How is a nuke made?

Answer 1

There are two technically difficult aspects of making a nuclear weapon. First, you have to have a sufficient amount known as a critical mass, of some fissile material, usually plutonium or the U235 isotope of uranium. Secondly, you have to have a mechanism that will bring together the two halves of the fissile material extremely rapidly. If they do not come together rapidly enough, instead of the desired chain reaction you just get a lot of heat, and the device melts (much like a melt-down of a nuclear reactor). That's the key. I will leave the details to you.

Answer 2

A nuclear weapon is typically made by enriching uranium or plutonium to high levels of fissile material. This enriched material is then used in a controlled chain reaction to release a large amount of energy in the form of a nuclear explosion. The design and construction of nuclear weapons are highly classified and tightly regulated by international agreements to prevent their proliferation.