Interaction of uranium, ruthenium, tellurium, and palladium with rhenium

Compatibility of refractory metals and their alloys with metallic fission products has not been investigated in sufficient detail to design a high-temperature space power or propulsion reactor. Also, combinations of fission products and uranium generated by the dissociation of UN are available to react with the pin cladding. Consequently, the present study focuses on identifying phases and interactions of uranium and ruthenium with cladding alloys as well as on the interaction of volatile elements with ruthenium. A reevaluation of the Ru-U binary phase diagram is the primary focus. Experimental results and review of reported phase diagrams and data establish the following: (1) the ruthenium and URu3 eutectic solidus is at ∼1,870 K; (2) the liquidus temperature has a concave shape in the phase region between 0.75 and 1 mole fraction ruthenium; (3) tellurium and palladium liquids attack the rhenium grain boundaries and may cause compatibility problems in a reactor operated to high burnups and or high temperatures