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Nuclear Weapons

A nuclear weapon is an explosive device that derives its destructive force from nuclear reactions, either just using fission (as in the first 'atomic' bombs) or using a combination of fission and fusion - as in 'hydrogen' bombs.

Nuclear reactions release vast quantities of energy from relatively small amounts of matter. A critical mass of fissile material is required. The mass of some of the matter is converted into energy. See binding energy.

Nuclear weapons require highly enriched nuclear material. This is done in a centrifuge.

The first fission (atomic) bomb test released the same amount of energy as approximately 20,000 tons of TNT.

The first thermonuclear (hydrogen) bomb test released the same amount of energy as approximately 10,000,000 tons of TNT... 500 times the destructive power!

Deployment of nuclear weapons

The only nuclear weapons that have been used in a war were early fission weapons:

The bomb dropped on Hiroshima in August 1945 was a uranium gun-type assembly 'atom' bomb. It had the codename 'Little Boy'. Approximately 600 to 860 milligrams of matter in the bomb was converted into photons of electromagnetic energy. It exploded with an energy of 16 kilotons of TNT (67 TJ).
The bomb dropped on Nagasaki three days after the Hiroshima bomb was a plutonium implosion-type fission bomb code-named 'Fat Man'. It exploded with an energy of 21 kilotons of TNT (88 TJ).

Since the bombings of Hiroshima and Nagasaki, nuclear weapons have been detonated on over two thousand occasions but only for testing purposes and demonstrations. It is estimated (in 2012) that there are over 17,000 nuclear warheads in the world, with around 4,300 of them considered ready for use or 'operational'. all of today's nuclear weapons have far more destructive power than the ones used in World War II.