there is provided a process for the production of spherical fuel and / or fertile oxide or carbide particles for a nuclear reactor , especially a high temperature reactor , by casting an aqueous solution of a uranium and / or a thorium and / or plutonium salt , as well as in the case of the production of carbide particles finely dispersed carbon also , from a vibrating nozzle , passing the drops formed through an ammonia containing gas zone into an ammoniacal precipitation bath with subsequent washing , drying and sintering or melting . to the aqueous solution there is added individually or in admixture a water soluble or water miscible monomeric hydrocarbon having an aldehyde , keto , ether , amino , imino , phenol , carboxylic acid or carboxylic acid amide group , which substituted hydrocarbons form stable adducts with uranium , thorium and plutonium in aqueous alkaline solution , which adducts cannot be washed out with water and which does not impart to the solution a viscosity of over 15 cp at 20 ° c .