<Gun-type fission weapons> don't work with <Plutonium-239> because of the presence of <Plutonium-240> as an impurity which leads to <fizzle (nuclear explosion)>.

Good mentions at: https://youtu.be/dgBDvnqMkT4?t=252


Gun-type fission weapons don't work with plutonium

{wiki}

This <isotope> shows up as an inevitable contaminant in <Plutonium-239> for <nuclear weapons>, because it emits <neutrons> too fast and makes it harder to assemble the critical mass without <fizzle (nuclear explosion)>.

It is the presence of this contaminant that made <implosion-type fission weapon> a necessity: <Gun-type fission weapons don't work with plutonium>{full}.

<Wikipedia> explains that Pu-240 is formed by Pu-239 <Neutron> capture:
> About 62% to 73% of the time when \sup[239]Pu captures a neutron, it undergoes fission; the remainder of the time, it forms 240Pu.
so its presence is inevitable.


Ciro Santilli @cirosantilli 37

 Incoming links: Fizzle (nuclear explosion)