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At 16:35 on April 21, 2004 with Unit 1 in … At 16:35 on April 21, 2004 with Unit 1 in Mode 1 at 17% power, Susquehanna Unit 1 was manually scrammed in response to main turbine bearing high vibrations experienced during startup turbine testing. The turbine had been replaced during the recently completed Unit 1 refueling outage. After approximately 35 minutes of turbine operation at 1800 rpm and no load, a rub developed in the vicinity of bearing #2. Vibration increased to levels warranting turbine trip as directed by operating procedure.</br></br>Despite the turbine trip, the rub continued to cause localized heating thus creating a rotor bow condition and a steady vibration increase. The Reactor Protection System was manually initiated and condenser vacuum was broken to allow for a more rapid decrease in turbine speed and, subsequently, vibration levels. Plant response to the manual reactor scram was in accordance with design. Causes cited for this event include: (1) Turbine startup vibration trip limits were not set sufficiently low to preclude rub induced high vibration (2) Vibration change rates were not monitored and used as a response input to high vibration conditions and (3) Project management did not establish contingency plans in sufficient depth to handle all potential vibration issues. After implementing corrective actions to address these deficiencies and performing a thorough evaluation to ensure equipment had not been adversely impacted by the high vibration, the turbine was successfully started and loaded in accordance with the established startup procedure. The manual RPS actuation and the subsequent manual initiation of the Reactor Core Isolation Cooling system, to assist with reactor level control, are unplanned actuations of systems that mitigate the consequences of significant events and are, therefore, being reported per 10CRF50.73(a)(2)(iv)(A). There were no actual adverse consequences to the fuel, any plant equipment, or to the health and safety of the public as a result of this event.y of the public as a result of this event.
At 16:35 on April 21, 2004 with Unit 1 in … At 16:35 on April 21, 2004 with Unit 1 in Mode 1 at 17% power, Susquehanna Unit 1 was manually scrammed in response to main turbine bearing high vibrations experienced during startup turbine testing. The turbine had been replaced during the recently completed Unit 1 refueling outage. After approximately 35 minutes of turbine operation at 1800 rpm and no load, a rub developed in the vicinity of bearing #2. Vibration increased to levels warranting turbine trip as directed by operating procedure.</br></br>Despite the turbine trip, the rub continued to cause localized heating thus creating a rotor bow condition and a steady vibration increase. The Reactor Protection System was manually initiated and condenser vacuum was broken to allow for a more rapid decrease in turbine speed and, subsequently, vibration levels. Plant response to the manual reactor scram was in accordance with design. Causes cited for this event include: (1) Turbine startup vibration trip limits were not set sufficiently low to preclude rub induced high vibration (2) Vibration change rates were not monitored and used as a response input to high vibration conditions and (3) Project management did not establish contingency plans in sufficient depth to handle all potential vibration issues. After implementing corrective actions to address these deficiencies and performing a thorough evaluation to ensure equipment had not been adversely impacted by the high vibration, the turbine was successfully started and loaded in accordance with the established startup procedure. The manual RPS actuation and the subsequent manual initiation of the Reactor Core Isolation Cooling system, to assist with reactor level control, are unplanned actuations of systems that mitigate the consequences of significant events and are, therefore, being reported per 10CRF50.73(a)(2)(iv)(A). There were no actual adverse consequences to the fuel, any plant equipment, or to the health and safety of the public as a result of this event.y of the public as a result of this event.
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