The Nuclear Regulatory Commission says it’s monitoring a decrease in the coolant level in 1 of the two reactors at the Prairie Island nuclear power plant in Welch Minnesota. An “unusual event” occurred at 6:24 a.m., this morning at Prairie Island nuclear plant, the Nuclear Regulatory Commission reported. The declaration was made due to an indication of an increase in reactor coolant system leakage.

Unit 2 currently is shut down for a refueling outage. Unit 1 is at full power. The workers at the plant identified an apparent decrease in reactor vessel coolant level and are taking actions to further understand the situation. The plant is maintaining the appropriate level of water in the reactor. The NRC is monitoring the plant’s efforts.

Two NRC resident inspectors have responded to the site, and once the event is over the NRC will investigate the cause of the incident, they said.

Prairie Island 2 – 2011 Plant Inspection Findings

Flammable Gas Bottles Installed and/or Stored in the Auxiliary Building – Inspection Report# : 2011012 (pdf)

FAILURE TO MAKE EIGHT HOUR REPORT PURSUANT TO 10 CFR 50.72. – Inspection Report# : 2011004 (pdf)

FAILURE TO MAKE EIGHT HOUR REPORT PURSUANT TO 10 CFR 50.72. Finding. – Inspection Report# : 2011004 (pdf)

UNIT 2 REACTOR TRIP DUE TO MIS-OPERATION OF SUBSTATION BREAKERS – Inspection Report# : 2011004 (pdf)

FLAMMABLE GAS CYLINDER STORED IN SAFETY-RELATED AREA. – Inspection Report# : 2011002 (pdf)

Failure to Complete Immediate Operability Determination on Molded Case Circuit Breakers – Inspection Report# : 2011005 (pdf)

Failure to Correct a Condition Adverse to Quality – Inspection Report# : 2011012 (pdf)

RADIATION MONITORS NOT FULLY SCOPED INTO OR ASSESSED BY THE MAINTENANCE RULE PROGRAM. – Inspection Report# : 2011004 (pdf)

CORRECTIVE ACTION ASSIGNMENTS CLOSED WITHOUT COMPLETION OF TASKS. – Inspection Report# : 2011004 (pdf)

FAILURE TO PROVIDE COMPLETE AND ACCURATE INFORMATION IN A LICENSEE EVENT REPORT – Inspection Report# : 2011004 (pdf)

FAILURE TO PROVIDE COMPLETE AND ACCURATE INFORMATION IN A LICENSEE EVENT REPORT – Inspection Report# : 2011004 (pdf)

EVALUATION OF EQUIPMENT STORED NEAR SAFETY-RELATED EQUIPMENT. – Inspection Report# : 2011003 (pdf)

GL 2008-01 EVALUATIONS DID NOT ADEQUATELY VERIFY THE DESIGN FOR SUSCEPTIBLE LOCATIONS OF GAS ACCUMULATION IN PIPING SYSTEMS. – Inspection Report# : 2011003 (pdf)

ALTERNATE METHODS WERE NOT DEVELOPED FOR MONITORING INACCESSIBLE SUSCEPTIBLE LOCATIONS. – Inspection Report# : 2011003 (pdf)

FAILURE TO ENSURE THAT THE TRAIN A AND THAIN B DC ELECTRICAL POWER SUBSYSTEMS REMAINED OPERABLE IN MODES 1 THROUGH 4. – Inspection Report# : 2011011 (pdf)

NO FULL FLOW TESTING OF PORV AIR SUPPLY CHECK VALVES. – Inspection Report# : 2011003 (pdf)

FAILURE TO EVALUTE THE EFFECTS OF DYNAMIC LOADS AT THE CS DISCHARGE PIPING. – Inspection Report# : 2011003 (pdf)

FAILURE TO PRESCRIBE APPROPRIATE PROCEDURE FOR IN-SERVICE TESTING OF CHECK VALVES. – Inspection Report# : 2011003 (pdf)

INCOMPLETE AND INACCURATE EMERGENCY ACTION LEVEL CHANGE SUBMITTAL. – Inspection Report# : 2011502 (pdf)

Failure to identify that information provided to the NRC was Incomplete and Inaccurate regarding Emergency Action Level setpoints (1EP4.1.b) – Inspection Report# : 2011502 (pdf)

FAILURE TO ASSESS THE IMPACT OF CHANGES IN THE PLANT’S ISOTOPIC PROFILE. – Inspection Report# : 2011003 (pdf)

Preliminary Notification (PN) Reports for 2011

December PNO-I-11-004A 12/16/2011 Constellation Energy Nuclear Group, LLC: Nine Mile Point Unit 2 Technical Specification-Required Shutdown Due to an Increase in Unidentified Reactor Coolant System Leakage – (Update) PNO-I-11-004 12/12/2011 Constellation Energy Nuclear Group, LLC: Nine Mile Point Unit 2 Technical Specification-Required Shutdown Due to an Increase in Unidentified Reactor Coolant System Leakage PNO-III-11-016A 12/12/2011 Northern States Power Company: Monticello Shutdown Greater Than 72 Hours Due To Actuation Of Reactor Protection Relays Sensing Low Turbine Control Valve Hydraulic Pressure – (Update) November PNO-II-11-006A 11/30/2011 Carolina Power and Light Company: Brunswick Unit 2 Notification of Unusual Event (NOUE) Due To Reactor Coolant System Leakage – (Update) PNO-IV-11-009 11/30/2011 South Texas Project Nuclear Operating Company: South Texas Project Unit 2 Reactor Trip PNO-III-11-017 11/28/2011 NextEra Energy Point Beach: Point Beach Unit 1 Declares Notification of Unusual Event Due to Loss of Offsite Power PNO-III-11-016 11/22/2011 Northern States Power Company: Monticello Shutdown Greater Than 72 Hours Due To Actuation Of Reactor Protection Relays Sensing Low Turbine Control Valve Hydraulic Pressure PNO-II-11-006 11/16/2011 Carolina Power and Light Company: Brunswick Unit 2 Declares a Notice Of Unusual Event (NOUE) PNO-IV-11-008 11/02/2011 Southern California Edison: Ammonia Leak Causes Evacuation of Unit 3 Turbine Building and Alert Declaration October PNO-III-11-015A 10/28/2011 Northern States Power Company: Unplanned Shutdown Greater Than 72 Hours Due To A Loss Of The Auxiliary Power Transformer – (Update) PNO-III-11-015 10/25/2011 Northern States Power Company: Unplanned Shutdown Greater Than 72 Hours Due To A Loss Of The Auxiliary Power Transformer PNO-III-11-014 10/20/2011 FirstEnergy Nuclear Operating Company: Davis-Besse Shield Building Indications PNO-III-11-013A 10/20/2011 Northern States Power Company: Prairie Island Unit 2 Unplanned Shutdown for Greater than 72 Hours – (Update) PNO-III-11-012A 10/19/2011 FirstEnergy Nuclear Operating Company: Perry Unplanned Shutdown Greater Than 72 Hours – (Update) PNO-III-11-013 10/05/2011 Northern States Power Company: Prairie Island Unit 2 Unplanned Shutdown for Greater than 72 Hours PNO-III-11-012 10/05/2011 FirstEnergy Nuclear Operating Company: Perry Unplanned Shutdown Greater Than 72 Hours PNO-III-11-011A 10/03/2011 Entergy Nuclear Operations, Inc.: Palisades Reactor Trip – (Update) September PNO-III-11-011 09/27/2011 Entergy Nuclear Operations, Inc.: Palisades Reactor Trip PNO-III-11-010 09/19/2011 Entergy Nuclear Operations, Inc.: Palisades Unplanned Shutdown Greater than 72 Hours and Notification of Unusual Event PNO-IV-11-007 09/19/2011 Union Electric Company: Alert Declared at Callaway Plant PNO-IV-11-006 09/15/2011 Queen’s Medical Center: Medical Event Involving Patient Overexposure August PNO-IV-11-003F 08/30/2011 Fort Calhoun Station: Fort Calhoun Station Declaration of a Notification of Unusual Event Due to High River Level – (Update) PNO-II-11-005A 08/24/2011 Virginia Electric and Power Company (North Anna Power Station, Units 1 and 2): Alert – Emergency Declarations Due to Seismic Event Calvert Cliffs Nuclear Power Plant, DC Cook, Hope Creek Generating Station, Limerick Generating Station, Oyster Creek Nuclear Generating Station, Palisades, Peach Bottom Atomic Power Station, Salem Nuclear Generating Station, Shearon Harris Nuclear Plant, Surry Power Station, Units 1 and 2, Susquehanna Power Station, & Three Mile Island Nuclear Station: Notification of Unusual Event – Emergency Declarations Due to Seismic Event – (Update) PNO-II-11-005 08/23/2011 Virginia Electric and Power Company (North Anna Power Station, Units 1 and 2): Alert – Emergency Declarations Due to Seismic Event Calvert Cliffs Nuclear Power Plant, DC Cook, Hope Creek Generating Station, Limerick Generating Station, Oyster Creek Nuclear Generating Station, Palisades, Peach Bottom Atomic Power Station, Salem Nuclear Generating Station, Shearon Harris Nuclear Plant, Surry Power Station, Units 1 and 2, Susquehanna Power Station, & Three Mile Island Nuclear Station: Notification of Unusual Event – Emergency Declarations Due to Seismic Event PNO-I-11-003A 08/15/2011 Constellation Energy Nuclear Group, LLC: Nine Mile Point Unit 2 Notification of Unusual Event Due to Reactor Coolant System Leak Greater Than 10 GPM and Plant Shutdown Greater Than Three Days – (Update) PNO-III-11-009 08/12/2011 NextEra Energy: Duane Arnold Unplanned Shutdown Greater Than 72 Hours PNO-I-11-003 08/09/2011 Constellation Energy Nuclear Group, LLC: Nine Mile Point Unit 2 Notification of Unusual Event Due to Reactor Coolant System Leak Greater Than 10 GPM and Plant Shutdown Greater Than Three Days July PNO-II-11-004 07/27/2011 United States Enrichment Corporation: Chlorine Trifluoride Release at the Paducah Gaseous Diffusion Plant PNO-I-11-001A 07/27/2011 Constellation Energy Nuclear Group, LLC: Nine Mile Point Units 1 and 2 Strike PNO-IV-11-003E 07/26/2011 Fort Calhoun Station: Fort Calhoun Station Declaration of a Notification of Unusual Event Due to High River Level – (Update) PNO-I-11-002A 07/19/2011 PSEG: Salem Generating Station Notification of Unusual Event Due to Reactor Coolant System Leak Greater than 10 GPM and Technical Specifications Required Shutdown – (Update) PNO-I-11-002 07/15/2011 PSEG: Salem Generating Station Notification of Unusual Event Due to Reactor Coolant System Leak Greater than 10 GPM and Technical Specifications Required Shutdown PNO-IV-11-005A 07/13/2011 Cooper Nuclear Station: Cooper Nuclear Station Declaration of a Notification of Unusual Event Due to High River Level – (Update) PNO-I-11-001 07/11/2011 Constellation Energy Nuclear Group, LLC: Nine Mile Point Units 1 and 2 Strike June PNO-IV-11-003D 06/30/2011 Fort Calhoun Station: Fort Calhoun Station Declaration of a Notification of Unusual Event Due to High River Level – (Update) PNO-III-11-008A 06/29/2011 Northern States Power Co./Monticello Nuclear Generating Plant: Monticello Shutdown Greater Than 72 Hours Due To A Leaking Safety Relief Valve – (Update) PNO-IV-11-003C 06/27/2011 Fort Calhoun Station: Fort Calhoun Station Declaration of a Notification of Unusual Event Due to High River Level – (Update) PNO-III-11-008 06/27/2011 Northern States Power Co./Monticello Nuclear Generating Plant: Monticello Shutdown Greater Than 72 Hours Due To A Leaking Safety Relief Valve PNO-IV-11-003B 06/26/2011 Fort Calhoun Station: Fort Calhoun Station Declaration of a Notification of Unusual Event Due to High River Level – (Update) PNO-IV-11-003A 06/20/2011 Fort Calhoun Station: Fort Calhoun Station Declaration of a Notification of Unusual Event Due to High River Level – (Update) PNO-IV-11-005 06/20/2011 Cooper Nuclear Station: Cooper Nuclear Station Declaration of a Notification of Unusual Event Due to High River Level PNO-IV-11-004A 06/08/2011 Fort Calhoun Station: Fort Calhoun Station Declaration of an ALERT Due to Fire Affecting Plant Safety Systems – (Update) PNO-III-11-007 06/08/2011 Braidwood Declares Notice of Unusual Event Due to Potential Damage to Auxiliary Feedwater Pumps PNO-IV-11-004 06/07/2011 Fort Calhoun Station: Fort Calhoun Station Declaration of an ALERT Due to Fire Affecting Plant Safety Systems PNO-IV-11-003 06/06/2011 Fort Calhoun Station: Fort Calhoun Station Declaration of a Notification of Unusual Event Due to High River Level May PNO-III-11-006 05/05/2011 NextEra Energy Duane Arnold, LLC: Alert at Duane Arnold Energy Center PNO-II-11-003B 05/02/2011 Browns Ferry Units 1, 2, and 3: Notification of Unusual Event Due to Loss of Offsite Power – (Update) April PNO-II-11-003A 04/28/2011 Browns Ferry Units 1, 2, and 3: Notification of Unusual Event Due to Loss of Offsite Power – (Update) PNO-II-11-003 04/27/2011 Browns Ferry Units 1, 2, and 3: Notification of Unusual Event Due to Loss of Offsite Power PNO-II-11-002B 04/19/2011 Surry Virginia Electric and Power Co. Units 1 and 2: Notification of Unusual Event Due to Loss of Offsite Power – (Update) PNO-II-11-002A 04/18/2011 Surry Virginia Electric and Power Co. Units 1 and 2: Notification of Unusual Event Due to Loss of Offsite Power – (Update) PNO-II-11-002 04/17/2011 Surry Virginia Electric and Power Co. Units 1 and 2: Notification of Unusual Event Due to Loss of Offsite Power PNO-IV-11-002 04/08/2011 Energy Northwest:Columbia Generating Station Notification of Unusual Event March PNO-III-11-005 03/24/2011 Exelon Generation Company, LLC: Braidwood Unit 2 Unusual Event Due to Loss of all Control Room Communications PNO-IV-11-001A 03/14/2011 Pacific Gas and Electric Company: Diablo Canyon Power Plant Notification of Unusual Event (Update) PNO-IV-11-001 03/11/2011 Pacific Gas and Electric Company: Diablo Canyon Power Plant Notification of Unusual Event February PNO-III-11-004A 02/14/2011 Exelon Generation Co.: LaSalle Unit 1 Restart Following Automatic Reactor Scram and Shutdown Greater than 72 Hours Due to a Main Power Transformer Trip PNO-III-11-004 02/03/2011 Exelon Generation Co.: LaSalle Unit 1 Automatic Reactor Scram and Shutdown Greater than 72 Hours Due to Main Power Transformer Trip January PNO-III-11-003 01/24/2011 Entergy Nuclear Operations, Inc.: Palisades Shutdown Due to Loss of Main Generator Electrical Load PNO-II-11-001 01/21/2011 McGuire Nuclear Station: Shut Down Due to Service Water Strainer Blockage PNO-III-11-002 01/19/2011 FirstEnergy Nuclear Operating Company: Davis-Besse Unusual Event Due to 480V Cable Fire PNO-III-11-001 01/11/2011 Entergy Nuclear Operations Inc.: Palisades Unusual Event and 72-Hour Limiting Condition for Operation Due to 4160 V Ground Fault

Preliminary Notification (PN) Reports for 2012

March PNO-III-12-002A 03/02/2012 Exelon Generation Company, LLC: Byron Unit 1 Loss of Offsite Power and Declaration of a Notice of Unusual Event – (Update) February PNO-III-12-002 02/29/2012 Exelon Generation Company, LLC: Byron Unit 1 Loss of Offsite Power and Declaration of a Notice of Unusual Event PNO-III-12-001 02/07/2012 Exelon Generation Company, LLC: Byron Unit 2 Restarts After a Loss of Offsite Power and Declaring a Notice of Unusual Event PNO-IV-12-003 02/01/2012 Southern California Edison Company: San Onofre Unit 3 Steam Generator Tube Leak and Rapid Shutdown January PNO-IV-12-002A 01/30/2012 Wolf Creek Nuclear Operating Corp.: Augmented Inspection Team Onsite at Wolf Creek Generating Station – (Update) PNO-IV-12-002 01/18/2012 Wolf Creek Nuclear Operating Corp.: Wolf Creek Generating Station Notification of Unusual Event PNO-IV-11-009A 01/12/2012 South Texas Project Nuclear Operating Company: South Texas Project Unit 2 Reactor Trip – (Update)

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