Shoreham Nuclear Plant on Long Island, New York

2. Shoreham Nuclear Plant on Long Island, New York

3. Nuclear Share of Electrical Power

4. Nuclear Power in the United States

5. NUCLEAR ENERGY • When isotopes of uranium and plutonium undergo controlled nuclear fission, the resulting heat produces steam that spins turbines to generate electricity. • The uranium oxide consists of about 97% nonfissionable uranium-238 and 3% fissionable uranium-235. • The concentration of uranium-235 is increased through an enrichment process.

6. NUCLEAR ENERGY • Nuclear fusion is a nuclear change in which two isotopes are forced together. • No risk of meltdown or radioactive releases. • May also be used to breakdown toxic material. • Still in laboratory stages. • There is a disagreement over whether to phase out nuclear power or keep this option open in case other alternatives do not pan out.

10. Terms and Definitions Fuel rods: rods full of U235 pellets Moderator: fluid (water) coolant that slows down neutrons Control rods: moderate rate of the chain reaction by absorbing neutrons

11. A Nuclear Reactor

12. A Nuclear Reactor Is Designed To Sustain a continuous chain reaction. Prevent amplification into a nuclear explosion. Consist of an array of fuel and control rods. Make some material intensely hot.

13. A Nuclear Reactor

14. Small amounts of radioactive gases Uranium fuel input (reactor core) Control rods Containment shell Heat exchanger Turbine Steam Generator Electric power Waste heat Hot coolant Useful energy 25%–30% Hot water output Pump Pump Coolant Pump Pump Waste heat Cool water input Moderator Coolant passage Pressure vessel Shielding Water Condenser Periodic removal and storage of radioactive wastes and spent fuel assemblies Periodic removal and storage of radioactive liquid wastes Water source (river, lake, ocean) Fig. 16-16, p. 372

15. Decommissioning of reactor Fuel assemblies Reactor Enrichment of UF6 Fuel fabrication (conversion of enriched UF6 to UO2 and fabrication of fuel assemblies) Temporary storage of spent fuel assemblies underwater or in dry casks Conversion of U3O8 to UF6 Uranium-235 as UF6Plutonium-239 as PuO2 Spent fuel reprocessing Low-level radiation with long half-life Geologic disposal of moderate & high-level radioactive wastes Open fuel cycle today “Closed” end fuel cycle Fig. 16-18, p. 373

16. What Happened to Nuclear Power? • After more than 50 years of development and enormous government subsidies, nuclear power has not lived up to its promise because: • Multi billion-dollar construction costs. • Higher operation costs and more malfunctions than expected. • Poor management. • Public concerns about safety and stricter government safety regulations.

17. NUCLEAR ENERGY • In 1995, the World Bank said nuclear power is too costly and risky. • In 2006, it was found that several U.S. reactors were leaking radioactive tritium into groundwater. Figure 16-19

18. NUCLEAR ENERGY • When a nuclear reactor reaches the end of its useful life, its highly radioactive materials must be kept from reaching the environment for thousands of years. • At least 228 large commercial reactors worldwide (20 in the U.S.) are scheduled for retirement by 2012. • Many reactors are applying to extent their 40-year license to 60 years. • Aging reactors are subject to embrittlement and corrosion.

19. NUCLEAR ENERGY • Building more nuclear power plants will not lessen dependence on imported oil and will not reduce CO2 emissions as much as other alternatives. • The nuclear fuel cycle contributes to CO2 emissions. • Wind turbines, solar cells, geothermal energy, and hydrogen contributes much less to CO2 emissions.

20. NUCLEAR ENERGY • Scientists disagree about the best methods for long-term storage of high-level radioactive waste: • Bury it deep underground. • Shoot it into space. • Bury it in the Antarctic ice sheet. • Bury it in the deep-ocean floor that is geologically stable. • Change it into harmless or less harmful isotopes.

21. Radioactive Decay Half life = the time for half the amount of a radioactive isotope to decay.

22. Half-life Molybdenum-99 (half-life = 2.8 days) Xenon-133 (half-life = 5.3 days) Krypton-85 (half-life = 10.7 years) Cesium-137 (half-life = 30.0 years) Plutonium-239 (half-life = 24,000 years)

23. Half life = the time for half the amount of a radioactive isotope to decay. • This is an exponential graph. • When else have we seen this type of graph? • Do the math, the waste will never be totally gone. • Some Uranium’s half life can be up to 700 million years.

24. NUCLEAR ENERGY • After three or four years in a reactor, spent fuel rods are removed and stored in a deep pool of water contained in a steel-lined concrete container. Figure 16-17

25. NUCLEAR ENERGY • After spent fuel rods are cooled considerably, they are sometimes moved to dry-storage containers made of steel or concrete. Figure 16-17

26. Disposal of Radioactive Wastes (200 Thousand Tons) Finding long-term containment sites Transport of highly toxic radioactive wastes across the United States The lack of any resolution to the radioactive waste problem Environmental protests Cost ($60 billion to 1.5 trillion)

27. Disposal of Radioactive Wastes To be safe, plutonium-239 would require 240,000 years (10 half-lives) of containment! Discuss the implications of this in terms of disposal of radioactive wastes. Yucca mountain in southwestern Nevada = the nation’s nuclear waste repository

29. Yucca Mountain, Nevada

30. Nuclear Power Accidents Three Mile Island 1979 Harrisburg, PA Loss of coolant in reactor vessel Damage so bad, reactor shut down permanently Unknown amount of radioactive waste released into atmosphere.

31. Case Study: The Chernobyl Nuclear Power Plant Accident • The world’s worst nuclear power plant accident occurred in 1986 in Ukraine. • The disaster was caused by poor reactor design and human error. • By 2005, 56 people had died from radiation released. • 4,000 more are expected from thyroid cancer and leukemia.

32. Chernobyl, Russia • Loss of water coolant perhaps triggered the accident. When the water-circulation system failed, the temperature in the reactor core increased to over 5,000 oF, causing the uranium fuel to begin melting and producing steam that reacted with the zirconium alloy cladding of the fuel rod to produce hydrogen gas.

33. How Chernobyl Blew Up • A second reaction between steam and graphite produced free hydrogen and carbon oxides. When this gas combined with oxygen, a blast blew off the top of the building, igniting the graphite. The burning graphite threw a dense cloud of radioactive fission products into the air.

34. Consequences of Radiation Exposure • Block cell division • Damage biological tissues and DNA • Death • Cancer • Birth defects

35. Economic Problems with Nuclear Power Energy demand estimates were unrealistic. Costs increase (5X) to comply with new safety standards. Withdrawal of government subsidies to nuclear industry. Public protests delayed construction. Any accident financially ruins the utility.

36. Comparing Nuclear Power with Coal Power

37. NUCLEAR ENERGY • A 1,000 megawatt (MW) nuclear plant is refueled once a year, whereas a coal plant requires 80 rail cars a day. Figure 16-20