PNO-I-88-041, on 880414,unidentified Leak Exceeded 6 Gpm Limit.Leak Identified from PORV Block Valve Packing Leakoff Line.Manual Valve in Leakoff Line Shut Off.Checks for Leaks & High Temp Investigation Continuing

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PNO-I-88-041:on 880414,unidentified Leak Exceeded 6 Gpm Limit.Leak Identified from PORV Block Valve Packing Leakoff Line.Manual Valve in Leakoff Line Shut Off.Checks for Leaks & High Temp Investigation Continuing
ML20151H431
Person / Time
Site: Millstone Dominion icon.png
Issue date: 04/15/1988
From: Bettenhausen L, Mccabe E, Raymond W
NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
To:
References
PNO-I-88-041, PNO-I-88-41, NUDOCS 8804200386
Download: ML20151H431 (1)


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4"* > > 7 DCS No: 50423880414 Date: April 15, 1988 PREO MINARY NOTIFICATION OF EVENT OR UNUSUAL OCCURRENCE--PNO-I-88-41 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:

Millstone Nuclear Sta. Unit 3 X Notification of Unusual Event Waterford, CT Alert 9.yu Site Area Emergency General Emergency Not Applicable Subjecti RCS UNIDENTIFIED LEAKAGE EXCEEDS LIMIT On April- 14, 1988, the plant was in hot standby after an April 13 plant trip due to loss of condenser vacuum caused by high circulating water traveling screen differential pressure. At 5:15 p.m., April 14, an Unusual Event was declared when Reactor Coolant System (RCS) unidentified leakage increased to ~6 gpm. The licensee identified that the inner of two Reactor Vessel (RV) 0-rings had begun to leak at 1:00 p.m. That sent steam to the Containment Drain Transfer Tank (CDTT). Feedback to valve stem leakoffs directed to the CDTT is hypothesized to have caused other leakage to begin. The 6 gpm leakage began after the telltale drain from the inner 0-ring cavity was isolated. The licensee detected the leak by noting increasing pressure in the COTT and inc eased containment gaseous radiation concentration.

A Containment entry was made at 8:00 p.m., and a leak was identified from the "B" PORV block valve packing leakoff line. A manual valve in the leakoff line was shut at 9:10 p.m. , April 14. CDTT pressure then dropped below the 75 psi relief setpoint and the CDTT relief reset. The licensee concluded the leak had been found and that the block valve outer packing and lantern rings were holding, and the plant de-escalated from the Unusual Event at 9:30 p.m. About 2:00 p.m., April 15, the licensee concluded that unidentified RCS leakage was ~1.1 gpm, and re-declared an unusual event. A Containment entry began about 3:00 p.m., to check for leaks and investigate high temperature (>120F) in the pressurizer cubicle. If the leakage problem is not clearly resolved in four hours, the licensee plans to go to cold shutdown.

Ssaweed and other debris that clogged the intake screens due to easterly winds is being

, removed. CDTT pressurization to at least 100 psi due to PORV block valve packing leakage is under evaluation.

Local new media were informed of the Unusual Event declarations by the licensee. The

, State of Connecticut has been notified.

This PN is current as of 3:15 p.m., April 15, 1988.

CONTACT: W. Raymond E. McCabe L. Bettenhausen 203-442-5357 215-337-5231 215-337-5233 i

1 8804200386 880415 0I PDR I&E PNO-I-88-041 DCD ~ [- ~ 3N