Kennewick — The Northwest’s only commercial nuclear power reactor disconnected from the grid Friday evening for the start of a planned 35-day refueling outage.
The Columbia Generating Station is shut down every other spring, when electricity demand is low and hydropower from spring snowmelt is plentiful.
The outage is used to add fresh fuel to the reactor core and to allow maintenance that is difficult while the plant is operating.
During the outage, the plume of water vapor that can usually be seen from most of the Tri-Cities will be absent.
The Energy Northwest nuclear power reactor is 10 miles north of Richland on leased land at the Hanford nuclear reservation site, but is unrelated to the World War II and Cold War weapons work and ongoing environmental cleanup there.
Before disconnecting from the grid Friday, the reactor achieved its second longest operating run in its 38-year history, 508 days online, according to Energy Northwest
The refueling outage requires about 1,200 temporary workers, including both Tri-Cities area residents and workers from across the country who fill campsites and any available temporary housing near the Tri-Cities for months before and during the outage.
They join the permanent Energy Northwest staff of 1,000 workers.
Crews will swap out 248 of the 764 nuclear fuel assemblies in Columbia’s reactor core with new fuel.
Fuel assemblies that have been in the reactor core for six years will be removed and placed in Columbia’s used fuel pool, which removes residual heat. After a minimum of five years in the pool, the used fuel will be moved to Energy Northwest’s outdoor dry-cask storage.
Energy Northwest also has a list of about 7,500 tasks to be completed during the outage by the reactor’s temporary and permanent employees.
Maintenance projects include inspecting the high-pressure turbine and moisture separator reheater.
A reactor feedwater drive turbine and pump, along with back-up transformer oil circuit breakers, will be replaced. Various valves with have diagnostic testing, with some replacements and refurbishments done.
“For the next several weeks, our focus will be safely completing the work to ensure Columbia continues to produce reliable and around-the-clock, carbon-free power for the region,” said Grover Hettel, Energy Northwest chief nuclear officer.
Columbia Generating Station is a 1,207 megawatt boiling water reactor that produces about 10% of the electricity used in Washington state. All of its electricity is provided at cost to the Bonneville Power Administration.
