By: LaVonje White
Intro to Nuclear Weapons
A nuclear weapon is an explosive device that develops its destructive force from nuclear reactions, either fission (fission bomb) or a combination of fission and fusion (thermonuclear weapon). Both reactions release vast magnitudes of energy from reasonably small amounts of matter. 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 quantity of energy as approximately 10,000,000 tons of TNT.
All existing nuclear weapons derive some of their explosive energy from nuclear fission reactions. Weapons whose explosive output is exclusively from fission reactions are commonly referred to as atomic bombs or atom bombs. This has long been noted as something of a contradiction, as their energy comes from the nucleus of the atom, just as it does with fusion weapons.
In fission weapons, a mass of fissile material is assembled into a supercritical mass—the amount of material needed to start an exponentially growing nuclear chain reaction—either by shooting one piece of sub-critical material into another or by compressing using explosive lenses a sub-critical sphere of material using chemical explosives to many times its original density. The latter approach is considered more sophisticated than the previous and only the latter approach can be used if the fissile material is plutonium.
A most important challenge in all nuclear weapon designs is to make certain that a significant fraction of the fuel is disbursed before the weapon destroys itself. The amount of energy released by fission bombs can range from the equivalent of just under a ton of TNT, to upwards of 500,000 tons of TNT.
Altogether fission reactions essentially generate fission products, the radioactive remains of the atomic nuclei split by the fission reactions. Many fission products are either highly radioactive; but short-lived, or moderately radioactive; but long-lived, and as such are a serious form of radioactive pollution if not completely controlled. Fission products are the principal radioactive component of nuclear fallout.