Process for the preparation of the heavy particles of oxides of the actinides and mixtures of oxides of the actinides can be used as fuel for nuclear reactors.

摘要

Dense particles of oxides of the actinide metals are prepared by forming a colloidal solution of the oxides of the metals, predominately in the tetravalent state, from an acid deficient solution (as defined below) of the nitrates of the actinide metals containing above 2 moles/l. of the metals and a molar ratio of nitrate: metals of 0.5-1.8: 1, subdividing the colloidal soln. into drops and gelling the drops by extraction of HNO3 therein by a liquid anionic exchanger (as defined below) contained in a water-immiscible solvent, and drying and calcining the gelled particles. Specified particles are of UO2, UO2/ThO2, UO2/PuO2 and ThO2/ PuO2. A liquid anionic exchanger is defined as a liquid capable of complexing with nitrate ions through a liquid/solid or a liquid/liquid interface, and exemplified exchangers are aliphatic primary amines and mixtures thereof. An acid deficient solution of the nitrate is a hydrolysed solution of the nitrate in which the equivalent nitrate concentration is less than the equivalent cation concentration, and may be formed from a solution of the nitrates by adding UO3 thereto, or by extraction of HNO3 therefrom by an anion exchanger. The colloidal solution may be formed by catalytic reduction of the solution of a nitrate of a hexavalent actinide in an autoclave with H2, in the presence of Al2O3 carrying one of the elements Pt, Pd, Os, Ru or Rh. The colloidal solution may be divided by spraying into the anionic exchanger or by emulsifying the solution in the exchanger by stirring.