DISTRIBUTION OF ANTIMONY-125, CESIUM-137, AND I-129 IN THE SOIL-PLANT SYSTEM AROUND A NUCLEAR-FUEL REPROCESSING PLANT

Field studies were conducted during the summer of 1987 to characterize the distribution of Sb-125, Cs-137 and I-129 in vegetation and soil at distances of 0.45 and 0. 75 km from a nuclear fuel reprocessing plant. Samples of sagebrush, wheatgrass, and rabbitbrush were collected and the leaves, stems, roots, and litter of the plants were separated. The vegetation samples were then dried at 70-degrees-C for 48 h, ground, and the concentrations of Sb-125 and Cs-137 were determined by gamma spectrometry. Using iodine separation and mass spectrometric techniques, I-129/I-127 atom ratios were also determined in the vegetation components. Soil samples were collected from the surface to a depth of 18 cm (at 3 cm increments), dried at 45-degrees-C, and the concentrations of Sb-125 and Cs-137 measured in the same manner as the vegetation samples. Results showed that the activity of Sb-125 was higher in the leaves than in the stem and roots. Of the total activity of Sb-125 (1041.7 Bq m-2) 33.4% was distributed in vegetation and 66-6% was distributed in soil. Cesium-137 concentrations were lower in the leaves than in the stems and roots. The I-129/I-127 isotopic ratios were in the range of 1.32 x 10(-2)-8.00 x 10(-4), decreasing from the leaves to the roots. Results indicated a slow downward translocation of CS-137 and I-129 through the plant tissues. Deposition of airborne Sb-125 measured through absorption on to transplanted vegetation was about one Bq m-2 d-1. Leaves of the transplanted sagebrush plant showed measurable accumulations of I-129 and I-129 and perturbed isotopic ratios after an exposure of 11 weeks.