Chemistry of volatile oxygen-bearing compounds formed by U, Np, Pu, Am and Cm

Vladimir Panteleimonovich Domanov

doi:10.21767/2472-1123-C1-021

Chemistry of volatile oxygen-bearing compounds formed by U, Np, Pu, Am and Cm

2^nd Edition of EuroSciCon Conference on Chemistry
February 19-20, 2019 | Prague, Czech Republic

Vladimir Panteleimonovich Domanov

Joint Institute for Nuclear Research, Russia

Posters & Accepted Abstracts: J Org Inorg Chem

DOI: 10.21767/2472-1123-C1-021

Abstract

Tracer-scale chemistry has some distinguishing characteristics which makes it differ from common (macro) chemistry. For example, the common redox and self-redox reactions 2Pu(IV)+U(IV)â�?�?>2Pu(III)+U(VI) and 2U(V)â�?�?>U(VI)+U(IV) that do not occur in extremely diluted solutions as collisions between micro components are practically excluded. Considerable differences in the chemical behaviour micro- and macro quantities of some actinides in the gaseous phase had also been observed. The initial sample contains a tracer quantity of the actinide under study that was adsorbed on the surface of quartz powder. The experiments were carried out using open quartz thermochromatographic (TC) columns (id=3 mm); oxygen served as a reagent and helium was a carrier gas; the flow rate of the gas mixture was 20 cm3 min–1; the initial sample was heated in a gas stream at 700-750 �?�?C and the final temperature was –165 �?�?C; the temperature gradient was –18 �?�?C cm^-1; the duration of each experiment was 30 min. It was found that uranium formed volatile dioxide and trioxide that were adsorbed at 450±25 �?�?C and 250±25 �?�?C. The values of adsorption enthalpy -ΔHao for UO₂ and UO₃ on quartz were 172±6 and 126±6 kJ mol-1 respectively. Two plutonium radioisotopes 238,239Pu were used in similar experiments. Contrary to the previous results, plutonium formed three oxides. The centres of their deposition zones were registered at 450±30�?�?C (PuO2), 250±30 �?�?C (PuO₃) and at negative temperature –105±25 �?�?C (PuO₄). The values of -ΔHao for these oxides were 175±7, 122±7 and 47±6 kJ mol^-1 respectively. Results of the TC isolation of neptunium, americium and curium oxides are also presented. In particularly, Cm formed also three oxides: CmO₂, CmO₃ and CmO₄.