Solidus and liquidus temperatures in the uranium-plutonium-zirconium system

Renewed interest in metallic fuel for nuclear reactors has prompted study of the solidus and liquidus for the uranium-plutonium-zirconium system. These temperatures are of importance in assessing the possibility of fuel melting during abnormal reactor conditions. Data obtained in previous work in this area were found to be inadequate for the needs of the current reactor development effort. A dual effort was undertaken to provide the needed data. These were (1) thermodynamic phase diagram analysis and calculation of the ternary solidus and liquidus surfaces and (2) experimental determination of solidus and liquidus temperatures for selected alloys. The methods used and results obtained are described.