EFFECTS OF CELLULOSIC DEGRADATION PRODUCTS ON URANIUM SORPTION IN THEGEOSPHERE

The current design concept for intermediate- and some low-level radioa ctive waste disposal in the UK involves emplacement in a cementitious repository deep underground. The movement of radionuclides away from s uch a repository through the host rock formation towards the biosphere is expected to be retarded to a significant degree by sorption proces ses. One major issue being studied is the effect on uranium sorption o f degradation products arising from organic waste matter, especially c ellulosic materials. The sorption of uranium could be reduced by degra dation products, either because of complexation, or through the organi c materials competing for sorption sites. Because of the complexity of authentic degradation products, work has also been carried out using gluconate and iso-saccharinate as well-characterised simulants. In the presence of high concentrations of either the authentic or simulated degradation products, significant reductions in uranium sorption have been observed. However, in the presence of lower concentrations of the se organic materials, such as would be present in the repository, sorp tion was reduced at most by only a small margin and, in some cases, th e results suggested a slight increase.