Effect of Waste Package Components on Radionuclides Released from Spent Fuel under Hydrothermal Conditions.

摘要

The Basalt Waste Isolation Project has conducted a series of hydrothermal experiments to characterize waste/barrier/rock interactions as a part of its study of the Columbia River basalts as a potential medium for a nuclear waste repository. Hydrothermal tests of 3--15 months duration were performed with light water reactor spent fuel and simulated groundwater, in combination with candidate container materials (low-carbon steel or copper) and/or basalt, in order to evaluate the effect of waste package materials on spent fuel radionuclide release behavior. In all experiments, (sup 14)C, (sup 129)I, and (sup 137)Cs occurred only as dissolved species, whereas the actinides occurred in 400 nm filtrates primarily as spent fuel particles. Actinide concentrations in 1.8 nm filtrates were below detection in steel-bearing experiments. In the system spent fuel + copper, apparent time-invariant concentrations of (sup 14)C and (sup 137)Cs were obtained, but in the spent fuel + steel system, the concentrations of (sup 14)C and (sup 137)Cs increased gradually throughout the experiments. In experiments containing basalt or steel + basalt, (sup 137)Cs concentrations decreased with time. In tests with copper + basalt, (sup 14)C and (sup 129)I concentrations attained time-variant values and (sup 137)Cs concentrations decreased. Concentrations for the actinides and fission products measured in these experiments were below those calculated from Federal regulations governing radionuclide release. 12 refs., 7 figs., 5 tabs. (ERA citation 13:047318)