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| Entered date | Event description | |
|---|---|---|
| ENS 56174 | 22 October 2022 17:36:00 | The following information was provided by the licensee via fax: During Mode 5 Refueling operations, while attempting to establish flow through the Fuel Pool Cooling system filter demineralizers, an air operated valve to a radioactive waste tank failed to close automatically. This caused the Fuel Pool Cooling system to pump water from the Skimmer Surge Tanks (SST) to the radioactive liquid waste system. In response to the loss of inventory from the SSTs, the Control Room operating crew started Core Spray Pump A to restore normal operating level In the SST. This prevented the loss of the Fuel Pool Cooling/Alternate Decay Heat Removal system which was the only in service system meeting the safety function of decay heat removal. Core Spray Pump A was used for Injection for less than 3 minutes. This is reportable as a discharge of ECCS into the RCS in response to an event, but not part of a pre-planned sequence under 10 CFR 50.72(b)(2)(iv)(A) and actuation of a specified system under 10 CFR 50.72(b)(3)(Iv)(A). The resident inspector has been notified. The following additional information was obtained from the licensee in accordance with Headquarters Operations Officers Report Guidance: Licensee reported approximately 6000-7000 gallons of water was injected into the RCS. The stuck open air operated valve was closed. Proceeding with refueling outage operations. |
| ENS 55981 | 7 July 2022 22:49:00 | The following information was provided by the licensee via phone and fax: On 7/7/2022, at 0740 CDT, the National Weather Service reported to Cooper Nuclear Station that the NAWAS ((National Warning System)) radio tower near Shubert, Nebraska would neither transmit nor receive. The Shubert Tower transmitter activates the EAS ((Emergency Alert System))/Tone Alert Radios used for public notification. Additional information from the National Weather Service received 7/7/2022 at 1601 (CDT) determined that the Shubert Tower transmitter is non-functional and would not likely be repaired within 24 hours. The backup notification system has been verified to be available throughout this period. This is considered to be a major loss of the Public Prompt Notification System capability. The primary notification system is not expected to be restored to service within 24 hours, and therefore this condition is reportable under 10 CFR 50.72(b)(3)(xiii), since the backup alerting methods do not meet the primary system design objective. The backup notification system is available to use for notifications if needed. The NRC Senior Resident has been informed. The following additional information was obtained from the licensee in accordance with Headquarters Operations Officers Report Guidance: The backup notification system has to be manually activated. |
| ENS 54232 | 20 August 2019 18:28:00 | At 0939 CDT, on 8/19/19, the National Weather Service reported to Cooper Nuclear Station that the National Warning System (NAWAS) Radio would neither transmit nor receive. The system has been intermittently available since then, but never declared fully functional. The backup notification system has been verified to be available throughout this period. Additional information from the National Weather Service received 8/20/19 at 1414 determined that the Shubert Tower transmitter is non-functional and would not be repaired until 8/21/19. The transmission outage is conservatively assumed to have begun at the first notification on 8/19/19 at 0939. The Shubert Tower transmitter activates the (EMERGENCY ALERT SYSTEM) EAS/Tone Alert Radios used for public notification. This is considered to be a major loss of the Public Prompt Notification System capability and is reportable under 10 CFR 50.72(b)(3)(xiii) when the primary notification system is or will be unavailable for greater than 24 hours with the backup system available. The NRC Senior Resident has been informed. |
| ENS 53941 | 16 March 2019 13:42:00 | At approximately 1100 CDT on March 15, 2019, Cooper Nuclear Station was notified by the National Weather Service that the Shubert radio transmission tower was not functioning due to evacuating their office in Omaha as a result of local flooding. This affects the tone alert radios used to notify the public in event of an emergency condition. Loss of function of this tower is reportable at 1100 CDT on March 16, 2019, when the tower could not be restored within 24 hours of the loss. This condition is reportable under 10 CFR 50.72(b)(3)(xiii). A backup notification method is available and will be utilized for notifications if needed. A return to service time for the Shubert tower is not currently available. The NRC Senior Resident Inspector has been informed. |
| ENS 53128 | 19 December 2017 17:17:00 | During regular power operations at 100% power, DG#1 and DG#2 were declared inoperable due to a common issue associated with indicating lights and the associated sockets installed in various control and auxiliary circuits for both DG's. The indicating lights in question are incandescent 120V AC style 120MB bulbs in a socket with a 550 ohm resistor. Style 120MB light bulbs have a failure mechanism where the bulb can cause a short circuit rather than the more common open circuit that is expected when an incandescent bulb filament fails. Cooper originally believed that the socket's integral resistor was sufficient to protect the circuit. In testing performed by an outside laboratory and confirmed on-site using warehouse stock, it was determined that the integral resistor may not have the power dissipation capability to protect the circuit ln which the light and socket are installed if a bulb fails in short circuit. This condition resulted in both DG's being declared inoperable at 1340 (CST) due to a loss of reasonable expectation that they would meet their safety function required action to start, load and run to support loads required to mitigate the consequences of an accident. This is a loss of safety function under 10CFR 50.72(b)(3)(v)(D) subject to an 8 hour report. As a result of both DG's being inoperable, the Control Room Emergency Filtration System is also inoperable. This is also a loss of safety function subject to an 8 hour report for the same criterion. The Senior Resident has been notified.
CNS is retracting the 8-hour non-emergency notification made on December 19, 2017 at 1340 CST (EN# 53128). Subsequent evaluation concluded a postulated lamp short circuit failure in any of the affected circuits would not impact the ability of the Diesel Generators to perform their safety function and therefore, were operable. With DG operability not affected, the Control Room Emergency Filtration System also remained operable. The NRC Resident Inspector has been notified. Notified the R4DO (Werner). |
| ENS 53074 | 16 November 2017 08:17:00 | At 0008 CST on 11/16/2017, Cooper Nuclear Station (CNS) was notified by Omaha Weather that the NOAA broadcast and the Shubert radio tower for this area is off. This affects the tone alert radios used to notify the public in event of an emergency condition. This is considered to be a major loss of the Public Prompt Notification System capability, and is reportable under 10CFR50.72(b)(3)(xiii). The transmission outage actually began at 2007 (CST), 11/15/2017, but CNS was not notified until 0008 (CST), 11/16/2017. Backup notification methods remained available throughout the period. At time 0447 CST on 11/16/2017, Cooper Nuclear Station was notified that the NOAA broadcast and Shubert radio transmission tower was returned to service. Nemaha County, NE, Richardson County, NE, and Atchison County, MO authorities within the 10 mile EPZ were notified by Cooper Nuclear Station of the condition and the effect on the tone alert radios at 0642 (CST), 11/16/2017. This is reportable under 10CFR50.72(b)(2)(xi) as a 4 hour report. The NRC Senior Resident has been informed. |
| ENS 48430 | 22 October 2012 13:28:00 | At 0642 (CDT) on 10/22/2012 a failure of power supply RMA-ES-53B was indicated by multiple area radiation alarms in the Control Room. This failure results in the loss of ability to remotely measure and quantify radiation levels in multiple area in the Reactor Building, Turbine Building and Main Control Room. This power supply serves 10 of 30 area radiation monitors located throughout the plant. The remaining 20 monitors remain fully functional. These radiation monitors do not cause entry to any Technical Specification conditions or required actions. The loss of ability to monitor and quantify radiological conditions in multiple area of the plant represents a major loss of emergency assessment capability per 10CFR50.72(b)(3)(xiii). These radiation monitors are used for EAL determinations. As specified by station procedures compensatory monitoring has been implemented by use of surveys and portable monitoring devices. Repairs are being implemented per station procedures and processes. The licensee informed the NRC Resident Inspector. |
| ENS 48405 | 13 October 2012 11:33:00 | At approximately 0320 CDT on 10/13/2012, Cooper Nuclear Station personnel identified portions of the onsite telephone system are not responding normally, following reports of a lightning strike in the vicinity of the meteorological tower. Personnel performed checks of onsite and offsite communications capability, and determined the normal method of contacting the state and local agencies would not function. Alternate methods were checked, and found to be only partially functional. This is considered to be a major loss of the offsite communications capability, and is reportable under 10CFR50.72(b)(3)(xiii). Alternate methods of contacting state and local agencies are available using working phones and the site cell phone system to obtain an offsite phone line and dial the direct line as listed in the emergency telephone directory. State and local agencies must be contacted individually. The capability to activate the ERO paging backup system per the implementing procedures is not affected by this condition. Communication personnel will respond to the site to correct the condition. The licensee has notified the NRC Resident Inspector and will be notifying state and local agencies.
This is a follow-up notification to EN 48405. At 1407 CDT on 10/13/2012, the normal method of contacting state and local agencies during an emergency has been restored. The licensee has notified state and local agencies and will be notifying the NRC Resident Inspector. Notified R4DO (Hagar). |
| ENS 45482 | 6 November 2009 23:22:00 | On November 6, 2009, at 1930 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). The RO (Reactor Operator) scrammed the reactor when (reactor vessel water) level lowered below 12 inches on the Narrow Range Instruments. All Control Rods fully inserted and a Group 2 Isolation occurred when level reached 3 inches on the Narrow Range Instruments. Reactor level lowered to approximately 22 inches on the Wide Range Instruments and was recovered in a slow and deliberate manner in order to minimize the effect on the cool down rate because of low levels of decay heat in the fuel. The Reactor Feed System was used to initially recover level. At 2043, the plant was in Mode 3 with the inboard MSIVs manually closed and level and pressure being controlled by RCIC. The MSIVs were closed to minimize the cool down rate and RCIC was started manually for level and pressure control. The Main Condenser remained available throughout the evolution and condenser vacuum is currently being maintained by the Mechanical Vacuum Pumps. The Group 2 Isolation was verified with no discrepancies and was reset at approximately 2010. 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. The licensee has notified the NRC Resident Inspector. |
| ENS 44689 | 30 November 2008 08:22:00 | On 30 November 08 at 0158, the Control Room Emergency Filtration System (CREFS) was declared inoperable due to a degraded Control Room Envelope (CRE). A CRE boundary door was found to be stuck partially open. With this door not fully closed and latched, reasonable assurance that CREFS would fulfill its safety function could not be established. The CRE door is a support features for CREFS at CNS. This is a single train system and per 10CFR50.72(b)(3)(v)(D) an 8 hour report is required due to the fact that at the time of discovery this condition could have prevented the fulfillment of the safety function of an SSC (Structure, System & Components) that is required to mitigate the consequences of an accident. The door was returned to a fully closed and latched position at the time of discovery, and CREFS was returned to operable status. Administrative controls are in place to ensure the door closes and latches until repairs can be performed. The licensee notified the NRC Resident Inspector. |
| ENS 44402 | 9 August 2008 05:24:00 | While performing main turbine reheat stop valve surveillance testing, Reheat Stop Valve 1RV 1A failed to reopen simultaneously with a Moisture Separator C high level alarm. Plant alarm response procedures require a reactor scram in this situation. Operating crew inserted a manual scram at 0204 CDT. Immediately after the scram, RPV level responded as expected and dropped below the Group 2 containment isolation setpoint. All rods inserted fully. RPV level is being controlled with RFP A and the startup valves. RPV pressure is being controlled on the bypass valves. The Group 2 isolation was complete with no anomalies. This report is being submitted pursuant to 50.72(b)(2) for RPS actuation (4 hour report) and 50.72(b)(3) for a valid Group 2 isolation (8 hour report). The scram was characterized as uncomplicated. The lowest reactor vessel water level reached was - 20 inches. No safeties lifted during the transient and all systems functioned as required. The cause of the reheat stop valve failure to reopen is under investigation. The NRC Resident Inspector has been notified. |
| ENS 43421 | 14 June 2007 14:20:00 | During verification of plant procedures associated with achieving safe shutdown during and after an Appendix R fire, it was determined that there was no readily available success path to secure HPCI when required. The scenario in question involves a fire-induced spurious HPCI initiation that must be terminated within 10 minutes to prevent flooding main steam lines and disabling both available methods of hot shutdown. For this event, RCIC is one defined method of temperature and pressure control to achieve hot shutdown. The other defined method requires ADS valves to lower pressure to allow CS to provide makeup water. As written, the procedure steps provided to Operations personnel would not have been sufficient to isolate steam to the HPCI turbine. All other methods to secure HPCI that would have been reasonably available required operation of components that could have been affected by the same fire that caused the spurious initiation of HPCI. The procedures have been changed to provide Operations personnel adequate and effective instructions to isolate HPCI when required after a spurious initiation during an Appendix R fire. This is being reported under 10 CFR 50.72(b)(3)(v)(A) as a condition that could have prevented the plant from achieving safe shutdown. The Senior Resident Inspector has been notified. |
| ENS 43375 | 19 May 2007 05:26:00 | On the evening of 5/10/2007, Cooper began a scheduled down power to accomplish required preventive and corrective maintenance, including replacement of directional control valves on three control rod drive (CRD) hydraulic control units (HCU). HCU 26-27 was hydraulically isolated for maintenance. The plant was in a single recirculation loop configuration to perform corrective maintenance on 'A' Recirculation Motor Generator. A single reactor feed pump was in operation for corrective maintenance to the 'A' Reactor Feed Pump lube oil system. At approximately 0025 CDT on 5/19/2007 reports from the field indicated that a small water leak had developed from the body to bonnet seal of CRD-V-122 for HCU 26-27. The manual isolation valves for the HCU were already closed to isolate the maintenance area. However, due to seat leakage past one or both of the manual isolation valves, the leakage continued and degraded to the point that a visible plume of steam was issuing from the valve. Further, high airborne activity level developed in the vicinity of the HCU bank in the Reactor Building. As a precaution, the Control Room supervisor (CRS) evacuated the Reactor Building at 0125 CDT. At 0200 CDT, the CRS entered the station reactor scram procedure and performed the preparation steps of transferring electrical loads to the startup transformer. At 0212 CDT, the reactor was manually scrammed. All rods inserted normally. A Group 2 containment isolation signal was received on low reactor water level at 3". During the recovery, the remaining reactor feed pump was manually tripped at 50" in accordance with station procedures due to high RPV level conditions. 'B' RFP was restarted when conditions permitted and is being used to control RPV level. RPV pressure is being controlled by the bypass valves rejecting heat to the main condenser. This report is being submitted pursuant to 50.72 (2)(iv) for a critical scram and specified system actuation for the Group 2 containment isolation. Currently, the leak into the Reactor Building has stopped. Radiological conditions are being assessed and a repair and recovery plan developed. The Senior Resident Inspector has been informed. The scram was characterized as uncomplicated and all systems functioned as required. No personnel contaminations or off-site releases occurred due to the HCU valve leak. |