The contribution of radioactivity to pyrophoricity in actinids

6 thoughts on “The contribution of radioactivity to pyrophoricity in actinids”

  1. Dear Florent, if I could draw your attention to the second par in this letter ( to the US NRC regarding the return of waste US DU from the UK’s 120mm CHARM DU production process. You will note that the swarf/turnings – the waste from the machining process for penetrators – are stored in mineral oil. Why? Because not doing so leaves them exposed to air and risks them spontaneously combusting, because DU, like U, LEU and HEU is pyrophoric. A property that has little to do with its radiological characteristics but everything to do with its chemical properties. Naturally you may view this as an extremely elaborate hoax, which is of course far more exciting than campaigning on the facts.


  2. It is possible that depleted uranium is slightly, or moderately, pyrophoric. It has its own alpha radioactivity (even if 235U is six times more radioactive than 238U) and thus some degree of internal heat. But the chemist I met really told me that 235U made the difference, and this appears also clearly in the patents I have found (they leave no doubt on that). The fact is that depleted uranium pyrophoricity itself was not studied by researchers, they studied the pyrophoricity of uranium which includes 235U. Clearly the presence of U235 is key in the pyrophoricity phenomenon and you should not be negating this. The ICBUW should not be excluding deliberately non-depleted uranium from its campaigning (even though its name actually suggest it could be campaigning on “uranium weapons” as a whole). And, more importantly, people should know that it is 235U, for instance in reactive materials, that is used to burn alive people (to put it bluntly) and this is the information that the ICBUW should be sharing. This is why I beg you to change your stance on that topic and to get in touch with chemists that will explain you the importance of 235U in the pyrophoricity of uranium.

  3. As I told you by Twitter I think that what makes actually the difference is not U235, as I thought, but U234 (see article ). Yes, depleted uranium is pyrophoric, but natural uranium is more pyrophoric, this is a scientific certainty. It happens because of the higher latent heat of uranium 234 (and U235 contributes a little bit). This latent heat is the activation energy ( see here : ) of the combustion reaction. Even though a reaction can lead to a more stable state (lower in energy), this reaction may not happen because of the energy barrier that has to be broken through. It’s like path dependence…

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