Nuclear fuel element

This patent describes a nuclear fuel element. It comprises: an elongated composite cladding container of a zirconium alloy tube consisting of constituents, other than the zirconium, in amounts greater than about 5000 parts per million by weight and having a barrier lining of zirconium metal in a thickness of the alloy tube, metallurgically bonded to the inner surface of the alloy tube, a central core of nuclear fuel material disposed within and partially filling the lined tubular container so as to leave a gap between the container and fuel proving the core. The nuclear fuel material being selected from the group consisting of compounds of uranium, plutonium, thorium and mixtures thereof which contain dispersed therethrough an additive of aluminum silicate in an effective amount up to about 5 percent by weight of the fuel material