No abstract

The formation of sulfate complexes of Curium in aqueous solutions is studied by time resolved laser fluorescence spectroscopy (TRLFS) at 25 °C. The species Cm", Cm(S0 4 )\ Cm(S0 4 )ï and Cm(S0 4 )5~ are quantified spectroscopically in the trace concentration range by peak deconvolution of fluorescence emission spectra. The complex formation equilibria are measured in NaCl/ Na 2 S0 4 solutions of constant ionic strength (3 molai) as a function of the sulfate concentration. The stability constants of Cm(S0 4 ) + and Cm(S0 4 )j are determined to be log β, = 0.93±0.08 and \ogß 2 = 0.61 ±0.08, respectively. The complex Cm(S0 4 )iS" is found to be stable only at very high sulfate concentrations (above 1 molai) and therefore not considered for further evaluation.

Actinide molten salts represent a class of important materials in nuclear energy. Understanding them at a molecular level is critical for the proper and optimal design of relevant technological applications. Yet, owing to the complexity of electronic structure due to the 5f orbitals, computational studies of heavy elements in condensed phases using ab initio potentials to study the structure and dynamics of these elements embedded in molten salts are difficult. This lack of efficient computational protocols makes it difficult to obtain information on properties that require extensive statistical sampling like transport properties. To tackle this problem, we adopted a machine-learning approach to study ThCl 4 −NaCl and UCl 3 −NaCl binary systems. The machine-learning potential with the density functional theory accuracy allows us to obtain long molecular dynamics trajectories (ns) for large systems (10 3 atoms) at a considerably low computing cost, thereby efficiently gaining information about their bonding structures, thermodynamics, and dynamics at a range of temperatures. We observed a considerable change in the coordination environments of actinide elements and their characteristic coordination sphere lifetime. Our study also suggests that actinides in molten salts may not follow well-known entropyscaling laws.

No abstract

No abstract