another complexity is that the plutonium core is not just any weapon-grade plutonium: it has to be casted in unstable delta phase (which has unusually low densi

another complexity is that the plutonium core is not just any weapon-grade plutonium: it has to be casted in unstable delta phase (which has unusually low density; the implosion's task is to switch it into alpha-phase which is much dense: this process makes core critical and explosion happens). Not to mention toxicity of the material itself.