A little bit about radiation
I'm already used to the fact that for most people, radiation is a field of mythology, not science. But then I stumbled upon this entry , in which the professional already explains the insane danger of Soviet smoke detectors. After that, I decided that it was worthwhile to engage in enlightenment.
What is the answer to the question "Is radiation harmful?" The same as the questions "is the temperature harmful?" Or "is the light harmful?". It is not the phenomenon itself that is harmful, but the output of its numerical parameters beyond the optimal limits for life. Numerous animal experiments showed a slight increase in life expectancy, increased immunity, etc. with some additional, relatively natural, radiation. They also showed a decrease in all these parameters with a further increase in the dose of radiation. Of course, there was no dose that is universal for all animal species, which gives an optimal result, it is different for all. No one knows what level of radiation would be ideal for a person, because for this, controlled experiments would have to be performed on tens of thousands of people.
But another thing is known: a person has different sensitivity to different factors. So, for example, a person feels good at a temperature of 300 K (27 ° C), but if you change it only by 10%, to -3 ° C or 57 ° C, then without protective equipment (appropriate clothing) only a few trained people can to survive. If you change it by 20%, to -33 ° C or 87 ° C, then no one without protection will survive for long. But a smooth change in illumination of 10-20 times a person does not notice at all. The difference between bright artificial lighting and illumination outside on a sunny day is about 1000 times ... Of course, in complete darkness, a person can survive, but with great difficulty, and too bright lighting will cause a problem with the temperature. But in general, the allowable range of change is many thousands of times.
What is the person's sensitivity to radiation exposure? Low enough. The natural level of radiation in different parts of the world varies extremely. If on average throughout the world a person receives a dose of 2.4 mSv per year, in some places only 1 mSv, and in others 10 or even 15-20 more. But no reliable data showing that this variation has an impact on health has been found. For example, residents of Switzerland, which is famous for the high life expectancy of its citizens, are exposed to increased doses of radiation. Astronauts receive even more radiation doses - about 0.5 mSv per ... day! Those. in a month they receive as much as the inhabitants of the most radioactive parts of the planet in a year.
')
Of course, this is not a reason to go on a tour under the sarcophagus of the fourth power unit of the Chernobyl NPP. There you will receive a dose in a minute more than a month on the ISS, and such exposure absolutely reliably has an extremely adverse effect on life expectancy. But you shouldn't be afraid of everything and everyone either.
In the last section, I used the “mSv” unit everywhere. This is the "milisievert." Let's see what it is, and what the general unit of measurement is here.
Let's start with the fact that at the hearing - X-rays (P). In X-rays, only x-rays and gamma rays are measured. This unit measures the so-called exposure dose, i.e. how many ions produce radiation in dry air. It is extremely convenient when measuring using an ionization chamber, since This type of sensor measures precisely the amount of ions (more precisely, their total charge). Dose in X-rays can be obtained directly, while all other doses are measured indirectly, leaving room for measurement errors. But, on the other hand, this dose does not directly indicate what harm a person causes radiation, and it cannot be used for beta and alpha radiation with other neutrons, it is not defined for them.
The next unit is glad. Glad is the unit of the absorbed dose of any radiation. Those. how much energy of ionizing radiation is absorbed by a unit of mass of a substance. Glad is 100 erg per 1 gram or 0.01 J per 1 kg. Also in rades measured kerma. Kerma is how much kinetic energy get charged particles of a substance when this substance absorbs non-charged ionizing radiation (gamma, neutrons). In most cases, the absorbed dose and kerma very precisely coincide, so do not fill your head with this. If the air absorbs 0.88 rad of gamma radiation, then ions will appear in it at 1 R. It can be said that 1 P = 0.88 is happy, and 1 rad of gamma radiation is equal to 1.14 R. However, because . all the same, the air does not exactly correspond to human tissues, and there are different tissues, plus the dosimeters error is rarely less than 20%, it is usually considered 1 P = 1 glad. The disadvantage of being glad, or rather of the absorbed dose, is that it does not take into account the significantly different effects on the body of various types of radiation.
The next unit is the biological equivalent of rad (rem). A rem is an equivalent dose unit. Those. it takes into account that fast neutrons with the same energy will cause 10, and alpha particles - 20 times more harm to the body than gamma or beta radiation. The corresponding coefficients are (or can be obtained) for absolutely any types of ionizing radiation. Also, the effective dose is measured in rems, which takes into account the different sensitivities of different organs. If a person is irradiated completely evenly, then the equivalent and effective dose is the same, but if some parts of the body are irradiated more strongly and some are weaker, there may be noticeable differences. For example, hands withstand very large doses, but the spinal cord is very sensitive to radiation. Ream also measures the ambivalent dose equivalent — such a “spherical dose in a vacuum.” No kidding, it is defined for a 30 cm ball of a strictly standardized composition, used for all sorts of tests, simulations, etc.
Next we have a gray (Gr). Gray is an analogue of glad in the SI system. 1 Gy = 1 J / kg = 100 rad.
And finally, a sievert (Sv). This is an analogue of the rem in SI. 1 Sv = 100 rem. Accordingly, the mSv that I used in the first section is 0.001 Sv or 0.1 rem.
In addition to the dose, there is also the activity of a radioactive substance. Those. how many decays in it occur in a certain time. Activity is measured either in the curie (Ci) or in Becquerel (Bq). Curie - the activity of one gram of radium-226, a very large value. Becquerel - one decay per second, very small value. 1 Ki = 37 GBq.
To make it easier to navigate, here are some numbers:
- the level of gamma radiation in my room is about 7 ÎĽR / h, 0.07 ÎĽGy / h and 0.07 ÎĽSv / h (power, respectively, of the exposure, absorbed and equivalent doses). The level of gamma radiation on granite platforms of the Moscow Metro is about twice as high (plus the dose of alpha lung exposure from elevated radon levels);
- a single dose at which radiation sickness can begin - 100 R, 1 Gr and 1 Sv;
- the activity of natural radioactive potassium-40 in a banana is about 20 Bq, in a kilogram of bananas - 130 Bq.
In principle, there are a huge number of different instruments and methods for measuring radiation, but I will only talk here about what, in principle, a person who does not work in the appropriate directions may encounter.
You can find “radioactivity indicators”, “dosimeters” and “dosimeters-radiometers” in stores.
The first ones are devices that do not pass any significant tests and generally do not pretend to accuracy of measurements. Almost always they are made on the basis of a Geiger counter type SBM-20. More rarely, on the basis of a miniature SBM-21 or on the basis of alpha-sensitive counters, for example, Beta-1 or Beta-2. Many believe that such devices may underestimate the testimony. Some "professionals" claim that at low energy gamma radiation, at the level of 30-100 keV, the instruments on the SBM-20 and the SBM-21 are underestimated several times, and they are not fixed below. My experience shows that everything is exactly the opposite: at low energy gamma radiation (experiments were made with 59 keV), they are at times overestimating their readings. Of course, they will not fix the gamma radiation of very low energy, but it also does not pose a great danger, since absorbed even in the skin. Beta-1 and Beta-2 capture all types of radiation, and even more overestimate the readings with low energy gamma radiation.
The honest manufacturer usually calls the dosimeter a device, the accuracy of measurement to which any attention was paid. Most often, they are also made on the basis of the SBM-20, but it is already closed by a special removable filter that attenuates low-energy gamma radiation and completely absorbs beta radiation. This allows you to accurately measure the level of gamma radiation in a wide range of energies. Also, these devices are usually able to integrate the readings for a long time, showing not only the dose rate, but also the dose itself. Devices contain better Beta-1, Beta-2 or other sensors with a mica window for low-energy beta radiation and alpha-radiation, also equipped with filters. Very expensive devices can use semiconductor or scintillator sensors, which have great sensitivity to gamma radiation and do not just capture particles, but measure their energy. This allows you to accurately measure the dose, and some models even know how to determine the isotopes that cause irradiation. However, semiconductors and scintillators can play a cruel joke: their sensitivity is highly dependent on energy, so it’s not just possible to measure it, but it’s definitely necessary. And it is necessary to take into account qualitatively the dependence of sensitivity on energy. If such a sensor is inserted into the device only for the loud “scintillator” inscription, then the measurement accuracy may be worse for it than for cheap indicators of radioactivity.
A dosimeter-radiometer is a device that, in addition to the dose of gamma radiation, also measures the flow of beta particles (with the corresponding sensors, alpha). The two previous points also fix beta radiation (dosimeters with the filter removed), but they continue to recalculate the readings into X-rays or Sievert, as if it were gamma radiation. The result is absolutely wrong: if for gamma radiation the probability of a particle fixing with a Geiger counter is directly proportional to its energy in a fairly wide range (somewhere from 0.3 to 1.5 MeV), and this range is expanded down to 0 by filters, 03-0.05 MeV, there is nothing like this for beta radiation. In the first approximation, above the defined energy limit, the sensor captures almost all beta particles, and below, not one. It is the same with alpha radiation (if the meter fixes it in principle). The radiometer can “say” that you are now measuring beta radiation, and then it will recalculate readings into the number of particles per square centimeter of the sensor cross-section area per unit of time. First, you measure with a filter to find out the gamma background, then without it, you subtract the first from the second - and here is the flow of beta particles. For alpha, everything is the same, only a second filter is added there, which delays it, but passes beta particles. Sometimes it is built in, sometimes you have to take it yourself, like a sheet of paper.
There are also software dosimeters for smartphones that use a camera covered with opaque material as an ersatz detector. They really work, but in my experience it is not necessary to expect accuracy from them, they can be mistaken at times in any direction.
It is also worth noting that with low levels of radiation, the readings of all the devices are not very accurate: they fix only about a dozen particles per measurement cycle, so that the statistical error becomes comparable with the measured value. If the device now shows 0.07 µSv / h, and after a minute - 0.14 µSv / h, this absolutely does not mean that the level of radiation has doubled. Most likely, as it was 0.10 µSv / h, it remained.
Another note on the actual measurements: they must be carried out so that the sensor of the device can be considered a point. Those. either the source of radiation, or the distance from it to the sensor should be several times larger than the sensor itself. If you poke a drop of radium paint on the tip of the toggle switch to the center of some Beta-2, then at different points of the sensor the level of radiation differs by several orders of magnitude. What a sensor measures in such conditions is “God only knows.” Measurements “on the surface” are permissible either for large sources (polluted soil, for example), or when we are not trying to measure it, but only with maximum sensitivity to fix the presence of radiation.
Indicator of radioactivity at the site of radioactive contamination
Professional scintillator dosimeter at the site of radioactive contamination (radiation level - the numbers below)
Software dosimeter. In this particular case, 3-4 times underestimates
What sources of radiation can be found in everyday life? Variety.
For example, everything that contains a lot of potassium, potash fertilizers, dietary salt with the addition of potassium, etc., is radioactive due to the content of natural potassium-40. Man, by the way, is also radioactive, because Potassium is an essential element of the body.
If we take the sources more seriously, these are thoriated welding electrodes (for example, WT-20), some old lenses with the addition of thorium oxide in glass, some old watches and other devices with radium backlight scales (now the backlight does not work from - due to burnout of the phosphor, radium is stored for thousands of years), ionization smoke detectors on americium-241, old ionization smoke detectors on plutonium-239 (weapon quality, by the way), etc.
As long as all this remains unharmed, it is usually not dangerous. Problems can arise only with the destruction of devices, because in this case, particles of alpha-active materials can get into the lungs and create strong local irradiation there. The risk of cancer is greatly increased. By the way, smokers' lung cancer in a noticeable degree is caused by the same: tobacco contains alpha-active polonium-210, the same one that Litvinenko was poisoned with.
Also, all these things are perfectly legal to use without special permissions: only once did I get a pressure gauge, the radiation level of which went beyond the permissible limits for unlicensed use (1 µSv / h at a distance of 10 cm from the surface), but it was from the MIG-21 fighter. However, laws in our country are not very fulfilled ... "Specialists" can easily declare that everything that has a radiation level of more than 30 μR / h right on the surface must be withdrawn. And the judges do not really understand such subtleties as radiation safety standards ... There is at least one precedent when the court took away a lens from a person, and they didn’t imprison him only because he did not know about his radioactivity. By all official regulations, this lens could be used.
Only industrial sources of radiation, operating X-ray machines and uncontrolled accidental emissions pose a real danger. Fortunately, it’s not so easy to face them. Although history uses precedents ...
Plutonium source from the smoke detector RID-1. The one about which horror stories tell in the article that provoked the writing of this text. While intact, does not pose a significant danger.
Relatively safe instrument with radium illumination
A large accumulation of relatively safe devices may not be as safe anymore.
A rare example of a device with radium illumination, more than a dozen times beyond the permissible limits
Industrial source that may pose a real danger
Contaminated area
The result of an uncontrolled accidental release half a century ago
Nuclear reactor core
Radiation damage
What is the answer to the question "Is radiation harmful?" The same as the questions "is the temperature harmful?" Or "is the light harmful?". It is not the phenomenon itself that is harmful, but the output of its numerical parameters beyond the optimal limits for life. Numerous animal experiments showed a slight increase in life expectancy, increased immunity, etc. with some additional, relatively natural, radiation. They also showed a decrease in all these parameters with a further increase in the dose of radiation. Of course, there was no dose that is universal for all animal species, which gives an optimal result, it is different for all. No one knows what level of radiation would be ideal for a person, because for this, controlled experiments would have to be performed on tens of thousands of people.
But another thing is known: a person has different sensitivity to different factors. So, for example, a person feels good at a temperature of 300 K (27 ° C), but if you change it only by 10%, to -3 ° C or 57 ° C, then without protective equipment (appropriate clothing) only a few trained people can to survive. If you change it by 20%, to -33 ° C or 87 ° C, then no one without protection will survive for long. But a smooth change in illumination of 10-20 times a person does not notice at all. The difference between bright artificial lighting and illumination outside on a sunny day is about 1000 times ... Of course, in complete darkness, a person can survive, but with great difficulty, and too bright lighting will cause a problem with the temperature. But in general, the allowable range of change is many thousands of times.
What is the person's sensitivity to radiation exposure? Low enough. The natural level of radiation in different parts of the world varies extremely. If on average throughout the world a person receives a dose of 2.4 mSv per year, in some places only 1 mSv, and in others 10 or even 15-20 more. But no reliable data showing that this variation has an impact on health has been found. For example, residents of Switzerland, which is famous for the high life expectancy of its citizens, are exposed to increased doses of radiation. Astronauts receive even more radiation doses - about 0.5 mSv per ... day! Those. in a month they receive as much as the inhabitants of the most radioactive parts of the planet in a year.
')
Of course, this is not a reason to go on a tour under the sarcophagus of the fourth power unit of the Chernobyl NPP. There you will receive a dose in a minute more than a month on the ISS, and such exposure absolutely reliably has an extremely adverse effect on life expectancy. But you shouldn't be afraid of everything and everyone either.
Radiation Units
In the last section, I used the “mSv” unit everywhere. This is the "milisievert." Let's see what it is, and what the general unit of measurement is here.
Let's start with the fact that at the hearing - X-rays (P). In X-rays, only x-rays and gamma rays are measured. This unit measures the so-called exposure dose, i.e. how many ions produce radiation in dry air. It is extremely convenient when measuring using an ionization chamber, since This type of sensor measures precisely the amount of ions (more precisely, their total charge). Dose in X-rays can be obtained directly, while all other doses are measured indirectly, leaving room for measurement errors. But, on the other hand, this dose does not directly indicate what harm a person causes radiation, and it cannot be used for beta and alpha radiation with other neutrons, it is not defined for them.
The next unit is glad. Glad is the unit of the absorbed dose of any radiation. Those. how much energy of ionizing radiation is absorbed by a unit of mass of a substance. Glad is 100 erg per 1 gram or 0.01 J per 1 kg. Also in rades measured kerma. Kerma is how much kinetic energy get charged particles of a substance when this substance absorbs non-charged ionizing radiation (gamma, neutrons). In most cases, the absorbed dose and kerma very precisely coincide, so do not fill your head with this. If the air absorbs 0.88 rad of gamma radiation, then ions will appear in it at 1 R. It can be said that 1 P = 0.88 is happy, and 1 rad of gamma radiation is equal to 1.14 R. However, because . all the same, the air does not exactly correspond to human tissues, and there are different tissues, plus the dosimeters error is rarely less than 20%, it is usually considered 1 P = 1 glad. The disadvantage of being glad, or rather of the absorbed dose, is that it does not take into account the significantly different effects on the body of various types of radiation.
The next unit is the biological equivalent of rad (rem). A rem is an equivalent dose unit. Those. it takes into account that fast neutrons with the same energy will cause 10, and alpha particles - 20 times more harm to the body than gamma or beta radiation. The corresponding coefficients are (or can be obtained) for absolutely any types of ionizing radiation. Also, the effective dose is measured in rems, which takes into account the different sensitivities of different organs. If a person is irradiated completely evenly, then the equivalent and effective dose is the same, but if some parts of the body are irradiated more strongly and some are weaker, there may be noticeable differences. For example, hands withstand very large doses, but the spinal cord is very sensitive to radiation. Ream also measures the ambivalent dose equivalent — such a “spherical dose in a vacuum.” No kidding, it is defined for a 30 cm ball of a strictly standardized composition, used for all sorts of tests, simulations, etc.
Next we have a gray (Gr). Gray is an analogue of glad in the SI system. 1 Gy = 1 J / kg = 100 rad.
And finally, a sievert (Sv). This is an analogue of the rem in SI. 1 Sv = 100 rem. Accordingly, the mSv that I used in the first section is 0.001 Sv or 0.1 rem.
In addition to the dose, there is also the activity of a radioactive substance. Those. how many decays in it occur in a certain time. Activity is measured either in the curie (Ci) or in Becquerel (Bq). Curie - the activity of one gram of radium-226, a very large value. Becquerel - one decay per second, very small value. 1 Ki = 37 GBq.
To make it easier to navigate, here are some numbers:
- the level of gamma radiation in my room is about 7 ÎĽR / h, 0.07 ÎĽGy / h and 0.07 ÎĽSv / h (power, respectively, of the exposure, absorbed and equivalent doses). The level of gamma radiation on granite platforms of the Moscow Metro is about twice as high (plus the dose of alpha lung exposure from elevated radon levels);
- a single dose at which radiation sickness can begin - 100 R, 1 Gr and 1 Sv;
- the activity of natural radioactive potassium-40 in a banana is about 20 Bq, in a kilogram of bananas - 130 Bq.
Radiation measuring instruments
In principle, there are a huge number of different instruments and methods for measuring radiation, but I will only talk here about what, in principle, a person who does not work in the appropriate directions may encounter.
You can find “radioactivity indicators”, “dosimeters” and “dosimeters-radiometers” in stores.
The first ones are devices that do not pass any significant tests and generally do not pretend to accuracy of measurements. Almost always they are made on the basis of a Geiger counter type SBM-20. More rarely, on the basis of a miniature SBM-21 or on the basis of alpha-sensitive counters, for example, Beta-1 or Beta-2. Many believe that such devices may underestimate the testimony. Some "professionals" claim that at low energy gamma radiation, at the level of 30-100 keV, the instruments on the SBM-20 and the SBM-21 are underestimated several times, and they are not fixed below. My experience shows that everything is exactly the opposite: at low energy gamma radiation (experiments were made with 59 keV), they are at times overestimating their readings. Of course, they will not fix the gamma radiation of very low energy, but it also does not pose a great danger, since absorbed even in the skin. Beta-1 and Beta-2 capture all types of radiation, and even more overestimate the readings with low energy gamma radiation.
The honest manufacturer usually calls the dosimeter a device, the accuracy of measurement to which any attention was paid. Most often, they are also made on the basis of the SBM-20, but it is already closed by a special removable filter that attenuates low-energy gamma radiation and completely absorbs beta radiation. This allows you to accurately measure the level of gamma radiation in a wide range of energies. Also, these devices are usually able to integrate the readings for a long time, showing not only the dose rate, but also the dose itself. Devices contain better Beta-1, Beta-2 or other sensors with a mica window for low-energy beta radiation and alpha-radiation, also equipped with filters. Very expensive devices can use semiconductor or scintillator sensors, which have great sensitivity to gamma radiation and do not just capture particles, but measure their energy. This allows you to accurately measure the dose, and some models even know how to determine the isotopes that cause irradiation. However, semiconductors and scintillators can play a cruel joke: their sensitivity is highly dependent on energy, so it’s not just possible to measure it, but it’s definitely necessary. And it is necessary to take into account qualitatively the dependence of sensitivity on energy. If such a sensor is inserted into the device only for the loud “scintillator” inscription, then the measurement accuracy may be worse for it than for cheap indicators of radioactivity.
A dosimeter-radiometer is a device that, in addition to the dose of gamma radiation, also measures the flow of beta particles (with the corresponding sensors, alpha). The two previous points also fix beta radiation (dosimeters with the filter removed), but they continue to recalculate the readings into X-rays or Sievert, as if it were gamma radiation. The result is absolutely wrong: if for gamma radiation the probability of a particle fixing with a Geiger counter is directly proportional to its energy in a fairly wide range (somewhere from 0.3 to 1.5 MeV), and this range is expanded down to 0 by filters, 03-0.05 MeV, there is nothing like this for beta radiation. In the first approximation, above the defined energy limit, the sensor captures almost all beta particles, and below, not one. It is the same with alpha radiation (if the meter fixes it in principle). The radiometer can “say” that you are now measuring beta radiation, and then it will recalculate readings into the number of particles per square centimeter of the sensor cross-section area per unit of time. First, you measure with a filter to find out the gamma background, then without it, you subtract the first from the second - and here is the flow of beta particles. For alpha, everything is the same, only a second filter is added there, which delays it, but passes beta particles. Sometimes it is built in, sometimes you have to take it yourself, like a sheet of paper.
There are also software dosimeters for smartphones that use a camera covered with opaque material as an ersatz detector. They really work, but in my experience it is not necessary to expect accuracy from them, they can be mistaken at times in any direction.
It is also worth noting that with low levels of radiation, the readings of all the devices are not very accurate: they fix only about a dozen particles per measurement cycle, so that the statistical error becomes comparable with the measured value. If the device now shows 0.07 µSv / h, and after a minute - 0.14 µSv / h, this absolutely does not mean that the level of radiation has doubled. Most likely, as it was 0.10 µSv / h, it remained.
Another note on the actual measurements: they must be carried out so that the sensor of the device can be considered a point. Those. either the source of radiation, or the distance from it to the sensor should be several times larger than the sensor itself. If you poke a drop of radium paint on the tip of the toggle switch to the center of some Beta-2, then at different points of the sensor the level of radiation differs by several orders of magnitude. What a sensor measures in such conditions is “God only knows.” Measurements “on the surface” are permissible either for large sources (polluted soil, for example), or when we are not trying to measure it, but only with maximum sensitivity to fix the presence of radiation.
Indicator of radioactivity at the site of radioactive contamination
Professional scintillator dosimeter at the site of radioactive contamination (radiation level - the numbers below)
Software dosimeter. In this particular case, 3-4 times underestimates
Radiation at home
What sources of radiation can be found in everyday life? Variety.
For example, everything that contains a lot of potassium, potash fertilizers, dietary salt with the addition of potassium, etc., is radioactive due to the content of natural potassium-40. Man, by the way, is also radioactive, because Potassium is an essential element of the body.
If we take the sources more seriously, these are thoriated welding electrodes (for example, WT-20), some old lenses with the addition of thorium oxide in glass, some old watches and other devices with radium backlight scales (now the backlight does not work from - due to burnout of the phosphor, radium is stored for thousands of years), ionization smoke detectors on americium-241, old ionization smoke detectors on plutonium-239 (weapon quality, by the way), etc.
As long as all this remains unharmed, it is usually not dangerous. Problems can arise only with the destruction of devices, because in this case, particles of alpha-active materials can get into the lungs and create strong local irradiation there. The risk of cancer is greatly increased. By the way, smokers' lung cancer in a noticeable degree is caused by the same: tobacco contains alpha-active polonium-210, the same one that Litvinenko was poisoned with.
Also, all these things are perfectly legal to use without special permissions: only once did I get a pressure gauge, the radiation level of which went beyond the permissible limits for unlicensed use (1 µSv / h at a distance of 10 cm from the surface), but it was from the MIG-21 fighter. However, laws in our country are not very fulfilled ... "Specialists" can easily declare that everything that has a radiation level of more than 30 μR / h right on the surface must be withdrawn. And the judges do not really understand such subtleties as radiation safety standards ... There is at least one precedent when the court took away a lens from a person, and they didn’t imprison him only because he did not know about his radioactivity. By all official regulations, this lens could be used.
Only industrial sources of radiation, operating X-ray machines and uncontrolled accidental emissions pose a real danger. Fortunately, it’s not so easy to face them. Although history uses precedents ...
Plutonium source from the smoke detector RID-1. The one about which horror stories tell in the article that provoked the writing of this text. While intact, does not pose a significant danger.
Relatively safe instrument with radium illumination
A large accumulation of relatively safe devices may not be as safe anymore.
A rare example of a device with radium illumination, more than a dozen times beyond the permissible limits
Industrial source that may pose a real danger
Contaminated area
The result of an uncontrolled accidental release half a century ago
Nuclear reactor core
Source: https://habr.com/ru/post/362171/
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