Section 24-3

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Nuclear Fission. Stability of elements is best around a mass number of 60. Atoms with a mass number greater than 60 tend to gain stability by fragmenting. The splitting of nuclei into fragments is known as nuclear fission. Fission is accompanied with a very large release of energy. - PowerPoint PPT Presentation

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<ul><li><p>Section 24-3Nuclear FissionStability of elements is best around a mass number of 60.Atoms with a mass number greater than 60 tend to gain stability by fragmenting.The splitting of nuclei into fragments is known as nuclear fission.Fission is accompanied with a very large release of energy.</p></li><li><p>Section 24-3Nuclear FissionNuclear power plants use fission to produce electricity by striking uranium-235 with neutrons.</p></li><li><p>Section 24-3Nuclear Fission (cont.)Each fission of U-235 releases three additional neutrons.Each of those neutrons can release three more neutrons.The self-sustaining process is called a chain reaction. http://glencoe.mcgraw-hill.com/sites/007874637x/student_view0/chapter24/concepts_in_motion.html </p></li><li><p>Section 24-3Nuclear Fission (cont.)</p></li><li><p>Section 24-3Nuclear Fission (cont.)There must be sufficient mass to get the chain reaction started. If not the neutrons escape before striking other nuclei.Without sufficient mass, neutrons escape from the sample before starting a chain reaction.Samples with enough mass to sustain a chain reaction are said to have critical mass.Samples with mass that is much greater than the critical mass have a reaction that escalates at a violent level and can cause a nuclear explosion. This is the supercritical mass. </p></li><li><p>Section 24-3Nuclear Fission (cont.)http://www.youtube.com/watch?v=qybUFnY7Y8w </p></li><li><p>Section 24-3Nuclear ReactorsNuclear fission produces the energy generated by nuclear reactors.The fission within a reactor is started by a neutron-emitting source and is stopped by positioning the control rods to absorb virtually all of the neutrons produced in the reaction.</p></li><li><p>Section 24-3Nuclear Reactors (cont.)The reactor core contains a reflector that reflects neutrons back into the core, where they react with fuel rods.Nuclear reactors produce highly radioactive nuclear waste.Breeder reactors produce more fuel than they consume.</p></li><li><p>Section 24-3Nuclear Reactors (cont.)</p></li><li><p>Section 24-3Nuclear FusionIt is possible to bind together two or more lighter elements (mass number less than 60).The combining of atomic nuclei is called nuclear fusion.Nuclear fusion is capable of releasing very large amounts of energy.The sun is powered by the fusion of hydrogen atoms to form helium atoms and a lot of energy.</p></li><li><p>Section 24-3Nuclear Fusion (cont.)Fusion has several advantages over fission.Lightweight isotopes are abundant.Fusion products are not radioactive.However, fusion requires extremely high energies to initiate and sustain a reaction.</p></li><li><p>Section 24-3Nuclear Fusion (cont.)Fusion reactions are also known as thermonuclear reactions.Many problems must be solved before nuclear fusion is a practical energy source.</p></li><li><p>Section 24-3ABCDSection 24.3 AssessmentBombarding a nuclei with charged particle in order to create new elements is called ____. A.nuclear conversion B.nuclear decay C.induced decay D.induced transmutation </p></li><li><p>Section 24-3ABCDSection 24.3 AssessmentThermonuclear reactions involve: A.splitting nuclei into smaller fragments B.fusing nuclei together to form larger particles C.bombarding nuclei with charged particles D.generating electricity in a nuclear reactor </p></li></ul>

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