ML20084K580

AO 50-265/74-13:on 740613,ECCS Low Level Switch LIS-2-263-72D Failed.Caused by magnet-switch Air Gap.Switch Tested Weekly Until New Switch Installed

ML20084K580
Person / Time
Site:	Quad Cities
Issue date:	06/21/1974
From:	Kalivianakis N COMMONWEALTH EDISON CO.
To:	Oleary J US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20084K568	List: ML20084K565 ML20084K580 ML20084K589 ML20084K594
References
AO-50-265-74-13, NJK-74-127, NUDOCS 8305190484
Download: ML20084K580 (3)

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Guad-CitiEA Generating Station Post Ofoce Box 216

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June 21, 1974 \ g/

Mr. John F. O' Leary, Director Directorate of Licensing Regulation U. S. Atomic Energy Co=ission Washington, D. C. 20545

REFERENCE:

QUAD-CITIES NUCLEAR POWER STATION DCCKET NO. 50-265, DPR-30, APPENDIX A, SECTIONS 1.0. A.4, 3.2.B, AND TABLE 3.2.2

Dear Mr. O' Leary:

Enclosed please find Abnormal Occurrence Report No. A.O. 50-265/

74-13 for Quad-Citics Nuclear Power Station. This occurrence was pre-vicuely rmrted t.: 2:cien III. Directorate of Replatnry Oparnt'. L.-

telegherc e.. Jui.e 13,19~4 and 6 ,yuu and Region III, Direci,orai,e of Regulatory Operations by telegram on June 14, 1974.

This report is subW.tted to you in accordance with the require-ments of Technical Specification 6.6.B.l.a.

Very Truly yours, 1

l- CClC/.0?T4EALTH EDISCN CCMPANY

QUAD-CITIES NUCLEAR PCUER STATION

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REPORT NUMBER: A.O.-50.-265/74-13 REPORT DATE: June 21,1974 OCCURRENCE DATE: June 13, 1974 FACILITY: QUAD-CITIES NUCLEAR POWER STATION CORDOVA, ILLIN0IS 61242 IDENTIFICATION OF OCCURRENCE:

Failure of ECCS Low-Low Level Switch LIS-2-263-72D CONDITIONS PRIOR TO OCCURRENCE:

Unit 2 Reactor in cold shutdown condition. .

DESCRIPTION OF OCCURRENCE:

While doing routine surveillance _of LIS-2-263-72D on June 13, 1974, it failed tc...ctuate. When tha '-- -- ' Vechani . l'ahtly pressed the mercury-vetted sullch, the unit funciloned properly and conLinued Lo do so. This failure was in violation of Technical Specification Section 3.2.B and Table 3.2.2 DESIGNATION OF APPARENT CAUSE OF CCCURRENCE:

Upon investigating the internal mechanisms of the level switch, it was found that the indicating arm wasn't energizing the mercury-vetted switch as it traveled in an arc. The switch functioned properly after it was touched and it could not be made to malfunction again. It appears that the magnet-switch air gap is marginal and may be responsible for the poried-ic failure of the switch.

ANALYSIS OF OCCURRENCE:

There are four low level switches arranged in a one out of two-twice logic.

Even though LIS-2-263-72D vas failed, the other three checked normal and the syctem would have operated as designed if it vore needed. Thereforo, there are no safety implications resulting from the occurrence that would jeopardize the safe operation of the plant or endanger the health and safety of the public.

CORRECTIVE ACTION:

A new level switch has been ordered and vill be installed to replace the

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. v switch that failed when it is received. In the interim, in addition to normal quarterly surveillance of the level switch, a functional test will be performed weekly until the switch is replaced. These actions should assure continued safe operation of the reactor and pre-vent repetition of this occurrence.

FAILURE DATA:

This switch has failed once before and was the subject of investigations at that time. The exchange of information and letters suggested several possible causes for the failure but reached no definite conclusions.

Subsequent to the failure, the switch performed satisfactorily until this occurrence. In view of the previous failure, the course of action de-scribed above has been decided upon.

The failed component is a Yarway Model 4418C Level Switch,' calibrated to I indicate from minus sixty inches to plus sixty inches water level.

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