Using Metal-Organic Frameworks and Enriching Pressure Swing Adsorption Cycles for Future Radionuclide Monitoring Systems

First-generation noble gas detection systems currently used by the International Monitoring System (IMS) operate in a similar manner: air is pumped into an activated carbon sieve bed where the radioxenon is isolated. Contaminants are removed, including water, carbon dioxide, and dust. As a result, the sorbent has concentrated xenon, both naturally abundant isotopes and radioactive isotopes, from the sampled air. The radioactivity of the isolated and concentrated xenon is measured, and the resulting spectrum is sent to the International Data Centre (IDC) for further analysis. The minimum detectable concentration of Xe-133 is ~ 1 mBq/m3. These air sampling units used to detect underground nuclear explosions would be significantly enhanced with next generation sorbent materials bearing higher radionoble gas capture capacities and selectivities. Currently, carbon adsorbent materials are being used in an inefficient and low retention multistage purification process. New sorbent materials, particularly silver doped zeolite, are being pilot tested affording a near 10-fold increase of xenon retention capacity, thus allowing for single stage columns during the final air sampling concentration step. Although silver doped zeolites afford an increased retention of radioxenon from the incumbent activated carbon materials, there is significant potential to further improve radioxenon retention and concentration using MOFs. NuMat Technologies has (1) developed scalable techniques for a promising xenon capturing metalorganic framework (MOF) adsorption material and (2) modeled novel enriching pressure swing adsorption (PSA) separation cycle capable of concentrating xenon found in air from ppb levels to single digit percentage levels. This modeled process precludes the use of exotic sensors to detect radioisotopes of xenon produced during underground nuclear events. Under this SBIR, NuMat Technologies will build and evaluate a prototype by incorporating the previously developed MOF into the previously modeled enriching PSA separation system enabling improved radioxenon retention and detection while reducing uncertainty.