1. BNEN – Nuclear Energy Intro W. D’haeseleer 2015-2016 What is Radioactivity? BNEN Nuclear Energy: Intro William D’haeseleer

2. BNEN – Nuclear Energy Intro W. D’haeseleer 2015-2016 Chemical elements Periodic Table (Mendeleev)

3. BNEN – Nuclear Energy Intro W. D’haeseleer 2015-2016

4. Chemical elements Periodic Table (Mendeleev) Focuses on the electrons in atoms

5. BNEN – Nuclear Energy Intro W. D’haeseleer 2015-2016 Chemical elements Periodic Table (Mendeleev) Focuses on the electrons in atoms

6. BNEN – Nuclear Energy Intro W. D’haeseleer 2015-2016 Chemical elements Periodic Table (Mendeleev) Focuses on the electrons in atoms

7. BNEN – Nuclear Energy Intro W. D’haeseleer 2015-2016 Chemical elements Periodic Table (Mendeleev) Focuses on the electrons in atoms

8. BNEN – Nuclear Energy Intro W. D’haeseleer 2015-2016 Atoms vs Nuclei & Electron Cloud (neutral) atom = nucleus + Z electrons ion = ionized atom nucleus = Z protons + N neutrons = A nucleons Matter is basically “empty space”, but electrons move at very high speed

9. BNEN – Nuclear Energy Intro W. D’haeseleer 2015-2016 Exited states in atoms Stationary states Hydrogen Mercury (simplified)

10. BNEN – Nuclear Energy Intro W. D’haeseleer 2015-2016 Exited states in atoms Transitions in eV range Emitted e.m. radiation = UV or X rays 1 eV = 1.6 10 -19 Joule

11. BNEN – Nuclear Energy Intro W. D’haeseleer 2015-2016 Transitions btwn shells in atoms

12. BNEN – Nuclear Energy Intro W. D’haeseleer 2015-2016 Exited states in nuclei Nuclei vibrate & rotate

13. BNEN – Nuclear Energy Intro W. D’haeseleer 2015-2016 Exited states in nuclei Nuclei vibrate & rotate

14. BNEN – Nuclear Energy Intro W. D’haeseleer 2015-2016 Exited states in nuclei Stationary states Transitions in MeV range Emitted e.m. radiation = Gamma rays

15. BNEN – Nuclear Energy Intro W. D’haeseleer 2015-2016

16. Electromagnetic spectrum UV & X rays Gamma rays Common e.m. waves: Radio TV Micro-wave I.R. (heat) visible

17. BNEN – Nuclear Energy Intro W. D’haeseleer 2015-2016 Elements vs Isotopes Chemical elements characterized by Z –Number of protons = Z –Number of electrons = Z If same Z but different N, particles called isotopes of chemical element –E.g., Hydrogen has three isotopes –Sometimes “isotope” used as generic name of all nuclei/atoms with all kinds of Z & A.

18. BNEN – Nuclear Energy Intro W. D’haeseleer 2015-2016 Some light Isotopes proton neutron

19. BNEN – Nuclear Energy Intro W. D’haeseleer 2015-2016 208 Pb last stable nucleus Rank all stable isotopes in (N,Z) plot Every stable isotope represented by a black dot

20. BNEN – Nuclear Energy Intro W. D’haeseleer 2015-2016 Chart of Nuclides About 1400 isotopes known About 280 stable About 1220 unstable

21. BNEN – Nuclear Energy Intro W. D’haeseleer 2015-2016 Chart of Nuclides Too many protons Too many neutrons

22. BNEN – Nuclear Energy Intro W. D’haeseleer 2015-2016 Chart of Nuclides N Z 208 Pb last stable nucleus

23. BNEN – Nuclear Energy Intro W. D’haeseleer 2015-2016 43 Tc 61 Pm Chart of Nuclides N Z

24. BNEN – Nuclear Energy Intro W. D’haeseleer 2015-2016 Chart of Nuclides N Z Too many protons Too many neutrons

25. BNEN – Nuclear Energy Intro W. D’haeseleer 2015-2016 Radioactive decay Beta - decay when too many neutrons: neutron  proton + electron (+ anti neutrino) A remains same Z  Z+1 & N  N-1

26. BNEN – Nuclear Energy Intro W. D’haeseleer 2015-2016 Radioactive decay Beta + decay when too many protons: proton  neutron + positron (+ neutrino) A remains same Z  Z-1 & N  N+1

27. BNEN – Nuclear Energy Intro W. D’haeseleer 2015-2016 Chart of Nuclides N Z Heavy unstable isotopes

28. BNEN – Nuclear Energy Intro W. D’haeseleer 2015-2016 Chart of Nuclides N Z Heavy unstable isotopes Wish to move downward quickly

29. BNEN – Nuclear Energy Intro W. D’haeseleer 2015-2016 Radioactive decay Emission two protons & two neutrons A  A – 4 & Z  Z – 2 N  N - 2

30. BNEN – Nuclear Energy Intro W. D’haeseleer 2015-2016 Summary radioactive decay Alpha decay Beta decay beta- decay beta+ decay Energetic alpha Energetic electron Energetic positron

31. BNEN – Nuclear Energy Intro W. D’haeseleer 2015-2016 Alpha energies Well defined energies of emitted alpha particles upon transition Typically ~ 4-10 MeV

32. BNEN – Nuclear Energy Intro W. D’haeseleer 2015-2016 Beta energies Energy variable (because neutrino) Beta min = electronBeta plus = positron

33. BNEN – Nuclear Energy Intro W. D’haeseleer 2015-2016 Beta energies Emitted energies vary considerably dependent on isotope

34. BNEN – Nuclear Energy Intro W. D’haeseleer 2015-2016 And Gamma rays?

35. BNEN – Nuclear Energy Intro W. D’haeseleer 2015-2016 Gamma decay Gamma decay typically follows beta decay Beta decay often to excited state of daughter Excited daughter then decays very quickly to lower state

36. BNEN – Nuclear Energy Intro W. D’haeseleer 2015-2016 Gamma decay (after beta decay)

37. BNEN – Nuclear Energy Intro W. D’haeseleer 2015-2016 Beta - Gamma decay E.g., beta min decay

38. BNEN – Nuclear Energy Intro W. D’haeseleer 2015-2016 Alpha - Beta - Gamma decay 212 Bi has all three decay modes

39. BNEN – Nuclear Energy Intro W. D’haeseleer 2015-2016 Alpha - Beta - Gamma decay

40. BNEN – Nuclear Energy Intro W. D’haeseleer 2015-2016 When radioactive decay? Start from N° radioactive isotopes λ = desintegration constant = probability for decay per second

41. BNEN – Nuclear Energy Intro W. D’haeseleer 2015-2016 When radioactive decay? Half life = time that half of the isotopes has decayed Average life time isotope

42. BNEN – Nuclear Energy Intro W. D’haeseleer 2015-2016 When radioactive decay? Activity = number of disintegrations per second = Becquerel = Bq = [1/s] Old unit = Curie = Ci ; 1 Ci = 37 GBq

43. BNEN – Nuclear Energy Intro W. D’haeseleer 2015-2016 Radioactive chains Very often daughter also unstable  Radioactive chains N1N1 N2N2 N3N3 λ1λ1 λ2λ2

44. BNEN – Nuclear Energy Intro W. D’haeseleer 2015-2016 Natural Radioactivity Many unstable isotopes exist in nature, and originate from nature –Cosmogenic isotopes –Primordial isotopes Very long lived lighter than Pb Natural radioactive chains 238 U 235 U 232 Th –Transuranic elements & Np decay series

45. BNEN – Nuclear Energy Intro W. D’haeseleer 2015-2016 Natural Radioactivity Many unstable isotopes exist in nature, and originate from nature –Cosmogenic isotopes –Primordial isotopes Very long lived lighter than Pb Natural radioactive chains 238 U 235 U 232 Th –Transuranic elements & Np decay series

46. BNEN – Nuclear Energy Intro W. D’haeseleer 2015-2016 Cosmogenic isotopes Interaction of cosmic radiation produces protons & neutrons which interact with with nuclei from atmosphere Produce radioactive isotopes Typical examples:

47. BNEN – Nuclear Energy Intro W. D’haeseleer 2015-2016 Cosmogenic Example C-14

48. BNEN – Nuclear Energy Intro W. D’haeseleer 2015-2016 Cosmogenic isotopes Tritium / pure Beta- decay T 1/2 = 12.3 year Carbon 14 / pure Beta- decay T 1/2 = 5715 year Phosphor 32 / pure Beta- decay T 1/2 = 14.3 days

49. BNEN – Nuclear Energy Intro W. D’haeseleer 2015-2016 Cosmogenic isotopes Tritium  Global inventory ~ 1.3 EBq T 1/2 = 12.3 year Due to weapons tests in 60’s up to 260 EBq (already gone) Carbon 14  ~ 230 Bq/kg of Carbon in T 1/2 = 5715 year living tissue Phosphor 32  of minor importance for T 1/2 = 14.3 days living tissues

50. BNEN – Nuclear Energy Intro W. D’haeseleer 2015-2016 Natural Radioactivity Many unstable isotopes exist in nature, and originate from nature –Cosmogenic isotopes –Primordial isotopes Very long lived lighter than Pb Natural radioactive chains 238 U 235 U 232 Th –Transuranic elements & Np decay series

51. BNEN – Nuclear Energy Intro W. D’haeseleer 2015-2016 Primordial radionuclides Very long lived – lighter than Pb Formed at time or before formation solar system Typical examples:

52. BNEN – Nuclear Energy Intro W. D’haeseleer 2015-2016 Primordial radionuclides Potassium 40 89% Beta- decay to Ca-40 with E max =1.3 MeV 11% EC to Ar-40, with Gamma of 1.46 MeV Typically in human body ~ 50 Bq/kg T 1/2 = 1.26 10 9 y

53. 53 Primordial radionuclides Potassium 40 Decay products are Ca-40 or Ar-40 (both stable) Present for 2.1% (weight) earth crust and 0.044% sea water K-40 only 0.01117% of natural K (mostly K-39) K present for about 0.15 kg in human body Further info from [Wade Alison, “Radiation and Reason”, 2009, p 51] T 1/2 = 1.26 10 9 y BNEN – Nuclear Energy Intro W. D’haeseleer 2015-2016

54. Potassium-40 54 β-β- EC γ 40 K 40 Ar 40 Ca 1.46 MeV E e,max 1,3 MeV BNEN – Nuclear Energy Intro W. D’haeseleer 2015-2016

55. Primordial radionuclides

56. BNEN – Nuclear Energy Intro W. D’haeseleer 2015-2016 Natural Radioactivity Many unstable isotopes exist in nature, and originate from nature –Cosmogenic isotopes –Primordial isotopes Very long lived lighter than Pb Natural radioactive chains 238 U 235 U 232 Th –Transuranic elements & Np decay series

57. BNEN – Nuclear Energy Intro W. D’haeseleer 2015-2016 Natural Radioactive Chains

58. BNEN – Nuclear Energy Intro W. D’haeseleer 2015-2016 Natural Radioactive Chains U-238 U-235 Th-232

59. BNEN – Nuclear Energy Intro W. D’haeseleer 2015-2016 Natural Radioactive Chains The Thorium series (Th-232) Ref: Yang & Hamilton, 1996

60. BNEN – Nuclear Energy Intro W. D’haeseleer 2015-2016 Th-232 natural series

61. BNEN – Nuclear Energy Intro W. D’haeseleer 2015-2016 Th-232 natural series

62. BNEN – Nuclear Energy Intro W. D’haeseleer 2015-2016 Natural Radioactive Chains The Actinium series (U-235) Ref: Yang & Hamilton, 1996

63. BNEN – Nuclear Energy Intro W. D’haeseleer 2015-2016 Natural Radioactive Chains The Uranium series (U-238) Ref: Yang & Hamilton, 1996

64. BNEN – Nuclear Energy Intro W. D’haeseleer 2015-2016 U-238 natural series

65. BNEN – Nuclear Energy Intro W. D’haeseleer 2015-2016 Radioactive chains U-238t 1/2 = 4.5 10 9 years U-235t 1/2 = 0.7 10 9 years Th-232t 1/2 = 14 10 9 years

66. BNEN – Nuclear Energy Intro W. D’haeseleer 2015-2016 Radioactive chains

67. BNEN – Nuclear Energy Intro W. D’haeseleer 2015-2016 Natural Radioactivity Many unstable isotopes exist in nature, and originate from nature –Cosmogenic isotopes –Primordial isotopes Very long lived lighter than Pb Natural radioactive chains 238 U 235 U 232 Th –Transuranic elements & Np decay series

68. BNEN – Nuclear Energy Intro W. D’haeseleer 2015-2016 Transuranics & Np decay series A fourth radioactive decay chain has existed in the past, called Np-237 series But T 1/2 = 2.1 10 6 year too small Mother isotope was actually Pu-241 T 1/2 = 14 year Only surviving member Bi-209 T 1/2 = 2 10 18 year; nearly stable

69. BNEN – Nuclear Energy Intro W. D’haeseleer 2015-2016 Natural Radioactive Chains The Neptunium series (Np-237) Ref: Yang & Hamilton, 1996 Bi-209

70. BNEN – Nuclear Energy Intro W. D’haeseleer 2015-2016 Transuranics & Np decay series Plutonium 239 does exist occur naturally in very small quantities: –From spontaneous fission U-235 & U-238 and then n-absorption in U-238 –In OKLO Gabon, natural fission reactor, naturally produced long time ago (but in mean time almost disappeared)

71. BNEN – Nuclear Energy Intro W. D’haeseleer 2015-2016 Long lived isotopes in nature

72. BNEN – Nuclear Energy Intro W. D’haeseleer 2015-2016 Long lived isotopes in nature Natural uranium –NU consist of 99.3% U-238 & 0.7% U-235 –Density soil ~1 à 1.6 10 3 kg/m 3 –Make pit/hole of 20m x 20m x 10m in yard  Leads to about 6 to 10 kg natural uranium

73. BNEN – Nuclear Energy Intro W. D’haeseleer 2015-2016 Long lived isotopes in nature

74. BNEN – Nuclear Energy Intro W. D’haeseleer 2015-2016 Some orders of magnitude Natural Radioactivity in oceans: –U-238 4-5 10 19 Bq (x 14 because progeny) –K-40 1.85 10 22 Bq Natural Radioactivity in earth crust: –Contiguous states US, 1 km deep; about 3-4 10 23 Bq Natural Radioactivity body (70kg) –About 8000 Bq (~ 55% from Ka-40, 40% from C-14) Rn-222 Radioactivity in buildings in Belgium –About 50 Bq/m 3 (Flanders ~20-30; Ardennes ~70-80)

75. BNEN – Nuclear Energy Intro W. D’haeseleer 2015-2016 Artificial Radioactivity From isotopes –Produced in laboratories & industries for medical purposes, measuring techniques –Produced in nuclear reactors –Released in nature by atomic weapons tests No distinction btwn natural & artificial radioactivity –Also alpha, beta, gamma, neutrons –Energetic ionizing particles

76. BNEN – Nuclear Energy Intro W. D’haeseleer 2015-2016 Artificial Radioactivity Examples Th-233  β T 1/2 = 22 min U-239  β T 1/2 = 23.2 min Pu-239  α T 1/2 = 2.4 10 4 year

77. BNEN – Nuclear Energy Intro W. D’haeseleer 2015-2016 Rare “decay” modes Two other occurring decay modes –Spontaneous break up / spontaneous fission –Neutron emission (in stead of gamma emiss)

78. BNEN – Nuclear Energy Intro W. D’haeseleer 2015-2016 Spontaneous fission U-238 undergoes spontaneous breakup in large fragments = fission Process in “parallel” with alpha decay Probab fission = 5 10 -7 probab alpha decay (0.5 ppm) 238 U Example: 1 g U-238 undergoes 20 fissions/h Leads to 2-3 neutrons per fission Note: also heavier elements undergo sf

79. BNEN – Nuclear Energy Intro W. D’haeseleer 2015-2016 Spontaneous fission U-238 undergoes spontaneous breakup in large fragments = fission 238 U Example: 1 g U-238 undergoes 20 fissions/h Leads to 2-3 neutrons per fission Recall: in yard pit/hole of 20m x 20m x 10m  120000 à 200000 f/h  or 33 à 56 f/s

80. BNEN – Nuclear Energy Intro W. D’haeseleer 2015-2016 Neutron emission after β decay After β decay, if energy excited state of daughter larger than “virtual energy” (binding energy weakest bound neutron) in neighbor: Then n emission rather than γ emission Called “delayed neutrons”

81. BNEN – Nuclear Energy Intro W. D’haeseleer 2015-2016 Ionizing particles Alpha, beta, gamma Fission fragments Neutrons  Interaction of these energetic particles with matter  May lead to biological damage  But to be considered quantitatively!

82. BNEN – Nuclear Energy Intro W. D’haeseleer 2015-2016 References Some basic examples (a.o.)