Dosimeter
Encyclopedia
exposure to something in the environment — particularly to a hazard inflicting cumulative impact over long periods of time
Time
Time is a part of the measuring system used to sequence events, to compare the durations of events and the intervals between them, and to quantify rates of change such as the motions of objects....
, or over a lifetime. This article concentrates on the radiation dosimeter, which measures exposure to ionizing radiation
Ionizing radiation
Ionizing radiation is radiation composed of particles that individually have sufficient energy to remove an electron from an atom or molecule. This ionization produces free radicals, which are atoms or molecules containing unpaired electrons...
, but other dosimeters also exist, such as sound dosimeters, ultraviolet
Ultraviolet
Ultraviolet light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than X-rays, in the range 10 nm to 400 nm, and energies from 3 eV to 124 eV...
dosimeters, and electromagnetic field
Electromagnetic field
An electromagnetic field is a physical field produced by moving electrically charged objects. It affects the behavior of charged objects in the vicinity of the field. The electromagnetic field extends indefinitely throughout space and describes the electromagnetic interaction...
dosimeters.
Ionizing radiation, such as X-ray
X-ray
X-radiation is a form of electromagnetic radiation. X-rays have a wavelength in the range of 0.01 to 10 nanometers, corresponding to frequencies in the range 30 petahertz to 30 exahertz and energies in the range 120 eV to 120 keV. They are shorter in wavelength than UV rays and longer than gamma...
s, alpha rays, beta rays, and gamma ray
Gamma ray
Gamma radiation, also known as gamma rays or hyphenated as gamma-rays and denoted as γ, is electromagnetic radiation of high frequency . Gamma rays are usually naturally produced on Earth by decay of high energy states in atomic nuclei...
s, remains undetectable by the senses, and the damage it causes to the body is cumulative, related to the total dose received. Therefore, workers who are exposed to radiation, such as radiographers, nuclear power plant
Nuclear power plant
A nuclear power plant is a thermal power station in which the heat source is one or more nuclear reactors. As in a conventional thermal power station the heat is used to generate steam which drives a steam turbine connected to a generator which produces electricity.Nuclear power plants are usually...
workers, doctors using radiotherapy, workers in laboratories using radionuclide
Radionuclide
A radionuclide is an atom with an unstable nucleus, which is a nucleus characterized by excess energy available to be imparted either to a newly created radiation particle within the nucleus or to an atomic electron. The radionuclide, in this process, undergoes radioactive decay, and emits gamma...
s, and some HAZMAT
Hazmat
Hazmat, HazMat and similar terms can refer to:* Hazardous materials and items—see Dangerous goods** Hazchem—a system of hazardous chemical classification and firefighting modes** A hazmat suit is a type of protective clothing...
teams are required to wear dosimeters so their employers can keep a record of their exposure, to verify that it is below legally prescribed limits.
Crew members aboard NASA
NASA
The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...
Space Shuttle
Space Shuttle
The Space Shuttle was a manned orbital rocket and spacecraft system operated by NASA on 135 missions from 1981 to 2011. The system combined rocket launch, orbital spacecraft, and re-entry spaceplane with modular add-ons...
missions had access to four types of active dosimeters should a radiation contingency occur. Crew members were required to wear passive dosimeters at all times throughout the mission.
Common types of wearable dosimeters for ionizing radiation include:
- Quartz fiber dosimeterQuartz fiber dosimeterA quartz fiber dosimeter, sometimes simply called a pocket dosimeter, is a pen-like device that measures the cumulative dose of ionizing radiation received by the device. It is usually clipped to a person's clothing and worn to measure one's actual exposure to radiation...
- Film badge dosimeterFilm badge dosimeterThe film badge dosimeter, or film badge, is a dosimeter used for monitoring cumulative exposure to ionizing radiation. The badge consists of two parts: photographic film, and a holder. The film is removed and developed to measure exposure....
- Thermoluminescent dosimeterThermoluminescent DosimeterA thermoluminescent dosimeter, or TLD, is a type of radiation dosimeter. A TLD measures ionizing radiation exposure by measuring the amount of visible light emitted from a crystal in the detector when the crystal is heated. The amount of light emitted is dependent upon the radiation exposure...
- Solid state (MOSFETMOSFETThe metal–oxide–semiconductor field-effect transistor is a transistor used for amplifying or switching electronic signals. The basic principle of this kind of transistor was first patented by Julius Edgar Lilienfeld in 1925...
or silicon diode) dosimeter
The quartz fiber dosimeters have to be prepared, usually daily, with a positive charge from either a hand-wound or battery-powered charging unit. As the gas in the dosimeter chamber becomes ionized
Ionization
Ionization is the process of converting an atom or molecule into an ion by adding or removing charged particles such as electrons or other ions. This is often confused with dissociation. A substance may dissociate without necessarily producing ions. As an example, the molecules of table sugar...
by nuclear radiation the charge leaks away causing the fiber indicator to rise up the graduated scale.
Factories prepare film-badge dosimeters for one-time use. The level of radiation absorption is indicated by a change of color on the film badge's surface, which is compared to an indicator chart.
Manufacturing processes that treat products with ionizing radiation, such as food irradiation
Food irradiation
Food irradiation is the process of exposing food to ionizing radiation to destroy microorganisms, bacteria, viruses, or insects that might be present in the food. Further applications include sprout inhibition, delay of ripening, increase of juice yield, and improvement of re-hydration...
, use dosimeters to calibrate doses. These are different from personal dosimeters because they usually must have a greater range. They often consist of small blocks of material such as perspex.
One can also carry out the dosimetry of neutron radiation
Neutron radiation
Neutron radiation is a kind of ionizing radiation which consists of free neutrons. A result of nuclear fission or nuclear fusion, it consists of the release of free neutrons from atoms, and these free neutrons react with nuclei of other atoms to form new isotopes, which, in turn, may produce...
with a few specialised devices such as superheated drop detectors.
Gallery
File:Dosimeter ablesung.jpg|View through the above fiber dosimeter showing a reading
File:dosimeter sosna front.jpg|Russian Sosna radiometer-dosimeter (Front view)
File:dosimeter sosna back.jpg|Russian Sosna radiometer-dosimeter (Rear view)
File:rd1503.jpg|Radex RD1503, a modern personal radiometer-dosimeter
See also
- Comparison of dosimetersComparison of dosimetersThe following table compares a features of dosimeters....
- Geiger counterGeiger counterA Geiger counter, also called a Geiger–Müller counter, is a type of particle detector that measures ionizing radiation. They detect the emission of nuclear radiation: alpha particles, beta particles or gamma rays. A Geiger counter detects radiation by ionization produced in a low-pressure gas in a...
- Scintillation counterScintillation counterA scintillation counter measures ionizing radiation. The sensor, called a scintillator, consists of a transparent crystal, usually phosphor, plastic , or organic liquid that fluoresces when struck by ionizing radiation. A sensitive photomultiplier tube measures the light from the crystal...
- Richard R. Rosenthal
- Royal Observer CorpsRoyal Observer CorpsThe Royal Observer Corps was a civil defence organisation operating in the United Kingdom between 29 October 1925 and 31 December 1995, when the Corps' civilian volunteers were stood down....
- Operational instruments of the Royal Observer CorpsOperational instruments of the Royal Observer CorpsThe Royal Observer Corps was a civil defence organisation operating in the United Kingdom between October 1925 and 31 December 1995, when the Corps' civilian volunteers were stood down....
- TracercoTracercoTracerco is the oil and gas services subsidiary of British chemical company and conglomerate Johnson Matthey.- History :In 1958 ICI established a division to research the use of ionizing radiation within chemical processes...
, Manufacturer of Radiation Monitors