IDAHO FALLS, Idaho (AP) — A cleanup contractor is preparing to demolish a 1960s-era nuclear reactor west of Idaho Falls.

The Post Register reports that work to remove the Experimental Breeder Reactor-II began in the spring, when contractors successfully entombed most of the reactor vessel in concrete. CWI is looking to remove the reactor's dome by the end of next September.

EBR-II began operating in 1964 at what was then Argonne National Laboratory-West and is now known as Idaho National Laboratory's Materials and Fuels Complex, about 30 miles west of Idaho Falls.

The sodium-cooled reactor was used for research and testing new fuels and materials. Before it shut down in 1994, the reactor produced as many as 20 megawatts of power. CWI has been working to decommission the reactor and related facilities since 2009.