PNO-I-88-049, on 880506,plant Shutdown Commenced to Locate Source of Boric Acid Buildup on Control Element Drive Mechanism Coolers & Ventilation Shroud & Unidentified Leakage.Util Plans to Replace Reactor Vessel Head O-rings

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PNO-I-88-049:on 880506,plant Shutdown Commenced to Locate Source of Boric Acid Buildup on Control Element Drive Mechanism Coolers & Ventilation Shroud & Unidentified Leakage.Util Plans to Replace Reactor Vessel Head O-rings
ML20154B094
Person / Time
Site: Millstone Dominion icon.png
Issue date: 05/09/1988
From: Bettenhausen L, Peter Habighorst, Mccabe E
NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
To:
References
PNO-I-88-049, PNO-I-88-49, NUDOCS 8805170063
Download: ML20154B094 (2)


4

. OCS No: 50336880509

.q* Date: May 9, 1988 PkLIMINARYNOTIFICATIONOFEVENTORUNUSUALOCCURRENCE--PNO-I-8 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 i staff on this date.

Facility: Northeast Nuclear Energy Company Licensee Emergency Classification:

Millstone Nuclear Station Unit 2 Notification of Unusual Event Docket No. 50-336 Alert Waterford, Connecticut Site Area Emergency

General Emergency '

X Not Applicable

Subject:

PLANT SHUTDOWN IN EXCESS OF 48 HOURS A plant shutdown was commenced at 9:00 p.m. on May 6,1988 to locate the source of boric acid buildup on the Control Element Drive Mechanism (CEOM) coolers and ventilation shroud, and to locate the source of unidentified leakage (0.7 GPH on 5/3).

The source of boron in containment was not located during a shutdown on April 8, (PHO-I-88-40). During control rod insertion at 1:45 a.m., May 7, CEAs-14, 16 (Group 6), dropped 43 steps, and CEA-31 (Group 1) droppad 17 steps, all from the initial fully withdrawn position. Each CEA was realigned with its respective group and rod insertion was completed. Inspections inside the containment were completed with '

the reactor in hot standby.

The initial inspections on May 7 identified minor valYe packing and flange leaks on reactor coolant instrument isolation valves. Subsequent containment inspections to investigate the lower reactor vessel and reactor vessel flange areas identified boric acid on the north end of the biological shield, the floor of the biological shield, and a small deposit (approximately 1/16" x 6" of acid residue on the reactor vessel just below the flange. RCS water droplets originating from the flanse area were observed flashing to steam. At 8:15 p.m. on May 7, upon further reactor vessel head '

inspections, the licensee concluded both the inner and outer reactor vessel "0" rings -

were leaking and commenced a plant cooldown to cold shutdown.

i As of 6:00 p.m. on 5/8, the plant was in cold shutdown (Mode 5), at 190 F. The i licensee plans to replace the reactor vassel head "0"-rings, repair CEAs 14,16, and 31, clean the boric acid from the reactor vessel, CEDM coolers, and ventilation shroud, and complete other maintenance. The outage is scheduled to last approximateley 17 days.

The licensee been informed.notified the news media of the shutdown. The S. ate of Connecticut has l

This information is current as of 6:00 p.m. (EDT), Mcy 8,1988.

l CONTACTh P. Habighorst E. McCabe L. Bettenhausen Q 203-442-5357 215-337-5231 215-337-5233 '

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Region I Form 83 (Rev. April 1988)

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