05000397/LER-2013-005
| Columbia Generating Station | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(iv)(A), System Actuation |
| Initial Reporting | |
| ENS 49120 | 10 CFR 50.72(b)(3)(iv)(A), System Actuation |
| 3972013005R00 - NRC Website | |
MONTH DAY YEAR
On 6/15/2013 at 1222 PDT Columbia Generating Station was in a refueling outage in Mode 4 when valid Essential Safety Function (ESF) actuation signals of Division .1 and 2 Emergency Diesel Generators were Division 1 and 2 Essential Service Water System pumps were also received due to the start of Division 1 and 2 Emergency Diesel Generators. The 4.16kV Division 1 and 2 critical switchgear buses were de-energized resulting in load shed of several systems and an invalid actuation of containment isolation valves for multiple systems. Power to the 4.16kV critical switchgear was automatically restored by the Emergency Diesel Generators.
Plant systems which had been load shed were returned to operating status, The 4.16kV critical switchgear buses were subsequently realigned to an offsite power source.
The momentary loss of the 115kV offsite power source was due to relays opening and reciosing to clear a line fault associated with a range fire under the transmission line.
- 26158 R5'
PLANT CONDITIONS
At the time of event, the plant was in a refueling outage in Mode 4 at 0% power with all rods in. In preparation for heating up the reactor to support the Reactor Pressure Vessel hydro surveillance test, shutdown cooling had been secured and Residual Heat Removal (RHR) pump "C" had been started in Suppression Pod mixing. Due to recently performed testing on the 230kV Startup Transformer [XMFRJ, the 4.16kV Division 1 and 2 critical switchgear buses [BUJ were powered from the 115kV offsite power source through the Backup Transformer [XFMR).
EVENT DESCRIPTION
On 6/15/2013 at 1222 PDT Columbia Generating Station (Columbia) received valid Essential Safety Function (ESF) [JEJ actuation signals of Division 1 and 2 Emergency Diesel Generators [DO] due to a momentary loss of the 116kV offsite power source and valid actuation signals of Division 1 and 2 Essential Service Water System [81] pumps due to the start of Division 1 and 2 Emergency Diesel Generators. This event Is reportable under 10 CFR 50.72(b)(3)(iv)(A) - Event Notification #49120 and 10 CFR 50.73(a)(2)(iv)(A).
On the loss of the 115kV offsite power source, the 4.16kV Division 1 and 2 critical swltchgear de-energized. The temporary loss of power to these critical switchgear buses resulted in the following:
- Start of Division 1 and 2 Emergency Diesel Generators re-energizing the 4.16kV Division 1 and 2 critical switchgear buses. The subsequent start of Division 1 and 2 Essential Service Water System pumps.
- Closure of containment isolation valves in the Reactor Water Cleanup System [CE], Equipment Drain System and the Floor Drain System (WK]. This was an Invalid isolation and is reportable under 10 CFR 50.73(a)(2)(iv)(A)
- . Fuel Pool Coding [DA) pumps tripped.
- Residual Heat Removal [BO] Pump "C" operating in Suppression Pool mixing mode tripped and the system depressurized.
- Control Rod Drive [AA] pump tripped - .
- Reactor building [NO] ventilation tripped
- Plant Service Water [KG] pump tripped Shutdown cooling was not in operation at the time of the loss. Reactor coolant temperature was maintained in the temperature range of 130.170 degrees Fahrenheit. Reactor pressure remained at 0 psig.
IMMEDIATE CORRECTIVE ACTION
Division 1 and 2 Emergency Diesel Generators automatically repowered the 4.16kV Division 1 and 2 critical switchgear buses in less than 15 seconds.
Fuel Pool Cooling pump "B" started automatically upon repowering the Division 2 critical swltchgear bus.
Division 1 and 2 Essential Service Water pumps started automatically due to the start of Division 1 and 2 Emergency Diesel Generators Actions were taken to restore the fdiowing systems to operating status:
- Control rod drive at 1227
- Plant service water at 1238
- Reactor building ventilation at 1243
- Reactor water cleanup at 1258
- 4.16kV Division 2 critical switchgear bus (transferred to the 230kV startup transformer) at 1259 26158 R5
- 4.16kV Division 1 critical switchgear bus (transferred to the 230kV startup transformer) at 1310
- Shutdown cooling at 1343 (due to potential delays in the reactor pressure vessel hydro surveillance)
- Division 1 and 2 Emergency Diesel Generators (returned to standby condition) at 1506
- Residual heat removal system °C" (filled and vented and returned to operable status) at 1554
CAUSE
Bonneville Power Authority (BPA) reported that a line fault was detected in the 115kV line. Protective relays properly reacted to the fault by tripping and reclosing in approximately 1.17 seconds, clearing the line fault. A range fire under the 115kV line is believed to be the cause of the fault.
FURTHER CORRECTIVE ACTION
None
ASSESSMENT OF SAFETY CONSEQUENCES
All off-site electric transmission systems functioned as designed. An analysis of the response of plant equipment and protective systems concludes all safety related plant equipment and systems operated correctly for this condition. There were no safety system functional failures. There were no adverse effects on the health and safety of the public as a result of this event.
SIMILAR EVENTS
There has not been any occurrence of an event or condition in the past three years at Columbia Generating Station involving the actuation of a ESF due to a grid disturbance.
ENERGY INDUSTRY IDENTIFICATION SYSTEM (ENS) INFORMATION CODES EIS codes are bracketed (J where applicable in the narrative.
26158 R5