New stable form of plutonium discovered

""A stable phase of Pu(V)! - no, it is impossible, it doesn't exist, the synthesis must have gone wrong," said the team of chemists, from the Moscow State University when they 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 compound would be to confirm it using HERFD at the Pu M4 edge. Kvashnina explains: "Our choice of beamline was straightforward: the 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 the 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 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 millions of years," concludes Kvashnina."

[link to m.phys.org (secure)]