IR 05000423/1986015

Page 1 to Insp Rept 50-423/86-15

ML20210U584
Person / Time
Site:	Millstone
Issue date:	05/29/1986
From:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
To:
Shared Package
ML20210U577	List: IR 05000423/1986015 ML20210U573
References
50-423-86-15, NUDOCS 8606030025
Download: ML20210U584 (1)

Text

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• a, Summary of Facility Activities The plant was operating at 75% power at the beginning of the inspection perio Nuclear were instrumentation in-core and ex-core axial flux difference calibrations in progres Power was increased to 90% following a brief power reduc-tion to repair an Electro-Hydraulic Control System fluid lea The plant reached rated thermal power, 3411MW(t), at 2210, April 1 The final tests in the power ascension program were conducted on April 21, when 10% load swings and a full power generator load rejection test was com-pleted from 1184MW(e).

The reactor was made critical at 2300 the same day and the unit was declared to be in commercial operation at 0001 on April 2 A steam leak occurred on a bolted manway closure of the "A" Moisture Separator Reheat Steam Drain Tank at 0711 on April 2 was tripped in an attempt to isolate the leak. Load was reduced and the turbine Later, a reactor trip occurred from 10% power on low steam generator level when the operator lost level con-tro Following repairs, the reactor was made critical at 1944, April 23 and was returned to full power at 0311, April 25 to begin the One-Hundred-Hour War-ranty Run. This was completed at 0825, April 2 The plant operated at full power until 0909, May 9, when the turbine was manually tripped in response to the loss of two condenser circulating water pumps. This occurred when in-take structure traveling screen clogging caused high differential pressur The plant remained shutdown until 2024, May 12, when the reactor was again made critical.

t A water hammer occurred at about 1900, May 12, while preparing to place the

"C" First Point (High Pressure) Feedwater Heater in servic The plant startup had been made with the heater isolated to repair a crack on the supply line to a shell side relie The water hammer damaged the heater emergency level control valv The heater remained isolated to allow repairs to the valve operator and yok . Review of Plant Events Power Reduction for EHC Repair On April 14 , at about 0730, an Electro Hydraulic Control (EHC) System oil leak was discovered on the "D" main turbine governor valve. The plant was at 75% power, 878HW(e). Oil was spraying at approximately one gallon per minute; there was no danger of loss of reservoir level but there was a concern about possible damage of electrical cable insulation in the vicinity. A power reduction was started immediately. The generator was taken off-line, and the turbine was secured at 0838. Mode 1 was main-tained; the reactor was borated to 10% power. Repairs were undertaken as soon as the affected portion of the EHC system was depressurized. The oil spill was well controlled and cleaned up. No electrical cable insu-lation was properly affecte seated The cause of the leak was determined to be an im-

"0" Ring in the control block valve to the governor valv ,

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