Semantic search
| Entered date | Event description | |
|---|---|---|
| ENS 52918 | 20 August 2017 22:46:00 | On August 20, 2017 at 1605 PDT, Columbia Generating Station was manually scrammed from 100 percent power due to a rise of Main Condenser back pressure. Manual scram of the unit is procedurally required upon a loss of Main Condenser back pressure. Preliminary investigations indicate that the Main Condenser air removal suction valve (AR-V-1) closed, resulting in the Condenser back pressure rising to within 1.0 inch Hg of the setpoint with reactor power greater than 25 percent. Further investigations continue. All control rods fully inserted. In addition to the closure of the air removal suction valve, one of two Reactor Feedwater startup flow control valves did not adequately operate to control Reactor vessel level and resulted in a high-level (Level-8) actuation tripping the Reactor Feedwater System. All other systems operated as expected. Reactor water level is currently being controlled manually with the start-up level control isolation valve. AR-V-1 has been manually opened with a jumper and temporary air supply. Reactor decay heat is being removed via bypass valves to the Main Condenser. This event is being reported under the following: 10 CFR 50.72(b)(2)(iv)(B), which requires a four-hour notification for any event or condition that results in actuation of the Reactor Protection System when the reactor is critical. The licensee notified the NRC Resident Inspector. The licensee plans to issue a press release.
The licensee is updating the notification to include an 8 hour notification under 10 CFR 50.72(b)(3)(iv)(A) for a specified system actuation due to a Level 3 isolation signal which occurred approximately 20 minutes after the scram. The licensee is currently in cold shutdown to repair the Reactor Feedwater startup flow control valve. The licensee has notified the NRC Resident Inspector. Notified R4DO (Farnholtz). |
| ENS 49152 | 28 June 2013 04:07:00 | At 1758 (PDT) on June 27, 2013, an alarm signaling heating, ventilation and air conditioning (HVAC) trouble in the Division 3 diesel and high pressure core spray (HPCS) room was received in the main control room. Follow-up investigation determined that the switch for the normal room supply fan (DMA-FN-32) was off. It is believed that the switch may have been inadvertently mispositioned during ongoing work in the vicinity. A worker was moving a vacuum nearby and stopped when he heard the local alarm. Columbia Generating Station is performing further investigation to determine if there are other possibilities for DMA-FN-32 control switch being mispositioned. The fan was returned to service at 1819 (PDT). An Operation's supervisor was present when returning the switch to ON and verified the switch operated as expected. Loss of DMA-FN-32 results in both the HPCS diesel (DG-3) and the HPCS system being inoperable due to inadequate cooling of those systems. Offsite power for Division 3 was verified to be operable while DG-3 was inoperable. The loss of the HPCS system results in the loss of safety function for a single train system and thus is reportable under the 10 CFR 50.72 sections noted above. Appropriate Technical Specification actions were entered and exited for DG-3 and HPCS inoperability times. There was no radiological release associated with this event. No safety system actuations or isolations occurred. The licensee notified the NRC Resident Inspector. |
| ENS 48639 | 30 December 2012 15:45:00 | Technical Specification 3.6.4.1 (Secondary Containment) requires that the secondary containment be operable. Surveillance requirement 3.6.4.1.3 requires verifying each secondary containment access inner door or each secondary containment access outer door in each access opening is closed. During a fire tour, a security officer proceeded through Reactor Building outer security door (R-204) and opened the inner door (R-205) prior to the outer security door completely closing. This resulted in both the Reactor Building inner and outer access doors being simultaneously open for a short duration. Normally, the doors are interlocked in which the inner door would not be able to be opened prior to the outer security door being closed. The security officer immediately notified the Main Control Room and operations personnel verified both doors were locked and closed. The outer security door (R205) has been key-locked closed until corrective actions are determined. Columbia Generating Station is investigating why the interlock feature failed. There were no radiological releases associated with the event. No safety system actuations or isolations occurred. The Licensee has notified the NRC Resident Inspector. |
| ENS 48170 | 8 August 2012 23:32:00 | At 1350 PDT on 08-08-2012, during the performance of an annual surveillance, power supply ARM-E/S-603A was discovered to have out of tolerance voltage readings. ARM-E/S-603A was declared non-functional. This resulted in a loss of the ability to monitor and quantify radiological conditions in multiple areas of the reactor building, due to the loss of ARM-RIS-1 through 10 (Area Radiation Monitor Radiation Indicating Switches 1 through 10). The loss of ability to monitor and quantify radiological conditions in multiple areas of the reactor building represents a major loss of emergency assessment capability per 10 CFR 50.72(b)(3)(xiii). As directed by station procedures, compensatory measures have been enacted to have Health Physics personnel tour the affected areas once per shift to document and trend the radiological conditions. ARM-RIS-1 and 4 thru 10 are used for EAL determinations. ARM-E/S-603A was returned to service at 1524 PDT on 08/08/2012. The licensee has notified the NRC Resident Inspector. |