Highly magnetic nanoparticles, originally devised for biomedical purposes, soon will be tested against one of the most toxic substances known to man - spent nuclear fuel. The project - funded by a one-year, $732,000 Department of Energy research grant - plans to prove the feasibility of using MNPs joined with binding chemicals called chelators to extract radioactive nuclides, such as uranium and plutonium, from spent nuclear fuel.
Leading the interdisciplinary nano-research team at the University of Idaho are principle investigators You Qiang, associate professor of physics, and Andrzej Paszczynski, associate professor of microbiology, molecular biology and biochemistry. The pair will work in collaboration with Linfeng Rao, nuclear chemist at Lawrence Berkley National Laboratory in California.
If successful, scientists at the University of Idaho will kill three birds with one nanoparticle by recovering usable nuclear fuel, making nuclear waste easier and safer to dispose of, and accomplishing the task in an environmentally friendly way.
"We believed from the very beginning that this project was a very good idea," said Paszczynski. "To achieve energy independence, America likely will build many new nuclear power plants. More plants mean more waste, which must be reduced and recycled."
The fundamental technology that makes the process possible is the ability to make the MNPs. These are tiny pieces of pure iron nanoparticles coated with a layer of iron oxides, commonly known as rust, just two nanometers thick. Because of their iron core, the MNPs are 10 times more magnetic than commercially available nanoparticles that typically are made entirely of iron oxide. The trick to using nanoparticles made of pure iron is the thin coating of iron oxide, which prevents the core from completely oxidizing into rust.
The particles can be created in exact sizes, ranging from two nanometers to 100 nanometers in diameter. At their largest, scientists still could fit 100 million nanoparticles on the head of a pin. At their smallest, a pin head could fit 250 billion.
The project will explore a process applied to the MNPs that allows the tiny pieces of iron to selectively grab on to radioactive metals belonging to the actinides group of elements. The nanoparticles are coated by an organic molecule that acts like glue for other chemicals, in this case holding alkyl-oxa-diamide. This long-named chemical compound works like Velcro, grabbing and holding tennis balls. Except in this case, the tennis balls actually are radioactive metal ions.
Because the MNPs have such a high magnetic momentum, a small magnetic field selectively can yank the MNPs with attached radioactive molecules out of the nuclear waste. Once separated, a process breaks the bonds, separating the actinides from the nanoparticles, both of which can be reused.
"The process uses environmentally friendly chemical molecules," said Qiang, "The MNPs are not toxic and can even be reused many times. The process does not produce any secondary waste."
Qiang originally created the MNPs for biomedical purposes and sees them being used to improve cancer detection with magnetic resonance imaging (MRI), as miniature heaters to attack malignant cells or as high precision drug delivery devices.
Despite the original purpose, when Qiang saw a presentation about nuclear separation technology at a DOE meeting in early 2006, he immediately recognized the possibilities. He approached Rao at the conference, and collaboration was born.
Qiang has the expertise in magnetism to create the nanoparticles, Paszczynski and Rao specialize in designing and putting the organic link between particle and actinide. Also, Rao has the nuclear expertise and facilities to work with the extremely dangerous substances.
"We need a nuclear specialist, physicist and organic biochemist to even make the right experiments," said Paszczynski. "It truly is an interdisciplinary research group."
The group currently is researching how to confirm that the nanoparticles have attached and are holding to the desired actinide. They also must investigate how the MNP's magnetic properties change once it is attached and also how to release the radioactive material once separated from the spent fuel.
The developing technology is superior to current nuclear separation technologies in many ways. Some current techniques result in impurities in the final product while others generate significant amounts of hazardous secondary waste.
"You not only have to have a good idea - a good project - you also have to be willing to work together," said Paszczynski. "Qiang and I have worked very well together for several years, and because we also developed good relations with Dr. Rao's research group, we're hoping this will be a long-term, successful project."