University of Illinois at Chicago Radiation Safety Section Environmental Health and Safety Office

1. University of Illinois at ChicagoRadiation Safety SectionEnvironmental Health and Safety Office Radiation Safety Physics Lecture Physics 108, 244

2. Ionizing Radiation • Radiation that can cause ionization of the material through which it passes either directly or indirectly • Electromagnetic radiation • Particulate radiation

3. 1 _ E ~ ν~ λ Electromagnetic Radiation • Electro-magnetic waves (uncharged packets of energy) propagated through space or a material medium Wavelength, m Frequency, s-1 Energy of one photon, eV

4. Particulate Radiation • Matter that that is propagated through space or through a material medium • Alpha Particles • Beta Particles (Electrons, Positrons) • Neutrons (uncharged) • Protons • Heavy Ions • Fission Fragments

5. Sources of Ionizing Radiation • Radioactive Materials • H-3, C-14, P-32, S-35, I-125, etc. • Radiation Producing Machines • X-Ray equipment • Accelerators • Computer Tomography, C.T. • Fluoroscopy • Mammography

6. Radioactive Decay • Atoms that have a neutron to proton ratio that is too high or too low undergo the process of radioactive decay • Radioactive decay is the spontaneous emission of matter and/or energy from the nucleus of the atom • Particles: Alpha and/or Beta Particles • Energy: Gamma Rays and X-Rays • As a result of radioactive decay the atom transforms into a different element, which can be either stable or also radioactive

7. Nature of Radioactive Decay • Decay is random, predicting when a given atom will decay is impossible • In sufficient numbers, the probability of decay becomes well defined • Decay Constant (λ) = The probability that any one atom will decay

8. Activity • Activity is the rate at which nuclear transformations occur in a radioactive material (rate of decay): A= λN • Number of radioactive atoms and, as a result, activity decreases exponentially with time: N = N0exp(-λt) A = A0exp(-λt)

9. Half-Life Time required for a radioactive substance to lose 50% of its activity by radioactive decay • ½ the activity • ½ the number of radioactive atoms • ½ the radiation intensity ln2 T1/2 = λ 1/2 1/4 1/8 T1/2 T1/2 T1/2

10. Units of Activity • Modern SI Unit • Becquerel (Bq) • 1 Bq = 1 decay per second • Traditional Unit • Curie (Ci) • The number of radioactive decays occurring in one gram of pure Ra-226 1 Ci = 3.7 x 1010 Bq = 37 GBq

11. Modes of Radioactive Decay • Alpha Decay • Lowers the n/p ratio • Usually occurs when atomic number is > 83 • Beta Decay (- or +) • Negative Betas (Negatrons) - Lowers the n/p ratio • Positive Betas (Positrons) - Raises the n/p ratio • Electron Capture • Raises the n/p ratio

12. Beta Decay • A neutron transforms into a proton, an electron, and an anti-neutrino H-3 He-3

13. Gamma Emission • After decay, some nuclei (called isomers) are left in an excited state (extra energy) • Excitation energy may be emitted as a gamma ray

14. Gamma Decay (Cs-137) Beta 661 keV Gamma Cs-137 T1/2 30 yr Ba-137m T1/2 2.55 min Ba-137 STABLE

15. Tl-204 Decay Tl-204 (T1/2 3.779 yr) 97.4% 2.6% Pb-204 Hg-204

18. Absorbed Dose • ABSORBED DOSE - The amount of energy imparted per unit mass at a given location within irradiated material • RAD (rad) - The traditional unit of dose, defined as the absorption of 100 ergs per gram (0.01 J / kg or 0.01 Gy) • GRAY (Gy) – The SI unit of dose, defined as the absorption of 1 joule per kilogram (100 rads) 1 Gy = 100 rad

19. Exposure • A measurement of the amount of ionization created by X-rays or gamma rays in a volume of air • Roentgen = 2.58 × 10-4 Coulombs / kg air • Exposure to 1 R delivers a dose of 0.96 rad to tissue

20. Biological Effectiveness • Equivalent Dose – A quantity that expresses the biological effect of exposure to the different types of radiation. • Radiation weighting factor (wR) - estimate of the effectiveness per unit dose of the given radiation relative a to low-LET standard (X-ray or gamma) Equivalent Dose = Absorbed Dose×wR

21. Equivalent Dose • REM (rem) - The traditional unit of dose of any radiation which produces the same biological effect as a 1 rad of absorbed dose of x- or gamma-rays • Sievert (Sv) – The SI unit of dose of any radiation that produces the same biological effect as a 1Gy of absorbed dose of x- or gamma-rays 1 Sv = 100 rem

22. Radiation weighting factors

23. Stochastic Effects • Cancer • Radiation is a weak carcinogen • Genetic • Magnitude thought to be very small

24. Stochastic Risks • The PROBABILITY that an effect occurs is related to the magnitude of the radiation dose • No relation between magnitude and severity of the effect – all or none response for an individual • Same effect can be seen in unexposed individuals

25. Radiation Risk Estimates International Commission on Radiological Protection (ICRP) Publication 103 (2007) Nominal Risk for Stochastic Effects After Exposure to 1 Sv at Low Dose Rates: For acute exposures a factor of 2 is used for risk estimates U.S. Cancer death rate: 21.20% (40.6% total) With exposure to 5 rem: 21.48%

26. 5,000,000 TYPICAL RADIATION THERAPY: 5,000 cGy = 5,000,000 mrem TO SINGLE ORGAN (delivered in series of exposures) Radiation Levels (mrem/year)

27. 5,000,000 500,000 LETHAL DOSE TO 50% OF HUMANS TYPICAL THERAPY X-RAY TO SINGLE ORGAN (series of exposures) 400,000 Radiation Levels (mrem/year)

28. 5,000,000 500,000 50,000 LETHAL DOSE TO 50% OF HUMANS TYPICAL THERAPY X-RAY TO SINGLE ORGAN (series of exposures) SMOKING 30 CIGARETTES PER DAY: 16,000 mrem/year 400,000 FIRST DETECTABLE PHYSIO-LOGICAL EFFECTS 25,000 16,000 SMOKING 30 CIGARETTES PER DAY Radiation Levels (mrem/year)

29. TOTAL AVERAGE ANNUAL RADIATION DOSE TO THE US RESIDENT: 620 mrem 5,000,000 50,000 500,000 5,000 LETHAL DOSE TO 50% OF HUMANS TYPICAL THERAPY X-RAY TO SINGLE ORGAN (series of exposures) MAXIMUM ALLOWED ANNUAL DOSE TO WORKER 400,000 FIRST DETECTABLE PHYSIO-LOGICAL EFFECTS 25,000 16,000 SMOKING 30 CIGARETTES PER DAY Radiation Levels (mrem/year)

30. Natural Background: Occupational: 110 mrem (1.1 mSv) 5,000,000 50,000 500,000 5,000 500 311 mrem (3.11 mSv) AVERAGE ANNUAL RADIATION EXPOSURE TO U.S. RESIDENT LETHAL DOSE TO 50% OF HUMANS TYPICAL THERAPY X-RAY TO SINGLE ORGAN (series of exposures) MAXIMUM ALLOWED ANNUAL DOSE TO WORKER Education, Research 70 Medical 80 EPA Map of Radon Zones Medical Exposures: 300 mrem (3.0 mSv) Cosmic 11.00% Government, Military 60 Industry 80 400,000 AVIATION 310 620 Absorbed Gamma Dose Rate in Air Terrestrial 300 FIRST DETECTABLE PHYSIO-LOGICAL EFFECTS AVERAGE NATURAL BACKGRD Nuclear Medicine 26% 7.00% MEDICAL Radon-222 311 Radon-220 Interventional Fluoroscopy 14% 223 X-RAY DIAGNOSTICS 68% 5.00% Aviation 310 25,000 Nuclear Power 190 RADON Potassium-40 200 CT 49% 5.00% 190 Conventional Radiography and Fluoroscopy 11% NUCLEAR POWER Th & U Series 16,000 CT 147 4.00% SMOKING 30 CIGARETTES PER DAY Other <0.01% NCRP Report 160, 2009 OCCU- PATIONAL 110 NCRP Report No.160, 2009 NCRP Report 160, 2009 77 NUCLEAR MEDICINE J.S.Duval et al, 2005, Terrestrial radioactivity and gamma-ray exposure in the US and Canada: U.S.G.S. Open-File Report 2005-1413 Radiation Levels (mrem/year) 28 mrem

31. Natural Radionuclides Contained In The Body: 29 mrem (0.29 mSv) Cosmic Radiation: 33 mrem (0.33 mSv) Consumer Products: 13 mrem (0.13 mSv) Terrestrial Radiation: 28 mrem (0.28 mSv) Terrestrial Radiation: 28 mrem (0.28 mSv) 5,000,000 50,000 500,000 5,000 50 LETHAL DOSE TO 50% OF HUMANS Po-210 Rb-87 TYPICAL THERAPY X-RAY TO SINGLE ORGAN (series of exposures) MAXIMUM ALLOWED ANNUAL DOSE TO WORKER 26% Commercial Air Travel INTERNAL R/N 29 6% Mining and Agriculture K-40 Th-232 400,000 AVIATION 310 COSMIC 300 2% Fossil Fuels FIRST DETECTABLE PHYSIO-LOGICAL EFFECTS AVERAGE NATURAL BACKGRD 33 27% Building Materials 0.6% Road Construction MEDICAL Ra-228 Th-230 <0.03% Glass & Ceramics TERRESTRIAL 311 21 223 X-RAY DIAGNOSTICS 3% Other 25,000 RADON 35% Tobacco 200 U-238 Rn-222 190 NUCLEAR POWER 16,000 J.S.Duval et al, 2005, Terrestrial radioactivity and gamma-ray exposure in the US and Canada: U.S.G.S. Open-File Report 2005-1413 CT 147 SMOKING 30 CIGARETTES PER DAY NCRP Report 160, 2009 C-14 Ra-224 OCCU- PATIONAL 110 J.S.Duval et al, 2005, Terrestrial radioactivity and gamma-ray exposure in the US and Canada: U.S.G.S. Open-File Report 2005-1413 77 NUCLEAR MEDICINE Radiation Levels (mrem/year) 500

32. 5,000,000 50,000 500,000 5,000 5 NATURAL GAS: 2 (especially residential use) LETHAL DOSE TO 50% OF HUMANS TYPICAL THERAPY X-RAY TO SINGLE ORGAN (series of exposures) MAXIMUM ALLOWED ANNUAL DOSE TO WORKER INTERNAL RN AVERAGE UIC OCCUPATIONAL EXPOSURE (751 monitored) 29 400,000 AVIATION 310 COSMIC 34 300 FIRST DETECTABLE PHYSIO-LOGICAL EFFECTS AVERAGE NATURAL BACKGRD 33 MEDICAL TERRESTRIAL 311 21 223 X-RAY DIAGNOSTICS NATURAL GAS (especially residential) 25,000 FALLOUT FROM WEAPONS TESTING: 0.75 RADON 2 200 190 NUCLEAR POWER 16,000 CT 147 SMOKING 30 CIGARETTES PER DAY CONSUMER PRODUCTS Average UIC occupational exposure (751 monitored) 34 mrem OCCU- PATIONAL 110 WEAPONS FALLOUT 13 0.75 SLEEPING WITH ANOTHER HUMAN 77 NUCLEAR MEDICINE 0.1 Radiation Levels (mrem/year) 500 50

33. Exposure Rate ConstantHow to calculate your radiation dose if you know the isotope, the activity & the distance.

34. • • • X X X Exposure Rate CalculationFrom a 10μCi Cs-137 Point Source at 1 cm (3.287 is the Exposure Rate Constant for Cs-137)

35. Exposure Rate at Various Distances From 10μci of Cs-137 • 0.1 cm 3287 mR/h • 1.0 cm 32.87 mR/h • 10 cm 0.3287 mR/h • 100 cm 0.003287 mR/h

36. 5,000,000 50,000 500,000 5,000 5 LETHAL DOSE TO 50% OF HUMANS TYPICAL THERAPY X-RAY TO SINGLE ORGAN (series of exposures) MAXIMUM ALLOWED ANNUAL DOSE TO WORKER INTERNAL RN AVERAGE UIC OCCUPATIONAL EXPOSURE (751 monitored) 29 400,000 AVIATION 310 COSMIC 34 300 FIRST DETECTABLE PHYSIO-LOGICAL EFFECTS AVERAGE NATURAL BACKGRD 33 MEDICAL TERRESTRIAL 311 21 223 X-RAY DIAGNOSTICS NATURAL GAS (especially residential) 25,000 RADON 2 10 hours of Physics Lab using 10 µCi Cs-137 source: 0.03 200 190 NUCLEAR POWER 16,000 CT 147 SMOKING 30 CIGARETTES PER DAY CONSUMER PRODUCTS OCCU- PATIONAL 110 WEAPONS FALLOUT 13 0.75 CONSUMER PRODUCTS: 0.03 (without building materials and tobacco) SLEEPING WITH ANOTHER HUMAN 77 NUCLEAR MEDICINE 0.1 Radiation Levels (mrem/year) 500 50

37. ALARA Policy • As • Low • As • Reasonably • Achievable

38. Standard Warning SignFor Radioactive Material Use Areas • Used to indicate an area is authorized for radioactive material use – BUT only by projects that have it listed in their authorization!

39. Lab Entrance Labeling LOW MEDIUM HIGH

40. Basic Principles of Radiation Protection • Time • Distance • Shielding • Contamination Control

41. Time • Radiation dose is directly proportional to the time of exposure

42. I2 d12 = I1 d22 Distance • Inverse Square Law Radiation intensity is inversely proportional to the distance squared I1 I2 d1 d2

43. Shielding

44. Rules for Handling Sources • DO NOT place your finger or any other part of your body directly over the face of the source • Handle the sources only by their edges • Minimize the time sources are handled • Increase distance to minimize exposure • Sign sources in and out with the T.A.

45. Lab Coats • You will be working with Sealed Sources only. • Lab coats and gloves are to be worn in the lab when handling UNSEALED radioactive material. • When working with SEALED radioactive sources, lab coats and gloves are NOT required.