[Southack]

"And, finally, plutonium will go critical all by itself in relatively small quantities. You have to be careful not to pile too much plutonium up in one spot because it will go off." - calenel

Not according to this site:
In order to start the chain reaction, the mass of plutonium must be fused together while a radioactive source emitted a neutron.

[calenel]

"Not according to this site: In order to start the chain reaction, the mass of plutonium must be fused together while a radioactive source emitted a neutron."

Read a little more closely. The "mass of plutonium" is a bunch of separate plutonium pieces that need to be "fused" by being pushed together and held together long enough to go supercritical instead of just going critical and scattering itself around the room. Also, note that the article you referenced also states the mass of plutonium required for a plutonium-only bomb, and that it can be made to go supercritical with conventional explosives that were available in the 1940s. There is no mention of exotic isotopes of artificial elements or the like. It even describes the trigger used and the time required to hold the plutonium together. It then goes on to mention the accessories, such as an altimeter (now why would we need that?) That article actually supports my side of this debate.