The mechanisms and kinetics of uranium corrosion and fuel element ruptures were investigated in water and steam at 170 C to 500 C and pressures from 100 to 2800 psig. The fuel element samples were coextruded Zircaloy-clad uranium-core rods and tubes which were defected prior to exposure. Uranium corrosion was found to be the sum of two processes;direct oxidation by water, and oxidation of uranium hydride intermediate. Fuel element ruptures occur in two stages;an initial induction period followed by an accelerating corrosion of the core causing the cladding to blister, swell, and fracture. Uranium corrosion and fuel element ruptures were examined with respect to the following parameters:temperature, pressure, steam versus liquid water, heat treatment, carbon content of uranium, zirconium content of uranium, cladding thickness, fuel geometry, annular spacings, defect geometry and size, coolant flow, hydriding of Zircaloy components, and irradiation effects.
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