Lecture 25.3- Fusion & fission


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Section 25.3 lecture for honors & prep chemistry

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  • Lecture 25.3- Fusion & fission

    1. 1. Bellwork- Half-life <ul><li>A patient is administered 20 mg of iodine-131. </li></ul><ul><li>How much of the isotope will remain in the body after 40 days if the half- life for iodine-131 is 8 days? </li></ul>
    2. 2. Fission and Fusion of Atomic Nuclei <ul><li>The sun is not actually burning. If the energy given off by the sun were the product of a combustion reaction, the sun would have burned out approximately 2000 years after it was formed, long before today. You will learn how energy is produced in the sun. </li></ul>
    3. 3. <ul><ul><ul><li>When the nuclei of certain isotopes are bombarded with neutrons, they undergo fission , the splitting of a nucleus into smaller fragments. </li></ul></ul></ul><ul><ul><ul><li>This often produces more neutrons. </li></ul></ul></ul>25.3
    4. 4. <ul><ul><li>In a chain reaction , some of the neutrons produced react with other fissionable atoms, producing more neutrons which react with still more fissionable atoms. </li></ul></ul>25.3
    5. 5. <ul><ul><ul><li>Nuclear Fission </li></ul></ul></ul>
    6. 6. 25.3 A Nuclear Power Plant uses fission to produce energy
    7. 7. <ul><ul><li>Neutron Moderation </li></ul></ul><ul><ul><ul><li>Neutron moderation slows down neutrons so the reactor fuel (uranium-235 or plutonium-239) can capture them to continue the chain reaction. </li></ul></ul></ul>25.3
    8. 8. <ul><ul><ul><li>Neutron absorption is a process that decreases the number of slow-moving neutrons. </li></ul></ul></ul><ul><ul><ul><li>Control rods, made of a material such a cadmium, are used to absorb neutrons. </li></ul></ul></ul>25.3
    9. 9. <ul><li>Animation 30 </li></ul><ul><li>Take a close look at a nuclear fission chain reaction. </li></ul>
    10. 10. <ul><li>Fission reactor </li></ul>
    11. 11. <ul><ul><ul><ul><li>Used fuel rods are kept under water in holding tanks. </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Water cools the spent rods, and also acts as a radiation shield to reduce the radiation levels. </li></ul></ul></ul></ul>25.3
    12. 12. <ul><ul><ul><li>Fusion occurs when nuclei combine to produce a nucleus of greater mass. </li></ul></ul></ul><ul><ul><ul><li>In solar fusion, hydrogen nuclei (protons) fuse to make helium nuclei and two positrons. </li></ul></ul></ul>
    13. 13. <ul><ul><li>Fusion reactions, in which small nuclei combine, release much more energy than fission reactions, in which large nuclei split. </li></ul></ul>25.3
    14. 14. <ul><ul><ul><li>The use of controlled fusion as an energy source on Earth is appealing. </li></ul></ul></ul><ul><ul><ul><ul><li>The potential fuels are inexpensive and readily available. </li></ul></ul></ul></ul><ul><ul><ul><ul><li>There is no radioactive waste product </li></ul></ul></ul></ul>25.3
    15. 15. <ul><ul><ul><ul><li>The problems with fusion lie in achieving the high temperatures necessary to start the reaction and in containing the reaction once it has started. </li></ul></ul></ul></ul><ul><ul><ul><ul><li>VIDEO </li></ul></ul></ul></ul>25.3
    16. 16. 25.3 Section Quiz. <ul><ul><li>1. One of the control mechanisms for a sustainable nuclear chain reactor involves slowing down the released neutrons so they may be captured by other nuclei. This is done using </li></ul></ul><ul><ul><ul><li>moderators. </li></ul></ul></ul><ul><ul><ul><li>shielding. </li></ul></ul></ul><ul><ul><ul><li>absorbers. </li></ul></ul></ul><ul><ul><ul><li>control rods. </li></ul></ul></ul>
    17. 17. 25.3 Section Quiz. <ul><ul><li>2. Spent fuel rods are stored in </li></ul></ul><ul><ul><ul><li>lead-lined containers. </li></ul></ul></ul><ul><ul><ul><li>deep pools of water. </li></ul></ul></ul><ul><ul><ul><li>thick concrete bunkers. </li></ul></ul></ul><ul><ul><ul><li>cadmium or graphite containers. </li></ul></ul></ul>
    18. 18. 25.3 Section Quiz. <ul><ul><li>3. Choose the correct words for the spaces. In solar fusion, _______ nuclei fuse to form _______ nuclei. </li></ul></ul><ul><ul><ul><li>helium, hydrogen </li></ul></ul></ul><ul><ul><ul><li>hydrogen-1, hydrogen-2 </li></ul></ul></ul><ul><ul><ul><li>hydrogen, helium </li></ul></ul></ul><ul><ul><ul><li>hydrogen-1, hydrogen-3 </li></ul></ul></ul>