Refueling Outages

​​​​​​​Every two years, Energy Northwest takes Columbia Generating Station offline for a refueling outage. ​​​​​​​​Columbia’s 26th refueling outage (R-26) took place in May - June, 2023. 

About 1,250 skilled workers, hired locally and from across the country, join Energy Northwest’s workforce of about 1,000 e​mployees, to support refueling and maintenance projects. 

Workers replace about a third of the 764 nuclear fuel assemblies in Columbia’s core with new fuel. Fuel assemblies that have been in the reactor core for six years will be placed in Columbia's used fuel pool, which removes residual heat from the assemblies. 

After a minimum of five years in the pool, the used assemblies are moved to Columbia’s on-site dry cask storage, where they are stored securely in above-ground, 185-ton, concrete and steel, dry-storage casks. There are currently 54 casks on site, containing most of Columbia’s 39 years of used fuel​.​

Learn more

Refueling outage ​​fact sheet​