The U-Pu-Zr metallic fuels contain multiple phases whose properties and distributions evolve due to factors such as fission, nuclear transmutation, and elemental redistribution under the influence of chemical and thermal gradients. An understanding of experimental data about phases, phase relationships, and phase properties in the U-Pu-Zr system is needed to enable mechanistic modeling of these phenomena and guide future research.

Although U-Pu-Zr alloys have been investigated for more than 60 years, relatively little reliable experimental information is available. Information about the technologically important alloy U-20Pu-10Zr (weight percent) is even more limited. The U-Pu-Zr alloys are difficult materials to study experimentally, and it is therefore important to understand what results have already been obtained, how reliable they are, and where they were reported.

This critical review provides a thorough compilation and critical assessment of the available experimental data involving properties of U-Pu-Zr phases, phase transitions, and phase diagrams, with particular attention to alloys with compositions close to U-20Pu-10Zr (weight percent). It is intended as a resource for fuel designers and modelers and a guide for prioritizing future experimental work.