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Radiation and Radioactivity (Around Us) Marco Silari

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Radiation and Radioactivity (Around Us) Marco Silari Italian Teachers Programme – September 2016 Radiation and radioactivity (around us) Marco Silari Radiation Protection Group Occupational Health & Safety and Environmental Protection Unit [email protected] M. Silari – Radiation and radioactivity – 6 September 2016 1 Why do you have sheep on the CERN site? M. Silari – Radiation and radioactivity – 6 September 2016 2 The wrong answer… The sheep are there to check radioactivity in the grass… Of course NOT! M. Silari – Radiation and radioactivity – 6 September 2016 3 CERN has a an extensive environmental monitoring plan (which does not involve the use of sheep…) Other environ- Stray radiation Air Water mental samples M. Silari – Radiation and radioactivity – 6 September 2016 4 If I say “radiation” or “radioactivity”, what comes to your mind? M. Silari – Radiation and radioactivity – 6 September 2016 5 I would guess this? Hiroshima, Japan, 6 August 1945 Chernobyl, Ucraine, 26 April 1986 Fukushima, Japan, 11 March 2011 M. Silari – Radiation and radioactivity – 6 September 2016 6 The pacific uses of radiation M. Silari – Radiation and radioactivity – 6 September 2016 7 The pacific uses of ionising radiation Medicine: Radiodiagnostics, nuclear medicine and radiation therapy Energy production Scientific research M. Silari – Radiation and radioactivity – 6 September 2016 8 The pacific uses of ionising radiation Industrial radiography Airport security https://uw-food-irradiation.engr.wisc.edu/Process.html Sterilization of food and medical material M. Silari – Radiation and radioactivity – 6 September 2016 9 The pacific uses of ionising radiation Non-destructive measurements in archeometry THE IRRADIATED MATERIAL DOES NOT BECOME RADIOACTIVE! M. Milazzo, University of Milan M. Silari – Radiation and radioactivity – 6 September 2016 10 What is ionizing radiation? M. Silari – Radiation and radioactivity – 6 September 2016 11 Ionising radiation Gamma radiation – photons or electromagnetic radiation – penetrating – “difficult” to shield Beta radiation – “light” charged particles – limited penetration in matter – “easy” to shield Alpha radiation β¯ (electron) – “heavy” charged particles – limited penetration in matter – “easy” to shield M. Silari – Radiation and radioactivity – 6 September 2016 12 Directly and indirectly ionising radiation Directly ionizing radiation: • fast charged particles (e.g., electrons, protons, alpha particles), which deliver their energy to matter directly, through many small Coulomb-force interactions along the particle’s track Indirectly ionizing radiation: • X- or g-ray photons or neutrons (i.e., uncharged particles), which first transfer their energy to charged particles in the matter through which they pass in a relatively few large interactions, or cause nuclear reactions • The resulting fast charged particles then in turn deliver the energy in matter The deposition of energy in matter by indirectly ionising radiation is a two- step process photon electron neutron proton or recoiling nuclei M. Silari – Radiation and radioactivity – 6 September 2016 13 What is radioactivity? M. Silari – Radiation and radioactivity – 6 September 2016 14 Periodic table of elements M. Silari – Radiation and radioactivity – 6 September 2016 15 The atom Nucleus: Electrons protons + neutrons M. Silari – Radiation and radioactivity – 6 September 2016 16 The three isotopes of hydrogen For example: the simplest chemical element, hydrogen, exists in three “variants” (ISOTOPES) HydrogenIdrogeno Deuteron Tritium Proton Electron Neutron M. Silari – Radiation and radioactivity – 6 September 2016 17 Chart of nuclides Unstable (=radioactive) nuclides ~ 3000 α-decay β- : n --> p+ + e- β+ : p+ --> n + e+ protons α : AX -> A-4Y + 4He2+ Stable nuclides ~250 neutrons M. Silari – Radiation and radioactivity – 6 September 2016 18 Radioactivity and ionising radiation Radioactivity: the phenomenon whereby atoms undergo spontaneous random disintegration, usually accompanied by the emission of ionising radiation The activity of a radioactive source is its rate of decay = number of disintegrations per second The unit of activity is the Bequerel 1 Bq = 1 s-1 (the old unit is the Curie: 1 Ci = 3.7 x 1010 Bq) The half-life T1/2 is the time necessary for half of the nuclei to decay Radionuclides are either of natural origin or produced by nuclear reactions (artificial radionuclides) M. Silari – Radiation and radioactivity – 6 September 2016 19 Why does ionizing radiation pose a health risk? M. Silari – Radiation and radioactivity – 6 September 2016 20 Effects of interaction of ionizing radiation with matter • Biological systems (humans in particular) are particularly susceptible to damage by ionizing radiation • The expenditure of a trivial amount of energy (~4 J/kg or Gy) to the whole body is likely to cause death… • …even if this amount of energy can only raise the gross temperature by about 0.001 °C • This is because of the ability of ionizing radiation to impart their energy to individual atoms and molecules • The resulting high local concentration of absorbed energy can kill a cell either directly or through the formation of highly reactive chemical species such as free radicals (atom or compound in which there is an unpaired electron, such as H or CH3) in the water medium that constitutes the bulk of the biological material M. Silari – Radiation and radioactivity – 6 September 2016 21 Unit The absorbed dose is the energy deposited by a given radiation in a unit mass of matter The unit of absorbed dose is the Gray: 1 Gy = 1 J/Kg (the old unit is the rad: 1 rad = 10-2 Gy) Radiation protection uses the operational quantity “dose equivalent H” in Sievert H=Q∙D 1 Sv = 1 J/Kg Q = quality factor of the radiation M. Silari – Radiation and radioactivity – 6 September 2016 22 Effects of radiation at the molecular and cellular level cell cromosome Cromatine fibre 1-10 m 1 m DNA nucleosome 30 nm 2 nm 10 nm Cells have a certain capacity (luckily) to repair damage M. Silari – Radiation and radioactivity – 6 September 2016 23 The biological effects of radiation Deterministic effects Probabilistic effects Example: burn Example: cellular mutation M. Silari – Radiation and radioactivity – 6 September 2016 24 The biological effects of radiation Stochastic effects Deterministic effects No dose threshold (linear function of Dose received in short time interval dose) dose threshold: > 100 mSv (> 500 mSv) Increase of probability by 5% per Sv for: Immediate consequences: - genetic defects - vomiting - cancer - immun deficiency - erythema and necrose Severity of the effect is independent of Health detriments are function of the the dose received dose (and dose rate) Delayed health detriments Lethal dose for humans: 5 – 7 Sv M. Silari – Radiation and radioactivity – 6 September 2016 25 The biological actions of radiation Cell membranes deterministic uncontrolled tissue indirect no-repair cell death pathologies effects (necrosis) OH free peroxydes, H O 2 radicals active substances H Hereditary effects non-lethal mis-repair mutation CANCER stochastic DNA lesions programmed cell death direct (apoptosis) effects IONISATION deterministic excitation repair normal cell survival biomolecule field physics chemistry biochemistry biology, medicine second, time scale 10-16s 10-6s 10-2s day, year, generation minute M. Silari – Radiation and radioactivity – 6 September 2016 26 Lethal dose (LD50/30) for various organisms Source: Martin Volkmer, Radioaktivität und Strahlenschutz, Informationskreis Kernenergie M. Silari – Radiation and radioactivity – 6 September 2016 27 Effects associated with whole-body exposure to radiation 0to0.25grays 0.25to1gray 1to1.25grays 2.25to5grays Above5grays No identified patho- Vomiting. Noticeable Lethal dose for 50% Some nausea. logical symptoms asso- changes to of the population. Slight fall in Almost certainly fatal. ciated with the the composition Hospitalisation leukocyte count. exposure to radiation. of the blood. essential. Radiation and man, CEA, France M. Silari – Radiation and radioactivity – 6 September 2016 28 Acute whole-body irradiation syndrome Syndrome Threshold Time to Symptoms Pathology Time to appearance death Haematopoietic 1 Gy 3 weeks Lymphocyte Depletion of 2 months depletion , bone marrow infections, bleeding Gastrointestinal 5 Gy 3 to 5 hours Diarrhoea, Destruction 2 weeks fever of the intestinal mucosa Central nervous 20 Gy 0,5 to 3 Lethargy, Inflammation 2 days system (CNS) hours convulsions of CNS, oedema LD 50 dose by acute whole body irradiation : 5 Gy M. Silari – Radiation and radioactivity – 6 September 2016 29 Relative Biological Effectiveness (RBE) The spatial distribution of radiation-matter interaction, and therefore biological damage, depends on type and energy of radiation (“track structure”) M. Silari – Radiation and radioactivity – 6 September 2016 30 Dose rate dependence Dose rate = amount of radiation absorbed per unit time Dose Dose rate 5 tubes of aspirin In 50 seconds?? Death Or in 50 years?? Small risk or 2500 mSv In 50 seconds?? Death of radiation Or in 50 years?? Small risk M. Silari – Radiation and radioactivity – 6 September 2016 31 What are the natural radiation levels? To which sources are we all exposed? (voluntarily or not) M. Silari – Radiation and radioactivity – 6 September 2016 32 Natural radiation exposures Annual exposure to natural radioactivity in France = 2.5 mSv (3.3 mSv including medical exposures) M. Silari – Radiation and radioactivity – 6 September 2016 33 Natural radiation exposures Annual exposure to natural radioactivity in Switzerland
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