A typical nuclear reactor uses only a small fraction of its fuel rod to produce power before the energy-generating reaction naturally terminates. What is left behind is an assortment of radioactive elements, including unused fuel, that are disposed of as nuclear waste in the United States. Although certain elements recycled from waste can be used for powering newer generations of nuclear reactors, extracting leftover fuel in a way that prevents possible misuse is an ongoing challenge.
Now, Texas A&M University engineering researchers have devised a simple, proliferation-resistant approach for separating out different components of nuclear waste. The one-step chemical reaction, described in the February issue of the journal Industrial & Engineering Chemistry Research, results in the formation of crystals containing all of the leftover nuclear fuel elements distributed uniformly.
The researchers also noted that the simplicity of their recycling approach makes the translation from lab bench to industry feasible.
“Our recycling strategy can be easily integrated into a chemical flow sheet for industrial-scale implementation,” said Johnathan Burns, research scientist in the Texas A&M Engineering Experiment Station’s Nuclear Engineering and Science Center. “In other words, the reaction can be repeated multiple times to maximize fuel recovery yield and further reduce radioactive nuclear waste.”
For their experiments, they prepared a surrogate solution of uranium, plutonium, neptunium and americium in highly concentrated nitric acid at 60-90 degrees Celsius to mimic dissolving of a real fuel rod in the strong acid. They found when the solution reached room temperature, as predicted, that uranium, neptunium, plutonium and americium separated from the solution together, uniformly distributing themselves within the crystals.
Burns noted that this simplified, single-step process is also proliferation-resistant since plutonium is not isolated but incorporated within the uranium crystals.
“The idea is that the reprocessed fuel generated from our prescribed chemical reaction can be used in future generations of reactors, which would not only burn uranium like most present-day reactors but also other heavy elements such as neptunium, plutonium and americium,” Burns said. “In addition to addressing the fuel recycling problem and reducing proliferation risk, our strategy will drastically reduce nuclear waste to just the fission products whose radioactivity is hundreds rather than hundreds of thousands of years.”