ML20082L815

Application for Amends to Licenses NPF-4 & NPF-7,changing TS Table 3.3-4 Re Station Blackout,Loss of Voltage & Undervoltage Trip Setpoints & Allowable Values Located in Spec 3.3.2 on ESFAS Instrumentation Trip Setpoints

ML20082L815
Person / Time
Site:	North Anna
Issue date:	08/29/1991
From:	Stewart W VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
Shared Package
ML20082L817	List: ML20082L815 ML20082L824
References
91-506, NUDOCS 9109040379
Download: ML20082L815 (9)

Text

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VIHOINIA Eu:criac Ann l'own:n Co.suwxy Ricusioun,Waaisir unu ci August 29, 1991 l~

U.S. Nuclear Regulatory Commission Serial No.:

91-506 Attention: Document Control Desk NAPS /MJB/TAH:R2 Washington, D.C. 20555 Docket Nos : 50-338 50-339

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License Nos.: NPF-4 NPF-7 Gentlemen:

VIRGINIA ELECTRIC' AND PUWER COMPANY NORTH ANNA POWER STATION UNITS 1 AND 2

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PROPOSED TECHNICAL SPECIFICATION CHANGE TABLE 3.3-4. STATION BLACKOUT. LOSS OF VOLTAGE. AND l

DEGR ADED VOLTAGE. TRIP SETPOINTS AND ALLOWABLE VALUES

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Pursuant to 10 CFR 50.90, Virginia Electric and Power Company requests amendments, in the form of changes to Technical Specifications, to Operating Licenses Number NPF-4 and NPF-7 for North Anna Power Statio. Units 1 and 2.

These amendments will revise the Station Blackout, Loss of Voltage and Undervoltage trip setpoints and allowable values located in Specification 3.3.2, Table 3.3 4, Engineered Safety Feature Actuation System instrumentation Trip Setpoints.

The proposed change for Specification 3/4.3.2 Table 3.3-4 Item 6.e, Station Blackout, is administrative in nature. The Trip Setpoint and Allowable Value are currendy listed i

I to a percentage of the transfer bus voltage. This will be changed to an actual voltage.

Tut,.roposed change for Spacification 3/4.3.2 Table 3.3 4 Items 7,a and 7.b, Loss of i

V),tage and Degraded Voltage, removes the tolerance values associated c'ith the Allowable Values listed in Technical Specification 3/4.3.2 Table 3.3-4 Items 7.a and l

7.b, Loss of Voltage and Degraded Voltage. These changes are intended to promote l

l clarity and ease of t.se of the specification.

In addition, the Trip Setpoints and Allowable Values for the Loss of Voltage and Degraded Voltage specifications (items v

7.a and 7.b of Table 3.3-4) have been revised.

i This request has been reviewed by the Station Nuclear Safety and Operating

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L Committee and the Management Safety Review Committee. It has been determined that this request does not involve an unrevieNd safety question as defined in 10CFR50.59, or a significant hazards consideration as defined in 10CFR50.92. The changes and the determination of no significant hazards are presented in the

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proposed final copy of the specification, a detailed discussion of the proposed Attachment.

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'9109040379 91o829 DR AD7CK 05000338

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Dochet Nos.: 50-338&339 serial No.:

91 506 Technical Specification 3.3.2.1-requires ESFAS surveillance testing to be performed every 18 months. Establishing new setpoints for the 4160 volt emergency bus undervoltage trip setpoints and the performance of associated post maintenance testing is not desired during power operations because of the increased possibility of inadvertent disconnection of the emergency buses from the preferred off site power l

sources.

Therefore, we request that the amendments become effective with their issuance, with implementation required prior to restart after each. unit's next refueling outage.

Currently, Unit 1 is scheduled for refueling outage from April 18,1992 through June 30,1992, and Unit 2 from February 1,1992 through April 14,1992.

Please contact us if you have any questions or require additionalinformation.

Very truly yours,

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&W-

/ W. L Stewart [#D Senior Vice President - Nuclear

Attachment:

Proposed License Amendment for North Anna Units 1 and 2.

i pc: U.S. Nuclear Regulatory Commission Region il 101 Marietta Street, N.W.

Suite 2900 Atlanta, Georgia 30323 Mr. M. S. Lesser L

NRC Senior Resident inspector l

North Anna Power Station Commissioner Department of Health Room 400

- 109 Governor Streel L

Richmond, Virginia 23219 l

i COMMONWEALTH OF VIRGINIA )

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COUbfTYOF HENRICO

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i The foregoing document was acknowledged before me, in and for the County and Commonwealth aforesaid, today by F. K. Moore who is Vice President - Nuclear Engineering Services, for W. L. Stewart who is Senior Vice President - Nuclear, of Virginia Electric and Power Company.

He is duly authorized to execute and file the foregoing document in behalf of L

that Company, and the statements in the document are true to the best of his knowledge and belief.

Acknowledged before me this _[f_. day of A7/2af,198/_.

My Commission Expires:

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IW Notary Public (SEAL) 1 l

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ATTACHMENT PROPOSED CHANGES TO TECHNICAL SPECIFICATIOf(S 6

NORTH ANNA POWER STATION-l-

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Virginia Electric and Power Company

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Dochet Nos. 338 & 339 Serial No. 91506 Attachment Pg 1/11 r

CONTENTS Saction Page 1

Discussion of Proposed Changes 2

2 Final Copy of Proposed Change Page::

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Determination of No Significant Hazards 9

(10 CFR 50.92 Evaluation) 1 t

Virginia Electric and Power Company

Docket Nog. 338 & 339 Serial No. 91506 Attachment Pg 2 /11 SECTION 1 PROPOSED CHANGES TO NORTH ANNA POWER STATION l

l TECHNICAL SPECIFICATION 3/4.3.2 l

l UNITS 1 AND 2 l

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1 DISCUSSION OF PROPOSED CHANGES l

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Virginia Electric and Power Company

Dochet Nos. 338 a 339 serial No.91-506 Attachment Pg 3 /11 QLEQUSSION OF PROPOSED CH ANGES BACKGROUND During a design basis event, the Engineered Safety Feature (ESF) systems are supplied electrical power by the 4160 Volt Emergency Busses. The availability of this equipment is assured by the Emergency Diasel Generators (EDGs) which provide full capacity back-up supplies.

The ESF electrical equipment is prevented from operatin0 n a reduced voltage i

condition, which could damage or incapacitate it, by anticipatory undervoltage inp relays which strip the emergency buses of electrical loads, start the EDGs, and then permit reloading the necessary ESF loads. The setpoints for these relays are subject to Technical Specification controls.

PROPOSED CHANGES Technical Soecification 3/4.3.2 Table 3.3-4 Item 6.e.

The Trip Setpoint specified for undervoltage protection of the Auxiliary Feedwater Pumps in Technical Specification 3/4.3.2 Table 3.3-4 Item 6.e, is currently listed as 257.5% of transfer bus voltage. This will be changed to 22392 volts on the transfer bus which is the actual voltage represented by 57.5% of 4160 volts (nominal voltage of the transfer buses). The Allowable Value is similarly presented as 252.5% of transfer l

bus voltage and is changed to 22184 volts on the transfer bus which is equal to 52.5%

l of 4160 volts. Therefore, these changes are administrative in nature and are intended to promote clarity and ease of use of the specification.

Technical Soecification 3/4.3.2 Table 3.3-4 Items 7.a. and b.

Changes in Trip Setpoint Voltage and Tolerance Values The Trip Setpoints values, time delays, and the tolerance values listed in Technical Specification 3/4.3.2 Table 3.3-4 Items 7.a and 7.b. are modified by this change.

l-These proposed values represent the minimum voltage and appropriate time delays l

required for the actuation of the Loss of Power sensing relays and are based on two considerations, The first consideration is to insures that during sustained reduced voltage situations, adequate voltage is provided to the ESF equipment for continued operation cnd that the equipment control power voltage is adequate to operate I

equipment control relays and contacts. The second consideration is to minimize the possibility of discconecting the emergency buses from the offsite power source during short term voltage drops, such as those caused by energizing large electrical loads.

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Docket flos 338 & 339 sonal rJo. 91-s00 Attachmont Pg 4 /11 The proposed Trip Setpoint voltage limits and tolerance values have been developed with these considerations to include relay drift, and conform to eur current undervoltage/ degraded voltage analyses and methodology.

The Trip Setpoint changes will assure that the the maximum analyzed relay drift will not result in the actual emergency bus voltage deviating from the degraded voltage analysis assumptions during a normal surveillance interval. The proposed voltage limits for Loss of Voltage and Degraded Voltage (Items 7.a and b.) and the tolerance for Loss of Voltage (item 7.a) are more restrictive than the current specification. The tolerance value for Degraded Voltage (Item 7.b) appears to be less restrictive, however a change of 17 volts on the 4160 volt emergency buses, results in the minimum discernible variance of the test instrumentation.

Bus voltage is determined by measuring the vo;tage output from a potential transformer with a voltage ratio factor of 60.6-to 1. Therefore a change of 7 volts on the 4160 volt primary side wu! result in a secondary sido change of only 0.1 volt.

Changes in Allowable Value Voltage Time Delays, and Tolerance Values The Allowable Values voltage ;imits, time delays, and tolerance values listed in Technical Specification 3/4.3.2 Table 3.3 4 Items 7.a and 7.b. are also modified by this change. These provide the minimura voltage and appropriate time delay values for the Technical Specification surveillance of undervoltage protection devices.

The proposed Allowable Value voltage limits and tolerance values have been developed in accordance with our current undervoltage/ degraded voltage (GDC-17) analyses and methodology. The proposed voltage limits for Loss of Voltage and Degraded Voltage (items 7.a and b.) are more restrictive than the current specification and conform to our current undervnitage/ degraded voltage analyses and methodology.

The time delay for the Degraded Voltage (Item 7.b) Allowable Value is also reduced from 7513 seconds to 563 seconds.

This is more restrictive than the existing specification and insures that the Emergency Diesel Generators will be supplying power to the emergency buses within 74 seconds.

The Trip Setpoint values contains adequate margins to prevent unnecessary disconnection from the offs :e po'vei source during transient, reduced voltage situations.

Therefore, it is not necessary to specify an upper boundary for the Allowable Values.

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Docket Nos. 338 & 339 serial No. 91506 Aitachment Pg 5 /11 The Allowabie Values for these items represent actual emergency bus voltage and time delay values. Relay drift will be accounted for in calculating the surveillance test acceptance criteria. The Surveillance test acceptance criteria will specify a range of values which will include the appropriate relay drift allowances calculated _to protect both ESF equipment from undervoltage situations and minimize the possibility of disconnection of the emergency buses from the offsite power source during short term voltage drops.

Therefore this amendment request changes the Technical Specification Allowable

- Values for items 7.a and 7.b, from bands defined by specific values with plus-or-minus deviations, to greater-than or-equal-to given minimum values, as well as providing new minimu ~ values based on the current undervoltage / degraded voltage (GDC-17) analyses and methodology.

Conclusion The new values for the Trip Setpoints and the Allowable Values ensure the continued protection of the ESF equipment from undervoltage conditions while minimizing the possibility _of unnecessary disconnecting from the preferred off-site power sources.

_ The values for the ~ rip Setpoints and the Allowable Values are at least as or more restrictive than the existing specification and are consistent with the regulatory basis for the Loss of Power and Degraded Voltage protection and the North Anna Units 1 and 2 Loss of Offsite ?ower (GDC-17) analysis while providing additional operating margins for future electncal loads.

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