Sorption of protactinium on Finnish bedrock

The sorption behavior of protactinium, which is a decay product of uranium, on the main rock types from the potential areas selected for construction of a repository was studied. The sorption distribution coefficients R-d of Pa were determined under ambient toxic) atmosphere and anoxic (nitrogen) at mosphere using natural fresh (Romuvaara and Kivetty) and brackish (Olkiluot o) groundwaters. The following R-d values (m(3)/kg) were obtained: for Romu vaara rock samples in Romuvaara groundwater under anoxic conditions, 0.07-2 .3 m(3)/kg and under oxic conditions, 0.20-1.8; for Romuvaara rock samples and Kivetty and Olkiluoto groundwaters under anoxic conditions, 0.70-8.6 an d 0.35-1.7, respectively (the values obtained with Kivetty and Olkiluoto ro ck samples were almost the same); for Kivetty rock samples and Kivetty grou ndwater under oxic and anoxic conditions, 0.51-1.7 and 1.7-12, respectively ; and for Olkiluoto rock samples and Olkiluoto groundwater under oxic and a noxic conditions, 0.71-3.1 and 0.31-2.4, respectively.