Reactive transport of Sr, Cs and Tc through a column packed with fracture-filling material

The migration behaviour of the fission products Sr-90, Cs-137 and Te-99 in a granite fracture-groundwater system was studied in column experiments usi ng crashed Stripa granite fracture-filling material (125-250 mu m) as a sor bent. Based on breakthrough curves of Sr2+, Cs+, TcO4- and anthraquinonsulp honate, the distribution ratio K-d(cm(3)/g) values for Sr2+ and Cs+ were es timated to be 1.5 and 2 respectively; non-sorbing behaviour of TcO4- under oxic conditions was observed. The diffusion of Sr2+ in the material is show n to be a kinetic-controlling step in the desorption process that followed the initial leaching. Under reducing conditions, it was found that TcO4- wa s reduced to TcO2. nH(2)O(s) by the Fe(II)-containing fracture-filling mate rial and Tc(IV)(aq) was rapidly sorbed by the material. This observation pr oves that the migration of technetium under reducing conditions in deep gro undwater systems will not only be controlled by the solubility of TcO2. nH( 2)O(s) and the speed of groundwater flow but also by the rapid sorption of Tc(IV)(aq) on all available mineral surfaces.