An apparatus for thermally treating an organic material comprises: a rotatable drum (10) with a sealed inlet end and a sealed outlet end; a burner (24) attached to one of the covers for injecting a fuel and oxygen mixture into the drum (10) ; a conduit (28) extending through the inlet cover for feeding organic material(29) into the drum; a number of carriers (48) within the drum (10); a helical conduit (40) wound around the outside of the drum (10), which has an inlet end (42) near the drum outlet for receiving carriers from the drum outlet and an outlet end (46) near the drum inlet for conveying the carriers (48) to the drum inlet end, as the conduit (40) rotates with the drum (10); a device for moving the organic material and the carriers (48) from the drum inlet towards the drum outlet so that the movement of the carriers (48) moving with the organic material, helps mull the organic material and cleans the inside wall of the drum; a separator (44) located near the inlet end (42) of the helical conduit (40) for separating the carriers (48) from any remaining solid portions of the organic material and placing the carriers (48) in the conduit inlet (42); and conduits connected with an opening in the drum outlet to convey solids and gases from the outlet end of the drum. Also claimed is an apparatus for reducing the quantity of a solid organic material contaminated with a radioactive material.    USE -   For reducing a solid material containing organic components to a liquid or gas state by cracking the molecules by exposure to heat produced by a flame in the rotating drum.    ADVANTAGE -   Drum walls can be cooled by exposure to ambient conditions temperatures, preventing degradation of the material of the drum walls while allowing the use of higher temperatures within the drum. The carriers circulating inside the drum, cleans the inside of the drum and prevents clogging. Cracking of the organic material occurs in a sealed container and therefore minimises the oxidation of the material. Additionally, material contaminated by radioactive material is processed by converting the organic material to a gas, so reducing the quantity of solid radioactive material for further processing and disposal.