Scientists and collaborators at the Lawrence Livermore National Laboratory (LLNL) have proposed a new mechanism by which nuclear waste could spread in the environment. Researchers at Penn State and Harvard Medical School are also involved in the research. The new findings have implications for nuclear waste management and environmental chemistry. The results of the research have been published in the Journal of the American Chemical Society.
Gauthier Deblonde is a LLNL scientist and lead author of the report on the new research. He said, “This study relates to the fate of nuclear materials in nature, and we stumbled upon a previously unknown mechanism by which certain radioactive elements could spread in the environment. We show that there are molecules in nature that were not considered before, notably proteins like 'lanmodulin' that could have a strong impact on radioelements that are problematic for nuclear waste management, such as americium, curium, etc.”
Past and present nuclear activities like fundamental research, energy generation, and nuclear weapons development have increased the urgency to understand the behavior of radioactive materials in the environment. Nuclear wastes contain actinides such as plutonium, americium, curium, neptunium and other radioactive isotopes which are particularly problematic because they remain radioactive and dangerous for thousands of years.
Unfortunately, very little is known about the chemical forms of these elements in the environment. This forces scientists and engineers to utilize models to predict their long-term behavior and migration patterns. Up to the present, these models have only been able to consider interactions with small natural compounds, mineral phases and colloids. The impact of more complex compounds such as proteins has mostly been ignored. The new research demonstrates that a type of protein that is abundant in nature vastly outcompetes molecules that scientists previously considered as the most problematic with respect to actinide migration in the environment.
Joseph Cotruvo Jr., is a Penn State assistant professor and co-corresponding author on the paper. He said, “The recent discovery that some bacteria specifically use rare earth elements has opened new areas of biochemistry with important technological applications and potential implications for actinide geochemistry, because of chemical similarities between the rare earths and actinides”.
The protein named lanmodulin is a small and abundant protein in many rare earth-utilizing bacteria. It was discovered by the Penn State members of the research team in 2018. The LLNL and Penn State team have studied in detail exactly how this unique protein works and how it can be applied for the commercial extraction of rare earths. However, the relevance of the protein to radioactive contaminants in the environment was previously unexplored.
Annie Kersting is a LLNL scientist. She said, “Our results suggest that lanmodulin, and similar compounds, play a more important role in the chemistry of actinides in the environment than we could have imagined. Our study also points to the important role that selective biological molecules can play in the differential migration patterns of synthetic radioisotopes in the environment.”
Mavrik Zavarin is also a LLNL scientist. He said, “The study also shows for the first time that lanmodulin prefers the actinide elements over any other metals, including the rare earth elements, an interesting property than could be used for novel separation processes.”
Rare earth element biochemistry is a very recent field that Penn State and LLNL have helped to pioneer. The new work is first to explore how the environmental chemistry of actinides could be connected to nature’s use of rare earth elements. Lanmodulin’s higher affinity for actinides may even mean that rare earth-utilizing organisms that are ubiquitous in nature might preferentially incorporate certain actinides into their biochemistry, according to Deblonde.