Radionuclide release rates from natural analogues of spent nuclear fuel

Measurements of 99Tc, 129I, 239Pu and U concentrations in rock samples from uranium deposits at Cigar Lake and Koongarra have been used to estimate radionuclide release rates from uranium minerals. Rates of release have been immeasurably slow at Cigar Lake. At Koongarra release rates appear to have been faster, producing small deficiencies of 99Tc, and larger ones of 129I. The differences in model radionuclide release rates are consistent with expected differences in uranium mineral degradation rates produced by the differing hydrogeochemical environments at the two sites. The model release rates are orders of magnitude less than those used to simulate mineral alteration rates in the initial Sandia Total Safety Performance Assessment