Method for the selective separation of uranium and protactinium from thorium-containing material

摘要

The subject of the invention is the way of selective separation of uranium and protactinium from irradiated in a nuclear reactor materials containing thorium. The method of selective extraction of uranium and protactinium from materials containing thorium, especially separating micro-amounts of uranium and protactinium from macro-amounts of other components containing thorium, especially ThO 2 , consists in dissolving a sample containing U, Th and Pa using a mixture of nitric acid, hydrofluoric acid and Al(NO 3 ) 3 in a hermetically closed vessel, made of polytetrafluoroethylene or derivatives of Teflon (PTFE, PFA). Next, the vessel is closed and heated in the temperature of 40-120°C for minimum 1 hour, after which the obtained clear solution is put onto a chromatographic column, filled with trioctylphosphine oxide (TOPO) adsorbed on a hydrophobic sorbent, favourably polystyrene-divinylbenzene, and elution is conducted, favourably of 50 ml solution which is a mixture of nitric and hydrofluoric acids with an addition of aluminium nitrate (favourably THOREX) at the pace of 0.2-10 mL/300 s, while at the column, 233 Pa is quantitatively retained and the effluent from the column which contains Th and U is quantitatively moved to a vessel made of polytetrafluoroethylene or its analogues (PTFE or PFA) and evaporated to the volume of 0.5-5mL. Next, we add 0.5-5mL of H 2 O, and next, the obtained solution is put onto the column, filled with quaternary aliphatic amine and conduct an elution with a solution which is a mixture of nitric and hydrofluoric acids with an addition of aluminium nitrate with H 2 O, at the eluent flow rate of 0.2-10 mL/300 s, collecting fractions of volumes of 0.1-10mL, selectively separating U and Th. Uranium is eluted quantitatively in first five fractions, favourably four fractions (v=10 mL) and next, Thorium in fraction 7-25 (v=39 mL).