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The Promise and Problems of Nuclear Energy II

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The Promise and Problems of Nuclear Energy II

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  1. The Promise and Problems of Nuclear Energy II Lecture #13 HNRT 228 Energy and the Environment

  2. Chapter 6 Summary Again • History of Nuclear Energy • Radioactivity • Nuclear Reactors • Boiling Water Reactor • Fuel Cycle • Uranium Resources • Environmental and Safety Aspects of Nuclear Energy • Chernobyl Disaster • Nuclear Weapons • Storage of High-Level Radioactive Waste • Cost of Nuclear Power • Nuclear Fusion as a Energy Source • Controlled Thermonuclear Reactions • A Fusion Reactor

  3. Review of Fission • 235U will undergo spontaneous fission if a neutron happens by, resulting in: • two sizable nuclear fragments flying out • a few extra neutrons • gamma rays from excited states of daughter nuclei • energetic electrons from beta-decay of daughters • The net result: lots of banging around • generates heat locally (kinetic energy of tiny particles) • for every gram of 235U, get 65 billion Joules, or about 16 million Calories • compare to gasoline at roughly 10 Calories per gram • a tank of gas could be replaced by a 1-mm pellet of 235U!!

  4. Enrichment • Natural uranium is 99.27% 238U, and only 0.72% 235U • 238U is not fissile, and absorbs wandering neutrons • In order for nuclear reaction to self-sustain, must enrich fraction of 235U to 3–5% • interestingly, it was so 3 billion years ago • now probability of wandering neutron hitting 235U is sufficiently high to keep reaction crawling forward • Enrichment is hard to do: a huge technical roadblock to nuclear ambitions

  5. iClicker Question • Which is closest to the half-life of a neutron? • A 5 minutes • B 10 minutes • C 15 minutes • D 20 minutes • E 30 minutes

  6. iClicker Question • Which is closest to the half-life of a neutron? • A 5 minutes • B 10 minutes • C 15 minutes • D 20 minutes • E 30 minutes

  7. iClicker Question • What is the force that keeps the nucleus together? • A weak force • B strong force • C electromagnetic force • D gravitational force

  8. iClicker Question • What is the force that keeps the nucleus together? • A weak force • B strong force • C electromagnetic force • D gravitational force

  9. iClicker Question • A neutron decays. It has no electric charge. If a proton (positively charged) is left behind, what other particle must come out if the net charge is conserved? • A No other particles are needed. • B A negatively charged particle must emerge as well. • C A positively charged particle must emerge as well. • D Another charge will come out, but it could be either positively charged or negatively charged. • E Neutrons cannot exist individually.

  10. iClicker Question • A neutron decays. It has no electric charge. If a proton (positively charged) is left behind, what other particle must come out if the net charge is conserved? • A No other particles are needed. • B A negatively charged particle must emerge as well. • C A positively charged particle must emerge as well. • D Another charge will come out, but it could be either positively charged or negatively charged. • E Neutrons cannot exist individually.

  11. iClicker Question • How many neutrons in U-235? • A 141 • B 142 • C 143 • D 144 • E 145

  12. iClicker Question • How many neutrons in U-235? • A 141 • B 142 • C 143 • D 144 • E 145

  13. iClicker Question • How many neutrons in Pu-239? • A 141 • B 142 • C 143 • D 144 • E 145

  14. iClicker Question • How many neutrons in Pu-239? • A 141 • B 142 • C 143 • D 144 • E 145

  15. iClicker Question • If a substance has a half-life of 30 years, how much will be left after 90 years? • A one-half • B one-third • C one-fourth • D one-sixth • E one-eighth

  16. iClicker Question • If a substance has a half-life of 30 years, how much will be left after 90 years? • A one-half • B one-third • C one-fourth • D one-sixth • E one-eighth

  17. iClicker Question • If one of the neutrons in carbon-14 (carbon has 6 protons) decays into a proton, what nucleus is left? • A carbon-13, with 6 protons, 7 neutrons • B carbon-14, with 7 protons, 7 neutrons • C boron-14, with 5 protons, 9 neutrons • D nitrogen-14, with 7 protons, 7 neutrons • E nitrogen-15, with 7 protons, 8 neutrons

  18. iClicker Question • If one of the neutrons in carbon-14 (carbon has 6 protons) decays into a proton, what nucleus is left? • A carbon-13, with 6 protons, 7 neutrons • B carbon-14, with 7 protons, 7 neutrons • C boron-14, with 5 protons, 9 neutrons • D nitrogen-14, with 7 protons, 7 neutrons • E nitrogen-15, with 7 protons, 8 neutrons

  19. iClicker Question • Basically, what is the nature of the alpha particle? • A an electron • B a proton • C a helium nucleus • D a uranium nucleus • E an iron nucleus

  20. iClicker Question • Basically, what is the nature of the alpha particle? • A an electron • B a proton • C a helium nucleus • D a uranium nucleus • E an iron nucleus

  21. iClicker Question • Basically, what is the nature of the beta particle? • A an electron • B a proton • C a helium nucleus • D a uranium nucleus • E an iron nucleus

  22. iClicker Question • Basically, what is the nature of the beta particle? • A an electron • B a proton • C a helium nucleus • D a uranium nucleus • E an iron nucleus

  23. Brief History of Nuclear Power 1938– Scientists study Uranium nucleus 1941 – Manhattan Project begins 1942 – Controlled nuclear chain reaction 1945 – U.S. uses two atomic bombs on Japan 1949 – Soviets develop atomic bomb 1952 – U.S. tests hydrogen bomb 1955 – First U.S. nuclear submarine

  24. “Atoms for Peace” Program to justify nuclear technology Proposals for power, canal-building, exports First commercial power plant, Illinois 1960

  25. Emissions Free • Nuclear energy annually prevents • 5.1 million tons of sulfur • 2.4 million tons of nitrogen oxide • 164 metric tons of carbon • Nuclear often pitted against fossil fuels • Some coal contains radioactivity • Nuclear plants have released low-level radiation

  26. Early knowledge of risks • 1964 Atomic Energy Commission report on possible reactor accident • 45,000 dead • 100,000 injured • $17 billion in damages • Area the size of Pennsylvania contaminated

  27. States with nuclear power plant(s)

  28. Nuclear power around the globe • 17% of world’s electricity from nuclear power • U.S. about 20% (2nd largest source) • 431 nuclear plants in 31 countries • 103 of them in the U.S. • Built none since 1970s • U.S. firms have exported nukes. • Push from Bush/Obama for new nukes.

  29. Countries Generating Most Nuclear Power

  30. Nuclear Fuel Cycle • Uranium mining and milling • Conversion and enrichment • Fuel rod fabrication • POWER REACTOR • Reprocessing, or • Radioactive waste disposal • Low-level in commercial facilities • High level at plants or underground repository

  31. iClicker Question • About what percentage of U.S. electricity is derived from nuclear power? • A 10 • B 20 • C 30 • D 40 • E 50

  32. iClicker Question • About what percentage of U.S. electricity is derived from nuclear power? • A 10 • B 20 • C 30 • D 40 • E 50

  33. iClicker Question • Which of the following countries has the highest percentage of electricity generated by nuclear power? • A United States • B United Kingdom (Great Britain) • C Japan • D France • E Russia

  34. iClicker Question • Which of the following countries has the highest percentage of electricity generated by nuclear power? • A United States • B United Kingdom (Great Britain) • C Japan • D France • E Russia

  35. Front end: Uranium mining and milling

  36. Uranium tailingsand radon gas Deaths of Navajominers since 1950s

  37. Radioactivity Basics Radioactivity – The spontaneous nuclear transformation of an unstable atom that often results in the release of radiation, also referred to as disintegration or decay. Units Curie(Ci) the activity in one standard gram of Radium = 3.7 x 1010 disintegrations per second Becquerel (Bq) 1 disintegration per second – International Units (SI)

  38. Radioactivity Basics Radiation – Energy in transit in the form of electromagnetic waves (gamma-γ or x-ray), or high speed particles ( alpha-α, beta-β, neutron-η, etc.) Ionizing Radiation – Radiation with sufficient energy to remove electrons during interaction with an atom, causing it to become charged or ionized. • Can be produced by radioactive decay or by accelerating charged particles across an electric potential.

  39. Radioactivity Basics Roentgen Rthe unit of exposure to Ionizing Radiation. The amount of γ or x-ray radiation required to produce 1.0 electrostatic unit of charge in 1.0 cubic centimeter of dry air. Radthe unit of absorbed dose. Equal to 100 ergs per gram of any material from any radiation. SI unit = Gray 1 Gray = 100 rads REMthe unit of absorbed dose equivalent. The energy absorbed by the body based on the damaging effect for the type of radiation. REM =Rad x Quality Factor SI unit = Sievert 1 Sv = 100 Rem

  40. iClicker Question • Which of the following describes the Roentgen? • A the unit of absorbed dose equivalent. • B the unit of absorbed dose. • C the unit of exposure to ionizing radiation • D all of the above • E none of the above

  41. iClicker Question • Which of the following describes the Roentgen? • A the unit of absorbed dose equivalent. • B the unit of absorbed dose. • C the unit of exposure to ionizing radiation • D all of the above • E none of the above

  42. iClicker Question • Which of the following describes the RAD? • A the unit of absorbed dose equivalent. • B the unit of absorbed dose. • C the unit of exposure to ionizing radiation • D all of the above • E none of the above

  43. iClicker Question • Which of the following describes the RAD? • A the unit of absorbed dose equivalent. • B the unit of absorbed dose. • C the unit of exposure to ionizing radiation • D all of the above • E none of the above

  44. iClicker Question • Which of the following describes the REM? • A the unit of absorbed dose equivalent. • B the unit of absorbed dose. • C the unit of exposure to ionizing radiation • D all of the above • E none of the above

  45. iClicker Question • Which of the following describes the REM? • A the unit of absorbed dose equivalent. • B the unit of absorbed dose. • C the unit of exposure to ionizing radiation • D all of the above • E none of the above

  46. ALARA A philosophy, necessary to maintain personnel exposure or the release of radioactivity to the environment well below applicable limits by means of a good radiation protection plan, through education, administrative controls and safe lab practices. As Low As Reasonably Achievable

  47. ALARA Principles Distance • Inverse Square Law – radiation intensity is inversely proportional to the square of the distance from the source • Use remote handling tools, or work at arms length • Maximize distance from source of radiation

  48. ALARA Principles Shielding • Any material between a source of radiation and personnel will attenuate some of the energy, and reduce exposure • Select proper shielding material for type of radiation, use less dense material for β’s, to minimize Bremsstrahlung (braking) radiation