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| Entered date | Event description | |
|---|---|---|
| ENS 53327 | 12 April 2018 12:14:00 | At 0920 EDT on April 12, 2018, the Watts Bar Unit 2 reactor automatically tripped while operating at 100 percent power. All control and shutdown bank rods inserted properly in response to the automatic reactor trip. All safety systems including Auxiliary Feedwater actuated as designed. The plant is stable with decay heat removal through Auxiliary Feedwater and Steam Dump Systems. The cause of the automatic reactor trip is being investigated. The automatic actuation of the Reactor Protection System (RPS) is being reported as a four-hour report under 10 CFR 50.72 (b)(2)(iv)(B). 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). The NRC Senior Resident Inspector has been notified for this event. The plant is currently stable at normal operating temperature and pressure. The grid is stable and the plant is in its normal shutdown electrical lineup. Unit 1 was unaffected by the Unit 2 trip. |
| ENS 51940 | 17 May 2016 23:06:00 | On May 17, 2016, at 1630 hours while restoring from a plant modification related to new 'loss of phase' circuitry, the 1 B-B 6.9kV buss de-energized resulting in a loss of voltage on the buss. The loss of voltage was caused by the loss of voltage relays that separated offsite power from the 1 B-B 6.9kV buss. At the time, the 1 B-B emergency diesel generator was removed from service for planned maintenance. In response to the loss of power on the 1 B-B 6.9kV buss, the operators entered abnormal operating instruction, AOI 43.02, Loss of Unit 1 Train B Shutdown Boards, and started emergency diesel generators 1 A-A, 2 A-A, and 2 B-B. All equipment operated properly. The emergency diesel generators were not required to be paralleled to the boards. Offsite power was restored to the 1 B-B 6.9kV buss at 1802 hours on May 17, 2016. This condition did not result in any adverse impact on the health and safety of the public. This event is reportable under 10 CFR 50.72(b)(3)(iv)(A), 'Any event or condition that results in valid actuation of any of the systems listed in paragraph (b)(3)(iv)(B) of this section, except when the actuation results from and is part of a pre-planned sequence during testing or reactor operation.' The NRC Resident Inspector has been notified. |
| ENS 46812 | 3 May 2011 14:18:00 | A contract supervisor had a confirmed positive for an illegal drug during a random fitness-for-duty test. The employee's access to the plant has been terminated. The licensee has notified the NRC Resident Inspector. Contact the Headquarters Operations Officer for additional details. |