Semantic search
| Start date | Reporting criterion | Title | Event description | System | LER | |
|---|---|---|---|---|---|---|
| ENS 57002 | 1 March 2024 19:45:00 | 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release | Inadvertent Siren Activation | The following information was provided by the licensee via email: At 1330 CST, on March 1, 2024, an equipment vendor was coordinating with Wright County performing maintenance on an emergency siren when the county operator mistakenly sent an alarm signal instead of cancel signal, activating all Wright County emergency sirens for approximately 17 seconds. At 1345 CST, the Monticello Nuclear Generating Plant (MNGP) emergency planning coordinator received a notification from the vendor and notified the duty shift manager (of the inadvertent activation). Wright County officials are planning to make a public notification via social media to local residents. No press release by the licensee is planned at this time. This event is reportable per 10 CFR 50.72(b)(2)(xi), 'News Release or Notification of Other Government Agencies.' This is a 4-hour Reporting requirement. The NRC Resident has been notified. | ||
| ENS 56995 | 28 February 2024 14:39:00 | 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation 10 CFR 50.72(b)(3)(iv)(A), System Actuation | Automatic Reactor Scram | The following information was provided by the licensee via fax and email: At approximately 0839 (CST) with Unit 1 in Mode 1 at 100 percent power, the reactor automatically scrammed due to the depressurization of the SCRAM air header caused by an invalid signal that (occurred) during system testing. The SCRAM was uncomplicated with all systems responding as expected. The cause and details of the event are under investigation. Containment isolation valves actuated and closed on a valid Group 2 signal. Due to the reactor protection system actuation while critical, this event is being reported as a four-hour, non-emergency notification per 10 CFR 50.72(b)(2)(iv)(B), and an eight-hour, non-emergency notification per 10 CFR 50.72(b)(3)(iv)(A) for the Group 2 isolation signal. Operations responded using the emergency operating procedure and stabilized the plant in Mode 3. Decay heat is being removed by discharging steam to the main condenser using the turbine bypass valves. There was no impact on the health and safety of the public or plant personnel. The NRC Resident Inspector has been notified. State as well as Wright and Sherburne Counties will be notified. The following additional information was obtained from the licensee in accordance with Headquarters Operations Officers Report Guidance: The Anticipated Transient Without Scram (ATWS) circuit was being tested when an invalid signal was sent to depressurize the SCRAM air header. | Reactor Protection System Main Condenser | |
| ENS 56759 | 27 September 2023 15:41:00 | 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation 10 CFR 50.72(b)(3)(iv)(A), System Actuation | Actuation of Reactor Protection and Containment Isolation Systems | The following information was provided by the licensee via fax: (On 09/27/2023) at 1041 CDT, with the plant at 75 percent power and main turbine control valve testing in progress, a reactor pressure transient resulted in a reactor steam dome high pressure scram and subsequent group 1 primary containment isolation of the main steam lines (MSL). All main steam isolation valves closed as a result of the group 1 isolation signal. Additionally, a group 2 containment isolation signal was received due to reactor pressure vessel (RPV) level less than plus 9 inches during the transient. Operations personnel responded and stabilized the plant. The high-pressure coolant injection (HPCI) system was placed in service to control RPV pressure. HPCI did not inject into the RPV and was not needed to control RPV water level. The cause of the initial pressure transient is under investigation. The NRC Resident Inspector has been notified.
The utility notified the State of Minnesota and Wright and Sherburne counties. Notified R3DO (Orlikowski) | Main Steam Isolation Valve Primary containment Reactor Pressure Vessel Main Steam Line | |
| ENS 56535 | 22 May 2023 23:38:00 | 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release | Notification to Another Government Agency | The following information was provided by the licensee via phone and fax: On 5/22/23, Xcel Energy performed a notification to the state of Minnesota Duty Officer, in accordance with Minnesota Statute 115.061, regarding 300-600 gallons of pumped ground water that overflowed from a holding tank and returned to the ground area from which it was pumped. The groundwater being pumped is related to recovery activities associated with the event reported on November 22, 2022 (EN 56236). This notification is being made solely as a four-hour, non-emergency report for notification to other government agency. An update is being provided to the Monticello community and published on Xcel Energy's website. This event is reportable in accordance with 10 CFR 50.72(b)(2)(xi). There was no impact on the health and safety of public or plant personnel. The NRC Resident Inspector has been notified. | ||
| ENS 56236 | 22 November 2022 21:30:00 | 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release | Notification of Environmental Report to Another Government Agency | The following information was provided by the licensee via email: On 11/22/2022, Monticello Nuclear Generating Plant initiated a voluntary communication to the State of Minnesota after receiving analysis results for an on-site monitoring well that indicated tritium activity above the (Offsite Dose Calculation Manual) ODCM and Nuclear Energy Institute (NEI) Groundwater Protection Initiative (GPI) reporting levels. The source of the tritium is under investigation and the station will continue to monitor and sample accordingly. This notification is being made solely as a four-hour, non-emergency report for a Notification of Other Government Agency. This event is reportable in accordance with 10 CFR 50.72(b)(2)(xi). There was no impact on the health and safety of the public or plant personnel. The NRC Resident Inspector has been notified. | ||
| ENS 52715 | 28 April 2017 21:43:00 | 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release | Offsite Notification for Release of Wastewater | This report is being made pursuant to 10 CFR 50.72(b)(2)(xi), as an event where notification to other government agencies has been made. On April 28, 2017, notification to the Minnesota State Duty Office was made due to a non-compliance with release of wastewater requirements in the Monticello Nuclear Generating Plant's National Pollutant Discharge Elimination System permit. There were no consequences to the health and safety of the public. The licensee notified the NRC Resident Inspector. | ||
| ENS 52682 | 15 April 2017 09:41:00 | 10 CFR 50.72(b)(3)(iv)(A), System Actuation | Valid Reactor Protection System and Partial Primary Containment Isolation System Actuations on Low Water Level | During shutdown activities with the reactor subcritical, actions were being taken to remove 11 Reactor Feed Pump from service in support of a scheduled refueling outage. Reactor Water Level on Safeguards level instrumentation dropped below +9 inches, which resulted in a valid Reactor Protection System (RPS) Scram signal and Partial Group 2 Primary Containment Isolation System (PCIS) signal. All systems functioned as required. Reactor Water Level on Safeguards instrumentation was restored to greater than +9 inches immediately. RPS and PCIS logic was reset. There was no impact to the health and safety of the public as a result of this event. This actuation of these systems is being reported per 10 CFR 50.72(b)(3)(iv)(A) as an event that resulted in a valid actuation of any of the systems listed in 10 CFR 50.72(b)(3)(iv)(B). The NRC Resident Inspector has been notified. | Reactor Protection System Primary Containment Isolation System | |
| ENS 52156 | 5 August 2016 15:14:00 | 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release | Offsite Notification Due to Drinking Water Exceeding Limits | On 8/5/2016 at 1014 (CDT), the Monticello Nuclear Generating Plant (MNGP) was notified by the Minnesota Department of Health (MDH) of a notice of violation for exceeding the drinking water limit for carbon tetrachloride in the drinking water well that supplies the Security Access Facility. Additionally the MDH will be notifying the Minnesota Pollution Control Agency regarding the violation. As a result, this issue is being reported under 10CFR50.72(b)(2)(xi) for notifications to other offsite government agencies. There was no impact to the health and safety of the general public as a result of this issue. The drinking fountains in the Security Access Facility have been isolated. The NRC Resident Inspector has been notified. | ||
| ENS 52020 | 18 June 2016 07:59:00 | 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release | Spurious Emergency Siren Activation | On 6/18/16 at approximately 0259 CDT, the Monticello Nuclear Generating Plant was notified by the Wright County Sheriffs Office of a spurious actuation of one emergency siren in the city of Monticello. As a result, this issue is being reported under 10CFR50.72(b)(2)(xi) for notifications to other off site government agencies as the licensee was notified by the Wright County Sheriff's Office. The source of the siren activation has not been determined. Wright County Sheriff's Office successfully deactivated the siren at 0322 CDT. There was no impact to the health and safety of the public as a result of this event as the offsite response capabilities remain functional with a single siren failure. The site is operating normally with no emergency conditions present. The NRC Resident Inspector has been notified. The licensee will notify the State of Minnesota concerning this event. | ||
| ENS 51566 | 24 November 2015 18:53:00 | 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release | Offsite Notification for a Discharge Canal Temperature Change Causing a Fish Kill | At 1253 CST on 11/24/2015, XCEL Energy Environmental Services made a report to the Minnesota Pollution Control Agency (MPCA) and the Minnesota Department of Natural Resources (DNR) due to the recorded total fish loss (59) as a result of the Monticello Plant's discharge canal temperature change following the reactor scram on 11/23/2015. This notification is being made under 10 CFR 50.72(b)(2)(xi) based on a notification to another government agency. This issue has no safety significance and no impact on the health and safety of the general public. NRC Resident Inspector has been notified. | ||
| ENS 51560 | 23 November 2015 16:40:00 | 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation 10 CFR 50.72(b)(3)(iv)(A), System Actuation | Reactor Scram Due to a Reactor Recirculation Pump Lockout | At 1040 CST, with the plant at 100% power, a lockout of the 11 recirculation pump occurred. Following the 11 recirculation pump lockout, at 1041 CST, a reactor scram and a Group 1 isolation occurred. All Main Steam Isolation Valves closed as a result of the Group 1 isolation signal. HPCI (High Pressure Core Injection) has been placed in service to control RPV (Reactor Pressure Vessel) pressure. HPCI did not inject into the RPV and was not needed to control RPV level. At 1104 CST, a Group 2 containment isolation signal was received due to RPV level less than +9 inches. The Group 2 isolation signal has been reset. The cause(s) of the 11 recirculation pump lockout, the reactor scram, and the Group 1 isolation are currently not known and are under investigation. This event is being reported under 50.72(b)(2)(iv)(B) due to the actuation of the Reactor Protection System when the reactor is critical. For the following reasons, this event is also being reported under 50.72(b)(3)(iv)(A): 1) This event resulted in a valid Group 2 containment isolation signal, 2) Since the cause of the Reactor Protection System actuation is not known, the event is being reported as a valid actuation of the Reactor Protection System, and 3) Since the cause of the Group 1 isolation is not known, the event is being reported as a valid primary containment isolation signal affecting multiple Main Steam Isolation Valves. All systems have responded as expected, all control rods fully inserted following the Reactor Protection System actuation. The plant is currently shutdown in mode 3, RPV pressure and RPV level are stable. This event did not result in any radiological release from the plant. This event did not challenge the health and safety of the public. The NRC Resident Inspector has been notified. The plant is in its normal shutdown electrical lineup. HPCI is in pressure suppression mode with RHR cooling the suppression pool. | Reactor Protection System Main Steam Isolation Valve Primary containment Reactor Recirculation Pump Control Rod | |
| ENS 51306 | 10 August 2015 20:35:00 | 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release | Inadvertent Activation of a Single Emergency Siren | On August 10, 2015, at approximately 1555 CDT, the licensee was notified that emergency siren S-07 in Sherburne County, MN had inadvertently activated from approximately 1525-1538 CDT. The cause of the activation is under investigation. The siren vendor (NELCOM) was also contacted and made the notification to the licensee. As a result, this issue is being reported under 10CFR50.72(b)(2)(xi) for notifications to other offsite government agencies as the licensee was notified by the Sherburne County Sherriff's Office. The source of the activation signal has not been determined. The vendor is investigating. The siren is no longer actuating. There was no impact to the health and safety of the public as a result of this event as the offsite response capabilities remain functional with a failure of only 1 out of 106 total sirens. The site is operating normally with no emergency present. (The) NRC Resident Inspector has been notified. The licensee will notify the State. | ||
| ENS 51241 | 20 July 2015 13:55:00 | 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release | Offsite Notification Due to Spurious Actuation of Emergency Siren | On 7/20/2015 at approximately 0931 CDT, the Monticello nuclear generating plant was notified by Wright County Sheriffs Office of a spurious actuation of one emergency response siren in the city of Monticello that occurred at approximately 0855 CDT (lasted for approximately three minutes). This actuation was confirmed by vendor system monitoring. As a result, this issue is being reported under 10 CFR 50.72(b)(2)(xi) for notifications to other offsite government agencies as the licensee was notified by the Wright County Sheriffs Office. The source of the activation signal has not been determined. The vendor is investigating. The siren is no longer actuating. There was no impact to the health and safety of the public as a result of this event as the offsite response capabilities remain functional with a single siren failure. The site is operating normally with no emergency conditions present. The NRC Resident Inspector has been notified. The State of Minnesota will be notified. | ||
| ENS 50052 | 23 April 2014 15:00:00 | 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release | Offsite Notification Due to Deceased Migratory Bird Found on Plant Property | Monticello Nuclear Generating Plant personnel discovered the remains of a deceased migratory bird on plant property. The cause of death was not immediately apparent and no work was ongoing in the vicinity at the time the bird was found. Notifications to the United States Fish and Wildlife Service will be made for this discovery. This event is being reported per 10CFR50.72(b)(2)(xi). The licensee has informed the NRC Resident Inspector. | ||
| ENS 50049 | 22 April 2014 19:00:00 | 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release | Offsite Notification Due to Deceased Migratory Bird Found on Plant Property | Monticello Nuclear Generating Plant personnel discovered the remains of a deceased migratory bird on plant property. The cause of death was not immediately apparent, no work was ongoing in the vicinity at the time the bird was found. Notifications to the Minnesota Department of Natural Resources and the Division of Fish and Wildlife will be made for this discovery. This event is being reported per 10CFR50.72(b)(2)(xi). The NRC Resident Inspector will be informed. | ||
| ENS 50026 | 11 April 2014 02:00:00 | 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release | Offsite Notification Due to a Dead Duck Found on Site | Monticello Nuclear Generating Plant personnel discovered the remains of what appeared to be a deceased duck on plant property. The cause of death was not immediately apparent, no work was ongoing within the vicinity at the time. Notifications to the Minnesota Department of Natural Resources and the Division of Fish and Wildlife will be made for this discovery. This event is reported per 10CFR50.72(b)(2)(xi). The licensee has notified the NRC Senior Resident Inspector. Plant personnel could not determine if the duck was an endangered species. | ||
| ENS 49876 | 5 March 2014 21:00:00 | 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release 10 CFR 72.75(b)(2), Offsite Notification | Offsite Notification Due to Dry Shielded Canister Test Results | This report is being made to provide information to the NRC regarding Monticello Dry Shielded Canister (DSC)-16. On February 17, 2014, dye penetrant examinations were performed on the outer top cover plate (OTCP) to shell weld on dry shielded canister (DSC)-16. This was a re-examination of a linear indication identified on January 24, 2014. The results of the re-examination identified a 1.6 inch linear indication that remained after surface conditioning. This indication had not been previously detected by nonconforming nondestructive examination previously reported by TriVis Inc. Xcel Energy is evaluating the condition and will remedy prior to moving the cask to the ISFSI (Independent Spent Fuel Storage Installation) pad. The associated DSCs loaded during the current campaign successfully passed their helium leak tests. Helium leak checks are performed to demonstrate confinement and boundary integrity. Thus, public health and safety is not affected. Since the licensee communication plan also notified other government agencies, this report is being made pursuant to 10CFR50.72(b)(2)(xi) and 72.75(b)(2). The above referenced dry shielded canister is currently located on the refuel floor in the reactor building. The licensee notified the NRC Resident Inspector. | ||
| ENS 49741 | 18 January 2014 09:38:00 | 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release | Offsite Notification Due to Discharge Canal Temperature Drop | At 0338 CST, Xcel Energy Environmental Services made a report to the State of Minnesota due to cooling water return to the Mississippi River via the plant's discharge canal dropping by more than 5 deg F per hour. The cause of the temperature drop was due to a required time limited reactor shut down. The reactor is currently shut down with all systems responding as expected. This notification is being made under 10 CFR 50.72(b)(2)(xi) based on a notification to another government agency. The NRC Resident Inspector has been notified
At 1130 EST on 1/20/2014, XCEL Energy Environmental Services made a report to the State of Minnesota (Minnesota Pollution Control Agency and the Minnesota Department of Natural Resources) due to the recorded total fish loss (207) as a result of the Monticello Plant's discharge canal temperature change per above. This is an update notification only and has no safety significance and no impact on the health and safety of the general public. The licensee notified the NRC Resident Inspector. Notified the R3DO (Skokowski). | ||
| ENS 49714 | 11 January 2014 07:00:00 | 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release | Offsite Notification Due to Decreasing Discharge Temperature | At 0205 CST (on 1/11/14), Xcel Energy Environmental Services made a report to the State of Minnesota due to cooling water return to the Mississippi River via the plants discharge canal dropping by more than 5 degrees F in an hour. The cause of the temperature drop was due to an emergent reduction in reactor power and generator load in response to a degrading condenser vacuum. This notification is being made under 10 CFR 50.72(b)(2)(xi) based on a notification to another Government Agency. The NRC Resident Inspector has been notified. | ||
| ENS 49181 | 8 July 2013 22:00:00 | 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release | Offsite Notification Due to Sodium Hypochlorite Spill | On July 8th, 2013, at approximately 1730 CDT, the Minnesota State Duty Officer was notified of an approximately 50 gallon sodium hypochlorite spill onsite. The spill has been contained and clean-up is in progress. There was no actual or potential impact on the environment and no impact on the health and safety of the public or onsite personnel. The licensee will also be notifying Wright County. The NRC Resident Inspector has been informed. | ||
| ENS 49113 | 13 June 2013 19:30:00 | 10 CFR 50.72(b)(3)(v)(B), Loss of Safety Function - Remove Residual Heat 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident 10 CFR 50.72(b)(3)(iv)(A), System Actuation 10 CFR 50.72(b)(3)(v)(C), Loss of Safety Function - Release of Radioactive Material | Emergency Diesel Generators Start | While preparing for an equipment test Thursday afternoon, Monticello Nuclear Generating Plant lost off-site power on its normal off-site power feed. Power for safety related loads was automatically transferred to the alternate off-site power source. The Emergency Diesel Generators started as designed but did not load onto the safety related busses due to the availability of off-site power. Operators stabilized the plant, which is shutdown for a refueling and maintenance outage, in less than an hour and are investigating the cause of the event. The current plant focus is on restoring the normal off-site power feed. The event posed no danger to the public or plant workers, and no one was injured. There was no release of radiation. Plant safety systems continue to be powered by the backup off-site power feed, with the emergency diesel generators available if needed. Event Specifics: At approximately 1430 CDT, during a refueling outage with the plant in Mode 4, reactor level at approximately 200 inches, and a full Scram already inserted, a loss of normal off-site power occurred due to a fault in a non-safety related bus supply breaker. The fault was in the 13.8 KV supply breaker to the #11 bus. This caused the Station 2R transformer to lockout, resulting in a loss of the normal off-site power to Essential Busses 15 and 16. Shutdown Cooling (SDC) was lost for approximately 1 hour due to loss of supply power and isolation of the common suction valves. Both 11 and 12 Emergency Diesel Generators (EDGs) automatically started but did not load onto their respective busses (as designed) due to the 1AR emergency off-site transformer re-energizing both 15 and 16 bus. This essential bus transfer is being reported as a 'Valid actuation of emergency AC electrical power systems' under 10CFR50.72(b)(3)(iv). During the event the decision was made to shut down the EDGs which rendered them inoperable for a short period of time until the Fast Start capability was reset. The period of time that the EDGs were inoperable is being reported as a 'Condition that could have prevented the fulfillment of the safety functions to remove residual heat, control the release of radioactive material, and mitigate the consequences of an accident under 10CFR50.72(b)(3)(v)(B), (C), and (D). Both EDGs have been restored to Automatic Standby Status and are operable. The loss of power resulted in a Group II Containment Isolation signal causing secondary containment to isolate and Standby Gas Treatment and Control Room Emergency Filtration to initiate as well as associated Group II Containment Isolation Valves to close. This is being reported as a 'General containment isolation signal ESF actuation' under 10CFR50.72(b)(3)(iv). The containment isolation has been reset, and SDC and SFPC have been restored. Reactor temperature rose approximately 4 degrees F during the event from 161 degrees to 165 degrees which remained in the prescribed operating band. Reactor level did not change. The licensee has notified the NRC Resident Inspector. | Secondary containment Emergency Diesel Generator Shutdown Cooling | |
| ENS 49066 | 24 May 2013 08:34:00 | 10 CFR 50.72(b)(3)(iv)(A), System Actuation | Automatic Start of Emergency Diesel Generator Due to Bus Undervoltage | At 0334 (CDT) on 5/24/2013 MNGP (Monticello Nuclear Generating Plant) experienced a loss of power to Bus 15 (Division 1 4kV Essential Bus) during performance of preoperational testing on the 2R reserve transformer which initiated an Essential Bus Transfer of Bus 15 and automatic start of 12 Emergency Diesel Generator. MNGP was in Mode 5 operations with water level >21 feet 11 inches above the top of the RPV flange and all credited safety systems were lined up to Bus 16 (Division 2 4kV Essential Bus) which was unaffected by this event. Bus 15 was automatically repowered from the 1AR reserve transformer as designed. During this evolution all critical safety functions remained green and all systems responded as expected to the Essential Bus transfer. The cause of the sequence of events that led to the Bus 15 loss of power is being investigated. This event is reportable under 10CFR50.72(b)(3)(iv) as an event that results in a valid actuation of 12 Emergency Diesel Generator. The NRC Resident Inspector has been notified. | Emergency Diesel Generator | |
| ENS 49010 | 8 May 2013 11:23:00 | 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release | Emergency Siren Spurious Actuation | On 5/8/2013 at 0623 (CDT) MNGP was informed by Wright County Sheriffs Department of a spurious actuation of one emergency response siren in Wright County (for about 2 seconds). This activation was confirmed by vendor system monitoring. The source of the activation has not been determined. At this time all aspects of the public notification system are functional. The licensee notified the NRC Resident Inspector and will notify the state and local governments. | ||
| ENS 48805 | 4 March 2013 15:27:00 | 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release | Offsite Notification Due to a Fish Kill | At 0927 CST on March 4, 2012, XCEL Energy Environmental Services made a report to the State of Minnesota regarding 475 fish killed from the discharge canal temperature transient following reactor shutdown on March 2, 2013. Monticello was in the process of performing a planned shutdown in preparation for a refueling outage. The NRC Resident Inspector, Wright County Sheriffs Department and Sherburne County Sheriffs Department have been notified by the licensee. | ||
| ENS 48754 | 14 February 2013 23:10:00 | 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release | Offsite Notification Due to Release of Amertap Balls Into the Mississippi River | On 2/14/2013, Xcel Energy personnel determined that approximately 44% of the Amertap balls recently used were not recovered. Monticello Nuclear Generating Plant is required to report to the Minnesota Pollution Control Agency (MPCA) when greater than 20% of the Amertap balls are not recovered. This is based on an agreement with the MPCA dated September 12, 2008. The MPCA was notified at 1710 CST on 2/14/2013. The licensee has notified the NRC Resident Inspector.
Update for 50.72 non-emergency notification number 48754: The referenced report number was made at 1831 EST on 2/14/2013. This report stated the Minnesota Pollution Control Agency (MPCA) was notified that 44% of Amertap balls recently used were not recovered at 1710 CST on 2/14/2013. Due to a miscommunication between the Monticello Nuclear Generating Plant Chemistry Department and the Xcel Energy Corporate Environmental Services contractor, the actual MPCA notification was not made until 0930 CST on 2/15/2013. This update report is to ensure the correct time of the MPCA notification was documented. The licensee notified the NRC Resident Inspector. Notified R3DO (Pelke). | ||
| ENS 48681 | 18 January 2013 18:40:00 | 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release | Pans System False Activation of 58 Sirens | There was a false activation signal applied for 3 seconds to site emergency sirens. The licensee notified the State of Minnesota and local government agencies. The licensee will notify the NRC Resident Inspector. | ||
| ENS 48503 | 12 November 2012 21:51:00 | 10 CFR 50.72(b)(3)(iv)(A), System Actuation | Reactor Building Isolation with Standby Gas Treatment System Actuation During Radioactive Material Move | At 1551 EST on 11/12/12, the 'A' Refuel Floor Process Radiation Monitor reached 62 mR/hr during movement of the old steam dryer in the plant reactor building. This resulted in the isolation of the drywell containment air monitor and the oxygen analyzer primary containment isolation valves. The signal also resulted in a reactor building isolation (Secondary Containment), start of 'A' Standby Gas Treatment, and transfer of the control room ventilation to the High Radiation Mode. All automatic isolation valves have been reset. Reactor building and control room ventilation have been reset. Standby gas treatment has been secured. There were no challenges to the health and safety of the general public. The NRC Resident Inspector has been notified. | Secondary containment Primary containment Standby Gas Treatment System | |
| ENS 48343 | 25 September 2012 20:00:00 | 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release | Offsite Notification Due to Hydraulic Leak | On September 25, 2012 at 1055 CDT, a road grader developed a hydraulic leak on a steering hose. This resulted in a light mist of approximately 20 gallons of oil being sprayed for a quarter mile. Three hundred feet of that was on gravel and the rest on blacktop. There is no actual or potential impact to the environment. There is no impact to plant operation. At 1500 CDT, (the licensee was) notified by Xcel Energy Environmental Services that the State has been notified. The licensee has notified the NRC Resident Inspector. | ||
| ENS 48341 | 25 September 2012 15:44:00 | 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation 10 CFR 50.72(b)(3)(iv)(A), System Actuation | Automatic Reactor Scram During Maintenance on 4160V Bus 12 Ammeter | During maintenance on 4160V Bus 12 ammeter, a Bus 12 lockout occurred. The station power was from 1R Reserve transformer for work on the 2R Auxiliary transformer. Net effect was Bus 12 locked out, removing power from 12 Reactor Feed Pump and 12 Reactor Recirculation pump. Reactor level lowered to +23 inches then began to rise. With both Main Feed Reg Valves in AUTO, the level transient reached +48 inches, the Reactor Water Level Hi Hi setpoint. The Main Turbine and 11 Reactor Feed Pump tripped as designed, and a Reactor SCRAM occurred. Reactor water level began to drop, and C.4.A Abnormal Procedure for SCRAM was used to restart 11 Reactor Feed Pump and recover water level. Minimum water level reached was -26 inches. Reactor Low Level SCRAM signal and Group 2 Primary Containment isolation occurred at +9 inches as designed, No Safety Relief valves lifted during this transient. High Pressure Coolant Injection (HPCI) and Reactor Core Isolation Cooling (RCIC) did not receive an initiation signal due to not reaching their setpoints. There were no Emergency Core Cooling Systems initiation setpoints reached. Prior to the event, both divisions of Standby Liquid Control were inoperable as part of planned maintenance. All control rods fully inserted. Decay heat is being removed through the turbine bypass to the main condenser. The plant is in a normal shutdown electrical lineup and stable in Mode 3. The licensee has notified the NRC Resident Inspector and will notify the State and local governments. | High Pressure Coolant Injection Reactor Core Isolation Cooling Primary containment Main Turbine Reactor Recirculation Pump Standby Liquid Control Emergency Core Cooling System Safety Relief Valve Main Condenser Control Rod | |
| ENS 47948 | 22 May 2012 22:13:00 | 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release | Offsite Notification Due to Loss of Amertap Balls | On May 22, 2012 it was determined that more than 20% (3 of 8 barrels) of the Amertap balls used for condenser cleaning on May 18, 2012 were not able to be recovered by normal means. Observers were stationed at the discharge structure during the process and it is not believed that balls were released to the river. The current agreement with the Minnesota Pollution Control Agency dated September 12, 2008, requires XCEL Energy to make a report to the MPCA whenever more than 20% (1.5 barrels or approximately 7,500 balls) of the Amertap balls are not recovered. The MPCA was notified May 22, 2012. Approximately, 15,000 Amertap balls have not been recovered by the normal strainer system and may be in the discharge canal. The licensee is investigating the cause of the event. The NRC Resident Inspector, Wright County Sheriffs Department, and Sherburne County Sheriffs Department have been notified. | ||
| ENS 47782 | 28 March 2012 21:48:00 | 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release | Offsite Notification of Potential Release of Amertap Balls to Mississippi | On 3/28/2012, Xcel Energy Personnel determined that approximately 50% of the Amertap balls recently used were not recovered. A survey of the Mississippi River bank downstream of the plant by site personnel recovered an additional 3 Amertap balls, indicating that the balls were not released to the river. Monticello Nuclear Generating Plant (MNGP) is required to report to the Minnesota Pollution Control Agency (MPCA) when greater than 20% (1 .5 barrels or approximately 7,500) of the Amertap balls are not recovered. This is based on an agreement with the MPCA dated September 12, 2008. The MPCA was notified at 1648 CDT on 3/28/12. The NRC Resident Inspector has been notified. | ||
| ENS 47725 | 8 March 2012 15:54:00 | 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release | Notification of the Minnesota Pollution Control Agency for Release of Amertap Balls | At 0954 on 3/8/12 Xcel Energy notified the Minnesota Pollution Control Agency of an Amertap ball release exceeding 1.5 barrels per agreement. Three barrels of Amertap balls are unaccounted for. Plant operational personnel are inspecting the site water system for unaccounted Amertap balls. A survey of the river performed by personnel only produced 4 of the missing balls. The licensee notified the NRC Resident Inspector. | ||
| ENS 47664 | 15 February 2012 14:25:00 | 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release | Offsite Notification Due to Inadvertent Manual Siren Activation | At 0825 CDT on 2/15/2012, the Monticello Nuclear Power Generating Plant (MNGP) received a report from the Sherburne County Sheriff Dispatcher that there had been an inadvertent manual initiation of Emergency Preparedness sirens in the county while performing siren testing. All plant conditions/parameters are normal. A total of 48 emergency sirens were on for approximately one minute before being secured. All sirens are currently functional. Sherburne County and the site NRC Resident Inspector have been notified The licensee also notified the Wright County offices. | ||
| ENS 47464 | 21 November 2011 22:06:00 | 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release | Offsite Notification Due to Fish Kill | At 1606 Central Standard Time, Xcel Energy Environmental Services made a report to the State of MN regarding 190 fish killed from the discharge canal temperature transient during the reactor scram on 11/20/11. The report was made verbally with a follow-up email message detailing the species of fish killed. This is a notification being made under 50.72(b)(2)(xi) as an event related to the environment for which notification to other government agencies have or will be made. The licensee has notified the NRC Resident Inspector and the State and will notify local authorities of this event. | ||
| ENS 47460 | 20 November 2011 05:12:00 | 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(b)(3)(iv)(A), System Actuation | Automatic Reactor Scram While Performing Turbine Bypass Valve Testing | While performing a regularly scheduled Turbine Bypass Valve surveillance, prior to Turbine Bypass Valve movement, a 'B' half scram (signal) was received. Operators immediately suspended testing. Approximately 10 seconds later, a full Reactor Protection System actuation occurred. Following the reactor scram, reactor water level lowered below the Group II isolation initiation setpoint of +9 inches, (resulting in containment valve isolations). There were no radioactive releases associated with this event. No other alarms were received prior to the RPS actuation. The cause of the reactor scram is under investigation at this time. Also, due to the reactor scram, discharge canal temperature rate of change exceeded plant requirements. As a result, the State of Minnesota, and appropriate local agencies will be notified. All control rods inserted and the scram is considered uncomplicated. The plant is in a normal shutdown electrical configuration. The licensee notified the NRC Resident Inspector. | Reactor Protection System Control Rod | |
| ENS 47364 | 21 October 2011 17:50:00 | 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(b)(3)(iv)(A), System Actuation | Automatic Reactor Scram Due to Lockout of Auxiliary Power Transformer | The station experienced a lockout of the 2R Auxiliary Power Transformer. The resulting transient caused an automatic actuation of the RPS system. All control rods fully inserted. A Group 2 Primary Containment isolation occurred. Both 11 and 12 Emergency Diesel Generators started on a loss of voltage signal. Equipment response was that the 11 ESW (Emergency Service Water) pump (cooling for the #11 Emergency Diesel) failed to develop required pressure. The #13-4160V non-safety related bus failed to restore after the transient (and feed the Division 1 Essential Bus). Additionally, the #15 bus transferred to the 1AR transformer (and is feeding the Essential Bus). The #11 Emergency Diesel Generator is currently tagged out of service. Electrical supply is being provided by offsite power. Reactor heat is being removed through the main steam line to the main condenser and reactor water inventory is being provided by the feedwater system. The SRVs lifted and reseated. The HPCI system was manually place into a pressure control mode. The Minnesota Pollution Control Agency is being notified due to the licensee violating the site discharge canal temperature rate of change limit. The licensee notified the NRC Resident Inspector.
Prior to this event the 'B' Control Room Emergency Filtration (CREF) and 'B' Control Room Ventilation (CRV) Systems were inoperable for planned maintenance. On 10-21-11 at 1325 CDT, the #11 EDG ESW Pump was declared inoperable due to low cooling water pump flow, resulting in the #11 EDG being inoperable, which in turn resulted in the 'A' CREF and 'A' CRV being inoperable. Contrary to reporting requirements this condition was not identified and reported pursuant to 10 CFR 50.72(b)(3)(v)(D) as required within 8-hours in the previous event notification. This condition resulted in a loss of safety function for both divisions of CREF and CRV. This update amends the 10-21-11 event notification to include this as an 8-hour non-emergency event pursuant to 10 CFR 50.72(b)(3)(v)(D). The licensee notified the NRC Resident Inspector. Notified the R3DO (Nick Valos) | Feedwater Emergency Diesel Generator Primary containment Main Steam Line Main Condenser Control Rod | |
| ENS 46657 | 5 March 2011 16:45:00 | 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release | Offsite Notification Related to Fish Kill | At 1045 the Monticello Nuclear Generating Plant (MNGP) control room was notified by an Xcel Energy environmental specialist that a fish kill count was conducted on the morning of 3/5/11 following reactor shutdown. In accordance with the MNGP water appropriations permit for fish kill in the Mississippi river, the environmental specialist will be notifying the State of Minnesota Department of Natural Resources and Minnesota Pollution Control Agency. Notifications made to above government agencies meet the reporting criteria established in 10CFR50.72(b)(2)(xi) as an event or situation related to the protection of the environment for which a notification to government agencies has been or will be made. Total fish kill was determined to be approximately 100 fish downstream of the plant's discharge canal. Fish kill was the result of cooldown of water being discharged to the river from the plant's discharge canal. All temperature limits specified in the plant's water appropriation permit were met throughout the shutdown. There was no release of any chemical or radioactive materials to the environment. The licensee has notified the NRC Resident Inspector and will be notifying appropriate state and local authorities. | ||
| ENS 46496 | 20 December 2010 09:57:00 | 10 CFR 50.72(b)(3)(iv)(A), System Actuation | Fuel Pool/Reactor Building Exhaust Plenum Primary Power Supply Failed | At 0357 December 20, 2010 the 'A' division Fuel Pool/Reactor Building Exhaust Plenum Primary Power Supply failed, resulting in upscale readings on both the Fuel Pool and Reactor Building Ventilation Plenum radiation monitors. This condition resulted in closure of the Group II Primary Containment Isolation Valves (PCIV), isolation of Secondary Containment (SCT), initiation of the Standby Gas Treatment System (SBGT), and a transfer of the Control Room Ventilation (CRV) and Control Room Emergency Filtration (CREF) systems to the High Radiation Mode. Conditions and Required Actions were entered for Technical Specification 3.3.6.2 (SCT Instrumentation), 3.3.7.1 (CREF Instrumentation), and 3.4.5 (RCS Leakage Detection - CAM). Radiation levels were verified to be normal in the affected areas. Isolations signals were reset and Secondary Containment ventilation systems were restored to a normal lineup. Repairs are currently in progress to replace the high voltage power supply to the affected radiation monitors and are expected to complete within the required action time limits of the applicable technical specifications. The licensee is in a 24 hour LCO. The licensee has notified the NRC Resident Inspector. | Secondary containment Primary containment Reactor Building Ventilation Standby Gas Treatment System | |
| ENS 46407 | 9 November 2010 17:39:00 | 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release | Offsite Notification - Violation of the Discharge Permit | The Minnesota Pollution Control Agency was notified (on 11/9/10) at 1139 hours (CST) today that at Monticello, the Circulating Water and Service Water Streams were simultaneously chlorinated for a duration of approximately one (1) hour. Simultaneous chlorination of these two water streams is a violation of the National Pollutant Discharge Elimination System (NPDES) Permit. Chapter 4, Section 2.3, states, 'The condenser cooling water and the service water shall not be chlorinated simultaneously.' Upon discovery of this event, both the Service Water and the Circulating Water bleach injection skids were secured. This event did not result in bleach discharge concentration in excess of the 0.038 ppm concentration set forth in the NPDES permit. The licensee notified NRC Resident Inspector. | Service water | |
| ENS 46113 | 21 July 2010 13:16:00 | 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release | Inadvertent Manual Initiation of Emergency Alert Sirens | At 0816 (CDT) on 7/21/2010, the Monticello Nuclear Power Generating Plant (MNGP) received a report from the Sherburne County Sheriff Dispatcher that there had been an inadvertent manual initiation of Emergency Preparedness sirens in the county while performing siren testing. All plant conditions/parameters are normal. A total of 48 emergency sirens were on for approximately 1 minute before being secured. The inadvertent initiation of the sirens was determined to be reportable under 10 CFR 50.72(b)(2)(xi), 'News Release or Notification of Other Government Agency.' Sherburne County, the State of Minnesota, and the site NRC Resident Inspector have been notified. | ||
| ENS 46023 | 17 June 2010 15:45:00 | 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release | Offsite Notification Due to Inadvertent Initiation of Emergency Preparedness Sirens | At 1045 (CDT) on 6/17/2010, the Monticello Nuclear Power Generating Plant (MNGP) received a report from the Sherburne County Sheriff Dispatcher that there had been an inadvertent manual initiation of Emergency Preparedness sirens in the county while performing siren testing in preparation for inclement weather anticipated later this evening. All plant conditions/parameters are normal. A total of 48 emergency sirens were on for approximately 1 minute before being secured. The inadvertent initiation of the sirens was determined to be reportable under 10 CFR 50.72(b)(2)(xi), 'News Release or Notification of Other Government Agency.' Sherburne County, the State of Minnesota, and the site NRC Resident Inspector have been notified. | ||
| ENS 45338 | 10 September 2009 14:13:00 | 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release | State Offsite Notification Due to Not Meeting Permit Requirements | The Minnesota State Pollution Control Agency and State Department of Emergency Management were notified today, September 10, 2009, that Monticello did not meet the National Pollutant Discharge Elimination System (NPDES) Permit. Samples from a new monitoring well near the reactor building showed low levels of tritium greater than normal background but below Environmental Protection Agency drinking water standards. The concentration of tritium is below any radiological reporting levels established in station procedures. No elevated levels have been detected in any of the other permanent plant monitoring wells. Therefore, we have no indications that there has been a release of tritium beyond the site from this source. The station will continue to monitor, sample and investigate the source of the tritium. The licensee notified the NRC Resident Inspector.
A subsequent water sample from a new monitoring well near the reactor building indicated a level of 21,300 picocuries/liter of tritium which is slightly above the Environmental Protection Agency drinking water standard for tritium of 20,000 picocuries/liter. No elevated levels have been detected in any of the other permanent plant monitoring wells. Therefore, (the licensee has) no indication that there has been a release of tritium beyond the site from this source. The station will continue to monitor, sample and investigate the source of the tritium. This poses no immediate safety concern for plant employees or the general public. The licensee notified the NRC Resident Inspector. Notified the R3DO (Ring). | ||
| ENS 44907 | 16 March 2009 14:00:00 | 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release | Offsite Notification Due to Fish Kill During Routine Shutdown | The licensee notified state and local authorities of a fish kill that occurred during a routine plant shutdown for refueling. The fish kill, in the Mississippi River, was monitored for a two day period. Notifications were made to the State of Minnesota Emergency Management Agency, Wright County Sheriff's Office, and Sherburne County Sheriff's Office. The licensee has notified the NRC Resident Inspector. | ||
| ENS 44633 | 6 November 2008 17:15:00 | 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release | Offsite Notification of a Discharge to the Mississippi River | On November 6, 2008 at 11:15, Operations was notified that results of an October 20, 2008 oil and grease weekly sample from a plant sump discharge to the Mississippi River exceeded the National Pollution Discharge Elimination System (NPDES) daily maximum allowable value of 15ppm. The October monthly average oil and grease NPDES of 10ppm was also exceeded. The Minnesota Pollution Control Agency is being notified. The licensee notified the NRC Resident Inspector. | ||
| ENS 44508 | 21 September 2008 02:35:00 | 10 CFR 50.72(b)(3)(iv)(A), System Actuation | Unplanned Loss of Shutdown Cooling Due to Containment Isolation | On Saturday, September 20, 2008, Monticello Nuclear Generating Plant (MNGP) experienced an actuation of the following systems: Reactor Protection System (with the reactor shutdown), Containment Isolation, and Emergency Diesel Generators. The apparent cause of the actuation was a pressure pulse in the reference leg of a Reactor level instrument that resulted when a CRD (Control Rod Drive) pump was started without the reference leg backfill system isolated from the CRD system. This notification is being made in accordance with 10CFR50.72(b)(3)(iv)(A). Due to the containment isolation, shutdown cooling was lost for approximately 90 minutes. Initial reactor temperature was ~95 degrees when the isolation occurred. When shutdown cooling was restored, reactor temperature had increased to ~120 degrees. The Emergency Diesel Generators started but did not load. The diesels have been restored to normal standby status. The licensee has notified the NRC Resident Inspector. | Reactor Protection System Emergency Diesel Generator Shutdown Cooling | |
| ENS 44498 | 17 September 2008 15:17:00 | 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release 10 CFR 50.72(a)(1)(i), Emergency Class Declaration 10 CFR 50.72(b)(3)(iv)(A), System Actuation | Unusual Event Due to Loss of Shutdown Cooling | Monticello lost the 1R offsite power transformer due to an industrial accident that grounded the bus and resulted in a fatality of an employee onsite. At the time of this event, the 2R offsite transformer was already out of service due to a previous event (see EN #44484). This effectively resulted in a loss of all normal offsite power. The 1AR safety related offsite power source remained available and the safety related buses are energized and diesels are available. However, shutdown cooling was lost during the event due to a Group 2 isolation and cannot be restored. The shutdown cooling suction isolation valves #2020 and #2030 have power but until the Group 2 logic can be reset the valves cannot be reopened. The licensee needs to repower the RPS bus to reset the logic. Based on the uncertainty in reestablishing shutdown cooling an Unusual Event was declared based on Emergency Director judgment (EAL HU5.1). Current reactor coolant temperature is approximately 110 degrees with a heatup rate of about 20 degrees an hour. State and local authorities and the NRC resident inspector have been notified. The licensee will likely be making a press release.
On Wednesday, September 17, 2008 Monticello Nuclear Generating Plant (MNGP) experienced a loss of power to the station transformer resulting in a valid actuation of the following systems: Reactor Protection System (with the reactor shutdown), Containment Isolation, and Emergency Diesel Generators. The cause of the loss of power was due to contact of a 115kV transmission line by a manlift. A vendor employee was electrocuted. On-site Medical Emergency Response personnel responded until the individual was transported to North Memorial Medical Center. The individual was pronounced dead at North Memorial Medical Center. Notifications of offsite agencies and a media press release are in progress. 'This notification is being made in accordance 10CFR50.72(b)(2)(xi) and 10CFR50.72(b)(3)(iv)(A).' Licensee notified the NRC Resident Inspector." Notified R3IRC (Garza)
This is a follow-up to Event notification #44498. The station has completed notifications to off-site agencies and to the media. The station continues to troubleshoot and restore plant equipment and respond to media inquiries. NUE update - As of 1113 CDT shutdown cooling was restored." Notified R3 IRC.
Monticello Nuclear Generating Plant exited their Notification of Unusual Event at 1100 CDT on 9/21/08. The exit criteria is supported on the following information: (1) This event did not result in the loss or potential loss of a fission product barrier and did not change the status of the current fuel condition. All three fission barriers are intact and were maintained throughout the event. (2) There were no radiation releases as a result of the event. (3) Restoration of plant loads including shutdown cooling onto a normal offsite power source (the 1R transformer) has been completed. (4) The 1R transformer offsite power source was recovered and is being protected. Protection of the 1R transformer will continue until availability of the other offsite power source supplied from the 2RS/2R transformers has been restored. (5) Shutdown cooling is in service. (6) The site organization challenges in response to the injury event and loss of decay heat removal are no longer present. The licensee has notified the NRC Resident Inspector, as well as state and local agencies. A media release will be issued. Notified R3DO (Stone), NRR EO (Galloway), IRD MOC (Clark), OPA (Burnell), DHS (S. Moore), and FEMA (D. Fuller). | Reactor Protection System Emergency Diesel Generator Shutdown Cooling Decay Heat Removal | 05000263/LER-2008-007 |
| ENS 44484 | 12 September 2008 03:47:00 | 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation 10 CFR 50.72(b)(3)(v)(B), Loss of Safety Function - Remove Residual Heat 10 CFR 50.72(b)(3)(iv)(A), System Actuation | Reactor Scram and Isolation Due to Transformer Lockout | While the 1R transformer was out of service for maintenance, the 2R transformer experienced a lockout resulting in a loss of normal offsite power, a reactor scram, and a Group 1, 2 and 3 isolation. All rods fully inserted as expected. The cause of the 2R transformer lockout is unknown at this time. After initiation, the high pressure coolant injection (HPCI) system would not trip at the high reactor water level set point +48", as required. The operators then manually isolated the HPCI steam lines. Plant decay heat removal is with the reactor core isolation cooling (RCIC) system and the safety relief valves. Torus cooling is in service. The vital electrical busses are being supplied by the 1AR transformer. Efforts are underway to restore the 1R transformer to service, and subsequently the non-vital busses. The licensee notified the NRC Resident Inspector.
The HPCI system was declared inoperable and isolated due to failure to automatically trip at +48" Reactor Water Level. The HPCI steam supply valves were automatically closed to remove HPCI from service. In addition, the HPCI turbine trip failed to trip with the turbine trip push button. The cause of the trip failure is unknown at this time. The licensee is continuing to investigate. HPCI did automatically start as designed and injected to the reactor vessel as designed. However, HPCI failed to trip at High Reactor Water Level as required. Additionally, the Automatic Depressurization System (ADS) timer showed erratic indication following the event. The ADS timer was inhibited to prevent automatic action. ADS is inoperable, but manual steam relief valve operation remains available. The licensee will notify the NRC Resident Inspector. Notified R3DO (Passehl), NRR EO (Ross-Lee), and IRD (McMurtray).
A (second) Group 2 isolation signal was received when reactor water level lowered below +9 (inches) (while pumping drywell sumps). All Group 2 valves except the drywell sump isolation valves were closed due to a previously reported Group 2 signal. The drywell sump valves had been opened to allow manual pumpdown of the sumps. The sump valves closed as expected. Licensee notified the NRC Resident Inspector. Notified R3DO (Passehl). | High Pressure Coolant Injection Reactor Core Isolation Cooling Automatic Depressurization System Decay Heat Removal Safety Relief Valve | 05000263/LER-2008-007 |
| ENS 43246 | 18 March 2007 04:46:00 | 10 CFR 50.72(b)(3)(iv)(A), System Actuation | Rps Trip Signal and Containment Isolations Received During Maintenance | With the plant in refueling outage with all rods in and in Mode 5, a RPS trip and a containment isolation was received at 2347, 03/17/07. This event occurred when Div #2 Bus 16 Bus Pot Drawer was opened during isolation of 1AR Transformer Metering under C/O-17605. The opening of this Pot Drawer caused Div #2 4KV Bus 16, Div #2 480V LC-104 and Div #2 480V MCC-141, 142, 143, and 144 to open. 'B' RPS tripped causing full RPS trip due to SRM shorting removed. The loss of power caused RBV (Reactor Building Ventilation) and Spent Fuel Pool Radiation Monitors to trip and cause containment isolation to occur. Investigation into C/O-17605, restoration of power, resetting of RPS and containment isolation in progress. The containment valves that received an isolation signal were: Primary Containment Atmosphere Control, Post Accident H2/O2 Control system, Post Accident Sampling system, O2 analyzing and SCTMT isolation (H&V). The licensee notified the NRC Resident Inspector. | Primary containment | |
| ENS 43174 | 20 February 2007 14:30:00 | 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release | Offsite State Notification Required by Npdes Permit | Notification to NRC following notification to the following government agencies on 02/20/2007 at 0830 (CST): State of Minnesota Pollution Control Agency - Water Control Quality, State of Minnesota Department of Emergency Management - State Duty Officer. Notifications made to above government agencies in accordance with Monticello NPDES permit for a collapse of cooling tower panels which resulted in a diversion of circulating flow overland to the discharge canal, resulting in washing of soil and gravel into the canal. The licensee informed the NRC Resident Inspector. | ||
| ENS 43114 | 23 January 2007 19:00:00 | 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release | Press Release Issued | The purpose of this notification is to inform the NRC that Nuclear Management Company (NMC) will be issuing a press release approximately two hours (CST) after this notification to the NRC on January 23, 2007, concerning an event previously reported to the NRC on January 10, 2007, via EN# 43088. The event in question involved an automatic reactor scram at 3:26 PM on January 10, 2007. As reported in that notification, all safety systems operated correctly. The scram occurred following the unexpected opening of the main turbine control valves. There was no release of radioactivity during the event. The purpose of the press release is to provide information to the media and the public regarding the results of NMC's investigation as to the cause of the January 10 event and the status of remedial actions. The licensee notified the NRC Resident Inspector. The licensee will notify State and Local authorities. |