ML17252B018

Letter Reporting a 10/04/1972 Condition Relating to the Discovery of Two of the Reactor Low Pressure Permissive Switches to Have Drifted Above the Technical Specifications - Dresden Unit 3

ML17252B018
Person / Time
Site:	Dresden
Issue date:	10/13/1972
From:	Worden W Commonwealth Edison Co
To:	Giambusso A US Atomic Energy Commission (AEC)
References
Download: ML17252B018 (2)

Text

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• Commonwealth Edison Company 72 WEST ADAMS STREET

• CHICAGO. ILLINOIS Addreu /leply fo,

~-""'U' T OFF1ce'eox 767 *CHICAGO, ILLINOIS 60690 Dresden Nuclear Power Station R. R. #1 Morris, Illinois October 13, 1972 Deputy Director for Reactor Projects Directorate of Licensing U. S. Atomic Energy Commission Washington, D. C. 20545

SUBJECT:

LICENSE DPR-25, DRESDEN-NUCLEAR POWER STATION, UNIT f>3. SECTION 6.6.B.3 OF THE TECHNICAL SPECIFICATIONS.

Dear Mr. Giambusso:

This is *to report* a* condition relating to* the operation of.- the unit in which, on October 4, 1972, the setpoints of two of the reactor low pressure permissive switches (for opening core spray and low pressure coolant injection admission valves) drifted beyond the values established:

in Table 3.2.2 of the Technical Specifications.

PROBLEM AND INVESTIGATION On October 4, 1972, during routine calibration of the reactor low pressure permissive switches (required every three months by Technical Specifications), two of the switches setpoints were found to have d.rifted above the Technical Specifications value of 350 psig *

. The subject switches, PS-3-263-52A2 and PS-3-263-52Bl, were found set at 371 psig and 356 psig respectively. This drift is in the safe dir-ection and would result in opemlng the core spray and LPCI injection valves at a higher than design pressure. PS-2-263-52A2 is a Meletron switch, model number 372-6SS-49A with a range of 0-1200 psig and an accuracy of +/- 1%.

PS-2-263-52Bl is an ITT Barton Switch, model number 288, with&a range of 0*500 psig and an accuracy of +/- 4%.

, A similar occurrence was experienced on Unit 2 on September 19, 1972 and was explained in a letter to Mr. Giambusso from Mr. Worden dated September 29, 1972.

Mr. A* ...Gi~mb~sso October 13, 1972 CORRECTIVE ACTION At the time of calibration, PS-3-263-52A2 and PS-3-263-52Bl were

.' reset to 327 psig and 326 psig reactor pressure reapectively. PS-3-263-52Al and PS-3-263-52B2 were within the Technical Specification Limits.

They have previously been set as close to 350 psig as practical.

Since these' switches have a 50 psig permissive trip setting span (Table 3.2.2 of the Technical Specifications) they will be set to the center of this span to prevent future recurrences. The micro-switch,PS-3-263*52A2, will be replaced since it has experienced excessive drift. Micro-switch PS-3-263-52Bl experienced drift which was within the instrument accuracy and so with theI new calibration setpoint, the Technical Specification limit should not be exceeded.

Sincerely, W. P. Wo~den Superintendent

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