Atomic Bomb


How it works

When an element such as plutonium or uranium hits neutrons, an atomic nucleus is split into two fragments and release fission energy. A single nuclear fission can only release a little energy but neutrons released in nuclear fission produce an additional fission with another nucleus. This nuclear chain reaction releases a gigantic energy (heat rays, atomic blast, radiation). Atomic bomb uses this energy as a weapon.


Atomic Bombs used in Nagasaki and Hiroshima

In order to explode an atomic bomb, a certain amount of fissile material, called critical mass, is necessary. The fissile material used in Hiroshima was uranium-235. Inside the bomb, uranium-235 was divided into two pieces, both of which are below critical mass. Using an explosive device, the two uranium-235 were brought together to form a critical mass that exploded instantaneously. This is known as a gun-barrel-type bomb.

The fissile material used in Nagasaki was plutonium-239. Inside the bomb, the plutonium-239 is divided into subcritical portions surrounded by gunpowder. When it is detonated, the conventional explosives squeeze the plutonium core in on itself to achieve a supercritical mass. This is known as an implosion type bomb


  • Length: 3.25m
  • Diameter: 1.52m
  • Weight: 4.5tons
  • Explosive force: equivalent to 21,000 tons of TNT

It was nick-named "fat man"


  • Length: 3m
  • Diameter: 0.7m
  • Weight: 4tons
  • Explosive force: equivalent to 15,000 tons of TNT

It was nick-named "little boy"