ML20084H682

Ro:On 710510,high Drywell Pressure Sensor Reset Failed. Caused by Magnet Attached to Bellows Pivoted Out of Position.Magnet Adjusted

ML20084H682
Person / Time
Site:	Oyster Creek
Issue date:	06/14/1971
From:	Finfrock I JERSEY CENTRAL POWER & LIGHT CO.
To:	Morris P US ATOMIC ENERGY COMMISSION (AEC)
References
13250, 2799, NUDOCS 8305040724
Download: ML20084H682 (2)

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%=.f M ADISoN AVE.NUE AT PUNCH DoWL ROAD e MO R RISToWN, N. J. 07960 e 5 33 - 611 f June 34, 1971 f

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Dr. Peter A. Morris, Director

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Diviulon of Reactor Licencing United States Atomic Energy Commission j

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Dear Dr. Morris:

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Subject:

Cycter Creek Station $[lj[- . . '

Docket 50-219 liigh Dryvell Pressure Sensor Reset Failure The purpose of this letter is to report the failure of Containment Spray System High Drywc31 Pressure Sensor IP 15A to reset after being tripped for surveillance testing.

Following the succeccful initiation of the Containment Spray System on May 7,1971, which requires the coincident signal of two Ret.ctor Lo Lo Water Level scusars and two Drywell lii Pressure censors ,

the signalc were irriediately removed and the pumps automatically stopped when the dryvell preccure indicaticn dropped belcw 1 psig. Hcwever, since the pump operability checx was to be conducted concurrently, the scnsors were again tripped to initiate the syatem and were maintained in that condition until the pump operability check was completed.

After the ci nals 6 were removed and the mode switch placed in

" Dyna *.ic 1" in pr qaration for returning the system to normal, the Containment Spray System " Auto Start" signal alarm was actuated. The alarm vac nat actuated with the .:tode ovitch in " Automatic I". After the Iteactor Lo in Water Level and Hi Drywell Presnure signals were rcmoved, troublechooting reveg. led the problem to be a failure of the 2 poig increasing trip portion of IP 15A to reset. By alternately increasing and decreacing the vacuum drawn on the low side of the cenror, which increaccc an1 decreases the differential presaure on the bellows act,nbly, the P pcig trip flaally reset. A differentin1 prescure war again applied to the switch to check the trip and reset l function, but this tine the trip did not occur until precsure had been [

increased to an ro.vimately 3.'l paig. 'i"ne high trip point wac recet to 2 psic und the r. witch netud. tion then checked satiuractorily twice.

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,Y Dr. Peter A. Morric Poge II June 14, 197]

Cn May 10, 1971, it van decided to check the Containment Spray Cyctem Automatic Actuation again due to the erratic behavior of IP 15A on May 7 Tne switches operated properly at their desig-

. nated cet pointa but again, after removal of the test signals and transfer of the mode cvitch to " Dynamic I", the Containment Spray System I " Auto Start" signal alarm was actuated indicating no reset

) action of cenaWP 15A. A thorough investigation of the censor proved that the magnet attached to the bellovo which actuates the 2 poig increasing portion of IP 15A had pivoted out of pocition, fpreventingtheswitchcontactsfrcmresetting. However, once reset, the switch cet point was changed resulting in the increase from 2 poig to 3 7 poig. The magnet vaa realigned and secured, the switch reacccmbled, and the set point readjusted to 2 psig. After ten natisfactory trip and reset checks, the sensor vac returned to service.

Although the Containment Spray System vac initiated at the proper cet point in each of three actuation tests, Containment Spray Syctem I may not have been initiated at the proper time if the cause of the change in set point had nct been discovered and rectified. As stated in Section VI of the FDSAh and Amendment 32, l only one Containsent Spray Cooling System is required to remove j heat from the primary containment following a design basic accident.

l The redundant cycten would have caticfied that requirement. Further, l the Technical Specificationa permit power operation to continue for l a period not to exceed reven days if one Containment Spray loop is out of service. On May 10, 1971, when the switch malfunction became evident, repairs were initiated and the problem corrected immediately.

A check of other indicating switchec of this type vill be made and neasures vill be taken to prevent the set screvo holding the magnets in pocition from loosening.

Twenty-five copien of this report are attached.

Very truly yours, UdD > .- )hhts 4 Ivan H. Finfrjek, 8 Manager, Nu car Generating Stations IRF/pk l

Attnehmenta ec: Mr. R. W. Kirkman, Regional Director Division of Compliance L..