Thursday, 15 July 2010

Recycling radioactive waste no longer a problem

Published in August 22nd, 2008 by IANS in

A new plant will help recover uranium from the ashes of radioactive wastes, which can then be recycled with an efficient, eco-friendly technology inspired by decaffeinated coffee and using supercritical fluids. The technique’s future may even hold the key to recycling the most dangerous forms of radioactive waste in the near future.

Chien Wai, University of Idaho chemistry professor, has developed a process that uses supercritical fluids to dissolve toxic metals. When coupled with purifying process developed in partnership with Sydney Koegler, an engineer with nuclear industry leader AREVA and University of Idaho, enriched uranium can be recovered from the ashes of contaminated materials.
“Radioactive waste is a big problem facing the US and the entire world,” said Wai. “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 like a gas and yet dissolve compounds like a liquid. For example, said Wai, 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 required, no acids applied, and no organic waste left behind.
“That’s why decaffeinated coffee tastes so good,” said Wai, while chuckling at the beauty and simplicity of the process. “There is no solvent used, and so no solvent left behind.”
Because the technology is so simple, cost-effective and environmentally friendly, AREVA is eager to test its first full-scale use on 32 tonnes of incinerator ash in Richland, Washington.
The existing plant in Richland 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 $1,800 dollars a kg in today’s market. This means about $5 million dollars is currently sitting in the garbage waiting to be recovered.
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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