PNO-I-88-101, on 881005,MSIV C Closed Fully During Partial Stoke Testing of Valve,Causing Water Level Decrease in Steam Generator C & Reactor Trip on lo-lo Steam Generator Level. Shutdown Extended to Perform Maint on Valve

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PNO-I-88-101:on 881005,MSIV C Closed Fully During Partial Stoke Testing of Valve,Causing Water Level Decrease in Steam Generator C & Reactor Trip on lo-lo Steam Generator Level. Shutdown Extended to Perform Maint on Valve
ML20155E320
Person / Time
Site: Millstone Dominion icon.png
Issue date: 10/06/1988
From: Barber S, Bettenhausen L, Mccabe E
NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
To:
References
PNO-I-88-101, NUDOCS 8810120240
Download: ML20155E320 (1)


>. DCS No: 504P.388105 Date: October 6, 1988 o -

l ' PRELIMINARY NOTIFICATION OF EVENT OR UNUSUAL OCCURRENCE--PNO-I-88-101 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: Li m see Emergency Classification:

Northeast Nuclear Energy Company _

, Notification of Unusual Event Millstone Nuclear Station Unit 3 Alert Waterford, Connecticut ___ Site Area Emergency f General Emergency X Not Applicable  :

Subject:

UNPLANNED SHUTDOWN IN EXCESS OF 48 HOURS '

On October 5, 1988, at 1:53 p.m., while at 100*. power, the "C" Main Steam Isolation i

Valve (MSIV) closed fully during partial stroke testing of the valve. The partial ,

stroke testing was part of a a routine, surveillance. The MSIV-C closure resulted in a water lever decrease (shrink) in th? "C" Steam Generator (SG) and subsequent Reactor /

turbine trip on low-low SG 1evel. The resident inspector responded to the control room and noted that the operators and plant syste'ms responded as expected except that the post-trip cooldown was greater than expected (531 degrees F vice 557 degrees F). The larger than expected coolduwn was attributed to high auxiliary feedwater (AFW) flow in combination with high post-trip steam loads. The licensee is continuing to investigate the event sequence.

, The licensee is extending the shutdown for maintenance on the "B" main feedwater *

regulating valve, which was being operated in manual because it had been sticking during operation in automatic. Present plans are to perform all work with the plant

' i in hot shutdown and to start-up on October 8, 1988. i

The licensee notified the news media of the shutdown. The State of Connecticut has been informed.

This information is current as of 9:30 a.m. (EDT), October 6, 1988.

4 CONTACT: S. Barber E. McCabe L. Bettenhausen l

] 203-442-5357 215-337-5231 215-337-5233 1 l DISTRIBUTION:

OWFN MNBB H-St. NL Mail: ADM:0MB  :

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CA NRR OGC OIA Regional Offices

, GPA 01 RI Resident Office l PA SLITP E00 Licensee:

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[ReactorLicensees)

Region I Form 83 l

j. (Rev. April 1988) as1ot2024o so1006 f

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I PDR IbE F,DC os PNO-1-sa-101

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