ML20084T545

Ro:On 721004,during Routine Calibr of Reactor Low Pressure Permissive Switches,Two Switches Setpoints Had Drifted Above Tech Spec Value.Cause Not Stated.Switches Will Be Set to Ctr of Permissive Trip Setting Span to Prevent Recurrences

ML20084T545
Person / Time
Site:	Dresden
Issue date:	10/13/1972
From:	Worden W COMMONWEALTH EDISON CO.
To:	Giambusso A US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20084T542	List: ML20084T539 ML20084T545 ML20084T548
References
NUDOCS 8306230256
Download: ML20084T545 (2)

Text

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. '50999 Commonwealth Edison Company 72 WEST ADAMS STREET

• C H I C A G O. ILLINOIS m n.e rro POST OFFICE 802 767

• C H IC A O o, li t l N Olt 4 0 4 9 0 Dresden Nuclear Power Station R. R. #1 '

Morris, Illinois 60450 'J' O october 13, 1972 s, .

e M9b N? g e'Y 7.7

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- 4 I. log 7 Mr. A. Giambusso , 'd; 9 Deputy Director for Reactor Projects , y Directorate of Licensing N,,,

U. S. Atomic Energy Commission <

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l[h i Washington, D. C. 20545 hI l

SUBJECT:

LICENSE DPR-25, DRESDEN NUCLEAR POWER STATION, UNIT 43, SECTION l 6.6.B.3 0F THE TECHNICAL SPECIFICATIONS.

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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) drif ted 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 drifted above the Technical Specifications value of 350 psig.

The subject switek.es, PS-3-263-52A2 and PS-3-263-52B1, were found set at 371 psig and 356 psig respectively. This drift is in the safe dir-ectios,i and would result in opening the core spray and LPCI injection valves at a higher than design pressure. PS-2-263-52A2 is a Heletron switch, model number 372-6SS-49A with a range of 0-1200 psig and an accuracy of i 17..

PS-2-263-52B1 is an ITT Barton Switch, model number 288, with a range of 0-500 psig and an accuracy of i 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.

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B306230256 721120 PDR ADOCK 05000249 8 PDR I 1

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O O October 13, P772 Mr. A. Giambusso '

ts CORRECTIVE ACTION At the time of calibration, PS-3-263-52A2 and PS-3-263-52B1 were reset to 327 psig and 326 psig reattor pressure respectively. PS-3-263-52A1 and PS-3-263-52B2 were within the Tecnical Specification Limits.

Theyhavepreviouslybeensetascloseto350psigaspracticII..

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-3-263-5ZA2, will be Micro-switch PS-3-263-52B1 replaced since it has experienced excessive drif t. accuracy and so with the experienced drifsetpoint, new calibration t which was the within the instrumentSpecification limit should not be Technicait exceeded.

Sincerely, d.. U3dow W. P. Worden Superintendent i

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