A glossary of some of the nuclear terms being used as Japan’s nuclear plant crisis unfolds. Cladding: The thin-walled metal tube that forms the outer jacket of a nuclear fuel rod. It prevents both corrosion of the fuel by the coolant and the release of fission products into the coolant. Aluminum, stainless steel, and zirconium alloys are common cladding materials. Containment building: The air-tig