New device could help scientists design new fuel reprocessing methods

Oct 20, 2011 By Louise Lerner
Argonne scientists Artem Guelis (right) and Kevin Nichols test their miniaturized apparatus for nuclear recycling research.

Designing better ways to recycle spent nuclear fuel could make nuclear energy a safer solution to the global energy problem, but there are a lot of gaps in our chemical knowledge -- and it's difficult to get those answers when the experiments involve radioactive material.

Scientists at the U.S. Department of Energy's (DOE) Argonne National Laboratory have one answer: Shrink the whole experiment down—to microliters.

When it comes out of a reactor, nuclear spent fuel contains a whole glut of different radioactive isotopes, all mixed together.

For years, scientists have looked for ways to separate out reusable fuel from the truly toxic stuff.

The nations that recycle spent nuclear fuel today use processes based on PUREX, a technique whose underpinnings date back to the 1940s. Ideally, new processes would make fuel recycling cheaper, safer and less complex.

But one big challenge to creating models that accurately represent fuel reprocessing lies in determining the rates of reaction in the procedure—essentially, how quickly different elements move between phases.

Recycling nuclear fuel is fundamentally a sorting exercise: chemists want to sift out the useful uranium from the bulk of other byproducts and highly radioactive ones. The fuel is dissolved in acid and different metals can be separated out using solvent extraction—a bit like oil collecting on the surface of a bottle of salad dressing. The rates at which the metals separate is determined by kinetics, and knowing the rates helps scientists design new and better techniques.

"From the chemistry standpoint, if we want to be able to design new and improved nuclear recycling schemes, you have to be able to understand the mechanism," said Argonne chemical engineer Kevin Nichols, who helped lead the research. "You have to be able to develop chemical insight, which comes from knowing the kinetics."

Previous experiments that looked into the kinetics of these particular classes of reactions used large volumes of material, which slows the process and leads to less accurate results. But Nichols and chemist Artem Gelis have built a solution: an apparatus that miniaturizes the process.

"If we cut the size down, we can do the same experiment much more quickly, generate less waste and get more precise measurements," Gelis explained.

The apparatus uses mere drops of radioactive material, rather than liters. This allows hundreds or even thousands of trials to be performed with just a few microliters of sample.

The new process grew out of a combination of solvent extraction research being done at Argonne and work being done by University of Chicago professor Rustem Ismagilov, whose laboratory created a miniaturized apparatus for protein crystallization. The process generated thousands of aqueous droplets containing proteins separated by an oil layer, which—as it happens—is similar to the process for nuclear recycling. Though it had not been tried before, the researchers decided to modify the technique for treatment kinetics.

Next, the team is planning to adapt the technique for other applications, such as processes that produce radioactive isotopes for medical use or even rare earth metal processing.

Rare earth metals are used in many energy technologies, such as solar panels and compact fluorescent lightbulbs, but today are primarily mined in China. The U.S. has rare earth metal deposits, but the popularity of renewable energy has triggered new interest in making U.S. rare earth metal mining more economical.

Explore further: Chemists characterize 3-D macroporous hydrogels

More information: The paper, "Toward Mechanistic Understanding of Nuclear Reprocessing Chemistries by Quantifying Lanthanide Solvent Extraction Kinetics via Microfluidics with Constant Interfacial Area and Rapid Mixing", was published in the Journal of the American Chemical Society and is available online.

Related Stories

U.S. to fund nuclear fuel center design

May 10, 2007

The U.S. Department of Energy will provide up to $60 million for the design of a nuclear fuel recycling center and advanced recycling reactor.

Plutonium in troubled reactors, spent fuel pools

Mar 18, 2011

(AP) --The fuel rods at all six reactors at the stricken Fukushima Dai-ichi complex contain plutonium - better known as fuel for nuclear weapons. While plutonium is more toxic than uranium, other radioactive ...

Recommended for you

Chemists characterize 3-D macroporous hydrogels

1 hour ago

Carnegie Mellon University chemists have developed two novel methods to characterize 3-dimensional macroporous hydrogels—materials that hold great promise for developing "smart" responsive materials that ...

Substrates change nanoparticle reactivity

7 hours ago

(Phys.org)—Nanoscale materials tend to behave differently than their bulk counterparts. While there are many theories as to why this happens, technological advances in scanning tunneling microscopy (STM) ...

Reviving cottonseed meals adhesives potential

9 hours ago

Cottonseed meal—the leftovers after lint and oil are extracted from cottonseed—is typically fed to ruminant livestock, such as cows, or used as fertilizer. But Agricultural Research Service scientists ...

New concrete composite can heal itself

10 hours ago

In the human body, small wounds are easily treated by the body itself, requiring no further care. For bigger wounds to be healed, the body may need outside assistance. Concrete is like a living body, in that ...

Actuators that mimic ice plants

10 hours ago

Engineers developing moveable robot components may soon take advantage of a trick plants use. Researchers at the Max Planck Institute of Colloids and Interfaces in Potsdam and Harvard University in Cambridge ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.