Weapons of mass destruction which are powered by atomic processes, produce large explosions and hazardous radioactive byproducts by means of either nuclear fission or nuclear fusion are called nuclear weapons. Artillery, plane, ship, or ballistic missile (ICBM) are used to deliver nuclear weapons. Tactical nuclear weapons can have the explosive power of a fraction of a kiloton (one kiloton equals 1,000 tons of TNT), while strategic nuclear weapons can produce thousands of kilotons of explosive force. Proliferation is an increasing cause of concern throughout the world. Majority of these weapons are held by the United States and the USSR are held by Great Britain, France, China, India, and Pakistan. Over a dozen other countries can, or soon could, make nuclear weapons. In the 1970s scientists started investigating the potential impact of nuclear war on the environment in addition to the consequences of radioactive material. Nuclear winter the word used for describing the collective effects environmental damage.
Countries with Nuclear Weapons Capability :
Acknowledged Nuclear Weapons Capability : The United States, Britain, China, France, India, Pakistan, Russia.
Unacknowledged Nuclear Weapons Capability : Israel
Seeking Nuclear Weapons Capability : Iran, Iraq
Abandoned Nuclear Weapons Development: North Korea, South Africa.
Stockpiles of nuclear weapons :
| Countries | Stockpiles of Nuclear Weapons (approx) |
| Russian Federation | 22,000 |
| U.S.A | 12,000 |
| France | 482 |
| China | 410 |
| Britain | 200 |
| Israel | 100 |
| India | 60 |
| Pakistan | 15-25 |
| Iran | 4 |
Reactions that power the destructive force of the weapons and their designs are the criteria used to classify the nuclear weapons. The popular criteria of classifying nuclear weapons into fission bombs and fusion bombs is unsatisfactory.
Atomic bombs (A-bombs), hydrogen bombs (H-bombs), fission bombs, fusion bombs, thermonuclear weapons are the common names used to describe nuclear weapons.
From the initial stages, "atomic bomb" is the term used to describe nuclear weapons. However this name is somewhat misleading since all chemical explosives generate energy from reactions between atoms - that is, between intact atoms consisting of both the atomic nucleus and electron shells.
Both fission and fusion weapons release energy through transformations of the atomic nucleus, and hence general term for all types of these explosive devices is "nuclear weapon".
Fusion weapons are called "hydrogen bombs" (H-bombs) because isotopes of hydrogen are principal components of the nuclear reactions involved. Deuterium (hydrogen-2) was the sole fusion fuel used in the beginning. Fusion weapons are called "thermonuclear weapons" because high temperatures are required for the fusion reactions to occur.
Pure Fission Weapons Fission reactions are used as a source of energy in pure fission weapons which operate by rapidly assembling a subcritical configuration of fissile material like Plutonium or enriched Uranium into one that is highly supercritical. The original atomic bombs tested on 16 July 1945 at Trinity and dropped on Japan on 6 August 1945 (Little Boy over Hiroshima) and 9 August 1945 (Fat Man over Nagasaki) were pure fission weapons.
These nuclear weapons are the easiest to design and manufacture, and are regarded as elementary nuclear weapons.
The size of pure fission bombs have practical limits as the larger size requires more fissionable material, which is is difficult to maintain as a subcritical mass before detonation and makes it harder to assemble into a high efficiency supercritical mass before stray neutrons cause predetonation.
Combined Fission/Fusion Weapons
Weapons other than pure fission weapons use fusion reactions to enhance their destructive effects. To initiate the fusion reactions, fission bomb is used.
Boosted Fission Weapons
In boosted fission weapons a few grams of a deuterium/tritium gas mixture are included in the center of the fissile core. When the bomb core undergoes enough fission, it becomes hot enough to ignite the D-T fusion reaction which proceeds swiftly. This reaction produces an intense burst of high-energy neutrons that causes a correspondingly intense burst of fissions in the core. This greatly accelerates the fission rate in the core, thus allowing a much higher percentage of the material in the core to fission before it blows apart. By accelerating the fission process a boosted fission bomb increases the yield by 100%.
Most fission bomb s are boosted to take advantage of increasing yield, reducing weight of the fission system and eliminating the risk of predetermination.
Staged Radiation Implosion Weapons
These are classified as fission-fusion or fission-fusion-fission weapons. These are less costly as they contain lesser amount of enriched Uranium or Plutonium and isotopes of light elements like Hydrogen and Lithium.
It is a two stage bomb; the primary stage is fission trigger and the secondary stage is fusion reaction. X-rays from the primary stage are used to compress the secondary stage through a process known as radiation implosion. The secondary is then ignited by a fission spark plug in its centre. Multiple staging to produce larger bombs is possible. Fusion and fission reactions physically seperate from each other. The fusion reactions occur in a package of a fusion fuel in the secondary.
The fusion reactions are used to boost the yield through direct release of a large amount of energy in fusion reactions; and by using high-energy or "fast" neutrons generated by fusion to release energy through fission of a fissionable jacket around the fusion stage.
Fission-fusion weapons are bombs that release a significant amount of energy by fusion but do not use fusion neutrons to fission the fusion stage jacket. If they employ the additional step of jacket fissioning using fusion neutrons they are called Fission-Fusion-Fission weapons.
The Alarm Clock/Sloika (Layer Cake) Design
This idea was invented independently, at least three times; by Edward Teller in the United States, who named the design "Alarm Clock", Andrei Sakharov and Vitalii Ginzburg in the Soviet Union who called it the "sloika" design. A sloika is a layered Russian pastry, and has thus been translated as "Layer Cake". Finally it was developed by the British (inventor unknown).
"Layer Cake" uses a spherical assembly of concentric shells. In the center is a fission primary made of U-235/Pu-239, surrounding it is an optional layer of U-238 for the fission tamper, then a layer of lithium-6 deuteride/tritide, a U-238 fusion tamper, and finally the high explosive implosion system. The process begins like an ordinary implosion bomb. After the primary in the center completes its reaction, the energy it releases compresses and heats the fusion layer to thermonuclear temperatures. The burst of fission neutrons then initiates a coupled fission-fusion-fission chain reaction.
Neutron Bombs
Neutron bombs, are referred to as "enhanced radiation (ER) warheads", are small thermonuclear weapons in which the burst of neutrons generated by the fusion reaction is intentionally not absorbed inside the weapon, but allowed to escape. The principle destructive mechanism is the intense burst of high-energy neutrons. Neutrons are more penetrating than other types of radiation, so many shielding materials that work well against gamma rays do not work nearly as well. The term "enhanced radiation" refers only to the burst of ionizing radiation released at the moment of detonation.
The use of deuterium-tritium gas mixture as the only fusion fuel distinguishes neutron bombs from other thermonuclear weapons. The D-T thermonuclear reaction releases 80% of its energy as neutron kinetic energy, and it is also the easiest of all fusion reactions to ignite.
The U.S. developed and produced three neutron warheads, a fourth was cancelled prior to production. All have been retired and dismantled. The Soviet Union, China, and France are all known to have developed neutron bomb designs and may have them in service. Israel may also have developed neutron bombs.
Cobalt Bombs and other Salted Bombs
A "salted" nuclear weapon is similar to fission-fusion-fission weapons, but instead of a fissionable jacket around the secondary stage fusion fuel, a non-fissionable blanket of a specially chosen salting isotope is used. Cobalt-59 is used in cobalt bombs. This blanket captures the escaping fusion neutrons to breed a radioactive isotope that maximizes the fallout hazard from the weapon rather than generating additional explosive force (and dangerous fission fallout) from fast fission of U-238.
Variable fallout effects can be obtained by using different salting isotopes. like :
| Parent Isotope | Natural Abundance | Radioactive Product | Half-Life |
| Cobalt-59 | 100% | Co-60 | 5.26 years |
| Gold-197 | 100% | Au-198 | 2.697 days |
| Tantalum-181 | 99.99% | Ta-182 | 115 days |
| Zinc-64 | 48.89% | Zn-65 | 244 days |
See Also :
Effects
Fission
Fusion
J.Oppenheimer
Leo Szilard
Albert Einstein
Related Links :
Cost
and Consequences of US nuclear weapon projects.
Nuclear
Warfare and survival.
Nuclear,
biological and chemical weapons.
Simulation
of an abandoned cold war weapon site.