CALANDRIA

The calandria is the vessel that stores the fuel bundles in light water reactors. It is made up of many metal pressure tubes that stretch horizontally through the casing so fuel can be added and removed without shutting the reactor down. In most reactors today, robotic arms can open the tube caps, slide a new fuel bundle in and collect the spent fuel bundle on the other side. There are hundreds of pressure tubes, with the exact number differing based on the type of reactor. Nonetheless in all designs, a coolant flows through all the tubes and each tube is seperated by a spacer. The calandria is considered the "core" of the reactor. The vessel itself is not pressured and as such, remains at much lower temperatures then the fuel bundle. Calandrias are very large, and are considered an essential part of many reactor designs.