ML20084S108

Ro:On 730515,during Routine Calibr of Isolation Condenser High Condensate Flow Switch DPIS-3-1349-B,setpoint Found Exceeding Value in Tech Specs.Cause Unknown.Investigation Underway

ML20084S108
Person / Time
Site:	Dresden
Issue date:	05/25/1973
From:	Worden W COMMONWEALTH EDISON CO.
To:	Giambusso A US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20084S111	List: ML20084S108 ML20084S121
References
407-73, NUDOCS 8306160157
Download: ML20084S108 (2)

Text

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Commonalth Edison N

,e q mj One First N(di Plata. Chictgo Ilhnots

.Q Addrzss Reply to: Post Off.ce Box 767 Chicago, it!inois 60690 Dresden Nuclear Power Station R. R. #1 Morrin, Illinois 60450 WP4 Ltr. #407-73 May 25, 1973 3 2

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s Pr. A. Giambusso 50-249 S' ag4 iw if fp Y-"

Deputy Director for P.cactor Pro,jects 2 U '

D Directorate of Licensing 1

%gDJ;., g U. S. Atemic Enerry Commission g 4OS-gg , , Sur Washingten, D.C. 20545 tij$,9?

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SUBJECT:

MCF??SE OPR-25. 09FSDE'I NUCIIAR POWF3 STATIC?f. U?IIT 43, \/

SECTIC?; 6.6.B.2 CF THE TECH?IIC AL SPECIFIC ATIO!!S.

Dear Mr. Giambusso:

This is to report a condition relating to the operation of the unit, in which, durine veutine calibratien of the isolation condenser hich cenden-sate flew switch DPIS-3-1349-B the setpoint was fcund to exceed the value epecified in Table 3.2.1 of the Technical Specifications.

PROBTIM A?'D INVESTIGATIC?!

On May 15, 1973, du*ine a routine calibration, the isolation conden-ser high condensate flow switch DPIS-3-1349-3 was fcund to actuate at a differ-ential pressure of 32.7_ inches of wate . The Technical Specification limit as set fcrth in Table 3.2.1 for the hich ccndensate flow switches is 3 32 inches of water. The high cendensate flew switches have a range of 0 to 60 inches of water and an accuracy specificatien of i LT of full scale. .

CC9RFCTIV:' ACTIC?!

This switch last exhibited excessive drift en September 22, 1972.

At that tir.e the setroint was lowered frem3031 inches of water to 28.5 i 1 l inches of water to increase the range to prevent the switch frem drifting above the Technical Specificatien limit. On Feb*uary 7,1973, a locking de-vice was installed to also help prevent the drifting situation. Since the switch is still drifting beycnd allowable limits, further action is warranted.

The station procedures will be changed to recuire calibration ad.justment to 27.511 inches of water fer both switches in the condensate return line.

This' action will further increase the rance to p?cvent the switch f"em driftinc above limits. Alto, calibratien of the switches will be perforced menthly rather than once eve y three renths as listed in Table 4.2.1 of the Technical Specifications. These ccrrective actions will remain in effect while an in-vestigatien is cenducted to determine the cause of the pechlem. The investi-gatien will take approximately six renths. This corrective action only applies to unit 3 since unit 2 switches have not exhibited this p oblem.

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. COPY SENT REGION

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t Two sensors (DPIS-3-1349 A & B) on the isolation condenser return line are

! provided to detect the failure of the isolation condenee* line and actuate  !

isolation action. The sensers are arranced in a 1 out of 2 logic to treet 4 the single failure criteria. The trip setting and valve closure ti:ne are such as to prevent un.coverine the core er exceedint* site limits. There are no implicaticns er effect en the safety or public health because the redun-dant switch (DPIS-3-1349-A) would have actuated within the Technical Speci-fication limit. This switch actuated at 29.4 inches of water during the routine calibratien.

' Since the locking devices have been installed en similar switches on units 2 & 3, this has been the first failure. Therefore, it is believed to be an isclated occurrence. These chances should prevent future recurrence

. of drift beycnd Technical Specification limits in the subject switch.

N. .Ub W. P. Worden Superinterrient Dresden Station l WJ:MST :Jw cc: KFd Ltr. File a

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