Physical overview Mechanism įission product yields by mass for thermal neutron fission of uranium-235, plutonium-239, a combination of the two typical of current nuclear power reactors, and uranium-233 used in the thorium cycle. The industry term for a process that fissions all or nearly all actinides is a " closed fuel cycle". Nuclear reprocessing aims to recover usable material from spent nuclear fuel to both enable uranium (and thorium) supplies to last longer and to reduce the amount of "waste". All actinides are fertile or fissile and fast breeder reactors can fission them all albeit only in certain configurations. U - or rather its decay products - are a major gamma ray emitter. The thorium fuel cycle produces virtually no plutonium and much less minor actinides, but 232 Concerns over nuclear waste accumulation and the destructive potential of nuclear weapons are a counterbalance to the peaceful desire to use fission as an energy source. U) whose radiotoxicity is far higher than that of the long lived fission products. Neutron absorption which does not lead to fission produces Plutonium (from 238 However, the seven long-lived fission products make up only a small fraction of fission products. The products of nuclear fission, however, are on average far more radioactive than the heavy elements which are normally fissioned as fuel, and remain so for significant amounts of time, giving rise to a nuclear waste problem.
#Instant egg head fusion vs fission free
The amount of free energy contained in nuclear fuel is millions of times the amount of free energy contained in a similar mass of chemical fuel such as gasoline, making nuclear fission a very dense source of energy. This makes a self-sustaining nuclear chain reaction possible, releasing energy at a controlled rate in a nuclear reactor or at a very rapid, uncontrolled rate in a nuclear weapon. Both uses are possible because certain substances called nuclear fuels undergo fission when struck by fission neutrons, and in turn emit neutrons when they break apart. Nuclear fission produces energy for nuclear power and drives the explosion of nuclear weapons. The unpredictable composition of the products (which vary in a broad probabilistic and somewhat chaotic manner) distinguishes fission from purely quantum tunneling processes such as proton emission, alpha decay, and cluster decay, which give the same products each time. Spontaneous fission was discovered in 1940 by Flyorov, Petrzhak, and Kurchatov in Moscow, in an experiment intended to confirm that, without bombardment by neutrons, the fission rate of uranium was negligible, as predicted by Niels Bohr it was not negligible. The smallest of these fragments in ternary processes ranges in size from a proton to an argon nucleus.Īpart from fission induced by a neutron, harnessed and exploited by humans, a natural form of spontaneous radioactive decay (not requiring a neutron) is also referred to as fission, and occurs especially in very high-mass-number isotopes. Most fissions are binary fissions (producing two charged fragments), but occasionally (2 to 4 times per 1000 events), three positively charged fragments are produced, in a ternary fission. The two (or more) nuclei produced are most often of comparable but slightly different sizes, typically with a mass ratio of products of about 3 to 2, for common fissile isotopes. Like nuclear fusion, for fission to produce energy, the total binding energy of the resulting elements must be greater than that of the starting element.įission is a form of nuclear transmutation because the resulting fragments (or daughter atoms) are not the same element as the original parent atom. In their second publication on nuclear fission in February of 1939, Hahn and Strassmann predicted the existence and liberation of additional neutrons during the fission process, opening up the possibility of a nuclear chain reaction.įor heavy nuclides, it is an exothermic reaction which can release large amounts of energy both as electromagnetic radiation and as kinetic energy of the fragments ( heating the bulk material where fission takes place). Frisch named the process "fission" by analogy with biological fission of living cells. Physicists Lise Meitner and her nephew Otto Robert Frisch explained it theoretically in January 1939. Nuclear fission was discovered on 19 December 1938 in Berlin by German chemists Otto Hahn and Fritz Strassmann. The fission process often produces gamma photons, and releases a very large amount of energy even by the energetic standards of radioactive decay. Nuclear fission is a reaction in which the nucleus of an atom splits into two or more smaller nuclei.
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