ML19330C349

LER 80-012/03L-0:on 800708,during Performance of ST-RPS-3, F.2,discovered That Trip Unit 3 Setpoints Had Drifted Out of Spec in Nonconservative Direction.Caused by Normal Setpoint Drift.Setpoints Adjusted

ML19330C349
Person / Time
Site:	Fort Calhoun
Issue date:	07/11/1980
From:	Core M OMAHA PUBLIC POWER DISTRICT
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
Shared Package
ML19330C344	List: ML19330C343 ML19330C349
References
LER-80-012-03L, LER-80-12-3L, NUDOCS 8008080271
Download: ML19330C349 (4)

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EV ENT OESCRIPTION AND PROSASLE CONSEQUENCES h 10i: l l During cerformance of ST-RPS-3, F.2, it was discovered that Trio Unit e3 (Reactor I ici3 l Coolant Flow) trip setpoints had drifted out of scecification in the nonconservative i 10;4i l di rection . Maintenance order #6405 was written to investigate the drift. The R.P.S. I 10 i s i i was inmediately placed in a two-out-of-three logic to t.ip mode. Technical Saecifi- I F3 i s i I cation 1.3(2) acolies. I l

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03 4 ai 40 41 42 43 44 47 CAUSE DESCRIPTION AND CCARECTIVE ACTIONS h li t o l l After troubleshootina, it was discovered that the setpoints had drifted out of I i, ii i i saecification due to nomal drift. All other areas of cossible trouble were checked I is i,ii for procer coeratio m and- found to be satisfactory. The setooints were adiusted usinc !

i, t3i l the aaprocriate calibration crocedures and coeration was verified usino the acercorhte i i i .s i i surveillance test.

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. s, LER No.80-012 Omaha Public~ Power District Fort Calhoun Station Unit No.1 Docket No. 05000285--

ATTACHMENT NO. 1 Safety Analysis The . trip setpoint on "B" channel was out of specification by ap-proximately 60 millivolts in the nonconservative direction. The trip unit would have performed the required trip function at slightly lower flow than required. This led to only a slight degradation of the RPS as the other thre e channels were operable at the time with setpoints within tolerance. At no time would the RPS have failed to accomplish its intended purpose, that is, to safely shut down t1e reactor.

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w LER No.80-012 '

Omaha Public Power District Fort Calhoun Station Unit No.1 Docket No. 05000285 9

ATTACHMENT NO. 2 Corrective Action Upon inspection of the trip unit and associated circuitry, it was

' discovered that the setpoint of the bistable trip unit, Gulf Electronics

-Systems Part No. ELD 240-000-lF, had drifted, and no other components were affecting the trip units. The correct setpoint was set into the -

trip unit using the applicable calibration procedure, CP-RPS-3, and the channel was functionally checked using the applicable surveillance *est, ST-RPS-3, F.2. This trip unit and all others will continue to be monitored by applicable Surveillance Tests.

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4 LER No.- 8'0-012

~ Omaha'Public Pewer Distric '

-Fort Calhoun Station Unit No.1 Docket No. 05000285 ATTACHMENT NO. 3

' Failure Data This is'the second recortable occurrance of its kind at the Fort Calhoun Station. See LER 78-20.

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