Alkali metal actinide complex halides : thermochemical and structural considerations

Abstract

HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. Résumé. -L'auteur passe en revue l'état actuel de nos connaissances dans le domaine de la thermodynamique des complexes halogènes d'actinides avec les ions alcalins, en portant une attention toute spéciale aux dérivés chlorés et bromes. Lorsque les données thermodynamiques et structurales sont accessibles, il tente de déduire l'évolution de l'énergie de la liaison actinide-halogène au sein d'une série de composés isomorphes ou analogues. Enfin, la variation énergétique au cours de la formation du complexe halogène à partir des halogénures binaires d'actinides et de métaux alcalins est prise pour base en vue de prévoir la stabilité de composés nouveaux, spécialement ceux pour lesquels l'halogénure binaire d'actinide n'a pas été préparé ou est de faible stabilité. Diverses méthodes de préparation sont évoquées.Abstract. -The present status of our information on the thermodynamics of the actinide halogeno-complexes with alkali metal ions is reviewed, with special emphasis on chloro-and bromo-derivatives.Where enough thermodynamic and structural data are available, attempts are made to deduce the evolution of the energetics of the actinide-halogen bonds along a series of isomorphous or analogous compounds. The energy change upon the formation of the halogeno-complexes from binary actinide halides and alkali metal halides is discussed with the aim of predicting the stability of new compounds, especially those for which the corresponding binary actinide halides have not been characterized or are of low stabilities. Possible preparative routes for such compounds are also outlined.

Investigating the hydrolysis of cryogenically layered molybdenum hexafluoride through a disordered hydrogen-bonded network

“…As a result of the common use of UF 6 in uranium enrichment since the 1940s, the chemical processing of UF 6 has been highly studied and is well understood. 1–8 However, uranium enrichment is carried-out under controlled conditions to limit moisture in the process to prevent loss of uranium to more thermodynamically favorable reactions which produce solids (material holdup). When UF 6 is exposed to atmosphere, it readily undergoes the hydrolysis reaction UF 6 (g) + 2H 2 O(g) → UO 2 F 2 (s) + 4HF(g).…”

A theoretical investigation of the hydrolysis of uranium hexafluoride: the initiation mechanism and vibrational spectroscopy

“…2 Since then, a significant amount of knowledge has been gained regarding the chemical processing of UF 6 . 3–11…”