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| Entered date | Event description | |
|---|---|---|
| ENS 52469 | 30 December 2016 16:37:00 | On 12/30/16 at 1302 EST, Unit 1 began withdrawing control bank rods for an approach to criticality following a refueling outage. At 1305 EST, operators observed that control rod H-6 did not withdraw. Operators entered the applicable Abnormal Operating Procedure. Operators tripped the reactor as required by plant procedures and entered applicable Emergency Operating Procedures. The act of manually tripping the reactor generated a valid trip signal in the plant Reactor Protection System. Following the reactor trip, all safety related equipment operated as designed. Auxiliary feedwater was already supplying the Steam Generators; a Feedwater Isolation occurred due to plant conditions. Unit 1 is currently being maintained in Mode 3 at NOT/NOP, approximately 548 degrees F and 2235 psig, with auxiliary feedwater supplying the steam generators, and decay heat removal via the steam dumps. Method of decay heat removal is Steam Generators via the steam dumps. Current reactor coolant system conditions: Temperature at 548 degrees F and stable, pressure 2235 psig and stable. All control and shutdown banks are inserted. Electrical alignment is normal, supplied by offsite power. No impact to Unit 2, Unit 2 is in Mode 1 at 100 percent power. The licensee notified the NRC Resident Inspector. |
| ENS 52426 | 13 December 2016 14:40:00 | On 12/13/16 at 1410 (EST), the following voluntary communication was made to the State of Tennessee in accordance with Tennessee Valley Authority's (TVA) guidance for communicating inadvertent radiological spills/leaks that are below regulatory reporting requirements to outside agencies and in alignment with NEI 07-07, 'Industry Ground Water Protection Initiative'. On 12/12/16, Sequoyah Nuclear Plant determined that a spill of greater than 100 gallons (approximately 3000 gallons) of condensate storage tank water with tritium levels of 1560 pCi/L (picocuries per liter) was spilled to a yard drain. The spill occurred on 12/5/16, during the filling of the Unit 1 #4 steam generator when a hose connection on a temporary fill skid failed. No elevated tritium levels have been detected at the Sequoyah Yard Drainage Pond before or after the event. This is reported in accordance with 10CFR50.72(b)(2)(xi), the required reportable threshold for tritium is 20,000 pCi/L. The licensee will notify the NRC Resident Inspector. |