[en] Flame retardant solid wastes are filled in a vessel such as a drum can and compressed to form compression products with the volume being reduced to one-to-several fractions. Then, the compression products are applied with heat treatment by a heating device having an electric heater, etc. It is preferable that the heating temperature is set within such a range as higher than the softening temperature capable of softening rubber, etc. in the compression products thereby reducing the recoiling force and lower than the temperature not evolving deleterious gases such as chlorine gas by heat decomposition. For instance, about 200 to 400 degC of temperature is desirable for rubber. Then, after charging a plurality of compression products removed with internal recoilling force by the heat treatment into a storing vessel such as a drum can, settling material such as mortar is charged between the outer circumferential surface of the compression products and the inner circumferential surface of the vessel by means of a charging machine and the entire portion is solidified into materials to be wasted. Thus, it is possible to prevent the worry that cracks are caused in the settling material by the spring back of the compression products after burying disposal, to expose solid wastes to the outside, without impairing the volume-reduction property. (Y.Y.)

[en] 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.)