ML20055B773
| ML20055B773 | |
| Person / Time | |
|---|---|
| Site: | Trojan File:Portland General Electric icon.png |
| Issue date: | 07/01/1982 |
| From: | PORTLAND GENERAL ELECTRIC CO. |
| To: | |
| Shared Package | |
| ML20055B771 | List: |
| References | |
| RO-82-01, RO-82-1, NUDOCS 8207230287 | |
| Download: ML20055B773 (3) | |
Text
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Trojnn Nuclesr Pltnt R. H. Engelk:n Dock 2t 50-344 July 2, 1982 License NPF-1 Page 1 of 3 REPORTABLE OCCURRENCE TROJAN NUCLEAR PLANT 1.
Report No.:
82-01, Revision 2.
2.
Report date:
a.
Original report: January 30, 1982.
b.
Revision 1 report: February 12, 1982.
c.
Current report: July 1, 1982.
3.
Occurrence date: January 16, 1982.
(Identification of Occurrences) 4.
Facility: Trojan Nuclear Plant P. O. Box 439 Rainier, Oregon 97048.
5.
Identification of Occurrence:
An engineering investigation determined on January 16, 1982 that the "B" (east) emergency desel generator (EDC) is inoperable when 120V AC Preferred Instrument Bus Y24 is supplied from Nonpreferred Instrument Bus YO2. A review of Plant records shows that from November 8, 1981 through November 12, 1981 (a total of 87 hours0.00101 days <br />0.0242 hours <br />1.438492e-4 weeks <br />3.31035e-5 months <br />) and from December 1, 1981 through January 4, 1982 (a total of 34 days and 3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br />), power to Y24 was supplied by YO2, rendering the "B" EDG inoperable. In addition, both EDGs were inoperable for 9-1/2 hours on December 8, 1981 and for 5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> on January 4, 1982. The appropriate action statements required by Technical Specifications 3.8.1.1, Action a, 4.8.1.1.a, and 4.8.1.1.a.5 were not implemented during those periods.
l 6.
Conditions prior to occurrence:
f The Plant was in Mode 3, Hot Standby, when this event was discovered.
During the periods when the "B" EDG was inoperable, the Plant was in Mode 1, Power Operation, at 100 percent power generation.
7.
Description of Occurrence:
Each preferred 120V AC instrument bus (Yll, Y13 for "A" train and Y22, Y24 for "B" train) is normally powered from its own static inverter, which uses either 120V AC or 125V DC input; however, if its inverter is out of service, each preferred bus may be powered from a nonpreferred 120V AC bus (Y01 for "A" train and YO2 for "B" train).
8207230287 820702 PDR ADOCK 05000344 l
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Trojtn Nuclear Plint R. H. Engalk:n
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Docket 50-344 July 2, 1982 License NPF-1 Page 2 of 3 On May 30,1977, it was determit.ed that the "B" EDG is inoperable when 120V AC Preferred Instrument Bus Y24 Is powered from its alternate source (YO2). A standing order was issued, alerting the operators to declare either EDG out of service when any one of the four 120V AC Preferred Instrument Buses were powered from their alternate sources. Also, a Request for Design Change (RDC 77-093) was issued to modify the design.
In 1980, a Training Information bulletin was issued which improperly identified 120V AC Preferred Instrument Bus Y22 as the bus impact-ing the operability of "B" EDC.
Bus Y24 provides power to the circuitry which serves to protect the "B" EDG in the event that EDG is supplying power to its associated bus at the time of the turbine l
trip. This circuitry is designed to protect the EDG from excessive loading by momentarily tripping the EDG output breaker following the main turbine trip. If Y24 is powered by a nonpreferred bus, the protective circuitry locks into a tripping mode; each time the EDG output breaker is closed, the circuitry trips the breaker again.
Therefore, to maintain "B" EDG in an operable condition, Y24 must be energized from its inverter that has battery backup. It was also determined that supplying Bus Y22 from its alternate power source renders the "B" EDG inoperable because the automatic start relay and generator output circuit breaker automatic close relay are powered from Y22. For the "A" EDG, all of the above protection and controls are supplied by Preferred Instrument Bus Y11.
A review of Plant records indicates the "B" EDG was inoperable due to Preferred Instrument Bus Y24 inverter problems for 34 days from December 1, 1981 until January 4, 1982 and for 87 hours0.00101 days <br />0.0242 hours <br />1.438492e-4 weeks <br />3.31035e-5 months <br /> from Novem-ber 8, 1981 to November 12, 1981. This resulted in operation which was less conservative than the least conservative aspects of the limiting condition for operation established in Technical Specifi-cation 3.8.1.
It was further determined that both EDGs were inoperable for 9-1/2 hours on December 8, 1981 and for 5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> on January 4, 1982.
8.
Designation of apparent cause of occurrence:
The occurrence resulted because erroneous information was used as a basis for incorrectly revising a Standing Order.
9.
Significance of Occurrence:
This event had no effect on either Plant or public safety. The Plant was never in a condition requiring the EDGs to start and I
provide emergency power while the "B" EDG was inoperable. In the event that the EDGs were necessary, manual action could have been taken to close the output breaker on the "B" EDC.
Trojan Nuclear Plant R. H. Engnik:n Dockst 50-344 July 2, 1982 License NPF-1 Page 3 of 3 10.
Corrective Action:
The correct information identifying which Preferred Instrument Buses affect operation of the "B" EDG has been documented in a Standing Order. RDC 82-13 was completed during the 1982 refueling outage.
This design change allows the EDGs to remain operable independent of the failure of any 120 VAC Preferred Instrument Bus. The appropri-ate power supplies to the circuit breaker control and protection are now powered from the respective train DC buses.
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