Fission Or Fusion :: essays research papers

Fission or conglutination     I think that right now, nuclear fission is the only way that we muckle get moreenergy out of a nuclear chemical reaction than we put in. First, the energy per fissionis very large. In practical units, the fission of 1 kg (2.2 lb) of uranium-235releases 18.7 million kilowatt-hours as heat. Second, the fission processinitiated by the absorption of one neutron in uranium-235 releases about 2.5neutrons, on the average, from the split nuclei. The neutrons released in thismanner quickly cause the fission of two more atoms, thereby releasing four ormore additional neutrons and initiating a independent series of nuclearfissions, or a chain reaction, which results in never-ending release of nuclearenergy. Naturally occurring uranium contains only 0.71 percent uranium-235 the residuum is the non-fissile isotope uranium-238. A mass of natural uranium byitself, no count how large, washstandnot sustain a chain reaction because only theuran ium-235 is easily fissionable. The probability that a fission neutron withan initial energy of about 1 MeV go forth induce fission is rather low, besides can be change magnitude by a factor of hundreds when the neutron is long-windeded down through aseries of elastic collisions with light nuclei such as hydrogen, deuterium, orcarbon. This fact is the foothold for the design of practical energy-producingfission reactors.     In December 1942 at the University of Chicago, the Italian physicistEnrico Fermi succeeded in producing the first nuclear chain reaction. This wasdone with an sight of natural uranium lumps distributed within a largestack of unadulterated graphite, a form of carbon. In Fermis "pile," or nuclear reactor,the graphite moderator served to slow the neutrons.     Nuclear concretion was first achieved on earth in the earlier 1930s bybombarding a target containing deuterium, the mass-2 isotope of hydrogen, withhigh -energy deuterons in a cyclotron. To accelerate the deuteron beam a greatdeal of energy is required, intimately of which appeared as heat in the target. As aresult, no terminate useful energy was produced. In the 1950s the first large-scalebut lordless release of fusion energy was demonstrated in the tests of atomic weapons by the United States, the USSR, Great Britain, and France.This was such a brief and uncontrolled release that it could not be used for theproduction of electric power.     In the fission reactions I discussed earlier, the neutron, which has noelectric charge, can easily get along and react with a fissionable nucleus ,forexample, uranium-235. In the typical fusion reaction, however, the reactingnuclei both have a positive electric charge, and the natural antagonism betweenthem, called Coulomb repulsion, must be overcome before they can join.