BI 105A Environmental Biology

1. BI 105AEnvironmental Biology Professor Jill Nissen Montgomery College Fall 2006

2. Chapter 12 Nuclear Energy

3. Chemical Energy • Chemical reactions involve the forming and breaking of bonds between atoms, but • Chemical energy is the energy stored in the bonds of molecules • atoms of one element do not change to atoms of another element, nor does any of their mass change to energy

4. Nuclear Energy • Nuclear energy is the energy released by nuclear fission or fusion • Nuclear reactions involve changes in the nuclei of atoms, and • small amounts of mass are converted to large amounts of energy: • E = mc2

5. Nuclear Energy • Nuclear reactions produce 100,000 times more energy per atom than do chemical reactions such as combustion

6. Split atoms Neutrons Uranium-235 Nuclear Energy Comes From Fission

7. Heat Neutrons Splitting Atoms Releases Neutrons, Making Heat

8. Steam produced Electricity Heat Heat Produces Steam, Generating Electricity Steam Generator Turbine Condenser

9. Nuclear Power PlantTurbine and Generator Steam Spinning turbine blades and generator Boiling water

10. Uranium-235 • Uranium ore consists of 3 isotopes: U-238, U-235, and U-234 • Uranium is naturally radioactive • the emission of energetic particles or rays from unstable atomic nuclei • Only U-235 is a fissionable material that can be used for nuclear power

11. Uranium Ore IsMined and Refined

12. Enrichment Concentrates theU-235 Isotope

13. Uranium Is Encased in Solid Ceramic Pellets

14. Fuel Rods Filled With Pellets Are Grouped Into Fuel Assemblies

15. Controlling the Chain Reaction Fuel Assemblies Control rods Withdraw control rods, reaction increases Insert control rods, reaction decreases

16. Pressurized Water Reactor Steam Condenser

17. U.S. Emission-Free Electricity(2003) Source: U.S. Energy Information Administration

18. 29% Greater Nuclear Energy Limits Carbon Dioxide Emissions in Power Sector(2002) Electric Power Industry CO2 Emissions Estimated Electric Power Industry CO2 Emissions Without Nuclear Power Source: EPA

19. 33% Greater Nuclear Energy Limits Sulfur Dioxide Emissions in Power Sector(2002) Electric Power Industry SO2 Emissions Without Nuclear Power Sources: EPA, EIA

20. International Programs • Finland and China are adding reactors to meet energy demand and enhance air quality • Germany and Sweden committed to phasing out nuclear power, then • Germany later launched a pilot program that includes allowances for nuclear plants • In 2002 Sweden removed the deadline for shut down • Canada approved tax incentives for nuclear capacity • France obtains 77% of its electricity from nuclear power

21. U.S. Programs • U.S. phasing out • U.S. currently ~7% of energy nuclear; • no new U.S. power plants ordered since 1976 • 40% of 105 commercial nuclear power expected to be retired by 2015 & all by 2030;

22. What Happened? • crippled by high & uncertain costs; • frequent malfunctions (Three Mile Island, Chornobyl); • false assurances and cover–ups; • overproduction of energy in some areas; • poor management; • lack of public acceptance.

23. Three Mile Island • What happened, step by step • http://www.pbs.org/wgbh/amex/three/sfeature/index.html

24. History’s Worst Nuclear Accident • April 26, 1986 - During a test at the Chornobyl plant, the No. 4 reactor exploded • April 27, 1986 – The secret was out! • 203 hospitalized, 31 died • Evacuation zone 30km over a month • Thyroid cancer among children increased • Still waiting for long-term effects

25. History’s Worst Nuclear Accident • The sum of [Chornobyl] and exposures to people all over the world," writes Bernard Cohen, "will eventually, after about fifty years, reach 60 billion millirems, enough to cause about 16,000 deaths.“ He puts Chornobyl's danger in context by pointing out that 16,000 deaths are caused every year by air pollution from coal-burning power plants in the United States alone.

26. Land use 17,000 ac 1,900 ac Daily fuel requirement 9,000 tons/day 3 kg/day Moderate to severe Air pollution Low Radioactive emissions 1 curie 28,000 curies Long-term risk over large area Risk from catastrophic accidents Short-term local risk Pros and Cons of Nuclear Energy Impact Coal Nuclear

27. Radioactive Wastes • Low level radioactive wastes are items contaminated by radioactivity that give off small amounts of ionizing radiation • High level radioactive wastes are produced by nuclear power plants and give off large amounts of ionizing radiation • Dangerous levels of radioactivity require special handling and secure storage • Case-in-Point: Yucca Mountain • http://msnbc.msn.com/id/3042216/

28. Can be reprocessed for . . . OR Nuclear weapons Fuel for Nuclear Weapons • The Link Between Nuclear Energy and Nuclear Weapons Spent fuel from conventional nuclear plant Fuel for breeder reactor

29. The Future of Nuclear Power • The safe disposal of radioactive wastes is one of the main difficulties to be overcome if nuclear energy is to realize its potential in the 21st centure

30. Review Objectives Introduction to Nuclear Processes• Distinguish between nuclear energy and chemical energy.• Contrast fission and fusion.• Define radioactive decay. Nuclear Fission• Describe the nuclear fuel cycle, including the process of enrichment.• Define nuclear reactor and describe a typical nuclear power reactor. Pros and Cons of Nuclear Energy• Discuss the pros and cons of electric power produced by nuclear energy versus coal. Safety Issues in Nuclear Power Plants• Describe the nuclear power plant accidents at Three Mile Island and Chornobyl.• Discuss the link between nuclear energy and nuclear weapons. Radioactive Wastes• Distinguish between low-level and high-level radioactive wastes.• Relate the pros and cons of permanent storage of high-level radioactive wastes at Yucca Mountain The Future of Nuclear Power• Briefly summarize the issues that must be addressed if nuclear power is to become a major energy source in the future.