Abstract: A method of recovering palladium from a palladium-containing aqueous solution by electrolysis is provided. The method comprises the steps of dc-electrolyzing the palladium-containing aqueous solution acidified with nitric acid by using an electrolytic cell equipped with a platinum electrode as a cathode to thereby deposit and collect palladium on the cathode, taking the cathode on which palladium has been deposited and collected out of the electrolytic cell, transferring the palladium-deposited cathode to a recovery vessel containing dilute nitric acid therein, and mechanically shaking the cathode in the recovery vessel to remove and recover palladium from the cathode. An apparatus for carrying out the above-described method is also provided.

Abstract: A method of treatment of a high-level radioactive waste comprising heating the radioactive waste at a high temperature of about 500.degree. to 3000.degree. C. to vaporize part of the elements contained in the radioactive waste, and cooling the resultant vapor to separately collect the elements. In one embodiment, the heating step is replaced by a reduction-heating step wherein heating is carried out in the presence of a reducing agent, e.g. hydrogen. In another embodiment, the heating step may be followed by the reduction-heating step.

Abstract: A method of treatment of a high-level radioactive waste containing platinum group elements is provided in which boron and a boron compound is added to a calcined material of the high-level radioactive waste in an amount of 0.5 to 10% by weight in terms of boron as a simple substance, and the resultant mixture is heated at a temperature of about 1000.degree. C. or above under a reduction condition to melt the mixture and to alloy the platinum group elements present in the calcined material with boron. A layer of the resultant platinum group element alloys is then separated and recovered from a layer of residual oxides through sedimentation. The layer of the residual oxides is solidified to form a highly volume-reduced high-level radioactive solidified waste.