1. Geologic Resources: Nonrenewable Mineral and Energy Resources Chapters 14 & 15 G. Tyler Miller’s Living in the Environment Chapters 14 & 15 G. Tyler Miller’s Living in the Environment

2. NUCLEAR POWER President Dwight Eisenhower, 1953, “Atoms for Peace”speech. –Nuclear-powered electrical generators would provide power “too cheap to meter.” Between 1970 and 1974, American utilities ordered 140 new reactors for power plants.

3. Nuclear Power After 1975, only 13 orders were placed for new nuclear reactors, and all of those were subsequently cancelled. –In all, 100 of 140 reactors on order in 1975 were cancelled. Construction costs, declining demand for electrical power, safety fears Electricity from nuclear power plants was about half the price of coal in 1970, but twice as much in 1990.

4. How Do Nuclear Reactors Work Most commonly used fuel is U 235, a naturally occurring radioactive isotope of uranium. Occurs naturally at 0.7% of uranium, but must be enriched to about of 3%. Formed in cylindrical pellets (1.5 cm long) and stacked in hollow metal rods (4 m long). –About 100 rods and bundled together to make a fuel assembly. –Thousands of fuel assemblies bundled in reactor core.

5. How Do Nuclear Reactors Work When struck by neutrons, radioactive uranium atoms undergo nuclear fission (splitting) releasing energy and more neutrons. –Triggers nuclear chain reaction.

6. Nuclear Fission

7. How Do Nuclear Reactors Work Reaction is moderated in a power plant by neutron-absorbing solution (Moderator). –In addition, Control Rods composed of neutron-absorbing material are inserted into spaces between fuel assemblies to control reaction rate. Cadmium or boron –Water or other coolant is circulated between the fuel rods to remove excess heat.

8. PWR

9. Periodic removal and storage of radioactive wastes and spent fuel assemblies Periodic removal and storage of radioactive liquid wastes Pump Steam Small amounts of radioactive gases Water Black Turbine Generator Waste heatElectrical power Hot water output Condenser Cool water input Pump Waste heat Useful energy 25 to 30% Waste heat Water source (river, lake, ocean) Heat exchanger Containment shell Uranium fuel input (reactor core) Emergency core cooling system Control rods Moderator Pressure vessel Shielding Coolant passage Coolant Hot coolant

10. RADIOACTIVE WASTE MANAGEMENT Until 1970, the US, Britain, France, and Japan disposed of radioactive waste in the ocean. Production of 1,000 tons of uranium fuel typically generates 100,000 tons of tailings and 3.5 million liters of liquid waste. –Now approximately 200 million tons of radioactive waste in piles around mines and processing plants in the US.

11. Radioactive Waste Management About 100,000 tons of low-level waste (clothing) and about 15,000 tons of high-level (spent-fuel) waste in the US. –For past 20 years, spent fuel assemblies have been stored in deep water-filled pools at the power plants. (Designed to be “temporary”.) Many internal pools are now filled and a number plants are storing nuclear waste in metal dry casks outside.

12. Radioactive Waste Management US Department of Energy announced plans to build a high-level waste repository near Yucca Mountain Nevada in 1987. –Facility may cost between $10 and 35 billion, and will not open until at least 2015. US Department of Energy announced plans to build a high-level waste repository near Yucca Mountain Nevada in 1987. –Facility may cost between $10 and 35 billion, and will not open until at least 2015.

13. Decommissioning Old Nuclear Plants Most plants are designed for a 30 year operating life. –Only a few plants have thus far been decommissioned. –General estimates are costs will be 2-10 times more than original construction costs.

14. CHANGING FORTUNES Public opinion has fluctuated over the years. –When Chernobyl exploded in 1985, less than one-third of Americans favored nuclear power. Now, half of all Americans support nuclear- energy. Currently, 103 nuclear reactors produce about 20% of all electricity consumed in the US.

15. NUCLEAR FUSION Nuclear Fusion - Energy released when two smaller atomic nuclei fuse into one large nucleus. (Sun) –Duterium and tritium, two heavy isotopes of H –Temperatures must be raised to 100,000,000 o C and pressure must reach several billion atmospheres. –Advantages: Production of few radioactive wastes Elimination of products that could be made into bombs Fuel supply that is larger and less hazardous than uranium.

16. NUCLEAR FUSION Despite 50 years and $25 billion, fusion reactors have never produced more energy than they consume!

17. Nuclear Energy  Fission reactors  Uranium-235  Potentially dangerous  Radioactive wastes Refer to Introductory Essay p. 338 Fig. 15-35 p. 366

18. Dealing with Nuclear Waste Low-level wasteLow-level waste High-level wasteHigh-level waste Underground burialUnderground burial Disposal in spaceDisposal in space Burial in ice sheetsBurial in ice sheets Dumping into subduction zonesDumping into subduction zones Burial in ocean mudBurial in ocean mud Conversion into harmless materialsConversion into harmless materials Fig. 15-40 p. 370

19. Nuclear Alternatives  Breeder nuclear fission reactors  Nuclear fusion  New reactor designs Storage Containers Fuel rod Primary canister Overpack container sealed Underground Buried and capped Ground Level Unloaded from train Lowered down shaft Personnal elevator Air shaft Nuclear waste shaft Fig. 15-42 p. 376