Investigation of the Phase Composition and Determination of the Oxygen to Metal Ratio of U–Pu­–Am Mixed Oxide Fuel

The phase composition and oxygen/metal ratio (O/M ratio, where М = U + Pu or U + Pu + Am) of experimental U–Pu and U–Pu–Am mixed oxide fuel samples obtained by co-electrocrystallization from alkali metal chloride melts were determined. The Pu content in the samples varied from 1.5 to 50 wt %, while the Am content varied within 1–5%. The phase composition was determined by X-ray powder diffraction, and the oxygen content was detected by gas coulometry. It was found that in most cases the crystallization products are two-phase mixtures formed on the ground of solid solutions of uranium and plutonium dioxides. It was established that the O/M ratio of selectively studied five samples was less than two (substoichiometric bulk composition). The set of data on the phase composition, crystal lattice parameters, and the appearance of the titration curves of gas-coulometric analysis indicate the possibility of the formation of single-phase mixed oxides of the type (U w Pu y Am z )O 2– x .