On April 25, 2013, Senators Wyden, Alexander, Feinstein, and Murkowski released a draft bill to create a sustainable, participatory process for managing nuclear waste. The senators requested comments and suggestions on the draft bill, as well as on the alternative language for siting an interim storage facility proposed by Senators Alexander and Feinstein. In addition, the senators posed eight questions on which they sought comments.

This report presents the analyses and results for the potential occurrence of external criticality events which could result from plutonium waste forms emplaced in a geologic repository similar to the one being developed at Yucca Mountain. The analyses evaluate both the MOX spent fuel and the immobilized plutonium waste forms in a repository if the waste package has degraded and if the fissile material has migrated to the invert and out into the far-field.