title: Biphasic MO2+x-M3O8-z domain of the U-Pu-O phase diagram.
abstract: The reduction of six mixed-oxide samples containing 14, 24, 35, 46, 54, and 62 mol % Pu was studied in situ by X-ray diffraction. The samples were first oxidized in air and subsequently reduced in a controlled atmosphere corresponding to a stoichiometric composition with an O/M = 2.00. After oxidation, we observed two structures, one cubic and one orthorhombic, MO2+x and M3O8-z. The two phases were subsequently reduced back to their stoichiometric O/M = 2.00 in a controlled atmosphere. The plutonium contents of the two resulting cubic structures differed from the initial one. We conclude that strong cation transport took place during oxidation, according to the shape of the tie lines in the biphasic MO2+x/M4O9-M3O8-z domain. The resulting overall O/M after oxidation was estimated. We propose the shape of the tie lines in the aforementioned biphasic domain and suggest a maximal plutonium solubility in the M3O8 structure at 8 ± 2 mol % (Pu/U + Pu) at 1573 K.
authors.affiliation: CEA, DEN, DTEC, SECA, LCC, Cadarache F-13108 Saint-Paul-Lez-Durance, France.|IM2NP, UMR 6122, CNRS, Aix Marseille University , Case 251, Avenue Escadrille Normandie Niemen, 13397 Marseille Cedex 20, France.
authors.forename: Michal
authors.initials: M
authors.lastname: Strach
authors.affiliation: CEA, DEN, DTEC, SECA, LCC, Cadarache F-13108 Saint-Paul-Lez-Durance, France.
authors.forename: Renaud C
authors.initials: RC
authors.lastname: Belin
authors.affiliation: CEA, DEN, DTEC, SECA, LCC, Cadarache F-13108 Saint-Paul-Lez-Durance, France.
authors.forename: Jean-Christophe
authors.initials: JC
authors.lastname: Richaud
authors.affiliation: IM2NP, UMR 6122, CNRS, Aix Marseille University , Case 251, Avenue Escadrille Normandie Niemen, 13397 Marseille Cedex 20, France.
authors.forename: Jacques
authors.initials: J
authors.lastname: Rogez