Thermodynamic activity measurements of U-Zr alloys by knudsen effusion mass spectrometry

Abstract

Vaporization of a series of U-Zr alloys, a fundamental subsystem of the promising metallic fuel U-Pu-Zr, was studied by using a tantalum Knudsen cell coupled with a mass spectrometer in the temperature range 1700–2060 K. Thermodynamic activities, partial molar Gibbs free energies and integral molar Gibbs free energies of mixing were calculated from the partial vapor pressures of uranium over these alloys. The activities of uranium exhibit negative deviations from ideality, especially in the uranium-rich composition region. Both the solidus and liquidus lines for this system estimated from the activities show negative deviations from the tentative phase diagram previously reported.