Diffusion of Tc-99 in granite: A small scale laboratory simulation experiment

The diffusion of Tc-99 in granite was investigated with small-sized diffusi on cells, composed of a radioactive source solution cell and a sampling cel l. Water in the two cells was kept at the same level. I ml aliquots were ta ken from the sampling cells daily during the first 50 days, then at interva ls of several days, and measured via liquid scintillation counting. The exp erimental results indicate that the diffusion of Tc-99 and H-3 in granite f ollows the one-dimensional diffusion equation when diffusion time is long e nough (> 100 days). The calculated average diffusion coefficient of Tc-99 ( 1.4 x 10(-12) m(2)/s) is about one half of that of H-3 (3.2 x 10(-12) in m( 2)/s).