Molecular Sponge for Nuclear Waste

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Image: SANDIA NATIONAL LABORATORIES

One of the principal products of nuclear fuel reprocessing is strontium-90, a radioactive form of strontium that, if exposed to living organisms, can damage bone cells and bone marrow. Recently, researchers sponsored by the Department of Energy's Environmental Management Science Program unveiled a new technology that acts as a molecular sponge¿it captures and stores radioactive strontium from liquid hazardous waste. "I am incredibly excited about this material," says Tina M. Nenoff, the principal investigator. "I think scientifically it¿s really interesting, and novel, and exciting."

The sponges are called Octahedral Molecular Sieves, or SOMS (right) (the first letter of the acronym is for Sandia National Laboratories, where Nenoff is based). Described in the February 21st issue of Journal of the American Chemical Society, they consist of microscopic pores that are adjusted to fit strontium-90 and contain negatively charged sites. Although these sites are normally bound to positively charged sodium atoms, when SOMS encounter liquid that contains strontium-90, they exchange the sodium for radioactive strontium, which has a stronger positive charge. In laboratory tests, the SOMS selectively captured 99.8 percent of strontium-90 ions from a solution containing a variety of metals. When heated, SOMS turn into perovskite, a stable material that can withstand extremely acidic and basic conditions, radiation and heat. Thus, SOMS are very likely well suited for disposal.

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Strontium-90 is one of the principal components of nuclear wastes, which are currently stored in a DoE network of underground tanks. Although Nenoff plans to test the SOMS technology for another two years before using it in the field, she believes it will play a significant role in cleaning up the remnants of nuclear fuel reprocessing. "This is what keeps me jazzed," she says. "[It] is just being able to work in this environmental clean up area ¿ and do my part to clean up the legacy."

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