A new stable form of plutonium discovered at the ESRF

October 18, 2019

An international team of scientists, led by the Helmholtz Zentrum Dresden-Rossendorf (HZDR), have found a new compound of plutonium with an unexpected, pentavalent oxidation state, using the ESRF, the European Synchrotron, Grenoble, France. This new phase of plutonium is solid and stable, and may be a transient phase in radioactive waste repositories. The results are published this week in Angewandte Chemie as a Very Important Paper (VIP).

Countries across the globe are making efforts to improve the safety of the nuclear waste storage in order to prevent release of radioactive nuclides to the environment. Plutonium, has been shown to be transported by groundwaters from contaminated sites for kilometres in the form of colloids, which are formed by interaction with clay, iron oxides or natural organic matter. A team of scientists lead by HZDR studies the chemistry of actinides under environmentally relevant conditions, by synthesizing such compounds, and then studying their electronic and structural behaviour both with advanced synchrotron X-ray methods experimentally as well as theoretically.

The latest paper of the international team shows how an experiment seemingly gone wrong leads to a breakthrough: the discovery of a new stable form of plutonium.

It all started when Kristina Kvashnina, physicist from HZDR and based at the ROBL beamline at the European Synchrotron - ESRF (a beamline owned and operated by the HZDR), and her team were trying to create plutonium dioxide nanoparticles using different precursors to be studied at ROBL. When they used the Pu (VI) precursor, they realized that a strange reaction took place during the formation of the plutonium dioxide nanoparticles. "Every time we create nanoparticles from the other precursors Pu(III), (IV) or (V) the reaction is very quick, but here we observed a weird phenomenon half way", explains Kvashnina. She figured that it must be Pu (V), pentavalent plutonium, a never-observed-before form of the element, after doing a high-energy resolution fluorescence detection (HERFD) experiment at the Pu L3 edge at ROBL.

Stable phase of Pu(V)! - no, it is impossible, it doesn't exist, the synthesis must have gone wrong", said, at the time, the team of chemists, from the Moscow State University when they all together looked at the data. "Chemists were in complete disbelief, but the results were quite clear", Kvashnina adds.

The only way to be certain of the existence of this pentavalent compoundwould be to confirm it using HERFD at the Pu M4 edge. Kvashnina explains: "Our choice of beamline was straightforward: ESRF-ID26 beamline, as it is the best place, regarding the intensity and energy resolution, where such high-energy resolution x-ray absorption spectroscopy studies at low energies can be done. In fact Pu M4 edge HERFD experiment was done at ID26 for the first time. To the best of our knowledge, HERFD data at the Pu M4 edge have never been reported in the literature and never been exploited".

The experiments confirmed the initial assumption, and a repetition three months later even demonstrated the long-term stability of the phase.. At the same time, theoreticians in Sweden were busy coming up with predictions of the Pu M4 edge spectral features and theoreticians from ROBL identified the species of that new phase. In the end it all came together and the new Pu (V) phase was confirmed.

Many scientists work on prediction of what happens to the nuclear waste in million years. "It is a difficult task and only theoretical predictions are possible, but the existence of this new Pu(V) solid phase, which is stable, will have to be taken into account from now on. It will change, for sure, the theoretical predictions of plutonium behaviour in the environment over a period of million years", concludes Kvashnina.
-end-


European Synchrotron Radiation Facility

Related Nuclear Waste Articles from Brightsurf:

Reducing radioactive waste in processes to dismantle nuclear facilities
Margarita Herranz, professor of nuclear engineering at the UPV/EHU, leads one of the working groups in the Europe H2020 INSIDER project.

Nuclear medicine and COVID-19: New content from The Journal of Nuclear Medicine
In one of five new COVID-19-related articles and commentaries published in the June issue of The Journal of Nuclear Medicine, Johnese Spisso discusses how the UCLA Hospital System has dealt with the pandemic.

Are salt deposits a solution for nuclear waste disposal?
Researchers testing and modeling to dispose of the current supply of waste.

Taking a bite out of food waste: Scientists repurpose waste bread to feed microbes
Food waste is a serious economic and environmental problem. Researchers have developed a protocol using waste bread as a medium to grow microorganisms for the fermented food industry.

Current model for storing nuclear waste is incomplete
The materials the United States and other countries plan to use to store high level nuclear waste will likely degrade faster than anyone previously knew, because of the way those materials interact, new research shows.

Unused stockpiles of nuclear waste could be more useful than we might think
Chemists have found a new use for the waste product of nuclear power -- transforming an unused stockpile into a versatile compound which could be used to create valuable commodity chemicals as well as new energy sources.

Researchers perfect nanoscience tool for studies of nuclear waste storage
Studying radiation chemistry and electronic structure of materials at scales smaller than nanometres, the University of Guelph team prepared samples of clay in ultra-thin layers.

Deep learning expands study of nuclear waste remediation
A research collaboration between Berkeley Lab, Pacific Northwest National Laboratory, Brown University, and NVIDIA has achieved exaflop performance with a deep learning application used to model subsurface flow in the study of nuclear waste remediation.

Nuclear physics -- probing a nuclear clock transition
Physicists have measured the energy associated with the decay of a metastable state of the thorium-229 nucleus.

Electrospun sodium titanate speeds up the purification of nuclear waste water
Electrospun sodium titanate speeds up the purification of water based on selective ion exchange -- effectively extracts radio-active strontium.

Read More: Nuclear Waste News and Nuclear Waste Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.