- When a neutron strikes the nucleus of an atom of uranium -235 it causes the nucleus to split into two fragments, each with half the number of protons and neutrons
- This splitting releases a great amount of thermal energy as well as gamma rays and two or more neutrons
- Then, under certain conditions, the neutrons strike other atoms which creates more fission and release of thermal energy
- These rapid fission reactions create a chain reaction in which almost all of the fissionable material is consumed, this process creates an explosion that is known as an atomic bomb
- Uranium-235, which is found naturally at a ratio of about one part per every 139 parts of the isotope uranium-238, undergoes fission more readily and emits more neutrons per fission than other isotopes
- For this to happen, the fissionable material must be brought to a critical state extremely suddenly
- A method used is that of implosion, in which a core of fissionable material is suddenly compressed into a smaller size and thus a greater density
- Because it is denser, the nuclei are more tightly packed and the chances of an emitted neutron’s striking a nucleus are increased.
- The core of an implosion-type atomic bomb consists of a sphere of fissionable material surrounded by a jacket of high explosives, which, being simultaneously detonated, implode the fissionable material under enormous pressures into a denser mass
- When completely fissioned, 1 kg (2.2 pounds) of uranium-235 releases the energy equivalently produced by 17,000 tons of TNT
- The detonation of an atomic bomb releases enormous amounts of thermal energy achieving temperatures that are million degrees in the exploding bomb itself
- The first atomic bomb to be used in warfare used uranium, it was called "little boy"
- It was dropped by the United States on Hiroshima, Japan, on August 6, 1945
- The explosion, which had the force of more than 15,000 tons of TNT, instantly and completely devastated 11.4 square km (4.4 square miles) of the heart of this city of 343,000 inhabitants
- By the end of the year the death toll had surpassed 100,000 and 67% of the city’s structures had been destroyed or damaged