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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 FROM MICHAEL STIDMON TO HOWIE CROUCH AT 1352 EST ON 2/15/13 * * *

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).

At 0401 CST on 3/6/2013, while in RHR-High (Residual Heat Removal-High) water level the plant experienced a momentary Loss of Shutdown Cooling which resulted in a loss of safety function for Residual Heat Capability. Division 2 RHR shutdown cooling was restored within approximately 90 seconds without issue. No changes were experienced in refuel volume temperature or level during the loss of RHR shutdown cooling. This occurred shortly after a flow adjustment on the system was made utilizing the outboard valve. The inboard valve was reopened and an investigation is in progress. At the time of the valve closure, decay heat removal continued from Reactor Water Cleanup in heat reject mode and fuel pool cooling (with the fuel pool gates removed) is in service. Division 1 RHR (Shutdown Cooling) was available (not Operable) at the time of the loss. It is not currently understood why the injection valve closed. All systems functioned as required except for the spurious closing of MO-2015 (the Div 2 RHR inboard injection valve). The following make-up sources are available: Divisions 1 and 2 RHR, Divisions 1 and 2 Core Spray, CRD (Control Rod Drive), CST (Condensate Storage Tank) via a Core Spray with pressurizing station bypassed. The licensee notified the NRC Resident Inspector.

• * * RETRACTION AT 1419 EDT ON 4/11/2013 FROM RYAN RICHARDS TO MARK ABRAMOVITZ * * *

On March 6, 2013 (Notification No. 48809) NSPM (Northern States Power Monticello) reported in accordance with 10 CFR 50.72 (b)(3)(v)(B), a momentary closure of valve MO-2015 in the operating Residual Heat Removal (RHR) subsystem as an event or condition that at the time of discovery could have prevented the fulfillment of a safety function. Following the event, the RHR SDC (shut down cooling) subsystem was removed from operation for equipment forensics and troubleshooting. Results validated that valve MO-2015 was operable and no issues were identified with the associated electrical circuitry, or the RHR SDC subsystem. The decay heat removal requirements of LCO 3.9.7, RHR - High Water Level, were met and there was not a loss of safety function. Therefore, NSPM retracts the March 6, 2013 notification for this event. The licensee notified the NRC Resident Inspector, state and local authorities, and may make a press release. Notified the R3DO (Passehl).

On August 27, 2013 at 2152 CDT, Monticello Nuclear Generating Plant (MNGP) experienced a runback of (the) 'B' Recirc pump from 87% speed to 71% speed. Operators took action to lock (the) 'B Recirc pump scoop tube. This runback resulted in a power reduction from 100% to 94% RTP (Rated Thermal Power). With the resultant mismatch between total jet pump flows of the two loops greater than required limits, should a LOCA (Loss of Coolant Accident) occur, the core flow coastdown and resultant core response may not be bounded by the LOCA analyses. It has been determined that this is an unanalyzed condition as defined by 10CFR50.72(b)(3)(ii)(8). At 0121 CST on August 28, 2013, MNGP completed reducing power to 88% using 'A' Recirc pump to match total jet pump flows and (the plant) is no longer in an unanalyzed condition. The 'B' Recirc scoop tube remains locked pending investigation. The licensee has notified the NRC Resident Inspector.

• * * RETRACTION ON 10/11/13 AT 1253 EDT FROM MARK HOESCHEN TO DONG PARK * * *

This is a retraction for ENS 49312: The licensee reviewed the MNGP design basis analysis to determine if the event was bounded. The licensee determined that the Loss of Coolant Accident (LOCA) provides a bounding analysis for this event. The limiting LOCA event for the MNGP as analyzed in accordance with 10CFR50 Appendix K conditions is based upon single failure of the Low Pressure Coolant Injection (LPCI) injection valve, effectively making LPCI inoperable for the event. The large break Design Basis Accident (DBA) with LPCI injection valve failure (which is analytically equivalent to the condition of both LPCI subsystems being inoperable) is the event analyzed for the current Licensing Basis Peak Cladding Temperature (PCT). This analysis bounds the event as a recirculation pump flow mismatch event is less limiting than the LOCA with LPCI injection valve failure analysis. Therefore, this recirculating loop flow mismatched event is less limiting than a previously analyzed event and ENS 49312 may be retracted as an unanalyzed event. The licensee has notified the NRC Resident Inspector. Notified R3DO (Skokowski).

On September 1, 2013 at 1610 CST, Monticello Nuclear Generating Plant (MNGP) experienced a runback of 'A' Recirc pump from 87% speed to 82% speed. Operators took action to lock 'A' Recirc pump scoop tube. This runback resulted in a power reduction from 100% to 98% RTP (Rated Thermal Power). Should a LOCA (Loss of Coolant Accident) occur with the resultant mismatch between total jet pump flows of the two loops greater than required limits, the core flow coastdown and resultant core response may not be bounded by the LOCA analyses. It has been determined that this is an unanalyzed condition as defined by 10CFR50.72(b)(3)(ii)(B). At 2123 CST on September 1, 2013, MNGP completed adjusting recirc flow speed on 'A' and 'B' Recirc pumps to match jet pump loop flows to within the required limits and is no longer in an unanalyzed condition. Both 'A' and 'B' Recirc scoop tubes remain locked pending investigation. The licensee has notified the NRC Resident Inspector.

• * * RETRACTION ON 10/11/13 AT 1253 EDT FROM MARK HOESCHEN TO DONG PARK * * *

This is a retraction for ENS 49316: The licensee reviewed the MNGP design basis analysis to determine if the event was bounded. The licensee determined that the Loss of Coolant Accident (LOCA) provides a bounding analysis for this event. The limiting LOCA event for the MNGP as analyzed in accordance with 10CFR50 Appendix K conditions is based upon single failure of the Low Pressure Coolant Injection (LPCI) injection valve, effectively making LPCI inoperable for the event. The large break Design Basis Accident (DBA) with LPCI injection valve failure (which is analytically equivalent to the condition of both LPCI subsystems being inoperable) is the event analyzed for the current Licensing Basis Peak Cladding Temperature (PCT). This analysis bounds the event as a recirculation pump flow mismatch event is less limiting than the LOCA with LPCI injection valve failure analysis. Therefore, this recirculating loop flow mismatched event is less limiting than a previously analyzed event and ENS 49316 may be retracted as an unanalyzed event. The licensee has notified the NRC Resident Inspector. Notified R3DO (Skokowski).

While performing the secondary containment airlock door interlock surveillance, the interlock to the main plenum room did not prevent the opening of both doors to the plenum room airlock (DOOR-85 and DOOR-86). The plenum room airlock doors were immediately closed. The time both doors were opened is estimated to be approximately one (1) second. When 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. There were no radiological releases associated with this event. The NRC Resident Inspector has been notified.

• * * UPDATE FROM KIM HOFFMAN TO HOWIE CROUCH AT 1753 EDT ON 9/20/13 * * *

This update provides additional information on the initial notification of the event. On 9/18/13, while testing secondary containment airlock doors, the interlocks did not prevent opening of both doors simultaneously. With the outer door to the main plenum room open, the inner door was able to be opened. At this point, Technical Specification SR 3.6.4.1.3 was not met and secondary containment was inoperable. The inner door was closed immediately. While in this condition, the inner door was then opened, and the interlock did not prevent the opening of the outer door. The outer door was closed immediately. Secondary containment was declared operable after verifying at least one of the airlock doors was closed. There were no radiological releases associated with this event. The NRC Resident Inspector has been notified. Notified R3DO (Reimer).

On 9/27/13, Monticello Nuclear Generating Plant's Technical Support Center power supply will be isolated to perform a planned maintenance activity. The maintenance activity may require implementation of compensatory measures to maintain TSC functionality during the activity. The compensatory measures include having the Emergency Director report to the Control Room and co-locating the remaining TSC staff at the EOF should an event be declared requiring ERO activation. The ERO has previously successfully demonstrated the ability to implement these compensatory measures. The maintenance activity is scheduled to be completed with the TSC returned to full functionality by the end of the dayshift on 9/27/13. The Site Emergency Response Organization has been notified of the maintenance activity. The licensee has notified the NRC Resident Inspector.

• * * UPDATE ON 9/27/13 AT 1916 EDT FROM MARK IHLENFELDT TO DONG PARK * * *

On 9/27/13, Monticello Nuclear Generating Plant's Technical Support Center power supply was isolated to perform a planned maintenance activity. The maintenance activity required implementation of compensatory measures to maintain TSC functional during the activity. Maintenance activity is completed and TSC is fully functional and returned to service. Site Emergency Response Organization has been notified. The licensee has notified the NRC Resident Inspector. Notified R3DO (Dickson).

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

• * * UPDATE FROM JON LAUDENBACH TO VINCE KLCO ON 1/20/14 AT 1259 EST * * *

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).

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).

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).