Patent Number: 042004926
Section: claims

1. A nuclear fuel element which comprises an elongated composite cladding container having a zirconium alloy tube containing constituents other than zirconium in an amount greater than about 5000 parts per million and a barrier of sponge zirconium metallurgically bonded to the inside surface of the alloy tube, said sponge zirconium barrier being of thickness from about 1% to 30% of the thickness of the said alloy tube, a central core of a body of nuclear fuel material selected from the group consisting of compounds of uranium, plutonium, thorium and mixtures thereof disposed in and partially filling said container so as to leave a gap between said container and said core and an internal cavity at one end of the container an enclosure integrally secured and sealed at each end of said container and a nuclear fuel material retaining means positioned in the cavity. 2. The nuclear fuel element of claim 1 which has in addition a cavity inside the fuel element and a nuclear fuel material retaining means comprising a helical member positioned in the cavity. 3. A nuclear fuel element of claim 1 in which the nuclear fuel material is comprised of plutonium compounds. 4. A nuclear fuel element of claim 1 in which the nuclear fuel material is comprised of uranium dioxide. 5. A nuclear fuel element of claim 1 in which the nuclear fuel material is a mixture comprising uranium dioxide and plutonium dioxide.