ML17252B000

Letter Reporting a 01/10/1973 Occurrence Relating to the Discovery of a Containment Spray System 2/3 Core Height Interlock Sensor to Be Outside the Technical Specification Limit - Dresden Unit 3

ML17252B000
Person / Time
Site:	Dresden
Issue date:	01/19/1973
From:	Worden W Commonwealth Edison Co
To:	Giambusso A US Atomic Energy Commission (AEC)
References
Download: ML17252B000 (1)

Text

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50-249 Commonwealth Edison* Company 72 WEST ADAMS STREET

• CHICAGO, ILLINOIS Addreu Reply fo, 60450 January 19, 1973 Mr. A. Giambusso Deputy Director for Reactor Projects Directorate of Licensing

• U. S. Atomic Energy Commission Washington, D. C. 20545

SUBJECT:

LICENSE DPR~25. DRESDEN NUCIEAR POWER STATION, UNIT #3, SFCTION 6.6.B.2 OF THE TFCHNICAL SPECIFICATIONS.

Dear Mr. Giambusso:

• This is to report a condition relat~ to the unit in which, on January 10, 1973, a containment spray system 1 core height inter2ock sensor was fou,n4 to be .out.side._ the.. Tec~caL.Specificat~ons .limit or Z 1

• core

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• PROBLEM AND INVESTIGATION The two-thirds core height water level sensor (LITS 3-263-73A) is a Yarway serial number 24992.. The function of the sensor is to prevent use of the appropri~te containment spray system loop if the vessel water level is at or below ! core height.

• The setting found on the routine calibration

~heck performed January 10, 1973, corresponded to a level 2 inches below the J core height setting, full core height being 144 inches.

This sensor has not previously drifted more than 2 inches, remaining

.well within the band established to comply with Technical Specification: limits.

The difference between the previous instrument calibration setpoint andithe setpoint found on January 10, 1973, was seven inches. No nuclear safety re-lated consequences resulted from this sensor setpoint change, s~e the 'inter-lock would still have operated at a vessel level equivalent to 1L.L. core height, which is still essentially j core height for all practical purposes.

CORRECTIVE ACTION 2 As stated earlier, this is the first q~c~n_9e of significant drift in the 1 core height level sensor~ The calibration surveillance frequency will be increased from quarterly to monthly until *it can be established that this instrument is not exhibiting an increasedhtendency to dP.tft.

~*~.w~,

W. P. Worden