ML20085J880

Ao:On 740523,during Routine Monthly Surveillance 2/3 Core Height Water Level Sensor Lits 3-263-73A Found to Have Setpoint Above Tech Spec Limit.Caused by Setpoint Drift. Switch Reset

ML20085J880
Person / Time
Site:	Dresden
Issue date:	05/31/1974
From:	Stephenson B COMMONWEALTH EDISON CO.
To:	Oleary J US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20085J883	List: ML20085J880 ML20085J887 ML20085J889
References
391-74, NUDOCS 8310190156
Download: ML20085J880 (2)

Text

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lir. J. F. O' Leary, Director b, ' .

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SUBJECT:

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C. i. SL C J .1 . iE 1 : .: CM C ! 6.b.P. l.a C ' T. : TP.CliMICAL SPM ul in C .T1 ;. ';.

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References:

1) Letter f rca W. P. Uorden to !!r. J. F. O' Leary dated :lovc=ber 19, 1973 concerning name subjact.

2) !?otification of Reaica III of /.EC Regulatory Operations Telephone: Mr. F. !:2ura,1345 hours0.0156 days <br />0.374 hours <br />0.00222 weeks <br />5.117725e-4 months <br /> on itay 24, 1974 Tcle gra:a: fir. J. Keppler, 1353 hours0.0157 days <br />0.376 hours <br />0.00224 weeks <br />5.148165e-4 months <br /> en Fay 24, 1974.

3) Evns: P6ID !!-26 Ca:. 12"3437

Dear Mr. O' Leary:

This letter is to report a condition relating to the cparatica cf the unit at chout 1600 'w:ra on ::ay 23, I Vi4. At this tira, the 2/3 core height vater Icral r, encor LITS 3-263 73A was fou id to have a cetpoint abova the Technical Specification limit of i 257" of water differential pressure decreasing.

a" Thin nalfunction is centrary to tabic 3.2.2 of the Tcchnical Specifications which requires that the centai:acnt spray syr.tcm be inter-Iccked to prevent cperation if reactor level is at or below 2/3 of the core height.

PROPTUI During routina r.:enthly surveille.n c of the 2/3 core height con-tainTant epray interlock level switches LITS-253-73A and B. switch "A" was found with a cetpoint of 259" 1I 2 0 differcatial pressura decronains. The r, witch was i:r.ediately cat to 254.5" U2 0 differential prcasure decreasing, h' +

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Mr. J. F. O' Leary \-) Hay 31, 1974 i

1 J NVESTICATION The switch in question is a Yarway number 441bEC device. Past surveillance hictory shows that the switch has been found out of specifica-i tions seven times in the past four years. The switch setpoint is normally 4

obcerved every roonth, during calibration and functional surveillances.

The manufacturer (Yaruny) has been consulted concerning the drif t probica and has identified five possible cources of setpoint drift. The procedure used by the Dresden Instrument Mcchanics has been analyzed by Yarway Corporation and has been described as " acceptable".

a CORRECTIVE ACTION Ievel nwitch LITS 3-263-73A was immediately reset to comply with the Technical Specifications.

The corrm:tive action to resolve the drift probica vill be to replace'the magnet, rpring, and =crcury cwitch on LITS 3-263-73A and B.

i These parts uare identified by the canufacturer as a source of setpoint drift. Proper instattation of the above parts will ensure that all five possible probica arcas pointed out by the manufacturer are corrected.

Other similar switches do not need this repair due to their nore reliable naturc, e

EVALUATICS

Leval evitch LITS 3-263-73A is nornally set at 96/144ths core

height. The out of spacification trip point would have been 94/144ths 3 core height. The function of the sensors is to provide a permissive to i

allow the use of the containment spray systc=.

Station abnormal procedures state that the reactor vesec1 1 cycl .

be normal prior to utilizint; the LFCI system in the containment cooling mode. Even though the cetpoint for loop "A" interlock was low, the operator would have verified the vessel level before nanually initiating containment a cooling. Therefore, this situation did not prenant a cafety hazard to either the plant personnel or the general public.

The cumulative experience to dato indicates thar Yarway level censorn are normally very relieble deviecs, the particular suitch in question being an exception. The failures associated uith LITS 3-263-73A are of a random nature. The canufacturer has' approved the procedure used to calibrate the instrements, and specific recommendations have been t specified. The corrective action stated above will impicment the recc=nend-ations.

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B. B. Stephensen Superintendent BBS:WEll:do

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