Radiation Basics Definitions
What is Radiation?
In our daily life, we are exposed to various types of naturally occurring radiation from cosmic rays, from radioactive substances in the earth, and from naturally occurring radiation in our bodies. This is commonly referred to as background radiation. The combined annual dose from these sources is thought to range from 0.001 to 0.003 sievert (or from 1 to 3 millisievert [mSv]).
In addition, the same level of radiation is thought to be received annually from radon, but the amount varies considerably depending on the geographic area and the type of building.
The radiation dose from chest radiography is a fraction of the annual naturally occurring background radiation dose, and the dose from fluoroscopy of the stomach is, at most, 0.05 Sv on the skin of the back. On average as an example, the annual radiation doses received per capita in the United States from naturally occurring and manmade sources of radioactivity is approximately 0.0036 Sv (3.6 mSv).
References about this subject: The Radiation Effects Research Foundation
Ionizing radiation is radiation that changes the structure of individual atoms by ionizing them. The ions produced in turn ionize more atoms.
Substances that produce ionizing radiation are called radioactive.
Radioactivity is a natural phenomenon. Nuclear reactions take place continuously on the sun and all other stars. The emitted radiation travels through space, and a small fraction reaches the Earth. Natural sources of ionizing radiation also exist in people and in the ground. The most common of these are uranium and its decay products.
Ionizing radiation is categorized into the following types:
- Alpha radiation
An alpha particle consists of two protons and two neutrons (namely, a nucleus of helium).
Alpha rays are produced following spontaneous decay of certain radioactive atoms, such as radium, plutonium, uranium, and radon. Because of its large mass and positive charge, an alpha ray can usually pass only a short distance–less than 1 mm–in water or no more than 1 to 3 inches in air before stopping, and can be stopped by a piece of paper. Therefore, health effects of alpha-ray exposures appear only when alpha-emitting materials are ingested (i.e., internal exposure).
- Beta radiation
A beta particle consists of a fast electron emitted from an atom. Its mass is nearly 1/2000 of the mass of a proton or neutron. It has more mass and less energy than a gamma ray, so it doesn’t penetrate matter as deeply as gamma and X-rays.
Beta rays are produced following spontaneous decay of certain radioactive materials, such as tritium (an isotope of hydrogen), carbon-14, phosphorus-32, and strontium-90. Depending on its energy (i.e., speed), a beta ray can traverse different distances in water–less than 1 mm for tritium to nearly 1 cm for phosphorus-32. As with alpha rays, the major concern for health effects is after their ingestion (i.e., internal exposure).
- Gamma rays
An electromagnetic wave, a gamma ray is similar to ordinary visible light but differs in energy or wavelength. Sunlight consists of a mixture of electromagnetic rays of various wavelengths, from the longest, infrared, through red, orange, yellow, green, blue, indigo, and violet, to the shortest in wavelength, ultraviolet. A gamma ray’s wavelength is far shorter than ultraviolet (i.e., it is far higher in energy).
They are almost identical to X-rays. Gamma rays generally have a shorter wavelength than X-rays. Gamma rays are very penetrating; thick lead shielding is generally required to stop them.
Gamma rays are produced following spontaneous decay of radioactive materials, such as cobalt-60 and cesium-137. A cobalt-60 gamma ray can penetrate deeply into the human body, so it has been widely used for cancer radiotherapy.
They are manmade radiation produced by bombarding a metallic target with electrons at a high speed in a vacuum.
X-rays are electromagnetic radiation of the same nature as light waves and radio waves, but at extremely short wavelength, less than 0.1 billionth of a centimeter. They are also called photons. The energy of X-rays is millions of times greater than that of light and radio waves. Because of this high energy level, X-rays penetrate a variety of materials, including body tissue.
X rays have the same characteristics as gamma rays, although they are produced differently. When high-speed electrons hit metals, electrons are stopped and release energy in the form of an electromagnetic wave. This was first observed by Wilhelm Roentgen in 1895, who considered it a mysterious ray, and thus called it an X ray.
X rays consist of a mixture of different wavelengths, whereas gamma-ray energy has a fixed value (or two) characteristic to the radioactive material.
Neutron particles are released following nuclear fission (splitting of an atomic nucleus producing large amounts of energy) of uranium or plutonium. In fact, it is neutrons that trigger the nuclear chain reaction to explode an atomic bomb.
The human body contains a large amount of hydrogen (a constituent of water molecules that occupy 70% of the human body), and when neutrons hit the nucleus of hydrogen, i.e., a proton that is positively charged, the proton causes ionizations in the body, leading to various types of damage. At equivalent absorbed doses, neutrons can cause more severe damage to the body than gamma rays. Neutrons hardly damage cells because they do not carry any electrical charge.
X rays and gamma rays are short wavelength
electromagnetic waves (with properties equivalent to light).
All the below waves are electromagnetic waves and related to light.
Electromagnetic waves (radiation) = flow of energy transmitted through space (Sohei Kondo)
Radiation and Radioactivity
|Radioactivity and radiation are different.|
Model of decay of a 60Co atomic nucleus
When an atom emits an alpha or beta particle or a gamma ray, it becomes a different type of atom. Radioactive substances may go through several stages of decay before they change into a stable, or non-ionizing, form. For example; U-238 has 14 different stages of decay before it stabilises.
– Isotope – Radioisotope – Radionuclide
An element may have several forms, or isotopes. A radioactive isotope of an element may be called “radioisotope”. However, the more correct term is radionuclide.
Each radionuclide has a characteristic half-life, which is the time required for half of a quantity of the material to decay.
Common Conversions and Prefixes
Represented by “R”, is the unit of measurement that indicates the charge produced in air by x or gamma rays, whereas SI Units are n terms of coulombs per kilogram of air (C kg-1).
1R = 2.58 X 10-4 C kg-1
Radiation Absorbed Dose and KERMA (Kinetic Energy Released in Material)
100 rad = 1 gray (Gy)
0.01 Gy = 1 rad
Radiation Dose Equivalent
100 rem = 1 sievert (Sv
0.01 Sv = 1 rem
1 µSv = 0.1 mrem
1 disintigration per second = 1 becquerel (Bq)
2.7 X 10-11 curie (Ci) = 1 Bq
1 µCi = 37 kBq
1 mCi = 37 MBq
1 Bq = 27 pCi
370 MBq = 10 mCi
SI Unit Prefixes
10-3 milli m
10-6 micro µ
10-9 nano n
10-12 pico p
103 kilo k
106 mega M
109 giga G
1012 tera T
Commonly used Isotopes
Common Use of the Isotopes (Radioisotopes)
Used in many smoke detectors for homes and businesses to measure levels of toxic lead in dried paint samples, to ensure uniform thickness in rolling processes like steel and paper production, and to help
determine where oil wells should be drilled.
Used to analyze metal alloys for checking stock and sorting scrap.
Aid to biomedical researchers studying the cell function and bone formation of mammals.
Used to measure the mineral content of coal ash and to measure the moisture of materials stored in silos.
Used in research to ensure that potential new drugs are metabolized without forming harmful by-products.
Used to treat cancers; to calibrate the equipment used to measure correct patient dosages of radioactive pharmaceuticals; to measure and control the liquid flow in oil pipelines; to tell researchers whether oil wells are plugged by sand; and to ensure the right fill level for packages of food, drugs and other products. (The products in these packages do not become radioactive.)
Used in research in red blood cell survival studies.
Used in nuclear medicine to help physicians interpret diagnostic scans of patients’ organs, and to diagnose pernicious anemia.
Used to sterilize surgical instruments; to improve the safety and reliability of industrial fuel oil burners; and to preserve poultry, fruits and spices.
When injected with monoclonal antibodies into a cancer patient, helps the antibodies bind to and destroy the tumor.
Used in mining to analyze material excavated from pits and slurries from drilling operations.
Widely used to diagnose thyroid disorders.
Used to check some radioactivity counters in in vitro diagnostic testing laboratories.
Used to diagnose and treat thyroid disorders. (Former President George H.W. Bush and Mrs. Bush were both successfully treated for Graves’ disease, a thyroid disease, with radioactive iodine.)
Used to test the integrity of pipeline welds, boilers and aircraft parts.
Used in indicator lights in appliances like clothes washers and dryers, stereos and coffeemakers; to gauge the thickness of thin plastics, sheet metal, rubber, textiles and paper; and to measure dust and pollutant levels.
Used to detect explosives and as voltage regulators and current surge protectors in electronic devices.
Used in molecular biology and genetics research.
Has safely powered at least 20 NASA spacecraft since 1972.
Used in electric blanket thermostats and to gauge the thickness of thin plastics, thin sheet metal, rubber, textiles and paper.
Used in protein studies in life science research.
Used to locate leaks in industrial pipelines and in oil well studies.
Used to study bone formation and metabolism.
Used in survey meters by schools, the military and emergency management authorities.
The most widely used radioactive isotope for diagnostic studies in nuclear medicine. Different chemical forms are used for brain, bone, liver, spleen and kidney imaging and also for blood flow studies.
Measures the dust and pollutant levels on filter paper and gauges the thickness of plastics, sheet metal, rubber, textiles and paper.
Used in electric arc welding rods in the construction, aircraft, petro- chemical and food processing equipment industries. It produces easier starting, greater arc stability and less metal contamination.
Prolongs the life of fluorescent lights.
Provides coloring and fluorescence in colored glazes and glassware.
Used for life science and drug metabolism studies to ensure the safety of potential new drugs; for self-luminous aircraft and commercial exit signs; for luminous dials, gauges and wristwatches; and to produce luminous paint.
(information and links related to radiation, for the general public and the scientific community)