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Radioactivity & Radioisotopes

Radioactivity & Radioisotopes. University of Lincoln presentation. This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License. In 1913 Soddy proposed the existence of ISOTOPES.

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Radioactivity & Radioisotopes

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  1. Radioactivity & Radioisotopes University of Lincoln presentation This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  2. In 1913 Soddy proposed the existence ofISOTOPES Definition: Atoms of the same elements with different atomic masses Isotopes Frederick Soddy Nobel Prize (Chemistry) 1921 This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  3. Radioactivity discovered in 1896 Henri Becquerel Marie & Pierre Curie This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  4. Stable v. Radioactive Isotopes There are approximately 1,700 isotopes known to exist This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  5. Chart of the Nuclides This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  6. Z N Black squares denote STABLE isotopes This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  7. Nuclear Stability • The stability of the nucleus depends on both N and Z • Z≤20 N=Z N/Z = 1 • 20<Z≤92 N>Z N/Z = 1–1.6 • Z>92 Spontaneous fission • If N/Z < or > stable ratio, the nucleus is radioactive This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  8. Chart of the Nuclides & Radioactivity Z N/Z < 1 N/Z = 1–1.6 Neutron DEFICIENT Neutron RICH N/Z > 1.6 N This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  9. Chart of the Nuclides & Radioactivity E Neutron RICH N/Z <1 Need to gain n + N/Z>1.6 Need to lose n - Neutron DEFICIENT STABLE This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  10. – Decay (Negatron emission) X  X + – A A Z Z+1 Parent Daughter Negatron It is easier to convert a neutron to a proton, than expel a neutron from the nucleus n  p This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  11.  Decay – decay (nearly) always results in a daughter in an excited state – if this excited state is fairly long-lived it is called a meta-stable state (m) XS energy is lost by expelling a -ray A E X Z Am X – Z+1  A X Z+1 This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  12. + Decay (Positron emission) X  X + + A A Z Z-1 Parent Daughter Positron It is easier to convert a proton to a neutron, than expel a proton from the nucleus p  n This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  13.  Decay • Nuclei that are simply too big (too many n and too many p) need to lose both n and p as quickly as possible  = Helium nucleus He 2 protons + 2 neutrons 4 2 This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  14. Chart of the Nuclides -emitters This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  15. Common Radioactive Emissions This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  16. Half-life (t½) The time taken for the activity of a radioisotope to reach half it’s original value This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  17. Half-Life (t½) For example, suppose we had 20,000 atoms of a radioactive substance. If the half-life is 1 hour, how many atoms of that substance would be left after: This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  18. Radioactivity One half life Two half lifes This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  19. Radioactivity • Decay Equation: At = A0e-t At = activity at time t A0 = activity at time 0 (initial activity)  = decay constant (rate constant) t = time First Order reaction This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  20. Radioactivity • Decay Equation: Ln(At) = Ln(A0)-t Intercept Gradient Straight line graph This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  21. Biological Effects of Radiation • Radiation passing through cells of living tissue  ions and free radicals • These react with compounds in the cell, disrupting or altering the normal metabolic processes This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  22. Biological Effects of Radiation • These changes can result in: • Death of the organism or animal • Reduced ability of cells to divide • Abnormal cell division • Changes in genetic material • Increase in the rate of aging This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  23. Biological Effects of Radiation Mainly due to the radiolysis of water: H2O + radiation  H+ + OH + e– OH immediately reacts with neighbouring molecules, such as proteins and DNA  foreign substances (also H2O2 is formed)  disrupt/change normal metabolic processes The hydroxyl free radical is very reactive This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  24. Cascade effect Initial disruption has now been magnified 8 times Continuation in cascade leads to a level of disruption with which the body cannot cope Radiation Initial disruption 1st generation of foreign substances that cause further disruption This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  25. Penetrating Power of Radiation    n Skin & paper Pb & concrete 5mm brass 6mm Al Very thick concrete (2m) This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  26. Absorbed Dose • The amount of energy absorbed by the tissue • Units – the Gray (Gy) • 1 Gy = 1 Jkg-1 • An absorbed dose of 10 Gy is lethal for most mammals • Although the absorbed energy is very low (10 Jkg-1), the disruption it causes to biological processes in the tissue will result in death This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  27. Dose Equivalent • Different radiation types cause different amounts of damage • In order for ‘dose’ to meaningful, need to be able to define it in terms of ‘damage done’ • Dose equivalent defines the damage done in man • Units – Sievert (Sv) This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  28. Dose Equivalent Dose Equivalent = Absorbed Dose (Gy) x Q Where Q is the empirical quality factor , X Q = 1 Fast n, p Q =10  Q =20 This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  29. Dose Equivalent In theory, 100 Sv -radiation will cause the same biological effect in man as a dose of 100 Sv  radiation BUT the absorbed doses are 100 Gy and 5 Gy, respectively This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  30. Illicit Radioactive Sources Dirty Bombs – Radiation Dispersal Devices (RDD) This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  31. Dirty Bombs • Conventional explosives wrapped in radioactive material • NOT atomic bombs This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  32. Dirty Bombs A SMART PHONE that can detect radiation may soon be helping the police to find the raw materials for radioactive “dirty bombs” before they are deployed. The phones will glean data as the officers carrying them go about their daily business, and the information will be used to draw up maps of radiation that will expose illicit stores of nuclear material. New Scientist (December 2004) This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  33. t½ U-238 = 4.5 x 109 y Not exactly ‘radioactive’ 1 atom will decay every 4.5 x 109 y Depleted Uranium This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  34. Acknowledgements • JISC • HEA • Centre for Educational Research and Development • School of natural and applied sciences • School of Journalism • SirenFM • http://tango.freedesktop.org This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

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