Roughly 2,000 temporary workers have come to the Tri-Cities as they join permanent staff at the Columbia Generating Station to replace hundreds of nuclear fuel arrays and complete thousands of other maintenance tasks for the next two months. 

The nuclear power plant was disconnected from the power grid on April 11 at the start of its 56-day refueling cycle, according to a release from Energy Northwest, the plant’s operator. 

The refueling comes after the plant’s second-longest operating cycle – 662 days or about a year and 10 months – since it became operational 40 years ago. It also is taking place when spring snowmelt puts hydroelectric power generation at its peak, minimizing any disruption to the power grid. 

Roughly a third of the plant’s fuel assemblies – 256 – will be replaced and placed in a used fuel pool before their transfer to dry storage.  

Among the more than 10,000 scheduled maintenance tasks are replacing the adjustable speed drive and a reactor recirculating pump and motor, valve repairs and upgrading the 230kV transmission line.