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At 23:55 on 5/12/16, Unit 2 experienced an … At 23:55 on 5/12/16, Unit 2 experienced an electrical transient resulting in a loss of 2B246 Reactor Building Engineered Safeguard System (ESS) Division 480 volt Motor Control Center (MCC) and 2Y246 208/120 Volt Alternate Current (AC) Instrument Panel. With the loss of the Reactor Building ESS Division 480 volt MCC, was manually scrammed. All rods inserted as expected. Reactor water level lowered to -27 inches and was immediately restored by normal feedwater level control. Level 3 (+13 inch) Primary Containment Isolation System (PCIS) isolations occurred, along with an initiation of the Reactor Core Isolation Cooling (RCIC).</br></br>The direct cause of the transient was found to be a phase to ground short between a cable and a protruding screw in MCC bucket 2B246091, Drywell Area Unit Cooler 2V411B Breaker. The apparent cause is the vendor did not comply with Specification E1116, Rev 3 with this order of buckets. Immediate corrective actions included the repair of 2B246 which has been completed. A plan has been developed to review a sample of the 480 VAC MCC breakers and is being tracked by maintenance and system engineering.ked by maintenance and system engineering. +
At 23:55 on 5/12/16, Unit 2 experienced an … At 23:55 on 5/12/16, Unit 2 experienced an electrical transient resulting in a loss of 2B246 Reactor Building Engineered Safeguard System (ESS) Division 480 volt Motor Control Center (MCC) and 2Y246 208/120 Volt Alternate Current (AC) Instrument Panel. With the loss of the Reactor Building ESS Division 480 volt MCC, was manually scrammed. All rods inserted as expected. Reactor water level lowered to -27 inches and was immediately restored by normal feedwater level control. Level 3 (+13 inch) Primary Containment Isolation System (PCIS) isolations occurred, along with an initiation of the Reactor Core Isolation Cooling (RCIC).</br></br>The direct cause of the transient was found to be a phase to ground short between a cable and a protruding screw in MCC bucket 2B246091, Drywell Area Unit Cooler 2V411B Breaker. The apparent cause is the vendor did not comply with Specification E1116, Rev 3 with this order of buckets. Immediate corrective actions included the repair of 2B246 which has been completed. A plan has been developed to review a sample of the 480 VAC MCC breakers and is being tracked by maintenance and system engineering.ked by maintenance and system engineering. +
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