GEOCHEMICAL BEHAVIOR OF TC-99 IN THE OKLO NATURAL FISSION REACTORS

Ru isotopic ratios of five Oklo uranium ore samples were determined by inductively coupled plasma mass spectrometry (ICP-MS). We found fissi ogenic Ru enriched metallic micro-inclusions in the samples, so in-sit u isotopic measurements were performed by secondary ion mass spectrome try (SIMS). From the isotopic abundances of fissiogenic Ru-99, the geo chemical behaviour of Te-99 in the Oklo natural reactors could be infe rred. More Ru-99 has been enriched in metallic inclusions of the sampl es than in matrix uraninite grains.