OMAHA, Neb. (AP) — The nation’s smallest nuclear power plant is set to permanently shut down today (Monday). The Omaha Public Power District’s board decided earlier this year that the Fort Calhoun nuclear power plant is no longer financially sustainable. But the shutdown is only one of the first steps of a decommissioning process that could stretch on for as many as 60 years and cost more than $1 billion.

During that process, the utility will have to decontaminate and disassemble elements of the power plant. The nuclear plant sits on the Missouri River across from Iowa and is about 15 miles north of Omaha.