Microautoradiography in Studies of Pu(V) Sorption by Trace and Fracture Minerals in Tuff

Abstract

AbstractMicroautoradiography was used to evaluate the mineralogic basis of Pu(V) retention by tuffs from Yucca Mountain, Nevada. Altered orthopyroxenes and oxide minerals are associated with high Pu retention, but are limited to specific stratigraphic horizons. A weaker but more general association of Pu with smectite occurs in most samples. Thinsections that cross fractures allow comparative studies of Pu retention by fracturelining versus matrix minerals. Using Ag metal in emulsions as a measure of underlying Pu concentration, electron-microprobe (EMP) analysis can quantify Pu retention along fracture walls and provide mineral/mineral Pu retention factors. For smectite-lined microfractures in zeolitized tuff, the smectite/clinoptilolite Pu retention factor is <80.