[en] A large quantity and various level of radioactive waste is arisen due to nuclear power plant decommissioning. Minimizing radioactive waste is, therefore, vital in reducing the burden to the radioactive waste disposal site capacity. The authors have developed a technique to fill low level radioactive molten metal as filler in thin waste disposal containers. This is termed the 'radioactive metal casting process for thin container'. Demonstration tests using actual scale containers consist of 3 themes, i.e., conditions to properly fill molten metal in the container with pre-placed metal, thinning container material with support of heat removal blocks, and metal impurity limit mixed in raw waste metal. As a result, it was demonstrated that the casting process can achieve a good fill ratio with no harmful loss to the pre-placed metal and no harmful distortion to the container or shielding layer, when the filler metal was poured into the container with a proper layout of heat removal blocks at the proper temperature. (author)