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Understanding Nuclear Energy: Radioactivity, Fission, and Waste Management

This lecture explores the fundamental concepts of nuclear energy, focusing on radioactivity and nuclear decay processes including alpha, beta, and gamma radiation. It discusses the mechanics of nuclear fission, including the production of electricity, and highlights the pros and cons of nuclear energy compared to fossil fuels. Additionally, the issues of nuclear waste management and safety concerns associated with nuclear power plants, illustrated by historical accidents like Three Mile Island and Chernobyl, are addressed.

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Understanding Nuclear Energy: Radioactivity, Fission, and Waste Management

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  1. Lecture 9.3: Nuclear Energy Chapter 12

  2. Changes in the nucleus • Radioactivity • spontaneous emission of radiation from nucleus • 3 types of radiation • Alpha • Beta • Gamma Distinguish them by their charge, mass, and penetrating power

  3. Nuclear Decay • Alpha Decay • Helium Nucleus

  4. Nuclear Decay • Alpha Decay • Beta Decay • Electron ***A neutron becomes a proton and ejects an electron

  5. Nuclear Decay • Alpha Decay • Helium Nucleus • Beta Decay • Electron • Gamma Ray • Ray of Light • EM radiation

  6. Penetrating Power • Alpha • stopped by clothing or paper • Beta • can pass through clothing & damage skin • Gamma rays: • Penetrates bodily tissues. Requires shielding by concrete or lead (High level waste)

  7. 4He 4α 212Po 4α+ A(?) 212Po 4α+ 208Pb or alpha particle - 2 2 Z 82 84 84 2 2 Balancing Nuclear Equations 212Po decays by alpha emission. Write the balanced nuclear equation for the decay of 212Po. Remember to conserve the mass number and atomic number 212 = 4 + A A = 208 84 = 2 + Z Z = 82

  8. 235U is the FuelFission is the Process • 1 g235U has 2 to 3 million times the energy of 1g of coal

  9. Fission Reactions

  10. How Electricity is Produced

  11. Nuclear Fission • Nuclear Fuel Cycle • processes involved in producing the fuel used in nuclear reactors and in disposing of radioactive (nuclear) wastes

  12. Cost of Electricity from Nuclear Energy • Cost is very high • 20% of US electricity is from Nuclear Energy • Affordable due to government subsidies • Expensive to build nuclear power plants • Long cost-recovery time • Fixing technical and safety issues in existing plants is expensive

  13. 35,000 tons SO2 4.5 x 106 tons CO2 70 ft3 vitrified waste 3.5 x 106 ft3 ash 1,000 MW coal-fired power plant 1,000 MW nuclear power plant Nuclear Fission Annual Waste Production 23.5

  14. Pros and Cons of Nuclear Energy • Pros • Less of an immediate environmental impact compared to fossil fuels

  15. Nuclear Fission • Chain reaction • Mass reactants > mass products slightly less • E = mc2 • S.C.R.A.M a reactor • Nuclear Waste • Nuclear Accidents • Three Mile Island, PA • Chernobyl, Ukraine • Fukushima, Japan

  16. Simple Example • A 500. g sample of Uranium has a half life of 50 years. What mass of uranium will remain after 250 years? 04/14/11 Chemistry with Mr. O'Leary

  17. Let’s Think This Out With a Chart • Lets figure out the to the total number of half lives (n) • 250 years/50 years = 5= n PLUG: mfinal = 500(1/2)5 04/14/11 Chemistry with Mr. O'Leary

  18. Radioactive Isotope Half-lives

  19. Safety Issues in Nuclear Power Plants • Meltdown • At high temperatures the metal encasing the uranium fuel can melt, releasing radiation • Probability of meltdown or other accident is low • Public perception is that nuclear power is not safe • Sites of major accidents: • Three Mile Island • Chernobyl (Ukraine)

  20. Radioactive Wastes • Long term solution to waste • Deep geologic burial –Yucca Mountain • Possibilities: • Above ground mausoleums • Arctic ice sheets • Beneath ocean floor

  21. Radioactive Waste • Temporary storage solutions • In nuclear plant facility (require high security) • Under water storage • Above ground concrete and steel casks • Need approved permanent options soon.

  22. Case-In-Point Yucca Mountain • 70,000 tons of high-level radioactive waste • Tectonic issues have been identified

  23. Nuclear Fusion 2H + 2H 3H + 1H 1 1 1 1 2H + 3H 4He + 1n 2 1 0 1 Fusion Reaction Energy Released 6.3 x 10-13 J 2.8 x 10-12 J

  24. Summary • Fission • The Missing Mass • Nuclear Reactors • Nuclear Waste Disposal • Fusion • Cold Fusion

  25. Nuclear Bombs

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