GB920167A - Improvements in or relating to nuclear fuel elements - Google Patents

Abstract

920,167. Nuclear fuel elements. UNITED KINGDOM ATOMIC ENERGY AUTHORITY. Jan. 19, 1961 [Feb. 16, 1960], No. 5460/60. Class 39 (4). A fuel element comprises a fissile member 2 having a hollow core 33 enclosed in a protective sheath 3, an insert 4a of fertile material longitudinally fluted to leave cavities 35 for the accommodation of growth of the fissile member 2 being provided within the core 33 which is sealed by discs 7, 8 welded to the member 2. The fertile material may be uranium depleted in the 235 isotope (relative to the fissile member) or thorium. In one embodiment, the sheath 3 is of magnesium alloy, the member 2 of natural uranium and the insert 4a and discs 7, 8 of depleted uranium. The discs 7, 8 make good contact with the inner faces of end caps 5, 6 of magnesium alloy, which faces have cylindrical recesses 9, 10 for locating heat insulating discs 11, 12 of alumina. The end caps 5, 6 are screwthreaded into the ends of the sheath 3 to which they are sealed by welds 17, 18, the screwthreads relieving the welds from strain caused by end growth of the member 2 on irradiation. The member 2 is keyed to the sheath 3 by circumferential grooves 28 to limit creep in the sheath when the fuel element experiences thermal cycling in a reactor. So as to provide a check on the integrity of the welds 17, 18, the end caps 5, 6 are provided with circumferential grooves 29, 30 housing thin rings 31, 32 of natural uranium from which fission products produced by irradiation escape into the reactor coolant, should a weld fail, to be detected by monitoring of the coolant.