PNNL

Abstract

A series of batch sorption and column experiments was conducted to investigate sorption and transport behavior of key radionuclides such as 99Tc, 129I, 79Se, and 90Sr on and through borehole sediments collected from the proposed low-level radioactive waste disposal repository at the Hanford Site (200 East Area). Batch sorption experiments conducted with uncontaminated Hanford groundwater or simulated glass leachates spiked with individual key radionuclides indicated that 90Sr showed the strongest sorption affinity, while 79Se sorption was intermediate, and 129I and 99Tc exhibited the least sorption among these radionuclides on the Hanford sediment. Transport behavior of these radionuclides through Hanford sediment provided similar results to the batch sorption experiments, suggesting high mobility for 99Tc and 129I compared to the intermediate and strong retardation in 79Se and 90Sr, respectively. Higher sorption affinity of 90Sr onto Hanford sediment from simulated glass leachate indicates that the proposed site’s natural Hanford sediment is adequate but engineered “getter” materials or barrier/cover materials should be placed on the repository to inhibit migration of mobile anionic radionuclides.