PNO-I-87-043, on 870514,during Reactor Trip Breaker Response Time Testing,Reactor Trip Occurred.Steam Generator Feedwater Isolation Pressure Transient Resulted in Failure of Two Lines to Thermal Relief Valves.Cause Under Investigation

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PNO-I-87-043:on 870514,during Reactor Trip Breaker Response Time Testing,Reactor Trip Occurred.Steam Generator Feedwater Isolation Pressure Transient Resulted in Failure of Two Lines to Thermal Relief Valves.Cause Under Investigation
ML20214G324
Person / Time
Site: Millstone Dominion icon.png
Issue date: 05/15/1987
From: Mccabe E, Shedlosky J
NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
To:
References
PNO-I-87-043, PNO-I-87-43, NUDOCS 8705270024
Download: ML20214G324 (1)


DCS No: 50423870514 Date: May 15, 1987 PRELIMINARY NOTIFICATION OF EVENT OR UNUSUAL OCCURRENCE--PNO-I-87-43 This preliminary notification constitutes EARLY notice of events of POSSIBLE safety cr 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 3 Notification of Unusual Event Docket No. 50-423 Alert Waterford, CT Site Area Emergency General Emergency l X Not Applicable

Subject:

REACTOR TRIP AND SHUTDOWN FOR OVER TWO DAYS A reactor trip from 69% power occurred at 10:07 a.m., May 14, 1987, during reactor trip breaker response time testing. All safety-related systems responded properly. The pressure transient caused by the accompanying steam generator feedwater isolation resulted in the failure of two (2) three quarter inch (3/4") lines to thermal relief valves for the tube side of two (2) of the three (3) feedwater heaters. The failure cccurred at the socket welds attaching the lines to the feedwater heater channel heads.

Dam:ge occurred to a feedwater heater isolation valve. There were steam leaks but no personnel injuries.

Initial review indicates that this was the first plant trip at high power with the constant speed motor-driven feed pump in operation, and that the accompanying fcedwater isolation pressure transient was larger than on previous isolations. The lic:nsee recreated the reactor trip breaker testing which was in progress at the time of the trip. All components functioned properly, with no actual trip generated.

Testing of the reactor protection system found proper operation.

The cause for the trip remains under investigation. Feedwater system repairs will take ab:ut two days. The licensee also plans to examine and evaluate high stress points in tha feedwater system to assess the potential for similar events. The resident inspector continues to follow licensee actions. Plant startup is not expected before May 19, 1987.

3 The State of Connecticut has been informed.

i l CONTACTS: J. Shedlosky E. McCabe 203-442-5357 215-337-5231 8-488-1231 DISTRIBUTION:

H. St. MNBB Phillips E/W Willste Mail: ADM:DMB Chairman Zech EDO NRR IE NMSS DOT:Trans only Comm. Bernthal PA OIA RES Comm. Roberts ELD AE00 NRC Ops Crt Crmm. Asselstine C:mm. Carr ACRS Air Rights INP0----

SECY SP NSAC----

CA PDR Regional Offices TMI Resident Section RI Resident Office Licensee:

(Reactor Licensees) k l

'M B705270024 870515 h_IM-o43 PDF

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