Alternative Igneous Source Term Model for Tephra Dispersal at the Yucca Mountain Repository

The Nuclear Regulatory Commission uses the ASHPLUME model in its evaluation of the basaltic volcanism scenario at the possible Yucca Mountain repository. The mixing of magma with the spent-fuel waste form is tied to a reasonable but unverified model that predicts that no dense tephra/fuel particles would form. An alternative model uses a mixing rule that allows the formation of dense tephra/fuel particles that would be transported in the volcanic plume differently. The alternative model shows significant sensitivity to the spent-fuel particle size distribution. However, differences in results between the two models are on average less than a factor of 2.