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On February 19, 2001 with the reactor oper … On February 19, 2001 with the reactor operating at 100% power, the Monticello Nuclear Generating Plant (MNGP) staff determined that there was reasonable doubt that plant operators could manually establish torus cooling following a DBA LOCA within the 10 minute design assumption. The containment cooling system was declared inoperable. To restore operability, a dedicated operator was stationed in the control room with the sole purpose of initiating torus cooling during a LOCA.</br></br>Following an unrelated reactor shutdown on February 25, 2001, a solution team was assembled to study torus cooling issues and recommend corrective actions. The team determined that the plant procedures used to initiate torus cooling were not streamlined for emergency conditions and were not written with the purpose of satisfying the 10 minute design assumption. On March 15, 2001 with the reactor shutdown, the solution team was evaluating operator actions to support torus cooling. It was determined by a calculation of post-accident drywell conditions that the potential for flashing of the fuel zone reactor water level reference leg during a DBA LOCA, although slight, was more probable than had been previously thought. This flashing could further delay operator actions to initiate torus cooling.</br></br>Prior to startup on April 2, 2001, a modification to relocate nearly all of the fuel zone instrument reference leg piping from the drywell to the reactor building was completed. In addition, changes were made to the torus cooling procedures to directly support the 10 minute requirement and the operators were trained on these changes.e operators were trained on these changes. +
February 19, 2001 +
On February 19, 2001 with the reactor oper … On February 19, 2001 with the reactor operating at 100% power, the Monticello Nuclear Generating Plant (MNGP) staff determined that there was reasonable doubt that plant operators could manually establish torus cooling following a DBA LOCA within the 10 minute design assumption. The containment cooling system was declared inoperable. To restore operability, a dedicated operator was stationed in the control room with the sole purpose of initiating torus cooling during a LOCA.</br></br>Following an unrelated reactor shutdown on February 25, 2001, a solution team was assembled to study torus cooling issues and recommend corrective actions. The team determined that the plant procedures used to initiate torus cooling were not streamlined for emergency conditions and were not written with the purpose of satisfying the 10 minute design assumption. On March 15, 2001 with the reactor shutdown, the solution team was evaluating operator actions to support torus cooling. It was determined by a calculation of post-accident drywell conditions that the potential for flashing of the fuel zone reactor water level reference leg during a DBA LOCA, although slight, was more probable than had been previously thought. This flashing could further delay operator actions to initiate torus cooling.</br></br>Prior to startup on April 2, 2001, a modification to relocate nearly all of the fuel zone instrument reference leg piping from the drywell to the reactor building was completed. In addition, changes were made to the torus cooling procedures to directly support the 10 minute requirement and the operators were trained on these changes.e operators were trained on these changes. +
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15:11:03, 27 November 2017 +
April 19, 2001 +
February 19, 2001 +
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