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Health physics
- 2. 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. 2
- 3. 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. 3
- 4. Radiation 4
- 6. Radiation and Radioactivity Radiation = emission and propagation of energy through space or through a material in the form of waves or, by extension, corpuscular emissions Radioactivity = spontaneous emission of radiation from the nucleus of an unstable atom 6
- 7. Electromagnetic Spectrum of Radiation Non-ionizing radiation = does not contain sufficient energy to produce ions Ionizing Radiation = particles or photons with sufficient energy to produce ions in the medium 7
- 8. Radiation Ionizing [Health Physics] Alpha Beta Gamma X-Rays Neutron Non-Ionizing [Industrial Hygiene] microwave, radio, laser, etc. 8
- 9. 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 9
- 10. X-Rays 10
- 11. Types of Ionizing Radiation Alpha Particles Stopped by a sheet of paper Radiation Source 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 11
- 12. Properties of α, β, γ 12
- 13. Radiation versus Contamination Radiation is a type of energy; contamination is material Exposure to radiation will not contaminate you Radioactive contamination emits radiation 13
- 14. Radiation and Radioactive Material 14
- 15. Contamination 15
- 16. Irradiation 16
- 18. Examples of Radioactive Materials Physical Radionuclide Half-Life Activity Where Found Cesium-137 30 y 1.5x106 Ci Food Irradiator Cobalt-60 5y 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 Technetium-99m 8d 6h Americium-241 432 y Radon-222 4d 0.015 Ci 0.025 Ci 0.000005 Ci 1 pCi/l Nuclear Medicine Diagnostic Imaging Smoke Detectors Environment 18
- 19. Personnel Dose Limits* Occupational Workers: TEDE Lens of eye Extremities Skin Other organs 5 rem/yr 15 rem/yr 50 rem/yr 50 rem/yr 50 rem/yr 20
- 20. Annual Exposure Limits rem mrem Whole-Body 5 5,000 Eye 15 15,000 Shallow 50 50,000 10 % 10 % Minors & Declared Pregnant Workers* Whole Body = Total Effective Dose Equivalent General Public Limit = 2 mrem / hr or 0.1 rem / yr 21
- 21. Radiological Units Radiation Exposure (rate) Measurement: Roentgen or milliroentgen mR/h) (R/h or rem or millirem (mrem/h) Sievert (SI unit), 1 sievert = 100 rem 22
- 22. Radiological Units Activity Measurement: Curie or milli or microCurie Becquerel (SI unit) or MBq Disintegrations per minute (dpm) Counts per minute (cpm) 23
- 23. Half-Life 24
- 24. Types of Radiation Hazards Internal Contamination External Exposure: whole-body partial-body External Contamination External Exposure Contamination: External: radioactive material on the skin Internal: radioactive material inhaled, swallowed, absorbed through skin or wounds 25
- 25. RADIATION AND PREGNANCY Time dependence first 2 weeks of pregnancy-resorption and termination of pregnancy 2nd week to 10th week period of major organogenesis=possible congenital abnormalities 2nd and 3rd trimesters, responses above are unlikely. Malignant disease during childhood a likely response. This also possible with exposure in 1st trimester Responses likely only with high rad doses (above 25 rad) 26
- 27. ALARA A - As L - Low A - As R - Reasonably A - Achievable 28
- 28. Recognition of Radiation Sources Labeling Certain exemptions Radiation detection 29
- 31. 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 32
- 32. Detecting and Measuring Radiation Detectors or Survey Instruments: contamination exposure rate Personal Dosimeters – Film, TLD, Self-reading measure doses to responders 33
Hinweis der Redaktion
- Health Physics Society
- What is radiation? Energy emissions. Here are some forms of radiation. What we are concerned about in this talk is ionizing radiation.
- 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.
- 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.
- 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.”
- 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 µCi to mCi quantities. Nuclear medicine patients are injected with µCi 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-11 gray (Gy) = 100 rad 1 sievert (Sv) = 100 rem1 becquerel (Bq) = 1 disintegration per second
- 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.
- 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.