Americium incorporation into studtite: a theoretical and experimental study

Abstract

Reactions of [AmO2]+ with [UO2(η2-O2)(H2O)2]·2H2O have been examined and the Am is reduced to Am(iii). Leaching experiments show that Am(iii) can be easily removed and a computational study sheds light on the mechanism and incorporation energies.

Tilting and Distortion in Rutile-Related Mixed Metal Ternary Uranium Oxides: A Structural, Spectroscopic, and Theoretical Investigation

“…First, Hubbard U parameters were computed for the d elements and uranium in the five A UO 4 oxides. These values, given in Table , are consistent with the parameters derived in previous studies of U 6+ compounds. ,,,, The DFT+ U calculations found the Cmmm structure to be the most stable for all five A UO 4 oxides, consistent with the calculations using the VASP code. At first sight, this disagreement with the experimental results for A UO 4 with A = Mn, Co, Mg, and β-Ni could be seen as a failure of the computational model.…”

“…However, the spatial extent of the 5f orbitals, strong spin–orbit coupling, complex occupations, and exotic bonding characteristics of actinide elements limit the application and reliability of certain computational codes. , A typical solution to this challenge is coupling computational methods with high-precision experimental studies of model systems, allowing for computational models to be improved and benchmarked. Such synergistic approaches have been well demonstrated for a variety of actinide materials including simple solid solutions. , Notwithstanding this, a paucity of information remains particularly for more complex actinide materials in which mixing of s-, d-, and f-block elements is encountered, for example, in fuel-cladding interaction products. Consequently, there is an inherent need to systematically examine such compounds to establish their fundamental chemistries and also the limitations of computational codes so that they can be reliably applied to other, more challenging, actinide systems.…”

Research for the Safe Management of Nuclear Waste at Forschungszentrum Jülich: Materials Chemistry and Solid Solution Aspects

“…[16][17][18][19] It was found that this approach significantly improves the prediction of structural and thermodynamic parameters of lanthanide phosphates and actinide-bearing molecular and solid compounds. [17,19,20] This method has been applied also to explain various properties and parameters of materials, such as their structural [17,21] and thermodynamic parameters, [22] their relative stability, [23,24] their electronic structure and X-ray absorption near edge structure (XANES) signatures, [25] and their defect formation energies. [26,27] It was also applied to derive reliable force fields for large-scale simulations of radiation damage processes [28] and to test the performance of different computational approaches for d and f electrons, [20] including advanced methodologies for computing solid solutions.…”

Modeling of Nuclear Waste Forms: State-of-the-Art and Perspectives

“…We used atomistic modeling to interpret the HERFD spectra and validate the structural models of the two phases, including the local U environments [38]. In recent follow-up studies, we computed incorporation energies of Np and Am into both phases [39]. The most energetically favorable oxidation states and their solution energies are reported in Table 2.…”

“…The Np and Am incorporation energies (in eV) into studtite and metastudtite peroxides. Data from Biswas et al[39].…”