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 Entered dateSiteRegionReactor typeEvent description
ENS 5411111 June 2019 17:55:00MonticelloNRC Region 3At 1132 CDT on 6/11/2019, both manual primary containment isolation valves in a one-inch service air line were found open. This resulted in an open primary containment penetration. Both valves are required to be closed for Primary Containment Isolation Valve Operability. Both valves were closed and independently verified closed at 1149 CDT on 6/11/2019. This is being reported under 10 CFR 50.72(b)(3)(v)(C) and (D), and 10 CFR 50.72(b)(3)(ii)(B). There was no impact to the health and safety of the public or plant personnel. The NRC Resident Inspector has been notified. The licensee also notified the State of Minnesota State Duty Officer.
ENS 5400015 April 2019 11:36:00MonticelloNRC Region 3At 0511 CDT on 4/15/2019, transport of a potentially radiologically contaminated person from the Monticello Nuclear Plant to a local hospital was performed prior to conducting a radiological survey as a prudent measure to ensure timely medical support. At 0658 CDT a radiological survey determined that the individual and their clothing were not contaminated. This is reportable under 10 CFR 50.72(b)(3)(xii). The NRC Resident Inspector has been notified."
ENS 5399713 April 2019 02:04:00MonticelloNRC Region 3

EN Revision Text: HIGH ENERGY LINE BREAK DOOR FOUND IN INCORRECT POSITION RESULTING IN LPCI AND CORE SPRAY BEING INOPERABLE At approximately 1815 CDT on April 12, 2019, High Energy Line Break (HELB) Door-410A in the Reactor Building was discovered in the closed position. HELB Door-410B was previously closed for maintenance. Either Door-410A or Door-410B must be open to support the current HELB analyses. With both doors closed, this is considered an unanalyzed condition resulting in the loss of a post-HELB safe shutdown path. With Door-410A and Door-410B closed, LPCI (Low Pressure Coolant Injection) and Core Spray injection valves in both divisions are no longer considered available. This condition is being reported under 10 CFR 50.72(b)(3)(ii) as an unanalyzed condition that significantly degrades plant safety and 10 CFR 50.72(b)(3)(v) as an event or condition that could have prevented the fulfillment of a safety function. The condition was resolved at approximately 1845 CDT on April 12, 2019 when Door-410A was blocked open. The health and safety of the public was not affected by this condition. The NRC Resident has been notified.

  • * * RETRACTION FROM JESSE TYGUM TO HOWIE CROUCH AT 1330 EDT ON 5/24/19 * * *

Event Notification (EN) #53997, made on 4/13/2019, is being retracted. An engineering evaluation completed subsequent to this event analyzed the discovered condition with both Door-410A and Door-410B being closed. The engineering evaluation determined that the environmental conditions present with both Door-410A and Door-410B closed would not have impacted the availability of both divisions of the LPCI (Low Pressure Coolant Injection) and Core Spray injection valves nor would it have resulted in the loss of a post-HELB safe shutdown path. Therefore, this condition did not meet the criteria for an 8-hour notification per 10 CFR 50.72(b)(3)(ii) as an unanalyzed condition that significantly degrades plant safety or per 10 CFR 50.72(b)(3)(v)(D) as an event or condition that could have prevented the fulfillment of a safety function. The NRC Resident Inspector has been notified. The licensee also notified the Minnesota State Duty Officer. Notified R3DO (Cameron).

ENS 5359711 September 2018 18:42:00MonticelloNRC Region 3On 9/10/2018, the 11 Core Spray (CSP) loop was placed in service to support quarterly surveillance testing. With the 11 CSP pump in service it was identified that the check valves isolating the 11 CSP system from the keep fill supply were leaking by. At 1129 CDT on 9/11/2018, it was identified that this leakage may have exceeded the leakage rate assumptions made in the dose analysis calculation for emergency core cooling system (ECCS) leakage outside containment following a loss of coolant accident (LOCA). Therefore, this is being reported in accordance with 10 CFR 50.72(b)(3)(ii)(B) for an unanalyzed condition that significantly degrades plant safety and 10 CFR 50.72(b)(3)(v) for any event or condition that at the time of discovery could have prevented the fulfillment of the safety function of structures or systems that are needed to: (C) Control the release of radioactive material; or (D) Mitigate the consequences of an accident. The potential ECCS leak pathway has been isolated. There is no impact to health and safety of the public. The NRC Resident Inspector has been notified."
ENS 5328523 March 2018 21:07:00MonticelloNRC Region 3GE-3This report is made for a loss of Emergency Assessment Capability associated with Emergency Action Levels for Toxic and Flammable Gas and is reportable under 10 CFR 50.72(b)(3)(xiii). During an emergency equipment inventory, it was identified that methods were not available to detect levels of toxic or flammable gas at the IDLH (Immediately Dangerous to Life and Health) level for a number of substances due to the detector having an unsuitable range. The IDLH is used to assess the Emergency Action Level Alert Range. The ability of the Control Room Staff to detect and respond to the presence of toxic or flammable gas is unaffected. Because there have been no chemical spills or releases that would require sampling to be performed, the health and safety of the public was not affected. The resident NRC Inspector has been notified. The licensee will be notifying the state of Minnesota.
ENS 5281420 June 2017 08:18:00MonticelloNRC Region 3GE-3At 2353 CDT on 6/19/2017, while performing the High Pressure Coolant Injection (HPCI) quarterly surveillance following planned maintenance, the HPCI turbine did not start as expected due to the HPCI turbine stop valve failing to open. This issue is being reported under 10 CFR 50.72(b)(3)(v)(D) as a condition that could have prevented the fulfillment of a safety function at the time of discovery. Investigation into the failure of the HPCI system to start is in progress. The unit remains at 100% power. The health and safety of the public was not affected. The NRC Resident Inspector has been notified.
ENS 527811 June 2017 23:41:00MonticelloNRC Region 3GE-3Planned maintenance to restore normal power to Plant Computer Systems resulted in an unexpected loss of all Meteorological (MET) Tower Data (at 1645 CDT). As a result, this represents a Loss of Emergency Assessment Capability and is reportable under 10CFR 50.72 (b)(3)(xiii). The isolation was restored and MET Tower Data was restored at 1845. The health and safety of the public was not affected as the plant is operating in a normal condition with no severe weather or storms in the area. Additionally meteorological data was available from the National Weather Service should this data had been necessary. The NRC Resident Inspector has been notified." The licensee will be notifying the State of Minnesota.
ENS 5274911 May 2017 18:11:00MonticelloNRC Region 3GE-3A can of alcohol (16.9 ounce foreign beer) was discovered unopened in an administration building refrigerator. Site security took possession of the can of alcohol. The owner of the can of alcohol is unknown. This licensee is making this 24 hour notification in accordance with 10CFR26.719(b)(1). The licensee notified the NRC Resident Inspector.
ENS 5271528 April 2017 21:21:00MonticelloNRC Region 3GE-3This 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 5268215 April 2017 13:03:00MonticelloNRC Region 3GE-3During 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.
ENS 5245421 December 2016 18:00:00MonticelloNRC Region 3GE-3

At 0935 (CST) on 12/21/2016, while performing the High Pressure Coolant Injection (HPCI) Comprehensive Pump and Valve Tests for post-maintenance testing following scheduled maintenance, the HPCI turbine did not start as expected due to the HPCI turbine stop valve failing to open. This issue is being reported under 10CFR50.72(b)(3)(v)(D) as a condition that could have prevented the fulfillment of a safety function at the time of discovery. Investigation into the failure of the HPCI system to start is in progress. The plant remains at 100% power with no challenges to the health and safety of the public. The NRC Resident Inspector has been notified. The plant is in a 14-day action statement under LCO 3.5.1, 'ECCS - Operating' due to the HPCI turbine stop valve failure. The licensee notified the Minnesota State Duty Officer.

  • * * RETRACTION FROM KIM HOFFMAN TO JOHN SHOEMAKER AT 1303 EST ON 1/17/18/17 * * *

On December 21, 2016, the NRC Operations Center was notified of Event Number 52454 that described a failure of the High Pressure Coolant Injection (HPCI) turbine stop valve to open during post maintenance testing prior to being declared operable. The condition was reported in accordance with 10 CFR 50.72 (b)(3)(v)(D) as a condition that could have prevented the fulfillment of a safety function at the time of discovery. At the time, it was not readily apparent that the failure was due to the maintenance activities. Subsequent return-to-service testing showed the oil system vent and fill had been inadequate following the maintenance. This event occurred as a result of the maintenance process and would not have occurred during normal operation of the system. NUREG-1022, Revision 3 states, 'reports are not required when systems are declared inoperable as part of a planned evolution for maintenance or surveillance testing when done in accordance with an approved procedure and the plant's TS (unless a condition is discovered that would have resulted in the system being declared inoperable).' There was no discovered condition that would have resulted in the safety function of the system being declared inoperable under normal, non-maintenance conditions. Based on the above additional information, Monticello Nuclear Generating Plant is retracting this report. The plant was in a planned evolution and did not discover a condition that could have prevented performing a safety function. The licensee has notified the NRC Resident Inspector. Notified R3DO (McCraw).

ENS 5245121 December 2016 16:38:00MonticelloNRC Region 3GE-3This 60-day telephone notification is being submitted in accordance with 10 CFR 50.73(a)(1) and 10 CFR 50.73(a)(2)(iv)(A) to report an invalid actuation of the 12 Emergency Diesel Generator Emergency Service Water pump (12 ESW pump). At 1745 (CST) on October 24, 2016, an unexpected auto-start of the 12 ESW pump occurred. The 12 Emergency Diesel Generator (12 EDG), was previously properly removed from service and isolated for scheduled maintenance. Upon investigation, is was determined that no valid start signal was present and actuation occurred during relay replacement activities on the 12 EDG in C-92 (12 EDG (G-38) electrical control panel) cabinet when electricians inadvertently bumped a 12 EDG start relay. During this period, the Control Room received annunciators indicating the 12 EDG engine was running/cranking and the 12 ESW pump started. Due to being isolated, the 12 EDG did not actually start. The licensee notified the NRC Resident Inspector.
ENS 5239627 November 2016 21:22:00MonticelloNRC Region 3GE-3At 1447 (CST) on 11/27/2016 while troubleshooting a minor leak on the High Pressure Coolant Injection (HPCI) turbine, it was discovered that the HPCI turbine exhaust drain pot high level bypass switch was not functioning per design to support removal of condensate from the HPCI turbine casing. This resulted in some water accumulation within the HPCI turbine casing. Subsequently, HPCI was declared INOPERABLE and this issue is being reported under 10CFR50.72(b)(3)(v)(D) as a condition that could have prevented the fulfillment of a safety function at the time of discovery. The plant remains at 100 percent power with no challenges to the health and safety of the public. The NRC Resident Inspector has been notified. Technical Specification limiting condition for operation requires HPCI to be Operable within 14 days. The licensee will be notifying the State of Minnesota regarding the event.
ENS 521565 August 2016 13:58:00MonticelloNRC Region 3GE-3On 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 521545 August 2016 06:26:00MonticelloNRC Region 3GE-3At 2240 CDT on August 4, 2016, it was discovered that the floor between the cable spreading room and the plant administration building (PAB) basement is not a credited Appendix R fire barrier. Because the cable spreading room and the plant administration building are located in the same fire area, a fire in the PAB could spread to the cable spreading room requiring evacuation of the control room. The travel path used to access the Alternate Shutdown Panel following control room evacuation traverses the same fire area in the PAB. Therefore, this event is being reported under 10 CFR 50.72(b)(3)(ii) for Degraded or Unanalyzed Condition as a fire in the PAB could have the potential to impact Division 1 equipment as well as impede the Operators ability to access Division 2 safe shutdown equipment. Fire watches have been established. There is no impact to the health and safety of the public. The NRC Resident Inspector has been notified. The licensee will notify the State of Minnesota.
ENS 521534 August 2016 22:04:00MonticelloNRC Region 3GE-3

At 1415 CDT on August 4, 2016, while performing a scheduled fire protection surveillance, it was discovered that a component within fire panel FZCP-7, BATTERY ROOM FIRE DETECTION had failed resulting in the inability of the installed fire detectors to detect a fire within the Division 1 and Division 2, 125 VDC battery rooms as well as the Division 2, 250 VDC battery room. This is being reported under 10 CFR 50.72(b)(3)(xiii) for a Loss Of Emergency Assessment Capability as the Control Room would not receive automatic notification of a fire in these areas for evaluation of HU2.1 and HA2.1 for fire within impacted battery rooms which are located within the Protected Area. There is no impact to the health and safety of the public. A 15 minute fire watch has been established for the affected fire zones. The NRC Resident Inspector has been notified.

  • * * UPDATE FROM MARTIN RAJKOWSKI TO DANIEL MILLS AT 1050 EDT ON 08/05/2016 * * *

Event Notification 52153 completed at 2204 EDT on 8/4/2016 shown above contains an error. The failure of FZCP-7, BATTERY ROOM FIRE DETECTION, resulted in the inability to detect a fire within the Division 1 and Division 2 125 VDC battery rooms as well as the Division 1 250 VDC battery room. The Division 2 250 VDC battery room was not affected by this issue. Additionally, the State of Minnesota was notified of this issue. The NRC Resident Inspector has been notified of this update. Notified R3DO (Skokowski)

ENS 5202018 June 2016 06:25:00MonticelloNRC Region 3GE-3On 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 5181222 March 2016 06:38:00MonticelloNRC Region 3GE-3On 3/22/2016 during performance of HPCI FLOW CONTROL SYSTEM DYNAMIC TEST PROCEDURE, an oil leak was discovered on the hydraulic control oil piping. HPCI had previously been declared INOPERABLE due to planned maintenance, however as a result of the oil leak HPCI remains INOPERABLE. This oil leak would have cause HPCI to be declared INOPERABLE had it been found outside of the planned maintenance. The plant remains at 100% power with no challenges to the health and safety of the public. HPCI is in a 14 day technical specification to repair the oil leak. The licensee notified the NRC Resident Inspector.
ENS 5156624 November 2015 17:02:00MonticelloNRC Region 3GE-3At 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 5156424 November 2015 14:19:00MonticelloNRC Region 3GE-3On 11/24/2015 at 0534 hours (CST) the plant was in MODE 3 (hot standby) for a forced outage. While initially placing Shutdown Cooling (SDC) in service, the 12 Residual Heat Removal (RHR) pump tripped approximately 8-10 seconds after start due to the closure of the RHR SDC suction isolation valves. This was determined to be from an invalid signal on the Reactor Pressure Vessel (RPV) suction interlock. This is being reported under 10 CFR 50.72 (b)(3)(v)(B) as an event or condition that could have prevented the fulfillment of the safety function of structures or systems that are needed to remove residual heat. This event did not challenge the ability to maintain safe shutdown conditions, remove residual heat, control the release of radioactive material, or mitigate the consequences of an accident as other methods of decay heat removal were being utilized successfully to establish plant conditions. The NRC Resident Inspector has been notified. This incident places the RHR system in a 24-hour technical specification limiting condition for operations.
ENS 5156023 November 2015 15:03:00MonticelloNRC Region 3GE-3At 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.
ENS 513798 September 2015 18:15:00MonticelloNRC Region 3GE-3A non-licensed employee supervisor had a confirmed positive for alcohol during a random fitness-for-duty test. The employee's access to the site has been terminated. The licensee notified the NRC Resident Inspector.
ENS 5130610 August 2015 19:49:00MonticelloNRC Region 3GE-3On 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 5124120 July 2015 13:37:00MonticelloNRC Region 3GE-3On 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 510342 May 2015 20:57:00MonticelloNRC Region 3GE-3On 5/2/2015 at 1247 CDT, while the plant was in MODE 5 for a refueling outage with the vessel cavity flooded, during logic testing of the non-credited essential 4kV bus, MNGP (Monticello Nuclear Generating Plant) experienced a human performance error that caused a loss of the 4kV bus and essential load center. Loss of the load center de-energized valve position indication on one shutdown cooling isolation valve. This tripped the shutdown cooling pump on a pump suction interlock, resulting in the loss of shutdown cooling. This is being reported under 10 CFR 50.72(b)(3)(v)(B) as an event or condition that could have prevented the fulfillment of the safety function of structures or systems that are needed to remove residual heat. Following the event, the safety related load centers were cross- This event did not result in the release of any radioactive material and did not challenge the health and safety of the public. The NRC Resident Inspector has been notified.
ENS 5097812 April 2015 16:01:00MonticelloNRC Region 3GE-3On 4/12/2015 at approximately 1230 CDT, an Xcel Energy employee performing activities in the drywell (currently shut down for a planned refueling outage), experienced heat exhaustion. Upon discovery, the plant emergency medical team was dispatched to aid the individual. The individual was immediately transported, via ambulance, to a local hospital for treatment without verification that no contamination existed. Accompanying the individual were two (2) radiation protection individuals. The individual was transported out of the Protected Area at approximately 1250 CDT. Because the potentially contaminated individual could not be surveyed prior to being transported offsite, the individual was considered potentially contaminated. As such, this event is being reported as an 8-hour prompt report pursuant to 10 CFR 50.72(b)(3)(xii). On 4/12/2015 at approximately 1340 CDT, the radiation protection personnel that accompanied the individual to the medical facility reported that the individual, ambulance, gurney, hospital travel path and exam room were determined not to be contaminated. As a result, no follow-up status report is planned. The licensee notified the NRC Resident Inspector. The licensee will be notifying the State Duty Officer.
ENS 5091521 March 2015 13:55:00MonticelloNRC Region 3GE-3

At 0537 CDT on March 21, 2015, following the High Pressure Coolant Injection (HPCI) system quarterly pump and valve surveillance, after HPCI was removed from service, an alarm for the HPCI Turbine Inlet High Drain Pot Level did not reset. This indicated that LS-23-90 (HPCI Steam Supply Drain High Level Bypass) did not reset, which could be an indication that condensate exists in the steam line. The system responded as designed but the alarm did not clear as expected. Without assurance that the condensate has been removed from the HPCI steam line, HPCI remains inoperable for reasons other than the planned surveillance. As a result, this condition is being reported under 10 CFR 50.72(b)(3)(v)(D) as a condition that could have prevented fulfillment of the safety function at the time of discovery. The health and safety of the public was maintained as the plant was in a normal condition with no initiating event in progress. The NRC Resident Inspector has been notified. The State of Minnesota will be notified.

  • * * RETRACTION FROM RANDY SAND TO DANIEL MILLS AT 1445 EDT ON 5/11/15 * * *

On March 21, 2015, Northern States Power Minnesota reported a condition that could have prevented the fulfillment of a safety function under 10 CFR 50.72(b)(3)(v)(D). The High Pressure Coolant Injection (HPCI) System was declared inoperable for a reason other than planned maintenance due to the failure of the HPCI Steam Supply Drain Hi Level Bypass Level Switch to clear the high level alarm subsequent to actuation. An engineering evaluation was performed and concluded that the function of the primary pathway to remove condensate remained unchallenged by the condition present on the level switch This conclusion was also validated via thermography with the HPCI steam supply pressurized and bypass valve open. The verification that the primary pathway was functional provides reasonable assurance that the HPCI steam supply was always clear of condensate supporting the ability of HPCI to perform its required safety function. Therefore, the condition present on the level switch did not render HPCI inoperable. The conclusions of the engineering evaluation provide the basis for retraction of the ENS report made on March 21. The NRC Resident Inspector has been notified. The licensee will also notify the State of Minnesota. Notified R3DO (Peterson).

ENS 5089917 March 2015 02:57:00MonticelloNRC Region 3GE-3

At 1820 on March 16th, 2015, the High Pressure Coolant Injection (HPCI) system steam lines were re-pressurized following scheduled maintenance. Upon restoration, an alarm was received that indicated condensate may exist in the steam line. The system responded as designed but the alarm did not clear as expected. Without assurance that the condensate has been removed from the HPCI steam line, HPCI remains inoperable for reasons other than the planned maintenance. As a result, this condition is being reported under 10CFR50.72(b)(3)(v)(D) as a condition that could have prevented fulfillment of the safety function at the time of discovery. The health and safety of the public was maintained as the plant was in a normal condition with no initiating event in progress. The NRC Resident Inspector has been notified. The licensee will also notify the State of Minnesota.

  • * * RETRACTION FROM RANDY SAND TO DANIEL MILLS AT 1445 EDT ON 5/11/15 * * *

On March 16, 2015, Northern States Power Minnesota reported a condition that could have prevented the fulfillment of a safety function under 10 CFR 50.72(b)(3)(v)(D). The High Pressure Coolant Injection (HPCI) System was declared inoperable for a reason other than planned maintenance due to the failure of the HPCI Steam Supply Drain Hi Level Bypass Level Switch to clear the high level alarm subsequent to actuation. An engineering evaluation was performed and concluded that the function of the primary pathway to remove condensate remained unchallenged by the condition present on the level switch. This conclusion was also validated via thermography with the HPCI steam supply pressurized and bypass valve open. The verification that the primary pathway was functional provides reasonable assurance that the HPCI steam supply was always clear of condensate supporting the ability of HPCI to perform its required safety function. Therefore, the condition present on the level switch did not render HPCI inoperable. The conclusions of the engineering evaluation provide the basis for retraction of the ENS report made on March 17. The NRC Resident Inspector has been notified. The licensee will also notify the State of Minnesota. Notified R3DO (Peterson).

ENS 5080610 February 2015 20:39:00MonticelloNRC Region 3GE-3

On February 10, 2015, at 1240 EST, Northern States Power-Minnesota (NSPM) determined that the Station Blackout (SBO) implementation at Monticello Nuclear Generating Plant (MNGP) was not consistent with the NRC Safety Evaluation (SE). Specifically, the High Pressure Coolant Injection (HPCI) system was not being utilized in a manner consistent with the NRC SE for SBO. Current battery calculations do not reflect a full complement of HPCI system equipment running for the duration (coping requirements) of the SBO event. The calculation assumed a manual action to remove the HPCI auxiliary oil pump from operating during an SBO event in order to preserve the station battery. NSPM is reporting this as an Unanalyzed Condition pursuant to the requirements of 10 CFR 50.72(b)(3)(ii)(B). The health and safety of the public was not affected since no SBO event occurred. All station batteries and the HPCI system remain operable in accordance with the plant Technical Specifications. The NRC Resident Inspector was notified of the event.

  • * * RETRACTION PROVIDED BY MICHAEL BURTON TO JEFF ROTTON AT 1254 EDT ON 04/03/2015 * * *

An engineering analysis was performed updating the battery calculations for Station Blackout (SBO) implementation demonstrating the ability of the safety related station batteries to provide sufficient capacity and capability to ensure that the core is cooled and appropriate containment integrity is maintained in the event of the SBO for the specified four hours. Therefore, the battery calculation is analyzed and specifically the High Pressure Cooling Injection (HPCI) System is analyzed to run in automatic for the entire duration of the SBO event meeting the site licensing basis for SBO. The SBO procedure has been revised to incorporate HPCI running in automatic for the entire duration of the SBO event. The NRC Resident Inspector has been notified. Notified R3DO (Duncan)

ENS 5070529 December 2014 03:40:00MonticelloNRC Region 3GE-3While the 12 Emergency Diesel Generator (EDG) was inoperable for performance of the monthly surveillance, adjustments were inadvertently made to 11 EDG which made it inoperable. As a result, Technical Specification (TS) 3.8.1 Condition E, for both EDG's inoperable was entered. Monticello has subsequently restored 12 EDG to an operable status within the 2 hour TS LCO (Limiting Condition for Operation) completion timer requirement. The station remained in a safe condition during this discovery with 12 EDG available at all times. The plant continues to operate in a normal condition with no initiating events present. The health and safety of the public was not impacted as a result of this condition. The NRC Resident Inspector has been notified. EDG 12 was restored to operable status at 2214 CST and EDG 11 will remain inoperable until a surveillance test is performed to start the EDG and restore the local governor control idle speed to the correct setting. The licensee will be notifying the Minnesota State Duty Officer.
ENS 5066310 December 2014 00:31:00MonticelloNRC Region 3GE-3

At 1830 (CST) on December 9, 2014 Door 410B, a HELB (High Energy Line Break) door between the east and west sides of the ground floor of the reactor building, was found closed. This door is one half of a pair of double doors that are normally open to provide a HELB energy and flooding release path to mitigate postulated HELB events. The closed HELB door has the potential to impact safe shutdown by exposing both divisions of safe shutdown components to unanalyzed environmental conditions. With the potential loss of both divisions of safe shutdown equipment, no safe shutdown path would exist. This condition is being reported as an unanalyzed condition as defined by (10 CFR) 50.72(b)(3)(ii)(B). The HELB door was immediately opened and returned to normal configuration. Door 410A remained open during the time that Door 410B was closed and provided an available, but not yet analyzed, release path that could have mitigated the consequences of this event. The health and safety of the general public was not impacted as a result of this condition. The NRC Resident Inspector has been notified.

  • * * RETRACTION FROM JON LAUDENBACH TO CHARLES TEAL ON 1/30/15 AT 1513 EST * * *

Further analysis has determined that the condition did not significantly degrade plant safety. Door 410B in the Reactor Building was found closed. This door is one half of a pair of double door (Doors 410A and 410B) that normally open to provide a High Energy Line Break (HELB) energy and flooding release path to mitigate postulated HELB events. The condition of one half of the double door closed was not previously analyzed. A subsequent completed engineering evaluation analyzed this condition, Door 410B being closed and Door 410A being open, for the following environmental conditions: peak compartment temperatures, block wall differential pressure, radiation dose, and flooding. The environmental conditions found the Reactor Building in response to Door 410B being closed with 410A being open does not affect the operability of safety related equipment housed within the Reactor Building or the ability to safely shut-down the plant and maintain the plant shutdown condition following a HELB event. The NRC Resident Inspector has been notified. Notified R3DO (Dickson).

ENS 5049626 September 2014 02:53:00MonticelloNRC Region 3GE-3

At 2200 CDT on September 25, 2014, the Duty Shift Manager was notified that Agastat relays associated with Primary Containment Isolation valves on the Hydrogen-Oxygen Analyzing System are beyond the analyzed shelf life for relays that are in the normally energized state and are considered INOPERABLE. This affected both primary containment isolation valves for a containment penetration on multiple flow paths. This issue was determined to be reportable under (10 CFR) 50.72 (b)(3)(v)(C) & (D) for an event or condition that at the time of discovery could have prevented the fulfillment of the safety function of structures or systems that are needed to control the release of radioactive material and mitigate the consequences of an accident. Additionally, the required actions involved isolating six flow paths via manual isolation valves. This action rendered the Hydrogen-Oxygen Analyzers non-functional for both trains and constitutes a loss of Emergency Preparedness and Accident Assessment Capability. This is reportable under (10 CFR) 50. 72(b)(3)(xiii). The Primary Containment Isolation Valves have been, and remain, in their closed position to satisfy their Primary Containment Function and protect the health and safety of the public. The NRC Senior Resident Inspector has been notified. The licensee will notify the State of Minnesota. The relays of concern were manufactured 19 years ago and have been in operation for 11 years, versus a manufacturer assumption of a 10 year operational lifespan.

  • * * UPDATE FROM SCOTT CHRISTOS TO DONALD NORWOOD AT 1430 EST ON 11/20/2014 * * *

Partial retraction for EN 50496. This is an update of Emergency Notification System (ENS) report 50496 that was submitted at 0253 EDT on Friday, September 26, 2014. ENS notification was made due to four relays associated with the sampling valves on the Hydrogen-Oxygen Analyzing (HOA) system that perform Primary Containment Isolation Valve (PCIV) functions. These relays were discovered installed beyond their manufacturer qualified service life, which called operability into question. The portions 10 CFR 50.72 (b)(3)(v)(C) & (D) are being retracted after subsequent bench testing and investigation of system operability. Based on the past operability evaluation, all four relays associated with PCIV functions on the HOA system would have performed their specific safety function of primary containment isolation, as required by the facility's technical specifications. Therefore, this event does not meet the threshold of an event or condition that would prevent fulfilment of a safety function. The loss of emergency preparedness and accident assessment capability previously reported under 10 CFR 50.72 (b)(3)(xiii) remains unchanged. The NRC Resident Inspector has been notified. Notified R3DO (Peterson).

ENS 5045614 September 2014 11:03:00MonticelloNRC Region 3GE-3

At 0226 CDT on September 14, 2014, MNGP (Monticello Nuclear Generating Station) experienced a trip of the 12 Reactor Recirc Pump. The subsequent power drop and lowering of recirculating water flow resulted in the plant being outside of the analyzed region of the Power to Flow Map. Operators promptly restored operation within the analyzed region per procedural guidance. This event has been determined to be a condition where the plant was in an unanalyzed condition that significantly degrades plant safety and is reportable under 50.72(b)(3)(ii). The plant is in stable condition at 51% power and the health and safety of the public were not affected. The investigation of the cause of this event is in progress. The licensee will notify the NRC Resident Inspector.

  • * * RETRACTION FROM SCOTT CHRISTOS TO HOWIE CROUCH AT 1433 EST ON 11/10/14 * * *

Further analysis has determined that the condition did not significantly degrade plant safety. General Electric Hitachi was requested to review the event and confirm the SIL653 guidance remains applicable for MELLLA+ (Maximum Extended Load Line Limit Analysis) operation. This review was completed and the conclusions of SIL653 remain valid . The SIL states that: 'unplanned events that result in the plant exceeding the licensed upper boundary do not constitute a safety concern. The consequences of such unplanned events are bounded by the GE safety analysis of limiting events initiated from within the licensed operating domain. Stability monitoring and protection using Detection and Suppression Solution Confirmation Density remained available throughout the event (oscillating power range monitors). The NRC Resident Inspector has been notified. Notified R3DO (Hills).

ENS 5041128 August 2014 10:09:00MonticelloNRC Region 3GE-3'Planned preventive maintenance will render both divisions of discharge canal radiation monitors non-functional. As a result, this represents a loss of emergency assessment capability and is reportable under 10 CFR 50.72(b)(3)(xiii). The planned maintenance is expected to last two hours. During this time, alternate plant parameters will be monitored and sampling performed if needed. The health and safety of the public remains protected as the plant is operating in a normal condition. The NRC Resident Inspector was notified prior to removing the discharge canal radiation monitors from service.
ENS 5036414 August 2014 08:58:00MonticelloNRC Region 3GE-3The service water radiation monitor system will be rendered nonfunctional during planned preventive maintenance. As a result, this represents a loss of emergency assessment capability and is reportable per 10CFR50.72(b)(3)(xiii). The planned maintenance is expected to last 4 hours. During this time, plant parameters will be monitored and sampling will be performed which will support sustaining the health and safety of the public during this planned maintenance activity. The NRC Resident Inspector will be notified prior to removing the service water radiation monitor from service.
ENS 503455 August 2014 20:53:00MonticelloNRC Region 3GE-3The Division 1 Control Room Emergency Filtration System (CREF) was inoperable for scheduled replacement of charcoal. During the scheduled maintenance, Division 2 CREF was placed into service. Approximately 5 minutes after startup (1446 CDT on 8/5/2014), the Division 2 CREF recirculation fan tripped off for unknown reasons. This rendered both trains of CREF inoperable. This required entry into Technical Specification TS 3.0.3. This is being reported pursuant to 10 CFR 50.72(b)(3)(v)(D) as an event or condition that could have prevented the fulfillment of the safety function of structures or systems that are needed to (D) Mitigate the consequences of an accident. At 1707 CDT on 8/5/2014, the Division 1 CREF train maintenance was completed and the Division 1 CREF was declared operable. TS 3.0.3 was exited at this time. Investigation is in progress to determine the cause of the Division 2 CREF trip. The control room boundary was not challenged during this time period with any change in radiation levels as plant operation was unaffected. Thus, the health and safety of the public was not affected. The licensee notified the NRC Resident Inspector and the State of Minnesota Duty Officer.
ENS 5032731 July 2014 08:21:00MonticelloNRC Region 3GE-3Planned preventative maintenance on the Service Water Radiation Monitor (SWRM) strainer will remove the SWRM from service. As a result, this represents a loss of emergency assessment capability since the SWRM is used to assess NUE and ALERT thresholds. The activity is expected to last 6 hours. During this time, the site will be monitoring alternate indications to detect leakage and the Chemistry Department will perform grab samples as required to ensure the ability to detect NUE levels of radioactivity in a timely manner and protect the health and safety of the public. The NRC Resident Inspector has been notified prior to removing the SWRM from service.
ENS 5022524 June 2014 15:06:00MonticelloNRC Region 3GE-3

Planned preventive maintenance will render parts of telephone system and Emergency Response Data System (ERDS) nonfunctional. As a result, this represents a loss of emergency communications capability and is reportable under 10 CFR 50.72(b)(3)(xiii). The maintenance is scheduled to begin on 6/25/2014 at 00:00 (CDT), and is expected to last approximately 5 hours. During this maintenance window, various communication connections will be intermittently interrupted for short periods of time. Affected communication connections include some local telephone company lines, Federal Telephone System, ERDS, the Monticello's NRC office, and automatic ring down lines to the state of Minnesota's Emergency Operations Center. During the planned maintenance window, communications to offsite will be available via radios, cell phones, and satellite communications. This ensures that the plant can adequately communicate with the NRC, state, and local agencies to ensure protection of the health and safety of the general public. The NRC Resident Inspector has been notified of the planned telecommunications maintenance. Licensee also notified the Minnesota State Duty Officer and the Wright and Sherburne County Sheriff dispatchers.

  • * * UPDATE PROVIDED BY DAMON HESSIG TO JEFF ROTTON AT 1823 EDT ON 06/25/2014 * * *

At 0500 (CDT) on 6/25/2014, planned maintenance on the Monticello telecommunications system was completed. At 1630 (CDT) on 6/25/2014, testing of all telecommunications was completed. All systems are functioning properly. The NRC Resident Inspector has been notified that the telecommunications system is functional. The Minnesota State Duty Officer and the Wright and Sherburne County Sheriff dispatchers have been notified that the telecommunications system is functional. Notified R3DO (Lara).

ENS 501755 June 2014 17:20:00MonticelloNRC Region 3GE-3Planned preventive maintenance will render the discharge canal radiation monitors inoperable for both A and B trains. As a result, this represents a loss of emergency assessment capability and is reportable under 10 CFR 50.72 (b)(3)(xiii). The planned maintenance is expected to last two hours. During this time, the site Chemistry Department will be perform sampling as a compensatory measure. The health and safety of the public remains protected as the plant is operating in a normal condition. The NRC Resident Inspector was notified prior to removing the discharge canal radiation monitors from service.
ENS 5013623 May 2014 16:57:00MonticelloNRC Region 3GE-3At 1130 CDT, an Area Radiation Monitor (ARM) was determined to be non-functional as a result of a failed calibration test. This represents a loss of assessment capability reportable under 10CFR50.72(b)(3)(xiii). A portable radiation monitor has been placed in the affected area as a compensatory measure. The health and safety of the public was protected as the plant was in a normal condition with no initiating event in progress or signs of elevated radiation levels on any other radiation monitors. The NRC Resident Inspector has been notified. The failed ARM is located in the 'A' RHR core spray room.
ENS 5011715 May 2014 23:49:00MonticelloNRC Region 3GE-3A degraded fire barrier was identified during a walkdown on May 15th, 2014 at 1620 (CDT). The barrier separates Appendix R safe shutdown divisional equipment. A fire watch has been established as a compensatory measure. The health and safety of the public was not jeopardized as a result of this condition as there have been no fires or initiating events. The discovery of this degraded fire barrier is being reported as an unanalyzed condition as defined by 50.72(b)(3)(ii)(B). The licensee has notified the NRC Senior Resident Inspector.
ENS 500771 May 2014 09:54:00MonticelloNRC Region 3GE-3The Service Water Radiation Monitor will be removed from service to facilitate planned preventative maintenance. As a result, this represents a loss of emergency assessment capability under NUREG 1022 revision 3 specific to RU 1.2 and RA 1.2. The planned maintenance is expected to last 7 hours. During this time, the site Chemistry Department will perform sampling every thirty minutes per procedure. As a result of the sampling, reasonable assurance exists to monitor and detect rising radiation levels in order to protect the health and safety of the public. The NRC Resident Inspector has been informed.
ENS 5005223 April 2014 12:51:00MonticelloNRC Region 3GE-3Monticello 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 5004922 April 2014 15:22:00MonticelloNRC Region 3GE-3Monticello 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 5002610 April 2014 22:40:00MonticelloNRC Region 3GE-3Monticello 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 500057 April 2014 16:12:00MonticelloNRC Region 3GE-3Both Discharge Canal Radiation Monitor Sample Pumps will be removed from service to facilitate planned maintenance activities. This represents a loss of emergency assessment capability under NUREG-1022 Revision 3 since the Discharge Canal Radiation Monitors are used to assess NUE (Notification of Unusual Event) and Alert thresholds. The Sample Pumps are expected to be unavailable for approximately two hours. During this time, Chemistry will be obtaining samples every 2 hours. As a result of the sampling, reasonable assurance exists that rising radiation levels will be able to be detected and monitored in order to protect the health and safety of the public. The NRC Resident (Inspector) has been notified prior to removing the Radiation Monitors from service.
ENS 4997028 March 2014 17:21:00MonticelloNRC Region 3GE-3At 1358 (CDT) on March 28, 2014, the Control Room was notified that two Secondary Containment doors (DOOR-62 and DOOR-63) were open at the same lime. This occurred while two employees were entering and exiting the Reactor Building at the exact same time. The time that both doors were open was approximately one (1) second. Secondary Containment differential pressure was maintained throughout the event. With both doors open, technical specification surveillance requirement SR 3.6.4.1.3 was not met and Secondary Containment was declared inoperable. Secondary Containment was declared operable after independently verifying at least one Secondary Containment access door was closed. The health and safety of the public was maintained as the plant was in a normal condition with no initiating event in progress or signs or elevated radiation levels within Secondary Containment. The NRC Resident Inspector has been notified.
ENS 4993820 March 2014 17:17:00MonticelloNRC Region 3GE-3At 1020 CDT, door 410B did not automatically close and latch as required. Door 410 B is an Appendix R fire door that is required for divisional separation of safe shutdown equipment. Due to the doors inability to close and latch as required, divisional separation could not be assured in the event of a fire. A continuous fire watch was established once the deficiency was discovered. The door was repaired and verified to be working properly. The door was non-functional for approximately one hour and fifteen minutes from the time of discovery. Health and safety of the public was maintained as the plant was in a normal condition and there has been no actual condition needing the door to close and latch. The NRC Resident Inspector has been notified.
ENS 498765 March 2014 16:08:00MonticelloNRC Region 3GE-3This 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 4984621 February 2014 10:09:00MonticelloNRC Region 3GE-3At 0130 CST, a degraded power supply resulted in multiple Area Radiation Monitors (ARMs) reading erroneously low. As a result, this condition is reportable under 10 CFR 50.72(b)(3)(xiii) as these ARMs are used to assess NUE and Alert thresholds. Portable Radiation Monitors have been placed in identified affected areas as a compensatory measure. The health and safety of the public was maintained as the plant was in a normal condition with no initiating event in progress or signs of elevated radiation on any other unaffected radiation monitors. The NRC Resident Inspector has been notified.