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Category:NRC Preliminary Notification of Event/Occurrence
MONTHYEARPNO-III-23-001A, Update to Preliminary Notification of Event or Unusual Occurrence - PNO-III-23-0012023-07-21021 July 2023
PNO-III-23-001A: Update to Preliminary Notification of Event or Unusual Occurrence - PNO-III-23-001
PNO-III-23-001, Monticello Nuclear Plant Unplanned Shutdown Due to Increased Tritium Levels2023-03-27027 March 2023
PNO-III-23-001 Monticello Nuclear Plant Unplanned Shutdown Due to Increased Tritium Levels
PNO-III-19-003, Monticello Nuclear Generating Plant Expiration of Security Supervisor Union Contract2019-08-29029 August 2019
PNO-III-19-003: Monticello Nuclear Generating Plant Expiration of Security Supervisor Union Contract
PNO-III-15-010, A UPDATE-Monticello Automatic Scram Due to Reactor Protection System Signal2015-12-0303 December 2015
PNO-III-15-010A UPDATE-Monticello Automatic Scram Due to Reactor Protection System Signal
ML15331A3442015-11-27027 November 2015
PNO-III-15-010 - Monticello Automatic Scram Due to Reactor Protection System Signal
PNO-III-14-001, A - Update to Monticello Shutdown Due to Reactor Coolant System (RCS) Pressure Boundary Leakage in Excess of Technical Specification Limits2014-02-0707 February 2014
PNO-III-14-001-A - Update to Monticello Shutdown Due to Reactor Coolant System (RCS) Pressure Boundary Leakage in Excess of Technical Specification Limits
ML14022A0222014-01-21021 January 2014
PNO-III-14-001: Monticello Shutdown Due to RCS Pressure Boundary Leakage in Excess of Technical Specification Limits
ML12234A6372012-08-20020 August 2012
Update to Monticello Shutdown Due to Drywell Unidentified Leakage Above Technical Specification Limits
ML12229A3152012-08-16016 August 2012
PNO-lll-12-009 - Monticello Shutdown Due to Drywell Unidentified Leakage Above Technical Specification Limits
PNO-III-11-016, A - Monticello Shutdowngreater than 72 Hours Due to Actuation of Reactor Protection Relays Sensing Low Turbine Control Valve Hydraulic Pressure (Update)2011-12-12012 December 2011
PNO-III-11-016-A - Monticello Shutdowngreater than 72 Hours Due to Actuation of Reactor Protection Relays Sensing Low Turbine Control Valve Hydraulic Pressure (Update)
ML11327A0262011-11-22022 November 2011
PNO-III-11-016, Monticello - Shutdown Greater than 72 Hours Due to Actuation of Reactor Protection Relays Sensing Low Turbine Control Valve Hydraulic Pressure
PNO-III-11-015, A, Monticello - Unplanned Shutdown Greater than 72 Hours Due to a Loss of the Auxiliary Power Transformer (Update)2011-10-28028 October 2011
PNO-III-11-015A, Monticello - Unplanned Shutdown Greater than 72 Hours Due to a Loss of the Auxiliary Power Transformer (Update)
ML11298A0652011-10-25025 October 2011
PNO-III-11-015, Monticello - Unplanned Shutdown Greater than 72 Hours Due to a Loss of the Auxiliary Power Transformer
PNO-III-11-008, A - Monticello - Update to Monticello Shutdown Greater than 72 Hours Due to a Leaking Safety Relief Valve2011-06-29029 June 2011
PNO-III-11-008A - Monticello - Update to Monticello Shutdown Greater than 72 Hours Due to a Leaking Safety Relief Valve
ML11178A0192011-06-27027 June 2011
PNO-III-11-008, Monticello Shutdown Greater than 72 Hours Due to a Leaking Safety Relief Valve
PNO-III-08-009, A, Monticello - Unplanned Shutdown Greater than 72 Hours - Update2008-09-29029 September 2008
PNO-III-08-009A, Monticello - Unplanned Shutdown Greater than 72 Hours - Update
PNO-III-08-010, Monticello - Loss of Offsite Power2008-09-17017 September 2008
PNO-III-08-010: Monticello - Loss of Offsite Power
ML0825906682008-09-15015 September 2008
PNO-III-08-009, Monticello, Unplanned Shutdown Greater than 72 Hours
PNO-III-07-001, A - Monticello Reactor Shutdown Due to Turbine Control Valve Failure (Update)2007-01-22022 January 2007
PNO-III-07-001A - Monticello Reactor Shutdown Due to Turbine Control Valve Failure (Update)
ML0701202562007-01-12012 January 2007
PNO-III-07-001: Monticello Reactor Shutdown Due to Turbine Control Valve Failure (Event Notification EN 43088)
2023-07-21
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January 12, 2007PRELIMINARY NOTIFICATION OF EVENT OR UNUSUAL OCCURRENCE -- PNO-III-07-001This preliminary notification constitutes EARLY notice of events of POSSIBLE safety or publicinterest significance. The information is as initially received without verification or evaluation, andis basically all that is known by the Region III staff on this date.FacilityMonticelloNuclear Management Co.Monticello, MNDocket: 50-263License: DPR-22Licensee Emergency Classification Notification of Unusual Event Alert Site Area Emergency General Emergency X Not Applicable
SUBJECT:
MONTICELLO REACTOR SHUTDOWN DUE TO TURBINE CONTROL VALVEFAILURE (EVENT NOTIFICATION EN 43088)DESCRIPTION:
At 3:28 p.m. CDT on January 10, 2007, the reactor shut down automatically after all four turbinecontrol valves unexpectedly opened subsequent to turbine control valve testing. Prior to thetrip, the reactor was at 90 percent power and stable. The open control valves caused adecrease in main steam line pressure which eventually led to the automatic scram. All safetysystems functioned as designed during the reactor scram. Because of the decrease in main steam line pressure when the control valves opened, the mainsteam isolation valves automatically closed; preventing the use of the main condenser fordecay heat removal. Cooldown and depressurization was accomplished using a combination ofmanual manipulation of the safety relief valves, and the High Pressure Coolant Injection andReactor Core Isolation Systems. The reactor is currently stable and in the cold shutdowncondition, with the residual heat removal system being used for decay heat removal. During the initial investigation of the cause of the scram, the licensee identified that the turbinecontrol valve actuator box was displaced by 8-12 inches, as a result of damage to the weldsthat connected the actuator platform to the support I-beams. Plant staff and the residentinspectors are investigating the cause of the weld damage and the turbine valve closure, aswell as whether the two problems are connected.The plant will remain shut down until the root causes for the two issues are identified and theturbine control valve problems are repaired.NRC resident inspectors are monitoring the situation. Additional NRC inspections will augmentthe resident inspectors to assist in gathering information concerning the apparent structuralfailures that resulted in the displacement of the turbine control valve actuator box. The State of Minnesota has been informed.
The event was reported to the NRC at 7:46 EDT on January 11, 2007. This information hasbeen discussed with licensed management and is current as of 10:00 a.m. CDT on January 12, 2007.
This preliminary notification will be updated as close to plant restart as possible.CONTACTS:
Nick ShahBruce Burgess630/829-9821630/829-9629
