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Radiation Protection Course Radiation Protection Service.

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Presentation on theme: "Radiation Protection Course Radiation Protection Service."— Presentation transcript:

1 Radiation Protection Course Radiation Protection Service

2 Radiation Protection Course Background Physics Michael Watt

3 Contents Atomic Structure Types of Radiation Attenuation & Shielding Activity & Half Life

4 Nucleus Electrons -ve charge Atomic Structure 1

5 Atomic Structure 2 Proton +ve

6 Neutrons Atomic Structure 3

7 Carbon 12 C 12 6 Atomic Number - No. protons Atomic Mass - no. protons and neutrons

8 Carbon 12

9 Definition of Isotope Atom protons fixed – number of neutrons can vary to form different isotopes. Example carbon has 2 stable isotopes 12 6 C, 13 6 C To be stable number of N and P must be about equal

10 Stability Curve p=n No..of Protons No. of Neutrons

11 Definition of Radioactive Isotope This occurs when the ratio of Neutrons to protons is too great or too small, and the atom spontaneously attempts to become stable Example carbon has five radioactive isotopes C-10, C-11, C-14, C-15, C-16

12 Carbon 14 C 14 6 Atomic Number - No. protons Atomic Mass - no. protons and neutrons

13 Ion An atom or molecule which has lost or gained one or more electrons An ion will have a positive or negative electrical charge

14 Ionisation

15 Types of ionising radiation -VE or +VE Alpha (2n+2p) Smoke detectors Beta (electron or positron) Biological work Gamma & X-ray (electromagnetic radiation) Some biological work (I-125) and Medical imaging

16 Sources of Ionising Radiation Alpha Americium 241 (& γ) Radon 222 Polonium 210 Beta Tritium (Hydrogen-3) Carbon-14 Sulphur-35 Phosphorus-32/33 Gamma Iodine-125 Cobalt-60 (& β) Fluorine-18

17 X-Rays Produced by accelerating electrons from a cathode onto an anode inside an evacuated glass tube. Less than 1 % of energy converted to x- rays, rest to heat. X-rays have the same physical properties as gamma photons.

18 Attenuation paper perspex lead

19 Energy of Ionising radiation The energy of Alpha, Beta and Gamma radiations is measured in ELECTRON VOLTS eV, normally keV and MeV 1eV = 1.6 x J Higher energy = more penetrating (for a given type of radiation)

20 Alpha Americium 241 (& γ)5.4 MeV Beta Tritium (Hydrogen-3) Carbon-14 Sulphur-35 Phosphorus-32 Phosphorus keV 157 keV 167 keV 1710 keV 250 keV Gamma Iodine-125 Cobalt-60 Fluorine keV 1.17 MeV & 1.33 MeV

21 Shielding Materials Alpha particles – Paper, dead layer of skin Beta particles – 1 cm perspex or tissue Gamma Photons – dense material such as lead or DU

22 Activity New Unit Becquerel 1 disintegration per second. Old Unit Curie Based on number of disintegrations from 1 g of radium x dps.

23 Specific Activity Measure of the activity per unit mass or volume Bq/g or Bq/ml

24 Half Life ( T 1/2 ) 1 half life Time

25 Half Life Fluorine min Phosphorus d Phosphorus d Iodine d Sulphur d Cobalt y Tritium (Hydrogen-3)12.3 y Carbon y

26 Radiation Dose Gray (Gy) – absorbed dose. Defined as 1 Joule of energy absorbed per kilogramme of material. Sievert (Sv)– Unit of equivalent dose and effective dose 100 rad = 1 Gray ( 100 rem = 1 Sv) 1mrad = 10 µGray ( 1 mrem = 10 µSv)

27 Next… Short video: –Working Safely with Radioactivity


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