SUPERCRITICAL CO_2 FLUID LEACHING (SFL) OF URANIUM FROM SOLID WASTES USING HNO_3-TBP COMPLEX AS A REACTANT

摘要

A new method, which is based on the efficient and selective dissolution of uranium oxides with supercritical CO_2 containing HNO_3-tributylphosphate (TBP) complex and is referred to as supercritical CO_2 fluid leaching (SFL) method, has been developed for the removal of uranium from the solid waste contaminated by uranium oxides. It was found that uranium oxides, UO_2 or U_3O_8, could be dissolved almost completely in supercritical CO_2 phase at 60°C and 20 MPa. The feasibility of the SFL method for the decontamination of uranium from the solid wastes was demonstrated using a synthetic waste, i. e., a mixture of the standard sea sand (ca. 50 g) and UO_2 or U_3O_8 powders (ca. 100 mg of U). The decontamination factor of UO_2 or U_3O_8 of 10~2 or 10~4, respectively, were attained by the recommended procedure.