PNO-I-89-039, on 890527,unidentified RCS Leakage Exceeded 2.5 Gpm & Plant Shutdown Initiated.Rcs Pressure Increased to 46 Gpm.Containment Entry Planned on 890530,after Deinerting. Maint Team Insp Initiated

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PNO-I-89-039:on 890527,unidentified RCS Leakage Exceeded 2.5 Gpm & Plant Shutdown Initiated.Rcs Pressure Increased to 46 Gpm.Containment Entry Planned on 890530,after Deinerting. Maint Team Insp Initiated
ML20247N752
Person / Time
Site: Millstone Dominion icon.png
Issue date: 05/30/1989
From: Mccabe E, Raymond W
NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
To:
References
PNO-I-89-039, PNO-I-89-39, NUDOCS 8906060017
Download: ML20247N752 (2)


DCS ilo: 50245890529 Date: May 30, 1989 T0$1 NARY NOTIFICATION OF EVENT OR UNUSUAL OCCURRENCE--PNO-I-89-39

'This preliminat'y 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 Nuc1 car Energy Company X Notification of Unusual Event Millstone Nuclear Station, Unit 1 Alert Docket No. 50-245 Site Area Emergency Waterford, CT General Emergency Not Applicable

Subject:

SHUTDOWN DUE TO HIGH RCS LEAKAGE During plant heatup on 5/27 after post-refueling startup on 5/26, operators noted that differential pressure (dp) on the inner recirculation pump "A" seal indicated seal failure. Power escalation continued; seal replacement planning was initiated. On 5/29, while at full power, unidentified reactor coolant system (RCS) leakage exceeded 2.5 gpm, and recirc pump "A" seal dp indicated outer seal failure. Power was reduced to 75%. Unidentified RCS leakage was measured at 8.5 gpm at 2:30 p.m. and confirmed at 3:50 p.m. An unusual event was declared based on a plant shutdown being required by high unidentified leakage. At 4:55 p.m., a controlled shutdown (50F/hr cooldown) was begun. RCS leakage increased. As measured by drywell and equipment drain sumps, maximum leakage was 46 gpm. (The Alert emergency action level is 50 gpm, and the recirc pump breakdown bushing is designed to limit leakage to 60 gpm at rated pressure). Io avo u possible valve binding, recirc loop "A" isolation valves were kept open. As RCS pressure dropped, leakage decreased. Drywell temperature rose from 135F to 142F. The drywell coolers were used to limit temperature. No equipment problems have been identified.

Containment monitors and a grab sample showed no significant change in drywell atmosphere radioactivity (3.5E-9 uCi/cc). Drywell inerting was maintained. The drywell was vented through the standby gas treatment system to keep pressure below 1 psig. Plant stack noble gas monitors showed no increase. Normal feedwater input was used for makeup. All emergency cooling systems (Low Pressure Coolant Injection, Feedwater Coolant Injection, Core Spray) were available but were not needed. Control rods were fully inserted by 11:00 p.m. The unusual event was terminated when cold shutdown was' achieved at 4:03 a.m., 5/30. By 8:00 a.m., shutdown cooling was in service, with the RCS at 148F, 0 psig. The last drywell leakage measurement was 17.4 gpm at 4:30 a.m., 5/30. Containment entry is planned about noon, 5/30, after deinerting.

The resident inspector responded to the plant during the evening on 5/29. The Haddam Neck senior resident inspector is on site to assist in follow-up, and the Shoreham senior resident inspector is enroute. A maintenance team inspection begins onsite today, should additional resources be needed promptly. The State of Connecticut was informed. The licensee has informed the Media.

CONTACT: W. Raymond Ebe McCabe (203) 447-3179 346-5231 89060 [ 090530 ggg ,

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CA NRR OGC OIA Regional Offices GPA 01 RI Resident Office PA SLITP EDO DE Licensee:

(Reactor Licensees)

Region I' Form 83 (Rev. April 1988) 1 I

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