CST Helps Cleanup Fukushima

Wednesday, May 30, 2012 @ 01:05 PM gHale

A molecular sieve that can separate highly volatile elements from radioactive wastewater, crystalline silico-titanate (CST), is now in Japan helping remove radioactive material at Japan’s damaged Fukushima Dai-ichi nuclear power plant.

The CST, created by Sandia National Laboratories and licensed by UOP, has removed more than 43 million gallons of contaminated wastewater at Japan’s earthquake and tsunami ravaged plant.

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The late Sandia chemist Bob Dosch and Texas A&M chemical engineering professor Ray Anthony were leaders of the team that developed CSTs in the early 1990s response to a need for materials to remove radioactive contaminants from wastewater. They found a certain class of synthetic zeolite is more effective in capturing some radioactive elements, like cesium, than other technologies.

They created CSTs: Inorganic, molecularly engineered ion exchangers they can size specifically for cesium and other elements. When you can remove high-level radioactive elements from contaminated water with CSTs, then it is possible to treat the remaining lower-level radioactive in a more economical and less hazardous way.

UOP worked with Sandia through a Cooperative Research & Development Agreement (CRADA) to produce a commercial-scale manufacturing procedure for the CSTs. “We developed a technology to bind the material into a beaded form so it could be used in ion exchange columns,” said Dennis Fennelly, UOP marketing manager.

CSTs came to mind for the Dai-ichi nuclear plant after the earthquake and tsunami hit March 11, 2011.

Seawater pumped in to cool the reactors, said Mark Rigali, manager of the geochemistry group at Sandia. The water suffered from contamination with cesium, a common fission product in reactor fuel. That meant the product could not release back into the ocean. “The Japanese were looking for a way to clean up the water,” Rigali said. “That’s where the CSTs came in.”

But nobody knew whether the technology worked in seawater.

DOE called on Sandia chemist Tina Nenoff at the end of March 2011 to test CSTs for removal of cesium in concentrated seawater, due to her extensive experience in developing and working with CSTs in the 1990s. Nenoff and colleague Jim Krumhansl worked around the clock for 10 days. “There was a sense of urgency,” Nenoff said. “We compared CSTs against commercially available zeolites, mineral zeolites and some clays. We found the CSTs outperformed the other materials for cesium removal from seawater under these conditions.”

Rigali said other materials can capture cesium, “but there’s nothing out there that works as well as a CST. It’s tough to beat.”

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