PNNL

Abstract

A major challenge for the processing of used nuclear fuel (UNF) is the release of volatile radionuclides that must be captured and subsequently stored. Solid adsorbents, in particular ultra-microporous metal-organic frameworks (MOFs), could be effective in capturing these volatile radionuclides including 85Kr. However, MOFs are found to be more Xe-philic than Kr and have comparable affinity of Kr and N2. Also, the adsorbent needs to have high irradiation stability. To address these challenges, here we evaluate a series of ultra-microporous MOFs, SIFSIX-M (M= Zn, Cu, Ni, Co or Fe) for their potential in 85Kr separation and storage using a two-bed breakthrough method. These materials were found to have higher Kr/N2 selectivity than the current benchmark materials, which lead to a notable decrease in the nuclear waste volume. All materials were systematically studied for gamma irradiation stability, which reveals that the metal centre in these isostructural frameworks plays a crucial role in their radiation resistance.