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On November 2, 2001, the plant was operati … On November 2, 2001, the plant was operating at 94 percent power during end-of-cycle coast down when both reactor building-to-suppression chamber vacuum relief lines were made inoperable for opening. The control switches for the air operated vacuum breaker valves in each line were simultaneously placed in the "Close" position thereby precluding the ability to automatically relieve vacuum in the suppression chamber. This action was taken in conjunction with performing a tagout for a local leak rate test (LLRT) which was to be performed while the plant was operating. The planned LLRT would have affected only one vacuum relief line at a time, necessitating only one switch at a time to be placed in "Close." However, the action to place both control switches from "Auto" to "Close" was specified on the clearance order, which would have been appropriate for only cold shutdown or refueling conditions. This improper planning was identified as the first root cause.</br></br>Subsequently, the senior reactor operator responsible for authorizing the clearance did not recognize the impact on the vacuum relief function of placing both control switches to "Close." This personnel error was identified as the second root cause. Immediate corrective action involved returning the vacuum breaker control switches to "Auto." Interim corrective actions were taken to prevent recurrence during the current outage. Additional corrective actions to prevent recurrence involve process and procedure improvements. Reference LER 2000- 009 for similar event.Reference LER 2000- 009 for similar event. +
November 2, 2001 +
On November 2, 2001, the plant was operati … On November 2, 2001, the plant was operating at 94 percent power during end-of-cycle coast down when both reactor building-to-suppression chamber vacuum relief lines were made inoperable for opening. The control switches for the air operated vacuum breaker valves in each line were simultaneously placed in the "Close" position thereby precluding the ability to automatically relieve vacuum in the suppression chamber. This action was taken in conjunction with performing a tagout for a local leak rate test (LLRT) which was to be performed while the plant was operating. The planned LLRT would have affected only one vacuum relief line at a time, necessitating only one switch at a time to be placed in "Close." However, the action to place both control switches from "Auto" to "Close" was specified on the clearance order, which would have been appropriate for only cold shutdown or refueling conditions. This improper planning was identified as the first root cause.</br></br>Subsequently, the senior reactor operator responsible for authorizing the clearance did not recognize the impact on the vacuum relief function of placing both control switches to "Close." This personnel error was identified as the second root cause. Immediate corrective action involved returning the vacuum breaker control switches to "Auto." Interim corrective actions were taken to prevent recurrence during the current outage. Additional corrective actions to prevent recurrence involve process and procedure improvements. Reference LER 2000- 009 for similar event.Reference LER 2000- 009 for similar event. +
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6 +
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05:33:04, 1 December 2017 +
December 28, 2001 +
November 2, 2001 +
Scheduling Error and Oversight Results in Loss of Reactor Building-to-Suppression Chamber Vacuum Relief Function +
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