Determination of diffusion coefficient of ¹³⁷Cs at unsaturated zone of DH-2 site soil under δ = 1.41 g.cm⁻³ condition

Radiocesium is one of the reference radionuclide on low-level radioactive waste disposal system. For the safety assessment of environment around the disposal facility, it needs to be studied their characters on the candidate site of radioactive waste disposal facility. Diffusion coefficient is important to be studied especially on the unsaturated zone lies between the foundation of facility and the saturated zone. In this experiment, soil samples were taken out from the logging result of DH-2 hole of SP-4 site on the 7 m depth from surface. Work was done in the diffusion column by gravitation method under density condition was 1.41 g.cm⁻³. The diffusion coefficient is determined in one dimension using non-steady diffusion method with variation of diffusion time and has obtained the smallest of Da value of ¹³⁷Cs in the soil sample was 1.76 E-12 m²s⁻¹ at the 6 months of diffusion time. The results show that the longer of length diffusion time, the smaller diffusion value was obtained. (paper)