Lecture 9.3: Nuclear Energy

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

11. How Electricity is Produced

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

14. 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

15. 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

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

17. 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

18. 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

19. 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

20. Radioactive Isotope Half-lives

22. 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)

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

25. 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.

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

27. 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

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

30. Nuclear Bombs