The nuclear power plant near Richland generated a record 9.7 million megawatt hours of electricity for the fiscal year that ended Monday.
The previous record for the Energy Northwest plant for a fiscal year was 9.5 million megawatts in fiscal 2006.
The Columbia Generating Station had no refueling outage in the past 12 months and it has operated more than 4.5 years without an unplanned shutdown, said Energy Northwest spokesman John Dobken.
Energy Northwest officials credit the record generation to a focus on excellence and performance and keeping plant equipment fixed and maintained.
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"Most importantly, the team reached this milestone while performing safely in the areas of nuclear, radiological, industrial and environmental safety," said Brad Sawatzke, vice president of nuclear generation, in a message to employees.