ML20059D238

Application for Amends to Licenses NPF-68 & NPF-81,revising TS to Allow One Time Extension of AOT for RHR Pumps from 3 to 7 Days.One Time Extension Necessary to Allow Mods to RHR Sys While Plant in Mode 1

ML20059D238
Person / Time
Site:	Vogtle
Issue date:	12/30/1993
From:	Mccoy C GEORGIA POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
Shared Package
ML20059D241	List: ML20059D238 ML20059D248
References
LCV-0232, LCV-232, NUDOCS 9401070083
Download: ML20059D238 (7)

Text

.

. Georga Power Company 40 inverness Cente Pyb.ay Pat Once Box 1295 Birrnegham. Amaama 35201 TMepnt.ne 205 B77 7122 L

C. K. McCoy Georgia Power vee pres,aent twe >

Vog% Propet December 30, 1993 ""#""""'"2'"*"

LCV-0232 Docket Nos. 50-424 '

50-425 LL S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D. C. 20555 Gentlemen:

VOGTLE ELECTRIC GENERATING PLANT REQUEST TO REVISE TECHNICAL SPECIFICATIONS ONE TIME EXTENSION OF ALLOWABLE OUTAGE TIME FOR RHR PUMPS In accordance with the provisions of 10 CFR 50.90 and 10 CFR 50.59, Georgia Power Company (GPC) hereby proposes to amend the Vogtle Electric Generating Plant (VEGP)

Unit I and Unit 2 Technical Specifications, Appendix A to Operating Licenses NPF-68 and NPF-81. The change will allow a one time extension of the allowe.ble outage time for each residual heat removal (RHR) pump from 2 to 7 days. The one time extension is necessary to allow modifications to the RHR system while the plant is in Mode 1. The modification will convert the pump / motor assembly to a coupled design. It involves the addition of a coupling and bearing between the pump and motor and replacement of the impeller and casing wear rings. The time is based on experience gained from the completion of the modifications on one of the Unit 2 RHR pumps. Performance of the modifications in Mode I will result in a significant reduction in personnel radiation exposure compared to performing it after plant shutdown, additionally it will allow both RHR pumps to be available to perform the shutdown cooling function. The modifications will increase the reliability and availability of the pumps as well as allow future nwintenance of the pumps and motors to be conducts under ronditions that will result in reduced exposure to radiation. The modification is necessary for operation of the RHR pura s at reduced flow.

During the time that each pump is being modified, the redundant RHR pump will be maintained operable. An evaluation of the effects of the one time increase in the allowable outage time on the calculated core damage frequency has been made. The evaluation was based on the results of the Individual Plant Examination (IPE). The IPE calculated a core damage frequency (CDF) of 4.9E-05 per reactor year. The conservative evaluation indicated that the cumulative effect ofincreasing the allowable outage time to 7 days, instead of the currently allowed 3 days, would change the CDF from 5.07E-05 to I

9401070083 931230 @4 ADDCK 05000424

'PDR )

P PDR 1 '

• 3 ,,

' Georgia Power b U. S. Nuclear. Regulatory Commission Page 2 5.34E-05 per reactor year for the modification of two pumps on Unit 1. The effect will be even less significant for Unit 2, since only one pump needs the modification.

Georgia Power Company requests approval of this change to the Technical Specifications by April 1994. This will allow the modification plans to be completed and implemented ~ .

between June and August of 1994, prior to the next scheduled refbeling outage.

The proposed change and the bases for the change are described in enclosure 1 to this  ;

letter. Enclosure 2 provides an evaluation pursuant to 10 CFR 50.92 showing that the . ,

proposed change does not involve significant hazards considerations. Instructions for  ;

~

incorporation of the proposed change into the technical specifications and a copy of the change are provided in enclosure 3.

]

In accordance with 10 CFR 50.91, the designated state official will be sent a copy of this letter and all enclosures.

Mr. C. K. McCoy states that he is a vice president of Georgia Power Company and is authodzed to execute this oath on behalf of Georgia Power Company and that, to the best of his knowledge and belief, the facts set forth in this letter and enclosures are true.

GEORGIA POWER COMPANY By:

C. K. McCoy Swont to and subscribed before me thish$1ay of [b.0m .1993.

u Abm;c(-

Fjbtar}2chlic in r.ne-smrymte la 1ma f

Enclosures:

1. Basis for Proposed Change

2. 10 CFR 50.92 Evaluation

3. Instructions for Incorporation and Revised Pages '

LCV-0232 70077$ .

i U. S. Nuclear Regulatory Commission Page 3 c(w): Georgia Power Comnany Mr. J. B. Beasley, Jr.

Mr. M. Sheibani '

NORMS i

U. S. Nuclear Regulatory Commission '

Mr. S. D. Ebneter, Regional Administrator Mr. D. S. Hood, Licensing Project Manager, NRR Mr. B. R. Bonser, Senior Resident Inspector, Vogtle State of Georgia Mr. J. D. Tanner, Commissioner, Department of Natural Resources I

LCV-0232 iF L

4.! .

< ENCLOSURE 1  ;

. VOGTLE ELECTRIC GENERATING PLANT  !

i REQUEST TO REVISE TECHNICAL SPECIFICATIONS ONE TIME EXTENSION OF ALLOWABLE OUTAGE TIME FOR RHR PUMPS BASIS FOR PROPOSED CHANGE 1 Proposed Change .;

The proposed change will add the following footnote to specification 3.5.2: ". The ':

allowable ot 2ge time for each RHR pump may be extended to 7 days for the purpose of .

convening the pump motor assembly to a coupled design. This exception may only be used one time per pump and is not valid after December 31,1994." ,

llMia >

The current design of the RHR pump and motor utilizes a single shaft. A modification is planned that will add a coupling to the shaft to allow the pump and motor to be disconnected. The modification will also include changes to the impeller that will improve ihmst bearing life and allow the; pumps to be operated at reduced flow. These ~ s modifications will improve pump performance, vibration lents, availability, and maintainability, as well as reduce radiation exposure during maintenance. The ability to' -

operate the pumps at reduced flow during operation with the reactor coolant system -

(RCS) partially drained has been recognized by the NRC as an improvement in safety. ~

Performance of the modification at power will allow it to be made when the RHR system is not needed to perform its shutdown cooling function and will allow it to be performed under conditions that result in reduced exposure of personnel to radiation. The one time -

extension of the allowable outage time from 3 to 7 days represents an insignificant effect- .

on the contribution of the RHR system to safety which is balanced against the increased pump reliability and reduced exposure to radiation that is achieved by performing the -t modifications while the plant is in operation.

One of the Unit 2 pumps has already been modified. The requested time of 7 days is .-

based on the experienca gained from the completion of that modification. The altemative for completion of these modifications while in Mode I is to perform one during each ,

outage which would result in a delay in the completion of all of the pumps for at least two . .

operating cycles 1

)

El-1

.1

e .,

ENCLOSURE 2 VOGTLE ELECTRIC GENERATING PLANT REQUEST TO REVISE TECHNICAL SPECIFICATIONS ONE TIME EXTENSION OF ALLOWABLE OUTAGE TIMis FOR RHR PUh YS 10 CFR 50.92 EVALUATION Pursuant to 10 CFR 50.92, Georgia Power Company (GPC) has evaluated the proposed revision to the Technical Specifications and has determined that operation of the facility in accordance with the proposed amendment would not involve any significant hazards considerations.

I}pckeround Modifications are planned for the RHR pumps that will enhance their maintainability, reliability, and performance and reduce exposure to radiation for maintenance workers.

The modification consists primarily of the installation of a coupling that will allow the pumps and motors to be disconnected. At the same time, modifications will be made that will improve pump performance and allow the pumps to be operated at reduced flow.

These changes will improve reliability and are necesuuy to allow operation at reduced flow which reduces tisk of pump cavitation during operation with the reactor coolant systen. {RCS) partially drained. One of the Unit 2 RHR pumps has already been modified.

The modifications for the remaining three pumps can be accomplished in 7 days for each pump. A significant reduction in exposure to radiation can be achieved for the modification ifit is made while the reactor is in operation because use of the RHR pump during shutdown increates the exposure rate in the vicinity of the pumps during periods shortly afler plant shutdown. In addition, one of the primary functions of the RHR system is heat removal during plant shutdown so it is desirable to have both trains available during that time. Therefore, it is proposed to make this modification while the plant is in Mode 1.

This will require a one time extension of the allowable outage time from 3 to 7 days. The modifications will be made on one pump at a time.

Analysis The large break loss of coolant accident (LBLOCA) is a design basis accident that is not considered as likely to occur during the lifetime of plant operation. It is used as a design'-

basis to assure conservatism. The safety function of the RHR pumps is to provide a low pressure, high volume water source for reflooding the core following a large break that results in a rapid depressurization. Following a small break LOCA, the RHR pumps may be required to provide suction pressure to the safety injection system during sump recirculation and for long term decay heat removal. The loss of coolant accident analyses only take credit for one train of RHR. The Technical Specifications require that both -

trains of RHR be operable in Mode 1. One train is allowed to be inoperable for a period of E2-1

y  : .j ENCLOSURE 2 VOGTLE ELECTRIC GENERATING PLANT REQUEST TO REVISE TECHNICAL SPECIFICATIONS ONE TIME EXTENSION OF ALLOWABLE OUTAGE TIME FOR RHR PUMPS 10 CFR 50.92 EVALUATION 3 days. The proposed change will provide for a one time extension of the allowable outage time from 3 to 7 days which will allow the modifications to be completed in 1994. - The alternative is to make the modifications during plant shutdown; however, that is during the time of peak radiation exposure rates from the RHR pumps due to their use during plant -

shutdown. A dose savings of 40 man-rem is expected by making the modification at power rather than afler a plant shutdown.

During this time, the redundant train will remain operable and be available to perform the -

safety function assumed by the safety analysis. The effects of having an RHR pump out of service for 7 instead of 3 days was evaluated. The evaluation.was based on the core damage frequency (CDF) from the Vogtle Individual Plant Examination (IPE). The CDF -

reported in the IPE is 4.9E-05/RY and used a historically based RHR pump outare time of 1.5 days per year. Use of the current allowable outage time of 3 days for each R1(8:L pump results in a CDF of 5.070E-05/RY. Use of a 7-day allowable outage time raises the CDF to 5.34E-05/RY. The effect will be even less significant for Unit 2, since only one pump '

needs the modification. The change results in a one time increase in CDF of 2.7E-06 above that which the current Technical Specifications allow, which is considered to be '

insignificant. Therefore, GPC has concluded that the increase in pump reliability and the reduction in exposure to radiation during the implementation of the modification justify; the performance of the modification during Mode 1 operation.-

- The safety function of the RHR will continue to be provided by the redundant train and, since the possibility of a design basis LBLOCA is small, an allowable outage time of 7 consecutive days is not significant to the CDF compared to the current allowable outage -

time of 3 days. In Mode 1, the RHR pumps are in standby; however, at least one is required to be in operation.when the plant is shut down. Therefore, performing the modifications in Mode I will allow both trains to be available for decay heat removal while

- the plant is shut down.

Conclusion Based on the above considerations, GPC has concluded the following concerning 10 CFR 50.92.

E2-2 4

c 4- ,

ENCLOSURE 2 VOGTLE ELECTRIC GENERATING PLANT REQUEST TO REVISE TECHNICAL SPECIFICATIONS

. ONE TIME EXTENSION OF ALLOWABLE OUTAGE TIME FOR RHR PUMPS 10 CFR 50.92 EVALUATION  :

F

1. The proposed change to the Technical Specifications does not involve a significant -

increase in the probability or consequences of an accident previously evaluated -

because the redundant train will remain available to. assure that the RHR will respond .;

to an accident as assumed in the accident analysis. A one time increase in the allowable outage time from 3 to 7 days has been shown to have only a small effect on the calculated frequency ofcore damage. q

2. The proposed change to the Technical Specifications does not create the possibility of a new or different kind of accident from any accident previously evaluated because the change only results in a one time increase of the allowable outage time. It does not .

result in an operational condition different from that which has already been considered by the Technical Specifications.

l

3. The proposed addition to the Technical Specifications does not involve a significant

. reduction in a margin of safety because the effects ofincreasing the allowed outage time on the calculated core damage frequency has been evaluated and determined to be -

small.

Based upon the preceding infonnation, it has been determined that the proposed Technical Specifications addition does not involve a significant hazards consideration as dermed by 10 CFR 50.92.

i E2-3 ,

i