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The Nucleus

The Nucleus. Physics is Phun November 2004. Topics: Nuclear structure Nuclear radiation Useful radiation effects. The Electromagnetic Spectrum. “Waves”. “Photons”. c = f λ c = the speed of light f = frequency λ = wavelength. E = h f E = photon energy h = Planck’s constant

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The Nucleus

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  1. The Nucleus Physics is Phun November 2004

  2. Topics:Nuclear structure Nuclear radiationUseful radiation effects

  3. The Electromagnetic Spectrum “Waves” “Photons” c = f λ c = the speed of light f = frequency λ = wavelength E = h f E = photon energy h = Planck’s constant f = frequency

  4. Infrared Visible light Ultraviolet

  5. “Members” of theElectromagnetic Spectrum

  6. Atomic models:1. the “plum-pudding” model2. the “nuclear” model(tiny nucleus with electronsin much larger orbits) Beryllium atom (without neutrons!!)

  7. The Nucleus1. Protons (positive charge)2. Neutrons (neutral charge)3. Nuclear Diameter ~10-15 m(atomic diameter ~10-10 m) The term “nucleon” refers to either a proton or a neutron in the nucleus. The term “nuclide” refers to a nucleus with a specific number of protons and neutrons.

  8. Stable Nuclides All Known Nuclides

  9. Nuclear models:1. the “water-drop” model2. the “shell” model Models tell us aspects of the structure of nuclei and how they behave.

  10. The water-drop modelall nucleons “undifferentiated”binding energy is equally distributed

  11. Binding Energy BE = M(Z protons) + M(N neutrons) – M(Nucleus) BE is the energy required to separate the full nucleus into its individual protons and neutrons

  12. Average Binding energy per nucleon

  13. Applications of thewater-drop model1. Nuclear fission (very large nuclei break up)2. Nuclear fusion(very small nuclei fuse together)

  14. Nuclear fission235U + n –—> small nuclei + neutrons + ENERGY!!n + 235U –—> another fissioncreating a “chain reaction”

  15. NuclearChainReaction Click title above to see video

  16. Controlled fission:Nuclear reactorUncontrolled fission:Atomic bomb(235U or 239Pu bomb)

  17. Pressurized Water Reactor From: Joseph Gonyeau, P.E., Virtual Nuclear Tourist http://www.nucleartourist.com/

  18. Advantages of Nuclear Power:1. Clean (no air pollution, including greenhouse gases)2. Safe compared with other fuels3. Price competitive with fossil fuels4. 100 year supply of 235U5. Infinite supply of 238U (if we use breeder reactors)

  19. Woolsey-Swanson Rule:People would rather live with a problem they cannot solve than accept a solution they cannot understand.

  20. UM Reactor Core Blue Cerenkov radiation

  21. Average Binding energy per nucleon

  22. Nuclear fusion2D + 2D –—> larger nuclei + LOTS OF ENERGY!!

  23. “Theta Pinch”electromagnetic squeezingto producefusion

  24. Nuclear Shell ModelDiscrete energy levelsfor protons and neutronsanddiscrete energies for radiationwhen energy levels change

  25. Radiation types:Alpha particle (2 Ps + 2 Ns: 4He nucleus)Beta particle (- or + electron)Gamma ray (photon energy packet)NeutronsCosmic Rays

  26. Radiation Exposure

  27. Sources of radiation exposure:1. Natural Exposure2. Man-made Exposure

  28. Natural Exposure:1. Radon gas2. Cosmic Rays3. External Environment4. Internal: The Body

  29. 238U Decay Chain

  30. Cosmic Rays:1. Mostly cosmic ray muons2. 14C and other products

  31. Cosmic Radiation

  32. Man-made radiation:1. X-rays2. Nuclear medicine3. Consumer products (food, etc.)

  33. Sources of Radiation Exposure From: National Institutes of Health

  34. Useful Radiation Effects INuclear PowerMedical: Diagnostic scans, tracers Magnetic resonance imaging Cancer radiation treatment Plutonium powered pacemaker Medical, dental sterilization

  35. Useful Radiation Effects IIPolymer cross-linking Shrink tubing (turkey wrapping) Ultra-strong materials (eg Kevlar) Tires (replaces vulcanization) FlooringFood irradiation Sterilization of meat Disinfestation of grain and spices Increasing shelf life (eg, fruits)

  36. Useful Radiation Effects IIIAbsolute sterilization of food: hospitals and space travel Radioactive dating Insect control Semiconductor doping Testing of space computer technology Environmental studies: air, global warming, ozone

  37. The Nuclear Waste Test

  38. Test Question #1 Suppose that all of the electrical energy for the world for the next 500 years were obtained from breeder reactors. Further suppose that all of the nuclear waste from these reactors were dissolved and spread uniformly throughout the oceans of the world.

  39. Which statement is true: • The oceans would be a vast wasteland, unable to support life. • 2. Much death and damage to ocean life would be caused. • 3. Any effect would be so small that it would be virtually impossible to see

  40. Which statement is true: • The oceans would be a vast wasteland, unable to support life. • 2. Much death and damage to ocean life would be caused. • 3. Any effect would be so small that it would be virtually impossible to see

  41. Test Question #2 Consider all of the people throughout history who have been exposed to man-made nuclear radiation, such as Hiroshima and Nagasaki, Chernobyl, Three Mile Island, nuclear bomb tests, accidental spills, etc.

  42. Which number most nearly approximates how many children conceived and born later to these people suffered genetic damage due to a parent’s exposure? • ~ millions • ~ thousands • zero

  43. Which number most nearly approximates how many children conceived and born later to these people suffered genetic damage due to a parent’s exposure? • ~ millions • ~ thousands • zero

  44. Reference materials:General:Nuclear Physics and Society web siteNuclear Reactors and Power:Joseph Gonyeau's Virtual Nuclear Tourist! Nuclear Plants Around the World

  45. A Nuclear Sunset

  46. The EndSee you in January! We are on the web at http://www.physics.umd.edu/lecdem/ Animated Gifs compliments of bellsnwhistles.com

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