Uranium-Series Disequilibrium Studies of Unaltered Rocks from the Lac du BonnetBatholith

摘要

Uranium series disequilibrium analyses have been made on pristine and unalteredcore samples from 440 m to 1000 m depth in the lac du Bonnet granitic batholith. The data show that naturally occurring isotopes of uranium, thorium and radium in the granite are in secular equilibrium and, therefore, have been immobile over the last 10(sup 4) to 10(sup 6) years. The presence of pore fluids in the rock matrix does not appear to have influenced this state of equilibrium. These results suggest, by analogy, that isotopes of the same elements in nuclear fuel waste, will be immobile in the geosphere for a similar period of time. This evidence provides independent support to the safety assessment performed for the Canadian concept for disposal of nuclear fuel waste.