| 单词 | nuclear fission |
| 释义 | nuclear fission A nuclear reaction in which a heavy nucleus (such as uranium) splits into two parts (fission products ), which subsequently emit either two or three neutrons, releasing a quantity of energy equivalent to the difference between the rest mass of the neutrons and the fission products and that of the original nucleus. Fission may occur spontaneously or as a result of irradiation by neutrons. For example, the fission of a uranium–235 nucleus by a slow neutron may proceed thus: 235U + n →148La + 85Br + 3n The energy released is approximately 3 × 10-11 J per 235U nucleus. For 1 kg of 235U this is equivalent to 20 000 megawatt-hours – the amount of energy produced by the combustion of 3 × 106 tonnes of coal. Nuclear fission is the process used in nuclear reactors and atom bombs (see nuclear weapons) |
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