Semantic search
| Entered date | Event description | |
|---|---|---|
| ENS 40362 | 29 November 2003 02:47:00 | At 2202 CST, a low Reactor Water Level Scram (Level 3) occurred due to lowering feedwater flow. All control rods inserted on the Scram. The Scram resulted in actuation of HPCI and RCIC on low Reactor Water level (Level 2), and the low level ATWS Recirculation Pump Trip (RPT). HPCI and RCIC initiated and both Reactor Recirculation pumps tripped. It is estimated that RCIC injected approximately 500 to 600 gallons, and HPCI injected less than 100 gallons. HPCI was secured early in the transient, and RCIC operated for approximately 2 minutes. Reactor Water level was recovered and maintained with the operating feedwater pump. The Reactor Water low level (Level 3) also resulted in Group 2 (Primary Containment), Group 3 (Reactor Water Cleanup), and Group 6 isolations (Secondary Containment Isolation and Control Room Ventilation system start). All isolations functioned as designed. Initial indications are that Feedwater Pump B speed lowered unexpectedly, causing Reactor Water level to lower. Reactor Water level reached -44 inches (wide range instruments) (120 inches above top of active fuel). The setpoints for HPCI, RCIC, and ATWS-RPT are -33 inches. Plans are to take the unit to Mode 4. The licensee notified the NRC Resident Inspector. |
| ENS 45489 | 11 November 2009 22:34:00 | On November 11, 2009, at 1743 CST the reactor was manually scrammed following a manual trip of the main turbine due to an un-isolable leak on the Turbine High Pressure Fluid System (TGF) governor valve 3. Initial power level when the leak was identified was approximately 70%. Power was lowered commencing at 1405 in accordance with shutdown procedures. The reactor operator scrammed the reactor at 17:43 from approximately 15% power when directed by the shutdown procedure to place the reactor in a condition to support repairs to the TGF system. In preparation for the scram, level was raised to the range specified in the shutdown procedure (approximately 46 inches). Following the scram, reactor vessel water level lowered to approximately 15 inches on the narrow range instruments, and was subsequently recovered to normal post scram range (approximately 40 inches) using the reactor feedwater system. All control rods fully inserted. No group isolations occurred since level did not reach the isolation setpoint (3 inches). At 1920, the inboard MSIVs were manually closed to stabilize plant cool down and maintain the plant in mode 3. The main condenser remained available throughout the evolution and condenser vacuum is currently being maintained by the mechanical vacuum pumps. Pressure is being controlled using the steam line drains to the main condenser. All equipment operated as expected and there were no difficulties encountered during the evolution. The TGF System has been secured and is in the process of being tagged out for repair. This event is reportable under 10CFR50.72(b)(2)(iv)(B) due to a non planned reactor scram while critical. The licensee has notified the NRC Resident Inspector. The plant is in its normal shutdown electrical lineup. |
| ENS 45856 | 19 April 2010 06:20:00 | At 0158 (CDT) on 4/19/2010, during implementation of clearance order activities, it was identified that the Technical Support Center (TSC) ventilation system would not transition to the emergency mode of operation. This condition is reportable under 10CFR50.72(b)(3)(xiii). The TSC ventilation system consists of normal ventilation equipment, including a normal air supply unit OAF-1, and an emergency air supply unit OAF-2 which provides conditioned air with HEPA and charcoal filtration. The system is placed in the emergency mode as follows: When TSC HEPA FILTER BYPASS switch is placed to EMER UP, the Energy Management System (EMS) receives an emergency signal and the following actions occur: 1. Air Dampers AD1443 and AD1445 close and cause OAF-1 to stop. 2. Air Dampers AD1442 and AD1444 open and cause OAF-2 to start. 3. Outside air to the TSC is routed through HEPA filter unit. During the clearance order activities, the TSC HEPA FILTER BYPASS switch was placed to EMER UP, but the actions above did not occur. A second attempt was made to place the system in the emergency mode, without success. Based upon these indications, it is considered that the TSC ventilation cannot be placed in the emergency mode. This is reportable under 10CFR50.72(b)(3)(xiii) as an event that results in a major loss of emergency assessment capability due to the loss of the emergency response facility. Per Emergency Plan Implementing Procedure 5.7.7 for Activation of TSC, personnel can relocate to the Alternate TSC (control room) and Alternate Operations Support Center (OSC) where the TSC functions will be performed. Both of these alternate facilities are equipped with emergency ventilation systems and are currently fully functional. Troubleshooting of the TSC ventilation system discrepancy will commence today. This system was last tested successfully on 10/20/2008 and due for retest on 6/21/2010. The licensee will inform the NRC Resident Inspector. |
| ENS 46017 | 16 June 2010 17:22:00 | Notification was made to the Nebraska Department of Environmental Quality regarding the inability to conform to the NPDES permit, since the discharges from the sludge pond to the Missouri River are uncontrolled at this time. As a result of high Missouri River levels, the sludge pond was overtopped. The discharges into this pond are subject to NPDES Requirements. The inputs into the sludge pond are described in the NPDES permit as low volume wastewater. There are three outfalls which discharge into the pond. Outfall 002B is described as Clearwell Discharge plus Outfall 004 Emergency Overflow. Outfall 002C is described as Floor Drains. Outfall 004 is described as Reverse Osmosis Reject and Boiler Blowdown Waste streams. Additionally, the high river levels have resulted in media inquiries regarding potential changes in plant operation. Public information personnel and management have responded to these inquiries with information on the impact of river level and preparations for additional actions should conditions warrant additional protective actions. The responses to these inquiries have been referenced in some publications. At the present time, the river appears to be at its crest, with no additional rise forecast. The current level is approximately 3.8 feet below the crest of the 1993 flood, which was the highest flood recorded at the site, and 5 feet below grade elevation. A press release is not planned at this time. The sludge pond does not contain any contaminated material. The licensee will notify the NRC Resident Inspector. |
| ENS 46201 | 24 August 2010 16:57:00 | During planned maintenance on the Startup Station Service Transformer (SSST), an undervoltage condition occurred on the 69 kV offsite power supply to the Emergency Station Service Transformer (ESST). At the time of this event, utility personnel were isolating 161 kV offsite power to the SSST from the grid. As a result, the offsite power voltage to the ESST lowered below the level where the essential 4160 VAC buses are automatically prevented from loading on the ESST. From 0814 to 0816, BKR IFS and 1GS Auto Closure Not Permitted alarms were received when the system control operator was switching out the 161 kV line which supplies the SSST. ESST Secondary Winding voltage lowered to 4309 V and the 69 kV line voltage lowered to 69.4 kV. The nominal setpoint for the Closure not Permitted action is 4330 V. Actions were taken per the alarm response procedures. The ESST was declared inoperable as the automatic closure of the supply breakers to the 4160 V essential buses was precluded. With the SSST already inoperable, LCO 3.8.1 Condition C (two offsite circuits inoperable) was entered for the ESST inoperability. Required action C.1 directs declaring required features inoperable when the redundant required features are inoperable within 12 hours of discovery; and required action C.2 directs restoring one offsite circuit to operable status within 24 hours. At 0816, the system control operator placed the 69 kV capacitor bank in service, restoring the 69 kV line voltage to 71.5 kV and ESST Secondary Winding voltage to 4461 V. At 0846, the ESST was declared Operable following restoration of supply voltage, and meeting acceptance criteria of SR 3.8.1.1, and exited the above LCO required actions for the ESST. The plant remains in LCO 3.8.1, Condition A for the SSST inoperability for planned maintenance. 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. Per the discussion in NUREG 1022, both offsite electrical power and onsite power are considered to be separate functions by GDC 17. Per the GDC, the offsite sources must be capable of automatically connecting to the essential buses within a few seconds. Due to the automatic transfer to the ESST being prevented, the auto transfer function described in the GDC was prevented. The lowest voltage recorded by the system control operator was 69.4 kV, corresponding to 4309 V on the essential 4160 V buses. The 69 kV line voltage was promptly restored, and the Closure not Permitted alarms cleared. The ESST could have been manually aligned to the essential buses during this event. The licensee notified the NRC Resident Inspector. |
| ENS 46391 | 3 November 2010 16:36:00 | At 0813 (CDT), the Cooper Nuclear Station (CNS) Control Room (CR) received a report of a partial neutron water shield drain down on the Dry Fuel On-site Transfer Cask (TC). The TC, with a loaded Dry Storage Cask (DSC), was located in the Reactor Building (RB) Railroad Airlock area. Final preparations were being completed prior to transferring the DSC to Horizontal Storage Module (HSM) 2A. The RB and south side of the Administration Building were cleared of unnecessary personnel. No abnormally elevated RB area radiological readings were noted on CR indication. Local indication in the (Railroad) Airlock from portable radiation monitors indicated abnormally high readings due to the drain down. At 0819 (CDT), CNS entered Abnormal Procedure 5.1 RAD, Building Radiation Trouble. Surveys indicate the top of the TC had readings of about 130 mR/hr neutron at 30cm, which is above the normal readings of 2 mR/hr. Surveys of the bottom portion of the TC indicated a neutron dose rate of 10 mR/hr at 30cm. Actions per 5.1 RAD were subsequently performed. An emergency declaration was not required, because no confinement boundary was adversely affected and neutron levels did not meet a factor of 1,000 over normal levels. Since dose rates were no greater than noted above, and because neutron dose was being directed upward due to the shielding loss being in the upper portion of transfer cask, the Technical Support Center (TSC), which is located in the Administration Building, was determined to support habitability. Furthermore the TSC is provided with additional shielding for personnel protection during an event. This is being reported as a 24 hour report under 10 CFR 72.75(d) for an important to safety fuel storage equipment that failed to function as designed when required to prevent releases, prevent exposures in excess of regulatory limits, or mitigate the consequences of an accident and no redundant equipment was available or operable to perform the required safety function. The cause of the drain down is under investigation. The licensee notified the NRC Resident Inspector. |
| ENS 46563 | 21 January 2011 23:00:00 | 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 1/18/2011 at 1731 CST, it was discovered that the open position indication light for RR-MO-53A, Reactor Recirculation (RR) Pump A discharge valve operator, was de-energized. The RR-MO-53A operator is powered by a 250 VDC motor with 125VDC control power. Investigations revealed that the 125 VDC control power circuit fuses for the valve operator were open. RR-MO-53A must close at a reactor pressure of 199 to 221 psig to allow Residual Heat Removal (RHR) Loop A to inject to the reactor during a LOCA involving Reactor Recirculation Loop B. This condition rendered RHR Loop A Low Pressure Coolant Injection (LPCI) function inoperable. At the time of discovery, RHR Loop B LPCI function was inoperable for planned maintenance. This maintenance was being performed on the service water side of the RHR heat exchanger, RHR-MO-25B, RHR Loop B Injection Outboard Isolation valve operator, RHR pump B motor, and RHR-MO-39B, Suppression Chamber Cooling Loop B Outboard Isolation valve operator. As specified by the Required Action for LCO 3.5.1 Condition H, two or more low pressure ECCS injection/spray subsystems inoperable, LCO 3.0.3 was immediately entered. LCO 3.0.3 requires the plant to be shutdown to Mode 2 within 7 hours. Preparations to commence plant shutdown were initiated in parallel with investigations to determine the cause of the open control power fuses. Subsequent troubleshooting revealed a failed light socket caused the fuses to open. The fuses were replaced and the circuit tested satisfactorily. At 1915 CST on 1/18/2011, RHR Loop A LPCI was declared Operable and LCO 3.0.3 was exited. The plant shutdown procedure was terminated prior to any power reduction occurring. Initial review of this condition for immediate reportability under 50.72(b)(3)(v), Condition that Prevents Fulfillment of a Safety Function, concluded the condition was not reportable based on the availability of Core Spray Pump A (CS-P-A), Core Spray Pump B (CS-P-B ), and RHR Pump D (RHR-P-D). Procedure 2.0.11.1, Safety Function Determination Program, states that Emergency Core Cooling System (ECCS) Safety Function is maintained if three low pressure ECCS Injection/Spray pumps remain operable. CS-P-A, CS-P-B and RHR-P-D all were operable at the time of discovery of the condition. RHR Pump B was restored to available at 1510. The maintenance on RHR Loop B did not remove RHR-P-D from service and an injection path was available at time of discovery of LPCI Loop A inoperable as RHR-MO-25B, RHR Loop B Injection Outboard Isolation valve, post work testing had been completed and the injection capability restored at 1701. Subsequent review determined that the reportability decision under 50.72(b)(3)(v) as a Condition that Prevents 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 simultaneous inoperability of both RHR LPCI Loops under 50.72(b)(3)(v) was made at 1549 on 1/21/2011. The licensee has notified the NRC Resident Inspector. |
| ENS 46941 | 9 June 2011 14:00:00 | Notification was made to the Nebraska Department of Environmental Quality regarding the inability to conform to the NPDES permit, since the discharges from the sludge pond to the Missouri River are uncontrolled at this time. As a result of high Missouri River levels, the sludge pond was overtopped. The discharges into this pond are subject to NPDES requirements. The inputs into the sludge pond are described in the NPDES permit as low volume wastewater. There are three outfalls which discharge into the pond. Outfall 002B is described as Clearwell Discharge plus Outfall 004 Emergency Overflow. Outfall 002C is described as Floor Drains. Outfall 004 is described as Reverse Osmosis Reject and Boiler Blowdown Waste streams. There is no radiological contamination in the pond. Additionally, the current and projected flooding conditions of the Missouri River high river levels have resulted in some media inquiries regarding potential changes in plant operation. Public information personnel and Management have responded to these inquiries with information on the impact of river level and preparations for additional actions should conditions warrant additional protective actions. Current river level is approximately 896 ft. MSL, three feet below the elevation which requires declaration of a NOUE, and approximately 4.8 feet below the crest of the 1993 flood, which was the highest flood recorded at the site. Current river elevation is 7 feet below grade elevation. A press release is not planned at this time. River level is currently projected to be 897.5 ft by Tuesday 6/14. Current river level is characterized as Moderate Flooding by the National Weather Service. There are currently no operational problems due to river conditions. The NRC Resident Inspector has been notified. |
| ENS 46970 | 19 June 2011 22:36:00 | Notification is being made to the Nebraska Department of Environmental Quality regarding the release of oil to the Missouri River from the Cooper Live Fire Training Facility. Currently, levees separating the Training Facility and the Missouri River are being over topped due to flooding of the Missouri River. This condition has resulted in flooding of the burn pits in the fire training facility, with the subsequent release of the residue which includes unburned fuel oil. Any release of this water containing oil to the Missouri River is uncontrolled at this time. Then is no radiological contamination in this area. Current river level is approximately 900.5 ft. MSL, approximately 3.0 feet below plant grade elevation. The fire training area is lower than plant grade. A press release is not planned at this time. River level is currently projected to be 899 ft. by Wednesday 6/22. The licensee notified the NRC Resident Inspector. |
| ENS 48153 | 2 August 2012 15:51:00 | A plant worker was overcome with heat and became unconscious while working in a non-contaminated area inside the Radiological Control Area. Onsite medical personnel determined the individual should be transported to an offsite medical facility for treatment. Radiation protection personnel were unable to fully verify the individual was not contaminated prior to transport to the offsite medical facility. Radiation protection personnel accompanied the individual to the medical facility, and while en route, completed the required surveys. No contamination was found. This report is being made in accordance with 10CFR50.72 (b)(3)(xii) for an event requiring the transport of a potentially radioactively contaminated individual to an off-site medical facility for treatment. The licensee has notified the NRC Resident Inspector. |
| ENS 48237 | 27 August 2012 20:48:00 | At 12:00 CDT maintenance personnel identified a pinhole leak from the Division 1 Service Water System piping in the Service Water Pump Room. Division 1 Service Water (SW) was declared inoperable and LCO 3.7.2 Condition A was entered due to a potential loss of structural integrity. This directs entry into LCO 3.8.1 for Diesel Generator #1 made inoperable by SW. DG 2 was previously made inoperable at 05:39 CDT on 8/25/2012 due to an unrelated issue regarding rain water inleakage into the DG 2 Room. Control Room Emergency Filtration system (CREFs) is aligned to Div 1 power. LCO 3.7.4 Condition A is applicable, requiring restoration of CREFs to operable status within 7 days. TRM LCO 3.6.1 condition A and B also apply, requiring (A) Restoration of containment spray subsystem A to OPERABLE status within 7 days and (B) Restore one RHR containment spray subsystem to operable status within 8 hours. DG 1 and DG 2 comprise the onsite emergency power systems. Both DGs inoperable is reportable per 10CFR50.72(b)(3)(v)(D) as a condition that could prevent fulfillment of the safety function of structures or systems needed to mitigate the consequences of an accident. Actions were taken to expedite repairs of the DG 2 roof leak and to further characterize the Division 1 SW piping leak. LCO 3.8.1 Condition E allows 2 hours to restore one DG to operable status or enter Condition F, to be in Mode 3 in 12 hours, which was entered at 14:00. Repairs to the roof leak on the DG 2 room were completed, after which DG 2 was declared Operable at 18:30. LCO 3.8.1 Conditions E and F required shutdown were exited at this time. LCO 3.8.1 Condition B for DG 1, and 3.7.2 for SW Loop A, continue to be active. Planning to repair the SW piping pinhole leak is continuing. There were no adverse grid conditions during the period both DGs were inoperable. The NRC Resident has been informed of the condition. No media or press release is planned at this time.
This notification is being made to retract Event Notification EN #48237 which reported a loss of safety function due to both onsite Emergency Diesel Generators (DGs) being simultaneously INOPERABLE. On 8/25/12 at 0539 CDT, DG#2 was declared INOPERABLE due to rain water in-leakage into the DG#2 room. Condition B of LCO 3.8.1 was entered. and Required Actions were being taken to restore the INOPERABLE DG within 7 days. Subsequently, on 8/27/12 at 1200 CDT Maintenance personnel identified a pinhole leak from the Division I Service Water System piping in the Service Water Pump Room. Division I Service Water was declared INOPERABLE and LCO 3.7.2 Condition A was entered due to a potential loss of structural integrity. This prompted entry into LCO 3.8.1 Conditions E and F which require shutdown, because DG#1 was made INOPERABLE by SW. Both DG's INOPERABLE is reportable per 10CFR50.72.b.3.v.D as a condition that could prevent fulfillment of a safety function of structures or systems needed to mitigate the consequences of an accident. Repairs to the roof leak on the DG#2 room were completed, after which DG#2 was declared Operable at 1830 CDT on 8/27/2012. LCO 3.8.1 Conditions E and F were exited at the time. LCO 3.8.1 Condition B for DG#1, and 3.7.2 for SW Loop A, continued to be active, and planning to repair the pin-hole leak continued. Subsequent investigation and UT examinations provided data which enabled SW Division 1 and DG#1 to be declared OPERABLE on 8/30/2012 at 0528 CDT. An evaluation of this condition concluded that further characterization of the SW Piping Pin-Hole leak enabled ASME Code Case N-513-3 to be applied to determine piping structural integrity was maintained. SW ability to supply required flows to its loads is not adversely diminished, because the flaw is small. Water leaking from the flaw will not adversely affect any other equipment important to safety by spray or flooding. The piping is compliant with ASME code. Based on this evaluation, the Division 1 SW system can perform its safety function and is OPERABLE. With Division 1 SW subsystem capable of fulfilling its safety function, DG#1 was therefore also capable of fulfilling its safety function during the period of SW subsystem INOPERABILITY. Consequently, during the period of DG#2 INOPERABILITY, DG#1 was capable of fulfilling the safety function of the onsite emergency power system. NPPD therefore retracts Event Notification EN 48237. The NRC Resident has been informed of this retraction. Notified R4DO (Azua). |
| ENS 48429 | 22 October 2012 03:49:00 | During a walkdown evaluating potential for adverse consequences of site flooding, per 10CFR50.54(f) request, a condition was identified which had the potential to adversely impact the ability to address external flooding conditions. The old Emergency Offsite Facility (which currently houses information technology offices) has a drain pipe which connects to Sump AA in the Augmented Radwaste (ARW) building and bypasses the flooding barriers erected per maintenance procedure 7.0.11 in the event of site flooding. Per the USAR, the basis for site flooding is a flood with concurrent surge effects on exposed safety related structures reaching an elevation of 905 feet. This elevation is 2.0 feet above the grade elevation of 903 feet. Flooding protection for important site facilities is provided by installing temporary barriers protecting to elevation 906 feet. Primary and Secondary Flood Barriers are installed at the ARW building external entrances on the 903 feet elevation to protect the Reactor Building from external flood water. The drain piping from the old EOF floor drain and shower is piped directly to Sump AA in the ARW building basement. This is a 3 inch pipe which drains by gravity. There are no isolation features on the pipe, and no barriers to flooding are provided for this facility, thus the potential exists to bypass the flood barriers which would be erected around the ARW Building. Flooding of the building basement could result, disabling processing equipment. If the basement fills up, flood waters could enter the Reactor Building through the internal entrance, which has no additional protection installed. Floodwaters could then affect equipment which is required to remove residual heat. This condition has been determined to be reportable per 50.72(b)(3)(v) - Any event or condition that at the time of discovery could have prevented the fulfillment of the safety function of SSCs that are needed to remove residual heat. The potential condition was identified on 10/20/2012. Evaluation of the condition and the potential impact was completed and reportability determined on 10/22/2012. The condition has been entered into the Corrective Action Program. The licensee notified the NRC Resident Inspector.
During a walk down evaluating the potential for adverse consequences of site flooding per 10CFR50.54(f) request, a condition was identified which had the potential to adversely impact the ability to address external flooding conditions. The Optimum Water Chemistry (OWC) building has 5 floor drains, at ground level elevation 903 ft, which connect to a common 3 inch drain pipe which connects to a sanitary sump located in the Turbine building, at an elevation of 882 ft, and bypasses all flooding barriers erected per maintenance procedure 7.0.11 in the event of site flooding. Per the USAR, the basis for site flooding is a flood with a concurrent surge effect on exposed safely related structures reaching an elevation of 905 ft. This elevation is 2 ft above the grade of the floor drains. Flooding protection for important site facilities is provided by installing temporary barriers which provide protection to an elevation of 906 ft. Primary and secondary barriers are installed at the Turbine building external entrances to protect the Reactor building from external flood waters. Additional secondary barriers are erected inside the Turbine building to provide additional protection to the Diesel Generator rooms. The drain piping from the OWC building floor drains is piped directly to the sanitary sump located in the Turbine building. There are no isolation features on the piping and no barriers to flooding are erected between the Turbine building and Reactor building thus the potential exists to bypass the flood barriers erected around the Turbine building. Flooding of the Turbine building could result in the accumulation of water in sufficient quantities to fill the Turbine building 882.5ft elevation to the height of the external floodwaters which would then be allowed to flow unimpeded by flooding barriers to the Reactor building through the internal entrance which has no additional barriers installed. These floodwaters could then affect equipment, located within the Reactor building, which is required to remove residual heat. This condition has been determined to be reportable per 50.72(b)(3)(v) - Any event or condition that at the time of discovery could have prevented the fulfillment of the safety function of SSC's. that needed to remove residual heat. This condition was identified at 1550 (CDT on) 10/22/2012 and has been entered into the Corrective Action Program. The licensee informed the NRC Resident Inspector. Notified R4DO (Hagar).
This notification is being made to retract Event Notification EN #48429 which reported a loss of safety function due to the discovery of two flow paths (one from the old Emergency Operating Facility and one from the Optimum Water Chemistry building) where an external event flood event at 905 feet would result in flooding of the Turbine and Radwaste basement and eventually the Reactor building basement. Upon further review, the design basis Probable Maximum Flood for CNS is 903 feet. The two water entry points discussed in the Event Notification are above the 903 foot elevation. Wave energy would be dissipated before reaching any of the main buildings so there would be a minimal influx of water into the structures. As such, there is no loss of safety function for equipment in the Reactor building basement. NPPD therefore retracts Event Notification EN #48429. The NRC Resident Inspector has been notified. Notified R4DO (Farnholtz). |