In-situ X-ray diffraction study of phase transformations in the Am–O system

Application of the UMACS process to highly dense U1−xAmxO2±δ MABB fuel fabrication for the DIAMINO irradiation

“…After cooling, this thermal treatment allows U 1Àx Am x O 2±d pellets exhibiting a nearly-monophasic structure to be obtained, corresponding to a homogeneous Am repartition. Under such experimental conditions, Am +IV is fully reduced to Am +III , while U +IV is partially oxidized to U +V [14,15], leading to the achievement of a stable (U +IV ,U +V ) 1Àx Am +III…”

Dilatometric Study of U1−xAmxO2±δ Sintering: Determination of Activation Energy

“…Based on these results, a 4‐h heat treatment at 2023 K was used to synthesize the U 1− x Am x O 2±δ solid solution. It was carried out in an all‐tungsten furnace under an Ar/H 2 (2%)/H 2 O(50 ppm) atmosphere, H 2 O being added to prevent americium sublimation …”

“…In terms of fabrication, one of the key issues is to take into account characteristics of both americium and uranium oxides. More specifically, americium oxides have higher oxygen potential than uranium or plutonium oxides and thus require more attention to prevent americium reduction to overly reduced states, or even to metallic state . It was also shown that sintering under over‐stoichiometric conditions (i.e., under a neutral atmosphere), which is suitable for preparing UO 2+δ dense fuels was not applicable to U 1− x Am x O 2±δ reactive sintering, as low‐density, heterogeneous and warped pellets were obtained …”

The Separation of 241Am from Aged Plutonium Dioxide for use in Radioisotope Power Systems

“…When making ceramic pellets the chemical behaviour of americium oxides needs consideration. It is well documented that americium dioxide loses oxygen when heated to beyond 800°C to form an oxide with a lower oxygen to americium ratio AmO2-x (where x = 0 -0.5) and can occur at even lower temperatures in a reducing atmosphere [11,12]. This is an important safety consideration because in launch accident scenarios it is possible for the heat source material to reach high temperatures (< 1800°C).…”

“…x The changes in phases from face centred cubic (fcc) AmO2 phase to body centred cubic (bcc) Am2O3+y phase to hexagonal Am2O3 phase may result in stresses within the material as the pellet heats, loses oxygen and cools down [12].…”