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On May 5, 2004, at 1327 hours (CDT), with … On May 5, 2004, at 1327 hours (CDT), with Unit 3 at 100 percent power in Mode 1, an automatic scram occurred due to a Main Generator Load Reject when a loss of offsite power occurred. The Emergency Diesel Generators automatically started and powered their respective electrical busses. All control rods fully inserted and Group I, II and III isolations occurred as expected. Operations personnel manually initiated the Isolation Condenser System for reactor pressure control, the High Pressure Coolant Injection System for reactor water level control, and the Low Pressure Coolant Injection System for Torus cooling. All systems initially responded to the scram as expected except the Standby Gas Treatment System was unable to maintain the Secondary Containment at the Technical Specification Surveillance Requirement limit of greater than or equal to 0.25 inches of vacuum water gauge. An Unusual Event for the loss of offsite power was declared at 1342 hours (CDT) and terminated at 1601 hours (CDT) on May 5, 2004. Additionally, during restoration of offsite electrical power to Bus 33, the Emergency Diesel Generator 2/3 output electrical breaker tripped.</br></br>The root causes associated with the load reject and loss of offsite power and the low Secondary Containment vacuum were respectively, equipment failure in the "C" phase of the 345 kilovolt circuit breaker 8-15 and a degraded Secondary Containment boundary not detected due to an inadequate leak rate test procedure. The investigation into the apparent cause of the Emergency Diesel Generator output breaker trip was indeterminate.</br></br>NRC FORM 366A� U.S. NUCLEAR REGULATORY COMMISSION (7-2001) Dresden Nuclear Power Station Unit 3 05000249 NUMBER NUMBERower Station Unit 3 05000249 NUMBER NUMBER +
May 5, 2004 +
On May 5, 2004, at 1327 hours (CDT), with … On May 5, 2004, at 1327 hours (CDT), with Unit 3 at 100 percent power in Mode 1, an automatic scram occurred due to a Main Generator Load Reject when a loss of offsite power occurred. The Emergency Diesel Generators automatically started and powered their respective electrical busses. All control rods fully inserted and Group I, II and III isolations occurred as expected. Operations personnel manually initiated the Isolation Condenser System for reactor pressure control, the High Pressure Coolant Injection System for reactor water level control, and the Low Pressure Coolant Injection System for Torus cooling. All systems initially responded to the scram as expected except the Standby Gas Treatment System was unable to maintain the Secondary Containment at the Technical Specification Surveillance Requirement limit of greater than or equal to 0.25 inches of vacuum water gauge. An Unusual Event for the loss of offsite power was declared at 1342 hours (CDT) and terminated at 1601 hours (CDT) on May 5, 2004. Additionally, during restoration of offsite electrical power to Bus 33, the Emergency Diesel Generator 2/3 output electrical breaker tripped.</br></br>The root causes associated with the load reject and loss of offsite power and the low Secondary Containment vacuum were respectively, equipment failure in the "C" phase of the 345 kilovolt circuit breaker 8-15 and a degraded Secondary Containment boundary not detected due to an inadequate leak rate test procedure. The investigation into the apparent cause of the Emergency Diesel Generator output breaker trip was indeterminate.</br></br>NRC FORM 366A� U.S. NUCLEAR REGULATORY COMMISSION (7-2001) Dresden Nuclear Power Station Unit 3 05000249 NUMBER NUMBERower Station Unit 3 05000249 NUMBER NUMBER +
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3 +
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15:12:17, 27 November 2017 +
October 29, 2004 +
May 5, 2004 +
UUnit 3 Scram Due to Loss of Offsite Power and Subsequent Inoperability of the Standby Gas Treatment System for Units 2 and 3 +
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