acceptable once the plant modifications are implemented.

SR 3.8.1.8 will now require verification of the capability to manually transfer Unit 1 and Unit 2 ESF power sources from the normal offsite circuit to an alternate offsite circuit. The licensee has addressed the adequacy of alternate configurations to support dual unit shutdown and capability to test the configurations. Therefore the staff has determined that SR 3.8.1.8, as revised, will continue to meet 10 CFR 50.36(c)(3).

The NRC staff concludes that there is reasonable assurance that the equipment required to safely shutdown the operating unit(s) and mitigate the effects of a design basis accident will remain capable of performing the safety function when the alternate preferred power source is connected to the Class 1E buses of the operating unit(s). When one normal preferred power source circuit through RSST or SST is not available, the safety buses of two operating units have two independent offsite power sources and meet the requirements of AEC 17 and the two NAPS units continue to meet with AEC 5, AEC 18, and 10 CFR 50.36.

5.0 STATE CONSULTATION

In accordance with the Commission's regulations, officials from the Commonwealth of Virginia were notified of the proposed issuance of the amendment. The NRC did not receive any comments from the Commonwealth officials.

6.0 PUBLIC COMMENTS On July 21, 2015, the NRC staff published a "Notice of Consideration of Issuance of Amendments to Facility Operating Licenses, Proposed No Significant Hazards Consideration Determination, and Opportunity for a Hearing," in the Federal Register associated with the proposed amendment request (80 FR 43131 ). In accordance with the requirements in 10 CFR 50.91, "Notice for public comment; State consultation," the notice provided a 30-day period for

public comment on the proposed no significant hazards consideration (NSHC) determination.

The 30-day comment period ended on August 20, 2015. Two public comments were received on October 8, 2015 regarding the proposed amendment. First comments was subject to the region of acceptable operation and temperature limitations for Surry and North Anna reactor coolant system heatup and cooldown curves. The second comment was questioning the licensee on their delay in submitting this LAR. The NRC staff review concluded that the first comment is not related to the proposed surveillance limitation change in the amendment request and the second comment regarding this amendment is related to licensee request of developing a plant modification, which would now require to eliminate current surveillance limitation requirement. These comments did not affect the conclusions in the NSHC determination as published in the Federal Register. Therefore, no changes were made to "AC Sources-Operating," revised surveillance requirement approval as described in this safety evaluation.

7.0 ENVIRONMENTAL CONSIDERATION

The amendment change requirements with respect to installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20 and changes surveillance requirements. The NRC staff has determined that the amendment involves no significant increase in the amounts, and no significant change in~ the types, of any effluents that may be released offsite, and that there is no significant increase in individual or cumulative occupational radiation exposure. The Commission has previously issued a proposed finding that the amendments involve no significant hazards consideration, and there has been no public comment on such finding (80 FR 43131 ). Accordingly, the amendments meet the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9). Pursuant to 10 CFR 51.22(b),

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

8.0 CONCLUSION

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

Principal Contributor: J. Cintron, NRR Date of issuance: February 22, 2016

ML16013A444 OFFICE LPL2-1/PM LPL2-1/LA DE/EE EB/BC DSS/STSB/BC NAME VSreenivas SFigueroa JZimmerman RElliott DATE 02/09/16 02/08/16 01/20/16 02/08/16 OFFICE OGC/NLO LPL2-1/BC LPL2-1/PM NAME CKanatas MMarkley VSreenivas DATE 02/03/16 02/22/16 02/22/16

Retrieved from "https://kanterella.com/w/index.php?title=ML16013A444&oldid=2445597"