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| Entered date | Event description | |
|---|---|---|
| ENS 53643 | 4 October 2018 07:57:00 | EN Revision Text: MANUAL REACTOR TRIP DURING LOW POWER PHYSICS TESTING At 0544 EDT on October 4, 2018, with Unit 1 in Mode 2 with reactor power in the intermediate range performing low power physics testing, the reactor was manually tripped due to a rod control urgent failure alarm. The trip was not complex, with all systems responding normally. Operations stabilized the plant in Mode 3. Decay heat is being removed through the main steam system. Unit 2 was not affected. There was no impact to the health and safety of the public or plant personnel. The NRC Resident Inspectors have been notified. All control rods inserted as expected. The cause of the rod control urgent failure is being investigated.
This Event Notification is being updated to clarify that the reactor was not critical when this event occurred. Therefore, the reporting requirement is changed from 10 CFR 50.72(b)(2)(iv)(B) to 10 CFR 50.72 (b)(3)(iv)(A). During Dynamic Rod Worth Measurement testing, Control Bank Charlie was inserted approximately 153 steps when the urgent failure occurred (CBC positioned at 75 steps out). Following the scram, additional analysis concluded that the reactor was subcritical when the Reactor Protection System was actuated." The licensee notified the NRC Resident Inspector. Notified the R2DO (McCoy). |
| ENS 53484 | 3 July 2018 12:00:00 | At 0954 (EDT) on July 3, 2018, with Unit 1 in Mode 1 at 100 percent power, the reactor was manually tripped due to high steam generator water level. The trip was not complex, with all systems responding normally. Operations stabilized the plant in Mode 3. Decay heat is being removed through the main steam lines through the steam dumps and into the condenser. The expected actuation of the Auxiliary Feedwater System (an engineered safety feature) is being reported as an eight hour report under 10 CFR 50.72 (b)(3)(iv)(A). Unit 2 was not affected. There was no impact to the health and safety of the public or plant personnel. The NRC Resident Inspectors have been notified. All control rods inserted and Unit 1 is in an electrical shutdown lineup. The cause of the high steam generator water level transient is being investigated. |
| ENS 52992 | 26 September 2017 11:03:00 | At approximately 0543 (EDT), while (recovering from the performance of) 2B Emergency Diesel Generator and ESFAS testing, a (subsequent) valid undervoltage actuation signal was sent to the 2B Emergency Diesel Generator (EDG). The 2B AC emergency bus (2BA03) was load shed, the 2B EDG automatically started, and tied to 2BA03. The 2BA03 bus was loaded by the automatic load sequencer. The actuation was identified by the Control Room operators and the 2B EDG was locally monitored while in service. This actuation is reportable due to the automatic actuation of a system listed in 10 CFR 50.72(b)(3)(iv)(B). The reactor was not critical at the time of the event and not challenged throughout the event. Decay heat removal and spent fuel pool cooling were not challenged throughout the event. The NRC Resident Inspector has been notified. The cause of the undervoltage condition is under investigation. |
| ENS 52619 | 17 March 2017 17:12:00 | At approximately 1517 (EDT), while restoring protective relay power to the 1B Reserve Auxiliary Transformer, a valid undervoltage actuation signal was sent to the 1B Emergency Diesel Generator (EDG). The 1B EDG automatically started and tied to the safety bus (1BA03). The 1BA03 bus was loaded by the automatic load sequencer. This actuation was identified by the Control Room Operators and the 1B EDG was locally monitored while in service. This actuation is reportable due to the automatic actuation of a system listed in 10 CFR 50.72(b)(3)(iv)(B). The reactor was not critical at the time of the event and not challenged throughout the event. Containment Cooler Number 8 did not automatically start in 'Fast Speed' as expected. Containment Cooler Number 8 was successfully started in 'Fast Speed' manually by the Control Room Operators. The NRC Resident Inspector has been notified. |
| ENS 50894 | 14 March 2015 19:19:00 | On March 14, 2015 at 1207 EDT, operators were performing steps to disable an automatic actuation signal to the B-train Auxiliary Feedwater system (AFW), when a valid actuation signal was received on B-train only. Both motor driven Auxiliary Feedwater pumps were already running and feeding forward. The B-train discharge valves went from throttled to fully open. The AFW discharge valves were restored to their previous positions without any adverse impacts on the plant. Decay heat removal was still being removed through the Atmospheric Relief Valves. The licensee notified the NRC Resident Inspector. |
| ENS 49461 | 22 October 2013 13:18:00 | At 1144 EDT, Vogtle Unit Two was manually tripped in response to lowering Main Condenser vacuum. The Unit 2 Bravo Main Feed Pump was tagged out for scheduled maintenance and the casing was being removed when condenser vacuum started lower due to isolation valve not holding pressure. Main Condenser vacuum lowered to less than procedural limits for continued plant operation. All systems operated correctly in response to the reactor trip. All control rods fully inserted. AFW was placed in service to control Steam Generator levels. System response allowed for an uncomplicated reactor trip response. Plant is stable in Mode 3 while performing a cause investigation. The NRC Senior Resident Inspector was notified and at plant site. The plant is in a normal post-trip electrical line-up. Decay heat is being removed via the steam dumps to the Main Condenser. |