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How Do Nuclear Bombs Work?

Atoms are made up of three subatomic particles

  • Positively charged protons in the nucleus
  • Neutrally charged neutrons in the nucleus
  • Negatively charged electrons orbit the nucleus

When the ratio of protons to neutrons is 1:1, the atom has a neutral charge

  • Isotope: when the number of neutrons changes

Radioactive Particles

  • When the nucleus is not neutrally charged, it emits particles called radiation through radioactive decay
  • Atomic bombs form by destabilizing the particle through fission and fusion


  • Splits the nucleus of an atom in two by overloading it with neutrons
  • As the nucleus splits it ejects neutrons along with bursts of electromagnetic energy
    • This energy is called gamma rays
  • Uranium is the most cooperative in inducing a fission chain reaction
  • U-235 can be forced to undergo fission by bombarding it with neutrons
  • As one U-235 undergoes fission, it ejects 2-3 neutrons which cause fission in other U-235 atoms, inducing a chain reaction and bursts of gamma rays
  • This happens in magnitudes of Picoseconds


  • Merges the nucleus of two atoms together to form a larger nucleus
  • The clash of nuclei produces energy
  • The sun does this

Critical Mass: the minimum amount of material needed to sustain a chain reaction

  • In order to harness nuclear power, the nuclear fuel has to be kept in separate subcritical masses so fission doesn’t happen until induced
  • When detonated, the subcritical masses are brought together to form a supercritical mass
  • Additional neutrons are also added to kick off the chain reaction
    • Polonium and Beryllium combined form a neutron generator used for detonation


  • The entire reaction is contained within this – neutrons bounce back into the core after hitting the walls of this container
  • As fission happens the neutrons start bouncing faster and faster within the tamper, building up a more dramatic outburst of energy that eventually breaks through the tamper
  • This material is usually made of U-238

Gun-Triggered Bomb (Fission)

  • A bullet filled with U-235 is packed on one side of a tube
  • Explosives fire the bullet down the tube where it collides with the neutron generator
  • This kicks off the fission chain reaction
  • Little Boy (Hiroshima bomb) used this mechanism
    • It was 1.5% efficient – 1.5% of the material fissioned before detonation

Implosion-Triggered Bomb (Fission)

  • Contains a sphere of radioactive U-235 as the tamper around a Plutonium-239 core
  • The sphere is surrounded by explosives
  • When explosives detonate, a shockwave presses the core and initiates the fission chain reaction
  • Fat Man (Nagasaki bomb) used this mechanism
    • It was 17% efficient

Thermonuclear/Hydrogen Bomb (Fission + Fusion)

  • Uses hydrogen isotopes Deuterium and Tritium as fuel
  • Contains a tamper made of U-238
  • Tamper is packed with hydrogen isotope fuel
  • The tamper surrounds a hollow rod of Plutonium-239 at the core
  • An implosion fission device detonates first → this compresses the fuel and causes the plutonium core to fission
  • The rod starts to fission → it gives off heat and pressure → this initiates fusion in the hydrogen isotopes → leads to the explosion
  • This process takes 600 billionths of a second and creates 700x the power of the Little Boy

Delivery Methods

  • Ballistic Missiles: exit the atmosphere and travel long distance before denotation
  • Cruise Missiles: shorter-range missiles that travel a couple of thousand miles
  • Tactical Weapons: artillery shells, land mines, etc

Radioactive Aftermath

  • After detonation, clouds of radioactive particles get carried by the wind to settle in surrounding areas
  • These radioactive particles poison the water supply, which cycles into vegetation, food sources, biodiversity, etc
  • Radioactive particles affect human cells that readily divide: hair, gut cells, bone marrow, reproductive organs, etc

Raw Material Supply

  • Uranium-235 is needed for nuclear weapons, but it does not occur naturally
  • Instead, U-235 can be formed by enriching U-238 (a natural resource)
  • U-238 can be bought commercially in powders called “Yellow Cake”
  • To build 1 nuclear bomb, 6.6 tons of Yellow Cake has to be bought, stored, and enriched
  • To enrich U-238, it has to reach a very fast speed that can only be done through a sophisticated centrifuge
    • The supply of this centrifuge is controlled by the Nuclear Suppliers Group
  • After U-235 is produced, the bomb can be designed and built (this cycle can take years)
  • After the bomb is designed, water, hydrofluoric acid, and magnesium are used to convert the gaseous U-235 into solid-state metal
  • This metal is shaped and refined to fit into the bomb
Koko Xu

Lover of international cuisines and Class B chess player.