Mitigating Radioactive Waste with Nanomaterials

As the tools available become more precise and develop new capabilities, discoveries arise that are surprising.  Sometimes, this occurs by accident as happened by scientists in Germany, Russia, and Sweden.  The report [Ref. #1] indicate the scientists found a chemically stable compound containing plutonium.  Specifically, the team led by Kristina Kvashnina at the Helmholtz Center Dresden-Rossendorf found that a compound containing plutonium in its fifth oxidations state can remain stable for “long” periods of time.  The team created nanoparticles of plutonium-oxide atoms in different oxidation states. 

 “One of the most fundamental properties of the chemical behavior of plutonium is the variety of its oxidation states.  The oxidation state is defined by the number of electrons that are removed from the valence orbitals of a neutral atom.  In the pentavalent oxidation state, plutonium has three electr4ons in the 5f shell, leaving the 6d orbitals empty. The oxidation state of plutonium determines its chemical behavior and its reactivity.” [Ref. 2]

The team observed the resultant particle structure using X-ray equipment at the European Synchrotron Radiation Facility in Grenoble, France.  They found that the theory agreed with the rapid formation of the plutonium-oxide nanoparticles in its third, fourth, and fifth states.  The sixth oxidation state proved to be different and appeared to have a two-step process that took some time to complete.

The conclusion was that the time lengthening could be due to a stable form of the fifth state.  This had not been observed experimentally before.  Theoretically, if this is correct, it would be possible for the particles could remain stable over months, which would be a major change in our understanding of the chemical properties of nuclear material, particularly nuclear waste.  The team did additional experimentation using high-energy resolution fluorescence and confirmed that a stable form of the fifth oxidation state has actually be observed.  They further confirmed the compound’s stability by drying it our of liquid suspension and measuring the absorption spectrum over time. 

 So, what is the significance of a stable state of plutonium-oxide? 

One of the most significant issues facing the nuclear power industry is the disposal of “spent” radioactive material for reactors.  Plutonium plays a prominent role in nuclear energy production as well as nuclear weapons.  The development of storage methods for nuclear waste is challenging to say the least.  With various materials capable of remaining radioactive for tens of thousands of years, the design of containment that will safeguard the material is difficult.  There are ongoing studies on ways to mitigate the long-term effects of the radioactive material.  This research may provide researchers a methodology to create nanomaterials that mitigate the effects of the radioactive materials by converting them into stable compounds.  This work provides a new method of evaluating was to handle long-term storage of radioactive waste.

References:

  1. https://physicsworld.com/a/surprisingly-stable-plutonium-compound-could-affect-nuclear-waste-storage/
2.      “A Novel Metastable Pentavalent Plutonium Solid Phase on the Pathway from Aqueous Plutonium(VI) to PuO2 Nanoparticles ” https://onlinelibrary.wiley.com/doi/10.1002/anie.201911637

About Walt

I have been involved in various aspects of nanotechnology since the late 1970s. My interest in promoting nano-safety began in 2006 and produced a white paper in 2007 explaining the four pillars of nano-safety. I am a technology futurist and is currently focused on nanoelectronics, single digit nanomaterials, and 3D printing at the nanoscale. My experience includes three startups, two of which I founded, 13 years at SEMATECH, where I was a Senior Fellow of the technical staff when I left, and 12 years at General Electric with nine of them on corporate staff. I have a Ph.D. from the University of Texas at Austin, an MBA from James Madison University, and a B.S. in Physics from the Illinois Institute of Technology.

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