NUCLEAR FUELS. • • • • • • • • • • • • • • • The source of energy in nuclear fuel is nuclear fission reaction . Both mass and energy remain conserved in nuclear fission reaction. Loss in mass is converted into energy. The study of nuclear fuel is important bcuz energy changes involved are many million times greater than in chemical fuel. ★ Nuclear Reaction:- In nuclear reaction the nucleus of an atom undergoes a change forming new atoms and releasing a huge amount of energy. The enormous amount of energy evolved in a nuclear reaction is due to the conversion of some of the mass into energy. A nuclear reaction is not affected by the changes in temperature and pressure. A nuclear change is irreversible. A nuclear reaction equation is balanced by making atomic number ( lower figures on the symbols) equal on both sides and also by making the mass numbers (upper figures on the symbols) equal on both the sides of equation taken separately. For example, conversion of nitrogen into oxygen can be represented as. 14/7 N(Nitrogen) + 4/2 He(x Particle)→17/8 O (Oxygen)+ 1/1 H(Proton). Sum of atomic numbers →Reactants 7+2 = 9 →Products 8+1 = 9. Sum of atomic masses → Reactant 14+4 = 18 → Products 17 +1 = 18. ★ Types of Nuclear rection:- ** Nuclear Fission- The process in which an unclear of a heavy atom( like uranium 235) splits up into two medium weight unclei with the liberation of an enormous amount of energy is called nuclear fission. It is carried out by bombarding the heavy nuclei with neutron. Fission reaction of Uranium-235 can be written as. 235/92 U + 1/0 n → 139/56 B a + 94/36 Kr + 3 1/0 n + large amount of energy. A large amount of energy is liberated during nuclear fission bcuz of a loss in mass, which is converted into equivalent amount of energy, in accordance with einsteins mass - energy equation ▲E = ▲m c2. Mostly in all fission reaction, neutrons are emitted. The number of neutrons resulting from a single fission is known as the multiplication factor. As the multiplication factor is greater than one the number of fission reaction increases for each successive neutron generation. If this chain reaction is not controlled it will proceed uninterrupted and a tremendous amount of energy will be released in a fraction of a second, which can lead to a nuclear explosion. If this chain reaction is controlled it can lead to power generation in a device called a nuclear reactor. ** Nuclear Fusion- Nuclear fusion is a process in which two lighter nuclei combine to form a heavy, more stable nucleus with the liberation of large amount of energy. When two deuterium atoms are heated to a very high temperature, then they fuse together to form a heavy nucleus of helium and an enormous amount of energy is liberated. 2/1 H+2/1 H→4/2 He + Enormous amount of energy As the fusion process involves combination of two positively changed nuclei which repel each other, it occurs at extremely high temperatures bcuz at such high temperatures (4×10^6° C) nuclei have sufficiently high kinetic energies to overcome the repulsion and they undergo fusion to from a bigger nucleus. Such high temperature can be attained by using the heat evolved in a fission reaction but in this way the fusion of hydrogen gets out of control and leads to explosion. There is greater loss of mass in fusion reaction than in a fission reaction and hence the amount of energy liberated in a fusion reaction is much more than that liberated in a fission reaction. The nuclear fusion reactions are relatively clean since the products of fusion reaction are not radioactive.
Posted on: Mon, 27 Oct 2014 15:30:09 +0000
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