As a part of investigation on the properties of water as a medium for the migration of radionuclides in a buffer material in nuclear waste disposal facility, the diffusion of tritium in the form of tritiated water and electrical conduction in compacted sodium montmorillonite saturated with distilled water were studied as a function of dry density and temperatures from 278 to 323K. The activation energies of electrical conduction were almost same as or slightly greater than those of diffusion of hydrogen isotopes and H{sub}2 18{sup left}O in pure water. The activation energies of the electrical conductivity as a function of dry density were fairly in good agreement with those of tritium but were different from those of sodium ions. The present results indicate the charge carrier for conduction in the compacted montmorillonite is protonic rather than sodium ions.
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