Since the middle of the last century, a new word has come into science - radiation. Its discovery made a revolution in the minds of physicists around the world and allowed us to discard some Newtonian theories and make bold assumptions about the structure of the Universe, its formation and our place in it. But all this is for specialists. The inhabitants just sigh and try to put together such disparate knowledge about this subject. Complicating the process is the fact that there are quite a few radiation units, and they are all eligible.
Terminology
The first term to get to know is, in fact, radiation. So they call the process of emission of any substance of the smallest particles, such as electrons, protons, neutrons, helium atoms and others. Depending on the type of particle, the radiation properties differ from each other. Radiation is observed either during the decay of substances into simpler ones, or during their synthesis.
Radiation units are conventional concepts that indicate how many elementary particles are released from a substance. At the moment, physics operates with seven different units and their combinations. This allows you to describe the various processes that occur with matter.
Radioactive decay is an arbitrary change in the structure of unstable atomic nuclei by the release of microparticles.
The decay constant is a statistical concept that predicts the probability of an atom breaking down over a specific period of time.
Half-life is the time period over which half of the total amount of a substance breaks up. For some elements, it is calculated in minutes, while in others - for years, and even decades.
What is radiation measured in
Radiation units are not the only ones used to evaluate the properties of radioactive materials. In addition to them, such quantities are used as:
- activity of a radiation source;
- flux density (the number of ionizing particles per unit area).
In addition, there is a difference in the description of the effects of radiation on living and non-living objects. So, if a substance is inanimate, then the following concepts apply to it:
- absorbed dose;
- exposure dose.
If the radiation affected the living tissue, then the following terms are used:
- equivalent dose;
- effective equivalent dose;
- dose rate.
The units of radiation are, as mentioned above, conditional numerical values adopted by scientists to facilitate calculations and build hypotheses and theories. Perhaps this is why there is no single universally accepted unit of measurement.
Curie
One of the units of measure for radiation is curie. It does not belong to the system (does not belong to the SI system). In Russia, it is used in nuclear physics and medicine. The activity of a substance will be equal to one curie if 3.7 billion radioactive decays occur in it in one second. That is, we can say that one curie is equal to three billion seven hundred million becquerels.
This number was due to the fact that Marie Curie (who introduced the term in science) conducted her experiments on radium and took as its basis its decay rate. But over time, physicists decided that the numerical value of this unit should be tied to another - becquerel. This allowed us to avoid some errors in mathematical calculations.
In addition to curie, you can often find multiple or fractional units, such as:
- mega-curie (equal to 3.7 per 10 to 16 degrees becquerels);
- kilo curie (3.7 thousand billion becquerels);
- millikuri (37 million becquerels);
- microcurie (37 thousand becquerels).
Using this unit, the volume, surface or specific activity of a substance can be expressed.
Becquerel
The becquerel radiation dose unit is a system unit and is part of the International System of Units (SI). It is the simplest, because the activity of radiation in one becquerel means that only one radioactive decay per second occurs in a substance.
It got its name in honor of Antoine Henri Becquerel, a French physicist. The name was approved at the end of the last century and is still in use. Since this is a fairly small unit, decimal prefixes are used to indicate activity: kilo, milli, micro, and others.
Recently, off-system units such as Curie and Rutherford have been used along with becquerels. One Rutherford equals one million becquerels. In the description of volumetric or surface activity, one can find the symbols becquerel per kilogram, becquerel per meter (square or cubic) and their various derivatives.
Roentgen
The unit of measurement of x-ray radiation is also not a system, although it is used everywhere to indicate the exposure dose of the received gamma radiation. One x-ray is equal to a dose of radiation at which one cubic centimeter of air at standard atmospheric pressure and zero temperature carries a charge equal to 3.3 * (10 * -10). This is equal to two million pairs of ions.
Despite the fact that under the legislation of the Russian Federation, most off-system units are prohibited, x-rays are used in the labeling of dosimeters. But they will soon cease to be used, as it turned out to be more practical to record and calculate everything in grey and sievert.
Glad
The unit of radiation rad is outside the SI system and is equal to the amount of radiation at which one millionth joule of energy is transmitted to one gram of matter. That is, one is glad - it is 0.01 joules per kilogram of matter.
The material that absorbs energy can be both living tissue, and other organic and inorganic substances and substances: soil, water, air. As an independent unit, rad was introduced in 1953 and in Russia has the right to be used in physics and medicine.
Gray
This is another radiation unit recognized by the International System of Units. It reflects the absorbed dose of radiation. It is believed that the substance received a dose of one gray, if the energy that was transmitted with the radiation is equal to one joule per kilogram.
This unit got its name in honor of the English scientist Lewis Gray and was officially introduced into science in 1975. According to the rules, the full name of the unit is written with a small letter, but its abbreviation is capitalized. One gray is equal to one hundred radam. In addition to simple units, in science they also use their multiple and fractional equivalents, such as kilogrey, megagrey, decigray, centigray, microgray and others.
Sievert
The sievert radiation unit is used to indicate effective and equivalent radiation doses and is also included in the SI system, like gray and becquerel. Used in science since 1978. One sievert is equal to the energy absorbed by a kilogram of tissue after exposure to one gray gamma rays. The unit received its name in honor of Rolf Sievert, a scientist from Sweden.
Judging by definition, sievert and gray are equal, that is, the equivalent and absorbed doses are the same size. But there is still a difference between them. When determining the equivalent dose, it is necessary to take into account not only the quantity, but also other radiation properties, such as the wavelength, amplitude, and which particles represent it. Therefore, the numerical value of the absorbed dose is multiplied by the radiation quality factor.
So, for example, all other things being equal, the absorbed effect of alpha particles will be twenty times stronger than the same dose of gamma radiation. In addition, it is necessary to take into account the tissue coefficient, which shows how the organs react to radiation. Therefore, the equivalent dose is used in radiobiology, and the effective one is used in occupational health (to standardize the effects of radiation).
Solar constant
There is a theory that life on our planet appeared due to solar radiation. Units of radiation from a star are calories and watts divided by a unit of time. This was decided because the amount of radiation from the Sun is determined by the amount of heat that the objects receive and the intensity with which it comes. Only half a millionth of the total amount of energy emitted reaches the earth.
Radiation from stars propagates in space at the speed of light and enters our atmosphere in the form of rays. The spectrum of this radiation is quite wide - from "white noise", that is, radio waves, to x-rays. Particles that also come with radiation are protons, but sometimes there can be electrons (if the energy release was large).
The radiation received from the Sun is the driving force of all living processes on the planet. The amount of energy we receive depends on the time of year, the position of the star above the horizon, and the transparency of the atmosphere.
The effects of radiation on living things
If living tissues of the same characteristics are irradiated with different types of radiation (in the same dose and intensity), then the results will vary. Therefore, to determine the consequences, only the absorbed or exposure dose is not enough, as is the case with inanimate objects. Units of measure of penetrating radiation, such as sievert rem and gray, appear on the stage, which indicate an equivalent dose of radiation.
Equivalent is the dose absorbed by living tissue and multiplied by a conditional (tabular) coefficient that takes into account how dangerous this or that type of radiation is. Most often, sievert is used to measure it. One sievert equals one hundred rem. The larger the coefficient, the correspondingly more dangerous the radiation. So, for photons it is one, and for neutrons and alpha particles, twenty.
Since the accident at the Chernobyl nuclear power plant in Russia and other CIS countries, special attention has been paid to the level of radiation exposure to humans. The equivalent dose from natural sources of radiation should not be higher than five millisieverts per year.
The effect of radionuclides on non-living objects
Radioactive particles carry a charge of energy that they transfer to a substance when they collide with it. And the more particles in its path come into contact with a certain amount of matter, the more energy it will receive. Its quantity is estimated in doses.
- The absorbed dose is the amount of radiation that has been received by a unit of substance. Measured in gree. This value does not take into account the fact that the effect of different types of radiation on matter is different.
- Exposure dose - represents the absorbed dose, but taking into account the degree of ionization of the substance from exposure to various radioactive particles. Measured in pendants per kilogram or x-rays.