05000219/LER-2003-002
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| 2192003002R00 - NRC Website | |
DATE OF OCCURRENCE
This event occurred on May 20. 2003
IDENTIFICATION OF OCCURRENCE
An electrical fault on an underground cable IBS Component CBL5) between the output breaker of Diesel Generator.1 (En_ Code 13G) and the 4160 VAC (Volts Alternating Current) bus 1C (EllS Component BU) caused bus 1C to lockout Power to
- Safety Related equipment fed from bus 1C was unavailable. Technical Specifications required the plant to be placed hi the cold shutdown condition. Completion of the shutdown is reportable UMW 10 CFR 60.73(aX2X0(A).
CONDITIONS PRIOR TO OCCURRENCE
The plant was operating at approximately 100% power with all reactor plant pressures and temperatures normal for full power operation. All safety-related equipment was operable.
DESCRIPTION OF OCCURRENCE
On May 20, 2003, at 0030 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />, power to the 4160 VAC bus 1C was lost when breaker 1C tripped and locked out due to a ground fault. Lockout of the faulted bus prevented Diesel Generator 1 from starting and re-energizing bus 1C. The loss of power to bus IC de-energized one division of safety-related equipment, Including Reactor Protection System 1, Core Spray Main and Booster Pumps A and 13, Containment Spray and Emergency Service Water pumps A and B, Standby Gas Treatment System 1, and related equipment. The other division of safety-related equipment was powered from bus 1D which remained energized and operable. The loss of power to Reactor Protection System I caused a half-scram. No other safety systems were required to actuate and no spurious actuations occurred.
After the bus fault, the plant remained at full power with normal operating reactor temperature, pressure, and water level. The loss of power to bus 1C caused entry into several Limiting Conditions for Operation, the most limiting of which was to be in the SHUTDOWN CONDITION within 12-hours due to loss of ability to monitor Primary Containment Identified and Unidentified Leak Rates. After making preparations, reactor power was reduced and a planned reactor scram was manually Initiated at 0943 hours0.0109 days <br />0.262 hours <br />0.00156 weeks <br />3.588115e-4 months <br />.
At 1134 hours0.0131 days <br />0.315 hours <br />0.00187 weeks <br />4.31487e-4 months <br />, the Unit Substation providing power to safety-related equipment was re-energized from the other division.
The next most limiting LCO was to be In the COLD SHUTDOWN CONDITION within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> due to Inoperability of various primary contali � anent -Isolation valves. -Rant cvoldowrrwas began at 0954 hours0.011 days <br />0.265 hours <br />0.00158 weeks <br />3.62997e-4 months <br /> and the COLD SHUTDOWN CONDrIK*1 was - reached at 1913 hours0.0221 days <br />0.531 hours <br />0.00316 weeks <br />7.278965e-4 months <br />. At 2040 hours0.0236 days <br />0.567 hours <br />0.00337 weeks <br />7.7622e-4 months <br />, the Unit Substation providing power to loads In the Turbine Building was re-energized from the other division. At 0411 hours0.00476 days <br />0.114 hours <br />6.795635e-4 weeks <br />1.563855e-4 months <br /> on May 21, 2003. the remaining Unit Substation was re-energized from the other &vision.
APPARENT CAUSE
The reactor shutdown was completed to satisfy Technical Specification Limiting Conditions for Operation due to the equipment made inoperable by the loss of power to 4160 VAC bus 1C. The loss of power was caused by an electrical faun on bus IC, specifically in a power feeder cable between the output breaker of Diesel Generator 1 and 4160 VAC bus 1C. The cable was a shielded power cable, type MV93, manufactured by Anaconda circa 1977 with ethylene propylene insulation and chlorinated polyethylene Jacket. Previous experience with this type of cable has been that the manufacturing process had a potential for Insulation defects and the presence of water accelerated cable degradation at any defect in the insulation.
PRC FORM }NA � y Oyster Creek Unit 1 � 105000 219
ANALYSIS OF OCCURRENCE AND SAFETY ASSESSMENT
The safety significance of this event is considered minimal. Power remained available to the redundant trains of safety-related equipment from 4160 VAC bus 10. The plant remained within Technical Specification limits at all times. The SHUTDOWN and COLD SHUTDOWN conditions were achieved within the allowed time limits. There was no radioactive release, nor any effect on the health and safety of the public.
CORRECTIVE ACTIONS
immediate Actions The plant was stabilized, brought to a shutdown condition as required by Technical Specifications, and placed In the cold shutdown condition as required by Technical Specifications.
Short Perm Cables between Diesel Generator 1 and bus 1C were replaced with cables of a different manufacture prior to startup.
The faulted section of the cable was recovered and sent to a laboratory for analysis.
An Extent of Condition review was completed. The review found that a Roof Cause Analysis after a similar cable fault In 2001 had Incorrectly Identified the cable type installed In this run. Therefore, the review was expanded to include physical verification that the type of cable installed between Diesel Generator 2 and bus 1D was not the same type that failed and confirmation that all of the buried cable powering safety-related equipment was not the same type that failed.
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