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On 10/26/2001 at 1917 EDT, Unit 2 was in t … On 10/26/2001 at 1917 EDT, Unit 2 was in the Run mode. At that time, the reactor scrammed on Average Power Range Monitor high neutron flux caused by a rapid increase, after an unexpected decrease, in the flow rate of the 2B reactor recirculation pump. Following the scram, water level decreased due to void collapse from the rapid reduction in power resulting in closure of Group 2 and Group 5 primary containment isolation valves and automatic initiation of the Reactor Core Isolation Cooling and High Pressure Coolant Injection systems. The low level initiation signal cleared before either system could inject water to the vessel. The secondary containment dampers automatically isolated and all trains of the Unit 1 and Unit 2 Standby Gas Treatment systems automatically started on low water level. Level reached a minimum of 40 inches below instrument zero. The Reactor Feedwater Pumps restored level to its pre-event value of approximately 35 inches above instrument zero within 35 seconds of the scram. Reactor vessel pressure did not exceed its normal value of approximately 1035 psig; therefore, no safety/relief valves lifted nor were any required to lift to reduce pressure.</br></br>The cause of this event is not known conclusively, although the available evidence indicates a problem with the amplifier board in the 2B reactor recirculation pump scoop tube positioner logic circuit is the most likely cause.</br></br>Corrective actions include replacing the amplifier board; temporarily requiring the 2B recirculation pump scoop tube to be locked when pump speed is not being changed; monitoring selected parameters in the pump speed control system; and performing a failure analysis of the amplifier board.a failure analysis of the amplifier board. +
October 26, 2001 +
On 10/26/2001 at 1917 EDT, Unit 2 was in t … On 10/26/2001 at 1917 EDT, Unit 2 was in the Run mode. At that time, the reactor scrammed on Average Power Range Monitor high neutron flux caused by a rapid increase, after an unexpected decrease, in the flow rate of the 2B reactor recirculation pump. Following the scram, water level decreased due to void collapse from the rapid reduction in power resulting in closure of Group 2 and Group 5 primary containment isolation valves and automatic initiation of the Reactor Core Isolation Cooling and High Pressure Coolant Injection systems. The low level initiation signal cleared before either system could inject water to the vessel. The secondary containment dampers automatically isolated and all trains of the Unit 1 and Unit 2 Standby Gas Treatment systems automatically started on low water level. Level reached a minimum of 40 inches below instrument zero. The Reactor Feedwater Pumps restored level to its pre-event value of approximately 35 inches above instrument zero within 35 seconds of the scram. Reactor vessel pressure did not exceed its normal value of approximately 1035 psig; therefore, no safety/relief valves lifted nor were any required to lift to reduce pressure.</br></br>The cause of this event is not known conclusively, although the available evidence indicates a problem with the amplifier board in the 2B reactor recirculation pump scoop tube positioner logic circuit is the most likely cause.</br></br>Corrective actions include replacing the amplifier board; temporarily requiring the 2B recirculation pump scoop tube to be locked when pump speed is not being changed; monitoring selected parameters in the pump speed control system; and performing a failure analysis of the amplifier board.a failure analysis of the amplifier board. +
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05:01:49, 1 December 2017 +
December 14, 2001 +
October 26, 2001 +
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