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| Start date | Reporting criterion | Title | Event description | System | LER | |
|---|---|---|---|---|---|---|
| ENS 49618 | 9 December 2013 14:00:00 | 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release 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 Declared Due to Unit 2 Auxiliary Transformer Explosion | At approximately 0748 (CST) on 12/9/2013, an electrical fault occurred resulting in a fire and explosion on the ANO (Arkansas Nuclear One) Unit 2 Unit Auxiliary Transformer. This caused a unit trip and a loss of power to Startup 3 Transformer, which is one of the two offsite power feeds to ANO Unit 2. ANO Unit 2 is currently in a stable shutdown condition. With Startup 3 and Unit Aux Transformer unavailable, power was lost to the Reactor Coolant Pumps and Circulating Water Pumps. RCS (Reactor Coolant System) natural circulation is in progress removing core decay heat. Emergency Feedwater actuated due to low steam generator levels and is supplying both steam generators. The unit is steaming to the atmosphere. 2A-1 and 2A-3 are powered from SU (Startup) 2 Transformer. 2A-4 is powered from 2K-4B Emergency Diesel Generator. ANO Unit 1 is currently operating at 98% power. The auto transformer tripped off line with the fault in ANO Unit 2 Unit Auxiliary Transformer. This has caused Startup Transformer 1 to be inoperable. This places ANO Unit 1 in a 72 hour Technical Specification action statement (T.S 3.6.1 for Loss of the SU-1 Transformer). No significant injuries were reported as a result of this condition and offsite agencies have been notified. At 0800 on 12/9/2013 Unit 2 declared a Notification of Unusual Event based on EAL HU4 Fire or Explosion inside Protected Area not extinguished in 15 minutes. At 0917 on 12/9/2013, the fire on Unit 2 Unit Auxiliary Transformer is OUT. The Licensee notified the NRC Resident Inspector. Notified DHS SWO, DOE Ops Center, FEMA Ops Center, HHS Ops Center, NICC Watch Officer, USDA Ops Center, EPA EOC, and Nuclear SSA vial email.
At 1215 CST, ANO terminated from the Unusual Event as per HU4 stable plant conditions. ANO Unit 2 is stable and will be cooled down to Mode 5 via natural circulation and decay heat is being removed via emergency feedwater and downstream dump valves to atmosphere. There is no radiological release and no personnel injuries. The licensee has notified the NRC Resident Inspector, Arkansas Department of Emergency Management, Arkansas Department of Health, and other local authorities. Notified R4DO (Vasquez), NRR EO (King) and IRC MOC (Morris). Notified DHS SWO, DOE Ops Center, FEMA Ops Center, HHS Ops Center, NICC Watch Officer, USDA Ops Center, EPA EOC, and Nuclear SSA vial email.
Outside agencies (National Response Center, Arkansas Department of Emergency Management, Corps of Engineers, and U.S. Coast Guard) were contacted due to a minor unknown amount of oil that entered the plant discharge to Lake Dardanelle. The oil was from the faulted Unit 2 Unit Auxiliary Transformer. The majority of oil was contained within the containment around the transformer or the oily water separator it drains to. Local inspection revealed only a small amount of what was released actually passed the containment booms that are continuously in place on the discharge canal. The oil boom was verified to be in good condition. The oil was verified to be mineral oil. The release was verified to be terminated. An additional oil boom was deployed. Reference (ANO) Condition Report CR-ANO-C-2013-03071. The licensee notified the NRC Resident Inspector. Notified the R4DO (Werner) | Steam Generator Feedwater Emergency Diesel Generator | |
| ENS 48869 | 31 March 2013 15:33:00 | 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release 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 | Notification of Unusual Event Declared Due to a Breaker Explosion in the Protected Area | At 0750 (CDT) on 3/31/2013, during movement of the Unit 1 Main Turbine Generator Stator (~500 tons), the Unit 1 turbine temporary lift device failed. This caused a loss of all off-site power on Unit 1. The ANO Unit 1 #1 and #2 EDG (Emergency Diesel Generator) have started and are supplying A-3 4160V switchgear and A-4 4160V switchgear. P-4A Service Water pump and P-4C Service Water pump has been verified running. Unit 1 has entered (procedures) 1202.007 - Degraded Power, 1203.028 - Loss of Decay Heat, and 1203.050 - Spent Fuel Emergencies. Unit 1 is in MODE 6. ANO-1 entered TS 3.8.2 A, 'One Required Offsite Circuit Inoperable'. All required actions are complete. The event caused a loss of decay heat removal on ANO Unit 1 which was restored in 3 minutes and 50 seconds. Unit 2 tripped and is in MODE 3. Emergency Feed Water was initiated on Unit 2 and Unit 2 was in (Technical Specification) 3.0.3 from 0817 (CDT) to 0848 (CDT) due to Emergency Feedwater. Unit 2 is being powered by off-site. Unit 2 Startup 3 (transformer) lock out at 0921 (CDT). (Bus) 2A1 is on Start up 2 (transformer) and (bus) 2A3 is on #2 EDG. 10CFR50.72 (b)(3)(iv)(A) - 4-hr. notification due to the ES (Engineered Safeguard Feature) actuation on both Unit 1 and Unit 2. 10CFR50 72 (b)(2)(iv)(B) - 4-hr. notification due to RPS (Reactor Protection System) actuation on Unit 2. 10CFR50.72 (b)(2)(xi) - 4-hr. notification due to Government Notification. 29CFR1904.39a - (OSHA) 8-hr. notification due to death on site. At 1033 (CDT) on 3/31/2013, Unit 2 entered a Notification of Unusual Event based on EAL HU4 due to damage in 2A1 switchgear. Notification of the NUE will be made lAW Emergency Plan requirements. Follow-up notifications will be made as appropriate. At this time, the full extent of structural damage on Unit 1 is not known. There was one known fatality and 4 known serious injuries to workers. The local coroner is on site for the fatality and the injured personnel have been transported offsite to local hospitals. Investigation into the cause of the failure and extent of damage is ongoing. On Unit 2, all rods inserted during the trip. The core is being cooled via natural circulation. Decay heat is being removed via steam dumps to atmosphere. There is no known primary to secondary leakage. The licensee has notified the State of Arkansas, local authorities, OSHA and the NRC Resident Inspector. Notified DHS SWO, DHS NICC, FEMA and Nuclear NSSA (via email).
The licensee terminated the NOUE at 1821 CDT. The basis for termination was that the affected bus (2A2) is de-energized and no other equipment on Unit 2 was damaged. The licensee has notified the state and local authorities and will be notifying the NRC Resident Inspector. Notified R4DO (Pick), NRR EO (Howe), IRD (Gott), DHS SWO, DHS NICC, FEMA and Nuclear SSA (via email).
The licensee made the following edits to the third paragraph of their original report (edits in quotes): Unit 2 tripped and is in MODE 3. Emergency Feed Water initiated on Unit 2. Unit 2 was in (Technical Specification) 3.0.3 from 0817 (CDT) to 0848 (CDT) due to Emergency Feedwater "being procedurally overridden." Unit 2 "was initially" being powered by off-site. Unit 2 Startup 3 Lock out occurred at 0921. 2A1 is now on Startup 2, and "2A4" is on #2 EDG. Notified R4DO (Kellar) via email. | Feedwater Service water Main Turbine Decay Heat Removal | |
| ENS 46555 | 20 January 2011 02:58:00 | 10 CFR 50.72(a)(1)(i), Emergency Class Declaration | Notice of Unusual Event Due to a Security Event | The licensee declared an unusual event based upon a potential security incident at the site. Contact the Headquarters Operations Officer for additional details. The NRC Resident Inspector has been notified. | ||
| ENS 44837 | 7 February 2009 16:59:00 | 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation 10 CFR 50.72(a)(1)(i), Emergency Class Declaration | Unusual Event Declared Due to a Fire Onsite | Arkansas Nuclear One Unit 1 declared an Unusual Event per EAL 7.5 at 1059 CST based on a fire onsite. The fire occurred on the 354 foot elevation iso-phase bus deck of the turbine building. The fire was attributed to a failed bonnet on a manual valve which had unthreaded during operation releasing hydrogen in the vicinity of the hydrogen add station. The licensee extinguished the fire using water and posted a reflash watch. There were no reported personnel injuries. Offsite assistance was requested from the London Fire Department which arrived onsite after the fire had been extinguished. The reactor was manually tripped with all control rods fully inserting. The plant is currently stable with decay heat removal via the steam dumps to the main condenser. The licensee informed state/local agencies and the NRC Resident Inspector.
The Unusual Event was terminated at 1338 CST after confirmation that the fire was extinguished and a review of the exit criteria as defined in plant procedures. The licensee is performing a damage assessment at this time. The licensee was in the process of informing state/local agencies and will inform the NRC Resident Inspector. Notified R4DO (Clark), NRR(Hiland), IRD (Grant), DHS (Banner) and FEMA (Canupp).
The subject event notification erroneously reported that all control rods fully inserted following the manual reactor trip initiated in response to a fire on site. In actuality, the rod bottom light for Rod 6 in Rod Group 7 on the CRD Position Indication Panel did not illuminate following the reactor trip and it was verified by plant computer to have inserted to 2.3 percent withdrawn. The control board operator identified this condition quickly and reported it to the Control Room Supervisor in his immediate action response. This condition did not necessitate any additional operator actions and shutdown margin requirements were maintained. The licensee has informed the NRC Resident Inspector. R4DO (Miller) notified. | Decay Heat Removal Main Condenser Control Rod | |
| ENS 43742 | 24 October 2007 04:05:00 | 10 CFR 50.72(a)(1)(i), Emergency Class Declaration | Alert Declared Due to Electrical Fire in the Auxiliary Building | At 2305 an Alert condition was declared based on Emergency Action Level (EAL) 7.6, "Fire or Explosion Onsite Affecting One Train of ESF Systems." The fire was out at the time of the notification. There was no gaseous radiological release. There were no injuries. The plant continues to operate at full power. The licensee is still assessing the full impact of any damage. The licensee notified the NRC Resident Inspector. * * * UPDATE AT 0044 ON 10/24/07 FROM JEFF GERARD TO PETE SNYDER * * * Smoke is dissipating." The Alert condition is still in effect. There is no radiological release. There was no explosion. * * * UPDATE AT 0256 ON 10/24/07 FROM FRED VAN BUSKIRK TO PETE SNYDER * * * The Alert condition was terminated at 0133 CDT since inspections of the local area confirmed that the fire had been extinguished. | ||
| ENS 42949 | 30 October 2006 19:04:00 | 10 CFR 50.72(a)(1)(i), Emergency Class Declaration 10 CFR 50.72(b)(2)(i), Tech Spec Required Shutdown | Alert Declaration Due to Electrical Fire Affecting One Esf Train | At 1304 CT on 10/30/06, the licensee declared an Alert due to a fire in a breaker compartment in safety-related 480 VAC Bus 2B-53. The bus feeder breaker tripped open, resulting in the loss of some safety equipment, including one train of emergency feedwater. The fire was immediately extinguished. The licensee notified the NRC Resident Inspector.
ANO-2 Technical Specification 3.6.3.1 action compliance is in progress which includes plans to commence plant shutdown starting at approximately 1908 hours (CT). Parallel repair efforts are underway to restore the necessary portions of 2B-53 power to allow exiting the Technical Specification 3.6.3.1 LCO's. The licensee notified the NRC Resident Inspector. Notified R4 DO (D. Powers) and R4 IRC (Kennedy).
At 1925 hours (CT) on 10/30/06, Shutdown of Unit 2 to Hot Standby was commenced in accordance with Technical Specification 3.6.3.1 Action D. This notification satisfies the requirement of 10CFR50.72(b)(2). The licensee notified the NRC Resident Inspector. Notified R4 DO (D. Powers) and R4 IRC (Kennedy).
At 1925 hours (CT), Shutdown of Unit 2 was commenced in accordance with Technical Specification 3.6.3.1. The termination criteria of OP-1903.010, Section 6.3 have been met and the Alert has been terminated (at 2000 CST). The licensee will notify the NRC Resident Inspector. Notified R4 DO (D. Powers), R4 IRC (Kennedy), NRR EO (Lubinski), NSIR (Leach, Blount, Wilson), HQ PAO (Brenner), Comm TA's (Lee, Brown, Skeen, Hatchett, Piccone), EDO Staff (Lamb - message), DHS SWO (Bozzo), FEMA (Casto), DOE (Foote), NRC (McCrossen), USDA (Giles), HHS (Harris) | Feedwater |