The migration of HTO from a point source was studied in the soil of the storage of radioactive waste at horizontal distances of 10 to 40 cm from the source between 2 and 4 m depths at 5 different rainfalls, up to 7641/m2. The water movement changed from 0.17 cm/l (at 10 cm) to 0.28 cm/l (at 40 cm distance) when 186 1 was irrigated, while at 764 1 rainfall it was found to be 0.11 cm/l at every distance. The estimated parameters of a three-dimensional migration model constructed to characterize HTO movement revealed that the HTO distribution migrates downwards in a small, about 1 m thick layer with an initial rate of 0.17 cm/l to slow down to about 0.05 cm/l after 50 years. The distribution is spreading horizontally with a constant rate of about 0.08 cm/l.