What is nuclear bombs made up of?

Answer 1

• active material (fissile and/or fusible materials)
• conventional explosives
• electronics (timing/firing circuits, fusing circuits, arming/safeing circuits, permissive action link or equivalent)
• metal and/or composite ballistic casing (might be steel or aluminum, in missile warheads an ablative resin/fiber composite heat shield is used too)
• etc.

The active material provides the nuclear energy of the weapon. For fission bombs it is either Uranium or Plutonium. For fusion bombs it is normally Lithium Deuteride. There are many bomb designs that combine fission and fusion: a boosted fission bomb uses a hollow sealed fissile core that is filled with either deuterium gas, tritium gas, or a mix of both to get a small fusion yield, which causes a higher fission yield; the traditional fusion bomb involves several "cycles" of fission and fusion to work resulting in it usually being referred to as a fission-fusion-fission bomb, with typically 90% or more of its yield actually coming from the final fission step (not fusion).

Answer 2

Nuclear bombs consist of either fissile materials like uranium-235 or plutonium-239. A critical mass of these materials is required to initiate a chain reaction, leading to a powerful explosion caused by the release of nuclear energy. The bomb also includes conventional explosives to trigger the nuclear reaction and enhance the blast effect.