Workers at the Hanford Nuclear Reservation have completed work to shut down a 400-megawatt (MW) reactor known as the Fast Flux Test Facility.
The facility, located in the Hanford site in the state of Washington, is owned by the US Department of Energy.
The reactor produced a variety of medical and industrial isotopes and provided research and testing of components and systems for advanced nuclear power systems.
The 100 workers on the project, many of whom had worked at the facility since it began operating in 1982, have been dispersed to other Hanford projects over the past year.
A decision must still be made on whether to dismantle the test reactor, which has not operated since 1992.