Reflectors:

Materials which have been used as reflectors involve pure water, beryllium (as metal or oxide), heavy water (deuterium oxide), and carbon (graphite), and zirconium hydride. A selection of that material to use is based hugely on the nuclear considerations provides above and the necessary neuronic properties of the materials. The majority power reactors use water as the moderator and reflector, as well as the coolant. Graphite has been used widely as moderator and reflector for thermal reactors. The Beryllium is superior to graphite as a moderator and reflector material but, since of its high cost and poor mechanical properties, it has little prospect of being used to any extent. A Beryllium has been used in a few examples such as test reactors, but is not used in any power reactors. Reactors by using heavy water as the moderator-reflector have the benefits of being able to operate satisfactorily along with natural uranium as the fuel material; enriched uranium is then not needs. Zirconium hydride serves as the moderator in the Training, Isotopes, Research, and General Atomic (TRIGA) reactor. The zirconium hydride is incorporated along with enriched uranium metal in the fuel elements.