Elemental depth profiling of nuclear waste glasses after two-years burial in a salt geology

This paper reports that detailed surface compositional analysis has been conducted on 12 simulated nuclear waste forms leached for two years in the brine environment of the Waste Isolation Pilot Plant (WIPP). Secondary ion mass spectrometry (SIMS) of both cations and anions has identified characteristic leaching and precipitation zones within the leached layers on all specimens. The thickness of the leached layer is found to range from approximately 0.3 to 2.7 μm and the total element loss from 80 to 625 mmol/m2, indicating that durability in brine differs by less than an order of magnitude between the different glasses. The in-depth profiles of anionic elements indicate the significant roles of carbon, fluorine, and chlorine in the formation of surface phases. Also recorded and discussed are elemental SIMS images of sputter crater tapers, providing additional documentation of leaching subzones