Overview of waste package and repository conceptual designs and the corresponding near-field conditions

Conceptual designs for spent fuel (SF), defense (DHLW), and commercial (CHLW) high level waste packages, repository layout concepts, waste package emplacement configurations, and anticipated key environmental factors were presented. Design features for the waste package and repository are closely related to environmental conditions in the near field. These features include waste package heat output, overpack wall thickness, area heat loading, dimensions of the waste package/borehole annulus at emplacement, and package emplacement pitch. Container material planned for all three waste forms is low carbon steel. Reference thickness of the container ranges from 8.63 cm for DHLW to 10.0 cm for SF. Borosilicate glass will be the waste form for DHLW. The DHLW will be combined with glass formers, melted and poured into a stainless steel canister approximately 61 cm in diameter and 3 m long. The canister will be filled to 85% capacity and placed in the low carbon steel container. Spent fuel assemblies will be consolidated and inserted into the low carbon steel container, and the closure welded. Key environmental factors were defined as those influencing brine migration to or away from the waste package; container corrosion; or radionuclide release after container breach. Factors include temperature, gamma radiation field intensity, pressure, brine inflow rate, and brine chemistry. Appendix contains 23 vugraphs