Event Notification Report for December 06, 2014
U.S. Nuclear Regulatory Commission
Operations Center
EVENT REPORTS FOR
12/05/2014 - 12/06/2014
EVENT NUMBERS
50774
Power Reactor
Event Number: 50774
Facility: RIVER BEND
Region: 4 State: LA
Unit: [1] [] []
RX Type: [1] GE-6
NRC Notified By: MICHAEL BRANSCUM
HQ OPS Officer: JOHN SHOEMAKER
Region: 4 State: LA
Unit: [1] [] []
RX Type: [1] GE-6
NRC Notified By: MICHAEL BRANSCUM
HQ OPS Officer: JOHN SHOEMAKER
Notification Date: 01/28/2015
Notification Time: 13:50 [ET]
Event Date: 12/06/2014
Event Time: 10:12 [CST]
Last Update Date: 01/28/2015
Notification Time: 13:50 [ET]
Event Date: 12/06/2014
Event Time: 10:12 [CST]
Last Update Date: 01/28/2015
Emergency Class: NON EMERGENCY
10 CFR Section:
50.73(a)(1) - INVALID SPECIF SYSTEM ACTUATION
10 CFR Section:
50.73(a)(1) - INVALID SPECIF SYSTEM ACTUATION
Person (Organization):
MICHAEL VASQUEZ (R4DO)
MICHAEL VASQUEZ (R4DO)
| Unit | SCRAM Code | RX Crit | Initial PWR | Initial RX Mode | Current PWR | Current RX Mode |
|---|---|---|---|---|---|---|
| 1 | N | Y | 100 | Power Operation | 100 | Power Operation |
60 DAY OPTIONAL REPORT - HALF SCRAM AND A DIVISION 2 PRIMARY CONTAINMENT ISOLATION SIGNAL
"On December 6, 2014, at approximately 1012 CST, while the plant was operating at 100 percent power, the Division 2 reactor protection system (RPS) bus de-energized unexpectedly. This resulted in a half-scram and a Division 2 primary containment isolation signal. Operators executed the appropriate abnormal operating procedures to begin an orderly restoration of the affected systems. Atmospheric pressure in the primary containment momentarily reached the high-pressure alarm setpoint, necessitating entry into the emergency operating procedure for that condition.
"Automatic isolation valves in the following systems closed as designed:
- reactor plant component cooling water
- drywell unit cooler water supply
- reactor building floor and equipment drains
- reactor building HVAC chilled water supply
- containment airlock seal air supply
- reactor recirculation system flow control valve hydraulics
- main steam line drains
- reactor water cleanup
- auxiliary building and annulus HVAC systems
"These engineered safety systems actuated as designed:
- standby gas control filter trains
- fuel building filter trains
- control building filter trains
"The event occurred approximately 25 hours after the Division 2 RPS motor-generator (MG) was aligned to the bus following replacement of the voltage regulator. Following the event, the MG set was found running with its output breaker tripped.
"A failure analysis determined that the spike suppressor and the field flash card were potential sources of the MG breaker trip. The spike suppressor was replaced. Inspection of the field flash card found a strand of wire from one of the attached leads nearly touching a trace on the circuit board. Testing determined that the wire strand was the most likely cause for the breaker trip. With no spare card readily available, the wire strand was removed and the field flash card was re-installed. Other cards were inspected, and no similar conditions were found. The MG set was load tested for 30 hours, and was placed in service on December 17[, 2014].
"Additionally, it is suspected that there is an intermittent failure occurring in the field flash card. A design change will be developed to correct that condition."
The licensee has notified the NRC Resident Inspector.
"On December 6, 2014, at approximately 1012 CST, while the plant was operating at 100 percent power, the Division 2 reactor protection system (RPS) bus de-energized unexpectedly. This resulted in a half-scram and a Division 2 primary containment isolation signal. Operators executed the appropriate abnormal operating procedures to begin an orderly restoration of the affected systems. Atmospheric pressure in the primary containment momentarily reached the high-pressure alarm setpoint, necessitating entry into the emergency operating procedure for that condition.
"Automatic isolation valves in the following systems closed as designed:
- reactor plant component cooling water
- drywell unit cooler water supply
- reactor building floor and equipment drains
- reactor building HVAC chilled water supply
- containment airlock seal air supply
- reactor recirculation system flow control valve hydraulics
- main steam line drains
- reactor water cleanup
- auxiliary building and annulus HVAC systems
"These engineered safety systems actuated as designed:
- standby gas control filter trains
- fuel building filter trains
- control building filter trains
"The event occurred approximately 25 hours after the Division 2 RPS motor-generator (MG) was aligned to the bus following replacement of the voltage regulator. Following the event, the MG set was found running with its output breaker tripped.
"A failure analysis determined that the spike suppressor and the field flash card were potential sources of the MG breaker trip. The spike suppressor was replaced. Inspection of the field flash card found a strand of wire from one of the attached leads nearly touching a trace on the circuit board. Testing determined that the wire strand was the most likely cause for the breaker trip. With no spare card readily available, the wire strand was removed and the field flash card was re-installed. Other cards were inspected, and no similar conditions were found. The MG set was load tested for 30 hours, and was placed in service on December 17[, 2014].
"Additionally, it is suspected that there is an intermittent failure occurring in the field flash card. A design change will be developed to correct that condition."
The licensee has notified the NRC Resident Inspector.