Migration of Tc-99 in unsaturated Chinese loess under artificial rainfall condition: an in situ test

The migration of Tc-99 in unsaturated Chinese loess under artificial rainfa ll condition was investigated in situ. Water suckers were buried at differe nt depths under the bottom of an experimental pit of 2 m x 2 m x 1 m (deep) . Quartz containing H-3 and Tc-99 was introduced into the experimental pit to an area of 40 cm x 40 cm and the pit was backfilled to a thickness of 30 cm. An artificial rainfall of 5 mm/h was applied to the experimental pit 4 h a day for 3 months. Moisture water samples were sucked with the help of a vacuum pumping system and the activity of H-3 and Tc-99 in the samples wa s determined. Breakthrough curves of H-3 and Tc-99 indicated that Tc-99 was slightly retarded. The calculated average apparent distribution coefficien t of Tc-99 in the medium was (1.98 +/- 0.42) x 10(-2) ml/g.