B Plant, T Plant, U Plant, PUREX, and REDOX (see their links) are the five facilities at Hanford where the original objective was plutonium removal from the uranium fuel rods after the rods had been subjected to the nuclear chain reaction in the Hanford reactors. Officially, each of these five facilities was called a “plutonium processing facility” or a “chemical separations plant” because chemicals were required to separate the plutonium from the rest of the irradiated fuel rod.
All of these chemical separations plants look similar to one another. They are hundreds of feet in length, with most of them standing about 80 feet high and 70 feet wide. If you were to go inside the main work area of one of these facilities, it’s kind of like going into a long warehouse. There’s lots of open space with high walls. It’s similar to being on the floor of a canyon, where you could look up and see the mountains on either side of you. Because of the similarity to how a canyon looks, the workers who built these chemical separations plants started to call them processing “canyons”. Today, these facilities are usually referred to simply as canyons.
The five canyons at Hanford are all located in the central part of the Site. Each remains highly contaminated after years of removing plutonium from irradiated fuel rods. Ultimately, all five will be decontaminated and demolished.