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Nuclear Energy

Nuclear Energy. Isotopes. Isotopes = 2 atoms of the same element ( same # of protons / atomic # ) that have different numbers of__________ . - Since the number of _________ is different, the isotopes have different __________. -

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Nuclear Energy

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  1. Nuclear Energy

  2. Isotopes Isotopes = 2 atoms of the same element (same # of protons / atomic # ) that have different numbers of__________. - Since the number of _________ is different, the isotopes have different __________. - The number given after the element symbol is the atomic mass. Examples: • 3 isotopes of H2O • Carbon-12 & Carbon-14 (12C & 14C) • U-235 & U-238

  3. Nuclear Fission nuclear fission: (fission = to split) a nuclear change in which certain unstable isotopes of high mass numbers split into lighter nuclei & ______________ in the process. Fission of a uranium–235 nucleus, initiated by a neutron.

  4. Half-Life: The amount of time that it takes half of a radioactive sample to decay.

  5. Determining amount of radioactive isotope remaining 1 half-life ½ (1/21) 2 half- lives ___ (1/22) 3 half-lives ___(1/23) 4 half-lives ___(1/24) Formula: N = No (0.5)t t= number of half-lives N = amount left No = original amount

  6. Half-life Comparisons

  7. Radioactive Decay Unstable isotopes undergo decay to form other isotopes, & in the process energy is emitted in three forms: • alpha particles: fast–moving, _______________(= Helium nucleus) • beta particles: fast–moving, ________________ • gamma rays: high–energy__________________ Alpha Decay

  8. Alpha particles can be blocked most easily, since they are _________ than beta particles. Gamma rays are the most difficult form of radiation to block, since they are not composed of matter, but rather are high frequency electron radiation.

  9. Alpha Decay Animation

  10. Nuclear Fission Video

  11. 2 Types of Beta Decay Beta minus decay: A neutron decays into a __________________ with the electron emitted. Beta Plus Decay Beta Minus Decay Beta plus decay: A proton decays into a ______ ______________with the positron emitted. (Like an electron, a positron has no significant mass.)

  12. Discuss with your table partner: Review the type of particles released in alpha, beta minus and beta plus decay (and what particles breakdown for beta decay). Determine what new isotope would be produced in each of the examples of radioactive decay on the next three slides.

  13. Plutonium-236 (atomic number 94) undergoes alpha decay. What is the atomic number of the new isotope? What is atomic mass of the new isotope? New isotope: ____ ____ _________________

  14. Magnesium-23 (atomic # 12) undergoes beta plus decay. What is the atomic number of the new isotope? Why? What is atomic mass of the new isotope? New isotope: ___ _______________________ ___ ___________

  15. Carbon-14 (atomic number 6) undergoes beta minus decay. What is the atomic number of the new isotope? Why? What is atomic mass of the new isotope? New isotope: __ ______________________ __ ______________

  16. Radioactive Pathway: A radioactive isotope can undergo a series of radioactive decay, until a stable isotope is reached.

  17. Increasing frequency and energy Increasing wavelength Gamma Rays are very high energy waves with a short wavelength

  18. Radiation Intensity is inversely related to the distance from the source: Intensity α 1/r2 (r = radial distance from source)

  19. Radioactivity Units • Some conversions: 1 Curie = 3.7 x 1010 disintegrations/sec 1 millicurie = 37 megabequerel (1 Bq = 1 disintegration/sec) 1 coulomb/kg = 3880 Roentgen • Average dose per person/year (US) = 360 mrem/yr (millirem/yr) • International Standard for safe yearly dose = 5,000 mrem/yr = 5 rem/yr (for people who work around radioactivity)

  20. Sources of Radiation: • Cosmic: from sun and other stars • Terrestrial: decay of radioactive elements in ground. Common decay product is radioactive radon gas • Food has Carbon 14 • Medical: X-rays, CT scans… • Coal plants release some radioactivity

  21. Nuclear Chain Reactions nuclear chain reaction: multiple fissions resulting from a _________feedback loop in which each fission releases neutrons that cause more fissions to occur. A nuclear chain reaction leads to major release of energy in the form of heat (and light).

  22. Nuclear Fission Chain Reaction Video http://www.youtube.com/watch?v=kHXMiYsFSrU

  23. Nuclear Energy Nuclear fission reactors produce electricity from heat released by the fission of uranium–235 or plutonium–239. • controlled rate of fission by absorbing excess neutrons with _________ & surrounding the reaction core with_______; • built–in safety features are supposed to minimize the risk of release of radioactive substances or an out-of-control fission reaction.

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

  25. Video: How Nuclear Energy Works http://www.youtube.com/watch?v=MGj_aJz7cTs

  26. http://www.youtube.com/watch?v=VJfIbBDR3e8 Types of Nuclear Reactors Video

  27. Nuclear Energy Use In United States, nuclear energy is declining. • No new plants since ______ . Although, first permits in decades is underway for two plants. • Existing plants (105) retired by 2030. Some other countries are investing increasingly in nuclear energy. • France gets about 78% of its energy from nuclear power plants.

  28. Nuclear Power Plants in 2005

  29. Japan set a policy to phase out nuclear power by 2040.

  30. Nuclear Accidents: Three Mile Island On March 29, 1979, reactor at the Three Mile island nuclear plant near Harrisburg, PA, lost its coolant & the core suffered a _________________. • 50,000 people evacuated & another 50,000 fled area; • unknown amounts of radioactive materials were released; an estimated 15-24 curies of I-131 • partial cleanup & payment of damage claims cost $1.2 billion so far; • 1997 study concluded that increased cancer rates were caused by released radiation.

  31. Nuclear Accidents: Chernobyl On April 26, 1986, Chernobyl disaster in the Ukraine: a series of explosions in a nuclear reactor flung radioactive debris into the atmosphere.

  32. http://www.youtube.com/watch?v=KGc3v50V1_o&feature=related Chernobyl Liquidators

  33. Chernobyl • About 400,000 people were forced to leave their homes • According to a UN report, some 160,000 km2 (62,000 mi2) remain contaminated; • About 35-49 million Curies of I-131 was released

  34. Chernobyl Zone of Exclusion The zone of exclusion is _________, which is the size of __________________.

  35. Chernobyl • In 1998 the Ukrainian health ministry reported 3,576 deaths. However, Greenpeace estimates a total death toll of about 32,000; • Over half a million people were exposed to dangerous levels of radioactivity; • The cost of the incident is estimated in excess of $358 billion.

  36. Chernobyl News Report 1986 http://www.youtube.com/watch?v=XmeeEpWxfRY

  37. Chernobyl 20 Years Later http://www.youtube.com/watch?v=ldYeFLZqh3Q

  38. Nuclear Accidents: Fukishima Dai-ichi • On March 11, 2011, a 9.0 earthquake hit off the coast of Japan, creating a 13-15 m (43-49 foot) tsunami wave. • Electricity from Japan’s grid was lost, but emergency generators came on-line to power the cooling systems. • A tsunami flowed over the 5.7 m seawall at the plant ________________________________________. • The fuel in the reactors began to over-heat. • 12 mile exclusion zone • 80,000 people displaced • Over 1,600 employees exposed to high levels of radiation.

  39. Nuclear Accidents: Fukishima Dai-ichi The explosions sent large amount of radioactive elements into the atmosphere http://www.cbsnews.com/8301-18563_162-57395780/a-rare-look-at-the-fukushima-daiichi-no-go-zone/

  40. Nuclear Accidents: Fukishima Dai-ichi The coolant leaking out of the cores contaminated ground water and ocean water. The extent of ocean radiation contamination as of Oct., 2011

  41. Nuclear Fuel Cycle • Decommissioning of reactor • Fuel assemblies • Reactor • Enrichment of UF6 • Fuel fabrication • (conversion of enriched UF6 to UO 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 UF6 Plutonium-239 as PuO2 • Spent fuel reprocessing • Low-level radiation with long half-life • Geologic disposal of moderate- and high-level radioactive wastes • Open fuel cycle today • Recycling of nuclear fuel

  42. Long Term Storage Issues After 3 or 4 Years in a Reactor, Spent Fuel Rods Are Removed and Stored in Water

  43. Storage of Nuclear Waste • Storing nuclear waste is the ultimate NIMBY situation (Not In My Back Yard) • Until a long-term location is opened, nuclear waste remains stored at ___________________ • Short-term storage involves keeping waste submerged in open pools of water for as long as 5 years and then eventually sealing the waste in steel and concrete casks • In CA, waste is stored near earthquake faults, and most other plants are located near major water sources, due to the large amount of water that is required for keeping the reactor cores cool • Many feel that it is dangerous to leave the waste ________ _______________ (i.e. it is vulnerable to terrorist attacks, accidents, or natural disasters)

  44. Long-Term Storage of Waste: Yucca Mt. Controversy Yucca Mountain National Nuclear Repository: • 100 miles NW of Las Vegas on western edge of the Nevada Test Site • Repository would be 1000 ft below the top of the mountain and 1000 ft above the ground water.

  45. Yucca Mountain • $10 billion has been spent so far to build a 5 mile long tunnel in the mountain

  46. Yucca Mountain • 90% of waste from power plants, 10% from defense programs • Waste is currently stored at facilities in 43 states

  47. Yucca Mountain Lawsuits • There were many law suits against Yucca Mountain project. Most cases were dismissed except for the EPA lawsuit on the following grounds: • EPA was required to keep radiation exposure to safe levels for as long as National Academy of Sciences’ scientists determined the site would have unsafe levels of radioactivity • Scientists determined the site would be highly radioactive for at least 100,000 years • EPA would only guarantee site for 10,000 years, and argued that nothing could be guaranteed for longer periods.

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