Thermal conversion of wastes

A process is described for the thermal conversion of a radioactive waste material which comprises the sequential steps of: introducing the radioactive waste material in the form of a finely atomized spray into the top of a spray dryer zone heated, by means of a hot gas produced externally of the zone on combustion of a fuel and air and introduced into the top of the zone, to a temperature of about 5000 to 10000C to convert the radioactive waste material, by contact with the hot gas, into a mixture of products including a non-radioactive gas comprising gaseous H/sub 2/O, CO/sub 2/ and nitrogen and a radioactive inorganic ash; removing the mixture of products from the bottom of the zone, and separating the radioactive inorganic ash from the mixture of products, the ratio of the volume of the radioactive waste material to the volume of the ash being in the range of about 7:1 to 70:1