Nuclear Technology

1. Nuclear Technology

2. Natural Radioactivity • Energy released by unstable isotopes of elements. • Involves either alpha, beta, or gamma particles. • Natural breakdown depends of the half-life of a radioactive isotope. • Time required for ½ of the atoms of an isotope to decay. • The shorter the half-life the greater the radiation initially released. • E.g. Radium-223 t½ = 11.4 days • Radium-226 t½ = 1600 years • Uranium-238 t½ = 4.468 billion years Nuclear Technology

3. Artificial Radioactivity • Isotopes of atoms are bombarded with neutrons. • Nuclear fission • – The nucleus splits. • – If enough radioactive material is packed • into a small space a chain reaction can occur. • – Nuclear reactions and a-bombs release vast • amounts of energy. Nuclear Technology

4. Artificial Radioactivity • Nuclear fission Nuclear Technology

5. Artificial Radioactivity • Nuclear fusion • – Two nuclei fuse together to form a heavier • atom. • – H-bombs and the sun both use fusion. • – The is also an enormous amount of energy • released in fusion reactions. • – If we could use fusion to produce electricity • there would be a lot less nuclear waste • produced. Nuclear Technology

6. Artificial Radioactivity • Nuclear fusion Nuclear Technology

7. Mass Defect Formula • Mass of nuclear components (p+, no) – • mass of nucleus = Energy • Einstein’s formula: E = mc2 • Used to calculate how much energy is released in a nuclear reaction. Nuclear Technology

8. Mass Defect Formula Nuclear Technology

9. Mass Defect Formula • Example: has 2 p+ and 2 no • 1 p+ = 1.0072765 u • 1 no = 1.0086649 u • 2 p+ + 2 no = 4.0318828 u • However, the mass of a helium nucleus is measured to be only 4.0015062 u! What happened to the remaining 0.0303208 u? • It was converted to energy when the nucleus formed – the source of solar energy. Nuclear Technology 4He 2

10. Weapons • A-bomb (atom-bomb) • – Enrico Fermi created the first chain reactions in 1943 using Uranium-235 or Plutonium-239 • – Neutrons collide with a nuclei causing them to break apart and release other neutrons that collide with still other nuclei. • This is the fission chain reaction. • – A conventional explosive device is needed to trigger the nuclear chain reaction. Nuclear Energy

11. Weapons • First A-bomb(atom-bomb) Nuclear Energy Trinity Test Site New Mexico, USA July 16, 1945 16/1000 of a second after detonation

12. Weapons • H-bomb (hydrogen-bomb) • – Developed in 1952; uses process of fusion of hydrogen. • – More powerful by weight (3 ½ times) than fission. • – An explosive charge triggers intense heat (100 million °C) and density which allows hydrogen nuclei to fuse forming helium nuclei (mimics the sun!). Nuclear Energy

13. Weapons • First H-bomb (hydrogen-bomb) Nuclear Energy Enewetakatoll Marshall Islands Nov. 1, 1952

14. Weapons’ Effects • A-bomb on Hiroshima (1945) was equivalent to 20,000 tons of TNT (dynamite). • H-bomb detonated on the Bikini atoll (1953) was 1,000 times more powerful. • Produced high temperatures (thousands of °C). • Caused radioactive fallout over wide areas carried by the wind. • Cancer causing particles remain long after the explosion. • Physical damage to the blast area is extensive and immediate. Nuclear Energy

15. Weapons’ Effects • A-bomb on Hiroshima & Nagasaki (1945) Nuclear Energy

16. Electrical Production • Hydroelectric • – Flow of water powers a turbine. • – Turbine turns a generator producing electricity. • – Non (or low) polluting process. Other Energy Sources

17. Electrical Production • Hydroelectric Other Energy Sources

18. Electrical Production • Thermal Power • – Burning of fossil fuels (oil, coal, natural gas) to produce steam. • – Steam powers turbine which turns a generator producing electricity. • – A condenser* cools down the steam to complete the cycle and prevent explosions. • – Is a polluting process due to burning of fossil fuels. • * System which cools steam converting it to water (like a car radiator). Other Energy Sources

19. Electrical Production • Thermal Power Other Energy Sources

20. Electrical Production • Nuclear Power • – Uses Uranium or Plutonium for fission process (chain reaction). • – Heat used to produce steam. • – Steam drives a turbine generator producing electrical energy. • – A condenser cools down steam (turns to water) to recycle the system and control for over pressure. Nuclear Energy

21. Electrical Production • Nuclear Power Nuclear Energy

22. Candu Reactor • Canada’s first nuclear reactor developed in 1960. • Uses natural uranium (U-238) with 0.7 % U-235 in fusion process. (Non-enriched uranium). Nuclear Energy

23. Candu Reactor • Uses Deuterium (hydrogen isotope) to produce heavy water (D2O): • – Condenser uses D2O as a coolant since it is more effective in reducing temperature. • – D2O also serves as a moderator by ensuring a constant chain reaction by slowing down the speed of colliding neutrons. • – Too many quick fissions can lead to over-heating causing a meltdown (extremely dangerous!) • – Both Chernobyl and Fukushima are examples of meltdowns, while Three Mile Island was a near meltdown Nuclear Energy

24. Canduin China Candu Reactor Nuclear Energy

25. U.S. Nuclear Reactors • Unlike Canada, U.S. uses: • – Ordinary water as coolant and moderator. • – Enriched Uranium (U-238 plus 3% U-235) in fission process. • Nuclear occurred at Three Mile Island in Pennsylvania (March 28, 1979). • – Reactor overheated, but not meltdown occurred. • – Most of the radioactive particles remained inside. Nuclear Energy

26. Nuclear Waste • Over 40,000 tons of ‘used’ uranium and plutonium is stored in Canada. • ‘Used’ uranium is only 2% radioactive, but requires billions of years to decay completely. • Fuel rods which house uranium is stored on site in bins placed in a pool of water. • Other waste is placed in concrete bins called caissons and stored underground covered in concrete. • Environmental danger due to leakage or in transportation. Nuclear Energy

27. Nuclear Waste Nuclear Energy

28. Medical Uses • Radioactive isotopes with short half-life (to avoid long-term damage to body) are used to treat the thyroid gland and destroy tumors: • – Iodine-131 → thyroid gland • – Cobalt-60 → destroys tumors • Other isotopes act as ‘tracers’ allowing detection of diseases of the heart and lungs (healthy organs do not retain much of the isotopes: • – Rubidium-81 → heart problems • – Tectinetium-99 → kidney problems Applications of Nuclear Technology

29. Medical Uses • Gamma rays (Cobalt-60) are used on foods to prolong shelf life. • Kills bacteria which can cause decay. • The rays do not affect the nuclei in the food – only the electrons (The food does not become radioactive). • Radioactive elements: • Unstable isotopes with more no in nucleus (than other similar elements or isotopes) – unstable but useful… Applications of Nuclear Technology

30. Heavy water • Water made by combining the hydrogen isotope, deuterium (D, or 2H), with oxygen forming D2O. • This isotope has 1 p+, 1 no, and 1 e- and is found in low abundance in nature (0.02%). • A third hydrogen isotope is called tritium (T, or 3H) with 1 p+, 2 no, and 1 e-. • Only the isotopes of hydrogen have their own chemical symbol. Additional Notes

31. Isotopes • Most but not all are unstable, because their atoms split apart. U-238 will go through a ‘decay’ process: • – Undergoing 14 successive stages, taking on 14 different forms before achieving stability as Lead-206. • – This process is radioactive since alpha, beta, gamma radiation, or neutrons are emitted. Additional Notes

32. Isotopes • E.g. U-238 decay series. Additional Notes

33. Nuclear Fission • Involves splitting the nucleus by bombarding it with neutrons. Additional Notes Neutron • When a no hits the nucleus of U-235 splits into two smaller nuclei (Kr & Ba) which in then releases more neutrons that will collide with other nuclei causing a chain reaction (fission).

34. Critical Mass • A minimum required mass of matter is required to sustain a controlled chain reaction (as in a nuclear reactor). If it exceeds the minimum point (critical mass), the reaction goes out of control (as in an a-bomb). Additional Notes

35. Critical Mass Additional Notes

36. Plasma • Plasma is the fourth state of matter. It resembles a very hot gas rich in electrically charged particles made up of ions and electrons. • – When the temperature reaches 3000 °C, the atoms become so excited that they release their e-’s, leaving positively charged ions and free-moving e-. • – The center of the sun is like a giant ball of plasma. Additional Notes

37. Fusion Reactor • The Soviet Union developed the first experimental fusion reactor called Tokamak: plasma made up of hydrogen isotopes, deuterium and tritium, is contained by a magnetic coil preventing the plasma from touching the sides of the chamber walls (or else it would melt them!) • – Strong electric current heats the chamber reaching 1 million C, thus causing fusion and energy is released. • – The technology to sustain such high Temperatures is still far from being developed. • – In 1991, Britain succeeded in creating a minutes worth of energy equal to 1 million Watts (1 MW). Additional Notes

38. Fusion Reactor • Tokamak Additional Notes