New Technique Recycles Radioactive Ash

A new plant soon will recover uranium from the ashes of radioactive garbage to be recycled back into nuclear fuel using an efficient, environmentally friendly technology. The technique is inspired by decaffeinated coffee, and its future may hold the key to recycling even the most dangerous forms of radioactive waste.

Over the course of 20 years, University of Idaho chemistry professor Chien Wai has developed a process that uses supercritical fluids to dissolve toxic metals. When coupled with a purifying process developed in partnership- with Sydney Koegler, an engineer with nuclear industry conglomerate authority AREVA, enriched uranium can be recovered from the ashes of contaminated materials. On Aug. 20, 2008, representatives from the company and the university signed an agreement to share the technologies and pave the way for the recycling plant’s construction.

“Radioactive waste is a big problem facing the United States and the entire world,” Wai said. “We need new, innovative technology, and I think supercritical fluid is one such technology that will play an important role in the very near future.”

A supercritical fluid—in this case, carbon dioxide—is any substance raised to a temperature and pressure at which it exhibits properties of both a gas and a liquid. When supercritical, the substance can move directly into a solid and dissolve compounds. For example, Wai said, supercritical carbon dioxide has directly dissolved and removed caffeine from whole coffee beans for decades.

When the carbon dioxide’s pressure is returned to normal, it becomes a gas and evaporates, leaving behind only the extracted metals. No solvents are required, no acids need to be applied, and no organic waste is left behind.

Because the technology is so simple, cost-effective and environmentally friendly, AREVA plans to test its first full-scale use on 32 tons of incinerator ash in Richland, Wash.

The Richland plant fabricates fuel for commercial nuclear power plants from raw enriched uranium supplied by utility customers as uranium hexafluoride (UF6). During normal operation, common items including filters, rags, paper wipes, and gloves become contaminated with uranium. The waste is burned to reduce its volume and increase its uranium content, making it easier to recover the uranium.

Nearly 10 percent of the ash’s weight is usable enriched uranium, worth about $900 dollars per pound on today’s market. This means, according to AREVA, about $5 million dollars is currently sitting in the garbage waiting to be recovered. The process may even become the basis of the next generation of plants designed to recover useful materials from spent fuel.

The new recycling plant is expected to be operational in 2009 and will take about a year to process AREVA’s ash inventory. When finished, much of its operating time can be devoted to ash received from other sites.

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