Lattice thermal expansion of Pu_1−y Am _y O_2−x plutonium–americium mixed oxides

Abstract

Plutonium–americium mixed oxides, Pu1−yAmyO2−x, with various Am contents (y = 0.018, 0.077, 0.21, 0.49, 0.80 and 1.00) were studied in situ by high‐temperature X‐ray diffraction. In this study, the lattice thermal expansion of the six compounds subjected to heat treatments up to 1773 K under reconstituted air (N2 + 21% O2 + ∼5 vpm H2O) was investigated. The materials remained monophasic throughout the experiments and, depending upon the americium content, the lattice parameter of the face‐centred cubic phase deviated from linear lattice expansion at elevated temperatures as a result of the progressive reduction of Am4+ to Am3+.

Electron correlation and relativistic effects on the electronic properties of a plutonium and americium mixed oxide (PuAmO4): from single-particle approximation to dynamical mean-field theory

“…Meanwhile, as listed in Fig. 1, the admixture of 5f 4 , 5f 5 and 5f 6 configurations yields the fractional occupation number of 5f electrons for Pu ions, while it involves 5f 5 and 5f 6 configurations for Am ions. 21,38 These many-body multiplets are responsible for the complicated multiple structures as illustrated in Fig.…”

New sample stage for characterizing radioactive materials by X-ray powder diffraction: application on five actinide dioxides ThO2, UO2, NpO2, PuO2 and AmO2

“…In some materials, the structural damage generated by decay can lead to a complete amorphization of the material (Walter et al, 2007;Vigier et al, 2019). Furthermore, the self-irradiation generally induces a significant lattice swelling over time (Turcotte, 1976;Weber, 1984;Baclet et al, 2007;Thiebaut et al, 2007;Ravat et al, 2007;Nishi et al, 2013;Lebreton et al, 2014, (Baena et al, 2015) 5.47127 ( 8) (Leinders et al, 2015) 5.434 (1) (Chollet et al, 2014(Chollet et al, , 2012 5.39819 (1) (Belin et al, 2004) 5.3755 ( 5) (Vauchy et al, 2017) 5.593 (3) (Horlait et al, 2012) 5.4702 (4) (Yamashita et al, 1997) 5.4338 (3) (Yamashita et al, 1997) 5.3954 (4) (Yamashita et al, 1997) 5.375 (1) (Epifano et al, 2017(Epifano et al, , 2016 5.5974 (6) (Yamashita et al, 1997) 5.470 (Markin & Street, 1967) 5.4328 (2) (Fahey et al, 1974) 5.3953 (4) (Noe & Fuger, 1974) 5.3733 (Fahey et al, 1974) 5.5972 (5) (Zachariasen, 1948) 5.4704 (1) (Baldock et al, 1966) 5.434 (Sudakov et al, 1973) 5.3960 (3) (Ellinger, 1961) 5.377 (3) (Zachariasen, 1949) Figure 12 Experimental lattice parameters of the fluorite structure of ThO 2 , UO 2 , NpO 2 , PuO 2 and AmO 2 obtained in this study compared with the values in the literature from Table 2. 2016; Vigier et al, 2018).…”

“…Finally, a decrease in the oxygen stoichiometry also leads to an increase in the lattice parameter of the f.c.c. structure of the actinide dioxides (Markin & Street, 1967;Vauchy et al, 2015Vauchy et al, , 2017Vauchy, Belin, Robisson et al, 2016;Epifano et al, 2016Epifano et al, , 2017. As mentioned in Section 3.1, no annealing was performed on the samples prior to the measurements so neither the accumulated lattice defects due to self-irradiation nor the oxygen stoichiometry were restored.…”

Computational Study of Plutonium–Americium Mixed Oxides (Pu0.92Am0.08O2–x); Water Adsorption on {111}, {110}, and {100} Surfaces

“…Although Pu and Am are neighbors in the periodic table, a higher oxygen equilibrium potential has been found for americium dioxide than PuO 2 , which reflects the different reducibility of Am 4+ and Pu 4+ . 7,8 Water adsorption behavior on AmO 2 and PuO 2 surfaces is also different. 5,9,10 Thus, the existence of Am in PuO 2 will influence the valence states of Pu ions, water adsorption on its surfaces and, potentially, the way the material interacts with other gaseous species.…”

“…15 Miwa et al reported that Pu 0.91 Am 0.09 O 2 has a single-phase fluorite structure and the microstructure is homogeneous. 13 Pu-Am MOX with various Am contents (Am to metal ratio = 0.018, 0.077, 0.21, 0.49, 0.80 and 1.00) were studied by Vaych et al; 8 regardless of the Am content, all the samples remain single phased, facecentered cubic (f.c.c.) fluorite.…”