• Question: What is inside of nuclear bombs?

    Asked by ands520agee to Tina-Jaine H, Stephen M, Ruth, oliviawilliams, michaeltaylor, graemesutcliffe, M, Calum, Alana M on 18 Dec 2024.
    • Photo: Michael Taylor

      Michael Taylor answered on 18 Dec 2024:

      Nuclear bombs are complex and their construction and operation is often kept confidential. What we can say is the essence of a nuclear bomb is to utilise the processes of nuclear fission (also used in electricity production) or nuclear fusion (the process that powers the Sun) to release vasts amount of energy to cause as much destruction as possible.

    • Photo: Tina-Jaine Haigh

      Tina-Jaine Haigh answered on 24 Jan 2025: last edited 24 Jan 2025 14:27

      The full answer to that is highly secret, and I don’t know. But you can get some idea if you understand how fission or fusion work. Some bombs use fission, some use fusion.
      In a fission reaction (usually using uranium or plutonium because they are very big atoms), for each atom that splits apart, it releases approximately 3 neutrons. Those neutrons have the potential to bump into other atoms and trigger them to fission. So 1 atom fissioning could lead to 3 atoms fissioning, then 9, then 27, then 71 and so on. All in less than a nanosecond. So the reaction rate can grow very rapidly. The reaction rate is all about how much energy is created per second.
      In a nuclear power station this would mean the reaction running out of control. That is prevented by using the control rods which absorb spare neutrons such that just 1 neutron from each fission triggers 1 more fission, and the reaction stays at a steady rate. In a fission bomb, they want the reaction to turn out of control and go very rapidly. So they just start the reaction and let it go nuts.
      Fusion requires bringing the nuclei of small atoms close enough together that they can bond together to make bigger atoms. They bond together by the “weak nuclear force” which makes protons attract protons, or protons attract neutrons, or neutrons attract neutrons. But at the same time, the electromagnetic force is pushing the protons away from each other, because they are both positively charged. The weak nuclear force only works over very short distances. The electromagnetic force works over much longer distances. The weak nuclear force is much stronger than the electromagnetic force only when the 2 nuclei are very close together. The rest of the time, the electromagnetic force pushing them apart is much stronger. So you have to be able to push past the whole range where the electromagnetic force dominates, to the point where the weak nuclear force dominates and pulls them together.
      In a fusion reactor, it’s a kind of particle accelerator, which sets the nuclei moving so fast they can bump into each other very hard and push past the repulsion of the electromagnetic force. In a fusion bomb, there isn’t room for a particle accelerator (have you seen how big ITER is?). They have to push the nuclei together by different means.

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