Model for liquid uranium and plutonium with implications on the adjacent solid phases

The hard-sphere model for liquid metals, which is used to analyze the physical properties of liquid uranium and plutonium, predicted successfully only the compressibility of liquid plutonium while it underestimated the measured viscosity and surface tension values. Based upon a correlation with the rare earth elements, the heat capacities of liquid uranium and plutonium were smaller and their heats of vaporization were larger than predicted. All these deviations suggest additional attractive energy in these two liquids. Diffusion and positron annihilation experiments suggest the appearance of liquid-like clusters in the bcc phases that exist in equilibrium with these liquids. The elastic modulus of /sub epsilon/Pu without these clusters was calculated to be approximately five times larger than the measured modulus. (U.S.)