A nuclear bomb can be built with a relatively small amount of nuclear material. A trained nuclear engineer with an amount of highly enriched uranium or plutonium about the size of grapefruit or an orange, together with commercially available material, could fashion a nuclear device that would fit in a van like one Ramzi Yousef parked in the garage of the World Trade Centrer in 1993. Such a bomb would level Lower Mahnattan.
於Shadow Masters一書,第220頁,迪米特曾解釋:
The problem arises when you try to join two pieces of uranium. Once you get them close to each other, and their corresponding neutron fields overlap, a slow nuclear reaction will start, instantly heating up these pieces of uranium. So when you try to get them closer, they will overheat, melt, and evaporate. You won’t be able to actually join these two pieces together, because they will always evaporate before you could get them to physically touch each other. Therefore, to join the two sub-critical masses of uranium into one over-critical mass required for the nuclear explosion, they need to converge at very high speed – 2.5km/sec. Only then, you have a chance for these two pieces to join before the slow nuclear reaction evaporates them.