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Louisiana State University Radiation Safety Office

This module from Louisiana State University's Radiation Safety Office provides an overview of ionizing radiation, including its types, properties, and dose equivalents. Learn about alpha particles, beta particles, neutrons, photons, and more.

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Louisiana State University Radiation Safety Office

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  1. Louisiana State UniversityRadiation Safety Office Module 2 Fundamentals of Ionizing Radiation

  2. What is Radiation? The transfer of energy from one object to another through space.

  3. Beta Particle Alpha Particle Neutron Photon Types of Radiation Particulate vs. Electromagnetic

  4. Ionizing Non-ionizing Visible Light X-Rays & Gamma Rays Ultra - Violet Micro - waves Electric waves Infrared Radio waves 10-12 10-10 10-8 10-6 10-4 10-2 100 102 104 106 108 1010 Wavelength (cm) Electromagnetic Radiation Oscillating electric and magnetic fields that transfer energy to matter via photon or wave interactions

  5. Charged vs. Uncharged Beta Particle Alpha Particle Neutron Photon Types of Radiation

  6. Ionizingvs. Has enough energy to completely remove an electron from an atom Non-Ionizing Not enough energy to completely remove an electron from an atom Types of Radiation

  7. Pair Production • A photon of at least 1.022 MeV energy may spontaneously form a positron-electron pair • The positron and electron interact with matter as energetic charged particles • The positron will eventually combine with an electron and produce two 511 keV photons

  8. Exposure • The sum of the charges of one sign produced by photons in a given mass of air • The SI unit of exposure is the coulomb/kilogram (C/kg) • The traditional unit is the roentgen (R) • 1 R = 2.58 x 10-4 C/kg • This unit is only defined for photons of less than 3 MeV energy in air • Symbol is X

  9. Absorbed Dose • The energy deposited in or absorbed by an object per unit mass • Applies to all radiation at all energies in all absorbers. • The SI unit of absorbed dose is the Gray (Gy) • The traditional unit is the rad • 100 rad = 1 Gy = 1 J/kg • Symbol is D

  10. Dose Equivalent • The energy deposited in an object per unit mass multiplied by a “quality factor” (quality factor accounts for the different biological effectiveness of different types of radiation) • The SI unit of dose equivalent is the sievert (Sv) • The traditional unit is the rem • 100 rem = 1 Sv • Symbol is H, H = D * Q

  11. Recommended Quality Factors(from the NRC - Nuclear Regulatory Commission) RADIATION TYPEQF X-rays and Gammas 1 Beta (except H-3) 1 H-3 1 Thermal Neutrons * Fast Neutrons * Unknown Neutrons 10 Alpha 20 * See 10 CFR Table 1004(b).2 (CFR = Code of Federal Regulations)

  12. Conversions • For purpose of radiation protection, it is assumed that 1R = 1rad = 1rem • R is only defined for photons • The quality factor is 1 for photons • The actual “conversion” factor is dependent on the absorber • 1R is actually less than 1rad (1R = 0.96 rad for tissue)

  13. Other Dose Equivalents • Deep Dose Equivalent (Hd) – The dose equivalent at a tissue depth of 1 cm due to external radiation • Eye Dose Equivalent (Heye) – The dose equivalent at a tissue depth of 0.3 cm due to external radiation • Shallow Dose Equivalent (H5) – The dose equivalent at a tissue depth of 0.007 cm due to external radiation

  14. Other Dose Equivalents * • Committed Dose Equivalent (HT50) – The dose equivalent received by a tissue (T) over the next 50 years due to an intake of radioactive material • Committed Effective Dose Equivalent (CEDE or HE50) – The sum of the products of the committed dose equivalent to a tissue and a weighting factor for that tissue, HE50 = Sw T HT50

  15. Other Dose Equivalents* • Effective Dose Equivalent (HE) – The sum of the products of the dose equivalent to a tissue and a weighting factor (wT) for that tissue, HE = SwTHT • Total Effective Dose Equivalent (TEDE) – the sum of the deep dose equivalent and the CEDE, TEDE = Hd + HE50

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