Canadian Nuclear Society Ionising Radiation Workshop

1. Canadian Nuclear Society Ionising Radiation Workshop CNS Team Bryan White John G. Roberts Embrace NORM Revision 13 Some Theory & Orientation 2018-02 Naturally Now with Balloons! Occurring Radioactive Material www.cns-snc.ca 1

2. The ionising radiation workshop kit… Geiger counter USB Interface Computer If your table has a computer, please don’t disturb it -- we’ll get to it shortly. 2

4. This ends the Introduction Some theory and orientation What is Radiation? Electromagnetic Radiation; “particle” radiation Non-ionising & Ionising Radiation (UV, α, β, γ, n, ν) Radioactive decay; periodic table and chart of the nuclides Fission (spontaneous and induced) Detecting Ionising Radiation Outline:

5. Outline continued: • Experiments: • Getting Started • Background Radiation • Potassium-40 • Thorium • Absorbers • Range • Uranium • Sources • Hot Balloons!

6. • Energy emitted by a source travelling through space away from the source. What is Radiation? • Most radiation we encounter is Electro-Magnetic radiation and behaves like visible light. I’m a wave! I’m a particle! (0 rest mass) Just call me a photon. 6

7. Radiation can also refer to sub-atomic particles: most have finite “rest mass” Electrons, protons, neutrons, alpha particles, muons, pions, neutrinos, …? Particles may be released from an atomic nucleus undergoing radioactive decay, or fission, or by an interaction such as “scattering”. Particles may be produced by interactions of other particles -- or may be produced by a particle accelerator. Particle Radiation 7

8. • Popular slang sometimes refers to cooking food in a microwave oven as “Nuking”. How about a microwave oven? • Microwaves are electromagnetic radiation with photons having miniscule energies compared to the binding energy of atomic electrons. • You can’t “Nuke” anything in a microwave oven. NON- Ionising! 8

9. Electromagnetic Radiation non-ionising ionising Figure copied from “Radiation Awareness” PowerPoint File by Health Physics Society, crediting NASA/JPL-Caltech Notice that cell phone radiation falls well into the “non-ionising” region of electromagnetic radiation. 9

10. Radioactive Decay • A radioactive atom has excess energy in its nucleus, but not quite enough to change to a lower energy state, and then... …spontaneously it changes to a lower energy state. • It does this by emitting sub-atomic particles… …and/or electromagnetic energy in the form of gamma radiation… …through quantum-mechanical tunnelling and other mechanisms. • One decay per second is known as one becquerel (Bq) of activity. 10

11. Radioactive Decay • If we start with 100 atoms of a particular nuclide, after a certain time we will have 50 of those atoms left. • This is known as the “half-life” of the nuclide. • After another “half-life”, we will have 25 of those atoms left . 0.39% 0 1 2 3 4 5 6 7 8 11

12. Half-life? If a sealed container holds one gram of a radio- isotope, what is the mass of the container after one half-life?

13. Half-life? The change in its mass is not detectable. Only a miniscule amount of mass is converted to the energy released via E = mc2

14. Described by a wave equation:c =  Energy of the wave is proportional to its frequency:E = h Electromagnetic Radiation • -- frequency [Hz]  -- wavelength [m] h is Planck’s constant h = 4.1 x 10-21 MeV•s (million electron-volt second) or h = 6.62 x 10-34 J•s (joule second)

15. Electromagnetic Radiation • At very high energies, wave effects are small so often it is more useful to consider the radiation as “particles” of light (photons) • Gamma rays are often referred to as “photons”

16. Does not displace electrons from atoms Can break chemical bonds due to heating effects radio waves, microwaves, infrared radiation, visible light Non-Ionising Radiation

17. Able to displace electrons from atoms, often breaking chemical bonds as a consequence UV light, X-rays, Gamma rays Alpha particles, beta particles, neutrons, and even neutrinos (extremely rarely) Ionising Radiation

19. Radioactive Decay Half-life: after 1 half-life, half of starting number of atoms of an isotope remain undecayed www.nndc.bnl.gov/chart/ protons neutrons

21. Online Interactive Chart of the Nuclides http://www.nndc.bnl.gov/chart/ 21

22. N P P Subatomic particle radiation • Most common sources are nuclear events • Emitted by an unstable atomic nucleus as it changes to a more stable one, releasing energy 3H Beta particle e- 3He+ Ion N N P e- e- Anti (electron) Neutrino νe Figure: based on Health Physics Society “Radiation Awareness”

23. Alpha particles Beta particles Gamma rays (electromagnetic radiation) Neutrons Neutrinos Ionising RadiationEmitted from atomic nuclei:

24. • Heavy nuclei that have “2 too many protons” will emit particles made up of 2 protons and 2 neutrons. Alpha Radiation • • These are known as “alpha particles”(the nucleus of a helium atom, 4He+2) • • After alpha emission, there is a nuclide with a different atomic number (a different element): this is known as transmutation. • The resulting nuclide may or may not be radioactive itself. Atomic Number -2, Mass -4 24

25. Alpha Radiation • Heavy Nuclei that have “too many protons” • Emit particles with 2 protons and 2 neutrons (some with gamma) α radon polonium helium

26. Alpha Radiation • Travel only a few centimetres through air • stopped by a sheet of writing paper • Significant harm possible if an -emitter enters the body

27. Radon in the home? Health Canada action level is 200 Bq/m3 (sustained average) US DOE level is 150 Bq/m3 No discernible health effects below ~ 100 Bq/m3 Alpha Radiation

28. Alpha Radiation • If you lived in a dwelling for 100% of the time • and the radon level was 100 Bq/m3 • volume of adult human lungs at ~ 6 L corresponds to 36 alpha decays per minute (~18.9 million per year)

29. Alpha Radiation If the radon level is just 1 Bq/m3 there would be ~ 21 alpha decays per hour in your lungs (~118 thousand per year)

30. Alpha Radiation Zero decays / minute is not an option In principlea single alpha decay could initiate the development of a cancerous cell -- it’s notprobable

31. - - - - - -  Alpha Decay of Radon-222 There is more than 1 alpha decay – Hot Balloons! Neutron No. 134 135 136 Atomic No. 86 55.6 s 25 minutes 3.8235 days    85 56 s 3.71 minutes 2.3 minutes  84 3.098 minutes < 300 ns < 300 ns ~5.6 MeV α

32. - - - - - -  Alpha Decay of Radon-220 Neutron No. 134 135 136 Atomic No. 86 55.6 s 25 minutes 3.8235 days    85 56 s 3.71 minutes 2.3 minutes  84 3.098 minutes < 300 ns < 300 ns

33. - - - - - - - -   Alpha Decay of Radon-219 Neutron No. 133 134 135 136 Atomic No. 86 4 s 55.6 s 25 minutes 3.8235 days     85 1.5 s 56 s 3.71 minutes 2.3 minutes   84 1.53 s 3.098 minutes < 300 ns < 300 ns

35. An aside on energy units Chemistry typical reactions100 to 1000 kJ/mol Nuclear Physics radioactive decay10 keV to 8 MeV 1 ev/particle x 6.02 x 1023 particles/mol x 1 joule/6.24 x 1018 eV 1 ev/particle  9.6 x 104 J/Mol or 96 kJ/mol 1 keV/particle  96 000 kJ/mol 1 MeV/particle  96 x 106 kJ/mol Suggest that when students see: keV think 1000 x more MeV think a million times more energy Check the CNS Energy & power fact sheet!

36. A nucleus that has “1 too many neutrons” will emit an electron – a beta-minus particle A neutron changes into a proton, an electron and an anti-neutrino The electron and anti-neutrino are emitted – along with a photon (gamma) in many cases After beta emission, there remains a nuclide with a different atomic number – a different element. The new nuclide may or may not be radioactive itself. Beta Radiation - 1 Atomic Number +1, Mass - 36

37. Beta Radiation • In beta-minus decay (β-), an electron is ejected from the nucleus (along with an anti-neutrino) as a neutron changes to a proton • Quarks (UDD) 4 Quarks (UUD)

38. A nucleus that has “1 too many protons” will capture an orbital electron, or emit an anti-electron – a positron – a beta-plus particle A proton changes into a neutron by: combining with an electron and emitting a neutrino OR by emitting a positron and a neutrino This form of beta decay also emits a photon (gamma) in most cases. There remains a nuclide with a different atomic number – a different element. The new nuclide may or may not be radioactive itself. Beta Radiation - 2 Atomic Number -1, Mass - 38

39. Beta Radiation • Beta Particles are stopped by aluminum foil • (but energetic Betas can scatter electrons that exit the other side of thin foil) • 6 mm of aluminum will stop most beta • Gamma radiation of modest energy is emitted by many beta decay events

40. Beta Radiation -- a beta emitter

42. - Beta decay of potassium-40 & Electron Capture Neutron No. 20 21 22 Atomic No. 20 >3 x 1021 a 1.02 x 105 a stable - 19 stable 1.25 x 109 a stable EC, + EC, + 18 stable 269 a stable

43. Potassium-40 decays • Beta decay takes 2 forms (more later): • β- decay: • β+ decay: • Electron capture • e- capture:

44. Highest energy EM radiation Interaction with matter similar to X-rays “Collision” with an electron can ionise the atom, breaking a chemical bond. Gamma Radiation

45. Gamma Radiation • Easily penetrates the body • Intense sources (Co-60, Cs-137 and high energy electron accelerators) are used to irradiate tumors • Absorbed by large thickness of water, lead metal or concrete • The atmosphere over your head provides shielding equivalent to 10 m of water 45

46. Ejected from fission of an unstable nucleus Uranium and thorium nuclides undergo spontaneous fission on earth (natural abundance) Neutrons

47. Neutrons • Fission can be induced by neutrons, which can be produced using alpha particles: Beryllium is mixed with an alpha emitter such as Rn-222. There are other reactions such as

48. Intense source is a controlled chain-reaction Critical chain-reaction as in a nuclear reactor, either a thermal neutron reactor, or a fast neutron reactor Sub-critical chain reaction as with a proton particle accelerator impinging on a fissile target Less intense sources: 252Cf spontaneous fission source Alpha particle emitting source (Rn, Am) irradiating a conversion target (Be, Li) Farnsworth-Hirsch fusor (2H-3H, 1H-9B) Neutrons

49. Uranium 235 “Fast”Neutrons “Slow” Neutron Fission Products Heat Nuclear fission <1 eV~103 m/s >1 MeV~107 m/s

50. U-235 fissions in either of two ways (typical): Neutrons