ML20085K177

Ro:On 730925,during Routine Surveillance,Hpci Flow Switch DPIS 3-2353 Had Trip Setpoint Above Tech Spec Limit.Caused by Setpoint Drift.Setpoint Corrected

ML20085K177
Person / Time
Site:	Dresden
Issue date:	10/24/1973
From:	Worden W COMMONWEALTH EDISON CO.
To:	Giambusso A US ATOMIC ENERGY COMMISSION (AEC)
References
797-73, NUDOCS 8310200253
Download: ML20085K177 (2)

Text

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e ComOwxith Edis::n One FA Miabonai Pla:a. Chicago. Illinois ' .

Address Reply to: Post Othce Box 767 Chicago Illinois 60690 .

50-249 WPW Ler.#797-73 Dresden Nuclear Power Station )

R. R. f1 '

Morris, Illinois 60450 " ' \ y, October 24, 1973 D p2  ! ts c Mr. A. Giambusso k. d #

Deputy Director for Reactor Projects \ , 4:h.p..f4;f A l

Directorate of Licensing , 4.c J U. S. Atomic Energy Commission Washington, D. C. 20545 * ' g ,t -

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SUBJECT:

LICENSE DPR-25, DRESDEN NUCLEAR POWER STATION, UNIT #3, SECTION 6.6.C.1 C7 TFE TECH:iICAL SPECIFICATI0:iS.

HPCI STEAM LINE HIGH FLOW SWITCH OUT OF CALIBRATION,

References:

1) Dwgs: P&ID M-51. S&L 12E2527

Dear Mr. Giambusso:

This letter is to report a condition relating to the operation of the unit at about 1600 hours0.0185 days <br />0.444 hours <br />0.00265 weeks <br />6.088e-4 months <br /> on September 25, 1973. At this time high pressure coolant injection (HPCI) flow switch DPIS 3-2353 was found to have a trip setpoint of 152.0" H 0. 2 This setpoint is contrary to Table 3.2.1 of the Technical Specifications which require a setpoint of f 150" H2 0.

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PROBLEM At the time of the occurrence, Unit 3 was operating in a steady state condition with a thermal load of 2295 MWe. Routine surveillance was being performed by the Instrument Department when HPCI flow switch DPIS3-2353 was found to have a setpoint of 152" H2 0. The switch was i==ediately reset to 148" H2 0. .The function of DPIS-3-2353 is to isolate the HFCI steam supply line in the event of a break in the steam piping.

INVESTICATION The " subject flow switch is a Barton model 288 differential pressure sensor. This switch has had a tendency to drift in both the increasing and decreasing direction. A locking device was installed on the switch in February of 1973 in an attempt to eliminate the drif t tendency. At the present time, the data from previous surveillances reveals that the locking device has not solved the drift problem. The overall problem of instrument setpoint drift is presently under investigation. The problem has plagued the station since its beginning, and no adequate corrective action has been determined at this time.

8310200253 731024 t PDR ADOCK 05000249 p J,d ~915 k > ct, m.

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Mr. A. Giambd b Octchsr 24, 1973 e s The most recent approach to the problem has been to solicit aid from the manufacturers of the various drif ting sensors. In the case of the Barton model 288, the factory representative has recommended that a field service engineer visit the station and analyse Barton switches with regard to application, factory adjustments, and calibration technique. The Barton representative has visitad the Station and we are now awaiting his recommenda-tions.

CORRECTIVE ACTION The immediate corrective action was to change the setpoint of DPIS-3-2353 to bring it within the Technical Specifications. The calibra-

! tion frequency for this switch will be increased to once per month until such time as this switch has demonstrated its reliability. Additional corrective action will be based on recommendations made by the Barton field service engineer.

EVALUATION Flow switch DPIS-3-2353 is one of two flow switches that isolate the HPCI steam line in the event of a break in the steam piping. The second switch is DPIS-3-2352, and its setpoint at the time of the occurrence was 146" H20. Therefore, it is concluded that in the event of a break in the HPCI steam line piping, isolation would have occurred well within the Technical Specifications, and thus the safety of the station personnel and j the general public was in no way compromised. The continued operation of i the unit was considered safe.

, Sincerely, ,

. Mb W. P. Worden Superintendent

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