Investigation of Xe and Kr Capture with Porous Materials: Towards UNF Recycling Readiness

Xenon and krypton are released upon processing of used nuclear fuel. Their management via capture and storage remains critical to the success of a commercial used nuclear fuel (UNF) recycling facility owing to the regulatory requirements (including 40 CFR Part 190) governing their free release. Conventional technologies for capture and storage present as high technology readiness level but can be costly and cumbersome to implement. The objectives of SHINEĺs Phase I and Phase II efforts are to fully explore the gas adsorption properties of porous materials, primarily, hollow glass microspheres, and fabricate engineering-scale systems allowing flow- through studies under simulated UNF conditions. Phase I marked the beginning of SHINEĺs investigation of gas capture and storage. Early on, a highly custom Sieverts-type apparatus was built with dual gas and vacuum inputs for batchwise studies of gas uptake under elevated temperatures. Different classes of metal-coated and uncoated HGMs were procured and characterized with microscopy. All samples were contacted with He during a campaign to establish the optimal parameters for successful gas adsorption and desorption. Afterwards, Kr uptake was quantified and compared with current state-of-the-art technologies. The Phase II project builds on the preliminary findings of Phase I in an effort to increase the readiness level of this technology. Two components are planned to support this goal: an engineering scale-up of material testing including the fabrication of a flow-through skid and further elucidation of the optimal parameters needed for selective Xe/Kr capture and storage under conditions relevant to UNF recycling. This technology has the potential for numerous commercial and public benefits. Kr storage in hollow glass microspheres would allow for the formation of a small-volume, robust waste form paving the way for the commercialization of used nuclear fuel recycling plants. The Xe, on the other hand, represents a commercial product which could supplement domestic production of this rare but valuable gas. Establishment of a process by which the minor gaseous constituent is captured in the presence of a much large volume of total gaseous waste (such in the case of Xe/Kr capture where Xe is 10x the amount of Kr) could prove informative to the CO2 capture efforts of others.