2. Very Heavy Nucleus Light Nucleus 85-104 u Heavy Nucleus 130-149 u Other Particles BACKHOMENEXT

3. U235 n La Mo HOMENEXT BACK

4. Light Nuclei Heavier Nucleus 33 BACK HOME NEXT

5. d + d + n He Two heavy hydrogen nuclei,deuterons,combine to form a nucleus of helium n BACK HOME NEXT 3

6. Now we will see an animation of a nuclear fission reaction. We will see how a neutron can cause fission of Uranium nucleus.We will also see controlled and uncontrolled chain reactions

15. Nuclear Energy, energy released during the splitting or fusing of atomic nuclei. The quantities of energy that can be obtained from the nucleus far exceed those that can be obtained from chemical processes, which involve only the outer regions of the atom. BACK HOME NEXT

16. Nuclear energy can be released in two different ways: by fission (splitting) of a heavy nucleus, or by fusion (combining) of two light nuclei. BACKHOME NEXT

17. In both cases energy is released because the products have a higher binding energy than the reactants. Fusion reactions are difficult to maintain because the nuclei repel each other, but, unlike fission reactions, fusion reactions create far less radioactivity. BACKHOMENEXT

18. Nuclear energy, measured in millions of electronvolts (MeV), is released by the fusion of two light nuclei, as when two heavy hydrogen nuclei, deuterons ( ª H), combine in the reaction producing a helium-3 nucleus, a free neutron ( ¦ n), and 3.2 MeV, or 5.1 × 10 -13 J. BACK HOME NEXT

19. Nuclear energy is also released when the fission of a heavy nucleus such as ¯ U is induced by the absorption of a neutron, as in BACKHOMENEXT

20. producing caesium-140, rubidium- 93, three neutrons, and 200 MeV, or 3.2 × 10 -11 J. A nuclear fission reaction releases 10 million times as much energy as is released in a typical chemical reaction. BACK HOME NEXT

21. Now you will see how a controlled chain reaction is used in a Nuclear Reactor to produce electricity.

27. Nuclear Energy," Microsoft® Encarta® Encyclopedia 2000. © 1993-1999 Microsoft Corporation. All rights reserved.