Susumu Horiuchi

Removal of radioactive methyl iodide by silver impregnated alumina and zeolite

Abstract The removal efficiency of methyl iodide for silver impregnated alumina and zeolite has been experimentally evaluated as functions of the relative humidity in the atmosphere and the amount of impregnated silver. At high relative humidities silver alumina performs with a larger removal efficiency using a smaller amount of impregnated silver than does silver zeolite. This difference is explained by effective reacting surface. The pore size dependency is correlated with the pore diffusion rate as the determining adsorption mechanism.

A pelletizing model and its application to radioactive waste treatment

A pelletizing mechanism was studied theoretically and experimentally to transform radioactive waste powders into dense and hard pellets in conjunction with the development of a new volume reduction system, a drying and pelletizing system. A pelletizing model was proposed based on plastic deformation of powder particles. Its validity was confirmed by fundamental experiments. From the model, such pellet properties as density and strength can be predicted over a wide compacting pressure range of a pelletizer using one material constant, the shear modulus of the powder, and one experimental value. This led to the proposal of a method to control the pelletizer and to estimate pellet properties. Usefulness of the method was confirmed experimentally from pilot plant tests.

Properties of a radioactive waste pellet package using cement-glass

This paper reports on radioactive waste slurry generated from nuclear power plants which is dried and compressed into pellets. These pellets are dropped in a polymer-impregnated concrete (PIC) barrier and solidified with cement-glass, which is a mixture of sodium silicate and cement. The mechanical strength of the PIC barrier is about three times higher than that of ordinary portland cement because of added steel fibers. The leaching ration form the package is experimentally studied using {sup 14}C, {sup 60}Ci, {sup 85}Sr, {sup 99}Tc, {sup 125}I, and {sup 134}Cs. Because of the low porosity of the PIC barrier, the leaching rate is controlled and increases in proportion to immersion time. The maximum leaching ratio from a 200-l package is estimated to be 0.004/yr.