05000373/LER-1982-031

LER 82-031/01T-0:on 820528,while Performing Turbine Stop Valve Test,Lead Accidentally Grounded,Tripping Reactor Protection Sys Bus A.Isolation Dampers Would Not Close. Caused by Override of Damper Trip Signals

ML20054F637
Person / Time
Site:	LaSalle
Issue date:	06/10/1982
From:	Damron J COMMONWEALTH EDISON CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML20054F633	List: 05000373/LER-1982-031, Forwards LER 82-031/01T-0
References
LER-82-031-01T, LER-82-31-1T, NUDOCS 8206170177
Download: ML20054F637 (3)

LER-2082-031,

Event date:
Report date:
3732082031R00 - NRC Website

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While perforning a special test on urbine stop valves, a Icad was accidentally groundef, tripping RPS Bus A causing a scram and PCIS isolations. 0.B. Sec. Cont. isolation 9

-,, dampers would not close; their signals were found to be overridden at solenoids. When 9 override was removed and dampers timed," 1VR05YA was too slow. Sec. Cont. was not requiyed

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at this time. Also, l.B. Sec. Cont. isolation dampers would have closed on isolation i

signal, although SYA was in slightly degraded condition due to slow time at closure. I Plant was in safe condition at all times.

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, 't. LER HUMBER: 82-031/0lT-0

11. LASALLE COUNTY NUCLEAR STATION: Unit 1 Ill. DOCKET NUMBER: 050-373 IV. EVENT DESCRIPTION While installing test equipment for LST 82-37 TSV Position Sw. Setpoints, a Control Systems Technician (CST) of the instrument Maintenance Dept.

accidentally touched a lif ted lead to ground, tripping ADS Bus A. This resulted in a full scram (no rod movement, as all were fully inserted) and PCIS isolations. However, nei ther Secondary Containment isolation damper closed, IVR04YA, IVR05YB. Investigation by Operating Dept. shi f t per-sonnel revealed that these outboard Isolation dampers had their trip signals overridden at their local " air to open when energized" solenoids.

Af ter the " override" of the solenoids was removed LOS-CS-Ql, Secondary Containment Damper, operability test was performed to demonstrate oper-ability of all four isolation dampers. IVR05YA closed in > 10 seconds; greater than its Tech spec Ilmit.

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V. PROBABLE CONSEQUENCES OF THE OCCURRENCE Plant conditions at the time of the occurrence did not dictate that Secondary Containment was required. Secondly, the Div. 11 (outboard) secondary contain-ment isolation dampers were in an operable condition, although slightly degraded, to provide the necessary containment boundary should it have been needed. There was and is no i rradiated fuel on site and therefore no gases s -- or particulate in need of treatment before any potential release. The plant was in a safe condition at all times.

VI. CAUSE Relay IPDS-VR049X4, which is in the logic circuit to permit the Olv. 1 (inboard) secondary containment dampers to open when it energizes and to isolate them when it de energizes, had been previously found reluctant to make full contact when energized, thus not permitting these dampers to open.

W.R. 15845, wri tten 5/22/82, which is still outstanding, was issued to repair the relay. The " fail safe" function of this relay, i.e. de-energize to isolate the dampers, was not affected.

The secondary containment i solation dampers are air to open. Upon receipt of an isolation signal, air bleeds from the cylinder holding the damper open, through an exhaust port on the solenoid, as a set of springs pull the dampers closed. Apparently, when unable to open or keep open the dampers in question, shift personnel " overrode" the dampers solenoids by utilizing a small valve attached to each solenoid, which permits the damper to be opened locally, by passing all open or close logic signals to the solenoids.

Therefore, when the RPS bus tripped, the dampers would not close.

Failure of IVR05YA to close within its prescribed time during the surveillance

, was traced to a plugged (di rt, oil, etc.) breather at the exhaust part of its solenoid.

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, Ill. CORRECTIVE ACTION Upon discovery of the solenoids being overridden, shift personnel immediately returned them to the norm i state. Caution cards were hung at the solenoids to warn any,and all not to tamper wi th the manual override valve. Work Request 16055 was issued to lock wire these small override valves in the normal posit *on'.

Work Regt.es t 160'I*wasissuedtocorrect the slow closing of IVR05YA. TI.e i ot rty breather de$cribed earlier was replaced, damper retimed at 4 ten .

secohds and damper declared fully operable 6/2/82. A work request has also been written to clean, or replace as necessary, the exhaust port breathers on the remaining dampers' solenoids to prevent a similar occurrence.

Each shift engineer will be required to discuss this incident with his crews.

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