PNNL

Abstract

One of the advantages of molten salt reactors (MSRs) is their ability to dynamically release volatile fission products such as Kr and Xe from the bulk fuel. In order to manage this consistent radioactive off-gas, massive delay beds of activated carbon are required to allow sufficient decay of short-lived isotopes prior to processing or release. However, these beds are immense, inefficient, and flammable, significantly hindering the facile deployment of MSRs. An improved bed material would demonstrate both higher delay efficiency as well as selectivity for Xe over Kr for the harvesting of valuable noble gases. Here, we incorporate a Xe-selective metal-organic framework, SBMOF-1, into engineered beads for the dynamic management of off-gases released from MSRs. Single column breakthrough experiments demonstrate that pressure-compacted SBMOF-1 pellets outperform the industrial carbon standard at all conditions, in terms of both total Xe capacity and Xe/Kr selectivity. By employing SBMOF-1 pellets, delay bed mass and volume are significantly reduced (up to 45% and 52% at 0°C compared to activated carbon) with no sacrifice in performance. The SBMOF-1 pellets also demonstrate roughly 50% more substantial Xe/Kr separation than activated carbon at all temperatures, delaying Xe breakthrough by a maximum factor of 37.7 compared to Kr breakthrough at -40°C. These results motivate the continued development of efficient sorbent technology for MSR off-gas management towards global energy solutions and novel compact power needs