If an isotope(such as uranium 235) can support fission, one might say it is fissile. What would you call a material like deuterium can support fusion, what would you call it?


2 Answers 2


U-235 and Pu-239 are fissile, or fissionable, as are other isotopes (e.g., U-233, Pu-241). D and T are fusionable. I don't think fusionable is used very much, but see Patents, Fusionable Material Target, http://www.google.com/patents/US20060198487. "Can support fission" or "can support fusion" is a strange wording. Better to say "can undergo nuclear fission" or "can undergo nuclear fusion." I could go on, but I won't.

Upon reflection, "can support nuclear fission" is OK for U-235 and Pu-239. Wilipedia defines fissile as "In nuclear engineering, fissile material is material capable of sustaining a nuclear fission chain reaction. By definition, fissile material can sustain a chain reaction with neutrons of any energy." Of course, a lot of engineering goes into the sustaining or supporting part, but it has been achieved. As for fusion, we don't have fusion reactors yet.

  • For such an arcane technical question, we'd need someone from the field to tell us what they actually not. Not sort of "nice interesting thoughts on it" as you and I have offered here, ab :)
    – Fattie
    Commented Aug 20, 2015 at 1:48
  • @Joe Blow It's not as arcane as some of the English language questions! But it is more nuclear engineering than physics. It's not fusible and fusionable -- both are OK -- it is the exact implications of "support".
    – ab2
    Commented Aug 20, 2015 at 1:52

Isn't it



Realistically, just ask on the physics site. Highly technical questions are not really for this site.

BTW I'm not entirely sure if "fissile" literally is used to mean "can support fission".

  • fusible is fine...as good as and maybe better than fusionable. There are also patents on fusible..."Neutron generator using compressed fusible material and laser pulse US 20100290574 A1"
    – ab2
    Commented Aug 20, 2015 at 1:45
  • 1
    Fusible normally means able to be fused by heat/melting. The issue is that fissile is defined by what's practical in a nuclear reactor, rather than meaning what can be fissioned in theory. When people start routinely fusing nuclei, we may find fusible is more common with that sense.
    – Stuart F
    Commented Mar 27 at 10:03

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