Patent Number: 048225258
Section: summary

The present invention relates to a process for preparing a cartridge for disposal of a radioactive waste liquid. The cartridge is useful for the disposal of a radioactive waste liquid in such a manner that it is impregnated with the radioactive waste liquid, followed by heat-melting and solidification into glass. In the regeneration treatment at a regeneration plant of a used fuel from a nuclear reactor, a highly radioactive waste liquid containing uranium, transuranium elements and nuclear fission products, and nitric acid, is produced as a by-product. Under the circumstances, a technique for safely and efficiently disposing such a radioactive waste liquid, is desired. Heretofore, for the treatment of such a radioactive waste liquid, a technique has been developed wherein the radioactive waste liquid is directly, or after being denitrated and concentrated into a slurry, mixed with a glass material, then the mixture is supplied into a high temperature glass melting furnace wherein the liquid component in the waste liquid is evaporated and the radioactive substances are melted into glass, and the molten glass is poured into and solidified in a container made of steel. However, in such a conventional technique, the glass material was in the form of beads or powder, and a dust containing a substantial amount of radioactive substances, was likely to be generated when the waste liquid was vigorously boiled in the glass melting furnace, and such a dust was likely to be discharged together with the exhaust gas. For this reason, it was necessary to provide a dust-treating installation in the exhaust gas treating system, with considerably strict requirements. Further, it was likely that the piping lines were clogged by the dust. Furthermore, there was a possible danger that bricks in the furnace underwent cracking by thermal shock, and a part thereof fell off. Under the circumstances, in recent years, it has been proposed to use glass fibers as the glass material. It is advantageous to use glass fibers in that the waste liquid is impregnated in spaces between glass fibers, and a dust generated during the melting operation, is trapped by the filtering effect of the glass fibers and prevented from scattering. The present inventors have conducted extensive research to develop this technique for practical application, and have found it possible to obtain a cartridge for the disposal of a radioactive waste liquid, which is more suitable for the treatment of the radioactive waste liquid for glass solidification, by partially fusing the glass fibers and molding them into a block. A patent application (Japanese patent application No. 101902/1984) has been filed for an invention based on this discovery. However, it has been found that the above-mentioned cartridge for the disposal of a radioactive waste liquid, has a problem that a dust of glass fibers is generated when the glass fibers are sintered, and the dust is likely to deposit to cause clogging of the cartridge supply system. Further, the strength of the cartridge varies to a substantial degree depending upon the sintering conditions, and it is difficult to obtain cartridges having constant or uniform strength. It is an object of the present invention to provide a process for preparing a cartridge for disposal of a radioactive waste liquid, wherein glass fibers are partially fused and molded, whereby it is possible to prevent the generation of a dust of glass fibers and to obtain constant strength for cartridges. The present invention provides a process for preparing a cartridge for disposal of a radioactive waste liquid, which comprises filling glass fibers in a mold, heat-treating the fibers for partial fusion and molding them into a molded product of a predetermined shape, wherein at least one member selected from the group consisting of boric acid, silicic acid, lithium borate, lithium silicate, zinc borate, zinc silicate, an organic silane, an oil emulsion, and an alumina sol, is applied to the glass fibers or to the molded product. Now, the present invention will be described in detail with reference to the preferred embodiments.