초록 ▼

A concrete pit containing radioactive waste is surrounded by a low diffusion layer of cement-based material, which in turn, is surrounded by a low water permeability layer of sodium-type bentonite and the leaching out of calcium ions from the low water permeability layer is inhibited by mixing sodiu

A concrete pit containing radioactive waste is surrounded by a low diffusion layer of cement-based material, which in turn, is surrounded by a low water permeability layer of sodium-type bentonite and the leaching out of calcium ions from the low water permeability layer is inhibited by mixing sodium bicarbonate or sodium carbonate with the sodium-type bentonite/sand mixture of the low water-permeability layer so that leached calcium ions form a barrier layer having calcium carbonate as the main component in the vicinity of the interface between the layers.

대표청구항 ▼

1. An artificial multi-barrier for a radioactive waste treatment facility wherein a low diffusion layer consisting of cement-based material is arranged on the outside of a concrete pit housing radioactive waste, and a low water-permeability layer provided in the form of a compacted layer consisting

1. An artificial multi-barrier for a radioactive waste treatment facility wherein a low diffusion layer consisting of cement-based material is arranged on the outside of a concrete pit housing radioactive waste, and a low water-permeability layer provided in the form of a compacted layer consisting of a mixture of sodium-type bentonite and sand at 10 to 70% by weight of said bentonite, said sand having a grain diameter of maximally 1.2 mm or less and further containing sodium bicarbonate or sodium carbonate so as to obtain a dry density of 1.6 g/cm3 or above and permeability of 1.0×10−12-m/s or below is arranged in contact with the outside of said low diffusion layer, said artificial multi-barrier being characterized by providing mixing the sodium bicarbonate or sodium carbonate with constituents of said low water-permeability layer so that in case of the leaching-out of calcium ions from the cement-based material of said low diffusion layer, said calcium ions are made to react with the sodium bicarbonate or sodium carbonate mixed with the constituents of said low water-permeability layer so that a calcium ion-diffusion barrier layer having calcium carbonate as its main component is formed in the vicinity of the interface between said low diffusion layer and said low water-permeability layer, wherein a back-filling layer consisting of refilling material having excavated earth and sand as its main component and permitting cement to be held therein is arranged in contact with the outside of said low water-permeability layer so that in case of the leaching-out of calcium ions from said back-filling layer, said calcium ions are made to react with the sodium bicarbonate or sodium carbonate mixed with the constituents of said low water-permeability layer so that a barrier layer having calcium carbonate as its main component is formed also in the vicinity of the interface between said low water-permeability layer and said back-filling layer, and wherein only a layer of said low water-permeability layer in the vicinity of the interface between said low water-permeability layer and said low diffusion layer and/or said back-filling layer comprises sodium bicarbonate or sodium carbonate of a high concentration or supersaturation concentration, while an inner layer or layers thereof comprises no sodium bicarbonate or sodium carbonate or otherwise have it of a lower concentration. 2. The artificial multi-barrier for a radioactive waste treatment facility according to claim 1, wherein said low water-permeability layer is in the form of a compacted layer consisting of a sodium-type bentonite, sand, and mixing water mixture containing the sodium bicarbonate or sodium carbonate. 3. The artificial multi-barrier for a radioactive waste treatment facility according to claim 2, wherein said sodium bicarbonate, when used, is mixed at a concentration supersaturating the mixing water for use in forming said low water-permeability layer, or said sodium carbonate, when used, is mixed at a concentration exceeding the saturation concentration of said mixing water. 4. The artificial multi-barrier for a radioactive waste treatment facility according to claim 3, wherein said low water-permeability layer has said sodium bicarbonate or sodium carbonate, at least part of which being mixed in the form of powder so as to have, in the vicinity of the interface between said low water-permeability layer and said low diffusion layer and/or said back-filling layer, the concentration supersaturating said mixing water for use in forming said low water-permeability layer. 5. The artificial multi-barrier for a radioactive waste treatment facility according to claim 4, wherein fillers consisting of inorganic fine powders for use in providing a densified texture are held in said low diffusion layer and/or said back-filling layer. 6. The artificial multi-barrier for a radioactive waste treatment facility according to claim 1, wherein said low water-permeability layer is in the form of a compacted layer consisting of a sodium-type bentonite/sand/mixing water mixture containing the sodium bicarbonate or sodium carbonate. 7. The artificial multi-barrier for a radioactive waste treatment facility according to claim 6, wherein said sodium bicarbonate, when used, is mixed at a concentration supersaturating the mixing water for use in forming said low water-permeability layer, or said sodium carbonate, when used, is mixed at a concentration exceeding the saturation concentration of said mixing water. 8. The artificial multi-barrier for a radioactive waste treatment facility according to claim 7, wherein said low water-permeability layer has said sodium bicarbonate or sodium carbonate, at least part of which being mixed in the form of powder so as to have, in the vicinity of the interface between said low water-permeability layer and said low diffusion layer and/or said back-filling layer, the concentration supersaturating said mixing water for use in forming said low water-permeability layer. 9. The artificial multi-barrier for a radioactive waste treatment facility according to claim 8, wherein fillers consisting of inorganic fine powders for use in providing a densified texture are held in said low diffusion layer and/or said back-filling layer. 10. The artificial multi-barrier for a radioactive waste treatment facility according to claim 1, wherein said sodium bicarbonate, when used, is mixed at a concentration supersaturating a mixing water for use in forming said low water-permeability layer, or said sodium carbonate, when used, is mixed at a concentration exceeding the saturation concentration of said mixing water. 11. The artificial multi-barrier for a radioactive waste treatment facility according to claim 10, wherein said low water-permeability layer has said sodium bicarbonate or sodium carbonate, at least part of which being mixed in the form of powder so as to have, in the vicinity of the interface between said low water-permeability layer and the low diffusion layer at least containing cement or consisting of the cement-based material, the concentration supersaturating said mixing water for use in forming said low water-permeability layer. 12. The artificial multi-barrier for a radioactive waste treatment facility according to claim 11, wherein said radioactive waste includes low-level radioactive waste.