Field study of the migration of Sr-90, Np-237, Pu-238 and Am-241 in unsaturated Chinese loess under artificial rainfall condition

The migration of Sr-90, Np-237, Pu-238 and Am-241 in unsaturated Chinese loess under artificial rainfall condition was investigated at the CIRP's field test site. Quartz containing Sr-90, Np-237, Pu-238 and Am-241 was introduced into an experimental pit and the pit was backfilled. Artificial rainfall of 10-15 mm/d was applied to the experimental pit for 1078 days. HTO was used for obtaining the migration rate of moisture water in the pit. Vertical core soil samples were taken twice a year and Cut into 0.5 cm long section soil samples. The section soil samples were weighed and wind dried. Radioactivity of Np-237 and Am-241 in the section soil samples was measured with a low energy photon detector (HPGe); Sr-90 and Pu-238 were determined with a low background alpha beta detector after chemical separation. During the experiment, moisture water at different depths was taken on a daily basis and H-3 in the moisture water samples was determined with liquid scintillation technique. Experimental result indicates that the downward migration rate of moisture water was 2.27 cm/d and the retardation factors of Sr-90, Np-237, Pu-238 and Am-241 in the loess unsaturated zone were 9.9 x 10(2), 3.2 x 10(3), 3.2 x 10(3) and 4.5 x 10(3), respectively. This result suggests that Sr-90, Np-237, Pu-238 and Am-241 could be effectively retarded by the loess unsaturated zone.Chemistry, Inorganic & NuclearNuclear Science & TechnologySCI(E)1ARTICLE289-949