Patent Number: 
Section: claims

1. A water-blocking filler mainly comprising sodium type bentonite, wherein more than 1 to 3% by weight or less of silica fume as a pozzolan substance in terms of a percentage by weight relative to a total amount of said sodium type bentonite is mixed with said sodium type bentonite. 2. A method for making an engineered multi-barrier in a radioactive waste disposal facility using the water-blocking filler according to claim 1, comprising:providing a low diffusion layer configured to be proximate to the radioactive waste, said low diffusion layer having a proximate and a distal side; andproviding a layer of said water-blocking filler adjacent to said low diffusion layer distal side. 3. A method for making an engineered multi-barrier in a radioactive waste disposal facility using the water-blocking filler according to claim 1, comprising:providing a carbon steel container for the waste; andsurrounding said container with a layer of said water-blocking filler.