What Is a Radiation Monitor?
A radiation monitor is an instrument that measures the intensity or quantity of radiation.
There are five main types of radiation, each measured according to a different principle. Some measure the amount of radiation in a space, while others measure the cumulative amount of radiation received by an individual.
Radiation is also present in the everyday environment in which we live, although it has a scary image due to atomic bombs, nuclear weapons, and nuclear power plant accidents. In radiation monitoring, the instrument to be used depends on the nature of the radiation to be measured.
In addition, the radiation monitor that can be used depends on whether the radiation level is high or low, or on the type of radiation (alpha, gamma, beta, or X-rays).
Uses of Radiation Monitors
1. Scintillation Radiation Monitor
Scintillation radiation monitors are used to measure the radiation dose rate in the general environment. Since the measured value varies with the distance from the source of contamination, it can also be used to determine the location of the contamination source.
The radiation dose rate in the air is the amount of radiation in the air per hour. Radiation in the air is radiation that travels through space and can come from outer space or from natural sources.
The unit of radiation dose rate is hGy/h (nanogray per hour), where Gy (gray) is the amount of radiation absorbed by a material, including the human body, and is also called absorbed dose.
2. GM (Geiger-Mueller) Tube Radiation Monitor
GM tube radiation monitors are mainly used to measure beta radiation and the degree of body surface contamination. They can also be used to measure gamma and X-rays, as well as air radiation dose rate, but their accuracy is inferior to that of the scintillation type.
It is also used to measure the presence of radioactive materials on the clothing and body surfaces of workers, etc., and to analyze nuclides in research experiments.
3. Ionization Chamber Radiation Monitor
Ionization chamber radiation monitors are used to measure the radiation dose rate in the air. However, since the ionization chamber type can only detect strong radiation, these radiation monitors are used in radiation-intensive environments, such as in the manufacture of X-ray equipment such as CT and X-ray machines, in the medical field where such equipment is used, and in nuclear power plants.
4. Personal Dosimeters
Personal dosimeters measure the cumulative amount of radiation exposure of the wearer over a certain period of time. Personal dosimeters are used in facilities that handle radioactive materials.
Areas with a high potential for radiation exposure, such as nuclear power plants, are designated as controlled areas, and it is required by law that people who enter these areas wear personal dosimeters to measure their radiation exposure during the time they are there.
Principle of Radiation Monitors
Radiation interacts with matter as it passes through it. The principle of radiation monitors is based on the interaction between radiation and matter.
GM-tube radiation monitors and ionization chamber radiation monitors use the ionizing action between radiation and gas. The GM-tube and ionization chamber radiation monitors calculate the radiation dose by converting the electric current generated by the ionization into an electrical signal.
Scintillation radiation monitors use the excitation action between materials. Excitation is the process by which radiation imparts energy to the electrons of an atomic nucleus, causing them to be repelled into an outer orbital. In the excitation process, the energy of the nucleus is emitted as light when it returns to the stable ground state from the high-energy excited state in the activated state. The weak light emitted by the scintillator in this process is amplified by a photomultiplier tube and converted into an electrical signal to measure radiation.
Scintillators are materials that emit light in response to X-rays and gamma rays, and are commonly used to measure radiation, such as sodium iodide (Nal) and cesium iodide (Csl). The principle of fluorescence is also used in personal dosimeters, which are called individual photon stimulated luminescence dosimeters, fluorescent glass dosimeters, or electronic dosimeters.
Other Information on Radiation Monitors
Radiation Units
In the news about radiation, you may hear unfamiliar units of measurement used. The main units are Bq (Becquerel) and Sv (Sievert).
The becquerel is the number of atomic nuclei that decay in one second and represents the ability of a radioactive material to produce radiation. The two units are used to express the radiation on the side of the generator and the radiation on the side of the receiver.