Event Notification Report for November 28, 2010
U.S. Nuclear Regulatory Commission
Operations Center
EVENT REPORTS FOR
11/27/2010 - 11/28/2010
EVENT NUMBERS
46441
Power Reactor
Event Number: 46441
Facility: MILLSTONE
Region: 1 State: CT
Unit: [] [2] []
RX Type: [1] GE-3,[2] CE,[3] W-4-LP
NRC Notified By: RICHARD VIGNEAU
HQ OPS Officer: HOWIE CROUCH
Region: 1 State: CT
Unit: [] [2] []
RX Type: [1] GE-3,[2] CE,[3] W-4-LP
NRC Notified By: RICHARD VIGNEAU
HQ OPS Officer: HOWIE CROUCH
Notification Date: 11/28/2010
Notification Time: 17:27 [ET]
Event Date: 11/28/2010
Event Time: 15:15 [EST]
Last Update Date: 11/28/2010
Notification Time: 17:27 [ET]
Event Date: 11/28/2010
Event Time: 15:15 [EST]
Last Update Date: 11/28/2010
Emergency Class: NON EMERGENCY
10 CFR Section:
50.72(b)(2)(iv)(B) - RPS ACTUATION - CRITICAL 50.72(b)(3)(iv)(A) - VALID SPECIF SYS ACTUATION
10 CFR Section:
50.72(b)(2)(iv)(B) - RPS ACTUATION - CRITICAL 50.72(b)(3)(iv)(A) - VALID SPECIF SYS ACTUATION
Person (Organization):
DON JACKSON (R1DO)
DON JACKSON (R1DO)
| Unit | SCRAM Code | RX Crit | Initial PWR | Initial RX Mode | Current PWR | Current RX Mode |
|---|---|---|---|---|---|---|
| 2 | A/R | Y | 100 | Power Operation | 0 | Hot Standby |
AUTOMATIC REACTOR TRIP AFTER TURBINE TRIP DUE TO LOSS OF CONDENSER VACUUM
"Loss of two circulating water pumps in one condenser caused a high main condenser backpressure. The high main condenser back pressure caused an automatic main turbine and reactor trip while critical >15%.
"Low steam generator water level following the trip caused an automatic Auxiliary Feedwater actuation. The low water level condition has cleared. Normal post-trip response has been verified and the plant is stable."
The licensee removed one circulating water pump from service in preparation of performing scheduled maintenance when the other circulator unexpectedly tripped. The cause of the pump trip is under investigation. During the trip, all rods inserted into the core. There were no primary safety valves that lifted during the transient but main steam safeties "chattered" during the transient and have fully reseated. There is no known primary to secondary leakage. The electrical grid is stable and supplying plant loads in a normal shutdown electrical lineup. The reactor is stable at normal operating pressure and temperature with decay heat being removed via the steam dumps to condenser.
The licensee has notified the State of Connecticut Department of Environmental Protection, the town of Waterford, CT, and the NRC Resident Inspector.
"Loss of two circulating water pumps in one condenser caused a high main condenser backpressure. The high main condenser back pressure caused an automatic main turbine and reactor trip while critical >15%.
"Low steam generator water level following the trip caused an automatic Auxiliary Feedwater actuation. The low water level condition has cleared. Normal post-trip response has been verified and the plant is stable."
The licensee removed one circulating water pump from service in preparation of performing scheduled maintenance when the other circulator unexpectedly tripped. The cause of the pump trip is under investigation. During the trip, all rods inserted into the core. There were no primary safety valves that lifted during the transient but main steam safeties "chattered" during the transient and have fully reseated. There is no known primary to secondary leakage. The electrical grid is stable and supplying plant loads in a normal shutdown electrical lineup. The reactor is stable at normal operating pressure and temperature with decay heat being removed via the steam dumps to condenser.
The licensee has notified the State of Connecticut Department of Environmental Protection, the town of Waterford, CT, and the NRC Resident Inspector.