ML20138G429

Discusses Contribution of Unit 1 Essential Svc Water Sys to Estimated Core Meltdown Frequency.Unit 2 Essential Svc Water Pumps in Final Stages of Preoperational Testing & Can Be Connected to Unit 1 Emergency Svc Water Sys

ML20138G429
Person / Time
Site:	Byron
Issue date:	12/06/1985
From:	Ainger K COMMONWEALTH EDISON CO.
To:	Harold Denton Office of Nuclear Reactor Regulation
Shared Package
ML20137Y697	List: ML20137Y693 ML20138G421 ML20138G429
References
NUDOCS 8512160323
Download: ML20138G429 (4)

Text

/ De 2 T's [( ~~ N Address Commonwealth Edison

} or.e First National Plaza. Chicago. Ithnois Reply to: Post Office Box 767

, N Chicago, Illinois 60690

, December 6, 1985 -

L Mr. Harold R. Denton, Director

! Office of Nuclear Reactor Regulation ,

i U.S. Nuclear Regulatory Commission l Washington, D.C. 20555 i

Subject:

Byron Station Unit 1 Essential Service Water System f NRC Docket No. 50-454

Dear Mr. Denton:

_. As a result of the review of the Byron LCO Relaxation Program, concerns have arisen regarding the calculated contribution of the Unit 1 essential service water (ESW) system to the estimated core melt frequency during the period i before operation of Byron Unit 2. These concerns were discussed with the NRC staff at meetings on December 3 and December 6, 1985. As proposed during the meeting on December 6, 1985, Commonwealth Edison will enhance the reliability of the unit 1 ESW system by making a Unit 2 ESW pump available during operation of Byron Unit 1.

^ The unit 2 ESW pumps are in their final stages of preoperational testing and can be connected to the Unit 1 ESW system through cross-tie piping existing in the the design. The following is a description of the administrative controls that will be put into effect to govern the availability of a unit 2 ESW pump until Byron Unit 2 is in operation.

I Prior to entering Mode 4, a Unit 2 ESW pump will be AVAILABLE to support Byron Unit 1 operation. The Unit 2 ESW

, pump will be considered AVAILABLE if it is capable of being manually started'and crosstied to the Unit 1 ESW system. The i L . y,_.A.

.. t - availability of. a. Unit: 2 ESW pump will be ensured by incorporating x 2.

the following surveillances into the Station Surveillance Program. *

1. At least once per day, Bus 241 will be verified to be energized if the 2A ESW pump is the AVAILABLE pump or i BUS 242 will be verified to be energized if the 2B ESW pump is the available pump.

1

2. At least once per day, the following valves will- be verified l open or capable of being operated from the main control '

board.

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2-l If 2A ESW pump - valves 2SXO33, 2SXO34, 2SX005,,*

is AVAILABLE 2SX001A, 2SX016A, 2SX027A If 2B ESW pump - valves 2SX005, 2SX001B, 2SXOi6B,

is AVAILABLE 2SX027B

3. At least once per 31 days, the AVAILABLE pump will be t

operated for 15 minutes.

g If neither Unit 2 ESW pump is AVAILABLE, either the 2A or 2B ESW pump will be restored to AVAILABLE status in 7 days or Byron Unit 1 will be in Mode 3 in 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and Mode 5 in the following 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />.

If only one Unit 1 ESW pump is OPERABLE and neither Unit 2 ESW pump is AVAILABLE, immediate action will be initiated to i

restore either a Unit 2 ESW pump to AVAILABLE status or a Unit 1 ESW pump to OPERABLE status. -

Byron Unit 1 is presently shutdown. Prior to entering Mode 4, operating procedures will be revised to instruct control room operators to crosstie the Unit 2 ESW system to the Unit 1 ESW system in the event both Unit 1 ESW pumps become inoperable.

Initial training on these procedures will be provided to control room operators involved with the startup of Unit 1.

i The actions described above will eliminate concerns regarding the calculated contribution of the Unit 1 ESW system to the estimated core melt frequency during the period before operation of Byron Unit 2. These actions will no longer be necessary when Byron Unit 2 begins to operate.

- Please address any questions you may have regarding this matter to this office.

Very truly yours, 47.

I K. A. Ainger -

Nuclear Licensing Administrator

, cc: Byron Resident Inspector

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This issue is still being investigated for any potential application to other W plants.

Sincerely, Hugh L. Thompson, Jr. , Director Division of PWR Licensing-A

Enclosure:

1. Memo from Thompson to Denton dated 12/5/85

2. Letter from Ceco to Denton dated 12/6/85 cc: J. Keppler F. Miraglia

.T. Speis R. Bernero W. Russell Distribution Docket or Central File i NRC PDR*

Local PDR*

PD#5 Reading File H. Thompson

, J. Stevens M. Rushbrook D. Eisenhut i

i 0FC :PD#5 :PD#5 :D: DIR  :  :  :  :

NAME :JStevens :VSNoonan :HThompson  :  :  :  :

DATC : / /85  : / /85  : / /85  :  :  :  :

! 0FFICIAL RECORD COPY f

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. . . _. . . _ . . . . .- . - - . . . = - .- - .

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ESWS to the estimated CMF during the period before operation of Byron Unit 2.

This issue is still being investigated for any potential application to other i W plants.

/

Sincerely, i

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/

l Hugh L. Thor.pson, Jr. , Director  ;

Division of PWR Licensing-A

Enclosure:

1. Memo from Thompson to Denton dated 12/5/85

2. Letter from CECO to Denton dated /12/6/85 1

cc

J. Keppler F. Miraglia T. Speis R. Bernero e W. Russell ,

Distribution / ,

4 i i Docket or Central File /

NRC PDR*

/

Local PDR* /

i PDf5 Reading File /

H. Thompson 1

J. Stevens /

M. Rushbrook D. Eisenhut i /

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!0FC ~ ,#5 :PDt5  : DIR  :  :  :  :

l___ _______:_______ :____________:____________.____________. ___________.___________

NAM

JStevens :VSNoona :HThompson  :  :  :  :

' DATE :lz /( 0/85_ _ _:/_V//d _ : _ _ _ _ _:_ /_ _/85 _ _ _ _ :: y 7_)/8 5  :  :  :

0FFICIAL RECORD COPY l

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