ML19352A098

LER 76-031/01T-0:on 761222,stack Gas Low Flow Alarm Sounded in Station Control Room.Caused by Ice Plug in Sample Line. Ice Plug Formed as Result of Failure in Heat Tracing of Line.Heat Tracing Replaced & Sample Line re-insulated

ML19352A098
Person / Time
Site:	Oyster Creek
Issue date:	01/03/1977
From:	Ross D JERSEY CENTRAL POWER & LIGHT CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
References
LER-76-031-01T, LER-76-31-1T, NUDOCS 8103040452
Download: ML19352A098 (3)

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7 0 50 59 G3 G1 00 69 74 'e b Evi.NT Of SCH.DTICN : On h'ednesday, December 22, 1976, at approximately 0700 hours0.0081 days <br />0.194 hours <br />0.00116 weeks <br />2.6635e-4 months <br />, a y [ " Stack Gas Low Flot:" alarm sounded in the Station Control Room. The alarm is set 7 1 9 t rI'ji at 1 SCFil aiiHTsusually associlifeb w1Th th-c need'To cli31 Trot 11 Thc stack- gas-- -

@[] l sample filters. Accordingly, a technician was dispatched and the filters were 7 8 9 charged. The stack gas sample system flow returned to normal and the loiTTliET'a1Xrni ~

b Lc1c 1rci Some erratic flow was observed during the next three hours of operation but 7 0 9 it should be noted that the system was still considered operable Wring this t1%~ - '-

b} !.fiince._the_roni10Iine system is_n. Lot hi.ghly denendent upon flow. In addition, the particular attention to the oTT gas and ~

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7 nu S5l l_ Control Room Operators were instructed to payarctL_T.111lo.tigp monitors for anv evidence of increase. The co

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@ [line. The ice plug _ formed as the result of a failure ia the heat tracing of the 7 o 9 line. The heat tracing was replaced and the sampic line was reinsulated. The

$ l installation of an ammeter, which will provide _ positive indication of the heat 7 0h tracing operability, will be investigated.

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@ l_at 1045 hours0.0121 days <br />0.29 hours <br />0.00173 weeks <br />3.976225e-4 months <br /> the stack gas sampic system was declared _ineperable and_ preparation.s_____.

7 n9 were immeilntely begun to shut (Fown the reactor. At 1135 hours0.0131 days <br />0.315 hours <br />0.00188 weeks <br />4.318675e-4 months <br />, plant shutdown t

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. OYSTER CREEK NUCLEAR GENERATING STATION Forked River, New Jersey 08731 Licensco Event Report Reportabic Occurrence No. 50-219/76-31-1T Report Date January 3, 1977 Occurrence Date December 22, 1976 Identification of Occurrence Violation of the Technical Specifications, Section 3.6. A.3 when the radio gases released from the stack were not continuously monitored. This event is considered to be a reportable occurrence as defined in the Technical Specifi-cations, paragraph 6.9.2.A.2.

Conditions Prior to Occurrence The plant was at steady state power with the following major parameters:

Power: Reactor, 1706 MWt Generator, 586 MNe Flow: Recirculation, 59.1 x 106 lb/hr Feedwater, 6.3 x 10 6 lb/hr Stack Gas: 14,000 pci/sec Description of Occurrence On Wednesday, December 22, 1976, at approximately 0700 hours0.0081 days <br />0.194 hours <br />0.00116 weeks <br />2.6635e-4 months <br />, a " Stack Gas Low Flow" alarm sounded in the Station Control Room. The alarm is set to trip at 1 SCFil and is usually associated with the need to change out the stack gas sample filters. Accordingly, a technician was dispatched and-the filters were changed. The stack gas sampic system flow returned to normal and the low flow alarm cleared. Some erratic flow was observed during the next three hours of operation but it should be noted that the system was still considered operable during this time since the monitoring system is not highly dependent upon flow. In addition, the Control Room Operators were instructed to pay particular attention to the off gas and area radiation monitors for any evidence of increase. The condition worsened and at 1045 hours0.0121 days <br />0.29 hours <br />0.00173 weeks <br />3.976225e-4 months <br />, the stack gas sampic system was declared inoperable and preparations were immediately begun to shut down the reactor. At 1135 hours0.0131 days <br />0.315 hours <br />0.00188 weeks <br />4.318675e-4 months <br />, plant shutdown commenced at a rate of 100 MXe/hr. The cause of the failure was traced to an ice plug which formed in the sample line. The ice plug was melted using an external heat source and the stack gas sample system was returned to service at 1317 hours0.0152 days <br />0.366 hours <br />0.00218 weeks <br />5.011185e-4 months <br /> and the plant shutdown was terminated at 1322 hours0.0153 days <br />0.367 hours <br />0.00219 weeks <br />5.03021e-4 months <br />.

Reportabic Occurrence No. 50-219/76- 31-1T 2 :.uary 3, 1977 Page 2 Apparent Cause of Occurrence The ice plug formed as the result of a failure in the heat tracing on the sample line.

Analysis of Occurrence The safety significance of this event is considered to be minimal since during the 152-minute period the sample system was inoperable, no increases were noted in off gas activity or in area radiation monitor readings. Furthermore, when returned to service, the stack gas monitors indicated the same as they did before the failure. It can, therefore, be concluded that the radio gases emitted from the stack were stable and constant during the period of inoperability.

Corrective Action The heat tracing was replaced and the sample line was reinsulated. The installation of an ammeter, which will provide positive indication of the heat tracing operability, will be investigated.

Failure Data N/A

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