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

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

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

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

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

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

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

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

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

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

11. This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License  Decay E A Z X AmAm Z+1 X –– A X   – 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

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

13. This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License  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 4242

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

15. This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License Common Radioactive Emissions EmissionSymbolNatureMassCharge Alpha  He nucleus4.00262+ Beta  electron0.000551– X-ray EMRNone0 Gamma  EMRNone0 Positron ++ positively charged electron 0.000551+ Proton p 1.00731+ Neutron n neutron1.00870

16. This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License Half-life (t ½ ) The time taken for the activity of a radioisotope to reach half it’s original value

17. This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License Half-Life (t ½ ) 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: TimeNumber of atoms remaining % of atoms remaining 1 Hour (one lifetime) 10,00050% 2 hours (Two lifetimes) 5,00025% 3 hours (Three lifetimes) 2,50012.5%

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

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

20. This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License Radioactivity Decay Equation: Ln(A t ) = Ln(A 0 ) - t InterceptGradient Straight line graph

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

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

23. This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License Biological Effects of Radiation Mainly due to the radiolysis of water: H 2 O + radiation  H + + OH  + e – OH  immediately reacts with neighbouring molecules, such as proteins and DNA  foreign substances (also H 2 O 2 is formed)  disrupt/change normal metabolic processes The hydroxyl free radical is very reactive

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

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

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

27. This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License 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)

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

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

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

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

32. This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License 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)

33. This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License Depleted Uranium t ½ U-238 = 4.5 x 10 9 y –Not exactly ‘radioactive’ –1 atom will decay every 4.5 x 10 9 y

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