Removal of uranium by an alkalization and acidification from the thermal decomposed solid waste of uranium bearing sludge

This study has been carried out to elucidate the characteristics of the dissolution for Thermal Decomposed Solid Waste of uranium-bearing sludge (TDSW), the removal of impurities by an alkalization in anitric acid dissolving solution of TDSW, and the selective removal (/recovery) of uranium by an acidification in an carbonate alkali solution, respectively. TDSW generated by thermal decomposition of U bearing sludge which was produced in the uranium conversion plant operation, was stored in KAERI as a solid-powder type. It is found that the dissolution of Tds is more effective in nitric acid dissolution than oxidative-dissolution with carbonate. At 1 M nitric acid solution, TDSW was undissolved about 30wt% as a solid residue, and uranium contained in TDSW was dissolved more than 99%. In order to the alkalization for the nitric acid dissolving solution of TDSW, carbonate alkalization is more effective with respect to remove the impurities. At the carbonate alkali solution controlled to about 9 of pH, Al,Ca, Fe and Zn co-dissolved with U in dissolution step was removed about 98±1%. On the other hand, U could be recovered more than 99% by an acidification at pH about 3 in a carbonate alkali solution, which was nearly removed the impurities, adding 0.5M H₂O₂. It was found that uranium could be selectively recovered (/removed) from TDSW.