Metal frameworks could capture krypton-85 during reprocessing

August 4, 2020, 9:51AMAround the Web

Separation of Kr-85 from spent nuclear fuel by a highly selective metal organic framework. Image: Mike Gipple/National Energy Technology Laboratory

According to a story published by the Massachusetts Institute of Technology on July 24, the capture of gaseous fission products such as krypton-85 during the reprocessing of spent nuclear fuel could be aided by the adsorption of gasses into an advanced type of soft crystalline material, metal organic frameworks(MOF), which feature high porosity and large internal surface areas that can trap an array of organic and inorganic compounds.

Copper shows promise: A group of researchers, including members of MIT’s Department of Nuclear Science and Engineering and the Department of Energy’s National Energy and Technology Laboratory, recently published a studyin the journal Nature Communicationsthat evaluated a series of ultra-microporous MOFs with different metal centers, including zinc, cobalt, nickel, and iron. They measured the efficacy and radiation resistance of the materials and found that a copper-containing crystal, SIFSIX-Cu, showed good promise for practical applications of MOFs to spent fuel management.

What’s the benefit? Existing methods for capturing gasses during reprocessing tend to collect oxygen and nitrogen gas, as well as the tiny quantities of krypton, increasing the waste volume, according to MIT. To optimize radiation stability and selective adsorption while also minimizing the volume of waste, the team proposed a two-step treatment process. An initial bed of the material is used to adsorb xenon and carbon dioxide from the effluent gas mixture before it is transferred to a second bed that selectively adsorbs krypton, but not nitrogen or oxygen.


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