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| Entered date | Event description | |
|---|---|---|
| ENS 51086 | 22 May 2015 10:43:00 | At 0014 PDT on 05/22/2015, Columbia experienced an unexpected momentary loss of SM-7, a Division 1 4.16 kV vital bus, resulting in a start of Emergency Diesel DG-1 . Additionally, under voltage circuitry prevented Standby Service Water pump 1A from starting to support DG-1 in response to the valid under voltage condition, and operators tripped the diesel at 0016 PDT. The SM-7 bus was reenergized by a 115 kV offsite source through backup transformer TR-B. The cause of this event was an inadvertent trip of under voltage circuitry while connecting test equipment in preparation for Diesel and Loss of Power logic testing. Division 1 was inoperable due to ongoing maintenance during the current refueling outage and was not being relied upon for decay heat removal or core circulation. Columbia is in Mode 5 with a coolant temperature of 96 degrees F, water level is at the normal refueling flooded level with fuel pool cooling gates removed. Division 2 is providing required electrical power and supporting components required for decay heat removal and inventory control. There was no impact to Shutdown Safety Assessment. The NRC Resident Inspector has been notified. |
| ENS 49460 | 22 October 2013 12:43:00 | At 0754 on 8/23/13, a loss of power to the Reactor Protection System (RPS) 'B' occurred due to the unexpected opening of the circuit breaker (RPS-CB-MG2) for the RPS 'B' motor generator due to a failure of the voltage regulator circuit card. The loss of RPS 'B' resulted in a half scram signal, closure of Primary Containment Isolation Valves (PCIVs) from multiple systems and loss of power to main steam line radiation monitors (MS-RIS-610B & MS-RIS-610D). No plant parameters or maintenance activities existed which would cause the opening of RPS-CB-MG2 or actuation of the primary containment isolation; therefore, this is considered to be an invalid actuation of a system listed in 10CFR50.73(a)(2)(iv). The half scram signal, closure of Primary Containment Isolation Valves (PCIVs) from multiple systems, and loss of power to main steam line radiation monitors were an expected response to the loss of RPS 'B'. RPS 'B' was repowered from an alternate power supply. The half scram signal was reset, the containment isolation valves were opened and the affected systems were returned to normal operation. The voltage regulator circuit card was replaced and RPS 'B' was returned to its normal power supply. As indicated in 10CFR50.73(a)(1), in the case of an invalid actuation reported under 10CFR50.73(a)(2)(iv)(A), the licensee may, at its option, provide a telephonic notification to the NRC Operations Center within 60 days of discovery of the event instead of submitting a written LER. This 60-day telephone notification is being made to meet the reporting requirements instead of submitting an LER since the actuation was invalid. The following additional information is provided as specified in NUREG-1022: The specific train(s) and system(s) that were actuated: PCIVs in multiple systems EDR-V-19 Drywell Equipment Drain Inboard Isolation Valve
EDR-V-20 Drywell Equipment Drain Outboard Isolation Valve
FDR-V-3 Drywell Floor Drain Inboard Isolation Valve
FDR-V-4 Drywell Floor Drain Outboard Isolation Valve
RWCU-V-1 Reactor Water Cleanup Suction Inboard Isolation Valve
RWCU-V-4 Reactor Water Cleanup Suction Outboard Isolation Valve
RRC-V-19 Reactor Water Sample Inboard Isolation Valve
RRC-V-20 Reactor Water Sample Outboard Isolation Valve
TIP-V-15 Traversing In-Core Probe Purge Isolation Valve
CRD-V-11 Control Rod Drive Scram Discharge Volume Drain Valve
Whether each train actuation was complete or partial: All PCIVs actuations for a loss of RPS 'B' were complete.
The reactor half scram for a loss of RPS 'B' was a partial activation.
Whether or not the system started and functioned successfully: All PCIVs functioned successfully. The licensee notified the NRC Resident Inspector. |
| ENS 48139 | 26 July 2012 17:52:00 | At 0535 (PDT) on 5/31/12 during power ascension following a maintenance outage, a loss of power to the Reactor Protection System (RPS) 'B' occurred due to the unexpected opening of the circuit breaker (RPS-CB-MG2) for the RPS 'B' motor generator. The loss of RPS 'B' resulted in a half scram signal, closure of Primary Containment Isolation Valves (PCIVs) from multiple systems and loss of power to main steam line radiation monitors (MS-RIS-610B & MS-RIS-610D). No plant parameters or maintenance activities existed which would cause the opening of RPS-CB-MG2; therefore, this is considered to be an invalid actuation of a system listed in 10CFR50.73(a)(2)(iv). The half scram signal, closure of Primary Containment Isolation Valves (PCIVs) from multiple systems, and loss of power to MS-RIS-B & D were an expected response to the loss of RPS 'B'. Power ascension was temporarily halted. RPS 'B' was repowered from an alternate power supply. The half scram signal was reset, the containment isolation valves were opened and the affected systems were returned to normal operation. Power ascension was resumed. The circuit breaker (RPS-CB-MG2) was replaced and RPS 'B' was returned to its normal power supply. Initial investigation efforts have not determined a cause for RPS-CB-MG2 opening. Investigations into the cause of RPS-CB-MG2 opening are continuing. As indicated in 10CFR50.73(a)(1), in the case of an invalid actuation reported under 10CFR50.73(a)(2)(iv)(A), the licensee may, at its option, provide a telephonic notification to the NRC Operations Center within 60 days of discovery of the event instead of submitting a written LER. This 60-day telephone notification is being made to meet the reporting requirements instead of submitting an LER since the actuation was invalid. The following additional information is provided as specified in NUREG-1022: The specific train(s) and system(s) that were actuated: PCIVs in multiple systems EDR-V-19 Drywell Equipment Drain Inboard Isolation Valve EDR-V-20 Drywell Equipment Drain Outboard Isolation Valve FDR-V-3 Drywell Floor Drain Inboard Isolation Valve FDR-V-4 Drywell Floor Drain Outboard Isolation Valve RWCU-V-1 Reactor Water Cleanup Suction Inboard Isolation Valve RWCU-V-4 Reactor Water Cleanup Suction Outboard Isolation Valve RRC-V-19 Reactor Water Sample Inboard Isolation Valve RRC-V-20 Reactor Water Sample Outboard Isolation Valve TIP-V-15 Traversing In-Core Probe Purge Isolation Valve CRD-V-11 Control Rod Drive Scram Discharge Volume Drain Valve Whether each train actuation was complete or partial: All PCIVs actuations for a loss of RPS 'B' were complete The reactor half scram for a loss of RPS 'B' was a partial activation Whether or not the system started and functioned successfully: All PCIVs functioned successfully The licensee notified the NRC Resident Inspector. |
| ENS 48005 | 7 June 2012 19:16:00 | On September 17, 2011, a root cause analysis identified that errors in the dose projection software gain factor associated with the high range stack monitor were introduced in 2000 and had the potential to produce inaccurate dose projection results. The resulting condition could have impacted the ability to accurately assess ongoing releases and determine appropriate protective measures for the public. The gain factors were corrected in October 2011 and dose projection capabilities have been restored. This condition was not originally recognized as being reportable in accordance with 10 CFR 50.72(b)(3)(xiii) due to the limited nature of the impact to a small portion of the radiological effluent EALs, however, it has been recently determined to be reportable. This late identification of reportability has been entered into our corrective action program. The licensee will notify the NRC Resident Inspector. |
| ENS 40273 | 23 October 2003 21:39:00 | Discovered vulnerability in a safeguard system that could allow unauthorized or undetected access to safeguards material. Compensatory measures have been employed. The licensee notified the NRC Resident Inspector. Contact Headquarters Operations Officer for additional details. |