ML19317E045
| ML19317E045 | |
| Person / Time | |
|---|---|
| Site: | Oconee  |
| Issue date: | 01/26/1978 |
| From: | DUKE POWER CO. |
| To: | |
| Shared Package | |
| ML19317E043 | List: |
| References | |
| RO-269-77-31, NUDOCS 7912110823 | |
| Download: ML19317E045 (2) | |
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DUKE POWER COMPANY
'f OCONET UNIT 1 Report No.: 'RO-269/77-31 Report Date:
January 26,'1978 g.
j-i occurrence Date: Dheember 29, 1977
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Facility:
Oconee Uniti, Seneca, South Carolina IdentificationofOccurrgee: RCS Pressure Channel Inoperable Conditions' Prior to Ocet ence:
90 percent full power Description of Occurrence:
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On December 27, 1977, unidentified Reactor Coolant System leakage of less than 1 gpm was detected. At 2131 RPS Channel A tripped on low pressure /
temperature and was placed in manual bypass. At 0200 on December 28 the previously detected leak was determined to be coming from the area of
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Engineered Safeguard' Channel 1and RPS Channel A Pressure Transmitter.
A reactor shutdown was initiated at-0209 due to high Reactor Building (RB) activity.
At 0600 personnel entered the RB and determined that pressure switch 1 PS-364 was leaking and valved it out.
Reactor power reduction was stopped at 39 percent full power and with the isolation of 1PS-364, RPS Channel A.was returned to service..
At 2400 during PT/l&2/0600/01, it was determined that RC Loop A wide range (WR) pressure was indicating high.
Further investigation determined that ES Analog Channel 1 WR pressure was indicating high and would not trip at required setpoints.
ES Analog Channel 1 was placed in trip condition.
Pressure transmitter IPT-21P, which is located approximately 5 feet from and slightly below IPS-364 was recalibrated and ES Analog Channel 1 was returned to service.
Apparent Cause of Occurrence:
The diaphragm of pres.sure switch IPS-364 evidently failed as steam was seen blowing from the switch. This failure caused RPS Channel A to trip.
The steam f, rom the switch failure evidently impacted on and shifted the zero setting of pressure transmitter IPT-21P. The zero shift caused the high reading-on ES Analog Channel 1.
Analysir'of Occurrence:
-Pressure switch 1PS-364 provides a signal to prevent valves LP-1, -2 from opening with RCS pressure greater than 400 psig. The failed diaphragm caused RPS Channel A to trip. RPS Channels B, C & D remained fully opera-tional during-the incident as required by Technical Specifications 3.5.1.
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Valves LP-1, -2 had been tagged shut prior to this incident..
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- The zero:setpoint of pressure. transmitter 1PT-21P shifted when it was-heated.by steam from the switch failure.
ES Analog Channel 1 which
,provides a signal-for LPI and EPI initiation became inoperable, however, channels l2 and 3 remained fully operational as required by Technical Specification 3.5.1.
TheLhealth and safety of-the public were not endangered'by this incident.
. Corrective Action:
Pressure' switch 1PS-364 is presently valved out and will be replaced during a^ future outage.. Pressure transmitter'1PT-11P was~recalibrated and returned to service.
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