title: Multiscale structural characterizations of mixed U(iv)-An(iii) oxalates (An(iii) = Pu or Am) combining XAS and XRD measurements.
abstract: Mixed actinide(III,IV) oxalates of the general formula M2.2UAn(C2O4)5·nH2O (An = Pu or Am and M = H3O(+) and N2H5(+)) have been quantitatively precipitated by oxalic precipitation in nitric acid medium (yield >99%). Thorough multiscale structural characterization using XRD and XAS measurements confirmed the existence of mixed actinide oxalate solid solutions. The XANES analysis confirmed that the oxidation states of the metallic cations, tetravalent for uranium and trivalent for plutonium and americium, are maintained during the precipitation step. EXAFS measurements show that the local environments around U(+IV), Pu(+III) and Am(+III) are comparable, and the actinides are surrounded by ten oxygen atoms from five bidentate oxalate anions. The mean metal-oxygen distances obtained by XAS measurements are in agreement with those calculated from XRD lattice parameters.
authors.affiliation: CEA, DEN, DRCP, SERA/ Laboratoire de Conversion des Actinides et Radiolyse, BP 17171, F-30207 Bagnols sur Cèze Cedex, France. benedicte.arab-chapelet@cea.fr.
authors.forename: B
authors.initials: B
authors.lastname: Arab-Chapelet
authors.affiliation: CEA, DEN, DEC, 13108 St Paul Lez Durance, France.
authors.forename: P M
authors.initials: PM
authors.lastname: Martin
authors.affiliation: CEA, DEN, DRCP, SERA/ Laboratoire de Conversion des Actinides et Radiolyse, BP 17171, F-30207 Bagnols sur Cèze Cedex, France. benedicte.arab-chapelet@cea.fr.
authors.forename: S
authors.initials: S
authors.lastname: Costenoble
authors.affiliation: CEA, DEN, DRCP, SERA/ Laboratoire de Conversion des Actinides et Radiolyse, BP 17171, F-30207 Bagnols sur Cèze Cedex, France. benedicte.arab-chapelet@cea.fr.
authors.forename: T
authors.initials: T
authors.lastname: Delahaye
authors.affiliation: Helmholtz-Zentrum Dresden-Rossendorf, Institute of Resource Ecology, D-01314 Dresden, Germany.
authors.forename: A C
authors.initials: AC
authors.lastname: Scheinost
authors.affiliation: CEA, DEN, DRCP, SERA/ Laboratoire de Conversion des Actinides et Radiolyse, BP 17171, F-30207 Bagnols sur Cèze Cedex, France. benedicte.arab-chapelet@cea.fr.
authors.forename: S
authors.initials: S
authors.lastname: Grandjean
authors.affiliation: Univ. Lille Nord de France, Unité de Catalyse et de Chimie du Solide, UCCS, UMR CNRS 8181, ENSCL-USTL, BP 90108, 59652 Villeneuve d'Ascq Cedex, France.
authors.forename: F
authors.initials: F
authors.lastname: Abraham