Fission and Fusion
Nuclear energy is released by the splitting (fission) or merging (fusion) of the nuclei of atom(s). The conversion of nuclear mass-energy to a form of energy, which can remove some mass when the energy is removed, is consistent with the mass-energy equivalence formula ΔE = Δmc², in which ΔE = energy release, Δm = mass defect, and c = the speed of light in a vacuum (a physical constant). When this equation is used in this way, the mass "changes" only because it is removed from the system, not because it is converted or destroyed (the removed binding energy retains and accounts for the missing mass, which is a conserved quantity).
Nuclear energy was first discovered by French physicist Henri Becquerel in 1896, when he found that photographic plates stored in the dark near uranium were blackened like X-ray plates (X-rays had recently been discovered in 1895).
Nuclear chemistry can be used as a form of alchemy to turn lead into gold or change any atom to any other atom (though this may require many intermediate steps). Radionuclide (radioisotope) production often involves irradiation of another isotope (or more precisely a nuclide), with alpha particles, beta particles, or gamma rays. Nickel-62 has the highest binding energy per nucleon of any isotope. If an atom of lower average binding energy is changed into an atom of higher average binding energy, energy is given off. The chart shows that fusion of hydrogen, the combination to form heavier atoms, releases energy, as does fission of uranium, the breaking up of a larger nucleus into smaller parts. Stability varies between isotopes: the isotope U-235 is much less stable than the more common U-238.
Nuclear energy is released by three exoenergetic (or exothermic) processes:
- Radioactive decay, where a neutron or proton in the radioactive nucleus decays spontaneously by emitting either particles, electromagnetic radiation (gamma rays), neutrinos (or all of them)
- Fusion, two atomic nuclei fuse together to form a heavier nucleus
- Fission, the breaking of a heavy nucleus into two (or more rarely three) lighter nuclei
Read more about this topic: Nuclear Binding Energy
Famous quotes containing the words fission and/or fusion:
“The pace of science forces the pace of technique. Theoretical physics forces atomic energy on us; the successful production of the fission bomb forces upon us the manufacture of the hydrogen bomb. We do not choose our problems, we do not choose our products; we are pushed, we are forced—by what? By a system which has no purpose and goal transcending it, and which makes man its appendix.”
—Erich Fromm (1900–1980)
“Sadism and masochism, in Freud’s final formulation, are fusions of Eros and the destructive instincts. Sadism represents a fusion of the erotic instincts and the destructive instincts directed outwards, in which the destructiveness has the character of aggressiveness. Masochism represents the fusion of the erotic instincts and the destructive instincts turned against oneself, the aim of the latter being self-destruction.”
—Patrick Mullahy (b. 1912)