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| Entered date | Event description | |
|---|---|---|
| ENS 53167 | 16 January 2018 10:06:00 | This 60-day telephone notification is being made under reporting requirements specified by 10 CFR 50.73(a)(2)(iv)(A) to describe an invalid actuation of a containment isolation signal affecting more than one system. At 2230 CST on November 30, 2017, with the Duane Arnold Energy Center (DAEC) operating at 100 percent power, an invalid Group 3 isolation on the 'B' side of the Primary Containment Isolation System (PCIS) occurred. Group 3 isolation signals were generated for Primary Containment Isolation Valves for Drywell and Torus Ventilation and Purge, Containment Nitrogen Compressor Suction and Discharge, Recirculation Pump Seals, and Post Accident Sample System. This event was caused by a fault on the 1D25 Instrument AC Inverter. The fault was caused by an insufficient design clearance to ground and was corrected by increasing the clearance. All equipment responded in accordance with the plant design. Specifically, all actuations were complete and successful. There were no safety consequences or impacts on the health and safety of the public. The event was entered into DAEC's corrective action program for resolution. The NRC Resident Inspector has been notified. |
| ENS 51863 | 12 April 2016 14:36:00 | On April 12, at 1235 CDT, Duane Arnold Energy Center contacted officials with the State of Iowa (Bureau of Radiological Health and Department of Natural Resources) and Linn County Public Health Department in accordance with the nuclear industry voluntary reporting criteria contained in NEI 07-07 'Industry Ground Water Protection Initiative'. The site contacted the agencies as courtesy to notify them about the identification of low levels of tritium found within the site's protected area from a potential new source. Samples were taken, and no regulatory limits were exceeded. The site team is working with industry experts on pinpointing the cause and installing an extraction well to remediate the situation. This report is being made in accordance with 10 CFR 50.72(b)(2)(xi), as a result of notification to offsite agencies. The Licensee has notified the NRC Resident Inspectors. There is no risk to plant employees, the public or drinking water. |
| ENS 49151 | 27 June 2013 11:33:00 | This 60-day telephone notification is being made under reporting requirements specified by 10CFR50.73(a)(2)(iv)(A) to describe an invalid actuation of a containment isolation signal affecting more than one system. At 1307 CDT on May 2, 2013, with the Duane Arnold Energy Center (DAEC) operating at 100% power, an invalid Group 3 isolation on the 'A' side of the Primary Containment Isolation System occurred. Group 3 isolation signals were generated for Primary Containment Isolation Valves for Drywell and Torus Ventilation, and Purge, Containment Nitrogen Compressor Suction and Discharge, Recirculation Pump Seals, and Post Accident Sample System. This event was caused by a human performance error that led to a blown fuse. Specifically, the fuse failed during pre-planned maintenance on a differential pressure switch when a test clip made inadvertent contact with an energized part of the switch. All equipment responded in accordance with the plant design. Specifically, all actuations were complete and successful. There were no safety consequences or impacts on the health and safety of the public. The event was entered into DAEC's corrective action program for resolution. The licensee notified the NRC Resident Inspector. |
| ENS 48767 | 19 February 2013 13:31:00 | This 60-day telephone notification is being made under reporting requirements specified by 10 CFR 50.73(a)(2)(iv)(A) to describe an invalid actuation of a containment isolation signal affecting more than one system. At 0354 CST on December 20, 2012, with the Duane Arnold Energy Center (DAEC) operating at 100% power, an invalid Group 3 isolation on the 'A' side of the Primary Containment Isolation System occurred. Group 3 isolation signals were generated for Primary Containment Isolation Valves for Drywell and Torus Ventilation, and Purge, Containment Nitrogen Compressor Suction and Discharge, Recirculation Pump Seals, and Post Accident Sample System. This event was caused by spurious upscale spike on the 'A' Refuel Floor Exhaust Radiation Monitor. All equipment responded in accordance with the plant design. Specifically, all actuations were complete and successful. There were no safety consequences or impacts on the health and safety of the public. The event was entered into DAEC's corrective action program for resolution. The licensee notified the NRC Resident Inspector. |
| ENS 48601 | 18 December 2012 11:20:00 | This 60-day telephone notification is being made under reporting requirements specified by 10CFR50.73(a)(2)(iv)(A) to describe an invalid actuation of a containment isolation signal affecting more than one system. At 1920 on October 20, 2012, with the Duane Arnold Energy Center (DAEC) shut down for a preplanned refueling outage, an invalid Group 3 isolation on the 'A' side of the Primary Containment Isolation System occurred. Group 3 isolation signals were generated for Primary Containment Isolation Valves for Drywell and Torus Ventilation, and Purge, Containment Nitrogen Compressor Suction and Discharge, Recirculation Pump Seals, and Post Accident Sample System. This event was caused by failed components in the power supply circuitry for the 'A' Refuel Floor Exhaust Radiation Monitor. All equipment responded in accordance with the plant design. Specifically, all actuations were complete and successful. There were no safety consequences or impacts on the health and safety of the public. The event was entered into DAEC's corrective action program for resolution. The licensee notified the NRC Resident Inspector. |
| ENS 48403 | 12 October 2012 17:02:00 | On October 12, at 1535 CDT, Duane Arnold Energy Center made a voluntary report to the State of Iowa (Bureau of Radiological Health and Department of Natural Resources) and Linn County Public Health Department in accordance with the nuclear industry voluntary reporting criteria contained in NEI 07-07, 'Industry Ground Water Protection Initiative.' The subject of the report was a leak from the Condensate Storage Tanks' containment pit sump. The release occurred in an isolated area inside the plant property and has been terminated. Samples were taken and no regulatory limits were exceeded. During and following the leak, there was no impact to site worker or public health and safety. This report in being made in accordance with 10 CFR 50.72(b)(2)(xi), as a result of notification to offsite agencies. The Licensee has notified the NRC Resident Inspector. Total amount leaked was estimated to be less than 100 gallons. |
| ENS 47511 | 8 December 2011 14:33:00 | This condition is being reported in accordance with 10CFR50.72(b)(3)(v) as a condition that could have prevented fulfillment of a safety function. On 12/02/2011 at 1311 CST, the Low Pressure Coolant Injection (LPCI) was declared inoperable when voiding was discovered in the 'B' Residual Heat Removal (RHR) inject vent line. Initial review of this condition for immediate reportability under 50.72(b)(3)(v), event or condition that could have prevented fulfillment of a safety function, concluded the condition was not reportable based on the availability of other Emergency Core Cooling Systems (ECCS). Specifically, Core Spray and HPCI were both available to perform the function of emergency core cooling. On 12/03/2011 at 1650 CST, LPCI was declared operable based on further examinations to determine extent of voiding, system filling and venting and completion of supporting engineering evaluations. Subsequent reviews determined that the reportability decision under 50.72(b)(3)(v) as a event or condition that could have prevented fulfillment of a safety function should be based on safety function at the system level, rather than at the ECCS function level. The decision to report the inoperability of LPCI under 50.72(b)(3)(v) was made at 1319 CST on 12/08/2011. The licensee has notified the NRC Resident Inspector. |
| ENS 47143 | 11 August 2011 15:29:00 | At 1138 CDT, while in the process of shutting down as required by Technical Specifications (Reference EN# 47142), with the reactor at approximately 15 percent power, a manual scram was inserted in order to complete the TS Required Action of being in Mode 3 within 12 hours. Upon inserting the manual scram, reactor water level dropped below 170 inches resulting in Primary Containment Isolation System (PCIS) Groups 2, 3 and 4 being received. This reactor water level response is considered normal following a reactor scram from power due to void collapse in the reactor vessel. Reactor water level is currently being controlled in the normal band. All PCIS group isolations went to completion and were subsequently reset. The PCIS isolations all functioned properly. This event is being reported pursuant to 10 CFR 50.72(b)(3)(iv)(A). The NRC Resident Inspector has been notified. |
| ENS 46954 | 13 June 2011 15:19:00 | This 60-day telephone notification is being made under reporting requirements specified by 10CFR50.73(a)(2)(iv)(A) to describe an invalid actuation of a containment isolation signal affecting more than one system. At 2043 on April 14, 2011, with the Duane Arnold Energy Center (DAEC) operating at 100% power, an invalid Group 3 isolation on the 'A' side of the Primary Containment Isolation System occurred. Group 3 isolation signals were generated for Primary Containment Isolation Valves for Drywell and Torus Ventilation, and Purge, Containment Nitrogen Compressor Suction and Discharge, Recirculation Pump Seals, and Post Accident Sample System. This event was caused by a high resistance contact on connectors in the detector circuitry for the 'A' Reactor Building Vent Shaft Radiation Monitor. All equipment responded in accordance with the plant design. Specifically, all actuations were complete and successful. There were no safety consequences or impacts on the health and safety of the public. The event was entered into DAEC's corrective action program for resolution. The licensee notified the NRC Resident Inspector. |
| ENS 46724 | 5 April 2011 11:58:00 | This 60-day telephone notification is being made under reporting requirements specified by 10CFR50.73 (a)(2)(iv)(A) to describe an invalid actuation of a containment isolation signal affecting more than one system. At 1354 on February 4, 2011, with the Duane Arnold Energy Center (DAEC) operating at 100% power, an invalid Group 3 isolation on the 'B' side of the Primary Containment Isolation System occurred. Group 3 isolation signals were generated for Primary Containment Isolation Valves for Drywell and Torus Ventilation, and Purge, Containment Nitrogen Compressor Suction and Discharge, Recirculation Pump Seals, and Post Accident Sample System. This event was caused by a high resistance contact on relays in the trip circuitry for the 'B' Fuel Pool Exhaust Radiation Monitor logic. All equipment responded in accordance with the plant design. Specifically, all actuations were complete and successful. There were no safety consequences or impacts on the health and safety of the public. The event was entered into DAEC's corrective action program for resolution. The licensee notified the NRC Resident Inspector. |
| ENS 46410 | 10 November 2010 13:49:00 | On November 10, 2010, at approximately 0518 hours, with the plant in Mode 5 during Refueling Outage (RFO) 22, the 'A' Residual Heat Removal (RHR) pump tripped while operating in the shutdown cooling mode resulting in an interruption of the primary means of decay heat removal for approximately 30 minutes. During this period the maximum increase in reactor temperature was approximately 2 degrees Fahrenheit with a calculated time to boil of approximately 33.9 hours. There was no loss of decay heat removal due to the fact that both trains of Fuel Pool Cooling system and the Reactor Water Cleanup system remained in service. At the time of this event, the plant was in the process of restoring motive power to MO-1909, Outboard Shutdown Cooling Isolation valve. Motive power had previously been isolated to the valve as part of a preplanned evolution of transferring the power supply to 'B' Reactor Protection System (RPS). Due to a failure to isolate the control power to MO-1909 when RPS power had been transferred, MO-1909 automatically closed when motive power had been restored due the existence of a Primary Containment Isolation System (PCIS) signal that was initiated when 'B' RPS power had been transferred. The closure of MO-1909 resulted in the isolation of the common shutdown cooling pathway, and therefore prevented both the 'A' and the 'B' RHR systems from removing decay heat. Preliminary investigations into this event indicate that the failure to isolate control power to MO-1909 occurred due to an existing procedure deficiency for transferring RPS power supplies. As a result of the closure of MO-1909, Operations entered Abnormal Operating Procedure (AOP) 149, Loss of Decay Heat Removal, and Technical Specification (TS) Limiting Condition for Operations (LCO) 3.9.7 Condition A; Required RHR Shutdown Cooling Subsystem Inoperable and performed the required actions of the AOP and TS. At approximately 0547, shutdown cooling was restored when the 'C' RHR pump was placed in shutdown cooling. TS 3.9.7 and AOP 149 were subsequently exited at 0551. During the duration of this event adequate decay heat removal existed as part of the site's Shutdown Risk Management in that two loops of Fuel Pool Cooling were in-service and Feed and Bleed utilizing the Control Rod Drive pumps was available. Additionally, Reactor Water Cleanup was in service and remained in service for the duration of this event. Note that RHR shutdown cooling was considered available during this event due to the fact that there were no component failures associated with MO-1909 preventing it from being immediately re-opened. This event is being reported as an event or condition that at the time of discovery could have prevented fulfillment of a safety function of structures or systems that are needed to remove residual heat under 10 CFR 50.72 (b)(3)(v)(B). The (NRC) Resident Inspectors have been notified. |
| ENS 45189 | 8 July 2009 13:10:00 | NextEra Energy Duane Arnold (NextEra Energy) makes the following notification under 10 CFR 21.21(d)(3)(i) of a failure to comply found during surveillance testing. The specific issue is insufficient clearance between the spring and the inside of the cylinder of the actuator for a Miller series A63B2N air cylinder actuator for a control valve (CV-1956A, Control Building Chiller Discharge to Emergency Service Water Isolation). The resulting improper clearance caused an increase in running load, which caused the valve to become stuck in the closed position. The valve failure was discovered on May 10, 2009. The control valve actuator was supplied by Flowserve US, Inc, as a basic component in April, 2008 for use at the Duane Arnold Energy Center. Flowserve has indicated that the actuator was procured as a commercial grade item and dedicated for safety related installation under their QA program. The valve and actuator were installed on April 17, 2009. The lack of spring to actuator clearance resulted in a loss of capability of CV-1956A to perform its intended safety function of providing a safety related seismic discharge path for cooling water from the safety related Control Building Chiller, 1V-CH-1A. The Chiller was declared inoperable as a result of this failure to comply and, on July 1, 2009 was determined to have resulted in a substantial safety hazard. The actuator for CV-1956A was rebuilt with a replacement spring having proper dimensional clearance and higher opening force capability. The actuator has been installed by a plant modification and the control building chiller has been returned to an operable status. The air operated valve assembly supplier, Flowserve US Inc, was contacted on July 1, 2009 to discuss NextEra Energy's findings. NextEra Energy has verified that no other safety related actuators with the incorrect valve actuator cylinder to spring clearances have been installed at the Duane Arnold Energy Center. The NRC Resident Inspector has been notified. |
| ENS 43692 | 5 October 2007 11:30:00 | On October 5, 2007, at approximately 0408, while attempting to open 480 VAC breaker 1B4234A/B for preplanned maintenance, a loss of bus 1B42 occurred. The preliminary cause of the bus trip was arcing of the bucket stabs/bus bars when opening the door to breaker 1B4234A/B. The arcing was a result of the breaker bucket inadvertently pulling away from the bus. At the time of this event, the 'A' Emergency Service Water (ESW) pump was out of service for preplanned maintenance. The loss of 1B42 resulted in a loss of the 'B' ESW pump. The 'A' ESW pump was subsequently returned to service at 0458 on October 5, 2007. Note that power was conservatively lowered approximately 4% at 0512. At the time of this power reduction, the plant was not in a Technical Specification that would require a plant shutdown. In addition to the loss of the 'B' ESW pump, the loss of 1B42 resulted in invalid Group 1-5 isolations on the 'B' side of PCIS (not including Main Steam Line Isolation Valves). This event is reportable under 10 CFR 50.72(b)(3)(v), Any event or condition that alone at the time of discovery could have prevented the fulfillment of the safety function of structures or systems that are needed to (D) Mitigate the consequences of an accident. The licensee notified the NRC Resident Inspector." The licensee has not yet determined if this is a mechanical failure of the breaker or a human error. However, they are looking at OE associated with this issue.
The licensee provided the following information as an update: In addition to the ESW loss of safety function that occurred, it has been determined that from 0408 till approximately 0715 on 10/05/07, a loss of both onsite emergency AC power sources occurred. Specifically, at the time of the event, the 'A' Emergency Diesel Generator (EDG) was out of service for preplanned maintenance. When bus 1B42 was lost, this resulted in a loss of 'B' ESW. The loss of 'B' ESW resulted in the 'B' EDG being incapable of performing its safety function. Therefore, this is another example of an event or condition that could have prevented the fulfillment of a safety function needed to mitigate the consequences of an accident. The licensee informed the NRC Resident Inspector. Notified R3DO (Hills).
On 10/05/07, this event was reportable under 10 CFR 50.72(b)(3)(v), Any event or condition that alone at the time of discovery could have prevented the fulfillment of the safety function of structures or systems that are needed to (D) Mitigate the consequences of an accident due to the loss of both ESW pumps. Further reviews have determined that the 'A' ESW pump was available at the time of the event and therefore, this event is not reportable for a loss of the ESW safety function. This event is still reportable for a loss of the on-site emergency AC power safety function. The licensee notified the NRC Resident Inspector. Notified the R3DO (Lara). |
| ENS 41760 | 9 June 2005 14:12:00 | This 60-day telephone notification is being made under reporting requirements specified by 10CFR50.73 (a)(2)(iv)(A) to describe an invalid actuation of a containment isolation signal affecting more than one system. At 1540 on April 14, 2005, with the Duane Arnold Energy Center (DAEC) shutdown for refueling, an invalid Group 3 isolation on the 'A' side of PCIS occurred. Group 3 isolation signals were generated for Primary Containment Isolation Valves for Drywell and Torus Ventilation, and Purge, Containment Nitrogen Compressor Suction and Discharge; Recirculation Pump Seals, and Post Accident Sample System. This event was caused while landing a lead on a relay terminal. During this activity the lead brushed another terminal, causing a fuse to blow which resulted in the inadvertent Group 3 isolation. All equipment responded In accordance with the plant design. Specifically, all actuations were complete and successful. There were no safety consequences or impacts on the health and safety of the public. The event was entered into DAEC's corrective action program for resolution. The licensee will notify the NRC Resident Inspector. |
| ENS 41759 | 9 June 2005 14:12:00 | This 60-day telephone notification is being made under reporting requirements specified by 10CFR50.73 (a)(2)(iv)(A) to describe an invalid actuation of a containment isolation signal affecting more than one system. At 0613 on April 14, 2005, with the Duane Arnold Energy Center (DAEC) shutdown for refueling, a PCIS Group 7 (Well Water and RBCCW Drywall Isolation Valves) signal was generated during post-maintenance testing on MO-4841A. This event was caused by an error in work planning which resulted in an incorrect relay being listed in a work order. When a jumper was installed across the terminals of the incorrect relay, an isolation signal was generated. All equipment responded in accordance with the plant design. Specifically, all isolations were complete and successful. There were no safety consequences or impacts on the health and safety of the public. The event was entered into DAEC's corrective action program for resolution. The licensee will notify the NRC Resident Inspector. |