Radiation. Basic concepts. (part 1)

In this article we are not going to dive into deep details of the physical fundamentals. Our purpose is to understand the essence of the radioactive impacts on humans; the exposure limits, conditions of attaining them and the methodology to monitor.
So, let us describe outlined what radiation is and how it is interesting to us:
• Radiation – in general, these are all types of radiation existing in nature – radio waves, visible light, ultraviolet light and so on. In this article, we are not interested in all radiation, but only its “harmful part”, that is, the part that is dangerous for our body and which arises as a result of the use of nuclear weapons in wartime, man-made disasters at nuclear power plants, natural natural radiation and others cases involving radioactive substances.
• In our case, it’s more accurate not to talk about radiation (as a more general concept) but about ionizing radiation. Ionizing radiation includes: both electromagnetic radiation in the form of gamma radiation and x-ray radiation, and flows of charged particles (alpha and beta radiation).
• The emphasis on ionizing radiation is based on the fact that this radiation has the ability to ionize molecules in the cells of living creatures – which leads to a violation of the normal functioning of the body as a whole.
So, without going into details, we can state that ionization radiation, wherever it comes from, is harmful to health. You need to know where it is present, how to control and measure it, what amounts are dangerous, which are safe, how to behave in a situation of ionization radiation (saying simpler – in case of radiation)
Ionization radiation – it is everywhere and even without war or a man-made disaster. Do we have fluorography, take a “snapshot” of the dentist’s tooth, fly in an airplane (the higher the Earth’s surface, the higher the ionization background), are in an unventilated basement (radioactive gas accumulates radon) or just a natural radiation background … – everywhere has its own dose. Building materials and other objects can emit radiation. It is important to deal with this issue wisely, understanding and measuring specific quantitative radiation data and comparing them with the norms.
What are the standards? What to fear and what to pay no attention to?
We immediately ask ourselves a question – how to quantify radiation? The main unit of measurement of radiation (ionization radiation), which may be of interest to people, can be considered – Sievert (Sv) and its derivatives millisievert (mSv) and microsievert (µSv), one thousandth and one millionth of Sievert, respectively. Today it is the world’s accepted basic unit for measuring ionization radiation in terms of its effect on a living organism. There are other units but they are used less and less in other cases, such as “x-ray”, “rem”, “curie”, “gray”. Previously, more often used the “x-ray”. 1 Sievert = 100 X-ray.
Sievert – in simple terms, this is a universal quantitative indicator (dose), which determines the dependence of the reaction of the human body to the effects of ionization radiation. Sievert comprehensively combines in one indicator a whole series of interdependencies between the reaction of the body and human organs to various types of radiation. If you figuratively describe what 1 Sievert is, then we can say that this is such a dose of radiation, having received that, a person in 50% of cases will receive radiation sickness with a fatal outcome. 0.2 Sievert – a high probability of developing cancer, 3 Sievert – a high probability of dying, 6 Sievert – a definite quick death. Here is such an “amazing” unit of measurement … Let’s just say – 1 Sievert is a very large dose and it is better not to get it.
Also, a very important unit for evaluating the radiation power is Sievert per hour. Why is power so important to know? Because the time aspect is very important. Since the human body has the ability to accumulate radiation, all doses that a person “grabbed” for their life remain with him. As a result, the norm “for life” is somewhere in the range of 100-700 mSv (that is, no more than 0.1-0.7 Sievert). Such a difference in the range is caused by the diversity of people and their habitats, for example, in the mountains the level of radiation is higher than in the lowlands, but the highlanders are more adapted to this. This implies ‘a time factor‘ as a feature of accounting for radiation doses for people. That is, you can get a high dose for a short time and it will not be as dangerous as a small dose that is taken for a very long time. Therefore, it is very important to take into account the dose in conjunction with time.
Now, using a unit such as Sievert (Sv) and Sievert per hour (Svh), we can proceed to comparative estimates.
Remember: 1 Sv = 1000 mSv = 1,000,000 µSv
So, right away for assessment, understanding and matching: the level of radiation that is considered safe is up to 0.5 µSv per hour. Above is considered as dangerous. Up to 0.2 µSv per hour – this is the safest level of external exposure to the human body, it usually fits into the framework of the natural radiation background.
For clarity, we will estimate everything in micro Sievert (mSv):
safe dose – 0,0005 mSv per hour;
a safe dose for life expectancy is 100-700 mSv per life (if per hour 0.0005 mSv, then in a year it will be 4.38 mSv, for 75 years it equals 328 mSv);
fluorography, chest x-ray, dental (dental) x-ray, despite the power are very short-lived. For one session a dose of 0.15-0.4 mSv is obtained. That is not enough – one twentieth / one thirtieth of the annual norm. That is why it is not recommended to do these procedures too often;
flight in an airplane at an altitude of 10km. within an hour – 0.005-0.020 mSv. (if about 18 days to fly continuously on an airplane – an annual dose is provided);
natural background (on average) for the year accounts for 1.5-2 mSv. For a year this is not that much but this is effect there is “always and everywhere”, and avoiding it is impossible.
That is, in everyday life, if you “collect” all the doses, both natural and “medical”, it is easy to meet the “lifetime norm”.
Now let’s provide dose limits in extreme situations with the potential consequences:
– a single dose of 200 mSv – a potentially dangerous and health-critical dose;
– a single dose of 500-1000 mSv causes a feeling of fatigue, moderate changes in the composition of the blood are observed. In the future oncological diseases occur (cancer of the blood, skin, thyroid gland, etc.);
– more than 1000 mSv (1 Sievert) – the appearance of radiation sickness is guaranteed;
– 1000-1500 mSv – pronounced somatic effects (nausea, vomiting), impaired performance, there are various forms of acute radiation sickness;
– 1500-2500 mSv – leukopenia (decrease in the number of leukocytes). In 30-50% of cases, vomiting may occur in the first day after exposure. At doses greater than 2000 mSv – a high risk of death;
– 2500-4000 mSv – radiation sickness of moderate severity occurs. In all irradiated patients, nausea and vomiting are observed on the first day after irradiation, the leukocyte count sharply decreases and subcutaneous hemorrhages appear. Such doses – cause significant, irreparable damage to health, alopecia and bleeding (leukemia). For treatment – bone marrow transplantation and maintenance in a sterile box are required;
– 4000-7000 mSv – a severe form of radiation sickness develops and a high probability of mortality.
– over 7000 mSv is an extremely severe form of acute radiation sickness. White blood cells completely disappear in the blood. Multiple subcutaneous hemorrhages appear. Mortality is of 100%. The cause of death is most often infectious diseases and hemorrhages;
– 10000 mSv (10 Sievert) – death within 2-3 weeks;
– 15000 mSv – 1 – 5 days before the inevitable death.

In what cases can such radiation levels be obtained?

Only in extreme situations (nuclear explosion, accident at a nuclear power plant, close interaction with radioactive substances). For example recent researches by scientists have determined what dose people received in Hiroshima in the area of the explosion (a ball burst in the air) – about 9,500 mSv (9.5 Sievert). After the explosion at a nuclear power plant in Fukushima at a distance of 20km. radiation was about 0.161 mSv (almost 1000 times higher than normal).
During the explosion in Chernobyl (Ukraine, 1986 year) near the station, the radiation power reached several thousand mSv per hour. About 400 times more radioactive substances were thrown out than during the explosion of the atomic bomb “Little boy”, which destroyed Hiroshima. Today in Pripyat city the radioactive background exceeds the norm and for permanent residence it will be impossible for more than 20,000 years (contamination with radioactive releases with a long half-life)!
How to protect yourself?
There are three main protection techniques: time protection, distance protection, and shielding. That is, the less you are in the radiation area and the further you are from the radiation source, the lower the radiation dose. In any case, in order to understand the situation and the degree of its seriousness, it is necessary to know the numerical indicators of radiation at the location and to record (the sum) of that dose obtained in proportion to the time of existing there. The Personal dosimeters device can help you out with that.
Practical advice, techniques for preventing radiation doses above the normative are discussed in the following articles (blogs).