1. General ChemistryPrinciples and Modern Applications Petrucci Harwood Herring 8th EditionChapter 26: Nuclear Chemistry Philip DuttonUniversity of Windsor, Canada N9B 3P4Prentice-Hall 2002

2. Contents26-1 The Phenomenon of Radioactivity26-2 Naturally Occurring Radioactive Isotopes26-3 Nuclear Reactions and Artificially Induced Radioactivity26-4 Transuranium Elements26-5 Rate of Radioactive Decay26-6 Nuclear Stability26-7 Nuclear Fission Prentice-HallGeneral Chemistry: ChapterSlide 2 of 47 26 3. Contents26-8 Nuclear Fusion26-9 Effect of Radiation on Matter26-10 Applications of RadioisotopesFocus On Radioactive Waste DisposalPrentice-HallGeneral Chemistry: ChapterSlide 3 of 4726 4. 26-1 The Phenomenon of Radioactivity Alpha Particles, : Nuclei of He atoms, 42He2+. Low penetrating power, stopped by a sheet of paper. 92U 238 234 90Th + 2He2+4The sum of the mass numbers must be the same on both sides.The sum of the atomic numbers must be the same on both sidesPrentice-Hall General Chemistry: ChapterSlide 4 of 47 26 5. Beta Particles, - Electrons originating from the nuclei of atoms in anuclear decay process. Simplest process is the decay of a free neutron:10 n 1p + -1 + 1 090Th234 23491Pa + -10Prentice-Hall General Chemistry: ChapterSlide 5 of 47 26 6. Positrons, + Simplest process is the decay of a free proton: 1 1p 1n ++10 0 Commonly encountered in artificially producedradioactive nuclei of the lighter elements:15P30 14Si30 + +10Prentice-HallGeneral Chemistry: ChapterSlide 6 of 4726 7. Electron Capture and Gamma Rays Electron capture achieves the same effect aspositron emission.Ti + -1 202810 20180Hg 201 80Hg + X-ray Gamma rays. Highly penetrating energetic photons. 92U 238 90Th234+ 2He2+ 4 90Th234 23490Th + Prentice-Hall General Chemistry: ChapterSlide 7 of 47 26 8. Tunneling Out of the NucleusPrentice-Hall General Chemistry: ChapterSlide 8 of 47 26 9. 26-2 Naturally Occurring Radioactive Isotopes 92U238Th + 2He2+23490 4 90Th 234 234 91Pa + -1 0 91Pa234 92U234+ -10 Daughter nuclides are new nuclides produced by radioactive decay.Prentice-HallGeneral Chemistry: ChapterSlide 9 of 4726 10. Radioactive Decay Series for 238U92Prentice-Hall General Chemistry: ChapterSlide 10 of 47 26 11. Marie Sklodowska Curie Shared Nobel Prize 1903 Radiation Phenomenon Nobel Prize 1911 Discovery of Po and Ra.Prentice-Hall General Chemistry: ChapterSlide 11 of 47 26 12. 26-3 Nuclear Reactions andArtificially Induced Radioactivity Rutherford 1919.N + 2He 14 74 178O + 1H 1 Irene Joliot-Curie.2413Al + 2He 4 15P30 + 1n 0 1514+130 P 30Si + 0Shared Nobel Prize 1938Prentice-Hall General Chemistry: ChapterSlide 12 of 47 26 13. 26-4 Transuranium Elements92 U238+ 0n 1 92 U 239 +92 U 23993 Np239 + 0 -1 98 Cf249+ 15 N 7105 U 260 + 4 0n 1Prentice-HallGeneral Chemistry: ChapterSlide 13 of 4726 14. CyclotronPrentice-Hall General Chemistry: ChapterSlide 14 of 47 26 15. 26-5 Rate of Radioactive Decay The rate of disintegration of a radioactive material called the activity, A, or the decay rate is directlyproportional to the number of atoms present. Ntln = -t N0 Prentice-HallGeneral Chemistry: ChapterSlide 15 of 47 26 16. Radioactive Decay of a Hypothetical 31P SamplePrentice-Hall General Chemistry: ChapterSlide 16 of 47 26 17. Table 26.1 Some Representative Half-LivesPrentice-Hall General Chemistry: ChapterSlide 17 of 47 26 18. Radiocarbon Dating In the upper atmosphere 14C forms at a constantrate:7N14 + 0n 16C14+ 1H1 6C14 7N14 + -1 0T = 5730 Years Live organisms maintain 14C/13C at equilibrium. Upon death, no more 14C is taken up and ratiochanges. Measure ratio and determine time since death.Prentice-HallGeneral Chemistry: ChapterSlide 18 of 4726 19. Mineral Dating Ratio of 206Pb to 238U gives an estimates of the age ofrocks. The overall decay process (14 steps) is:23892U Pb + 8 2He2+ + 6 -120682 40 The oldest known terrestrial mineral is about4.5 billion years old. This is the time since that mineral solidified.Prentice-HallGeneral Chemistry: ChapterSlide 19 of 4726 20. 26-6 Energetics of Nuclear ReactionsE = mc2 All energy changes are accompanied by masschanges (m). In chemical reactions E is too small to notice m. In nuclear reactions E is large enough to see m.1 MeV = 1.602210-13 JIf m = 1.0 u then E =1.492410-10 J or 931.5 MeVPrentice-Hall General Chemistry: ChapterSlide 20 of 47 26 21. Nuclear Binding EnergyPrentice-Hall General Chemistry: ChapterSlide 21 of 47 26 22. Average Binding Energy as a Function of Atomic NumberPrentice-Hall General Chemistry: ChapterSlide 22 of 47 26 23. 26-7 Nuclear StabilityShell TheoryPrentice-HallGeneral Chemistry: ChapterSlide 23 of 4726 24. Neutron-to-Proton RatioPrentice-Hall General Chemistry: ChapterSlide 24 of 47 26 25. 26-8 Nuclear FissionPrentice-HallGeneral Chemistry: ChapterSlide 25 of 4726 26. Nuclear Fission Enrico Fermi 1934. In a search for transuranium elements U was bombarded with neutrons. emission was observed from the resultant material. Otto Hahn, Lise Meitner and Fritz Stassman 1938. Z not greater than 92. Ra, Ac, Th and Pa were found. The atom had been split.Prentice-Hall General Chemistry: ChapterSlide 26 of 47 26 27. Nuclear FissionU + 1 0n235921 Fission fragments + 3 0 n + 3.2010-11 J 1Energy released is 8.2107 kJ/g U.This is equivalent to the energy from burning 3 tons of coalPrentice-HallGeneral Chemistry: ChapterSlide 27 of 4726 28. Nuclear ReactorsPrentice-HallGeneral Chemistry: ChapterSlide 28 of 4726 29. The Core of a ReactorPrentice-Hall General Chemistry: ChapterSlide 29 of 47 26 30. Nuclear Accidents Three Mile Island partial meltdown due to lost coolant. Chernobyl Fault of operators and testing safety equipment too close to the limit. France safe operation provides 2/3of power requirements forthe country.Prentice-HallGeneral Chemistry: ChapterSlide 30 of 4726 31. Breeder Reactors Fertile reactors produce other fissile material.1n 92U + 1 0 92U238 23992U 93Np+ -1 2392390 93Np 94Pu -1 239239+0Prentice-Hall General Chemistry: ChapterSlide 31 of 47 26 32. Disadvantages of Breeder Reactors Liquid-metal-cooled fast breeder reactor (LMFBR). Sodium becomes highly radioactive in the reactor. Heat and neutron production are high, so materials deteriorate more rapidly. Radioactive waste and plutonium recovery. Plutonium is highly poisonous and has a long half life(24,000 years).Prentice-Hall General Chemistry: ChapterSlide 32 of 47 26 33. 26-9 Nuclear Fusion Fusion produces the energy of the sun. Most promising process on earth would be: 1H 2+ 1H3 4 2 He + 0 n1 Plasma temperatures over 40,000,000 K to initiatea self-sustaining reaction (we cant do this yet). Lithium is used to provide tritium and also act asthe heat transfer material handling problems. Limitless power once we start it up.Prentice-HallGeneral Chemistry: ChapterSlide 33 of 4726 34. TokomakPrentice-Hall General Chemistry: ChapterSlide 34 of 47 26 35. 26-10 Effect of Radiation on Matter Ionizing radiation. Power described in terms of the number of ion pairs per cm of path through a material. P > P > P Primary electrons ionized by the radioactive particle may have sufficient energy to produce secondary ionization.Prentice-Hall General Chemistry: ChapterSlide 35 of 47 26 36. Ionizing RadiationPrentice-Hall General Chemistry: ChapterSlide 36 of 47 26 37. Geiger-Mller CounterPrentice-Hall General Chemistry: ChapterSlide 37 of 47 26 38. Radiation Dosage1 rad (radiation absorbed dose) = 0.001 J/kg matter1 rem (radiation equivalent for man) = radQ Q = relative biological effectivenessPrentice-Hall General Chemistry: ChapterSlide 38 of 47 26 39. Table 26.4 Radiation UnitsPrentice-Hall General Chemistry: ChapterSlide 39 of 47 26 40. 26-11 Applications of Radioisotopes Cancer therapy. In low doses, ionizing radiation induces cancer. In high doses it destroys cells. Cancer cells are dividing quickly and are more susceptible to ionizing radiation than normal cells. The same is true of chemotherapeutic approaches.Prentice-HallGeneral Chemistry: ChapterSlide 40 of 4726 41. Radioactive Tracers Tag molecules or metals with radioactive tags andmonitor the location of the radioactivity with time. Feed plants radioactive phosphorus. Incorporate radioactive atoms into catalysts in industry to monitor where the catalyst is lost to (and how to recover it or clean up the effluent). Iodine tracers used to monitor thyroid activity.Prentice-Hall General Chemistry: ChapterSlide 41 of 47 26 42. Structures and Mechanisms Radiolabeled (or even simplymass labeled) atoms can beincorporated into molecules. The exact location of thoseatoms can provide insight intothe chemical mechanism of thereaction.Prentice-HallGeneral Chemistry: ChapterSlide 42 of 4726 43. Analytical Chemistry Precipitate ions and weigh them to get a mass ofmaterial. Incorporate radioactive ions in the precipitating mixture and simply measure the radioactivity. Neutron activation analysis. Induce radioactivity with neutron bombardment. Measure in trace quantities, down to ppb or less. Non-destructive and any state of matter can be probed.Prentice-HallGeneral Chemistry: ChapterSlide 43 of 4726 44. Radiation ProcessingPrentice-HallGeneral Chemistry: ChapterSlide 44 of 4726 45. Focus On Radioactive Waste DisposalPrentice-Hall General Chemistry: ChapterSlide 45 of 47 26 46. Focus On Radioactive Waste Disposal Low level waste. Gloves, protective clothing, waste solutions. Short half lives. After 300 years these materials will no longer beradioactive. High level waste. Long half lives. Pu, 24,000 years and extremely toxic. Reprocessing is possible but hazardous. Recovered Pu is of weapons grade.Prentice-Hall General Chemistry: ChapterSlide 46 of 47 26 47. Chapter 26 QuestionsDevelop problem solving skills and base your strategy noton solutions to specific problems but on understanding.Choose a variety of problems from the text as examples.Practice good techniques and get coaching from people whohave been here before.Prentice-HallGeneral Chemistry: ChapterSlide 47 of 4726