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

摘要

The migration of radionuclides Np-237, Pu-238 and Am-241 in a weak loess aquifer were investigated in-situ with a bisectional experimental column. The experimental column was constructed by connecting 2 undisturbed aquifer medium columns together and inserted into the aquifer horizontally through holes pre-prepared in the wall of a vertical experimental shaft in an Underground Research Facility at the CIRP's field test site. Quartz containing radionuclides 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 column was collected and H-3 in the outflow was determined for calculating the water flow velocity through the experimental column. The experimental column 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 activity distribution region adjacent to the source introduction point and decreases abruptly as the distance increases. In addition there are other secondary activity distribution regions with different strength and widths. The calculated apparent distribution coefficients of the main specie of these radionuclides 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. [References: 12]