Semantic search
| Entered date | Event description | |
|---|---|---|
| ENS 47959 | 24 May 2012 17:31:00 | On 5/24/2012 at 1541 EDT, a notification to the National Response Center was made after the discovery of a visible oil sheen on waters of the U.S. (the Tennessee River side of Sequoyah's intake forebay skimmer wall). The source of the oil appears to be a tipped or overflowing catchpan located in the Essential Raw Cooling Water (ERCW) pumping station. All catchpans in the pumping station have been emptied to eliminate them as immediate potential source of oil released to the environment. The following agencies have also been notified: EPA Region 4, and the Tennessee Emergency Management Agency (TEMA). The Tennessee Department of Environment and Conservation (TDEC) will be notified. Cleanup is in progress. Measures to prevent recurrence are being taken. The NRC Resident Inspector will be notified. |
| ENS 46991 | 26 June 2011 19:39:00 | At 1614 EDT on 6/26/2011, Unit 1 reactor automatically tripped following a turbine trip from greater than 50% rated thermal power (P-9 interlock). Following the reactor trip, all safety-related equipment operated as designed. Auxiliary Feedwater automatically actuated as expected on loss of the operating main feedwater pumps. Initially, the steam dump system functioned as expected (all valves opened). Subsequently, the steam dump system was manually turned off when 3 of the valves did not close when expected. Consequently, decay heat removal is via the Steam Generators' atmospheric relief valves. No primary or secondary safety valves opened during or after this trip. 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. There is no indications of any primary to secondary leakage. All control and shutdown rods are inserted. The electrical alignment is normal, supplied from off-site power. There was no impact to Unit 2. Unit 2 is operating at 100% power / Mode 1 The NRC Resident Inspector has been notified. |
| ENS 46797 | 27 April 2011 20:19:00 | At 1929 EDT, both off-site A.C. power sources to Sequoyah were declared inoperable due to the effects of inclement weather on the TVA transmission system. This determination was made after a review of grid conditions confirmed that pre-analyzed grid/offsite power requirements could not be met. Both Sequoyah Units have entered TS LCO 3.8.1.1, action d, for two inoperable offsite power sources. It has not been determined when this condition will no longer exist. Although inoperable, off-site A.C. sources remain connected to Sequoyah; emergency diesel generators are not running nor required to be at this time. T.S. LCO 3.8.1.1, action d, requires verifying EDG operability within 8 hours and restoration of both offsite power sources within 24 hours or placing both Units in mode 3. The licensee informed the NRC Resident Inspector. * * * UPDATE FROM JEFF EPPERSON TO PETE SNYDER AT 0203 EDT ON 4/28/11 * * * As of 0119 EDT the licensee has two operable offsite power sources qualified through transmission and reliability analysis. The licensee exited their LCO Condition. The grid condition is now yellow. Notified R2IRC (Gody). |
| ENS 45520 | 26 November 2009 04:00:00 | At 0242 EST, 11/26/2009 Unit 2 reactor was manually tripped based upon indications that the 2A Main Feedwater Pump Turbine was losing vacuum. Prior to the trip, the reactor was at 30% RTP and ascending following completion of a scheduled refueling outage. 2A Main Feedwater Pump was in service; preparations were in progress to start 2B Main Feedwater Pump to support continued power ascension. Subsequent to the trip, the Auxiliary Feedwater Pumps (motor-driven and turbine-driven) started as expected in response to the trip of both main feedwater pumps following receipt of a normal feedwater isolation signal. No primary or secondary plant safety valves operated during the transient. All plant system responses to the trip were as expected. An investigation will be conducted to identify the cause of the indicated loss of vacuum and the required corrective actions. Expected restart date to be determined. All control rods fully inserted. The licensee has notified the NRC Resident Inspector. |
| ENS 40113 | 28 August 2003 22:01:00 | At 1618 EDT on 08/28/03, an Alert was declared at Sequoyah Unit 1 due to a failure of the Reactor Protection System (RPS) to auto-trip the reactor following a turbine trip. Turbine oil trip testing was in progress when at 1604, the main turbine tripped. The reactor trip breakers were opened by manual operator action approximately 20 seconds after the valid reactor trip signal. Following the trip, all systems operated as required. The main steam isolation valves were manually closed based on indication of steam flow and a throttled steam dump valve. No primary system or steam generator safety valves opened. The unit is currently stable with temperature controlled using atmospheric relief valves. The Auxiliary Feedwater System received an auto-start signal and successfully operated. All control rods were fully inserted into the core. There was no release of radioactive material. The licensee has initiated an investigation into the cause of the incident. The NRC Resident Inspector and the State of Tennessee were notified by the licensee. The NRC notified FEMA (Steiner), DOE (Morroni), USDA (Beers-Block), HHS (Williams), DHS (Glick), and DOT/EPA/NRC (Threatt). The NRC entered monitoring phase of normal mode with Region 2 in the lead at 1735 EDT.
At 2030 EDT on 08/28/03, the licensee terminated the Alert at Sequoyah Unit 1. The reactor is stable and in Mode 3, Hot Standby. This termination is based upon containment integrity, Emergency Core Cooling System and Engineered Safety Features operability, availability of heat sink, onsite and offsite electrical system and Emergency Diesel Generator operability, radiation monitor operability, availability of technical support personnel, and activation of a forced outage recovery team. Reactor coolant samples were taken, which showed no increase in activity. The NRC notified FEMA (Austin), DOE (Morroni), USDA (Beers-Block), HHS (Hogan), DHS (Van Buskirk), and DOT/EPA/NRC (White). The NRC exited monitoring phase of normal mode at 2045 EDT. |