Is it possible to speed up radioactive decay by squeezing atoms?
In the last few months, Fabio Cardone, at the Institute of
Nanostructured Materials, in Rome, Italy, and a few pals have posted on
the arXiv a growing body of evidence that it is.
In March, Cardone and co reported an increase in neutron emissions when crushing marble and granite. Their conjecture is that the crushing causes the piezonuclear fission of iron atoms into two aluminum nuclei emitting two neutrons.
But our focus today is a paper published in February, in which the team reported that cavitation–the generation and collapse of tiny bubbles in a liquid using pressure waves–causes the rate of decay of thorium-228 in solution to increase 1,000 times.
I guess it’s not entirely beyond belief that cavitation could have an effect on the nuclei
of atoms in solution. Cavitation is known to generate huge pressures and temperatures. By some theories, the energy released in this process is close to that needed for fusion. But it’s fair to say that the current consensus is that there is no good evidence that this line has been crossed in practice.
Nevertheless, Cardone’s claims are interesting, and his paper was published in Physics Letters A earlier this year.
Today, however, Stephan Pomp and pals from Uppsala University, in Sweden, cast some doubt on the result and the methods used by the Cardone team in the Physics Letters A paper.
They point out that the Cardone claim is extraordinary given the body of evidence gathered over the past 100 years about nuclear decay. Such an extraordinary claim should be backed by extraordinary evidence.
“We find that such evidence is missing in this paper and it even seems that methodological mistakes have been made,” they say.
Thorium decays by emitting alpha particles. Pomp and pals say that Cardone and co placed their detector underneath the glass vessel containing the thorium solution. “We note that the range of the emitted particles in glass is in the order of tens of micrometers and that it thus would be impossible for particles … to penetrate the vessel.”
They suggest a number of tests that Cardone and co can do to strengthen their results, such as measuring the background counts when the vessel is empty or filled with pure water in which cavitation is taking place.
It’ll be interesting to see the Cardone team’s reply to these criticisms; perhaps they’ll be able to answer each point made by Pomp and pals.
In the meantime, the question still stands: can pressure waves accelerate nuclear decay? Not on the evidence presented by Cardone and co so far.
arxiv.org/abs/0903.3104 Piezonuclear Neutrons from Fracturing of Inert Solids
arxiv.org/abs/0710.5177: Speeding Up Thorium Decay
arxiv.org/abs/0907.0623: Comments on “Piezonuclear Decay of Thorium” by F. Cardone et al.