aluminum has been considered as a material for cladding fuel elements to be used in reactors cooled by high-temperature recirculating water. Aluminum is abundant, chap, has a relatively low cross section for thermal neutrons, and is readily fabricated into complex shapes. For these reasons, it appears that the use of aluminum rather than steel, Zircaloy or other candidate materials for fuel element cladding, would result in considerable savings in operating expense. The actual economics will of course depend on specific factors such as core materials and design of the reactor/. Aluminum appears particularly attractive for cladding the cores of aluminum-plutonium alloy proposed for the Plutonium Recycle Test Reactor since, in this case, the physical characteristics of the core and cladding would be practically identical.