ML17252B001

Letter Reporting a 01/08/1973 Occurrence Relating to the Switches for HPCI High Flow Isolation Drifting Above Technical Specification Limit - Dresden Unit 3

ML17252B001
Person / Time
Site:	Dresden
Issue date:	01/17/1973
From:	Worden W Commonwealth Edison Co
To:	Giambusso A US Atomic Energy Commission (AEC)
References
WPW Ltr. #44-73
Download: ML17252B001 (2)

Text

Regulatory.

.L!:..:..... -ls..:....... - .....*

ei 'file ~Y~-

11: ** ~:.:t ..........;-..~ ... ~ ....

50-249 Commonwealth Edison Company 72 WEST ADAMS STREET

• CHICAGO, ILLINOIS Addre11 Reply to:

. POST OFFICE BOX 767 *CHICAGO, ILLINOIS 60690.

Dresden Nuclear Power Station R. R. #1 Morris, Illinois WPW Ltr. #44-73 January 17, 1973 Mr. A. Giambusso Deputy Director for Reactor Projects Directorate of Licensing U. S.

• Atomic Energy Commission Washington, D.C. 20545

SUBJECT:

UCENSE DPR~25. DRF1'DEN NUCLEAR POWER STATION, UNIT #3 SECTION 6.6.B.2 OF THE TECHNICAL SPECIFICATIONS.

Dear Mr. Giambusso:

This.is to report a condition relating to the unit.in which, Ori January 8 1973 ~ ~t:he . . switches for the High Pressure Co'olant Injection System (HPCI} high *flow isol.8.tion drifted above the Technical Specification limit of a differential pressure of~ 150 inches *of water. The switches were immediately recalibrated to comply with the Technical Specification limits.

PROBLEM AND INVESTIGATION The swit*ches are Barton* Model #288 differential pressure sensors identified as DPIS 3-2352 aiid DPIS 3-2.3~.3. The history or these switches shows drift *in* both the increasing and decreasing direction. This drift problem has been investigated and the manufacturers SU.ggested correction is to install locking devices on the

• calibrating screws to prevent screw movement caused by normal plant vibration.

The function of DPIS .3-2.352 and DPIS .3-2.353 is to isolate the HPCI syatem in the event of a breakage in the.HPCI steam supply piping.

Although the switches drifted above the Technical Specifications, they did operate, and in the event of a break in the steam piping would have isolated the HPCI system *at 150.5 inches differential pressure. Consequently, we conclude that this slight switch drift no safety hazard.

t..---.L~

,(..i,)

DOCl<mtl

. USAEC

CORRECTIVE ACTION As mentioned above, the manufacturer or*Ba.rt"on Model #288 switches has been consulted concerning this drift problem, and has made specific recommendations as to a corrective action. This corrective action consists of installing locking devices on the switch calibrating screws. The locking devices have be.en received and are presently being processed throughCOmrilonwealth Fdison Quality Assurance. The devices will be installed,* after Quality Assurance approval, on all Barton Model

1. 288 switches and any other switch with similar problems, with an esti-mated completion date of March 1, 1973. A follow up study will be per-formed to assure that the locking devices have corrected the drift problem on the Barton Model #288 switches. A follow up letter will be provided upon completion of this study.

Sincerely, tJJ.~. w~

W. P. Worden WPW:WH:jlw cc: WPW Ltr. File

(

. ' \

• *' j '

. ,.'