Abstract
The gas-phase conversion of U3O8, MoO3, SrO, and their mechanical mixtures, and also of ZrO2 into water-soluble compounds in the atmosphere of (NOx + vapor H2O) or HNO3 (vapor) was studied. In the course of gas-phase conversion, U3O8 and SrO transform into water-soluble compounds (nitrates, hydroxonitrates), whereas MoO3 and ZrO2 undergo no changes. The principal possibility of separating U from Mo and Zr by gas-phase conversion of the oxides in the atmosphere of (NOx + vapor H2O) or HNO3 (vapor) was demonstrated.
Highlights
The current plans calling for the transition to fast-neutron reactors, as well as to reactors with a high fuel burnup have stimulated an active search of spent nuclear fuel (SNF) reprocessing techniques that would be alternative to the classical Purex process
The gas-phase conversion of U3O8 with the formation of water-soluble compounds in nitrating atmosphere can be described by the following reaction equations: U3O8 + 6NO2 + 2O2 + 3nH2O = 3UO2(NO3)2·nH2O (n = 0, 1, 3 or 6)
It is necessary noted that TG curves for uranyl nitrate and products of U3O8 in nitrating atmosphere have a similar course
Summary
The current plans calling for the transition to fast-neutron reactors, as well as to reactors with a high fuel burnup have stimulated an active search of spent nuclear fuel (SNF) reprocessing techniques that would be alternative to the classical Purex process. One of the promising technologies of short-cooled SNF reprocessing is voloxidation (volume oxidation) of both SNF and zircalloy fuel cladding, followed by treatment of voloxidation products in the atmosphere of NOx gases. Voloxidation allows volatile components (3H, 14C, 129I, radioactive noble gases) to be removed before starting the radiochemical reprocessing of the fuel; in addition, strong zirconium fuel claddings transform into ZrO2 [1], and UO2 transforms into U3O8. This treatment does not eliminate regular problems with colloid formation in the step of SNF dissolution in HNO3. It seems more promising that the oxidative recrystallization be followed not by the dissolution of SNF voloxidation products and fuel rods in nitric acid, but by their treatment with nitrogen oxides to obtain weakly hydrated water-soluble uranium compounds
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