[Comparison of migration characteristic of 3H and 99Tc in loess]

3H and 99Tc are important nuclides in low and intermediate level radioactive wastes, and in safety assessment of near surface repository their migration characteristic usually determines the computing result. The medium of loess appears to possess the characteristic of weak adsorption ability to 3H and 99Tc when they are migrating in it, so the adsorption ability are often neglected, and 3H are used to identify groundwater velocity. But in the field test it was showed that in the aerated zone loess possesses stronger adsorption ability to 99Tc than to 3H, and in the aquifer the stronger adsorption ability to 3H than to 99Tc. In this paper the migration tests of 3H and 99Tc were simulated by NESOR program of non-equilibrium adsorption model. The results show: 99Tc distribution coefficient ranges 0.05-0.055 mL/g in the aerated zone, 3H distribution coefficient is 0.116 mL/g in the aquifer, and the parameter reflects integrated impact of loess on 3H and 99Tc, and the mechanism of them being retarded still need proving.