H Canyon is the only hardened nuclear chemical separations plant still in operation in the United States. Constructed in the early 1950s and beginning operations in 1955, the facility historically recovered uranium-235 and neptunium-237 from aluminum-clad, enriched-uranium fuel tubes from Site nuclear reactors and other domestic and foreign research reactors using a chemical separations process.

The interior of the building resembles a canyon because the processing areas are shaped like a gorge in a deep valley between steeply vertical cliffs. It is 835 feet long with several levels to accommodate the various stages of material stabilization, including control rooms to monitor overall equipment and operating processes; equipment and piping gallery for solution transport, storage and disposition and unique overhead bridge cranes to support overall process operations. To minimize worker exposure to radiation, work in the canyon, including maintenance, is remotely performed by overhead bridge cranes. The thick, dense concrete walls that separate workers from the actual processing areas provide added protection.