Waste Package Neutron Absorber, Thermal Shunt, and Fill Gas Selection Report

Materials for neutron absorber, thermal shunt, and fill gas for use in the waste package were selected using a qualitative approach. For each component, selection criteria were identified; candidate materials were selected; and candidates were evaluated against these criteria. The neutron absorber materials evaluated were essentially boron-containing stainless steels. Two candidates were evaluated for the thermal shunt material. The fill gas candidates were common gases such as helium, argon, nitrogen, carbon dioxide, and dry air. Based on the performance of each candidate against the criteria, the following selections were made:
Neutron absorber: Neutronit A978
Thermal shunt: Aluminum 6061 or 6063
Fill gas: Helium