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| Entered date | Event description | |
|---|---|---|
| ENS 52163 | 9 August 2016 16:58:00 | On 8/09/2016 at 1415 EDT, TVA (Tennessee Valley Authority) notified the National Response Center that Watts Bar Nuclear (WBN) Plant has noted an oil sheen in the Unit 2 Cooling Tower Basin. An oil sheen was observed within the Unit 2 Cooling Tower Basin at WBN. The sheen did not cover the entire cooling tower basin. The sheen covered approximately 4 square feet. No oil sheen was visible in the yard holding ponds or Tennessee river from the bank above the diffuser pipes. Notifications were also made to TEMA (Tennessee Emergency Management Agency). Oil levels from the suspected source did not indicate any change in oil reservoir levels. Unit 1 remains in Mode 1 at 85 (percent) power - reduced power due to main condenser back pressure limits. Unit 2 remains in Mode 1 at 25 (percent) power - initial startup testing. This event is reportable under 10 CFR 50.72(b)(2)(xi) as a condition that was reported to an outside Government Agency. The NRC Resident Inspector has been notified. |
| ENS 51815 | 22 March 2016 13:59:00 | On March 22, 2016, at 1131 EDT, the Watts Bar Nuclear Plant Unit 1 (WBN1) reactor tripped due to the actuation of the Over Temperature Delta Temperature bistables. Concurrent with the reactor trip, the Auxiliary Feedwater (AFW) system actuated. All control rods inserted upon the reactor trip. Engineered Safety Function systems functioned as expected. WBN1 is currently stable in Mode 3. The Reactor Coolant system is being maintained at normal operating pressure and no-load temperature with decay heat removal via the Main Condenser steam dumps and the AFW system. The station is in a normal shutdown electrical alignment. Watts Bar Unit 2 is in mode 4 preparing for power ascension testing and was unaffected by the WBN1 event. The cause of the event is under investigation. This event is being reported pursuant to 10 CFR 50.72(b)(2)(iv)(B) and 10 CFR 50.72(b)(3)(iv)(A). The NRC Resident Inspector has been notified. |
| ENS 50580 | 30 October 2014 14:07:00 | On October 30, 2014, at 1100 EDT, TVA conducted a briefing for government officials and other stakeholders regarding the decision to accelerate the Boone Reservoir annual drawdown after discovery of a sink hole near the base of the embankment and a small amount of water and sediment found seeping from the river below the dam. TVA is continuously monitoring the dam and conducting an investigation to determine the source of the water seepage. The dam is located upstream of all three TVA nuclear sites. There are currently no nuclear plant operability or safety issues, and TVA is assessing the impacts on the plant licensing bases. A press release was issued at approximately 1300 EDT. This notification is being made in accordance with 10 CFR 50.72(b)(2)(xi) due to notification of other government agencies and a news release. The NRC Senior Resident Inspector was notified. The licensee is evaluating this event for potential impact on the design basis flooding level. |
| ENS 50278 | 13 July 2014 23:13:00 | On July 13, 2014 at 1937 (EDT), Watts Bar Nuclear Plant Unit 1 reactor was manually tripped due to automatic isolation of all low pressure feedwater heaters. Concurrent with the reactor trip the Auxiliary Feedwater system actuated as designed. All Control and Shutdown rods fully inserted. All safety systems responded as designed. The unit is currently stable in Mode 3, with decay heat removal via Auxiliary Feedwater, steam dumps and the main condenser. The station is in a normal shutdown electrical alignment. The cause is currently under investigation. This is being reported under 10CFR 50.72(b)(3)(iv)(A) and 10CFR 50.72 (b)(2)(iv)(B). The NRC Senior Resident (Inspector) has been notified. Initial indications are that a level switch failed on the #7 heater drain tank which caused the heater drain tank pumps to trip. When the high level tank setpoint was reached, the feedwater system isolated. |
| ENS 50242 | 30 June 2014 17:00:00 | A non-licensed contract supervisor tested positive for alcohol on a random fitness for duty test. The supervisor's access to the facility has been terminated. The licensee has notified the NRC Resident Inspectors. |