Volatilization of Ruthenium, Caesium and Technetium from Nitrate Systems in Nuclear Fuel Processing and Waste Solidification

Abstract

Ruthenium volatilization measurements have been carried out on nitric acid and nitrate preparations during solution evaporation and subsequent thermal nitrate decomposition (calcination). Substantial volatilization commences in the final stages of evaporation, and proceeds throughout nitrate decomposition. In the latter, the volatilization correlates with nitrate pyrolysis. RU0 4 is probably the primary volatile species produced in an oxidizing environment, but is rapidly decomposed either to solid Ru0 2 or to condensed phase Ru(NO) compounds in liquid condensates.Caesium and technetium volatilization measurements under calcination and vitrification conditions show that the presence of Tc has a marked synergistic effect on Cs volatilization. The mole ratios of the volatilized elements suggest volatilization as a common compound such as CsTc0 4 .

Effect of Composition and Temperature on Volatilization of Cs from Borosilicate Glasses

“…Hence, it is necessary that the formation of Cs containing volatile species must be kept to a minimum during the vitrification process. Several studies are available regarding the extent of Cs volatilization during vitrification of high active nuclear waste . These studies have revealed that the composition of the glass, including the nature and concentrations of the constituents in the waste, play a major role in the extent of Cs volatility.…”

Study on valence of Pu, Np and Tc in nitric acid after electrolytic reduction

“…Ru is a complicated fission product elements in reprocessing system [9] and its nitrosyl nitrato complexes include numerous monocular, neutral, anionic and cationic species [10]. The presence of Ru(III) in nitric acid solutions accelerate the oxi- dation of Pu [11].…”

Radionuclides in the Geosphere: Sources, Mobility, Reactions in Natural Waters and Interactions with Solids

“…Mainly gaseous fission products and aerosols have been emitted, but solutions have also been given off. The most severe accident was that at Chernobyl in 1986 [48][49][50][51][52][53][54], Gaseous fission products and aerosols have been transported through the air over great distances [55]. Even molten particles from the reactor core ("hot particles") have been carried with the air over distances of several hundred kilometers.…”