ML18153C957

Lists Compensatory Measures & Provisions to Maximize Margins of Safety During Bus Outage

ML18153C957
Person / Time
Site:	Surry
Issue date:	02/28/1992
From:	Stewart W VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	Ebneter S NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML18153C956	List: ML18153C955 ML18153C957
References
92-142, NUDOCS 9204060181
Download: ML18153C957 (4)

Text

. FEB 28 '92 16: 20 NLD ENCLOSURE e*_.

V1RcUN1A-Euc."'l*::iuc AlfD P~* Cox:P.&lfY H.%CKHOlfD,VI:RODUA G01!61.

February 28i 1992 United states Nuclear Regulatory COmml&alan

. Attn: Mr. Stewart Ebneter

• Region 11 Suite 2~0 101 Marietta Strtet, N. W

• Atlanta, Georgia 30323

Dear Mr. Ebnetar:

~IBGINIA £LECJB1C, AND P()WEB COMPANY

$LIBBY PQ'6'EB STATION UNrrs NO 1 AND 2 ELECTRICAL POWER SYSJ&M -

WAIVER Qf CQMPLIAMC(l Strlal. No.92-142. -

NL&P/JH/ETS

.*

• Docket Nos.

50*280 50*281 ucense Nos. DPR-32 OPR*37 An oil teak has developed on the eurre*nt transformer for Phase *c* of the No. 1 Switchyard Station Service Transformer In the station's 34.SkV distribution system.

Which supplies Bus No. 5. *The continuing oil leak will lead to eventual failure of the

• currint transformer and the potential loss of the No. 5 Bus. Bus No. 5 powers Reserve*

__ Station Transformers (RSSTa) 'A' and 'B'.which supply the Unit 1

• 1J and Unit 2

• 2H 4, 60V Emergency Buses, respectively. To replace the leaking ~ransformer it. will be necessary to d&-energlze Bus No. !5.. Oe-envrgizing the 'A' and 'B' RSSTs wiU require.

• that the electrical loads on the associated emergttncy bus be carried by the Emergency Diesel Generalors (EDGs): The 2H Bus will be powered by the No. 2 EOG and the 1J Bus will be powered by the No. 3 EOG. The No. 3 EOG Ii shared between Units.1 and 2 and can be aligned to power bus 1 J or 2J. With EOG No. 3 running on the 1J Bus,~ design basis accident on Unit 2 would cause the EOG lo transfer to the 2J Bus. However, on Unit 2, due to the breaker alignment this transfer would not occur

. on an undervoltage condition alone.

Therefore, the No. 3 e*oG is -considered inoperable for Unit 2.

T echni~I Specification 3.16 allows one otts~e AC power source or one EDG to be inoperable for seven dayG. but *does not address operation with both an Inoperable offsite power souroe and an Inoperable EOG. In addition, this electrical distribution.

configuration will cause two aJr conditioning chillers to be without both a normal and emergency power supply. Technical Specification 3.23 allows one air conditioning

_ chiller to be inoperable, but does not permit opirstion with two inoperable chillers.

Tnerefore, Units 1 and 2 will be required to enter Technical Specification 3.0.1. which requires that a unit be placed in Hot Shutdown within Six (6) hours.

We have estimated th.at the repairs and testing. of the current transformer could take approximately 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br />. Ther&fore, In a telephone conference call on February 9204060181 920302 PDR ADOCK 05000280 P

PDR

'I, FEB 28 '92 16:20 NLD 27,1992. with tfle NRC Region II and NRR staffs we requested a waiver of compllance from the_ requirements of Technical Specification 3.0.1 for 1 O hours to complete the.

• repair and tasting of the current transformer prior to entry into the six hour action-

. statement to Hot Shutdown. Verbal approval of the waiver was granted at that tirne to -

complete the transformer repairs. This letter formally documents the requested wavier.

. of compliance.

$AfEJY IMPACT ANP POTENTIAL CONSEOUENQES.

_ Maintaining Doth units at power, with Buses 1 J and 2H powered by the respective EOGs, has been evaluated from a nuclear safety_ perspective as the most desirable_

operating configuraUon for replacing the current transformer. Prompt replacement of tne leaking transformer minimizes the risk of a sudden failure and IOS8 of Bu1 No. 5.

With both units initially at power, the reactor coolant pumps and the secondary sy,tem& are. available for cote heat removal. Use of the EOGs to supply power to the emergency buses is in accordance with plant design, establi$hed procedures, and operator training.

Emergency bus loads have bHn reviewed, as well as EOG

,capabilities to ensure safeguards equlpr'nint can be started on the emergency buws in* an accident situation without overloading the EOG. Given certain Initial equipment

• alignments, the EDG can handle the required accident loads. Operation of the EDGs with a light load during the evolution has also been evalu~lted and 1ound acceptable.

In addition,. ~qulpment which Is important to sa1~ plant operation will initially be aligned in a manner which minimizes the impe.ct of an EOG failure on the plant. In the unlikely event of an EOG failure. backup power is available by manually re-energizing Bus No.. 5 from the 230/34.5kV Transformer No. 4, Whleh can be accomplished within approximately 60 minutes. Backup power is also available by backfeed from Unit 1 or Unit 2. or by closing the emergency bus tie breakers.

The governing procedure for removing. Bus No. 5 from *s,rvice contains the following.

compensatory measures and provlaions to maximize margins Qf safety.during the bus outagi:

1.

A Senior Op(irations Manager will be assigned to exercise continuous responSlbllltY tor oversight of thi evolution and will provide the partidpan~ with a pre*job ~~efirig ~,vering th&i pre~utions_ a~ limitations. This manager wiB_

oversee critical portions of the evolution and will have.the authority to terminate the procedure if-needed to ensure the safe operation of the unit.

2.

. Operations pirsonnel will review 1he Abnormal Procedures for los_s of-reserve station service power and $tation blackout. end the invo~ved personnel will review the procedure governing the evolution.

3.

Operators will be dedicated to the switchyard, the EDGs, and the Low Level

• Intake.

4.

The three EDGs will be confirmed to be fully operable prior to the repair evolution.

. FEB 28 'S2 15:,21 NLD

.5. *.

6.

7.

8'.

9.

10.

e

_ The action stati1m~11t log* will be reviewed for emergency bus loads which may be out of service.

The -system operator WIii be aware of th; evolution and will not perform..

switching which could afflilct the reliability of the Surry switchyard.

Maintenance will not be performed on any emergency bus component during the No. 6 Bus outage.

Swltchyard access will be restricted by the Security Department and Bus No. 6

• .will be roped off.

Plant responH to possible abnormal events is described in the governing

• procedure, and detailed contingency actions are specified.

. Electrical loads wiU be aligned to minimize. the consequences of_ possible *

. ~uipment failures and to assure EOO capability to assume safeguards load$ in an accident situation:

Given the Shon duration of thg bus outage, pre~autionary measures, failure modes and effects, and contingency actions associated with the removal of Bus No. 5 from.

service, it has been determined that no safety consequences will result from the plenned evolution and that the reQuested temporary waiver of compliance is reasonable and Justified, A safety evaluation has been performed and approved by

. SNSOC.

SlGNIFICANJHAi!ABDS CONSIDERATION The proposed waiver of compliance has been evaluated In accordance with the criteria contained in 1 o CFR 50.92 and. has been determined not to result in a significant hazards consi~eration.

1.

The. propos~d waiver does not significantly increase the probability or consequence$ of an aceiderrt previously evaluated. Since tM EDGs and the emergency power distribution system are not assum&d to be the sole Initiators of an~ accident previously* evaluated, the probability of such acciclents ii not increased. The con.sequences of a Loss o1-coolant Accident with a concurrent _

Lo.ss of Off-Site Power are not increased by the proposed operational configuration.

- 2.

The proposed ~ai~er will not create the possibility of a ne.w Qr different kind of accidem from any accident previously evaluated. No physi~I modifications to the plant are involved. Th& proposed waiver do8s not involve operation of any plant equipment in a different manner from which it was designed to operate.

Since a new failure mode is not created, a new or different type of aocident is not made possible.

.J

IJi.*

FEB 28 '92 16:22 l'l.D *e

3.

The proposed waiver does not involve a* significant reduction In a margin of safety. The propo,ed operational configuration.does not Involve changes to

• safety llmlt5 or limiting safety system settings.

Setpoints and operating parameters are not affected. Safety margins are. therefore. not reduced.

ENVIRONMENTAL CONSeOUENCES This walver will not change the types of any effluents that' may be released offSite, nor create a significant Increase In individual or cumulative occupatlonal radiation exposure. The proposed waiver does not Involve operation of any plant equipment In a diffv~ent manner from which It was designed to operate. Since a new failure mode le

• not created, a new or different type of aociden1 is not made possible. Therefore, the environmental oons~uenoes of each analyzed accident remains bounded by the existing design basis analysis.

Thi! waiver of compliance has been reviewed by.the Slation Nuclear Safety and Operating.committee and it has been determined that no unrevJewed safety question

. or significant hazards consideration exi~s.

Very truly yours, C).9{JN~

.L:e ~ W: L Stewart

"\\

senior Vi~ President

• Nuclear co:. U. S. Nuclear Regulatory Commission

• Document Control Desi<

Washington, o. c. 2_0555 Mr. M.-W. Branch*

• NRC senior Resident Inspector.

Surry Power Station