Solidification processing method for radioactive waste

The pressure in a vessel containing radioactive wastes is previously reduced and cement mortar prepared by kneading cement, sand and kneading agent with water is poured under shaking substantially to the upper end of the vessel. After the lowering of the mortar level due to the deforming has been terminated, the pressure is increased gradually. Then, the cement mortar is further poured substantially to the upper end of the vessel again. With such a two step pouring method, spaces other than the radioactive wastes in the vessel can be filled substantially completely with the cement mortar. Accordingly, it is possible to avoid the problem in view of the strength due to the formation of gaps at the inside of the vessel, or leaching of radioactive materials due to the intrusion of water into the gaps. Further, if washing water is reutilized as water for kneading or washing after the precipitation of the solid contents, the amount of the secondary wastes generated can be reduced. (T.M.)