PNO-I-88-118, on 881113,licensee Shutdown Plant in Response to High Unidentified Leakage Into Primary Containment.Caused by Increase in Unidentified Drywell Leakage.Licensee Will Replace Topwork for Both D & E Safety Relief Valves

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PNO-I-88-118:on 881113,licensee Shutdown Plant in Response to High Unidentified Leakage Into Primary Containment.Caused by Increase in Unidentified Drywell Leakage.Licensee Will Replace Topwork for Both D & E Safety Relief Valves
ML20206D912
Person / Time
Site: Millstone Dominion icon.png
Issue date: 11/14/1988
From: Barr S, Bettenhausen L, Raymond W
NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
To:
References
PNO-I-88-118, NUDOCS 8811170322
Download: ML20206D912 (2)


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, OCS No: 50245881113

. Dau : November 14, 1988 PRELIMINARY NOTIFICATION OF EVENT OR UNUSUAL OCCURRENCE--FNO-I-88-118 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: Northeast Nuclear Energy Co. Licensee Emergency Classification:

Millstone Unit 1 XX Notification of Unusual Event Docket No. 50-245 Alert Waterford, C1 ~~ Site Area Er ergency General Emergency Not Applicable

Subject:

SHUTOOWN DUE TO HIGH UNIDENTIFIED LEAKAGE INTO PRIMARY CONTA!WENT Millstone 1 began an erderly plant shutdown on 11/13 at 7:35 a.m. in c'.sponse to a 2.69 gpm unidentified leakage rate into primary containment, in excess of the 2.5 spm TS limit. The licensee declared an unusual event and notified the NRC Operations Center via ENS.

Earlier, at 12:30 a.m. on 11/13, the operators noted that both drywell pressure and the differential pressure between the drywell and torus increased. During subsequent investigation, the operators noted an increase in unidentified drywell leakage (from 0.75 gpm to 0.94 gpm), a two degree F increase in the drywell ventilation units, and a three degree F increase in the 0 and E safety relief valve (SRV) tailpipes.

Unidentif frA leakage increased to a maximum of 3.0 gpm at 10:00 a.m,; the E SRV tailpipe temperature continued to increase and stabilized at 225 degrees F. The above indications led the licensee to suspect '. hat a vacuum breaker on the E SRV ta11 pipe had failed open.

On 11/13, with RPV pressure at approxinately 600 psig, the licensee conducted a visual inspection of the accessible vacuum breakers. The inspection identified an open vacuum breaker on the O tailpipe which shut when tapped, and steim leaking into the E tailpipe as evidenced by the steam released when an associated vicuum breaker was tapped. The licensee plans to replace the topworks for both the 0 and E SRV's; they are in transit from Wyle Labs and are expected to be received on site today. The unusual event was terminated at 9:10 a.m. on 11/14, and the plant was in cold shutdown at 12:55 a.m. on 11/14. The licensee expects to return to full power on 11/16. The SRV topworks had been obtained earlier to support a planned shutcown for replacement, but the valves leaked upon test and had to be reworked at Wyle.

This information is current as of 8:00 a.m., November 14. The resident staff is reviewing the event and is following tne licensee's actions.

The State of h nnecticut has been notified.

CONTACT: S. Barr L. Bettenhausen W. Raymond 215-337-5097 215-337-5233 203-442-5357 jg11g22 851114 FNO-I-88-118 FDC h, **

50245.381113 2 DitTHIBUTIQN:

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SECY NMSS NSAC----

CA NRR OGC OIA Regional Offices TMI Resident Section GPA O! RI Resident Office PA SLITP EDO OE Licensee:

(Reactor Licenstes)

Region I Form 83 (Rev. April 1988) 9 i-l l

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