URANIUM EXTRACTION FROM NUCLEAR WASTES WITH A HIGH PRESSURE MIXTURE OF CO_2 AND TBP COMPLEX WITH NITRIC ACID

摘要

The solubility of TBP complex with HNO_3 and H_20 inrnsupercritical carbon dioxide (SF-CO_2) is very high and thernorganic solution whose composition is given asrn(HNO_3)I.s(H_20)0.6TBP is completely miscible in SF-CO_2 ifrnthe mixture is pressurized more than 13 MPa at 323 K.rnThe solubility of a mixture of UO_2(NO_3)2(TBP)2 and TBPrnin SF-CO_2 is also high and 0.5 molodm 3 UO_2(NO_3)2(TBP)2rnis miscible in SF-CO_2 if the mixture is pressurized morernthan 13 MPa at 323 K. Uranium was well extractablernfrom the solid matrices of UO_2 or U3Os with the highrnpressure solution of TBP-HNO_3- H_20-CO_2 at 323 K and 15rnMPa. The decontamination factor of UO_2 or U3Os wasrndetermined to be higher than 3x 10~2 for the decontaminationrnexperiments with using the simulated waste. The solidrnwaste after the supercritical fluid leaching treatment wasrnwell dry and contained enough low concentrations of TBPrnand HNO_3.