PNO-II-89-058, on 890814,reactor Tripped from 93% on Turbine Trip.Caused by Loss of Condenser Vacuum as Result of Ruptured Seal Between Condenser & Turbine.Investigations Underway.Licensee Estimate of 5-day Outage Noted

PNO-II-89-058:on 890814,reactor Tripped from 93% on Turbine Trip.Caused by Loss of Condenser Vacuum as Result of Ruptured Seal Between Condenser & Turbine.Investigations Underway.Licensee Estimate of 5-day Outage Noted

ML20246D117
Person / Time
Site:	Grand Gulf
Issue date:	08/15/1989
From:	Cantrell F NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
To:
References
PNO-II-89-058, PNO-II-89-58, NUDOCS 8908250259
Download: ML20246D117 (2)

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August 15, 1989 PRELIMINARY NOTIFICATION OF EVENT OR UNUSUAL OCCURRENCE PNO-II-89-58 This preliminary notification constitutes EARLY notice of events of POSSIBLE safety or public interest significance. The information is as initially received without verifi-cation or evaluation, and is basically all that is known by the Region 11 staff on this date.

FACILITY: System Erergy Resources, Inc. Licensee Emergency Classification:

Grand Gulf Unit 1 Notification of Unusual Event Docket No. 50-416 Alert Port Gibson, MS Site Area Emergency General Emergency X Not Applicable

SUBJECT:

OUTAGE TO EXCEED 48 HOURS On August 14, 1989, at 8:18 a.m. (CDT), the reactor tripped from 93 percent (after power w:s reduced from 100 percent) on a turbine trip. The turbine trip was caused by a loss of condenser vacuum as a result of a ruptured seal (rubber boot) between the condenser and the turbine. All control rods inserted fully except rod 32-45, which inserted from full out to position 08. This rod was driven in manually without additional problems. (The licensee is investigating to determine why this rod stopped at position 08.) Both recirculation pumps tripped as. a result of the high pressure ATWS signal (pressure spike) generated when the turbine stop/ control valves fast closed to initiate the turbine trip. The main steam isolation valves were closed manually before the condenser vacuum decreased to the automatic closure setpoint. MSIV F022B. failed to close manually, and did not close until about 10-15 minutes af ter the isolation signal as a result of low condenser vacuum. The-electrical circuits appear to be satisfactory. The licensee plans to check the solenoid and shuttle valves in ti.e air supply to MSIV F022B a# .er they get in the drywell. Safety relief valves were used to control reactor pressure until a mechanical vacuum pump was started. MSIVs were reopened and the condenser was used to bring the plant to cold shutdown. RCIC was manually initiated and secured without reactor level decreasing to the l initiation point. The licensee is also investigating why the vent valves on the scram discharge volume failed to open to permit draining the SDV after the scram. Initially the scram signal could not be reset because the scram discharge volume could not be drained. Investigation showed that the air supply to the drain and vent valves have apparently been " bumped closed." (Valve adjacent to a passageway and was not guarded or wired in position.) There is no apparent connection between the failure of control rod 32-45 to insert fully and the SDV vent valve failure. The licensee estimates a five day outage.

The Region has dispatched a Projects Section Chief to monitor licensee actions.

The State of Mississippi has been notified.

The NRC received initial notification of this event by telephone from the Shift Superintendent at 12:01 p.m. (EDT) on 8/14/89.

This information is current as of 2:00 p.m. (EDT) on 8/15/89.

CONTACT: F. Cantrell - 841-5534 8908250259 890815 N Ik 9-058 PDC g i

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