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| Start date | Reporting criterion | Title | Event description | System | LER | |
|---|---|---|---|---|---|---|
| ENS 52526 | 1 February 2017 21:05:00 | 10 CFR 50.72(a)(1)(i), Emergency Class Declaration | Unusual Event - Potential Security Event | Plant Hatch declared a notification of unusual event. Subsequent investigation determined the paraphernalia was related to plant drills. The Unusual Event was terminated at 1727 EST. The licensee notified the NRC Resident Inspector. Notified the DHS SWO, FEMA, NICC, and NNSA (via e-mail).
The event was retracted. The licensee notified the NRC Resident Inspector. Notified the R2DO (Shakur), NSIR (Holian), IRD MOC (Gott), DHS SWO, FEMA, NICC, and NNSA (via e-mail). | ||
| ENS 46258 | 18 September 2010 20:27:00 | 10 CFR 50.72(a)(1)(i), Emergency Class Declaration | Unusual Event Declared Due to High-High Reactor Building Sump Level Alarm | This is a one-hour report for the discovery of a condition that met an Emergency Activation Level (EAL) for a Notification of an Unusual Event (NOUE). EAL HU-1 - Natural and Destructive Phenomena Affecting the Protected Area Threshold Value 6 states, 'Exceed Max Normal Operating Values specified in EOP 31 EO-EOP-014-1 SC - Secondary Containment Control Table 5 Secondary Containment Operating Water Levels.' Plant Hatch Unit 1 declared a NOUE on 9/18/10 at 1627 based on HU-1 Natural and Destructive Phenomena Affecting the Protected Area due to exceeding the Max Normal Operating Value for the Reactor Building NE Diagonal Floor Drain Sump. At 1615, both the Level High and Level High-High annunciators alarmed. Water has not overflowed the sump. However, due to its design, it is not possible to immediately visually confirm the sump level. The sump pumps were not running and would not run with their switches in START indicating either: (1) there is no water in the sump, (2) both pumps are OOC (Out of Commission), or (3) there is a problem in the sump level control system. Maintenance is assessing the situation. The licensee has notified the state and local agencies and will notify the NRC Resident Inspector.
At 0400 EDT, the NOUE was terminated. The termination criteria was that the NE Diagonal Floor Drain Sump level was in its normal operating range with no abnormal sump in-leakage detected. Compensatory measures are in place to measure level in the sump. An investigation into the abnormal level indication is still in progress. The licensee will be notifying state and local authorities as well as the NRC Resident Inspector. Notified R2DO (Henson), IRD (Gott), NRR EO (Howe), DHS (Inser) and FEMA (Via).
On September 18, 2010, a notification, Event Number 46258, was submitted to the NRC to report a circumstance at Plant Hatch Unit 1 which appeared to be a 'High-High' reactor building sump level alarm. Such an alarm would meet the designated Emergency Activation Level (EAL) for a Notification of an Unusual Event (NOUE). On the day of the event, it was thought that receipt of both the 'High' and 'High-High' level annunciators for the reactor building northeast diagonal floor drain sump was indicative of the sump level having reached its maximum normal operating level, and a NOUE was made. During a subsequent Investigation, engineering personnel determined that the 'High' and 'High-High' level switches for this sump are wired such that both alarms are actuated concurrently when the 'High' level in the sump is reached at approximately 52 Inches. The 'High-High' sump level annunciation (the level at which the NOUE must be made) Is supposed to alarm at approximately 60 inches. Engineering personnel also determined that the level logic is currently improperly configured to clear both the 'High' and 'High-High' level alarms when the sump level rises to 60 inches. The initial 'High' and 'High-High' level alarms in the main control room were received at approximately 1615 EDT on September 18, 2010. At that time the sump level would have reached an actual level of approximately 51 inches (albeit with a false indication of approximately 60 inches due to the configuration error noted above) based on the setpoint at which this alarm occurs. The normal leakage into this sump at the time of this event was at a rate of approximately 1 inch per hour. The sump pumps were started at approximately 1800 EDT to pump down the sump. This action resulted in a maximum actual sump level of approximately 53.5 inches, assuming the normal leakage into the sump was occurring during this period. At no time did the sump level actually reach the 'High-High' sump level criteria of 60 inches, nor did the annunciated level clear prior to pumping down the sump which also demonstrated that the 60 inch criteria was not met. It is now apparent that the initial NOUE was a conservative report that was properly made based on the information available to the operators at the time. The subsequent investigation provided additional information regarding actual sump level conditions including information that both 'High' and 'High-High' alarms annunciate at the 'High' sump level and would have cleared had the 'High-High' level been reached. Since the 'High-High' sump maximum normal operating level of 60 inches was never reached during this event, the determination has been made that the EAL was not appropriate given the actual sump conditions, thereby making the event non-reportable and an NOUE unnecessary. Based on the preceding Information, Southern Nuclear Company (SNC) hereby provides notification that Event Number 46256 is retracted. The licensee will notify the NRC Resident Inspector. Notified R2DO(McCoy). | Secondary containment | |
| ENS 46227 | 3 September 2010 02:50:00 | 10 CFR 50.72(a)(1)(i), Emergency Class Declaration | Notification of Unusual Event Declared Due to High Water Level in the Rcic Instrument Sump | This is a one-hour report for the discovery of a condition that met an emergency action level (EAL) for a Notification of Unusual Event (NOUE). EAL HU1 - Natural and Destructive Phenomena Affecting the Protected Area Threshold Value 6 states: 'Exceeding Max Normal Operating Values specified in EOP 31EO-EOP-014-1(2) SC - Secondary Containment Control Table 5 Secondary Containment Operation Water Levels.' On September 2, 2010 Plant Hatch Unit 2, as part of an on-going RCIC (Reactor Core Isolation Cooling) system outage, was restoring a tagout which un-isolated the CST (Condensate Storage Tank) from the RCIC system. The shift crew received several alarms in a short period of time for RCIC Northwest Diagonal Instrument Sump levels culminating with receiving the RCIC N-W DIAG INSTRSUMP LVL HIGH HIGH HIGH alarm at 2240. There was a report of water on the floor of the diagonal and 2E51-FV005 (a vent valve on the discharge of the barometric condensate pump) was identified as the source. The shift crew closed 2E51-F010 (suction isolation valve to the CST) to isolate the CST from the RCIC system. The Shift Manager declared an NOUE at 2250 for HU-1 Natural and Destructive Phenomena Affecting the Protected Area. At 2255 the Triple High alarm cleared. Plant personnel have visually confirmed that the sump level has been pumped down to normal level. The water level in the RCIC room did not rise to a level such that any equipment was adversely affected. Plant Hatch notified the following agencies: Georgia EMA, Appling County EMA, Jeff Davis County EMA, Tattnall County EMA, and Toombs County EMA. At the time of this notification, exit criteria for exiting the NOUE had been met and Hatch personnel were in the process of officially terminating the NOUE. The licensee will notify the NRC Resident Inspector.
The licensee officially terminated the NOUE at 0013 EDT on 9/3/2010. | Secondary containment | |
| ENS 44815 | 29 January 2009 13:50:00 | 10 CFR 50.72(a)(1)(i), Emergency Class Declaration | Unusual Event - Toxic Gas Discharge in Waste Gas Treatment Building | An unisolable pipe break on an in-service waste gas treatment building chiller has resulted in a toxic release of asphyxiant freon gas. All personnel were evacuated and no injuries occurred. An entry by operations personnel with self contained breathing apparatus verified that all site personnel have evacuated the building. There was no impact to offgas processing equipment in the area and actual gas concentration was not known at the time of declaration so the assumption of toxic gas concentration is conservative. The Licensee notified the NRC Resident Inspector, Georgia Emergency Management Agency, Appling County, Jeff Davis County, Tattnall County, and Toombs County.
Air samples in the area indicated no detectable freon. Licensee terminated the event at 0946. Notified R2DO(McCoy), NRR EO(Ross-Lee), DHS(Inzer), and FEMA(LaForte) | ||
| ENS 43541 | 1 August 2007 06:05:00 | 10 CFR 50.72(a)(1)(i), Emergency Class Declaration | Unusual Event Declared Due to Fire in Protected Area Greater than 10 Minutes | An Unusual Event was declared based on a fire lasting > 10 minutes within the Protected Area. Fire was on a Pole Mounted Transformer located on the 230 KV Supplemental Power System in the North East corner of the Protected Area. Helper Cooling Tower Fans were lost and sequenced back on. Unit 1 maintained 100% Rated Thermal Power. Unit 2 reduced power to 91.2% due to increasing Circulating Water Temperatures per procedure. Fire was extinguished at 0213 using dry chemical fire extinguishers. Fire was initially spotted at 0152 EDT. It is believed that a snake may have caused the transformer to arc and that the arcing caused the wood transformer pole to catch on fire. Other than the brief loss of helper cooling to the circ water, there was no other impact on the facility. No offsite assistance from the fire department was called or needed. The licensee terminated the Unusual Event at 0250 EDT. The licensee notified local and State Authorities and the NRC Resident Inspector. | ||
| ENS 42537 | 1 May 2006 08:39:00 | 10 CFR 50.72(a)(1)(i), Emergency Class Declaration | Unusual Event Declared Due to a Fire in an Isophase Bus Duct Lasting 11 Minutes | The Unusual Event was declared due to a fire lasting greater than 10 minutes (after discovery) within the protected area. The fire was located on the Isophase Bus Duct near the Main Transformer. A load reduction to 80% rated thermal power is in progress on Unit 1. The fire was extinguished at 0450 with dry chemicals extinguishers." The licensee believes the fire was on cabling in the Isophase bus duct due to overheating. The licensee has been monitoring hot spots on the duct cabling for several days. The fire did not apparently impact any other systems and observers are at the location monitoring for any change in conditions. No Tech Spec Limiting Conditions of Operations resulted from the fire and there is no impact on Unit 2 operations (which is currently at 100%). Termination criteria will be based on management judgment and safety assessment.
Unusual Event terminated at 0655 (EDT). Fire extinguished. Reactor power reduction continuing. Management evaluating continued operation. The unit is currently at 77% power and plans are to reduce power to 60% pending their evaluation of continued operation. The licensee will notify the NRC Resident Inspector. Notified R2 DO (K. Landis), NRR EO (M.J. Ross-Lee), IRD Manager (P. Wilson), DHS (S. York), and FEMA ( M. Roland). | Main Transformer | |
| ENS 42096 | 29 October 2005 17:25:00 | 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation 10 CFR 50.72(a)(1)(i), Emergency Class Declaration 10 CFR 50.72(b)(3)(iv)(A), System Actuation | Unusual Event - Main Transformer Fire | NUE declared on Hatch Unit 1 due to a fire on the main transformer lasting greater than 10 minutes. Unit 1 reactor scram on main turbine trip. Group 2 PCIV (Primary Containment Isolation Valves) isolation on low reactor water level (+3 inches). All group 2 valves closed as required. Fire extinguished at 1358 hours. Plant is stable. All control rods fully inserted on the reactor scram. The plant is in hot shutdown steaming through the turbine bypass valves to the main condenser. No safety systems are affected. Emergency electrical buses are on normal offsite power and emergency diesel generators are available if required. The onsite fire brigade responded to the fire and the fire suppression system for the main transformer functioned as expected. The licensee notified the NRC Resident Inspector.
The licensee is still in a NUE. The fire is out. The fire reflashed at 1603 when the deluge system was secured to inspect the transformer. The deluge system was restarted immediately. Offsite fire support have responded. Cleanup efforts are in progress. The licensee notified the NRC Resident Inspector. Notified IRD (Blount), R2DO (Cahill), and NRR EO (J. Hannon).
The licensee is still in a NUE. This call is to add an offsite notification per 10 CFR 72.75 (b)(2) to another government agency. The site chemistry department notified the National Response Center (Coast Guard) at 1636 that the site had discharged an unknown quantity of oil into the Altamaha River and was implementing site spill control and countermeasures procedures. The licensee also notified the Georgia Environmental Protection Division. The licensee notified the NRC Resident Inspector. Notified IRD (Blount), NRR EO (J. Hannon), and R2DO(Cahill).
The licensee reports that the fire is confirmed extinguished (i.e., no risk of reflash) based on long term monitoring of the transformer including thermography measurements. The Unit remains in an Unusual Event until assessment activities related to the transformer fire have been completed. The licensee notified the NRC Resident Inspector.
Based on the results of assessment activities related to the transformer fire, the licensee has exited the Unusual Event at 0050. The licensee notified the NRC Resident Inspector. The R2DO (Cahill), EO (Hannon), IRD (Blount), DHS (Doyle), and FEMA (Bisco) have been notified. | Emergency Diesel Generator Primary containment Main Transformer Main Condenser Control Rod | |
| ENS 41381 | 8 February 2005 01:55:00 | 10 CFR 50.72(a)(1)(i), Emergency Class Declaration | Plant Had a Freon Leak in the Drywell Chiller Room | The plant reported that there was a freon leak in the Drywell Chiller Room located in the Unit 2 Reactor Building. Maintenance was being performed on the refrigeration equipment relief valve when the gas began to escape into the room. There were six men working in the room and two were affected by the freon gas. They were treated on site and released. Oxygen content in the room was 20.5% and LEL for hydrocarbons was alarming at 19%. The drywell chiller room is secured and being cleared of the 1,200 pounds of freon gas. At this time an investigation is being made to determine the cause which may have been due to the relief valve opening or the workers removing the valve. The plant entered the NOUE due to a "toxic gas release". The NOUE will be terminated when the room is habitable. The NRC Resident Inspector was notified along with State and Local agencies.
Licensee reported that the NOUE was terminated at 0245 EST after the freon had been successfully cleared from the Drywell Chiller Room. Licensee will notify the NRC Resident Inspector. Notified FEMA (Liggett), DHS (Knox), IRD (Wilson), R2DO (Payne), and NRR EO (Beckner). | ||
| ENS 40428 | 6 January 2004 17:58:00 | 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release 10 CFR 50.72(a)(1)(i), Emergency Class Declaration | Unusual Event Declared Due to Fire on Refuel Floor | Fire reported to control room at 1240 EST 01/06/04. Fire was located inside a portable "Kelly" building on the Refueling Floor which lasted greater than 10 minutes. An Unusual Event was declared at 1258 on 01/06/04. Fire was extinguished at 1302. Fire did not spread beyond the boundary of the Kelly building. The Kelly building was in a contaminated area, but there was no radioactive release outside of the Kelly building. Unusual Event was terminated at 1321. Initial notification to NRC Headquarters of the Unusual Event was made by the NRC Senior Resident Inspector at 1254 EST. At 1303 EST 01/06/04 the decision was made not to enter the Monitoring Phase of Normal Mode of Incident Response for this event. Licensee notified NRC Resident Inspector, State, and Local emergency management authorities. |