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Useful applications of radioactivity and nuclear energy

Useful applications of radioactivity and nuclear energy. Power for good... and evil. Power generation. Heat energy from the nuclear fission is used to create steam that generates electricity by turning a turbine. Dimming of the day.

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Useful applications of radioactivity and nuclear energy

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  1. Useful applications of radioactivity and nuclear energy Power for good... and evil

  2. Power generation • Heat energy from the nuclear fission is used to create steam that generates electricity by turning a turbine

  3. Dimming of the day • Nuclear power offered the promise of plentiful cheap power. It has failed to deliver. • Public hostility and fear • Periodic accidents and disasters • Availability of nuclear fuel • Problems of disposal • Costs of power production

  4. Nuclear power prevalent in Europe

  5. Nuclear power: environmental friend • The greatest environmental threat is perceived to be global warming – the build-up of greenhouse gases from fossil fuels • Nuclear power offers a greenhouse-free alternative

  6. Nuclear dangers: live or Memorex? • A nuclear plant can NEVER result in a nuclear explosion • But accidents have occurred: • Chernobyl • Three Mile Island • Varying views on Chernobyl • Anti-nuke 500,000 deaths • Actual scenario 4,000 deaths • Chernobyl compares favourably with coalmines • Mount St Helens eruption leaked radiation thousands of times greater than Three Mile Island

  7. Useful radioisotopes and half-lives • Selection of nuclide will depend on • Chemical considerations – use of iodine in thyroid for example • Half-life: • Short for medical applications – 123I • Long for dating applications - 14C

  8. Radioisotopes have wide range of uses • H-3 Triggering nuclear weapons, luminous paints and gauges, biochemical tracer • I-131 Thyroid treatment and medical imaging • Co-60Food irradiation, industrial applications, radiotherapy • Sr-90 Tracer in medical and agricultural studies • U-235/238 Nuclear power generation, depleted U used in weapons and shielding • Am-241 Thickness and distance gauges, smoke detectors (low energy gamma – safe for domestic use)

  9. Biological Effects of Radiation • Penetrating powerof radiation is function of mass: -rays> -particles >> -particles. • Ionizing radiation removes electron from water to form H2O+ ions in tissue. • H2O+ ions react with H2O molecule to produce H3O+ and a highly reactive •OH radical. • Free radicals generally undergo chain reactions, producing many radicals in biomolecules.

  10. Measuring the damage

  11. Biological Effects of Radiation • Not all forms of radiation have the same efficiency for biological damage. • To correct, the radiation dose is multiplied by the relative biological effectiveness (RBE), which gives the roentgen equivalent for man (rem). • RBE is about 1 for - and - and 10 for  radiation. • SI unit for effective dosage is the Sievert (1 Sv = RBE x 1 Gy = 100 rem).

  12. Biological Effects of Radiation

  13. Somatic and Genetic damage • Somatic damage. High-energy radiation causes extensive damage to important structural and functional molecules • Sickness and/or death generally result • Genetic damage. Lower levels of exposure cause more subtle changes to the DNA • Physical defects appear in offspring

  14. Biological Effects of Radiation

  15. So what is my exposure? • Worksheet for calculating annual exposure • Is nuclear power so dangerous? • Under normal working conditions, exposure to radiation from a power station is negligible • Concerns center on disasters and waste disposal • What is worse, long-term discharge of greenhouse gases and acid rain on a global scale or more localized sites of radioactive waste storage? Calculate Your Radiation Dose

  16. The Dating Game • Carbon-14 is produced in the upper atmosphere by the bombardment of nitrogen atoms with neutrons: • Radioactive 14CO2 is produced, which mixes with ordinary 12CO2 and is taken up by plants during photosynthesis.

  17. Carbon Dating • During an organism’s life, 14CO2 and 12CO2 are in a dynamic equilibrium at a ratio of 1 part in 1012. • When an organism dies, the 14C/12C ratio decreases as 14C undergoes b decay to 14N. • Measuring the 14C/12C ratio determines the age of the sample with a high degree of certainty. • Ages of 1000–20,000 years are commonly determined. The half-life for 14C is 5730 years.

  18. The age of the earth • U-238 decays eventually to Pb-206 • Since half-life of U-238 is much longer (4.5 billion years) than the intermediates, Pb-206 appears almost instantly after its decay • If the mineral was once pure U-238, after some billions of years it becomes a mixture of U and Pb only • Measuring the ratio of Pb:U gives us the age of the rock • Note that the U-238 half-life is of the order of the age of the earth. If the earth was 6,000 years old or 50 billion years old it would not work

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