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Nuclear energy

Nuclear energy. Review: Elements and Isotopes. What are elements defined by? What are isotopes? What is the difference between a stable and a radioactive isotope?. Radioisotopes. experience radioactive decay (the loss of alpha or beta particles over time)

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Nuclear energy

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  1. Nuclear energy

  2. Review: Elements and Isotopes • What are elements defined by? • What are isotopes? • What is the difference between a stable and a radioactive isotope?

  3. Radioisotopes • experience radioactive decay (the loss of alpha or beta particles over time) • Result: atoms of one element physically change into another element. • Eg Carbon-14 decays to Nitrogen-14 by loss of negative beta particles • Radioactive half life= the amount of time it takes for 50% of the radioactive isotope in a substance to decay.

  4. Practice: Plutonium-239 has a half-life of 24,000 years. How much of a 4 gram sample will remain after 96,000 years? • 1g • 0.5g • 0.25g • 0.125g • 0.625g

  5. Dating with radioactive isotopes • Carbon-14 can be used to estimate the age of plant and animal remains

  6. Geological dating with Uranium • Uranium-238 is a very common radioisotope that decays to a stable isotope of lead • It has a half life of 4.5 billion years

  7. The discovery of radioactive atoms • 1896 uranium radiation observed • 1898 radiation consists of high energy particles • 1919 N nuclei hit with alpha particles turned into O • 1938 First fission reaction

  8. Nuclear rxns vs combustion Combustion Nuclear Nucleic changes result in element transformations Small of amount of matter releases large amounts of energy…less mass in products • Atoms do not change; are rearranged • Mass of reactants = mass of products • Energy is released as heat when bonds break

  9. Types of nuclear reactions • Fission • Fusion

  10. NUCLEAR ENERGY • Nuclear power plants use U-235, a radioactive isotope of uranium. • Mining • Enrichment • Fuel assembly

  11. Nuclear power plant

  12. NUCLEAR WASTE

  13. NUCLEAR WASTE

  14. Math Practice After 100 million years, only 1/32 of the original amount of a particular radioactive waste will remain. The half-life of this radioactive waste is how many million years? a. 10 b. 20 c. 30 d. 40 e. 50 You have 180g of a radioactive substance. It has a half-life of 265 yrs. After 1,325 yrs, what mass remains?

  15. Nuclear waste • Low level • Radioactive solids, liquids, or gases that give off small amounts of ionizing radiation • Sources include power plants, hospitals, research labs, and industries • Low Level Radioactive Waste Policy Act 1980 & 1985 • All states must be responsible for disposal of non-defense related waste produced w/in their borders. • High level • Radioactive solids, liquids, or gases that initially give off large amounts of ionizing radiation • Sources include anything that was inside the reactor core (metals, water, gases, spent fuel)

  16. Nuclear Waste Policy Act 1982 • Stated that there must be a permanent site for storing high level waste by 1998 • That was not met; postponed to 2010 at earliest • 1987 Congress identified Yucca Mountain in Nevada as the best potential site • In 2002 it was officially approved by Congress • Rescinded by Obama in 2009

  17. 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.

  18. The risks of nuclear energy • Meltdown • Acute radiation syndrome • Daily radiation for workers (carcinogenic over time) • Radiation into groundwater from stored waste • Small scale persistent radiation to nearby communities

  19. Radiation and health • We are exposed to natural (background radiation) and artificial radiation every day • 300 millirems per year from space/the atmosphere, the soil (radon), foods we eat (radioactive potassium) • 60 millirems from manmade radiation (radiowaves, hospitals, industries, housing materials, microwaves, cell phones, tobacco, television, smoke detectors, etc.)

  20. Figure 16-19

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