The migration of radionuclides Np-237, Pu-238 and Am-241 in a weak loess aquifer: A field column experiment

The migration of radionuclides Np-237, Pu-238 and Am-241 in a weak loess aq uifer were investigated in-situ with a bisectional experimental column. The experimental column was constructed by connecting 2 undisturbed aquifer me dium columns together and inserted into the aquifer horizontally through ho les pre-prepared in the wall of a vertical experimental shaft in an Undergr ound Research Facility at the CIRP's field test site. Quartz containing rad ionuclides H-3 Np-237, Pu-238 and Am-241 was introduced as a point source a the center of the experimental column. Outflow water of the experimental c olumn was collected and H-3 in the outflow was determined for calculating t he water flow velocity through the experimental column. The experimental co lumn was cut into slices of 0.3cm long and the radioactivity of Np-237, Pu- 238 and Am-241 in the sliced soil samples was analyzed when the experiment was completed The water flow velocity in the experimental column was calculated as 1.15 /- 0.05 cm/d. The activity distribution of Np-237, Pu-211 and Am-241 in the experimental column indicate that each radionuclide has a very strong acti vity distribution region adjacent to the source introduction point and decr eases abruptly as the distance increases. In addition there are other secon dary activity distribution regions with different strength and widths. The calculated apparent distribution coefficients of the main specie of these r adionuclides is (8.90 +/- 1.51) x 10(2) ml/g for Np-237, (9.48 +/- 1.61) X 10(2) ml/g for Pu-238 and (9.79 +/- 1.66) x 10(2) ml/g for Am-241.