ML20084U994

Ro:On 720307,while Conducting Monthly Surveillance Tests on Lpci,Containment Spray Interlock Relay 1530-110AW Would Not Energize.Caused by Incorrect Wiring Contrary to Wiring Diagram.Wiring Changed to Correspond W/Diagram

ML20084U994
Person / Time
Site:	Dresden
Issue date:	03/17/1972
From:	Worden W COMMONWEALTH EDISON CO.
To:	Morris P US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20084U996	List: ML20084U994 ML20084V005
References
NUDOCS 8306290691
Download: ML20084U994 (3)

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PC$t CP' fE RCE Fe7 e CatC&GO, stLINOIS e0400 Dresden Nuclear Fower Station R. R. ll Morris Illinois 60450 Farch 17, 1972 a

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Dr. Peter A. Morris y 3:

Division of Reactor Licensine

. U. S. Atomic Energy Comission 1e

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Washington, D. C. 20 % 5

. .q . )s SU N ECT-V LICE 2135 DPR 25, DRESDFE *1l CLEAR POWER STATTON UNIT M ,

. SECTION 6.6.B.2 0F THE TECHNICAL SPECIFICATIONS

Dear Dr. Morris:

This is to report a condition relating to the operation of the station when, during nonthly surveillance testing of the Iow Pressure >

Coolant Injection System (LPCI), a wirinr error was found in the logic -

circuitry which provides a permissive to utilize containment sprays under accident conditions, provided reactor water level is creater than 2/3 core height. ,

PROBI2M AND INVESTIGATION On March 7, 1972, at 1500 hours0.0174 days <br />0.417 hours <br />0.00248 weeks <br />5.7075e-4 months <br />, while conducting monthly surveillance tests on the Iow Pressure Coolant Injection System (LPCI), a containment spray interlock relav (1530 110AW) would not energize. This relav provides permissive to utilize containment sprav if reactor water level is areater than 2/3 core heicht. Investication revealed that one side of the rela:r was wired such that the "LPCI System low flow switch, (3-1501-589) was included in the relay circuit, contrary to the wirine diacram. (Refer to attached schematic.)

The 'LPCI System low flow" switch contact is normally closed when the surveillance test is conducted. During this particular surveillance testing, however, the ' low flow' switch calibration had drifted and the

, contact on this switch was open. This resulted in the de-energization of p( relay 1530-110AW. The drift in the calibration of the " low flow switch was thus responsible for the events which led to the discovery of the g wiring error G.' this also explains the fact that this wiring error was g not detected twing previous surveillance testing. pg,/ pf M

gy- 8306290691 720317 PDR ADOCK 05000249 R,li S PDR COPY SENT REGIONE

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O O Dr feter A. Morris - 2- March 17, 1472 i

i review of the construction and preoperational tests indicated that tre relay was tested, but not with the LPCI pumps runnine and hence with the LPCI 3ystem low flow switch open. These facts explain why the wirine error kss not detected durine the construction and preoperational test pnases.

IL should he noted that the LPCI Subsystem was always operable during the period when the wirine error existed. The effect of this wiring error was only to prohibit a permissive signal to spray the contain- i ment when the reactor water level was higher than the two-thirds core i height position during an accident condition. This operation, in spite  ;

of the wirins error, could hwe been performed by means of a bypass switch which is part of this subsystem. In addition, it was determined that there was no safety sirnificance related to the calibration drift of the low flow switch. (These switches are calibrsted routinely. )

The cirruits on similar rela.7s on the corresponding subsystema on Dresden Unite 2 and 3 were checked and found to be wired properly.

COPRECTIVE ACTION The wirinc circuit for relay 1530110AW was changed to correspond with that on the wiring diacran and the 'LFCI System low flow' switch was recalibrated. The required surveillance test was rspeated satisfactorily  ;

following the wiring change.

Sincerely, u >-

W. P. Worden i Superintendent NFh':ls i Enc.

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