Uranium

1. Uranium Keith Becker Grace Amico Bryan Park

2. Basics • Heaviest of all naturally occurring elements. • Metal substance that is easily fissionable. • Found in rocks all over the world (uranium ore). • Abundant but nonrenewable. Developed in WW II era.

3. U 235 Used for energy production. Easily split when bombarded by neutrons causing a chain reaction. Releases heat energy and radiation. U 238 Not easily split and therefore inefficient for energy production. Isotopes

4. Nuclear Fuel Cycle • Nuclear energy is released through fusion or fission. • Fission is the only viable source as humans have yet to develop efficient fusion technology. • To get usable uranium fuel requires: • Mining, milling, conversion, enrichment, and fuel fabrication.

5. Mining • First step in process. • Uranium ore is mined from underground and surface mines. • One ton of uranium ore in the US yields 3-10 pound of pure uranium.

6. Milling • Ore is crushed and mixed with acid. • Uranium is dissolved while other substances such as rock remain solid. • Acid solution is then drained and dried into “yellowcake”.

7. Conversion • Yellowcake is converted into a gas called uranium hexafluoride. • This is then shipped to a gaseous diffusion plant.

8. Enrichment • Uranium must be processed in order to increase concentrations. • Enrichment increases concentration anywhere from 1-5%. • This process removes U 238

9. Fuel Fabrication • U made solid and formed into ceramic pellets. • One pellet has the same amount of energy as 150 gallons of oil. • Pellets are sealed into 12 foot tubes called fuel rods. • Rods are then grouped into fuel assemblies.

10. Nuclear Reactor • Fission takes place in the reactor core. • Surrounding the core of the reactor is a shell called the reactor pressure vessel.

11. Nuclear Reactor Cont. • There are 200 fuel assemblies in each reactor core. • Moveable control rods are placed in between assemblies to absorb neutrons and slow down the nuclear reaction. • Reaction produces heat which is used to create steam just as in a coal or oil power plant. • Steam turns turbine generators which produce electricity. • Water is also used to cool the reactor.

12. Used Fuel Storage • Fuel rods much be replaced every 12-18 months to reduce radioactive waste in the reactor. • Used fuel is a mix of radioactive waste and unused fuel. • Stored in a deep pool of water called a “used fuel pool”. • In 3 months the waste loses 50% of its radioactivity due to decay. 1 year= 80% and 10 years = 90%. • Then deposited into a permanent federal disposal site.

13. Reprocessing • 1/3 of the fuel is unused when the fuel rod is replaced. • Reprocessing separates unused fuel from radioactive waste. • Reprocessing is more expensive than making new fuel, so most companies don’t do it.

14. Waste Repository • Believed that storing nuclear waster deep underground is safest. • The 1982 Nuclear Waste Policy Act led to the designing and construction of the first U.S. first repository, which opens this year. The repository will store waste from nuclear plants and defense weapons plants. • People who use electricity from nuclear power plants pay 1/10 cent for each kilowatt/hr of electricity (the average house pays $7.50).

15. Nuclear Energy Use • 20% of electricity in US comes from nuclear power. • 18% of world electricity comes from nuclear power. • Leading countries in nuclear energy production are the US, France, Japan and Germany. • 75% of France’s electricity comes from nuclear power.

16. Radiation • Natural: cosmic rays from space, minerals, and radon in the air. • Man-made: x-ray equipment, smoke detectors, color TV, and luminous dial clocks.

17. Ionizing Radiation • Ionizing radiation can be harmful because it can destroy or damage cells. • Alpha radiation: slowest form, can be stopped by a sheet of paper or skin. • Beta radiation: can pass through an inch of water or skin. • Gamma radiation: electromagnetic wave that has no weight and can pass through lead, concrete, and large amounts of water.

18. Licensing • Permits are needed in order to start construction of a nuclear plant and licenses are needed to begin the operation. • The plans and reports must be sent to the Nuclear Regulatory Commission. • Before construction begins, local hearings are held so that people may voice their opinions about the project.

19. Nuclear Safety • Two main examples of Nuclear Energy Plants going wrong- • Three Mile Island (United States, 1979) • Chernobyl (Ukraine, 1986)

20. Three Mile Island • Water was accidentally cut off to the reactor core which caused the Uranium fuel to melt. • The result was that some radioactive material escaped, but no one was injured because of the plant’s many safety barriers.

21. Chernobyl • Two explosions blew off the top of the reactor building and a large amount of radioactive material was introduced to the area. • 100,000 people were evacuated from their homes, 200 workers were treated for radiation sickness and burns, and 31 people died. • However, Chernobyl was extremely rare and it is highly unlikely that a similar incident would repeat due to better security.

22. Miscellaneous Information • Radiation is measured by rem and millirem. The average American is exposed to about 360 millirem a year (harmless amount). • 80% of the Uranium in the U.S. is imported. • In 2007 Uranium cost $75 per pound. • Nuclear plants have high up-front costs, but save money and resources in the long run.

23. Miscellaneous Information • Nuclear electricity costs about 2 cents per kilowatt/hr. • Our Uranium resources could last us for another 500 years, and through a process called “breeding,” which converts Uranium into Plutonium, we could extend Uranium reserves for millions of years but it is currently only being used in France. • Nuclear power plants create no air pollution and water used for cooling processes is recycled.