PNO-I-88-111, on 881022,manual Reactor/Turbine Trip Was Initiated Due to Lowering Main Condenser Vacuum.High Suction Differential Pressure Conditions Caused by Seaweed Impingement.All MSIVs Were Closed

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PNO-I-88-111:on 881022,manual Reactor/Turbine Trip Was Initiated Due to Lowering Main Condenser Vacuum.High Suction Differential Pressure Conditions Caused by Seaweed Impingement.All MSIVs Were Closed
ML20205H936
Person / Time
Site: Millstone Dominion icon.png
Issue date: 10/24/1988
From: Barber S, Bettenhausen L, Mccabe E
NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
To:
References
PNO-I-88-111, NUDOCS 8810310226
Download: ML20205H936 (1)


o -y DCS No: 50423881022 Date: October 24, 1988 PRELIMINARY NOTIFICATION OF EVENT OR UNUSVAL OCCURRENCE--PNO-I-88-111 This preliminary notification constitutes EARLY notice of events of POSSIBLE safety or public interest significance. The information is as initially received without verification or evaluation, and is basically all that is known by the Region I staff on this date.

Facility: Licensee Emergency Classification:

-Northeast Nuclear Energy Co. Notification of Unusual Event Millstone Nuclear Sta. Unit 3 Alert Waterford, Connecticut Site Area Emergency Docket No. 50-423 General Emergency

,X Not Applicable

Subject:

UNPLANNED SHUTOOWN IN EXCESS OF 48 HOURS On October 22, at 5:06 a.m., while at 100'4 power, a manual reactor / turbine trip was initiated due to lowering main condenser vacuum. The "A" main circulating water (CW) pump had been manually tripped off one minute earlier due to high suction differential pressure (DP). The high DP conditions were caused by seaweed impingement on its travelling water screens due to an early morning storm. Blockage in a trough used to sluice off normal debris backed up resulting in the inability of the screenwash system to continue to clean the screens. The stormy conditions also caused the automatic trip of the "B" CW pump on a high DP which resulted in a low vacuum in the "A" condenser which forced the manual trip. All safety systems responded appropriately to the trip.

All of the Main Steam Isolation Valves (MSIV) were closed because of the loss of condenser vacuum. The post-trip cooldown was stabilized at 557 degrees F. The resident inspector responded to the site and observed the operators stabilize the plant in hot standby.

While performing MSIV partial stroke testing in preparation for restart, the "A" MSIV folly closed during its surveillance. One of eight of its solenoids that ports steam above the operating piston failed to stroke properly. Subsequent partial stroke tests confirmed the failure. Because the solenoid is exposed to full main steam pressure, the licensee decided to go to cold shutdown aid effect repairs.

The licensee has notified the news media and the state of Connecticut about the shutdown and the decision to proceed to cold shutdown.

CONTACT: S. Barber E. McCabe L. Bettenhausen 203-442-5357 215-337-5231 215-337-5233 DISTRIBUTION:

OWFN MNBB H-St. NL Mail: ADM:DMB Chairman Zech AE0T) RR1 lies 00T:Trans only l Com. Roberts ARM POR Comm. Carr OGC NRC Ops Ctr Ce m . Rogers INP0----

SECY NMSS NSAC----

CA NRR OGC OIA Regional Offices GPA 01 RI Resident Off'ce PA SLITP /

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EDO OE Licensee:

(Reactor Licensees)

Region I Form 83 ,q pf (Rev. April 1988) 8810310226 881024 PDR I&E V / (> '

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FNO-1-SS-111 PDC