Refresher Training for Users of Radiation Producing Devices

1. Refresher Training for Users of Radiation Producing Devices Elayna Mellas Radiation Safety Officer Environmental Health & Safety Manager Clarkson University Downtown Snell 155 Tel: 315-268-6640 emellas@clarkson.edu This training course has been partially adapted from slides provided by Steve Backurz, Radiation Safety Officer of The University of New Hampshire

2. Introduction • Radiation is a valuable tool used in research at Clarkson • Electron microscopes • X-ray fluorescence spectrometry • X-ray diffraction analysis of samples for chemistry and engineering research • Radioactive materials and X-ray machines are very safe if used properly and simple precautions are followed

3. The Basics: Definitions • Radioactivity: The spontaneous disintegration or decay of an unstable atom, resulting in the release of energy (radiation). • Radiation: Energy in the form of particles or waves • Radioactive material: Any material that is composed of (or contains) radioactive atoms. • Ion: Any atom or molecule with an imbalance in electrical charge. Ions are very unstable and will seek electrical neutrality by reacting with other atoms or molecules • Activity: The number of disintegrations (decays) occurring per unit of time. • Half Life: The time it takes for an amount of radioactive material to lose half (50%) of its activity because of decay.

4.  The Particles  • ALPHA PARTICLE (): A high energy particle emitted from the nucleus during the decay of an atom. • Travel a few centimeters in air • Stopped by a sheet of paper or layer of skin • Not an external hazard; ingestion or inhalation concern • BETA PARTICLE (): A high energy particle emitted from the nucleus during the decay of an atom • Travel 10 to 20 feet in air • Stopped by a book • Shielding high energy betas with lead can generate more radiation due to Bremsstrahlung x-rays • GAMMA RADIATION (): Electromagnetic radiation emitted from the nucleus during decay • No mass, no charge • Travel many feet in air 

5. Radiation Wavelength in Angstrom Units 8 6 4 2 -2 -4 -6 10 10 10 10 1 10 10 10 Radio Infrared V Ultra-Violet X-Rays Cosmic Rays i Light s i b l Photon Energy in Million Electron Volts (MeV) e Gamma Rays 4 - 10 -8 -6 -4 -2 2 2 2 10 10 10 10 10 1 10 10 The Electromagnetic Spectrum

6. Wave type of radiation - non-particulate • Photons originating from the electron cloud • Same properties as gamma rays relative to mass, charge, distance traveled, and shielding • Characteristic X-rays are generated when electrons fall from higher to lower energy electron shells • Discrete energy depending on the shell energy level of the atom • Bremsstrahlung X-rays are created when electrons or beta particles slow down in the vicinity of a nucleus • Produced in a broad spectrum of energies • Reason you shield betas with low density material X-Rays

7. Energy is lost by the incoming charged particle through a radiative mechanism Bremsstrahlung Radiation Beta Particle Bremsstrahlung Photon - + + Nucleus

8. High Voltage Power Supply Current Tungsten Filament Target Cathode Anode Glass Envelope Tube Housing X-Ray Machine Components

9. kVp - how penetrating the X-rays are • Mammography - 20 - 30 kVp • Dental - 70 - 90 kVp • Chest - 110 - 120 kVp • mA - how much radiation is produced • Time - how long the machine is on • Combination of the above determines exposure X-Ray Machine Basics

10. Ionization by a Beta particle: Ionization - ejected electron Beta Particle - - - Colliding Coulombic Fields The neutral absorber atom acquires a positive charge -

11. Gamma interactions differ from charged particle Interactions • Interactions called "cataclysmic" - infrequent but when they occur lot of energy transferred • Three possibilities: • May pass through - no interaction • May interact, lose energy & change direction (Compton effect) • May transfer all its energy & disappear (photoelectric effect) Gamma Interactions

12. An incident photon interacts with an orbital electron to produce a recoil electron and a scattered photon of energy less than the incident photon Compton Effect Before interaction After interaction Scattered Photon - - - - - - - - Electron is ejected from atom Incoming photon Collides with electron

13. Biological Effects Effects of Acute Whole Body Exposure on Man • Acute Exposure • Large Doses Received in a Short Time Period • Accidents • Nuclear War • Cancer Therapy • Short Term Effects (Acute Radiation Syndrome 150 to 350 rad Whole Body) Anorexia Nausea Erythema Fatigue Vomiting Hemorrhage Epilation Diarrhea Mortality

14. Biological Effects • Chronic Exposure • Doses Received over Long Periods • Background Radiation Exposure • Occupational Radiation Exposure • 50 rem acute vs 50 rem chronic • acute: no time for cell repair • chronic: time for cell repair • Average US will receive 20 - 30 rem lifetime • Long Term Effects • Increased Risk of Cancer • 0.07% per rem lifetime exposure • Normal Risk: 30% (cancer incidence)

15. Medical X-Rays 55.0% Radon Other 1% Internal 11% Consumer Products 3% Man-Made 18% Nuclear Medicine 4% Cosmic 8% Terrestrial 6% • Your exposure to radiation can never be zero because background radiation is always present • Natural Sources (Radon), Cosmic, Terrestrial, Medical Diagnostic, Consumer Products, etc Background Exposure Annual Dose from Background Radiation Total exposure Man-made sources 11 Total US average dose equivalent = 360 mrem/year

16. Standards for Rad Protection • Occupational Limits (Researchers) • 5 rem per year (total effective dose equivalent: TEDE) • 50 rem per year (any single organ) • 15 rem per year lens of the eye • 50 rem per year skin dose • Members of Public • 100 mrem per year • No more than 2 mrem in any one hour in unrestricted areas from external sources • Declared Pregnant Females (Occupational) • 500 mrem/term (evenly distributed) • Declaration is voluntary and must be submitted to RSO in writing (see form on website)

17. Anticipated Exposures: Less than the minimum detectable dose for film badges (10 mrem/month) - essentially zero • Average annual background exposure for U.S. population = 360 mrem/year • State and Federal Exposure Limits = 5000 mrem/year Clarkson Anticipated Worker Radiation Exposure

18. Uses of Radiation

19. Consumer Products • Building materials • Tobacco (Po-210) • Smoke detectors (Am-241) • Welding rods (Th-222) • Television (low levels of X-rays) • watches & other luminescent products (tritium or radium) • Gas lantern mantles • Fiesta ware (Ur-235) • Jewelry

20. Research at Clarkson Using Radiation Sources • Radioactive Materials (both open and sealed sources) • Gas Chromatographs (sealed sources) • Liquid Scintillation Counters (sealed sources for internal standards) • X-ray Diffraction equipment • Electron microscopes • X-ray fluorescence spectrometer

21. Diagnostic • X-rays • Nuclear Medicine (Tc-99m, Tl-201, I-123) • Positron Emission Tomography (PET) • Therapeutic • X-rays (Linear Accelerators) • Radioisotopes • Brachytherapy (Cs-137, Ir-192, Ra-226) • Teletherapy (Co-60) • Radiopharmaceuticals (I-131, Sr-89, Sm-153) Medical

22. Reducing Exposure • The goal of radiation protection is to keep radiation doses As Low As Reasonably Achievable and eliminate any unnecessary dose to yourself, coworkers, and the public • Clarkson is committed to keeping radiation exposures to all personnel ALARA • What is reasonable? • Includes: • State and cost of technology • Cost vs. benefit • Societal & socioeconomic considerations A s L ow A s R easonably A chievable

23. Practicing ALARA Protect Yourself & Your Colleagues! • Time: minimize the time that you are in contact with radioactive material to reduce exposure • Distance: keep your distance. If you double the distance the exposure rate drops by factor of 4 • Shielding: place a barrier between you and the radioactive source • Source Reduction: order and use the smallest amount of radioactive materials as necessary • Protective clothing: protects against contamination only - keeps radioactive material off skin and clothes OPTIMIZE USE OF ALL PROTECTIVE MECHANISMS TO MINIMIZE DOSE.

24. Shielding Recommendations: • Betas (ex: 32P): • Use material with low atomic number, such as: • Plastic, lucite, acrylic • Wood, paper, cardboard • Gammas (ex: 125I or 51Cr): • Use material with high atomic number, such as: • Lead, concrete, bricks, stainless steel, cast iron

25. Radiation levels decrease as the inverse square of the distance (i.e. move back by a factor of two, radiation levels drop to one fourth) • Applies to point sources (distance greater than 5 times the maximum source dimension) = 2 2 I R I R 1 1 2 2 where I = Intensity (exposure rate) at position 1 and 2 and R = distance from source for position 1 and 2 R2 I2 (mrem/hr) Source I1 (mrem/hr) R1 Position 2 Position 1 External Radiation Inverse Square Law

26. Gamma Ray Constant to determine exposure rate • (mSv/hr)/MBq at 1 meter • Hint: multiply (mSv/hr)/MBq by 3.7 to get (mrem/hr)/uCi • Exposure Rate Calculation, X (mrem/hr) at one meter: Gamma Ray Constant X = Where, A = Activity (Ci)  Gamma Ray Constant(mSv/hr)/Mbq 3.7 is the conversion factor

27. Sample Calculation • 5 Curie Cs-137 Source • Calculate Exposure Rate at 1 meter  = 1.032 E-4 mSv/hr/MBq @ 1 meter X = 1.032 E-4 * 3.7 * 5 Ci * 1000 mCi/Ci * 1000 uCi/mCi X = 1909 mrem/hour X = 1.91 rem/hour

28. Detecting Contamination Survey Meters are portable instruments that can be used to detect most spots of contamination - except for 3H. Wipe Testing must always be done for 3H and lower activities (100 µCi or less) of 35S and 14C.

29. Detecting Common Isotopes Geiger- Mueller (GM) Probe Survey Meter Sodium Iodide (NaI) Probe Liquid Scintillation Counter

30. Survey Meter Operability Each USER must verify that the survey instrument is in good working order before each use. • Check calibration date (not older than 12 months) • Batteries must be fresh / good • Background count rate • Detector/instrument must be responsive • Miscellaneous conditions…? • Check Physical Condition • Cables, Connections, Damage • Select Proper Scale • Response Time (Fast or Slow?) • Audio (On or Off)

31. A radiation detector will not detect every disintegration from a source (i.e., they are not 100% efficient) • Counts per minute (cpm) is the number of disintegrations that a detector “sees” • The efficiency of a detector is determined by the following: Efficiency = net cpm / dpm = gross cpm – background cpm / dpm CPM & DPM

32. Survey Meter “Background” Levels ! "gross" "net" Remember that background is radiation coming from the environment, and it cannot be prevented or eliminated. Each detector will have its own background level. 1st check the background level - use it as a baseline. Observed: Background: Zero: Any reading higher than the background level means the item is radioactive.

33. Regulatory Agencies • U. S. Nuclear Regulatory Commission • Regulates the nuclear industry pursuant to the Atomic Energy Act • Regulatory guides published to describe methods for complying with regulations • Agreement States • Some states have entered into an agreement with the NRC to regulate by-product material (and small quantities of source and special nuclear material) • Currently, 30 states are agreement states including New York

34. Radiation at Clarkson • Activities are licensed by the State of New York • Radiation Safety Committee has responsibility to review, approve, and oversee activities • Radiation Safety Officer (RSO) runs program • Clarkson is required to: • Train individuals that use sources of radiation • Train non-radiation workers that work in the vicinity of radiation sources • Monitor and control radiation exposures • Maintain signs, labels, postings

35. Posting & Labeling Notices • Posting • New York Notice to employees form • Caution Radiation Producing Devices or X-Rays

36. Right to report any radiation protection problem to state without repercussions • Responsibility to comply with the Radiation Protection Program and the RSO's instructions pertaining to radiation protection • Right to request inspection • in writing • grounds for notice • signed • Responsibility to cooperate with NY State inspectors during inspections and RSO during internal lab audits Employee Rights and Responsibilities

37. Inspections • Inspections • NY shall be afforded opportunity to inspect at all reasonable times • Records shall be made available • Inspector may consult with workers privately • Worker may bring matters to inspector privately • Workers can request inspection • Must be in writing • Name is not revealed

38. Internal Audits • Internal audits by Clarkson RSO are performed in all labs on campus • Looking for same things as state inspector • Security of radiation producing devices • Proper procedures in use • Postings, dosimetry, survey meters, calibrations, records of surveys, etc.

39. Report anything that looks out of the ordinary or if you are uncertain about what to do, where to go, requirements, exposures: • Call the people on the emergency list • Ask the Radiation Safety Officer (RSO) • Elayna Mellas • 268-6640 • emellas@clarkson.edu Your Role in Radiation Protection

40. Acknowledgements This training course has been adapted from slides provided by Steve Backurz, Radiation Safety Officer of The University of New Hampshire and Eric Andersen, Radiation Safety Officer at the Dana-Farber Cancer Institute.