Nuclear weapons energy release

The process of nuclear fission was discovered more than half a century ago in 1938 by Lise Meitner (1878-1968) and Otto Hahn (1879-1968) in Germany. With the outbreak of World War II a year later, interest focused on the enormous amount of energy released in the process. At Los Alamos, in the mountains of New Mexico, a group of scientists led by J. Robert Oppenheimer (1904-1967) worked feverishly to produce the fission, or atomic, bomb. Many of the members of this group were exiles from Nazi Germany. They were spurred on by the fear that Hitler would obtain the bomb first Their work led to the explosion of the first atomic bomb in the New Mexico desert at 5 30 a.m. on July 16,1945. Less than a month later (August 6,1945), the world learned of this new weapon when another bomb was exploded... 

Airborne poisons in the nuclear weapons progam were not limited to radioactive materials released from weapons. The weapons technology involved the use of many exotic materials, some of which were toxic (e.g., beryllium). Hazardous releases of these materials occurred in industrial settings in urban areas and were studied by the Atomic Energy Commission as occupational and public health problems. 

A single kilogram of radioactive metallic plutonium-238 produces as much as 22 million kilowatt-hours of heat energy. Larger amounts of Pu-238 produce more heat. However, Pu-238 is not fissionable, and thus it cannot sustain a chain reaction. However, plutonium-239 is fissionable, and a 10-pound ball can reach a critical mass sufficient to sustain a fission chain reaction, resulting in an explosion, releasing the equivalent of over 20,000 tons of TNT. This 10-pound ball of Pu-239 is only about one-third the size of fissionable uranium-235 required to reach a critical mass. This makes plutonium-239 the preferred fissionable material for nuclear weapons and some nuclear reactors that produce electricity. 

Nuclear weapons which usually use nuclear fusion, have far greater yields than weapons, which use only fission, as fusion releases more energy per kilogram and can also be used as a source of fast neutrons to cause fission in depleted uranium. 

Although the transient test was orders of magnitude below a nuclear weapon in regard to energy release and temperature achieved, the debris showed many similarities to fallout. These included not only the size and appearance of the particles but also the correlation properties of various radionuclides. Dissimilarities in the correlations and the variation of specific activity with particle type confirm expectations of the importance of escape processes to the formation mechanisms for this type of debris. This study shows that data-correlation techniques developed for fallout characterization are also useful in studying reactor debris. 

A nuclear reactor is a device in which nuclear chain reactions are initiated, controlled, and sustained at a steady rate. Nuclear reactors are used for many purposes, but the most significant current uses are for the generation of electrical power and for the production of plutonium for use in nuclear weapons. Currently, all commercial nuclear reactors are based on nuclear fission. The amount of energy released by one kg 235U is equal to the energy from the combustion of 3000 tons of coal or the energy from an explosion of 20,000 tons of TNT (Trinitrotoluene, called commonly dynamite). 

Nuclear Explosions Although conventional explosives have become the weapons of choice of terrorist groups, a joint report issued in 2008 by Harvard s Kennedy School of Government and the Nuclear Threat Initiative reminds us that there is a real danger that terrorists could get and use a nuclear weapon.16 In order to understand what this would mean, we return to the atomic nucleus. A nuclear fission reaction releases far more energy than any ordinary chemical process. The Oklahoma City bomb was equivalent to the explosion of approximately 40001b of TNT.17 In contrast, the atomic bomb dropped on... 

This fission reaction starts with the splitting of just one U-235 nucleus. This reaction releases three neutrons that can then split three uranium nuclei, which give off nine neutrons, which split nine uranium nuclei, and so on. This process is called a chain reaction, and once started, it continues until all of the uranium is split. With each step in the chain reaction, three times more energy is released than in the previous step in the reaction. This explains why a nuclear weapon releases so much energy. 

A typical example is the way nuclear weapons were defined in the Treaty of Tlatelolco. Article 5 of that treaty reads For the purpose of this Treaty, a nuclear weapon is any device which is capable of releasing nuclear energy in an uncontrolled manner and which has a group of characteristics that are appropriate for use for warlike purposes. Any instrument that may be used for the transport or propulsion of the device is not included in this definition if it is separable from the device and not an indivisible part of it (emphasis added). 

For use in nuclear weapons, the concentration of °Pu in the plutonium should be low, because the presence of this nuclide leads to the production of appreciable amounts of neutrons by spontaneous fission if the concentration of °Pu is too high the neutron multiplication would start too early with a relatively small multiplication factor, and the energy release would be relatively low. Higher concentrations of " Pu also interfere, because of its transmutation into " Am with a half-life of only 14.35 y. To minimize the formation of " °Pu and " Pu, Pu for use in weapons is, in general, produced in special reactors by low bum-up (<20 000 MWth d per ton). 

Nuclear weapons are explosive devices that release nuclear energy. An individual nuclear device may have an explosive force equivalent to millions of tons (megatons) of trinitrotoluene (TNT, the chemical explosive traditionally used for such comparisons), and is more than enough to inflict devastating physical damage to a city. 

The destructive power of nuclear weapons derives from the core of the atom, the nucleus. One type of nuclear weapon, the fission bomb, uses the energy released when nuclei of heavy elements such as plutonium fission (split apart). A second even more powerful type of nuclear weapon, the fusion or hydrogen bomb, uses the energy released when nuclei of hydrogen are united (fused together). 

Conventional, chemical explosives get their power from the rapid rearrangement of chemical bonds, the links between atoms made by sharing electrons. In chemical explosives, atoms dissociate from other atoms and form new associations this releases energy, but the atoms themselves do not change. Nuclear weapons are based on an entirely different principle. They derive their explosive power from changes in the structure of the atom itself, specifically, in the core of the atom, its nucleus. 

Because hydrogen is lighter than uranium, more hydrogen atoms fit into a sample of the same weight. Thus, even though one fusion reaction releases less energy than one fission reaction, more hydrogen than uranium atoms can be packed into a nuclear weapon and many more fu-... 

Atomic bomb— An explosive weapon which uses uranium-235 or plutonium as fuel. Its tremendous destructive power is produced by energy released from the "splitting of atoms" or nuclear fission. Also called A-bomb, atom bomb, or fission bomb. 

Hydrogen bomb—An nuclear explosive weapon which uses hydrogen isotopes as fuel and an atom bomb as a detonator. More powerful than an atom bomb, the Hydrogen bomb derives its destructive power from energy released when nuclei of hydrogen are forced together to form helium nuclei in a process called nuclear fusion. Also called H-bomb or Thermonuclear bomb. 

Nuclear weapon— A bomb or other explosive that derives it explosive force from the release of nuclear energy. PlutoniumA heavy, rare natural element that undergoes fission in a nuclear bomb. It is produced artificially by bombarding uranium-238 with neutrons. The addition of one neutron to the nucleus of uranium-238 changes it into plutonium-239 which is called "weapons grade plutonium," the most efficient form for making weapons. 

In all, 193 experiences nucleaires (nuclear tests and safety trials) were conducted at the French nuclear weapon test site at Mururoa and Fangataufa atolls. Of these, 178 were nuclear tests , in which a nuclear device was exploded with a large release of fission and, in some cases, fusion energy and 15 were safety trials in which more or less fully developed nuclear devices were subjected to simulated accident conditions and the nuclear weapon cores were destroyed by means of conventional explosives, with no or—on a few occasions—very small releases of fission energy. 

LaRosa, J., Danesi, P.R., Fajgelj, A., Makarewicz, M., Vajda, N., Valkovic, V., Zeisler, R., Stegnar, P., Analytical approach to the measurement of radionuclides in environmental contamination of a former nuclear weapon testing area, presented at International Symposium on Environmental Impact of Radioactive Releases, International Atomic Energy Agency, Vienna, 8-12 May 1995. 

---