ML20099J359

Special Rept:On 840808,inadvertent Safety Injection Occurred.Caused by Failed Lamps in Partial Trip Status Panel.Failed Lamps Replaced & Design Change Implemented

ML20099J359
Person / Time
Site:	Callaway
Issue date:	11/08/1984
From:	Miltenberger S UNION ELECTRIC CO.
To:	James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
References
ULNRC-970, NUDOCS 8411290017
Download: ML20099J359 (2)

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llNION lI.LECTRIC COMPANY CALLAWAY PLANT MAILING ADDRESS:

P. O. B OK S 2O FVLTON. MO, 652St

-PRINCIPAL STAFF .

November 8, 1984  ! /6A 7 gg gggyj j

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Mr. James G. Keppler 4

Regional Administrator Office of Inspection & Enforcement U. S. Nuclear Regulatory Commission Region III 799 Roosevelt Road Glen Ellyn, IL 60137 i

ULNRC- 970 DOCKET NUMBER 50-483 i CALLAWAY PLANT UNIT 1 FACILITY OPERATING LICENSE NPF-25 i

SPECIAL REPORT EMERGENCY CORE COOLING SYSTEM ACTUATION

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Dear Mr. Keppler:

I j This Special Report is submitted pursuant to Technical Specification 3.5.2 and 6.9.2 concerning an Emergency Core Cooling System actuation, t On August 3, 1984, Callaway Plant Unit 1 experienced an inadvertent Safety Injection (SI). Plant configuration just prior to the event was Mode 4, with the Reactor Coolant i System at 385 psig and 3260F.

The event was initiated when a Instrument and Controls technician placed a Reactor Coolant System (RCS) pressure

channel in the. TEST mode during the performance of a Tech-i nical Specification surveillance test. Three of the four instrument channels that monitor RCS pressure feed a permis-sive circuit which permits blocking of the Pressurizer Low Pressure /Steamline Low Pressure Safety Injection signals'at low RCS pressures. Prior- to the . event this permissive

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84112 17 841108 '

' PDR A K 05000483 PDR 6 NOV 161984 d

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Mr. James G. Keppler Page 2 November 8, 1984 circuit was in the " BLOCK" mode due to the plant being in Mode 4 with low RCS pressure. One of the three redundant pressure channels had failed in the tripped state due to incorrect strapping on the associated bistable. This tripped condition went undetected due to failed lamps on the asso-cicated windows of the Partial Trip Status Panel. Thus, when the pressure loop being calibrated was placed in the TEST mode, the required 2 out of 3 coincidence logic for the permissive circuit was satisfied. This caused the block of the SI signal to be automatically reset allowing the Pressurizer Low Pressure SI signal to cause an Emergency Core Cooling System (ECCS) actuation. This is the first ECCS actuation Callaway has experienced at temperature.

To prevent recurrence, the failed lamps in the Partial Trip Status Panel have been replaced and a design change implemented to correct the false bistable output. In addi-tion, I & C procedures are being revised to include a step to require a lamp test on the Partial Trip Status panel prior to putting an instrument channel into test.

Although an Unusual Event was declared, at no time did plant conditions pose a threat to the public health or safety.

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/ k S. E. Miltenberger SEM/WRC/SMB/ldj cc: USNRC Resident Inspector, Callaway Missouri Public Service Commission