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 P Commonwealth Edison Co
To:	Giambusso A US Atomic Energy Commission (AEC)
References
Download: ML17252B000 (1)

Text

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

Dear Mr. Giambusso:

• This is to report a condition 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 .. .limit or Z 1

• core

• height. .** ,.; .. _,,,.j . *

,... * .. *. *. . . . . . ... ,., . " . . ' 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 containment spray system loop if the vessel water level is at or below ! core height.

• The setting found on the routine calibration 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 lated consequences resulted from this sensor setpoint change, the 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 of significant drift in the 1 core height level 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. P. Worden