Lab Discovers Material to Help Process Spent Nuclear Fuel

Tina Nenoff (Randy Montoya, Sandia National Lab)

Research chemists at Sandia National Lab in Albuquerque have developed a new material that can capture and remove volatile radioactive gas from spent nuclear fuel. The team led by Tina Nenoff (pictured right) published their findings recently in the Journal of the American Chemical Society; paid subscription required.

The Sandia researchers, with colleagues from Argonne National Lab in Illinois, used metal-organic frameworks (MOFs) — crystalline, porous materials in which a metal center is bound to organic molecules by a self-assembly process of chemical synthesis. The Sandia team focused on using MOFs to remove iodine, whose isotopes have a half-life of 16 million years, from spent fuel that cannot be burned off as fuel.

The team started with known materials, including silver-loaded zeolite, a crystalline, porous mineral with regular pore openings, high surface area and high mechanical, thermal, and chemical stability. Zeolite frameworks are known to trap and remove iodine from spent nuclear fuel, but need silver added to work well. Silver, however, is expensive and poses its own health and environmental problems.

The researchers then engineered a new material without silver that would work like zeolites, but with a higher capacity for gas molecules, in this case an MOF highly selective for iodine. The Sandia team found the zeolite Mordenite and took its best elements — pores, high surface area, stability, and chemical absorption — that led to an MOF with the ability to separate iodine from a stream of molecules. The MOF and pore-trapped iodine gas can then be incorporated into glass waste for long-term storage.

Nenoff’s team had one more task to create a viable material: generate the MOF material in a useful and efficient form for the field. The material first created by the team emerged as a fine powder that blew away in a breeze and thus would likely have been wasteful in a production setting.

To meet this need, the Sandia researchers developed an MOF in pellet form, using commercially available products, which provides a more stable material to use without loss of surface area. Sandia has applied for a patent on the pellet technology, which could have commercial applications.

Read more: Microbes Found to Clean Nuclear Waste, Generate Electricity

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