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  • Over 20 y as a practicing health physicist in many operational areas. Approximately 13 y as the captain of the DOE Region 5 Radiological Assistance Program Team. Extensive explosives training in the Marines and in Hazmat. So these qualifications enable me to be a member of one of the elite response teams…
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  • What is radiation? Energy emissions. Here are some forms of radiation. What we are concerned about in this talk is ionizing radiation.
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  • Ionizing Radiation Alpha particles, beta particles, gamma rays and x-rays are types of ionizing radiation. When they interact with other atoms, they have enough energy to cause ionization of these atoms. Patients with radioactive material on them or inside their bodies are said to be contaminated. Contaminated patients require care in handling to effectively remove and control the contamination. Patients who have only been exposed to the radiation from a radioactive source or a machine, such as an x-ray machine or a linear accelerator, are not contaminated and do not pose any radiation contamination or exposure potential for hospital personnel. Radiation safety precautions are not needed for patients who have only been exposed and are not contaminated.
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  • Types of Ionizing Radiation Radiation is simply the emission of extra energy from a substance. That released energy can be can be in the form of particulate radiation (alpha, beta, or neutron) or energy (x-ray or gamma). Think of a hyper-active child bouncing off of the walls. Eventually, the child is worn out and goes to sleep. Radioactive decay is the process that the radioactive substance goes through to give off its extra energy to become a stable element (i.e. radium to lead). Alpha particles. Alpha particles are ejected (thrown out of) the nuclei of some very heavy radioactive atoms (atomic number > 83). An alpha particle is composed of two neutrons and two protons. Alpha particles do not penetrate the dead layer of skin and can be stopped by a thin layer of paper or clothing. If an alpha emitting radioactive material gets inside the body through inhalation, ingestion, or through a wound, the emitted alpha particles can cause ionization that results in damage to tissue. It is less likely that a patient would be contaminated with an alpha emitter. Beta particles. A beta particle is an electron ejected from the nucleus of a radioactive atom. Depending on its energy, beta radiation can travel from inches to many feet in air and is only moderately penetrating in other materials. Some beta radiation can penetrate human skin to the layer where new skin cells are produced. If high enough quantities of beta emitting contaminants are allowed to remain on the skin for a prolonged period of time, they may cause skin injury. Beta emitting contaminants may be harmful if deposited internally. Protective clothing (e.g., universal precautions) typically provides sufficient protection against most external beta radiation. Gamma rays and x-rays (photons). Gamma rays and x-rays are able to travel many feet in air and many inches in human tissue. They readily penetrate most materials and are sometimes called “penetrating” radiation. Thick layers of dense materials are needed to shield against gamma radiation. Protective clothing provides little shielding from gamma and x radiation, but will prevent contamination of the skin with the gamma emitting radioactive material. Gamma and x radiation frequently accompanies the emission of beta and alpha radiation.
  • Gamma-emitting radioactive material can be in solid form and dispersed as a powder, so it could be in a particulate form. Radioactive material can also be fumes, vapors, and aerosols.
  • You just saw the slide on radiation… it is just energy. If you were exposed to radiation, it would be like exposure to the sun’s rays. Contamination is “getting dirty” – technically speaking “crapped up!” When radioactive material is where it is not wanted (e.g., on the ground, in water, or on you), we refer to it as “contamination.”
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  • Examples of Radioactive Materials Look at the list, this is just a sample… there is a smorgasbord of radioactive stuff here and lots of applications. Just imagine what is there for the taking! Radioactive materials emit ionizing radiation. They are used in medical diagnosis (nuclear medicine), medical therapy (cancer treatment), industry (food irradiation), and for research. Many radioactive materials, including radioactive waste, are commercially shipped in special containers. A radionuclide is chemically identical to and behaves in the body the same way as the non-radioactive form of the element. For example, radioactive iodine (e.g. I-131) is concentrated in the thyroid in the same way as non-radioactive iodine(i.e. I-127). Quantities of radioactive material (i.e. activity) range from trivial amounts in typical laboratories, to much larger quantities, such as in nuclear reactors. Half-lives can range from seconds to millions of years. The nuclides that are highlighted in red are those that are considered to be potential nuclides that could be present in a radiological dispersal device.
  • Radiation Units A curie is a very large amount of radioactivity. Contamination of individuals usually involve µ Ci to mCi quantities. Nuclear medicine patients are injected with µ Ci to mCi quantities of radioactive material for routine diagnostic exams. The basic unit of radiation dose is the rad. The rad is defined as the deposition of 0.01 joule of energy (a small amount) per kilogram (kg) of tissue. A rad of x-rays, a rad of gamma rays, and a rad of beta particles are about equally damaging to tissue. However, a rad of another type of ionizing radiation, such as alpha particles or neutrons, is much more damaging to tissue than a rad of gamma rays. The rem was introduced to take into account this variation in tissue damage. This is important because a person may be exposed to more than one type of radiation. For example, it was found that 100 rad of gamma and beta radiation produced the same effect as 100 rad of x-rays. However, only 20 rad of neutrons and 5 rad of alpha particles produced the same effect as 100 rad of x-rays. Therefore, neutron and alpha radiations were more potent and required fewer rad to produce the same effect. The number of rem is calculated by multiplying the number of rad by a radiation weighting factor that accounts for the relative amount of biological damage produced by a specific type of radiation. The radiation weighting factor for x-rays, gamma rays, and beta particles is 1. Thus, a rad of one of these radiations is equal to one rem. For other types of radiation (that are less likely to be present in accidents), the quality factor may be higher. The International Scientific System (SI) assigns different units to the quantities: 1 R = 2.58 X 10 -4 C kg -1 1 gray (Gy) = 100 rad 1 sievert (Sv) = 100 rem 1 becquerel (Bq) = 1 disintegration per second
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  • Types of Radiation Hazards Patients who have only been exposed to the radiation from a radioactive source or a machine, such as an x-ray machine or a linear accelerator, are not contaminated and do not pose any radiation contamination or exposure potential for hospital personnel. Radiation safety precautions are not needed for patients who have only been exposed and are not contaminated. Patients with radioactive material on them or inside their bodies are said to be contaminated. Contaminated individuals require care in handling to effectively remove and control the contamination. Analogy - You can think of radiation exposure and radioactive material in terms of a trip to the beach. Sand is like radioactivity. The sun is like radiation exposure. Once you go inside, you are not in the sun any longer and there is no more exposure (radiation stops). On the other hand, most of the sand came off when you walked off the beach, however, some sand remains on your skin until you physically remove it (brush or wash it off). The same is true for radioactivity contamination on the skin. A small amount may remain on the skin and need to be washed off.
  • Causes of Radiation Exposure and Contamination Accidents - There are several settings or scenarios in which radiation accidents may occur: nuclear reactor accidents; medical radiation therapy accidents or errors in treatment dose; accidental overexposures from industrial irradiators; lost, stolen or misused medical or industrial radioactive sources; and accidents during the transportation of radioactive material. Terrorist Use of Nuclear Materials - The use of radioactive materials in an RDD or a nuclear weapon by a terrorist is a remote but plausible threat. The medical consequences depend on the type of device used in a terrorist event. Radiological Dispersal Device (RDD) - A radiological dispersal device (sometimes called a “dirty bomb”) is NOT an atomic bomb. Such a device is formed by combining a conventional explosive (e.g., TNT or a plastic explosive) with radioactive material that may have been stolen. The initial explosion may kill or injure those closest to the bomb, while the radioactive material remains to expose and contaminate survivors and emergency responders. Low Yield Nuclear Weapon - A low yield nuclear weapon or partial failure of a high yield weapon could cause a low yield nuclear detonation. For example, if one considers the consequences of a 0.1 kiloton yield nuclear detonation (less than 1/100 the size of the weapon used on Hiroshima), then the following would occur within one minute surrounding ground zero. The effects listed below do not take into account that multiple injuries caused by the interaction of the various types of injury will increase the probability of fatality. (NCRP Report No. 138) - The range for 50% mortality from trauma from the blast is approximately 150 yards. - The range for 50% mortality from thermal burns is approximately 220 yards. - The range for 400 rad from ionizing radiation (i.e., gamma and neutron) would be approximately 1/3 mile. - The range for 400 rad in the first hour from radioactive fallout would be almost 2 miles in the downwind direction. - As the size of the weapon increases, the effects encompass a greater distance. This will result in the release of widespread contamination and substantial air blast and heat.
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  • Radiation Doses and Dose Limits Radioactive material has always been a natural part of the earth. It has existed for millions of years in the crust of the earth, in building materials, in the food we eat, the air we breathe, and in nearly everything that surrounds us. Radiation from these materials, as well as cosmic radiation from the sun and universe, makes up the natural background radiation to which we are constantly exposed. On the average, persons are exposed to about 300 millirem per year from natural sources. The guidance from NCRP Report No. 116, Limitation of Exposure to Ionizing Radiation , states that for life saving or equivalent purposes, workers may approach or exceed 50,000 mrem to a large portion of the body. Emergency exposures are considered once-in-a-lifetime. This is below the threshold for the acute radiation syndrome. If an individual is exposed to more than 100 rem at one time, predictable signs and symptoms will develop within a few hours, days, or weeks depending on the magnitude of the dose. About half of all people exposed to a single dose of 350 rem will die within 60 days (LD 50/60 ) without medical intervention. The large doses used in medicine for radiation therapy, while higher than this dose, are given to only part of the body and are typically given over a period of weeks. The dose limits are highlighted in orange. Radiation Sickness - Acute Radiation Syndrome Radiation sickness [acute radiation syndrome (ARS)] is an acute illness following exposure to a very large dose of ionizing radiation. It is produced if a large dose of radiation reaches enough sensitive tissue within the body. The acute radiation syndrome follows a roughly predictable course over a period of time ranging from a few hours to several weeks.
  • Conference of Radiation Control Program Directors
  • Detecting and Measuring Radiation One radiation detector won’t identify all radiations. However, most radioactive materials emit more than one type of radiation. In addition, there are contamination detection equipment and exposure rate monitors. Be sure to know what your detector tells you and what it doesn’t. You cannot see, smell, taste, feel, or hear radiation, but we have very sensitive instrumentation to detect it at very low levels. Radiation monitoring instruments detect the presence of radiation. The radiation measured is usually expressed as exposure per unit time, using various units of measure, milliroentgen per hour (mR/hr) and counts per minute (CPM). Anything with “milli” in front of it is SMALL! The most commonly used instruments to detect the presence of radiation include: Geiger- Mueller Survey Meter. The Geiger-Mueller (GM) survey meter (also known as a Geiger counter) will detect low levels of gamma and most beta radiation. The instrument typically has the capability to distinguish between gamma and most beta radiation. This instrument is used to quickly determine if a person is contaminated. GM survey meters are very sensitive and other instruments may be needed to measure higher levels. Ionization Chamber Survey Meter. This device can accurately measure radiation exposure. These meters measure from low levels (mR/hr) to higher levels (many R/hr). To find the dose an individual is receiving, multiply the dose rate by the time that they are exposed. Personal Dosimeters. These devices measure the cumulative dose of radiation received by persons wearing them. Film and TLD badges must be analyzed by the company that supplies them and so the dose received is not typically known for several days. However, self reading dosimeters allow the wearer to immediately see the total dose they have received.

Part I Part I Presentation Transcript

  • Radiation Safety Principles Overview George D. Mosho, CHMM, CHS-I Health Physicist
  • Personal Introduction
    • Health Physicist – Argonne National Laboratory
      • Operational Health Physics/Radiation Safety
      • Emergency Response
      • Decontamination & Decommissioning/Site Characterization
    • Hazmat Officer (Lt.) – Will County EMA
      • Assist. Safety Officer
      • Radiation Dosimetry Officer
    • Combat Engineer Officer – USMC
      • NBC Officer
      • Explosives/Mines/Boobytraps
  • Health Physics
    • Health physics is the development, dissemination, and application of both the scientific knowledge of, and the practical means for radiation protection .
    • The objective of health physics is the protection of people and the environment from unnecessary exposure to radiation.
  • Introduction
    • Radioactive material is a hazardous material .
    • Hazardous materials are managed safely every day. ( i.e. gasoline; chlorine)
    • Radioactive materials are also safely managed daily.
  • Radiation
  • Radiation
    • Ionizing [Health Physics]
      • Alpha
      • Beta
      • Gamma
      • X-Rays
      • Neutron
    • Non-Ionizing [Industrial Hygiene]
      • microwave, radio, laser, etc.
  • Ionizing Radiation
    • Ionizing radiation is radiation capable of imparting its energy to the body and causing chemical changes
    • Ionizing radiation is emitted by
      • - Radioactive material
      • Some devices such as x-ray machines
  • Alpha Radiation
  • Beta Radiation
  • Gamma-Rays
  • X-Rays
  • Types of Ionizing Radiation Alpha Particles Stopped by a sheet of paper Beta Particles Stopped by a layer of clothing or less than an inch of a substance Gamma Rays Stopped by inches to feet of concrete or less than an inch of lead Radiation Source
  • Misconceptions
    • Don’t get hung up on the fact that alpha & beta are “particles”; x-rays and gamma are energy!
    • Radioactive material that emits alpha, beta and/or gamma can be a…
      • Solid
      • Liquid
      • Gas
  • Radiation versus Contamination
    • Radiation is a type of energy; contamination is material
    • Exposure to radiation will not contaminate you
    • Radioactive contamination emits radiation
  • Radiation and Radioactive Material
  • Contamination
  • Irradiation
  • Activation/Induced Activity
  • Examples of Radioactive Materials Physical Radionuclide Half-Life Activity Where Found Cesium-137 30 y 1.5x10 6 Ci Food Irradiator Cobalt-60 5 y 15,000 Ci Cancer Therapy Plutonium-239 24,000 y 600 Ci Nuclear Weapon Iridium-192 74 d 100 Ci Ind. Radiography Hydrogen-3 12 y 12 Ci Exit Signs Strontium-90 29 y 0.1 Ci Ocular Therapy Iodine-131 8 d 0.015 Ci Nuclear Medicine Technetium-99m 6 h 0.025 Ci Diagnostic Imaging Americium-241 432 y 0.000005 Ci Smoke Detectors Radon-222 4 d 1 pCi/l Environment
  • Radiation Units Measure of Amount of radioactive material Ionization in air Absorbed energy per mass Absorbed dose weighted by type of radiation For most types of radiation 1 R  1 rad = 1 rem Quantity Activity Exposure Absorbed Dose Dose Equivalent Unit curie (Ci) roentgen (R) rad rem
  • Radiological Units
    • Radiation Exposure (rate) Measurement:
      • Roentgen or milliroentgen (R/h or mR/h)
      • rem or millirem (mrem/h)
      • Sievert (SI unit), 1 sievert = 100 rem
  • Radiological Units
    • Activity Measurement:
      • Curie or milli or microCurie
      • Becquerel (SI unit) or MBq
      • Disintegrations per minute (dpm)
      • Counts per minute (cpm)
  • Half-Life
  • Radioactive Decay Example A x = A 0 e -0.693 t/T½ where…. A x = Current activity (23 Oct 08) A 0 = 5 microCi (Initial activity: 23 Oct 04) t = 4 y elapsed T ½ = ~ 30 y ( 137 Cs) A x = (5 microCi) e -0.693 (4 y/30 y) A x = 4.6 microCi
  • Radioactive Decay
    • A x = A 0 e -0.693 t/T½
    • where…
    • A x = Activity of the source at t = x
    • A 0 = Activity of the source at t = 0
    • t = time elapsed from t = 0 to t = x
    • T ½ = Half-life of the specific radionuclide
  • Inverse Square Law
    • I 2 = I 1 (d 1 2 /d 2 2 )
    • where…
    • I 1 = Intensity † of radiation at position #1
    • I 2 = Intensity of radiation at position #2
    • d 1 = Distance position #1 is from source
    • d 2 = Distance position #2 is from source
    † : Exposure rate (i.e. mR/h)
  • Inverse Square Law Example
    • I 2 = I 1 (d 1 2 /d 2 2 )
    • where…
    • I 1 = 120 mR/h
    • d 1 = 2 m from the source
    • d 2 = 4 m from the source
    • I 2 = (120 mR/h)((2 m) 2 /(4 m) 2 )
    • I 2 = 30 mR/h
  • Types of Radiation Hazards
    • External Exposure:
      • whole-body
      • partial-body
    • Contamination :
      • External: radioactive material on the skin
      • Internal: radioactive material inhaled, swallowed, absorbed through skin or wounds
    External Exposure Internal Contamination External Contamination
  • Causes of Exposure/Contamination
    • Accidents
      • Nuclear reactor
      • Medical radiation therapy
      • Industrial irradiator
      • Lost/stolen medical or industrial radioactive sources
      • Transportation
    • Terrorist Event
      • Radiological dispersal device (dirty bomb)
      • Low-yield nuclear weapon
  • ALARA
    • A - As
    • L - Low
    • A - As
    • R - Reasonably
    • A - Achievable
  • ALARA
    • Basic Question:
    • “ Does the benefit outweigh the risk?”
    • If not, then back to the drawing board.
    • If so, then review the operation for further potential improvements (i.e. reduction in exposure)
  • Standard Radiation Protection Principles
    • ▪ Time
    • ▪ Distance
    • ▪ Shielding
  • Radiation Protection Principles
    • Time
    • Distance
    • Source Barrier
    • Personal Barrier
    • Dispersal
    • Source Reduction
    • Effect Mitigation
    • Decorporation (Internal and surface irradiation only)
    • Optimal Technology
    • Limitation of Other Exposures
  • Natural Background Radiation
    • U.S. average: 100 - 400 mrem/y
    • [200 - 300 mrem/y due to radon]
    • Parameters:
      • mineral deposits (Brazil ~ 7 rem/y - 232 Th)
      • elevation above sea level (Denver ~ 600 mrem/y - cosmic rays)
      • other- foodstuffs, lifestyle, construction techniques for dwellings, etc.
  • Background Radiation
  • Radiation Doses and Dose Limits
    • Flight from Los Angeles to London 5 mrem
    • Annual public dose limit 100 mrem
    • Annual natural background 300 mrem
    • Annual radiation worker dose limit 5,000 mrem
    • “ Mild” acute radiation syndrome 200,000 mrem
    • LD 50/60 for humans (bone marrow dose) 350,000 mrem
  • Biological Effects
    • Potential effects on the human body from ionizing radiation:
      • No damage
      • Cells repair damage and operate normally
      • Cells are damaged and operate abnormally
      • Cells die as a result of the damage
  • Laws and Regulations
    • The Atomic Energy Act of 1954 is the basis of all laws and regulations controlling the use of radioactive materials in the US.
    • Several federal agencies, including the NRC , DOE , EPA , OSHA , and DOT have developed and promulgated radiation protection standards.
    • Organizations such as the NCRP , IAEA , ICRP and CRCPD provide recommendations for radiation exposure and the implementation of standards.
  • Personnel Dose Limits *
    • Occupational Workers:
      • TEDE ** 5 rem/yr
      • Lens of eye 15 rem/yr
      • Extremities 50 rem/yr
      • Other organs 50 rem/yr
      • Skin 50 rem/yr
    • Members of Public:
      • TEDE 0.1 rem/yr
      • * 10 CFR 20 and 10 CFR 835
      • ** Total Effective Dose Equivalent (TEDE) means the sum of the deep-dose equivalent (for external exposures) and the committed effective dose equivalent (for internal exposures).
  • Personnel Dose Limits (cont'd)
    • Minors:
      • 10% of occupational (10 CFR 20)
      • 0.1 rem/yr TEDE (10 CFR 835)
    • Embryo/Fetus:
      • 0.5 rem TEDE for the entire gestation period
  • Detecting and Measuring Radiation
    • Detectors or Survey Instruments:
      • contamination
      • exposure rate
    • Personal Dosimeters – Film, TLD, Self-reading
      • measure doses to responders
  • Questions? Thank you. If you have any questions at a later date, please contact me at Argonne National Lab George D. Mosho, CHMM 630-252-6172 [email_address]