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Abstract

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Introduction

Increase of level of natural environment radioactivity is conditioned, foremost, by development of atomic energy, active use of sources of ionizing radiation in medicine and industry, and also by radionuclides in technique, scientific and war researches. The increase of ruinous action of ultraviolet rays is caused by anthropogenic destruction of the atmosphere ozone layer.

The radioactive pollution of environment has attained global catastrophic scales. It happens as a result of nuclear tests, accidents on the objects of atomic energy, during booty and processing of nuclear fuel etc. The ecological consequences of the greatest technogene catastrophes of Chernobyl nuclear power plant and Fukushima became the severest for the world ecosystems and especially for the human health. So, humanity must learn how to prevent and counteract to negative influence of radiation on ecosystems today [1].

1.Radioactive decay

Majority of nuclear kernels unstably. Sooner or later they spontaneously (or as the physicists speaks, it is spontaneous) break up to smaller kernels and elementary particles which it is accepted to call products of disintegration or affiliated elements. Breaking-up particles can be called initial materials or parents. To us well familiar chemicals (iron, oxygen, calcium, etc.) is available for all at least one stable isotope. That fact that these substances to us are well-known, testifies to their stability – means, they live long enough that in significant amounts to collect naturally, without breaking up to components. But each of natural elements has also unstable isotopes – their kernels can be received in the course of nuclear reactions, but long they don't live, as quickly break up [2].

At beta disintegration (β-) electrons with energy in wide (from zero to a maximum) a range are let out. Losing an electron, the atom kernel at invariable mass number gains the following (higher) atomic number. Many isotopes break up with emission of positrons (β+) or by electron capture (е).

β-disintegration and capture of electrons are usually accompanied γ-by radiation (at capture of electrons characteristic x-ray radiation is observed). α-radiation is characteristic for disintegration of the heaviest nuclides, in particular for natural isotopes of uranium, radium and radon thorium and artificially received plutonium and other. At α-disintegration atomic number decreases on 2, and mass number – by 4 units. This radiation is usually accompanied by emission γ-quanta [3].

α-radiation represents a stream α-the particles extending with initial speed about 20 thousand km/s. Their ionizing ability is huge, and as certain energy is spent for each act of ionization, their penetration is insignificant: the length of run in air makes 3—11 cm, and in liquid and firm environments – the 100-th shares of millimeter. The leaf of dense paper completely detains them.

As α-radiation has the greatest ionizing, but the smallest penetration, external radiation α-particles almost harmlessly, but their hit in an organism very dangerously [4].

2. The basic unit of measurement of radiation

The main physical size which characterizes a radioactive source, this number of disintegrations occurring in it in unit of time. Such size was called activity. Activity of this or that substance, for example, a radioactive isotope, is defined by quantity of the atoms which are breaking up in unit of time and, therefore, number of radioactive particles let out by substance in direct ratio to its activity.

As activity unit in the International system of SI the Becquerel (Bq) is chosen. Activity in 1 Bq corresponds to one disintegration in a second. However in practical dosimetry and radiating physics other unit – curie (Ki, is designated by Ci) is more often used. The curie in 37 billion times more one Becquerel (1 Ki = 3,7 1010 Bq), that is corresponds to 37 billion radioactive disintegrations a second that corresponds to number of the disintegrations occurring in one gram of radium-226 – historically the first substance in which laws of radioactive disintegration were studied. As activity of one gram of pure radium is close to 1 Ki, it often express in grams. In it (and only in it) a case the unit of mass of substance possesses individual activity.

Thanks to disintegration the quantity of radioactive atoms in initial mass of substance decreases eventually. Respectively decreases, and activity. This reduction of activity submits to the exponential law:

Ct = C0 exp (- [0,693/T]t), (2.1)

where Ct – activity of substance after the lapse of t time, С0 – activity during the initial moment.

Apparently from a formula (2.1) describing disintegration, the size T serves as the most important characteristic of radioactivity – it shows that time after which activity of substance (or the number of radioactive atoms) decreases twice. This time of T is called as a half-life period [5].

On the VII International congress of radiologists which took place in 1953 in Copenhagen, energy of any kind of the radiation, absorbed in one gram of substance, it was recommended to call the absorbed dose. As unit of the absorbed dose rad (on the first letters of the English phrase radiation absorbed dose, – the absorbed dose of radiation) was chosen.

Rad, as well as curies (1 Ki = 3,7 gigabecquerels, GBq), are so-called stand-alone units, and from the point of view of orthodox adherents of SI system on their use should be imposed a severe ban. However vital practice appeared stronger than formal instructions, and illegal unit of the absorbed dose – rad – is used much more often than the corresponding unit of SI system – Grey (Gr, is designated by Gy).

It is necessary to pay attention to that circumstance that rad (or gray) – unit of purely physical size. In essence, it is the power unit which in any way isn't considering those biological effects which are made by a penetrating radiation at interaction with substance. However that really interests experts in dosimetry and radiating physics, are changes in an organism, arising at radiation of the person. It appeared that weight of all violations strongly differs depending on radiation type.

For simplicity and convenience reasons the biological effects caused by any ionizing agents, it is accepted to compare to impact on a live organism x-ray or gamma radiations. Convenience here consists that for x-ray radiation the set doses and their capacities rather simply turn out (for example, by means of the calibrated x-ray sources), well are reproduced and are reliably measured. All these procedures become much more difficult for other types of radiations. That it was possible to compare influence of the last to biological effects from x-ray and gamma radiations, the so-called equivalent dose which is defined as work of the absorbed dose on some factor depending on a type of radiation is entered [5].

The resulting human equivalent dose is the main criterion for radiobiological risk exposure to any radiation. Note also that some parts of the body (organs, tissues) are more sensitive than others. Therefore, the irradiation dose of organs and tissues should also be taken into account with different coefficients k. This, so- issue-weighted factors, can be found in the relevant tables [6].

3. Radiation situation in the Donetsk region

On the territory of Donetsk region there are 80 enterprises, which maintain ionizing radiation sources. Generally, there are enterprises of coal and metallurgical industry. The huge work about the enterprises and in the organizations maintaining sources of ionizing radiation is carried out by districts of sanitary epidemic posts of radiating hygiene.

In treatment and prophylactic establishments of Donetsk region 723 x-ray offices are maintained, which contains 1064 x-ray devices (data for 2002). For the purpose of doze weight decrease of the personnel and patients, all x-ray devices are obligated for radiation control not less than 1 time for 1,5 years. Systems of radiating safety in all offices operate: the upgraded x-ray devices. Application of individual protection resources is obligatory supervised.

In Donetsk region there are 134 building industry enterprises and 2265 enterprises (for 2006), using industrial wastes, slags etc. work. Radiating safety control of building materials is carried out at all production phases. The measurement of gamma background level in the constructed buildings a final stage of control is. In area it is created and the computer database of the enterprises of building industry is constantly updated.

In 11 sanitary epidemic posts (SEP), there is the necessary equipment for carrying out laboratory control of building materials, foodstuff and objects of environment. Every SEP is provided with dosimetric equipment for daily gamma background measurement and the express control of radiating pollution. Except region SEP, radiating control is carried out by the Mariupol radiological center STAKS and its divisions [3].

According to the current legislation, all foodstuff and the raw materials, areas made in the territory and delivered of other regions, are subject to continuous radiating control. The special attention is payed to the food imported from territories of victims after failure on the Chernobyl Nuclear Power Station [2].

4. Natural background radiation field

In all territory is carried out the radiometric shooting on a system of 2×2 km and 3×3 km in regions of industrial hubs and other part of the territory on a system of 4×4 km. The metric analysis was made by sampling on gamma specter. Generally, about 3 thousand measurements are made.

Works were carried out for the period since 1989 till 1996 inclusive. Measurements were made directly in the field at the same time with selection of geochemical tests.

On the most part of the territory, excepting the east, radiation levels make not more than 20 мcR/hour, on the average 13-15 мcR/hour that is less than maximum permissible level established according to Standards of radiating safety of Ukraine and reaching 30 мcR/hour. There are locations, especially at the south and South to the east of Volnovakha, where levels of radioactivity exceed 20 мcR/hour, and in separate points exceed more than 28 мcR/hour. It is possibly connected with an exodus to a day surface of Archean and Proterozoic crystal breeds the with the raised natural radiating background.

The highest levels of radioactivity are fixed in east part of area. The strip in width in the south to 25 km, in the central – to 50 km, which in a northern part falls out the limits area is allocated. This strip in length to 100 km in the area territory (outside of area it is unknown) settles down in the submeridian direction from the northeast on the southwest, crossing perpendicularly the Main anticline. Radiation levels here make more than 20 мcR/hour, especially in the central part of a strip. Radioactivity levels here reach to 40 мcR/hour and more (50-57 мcR/hour). On the most part of the territory of a strip radiation levels make 25-30 мcR/hour. For strip edges, they gradually decrease and reach background values. It is necessary to note that the increased concentration artificial and a lesser extent ofnatural radionuclides for these levels, is characteristic.

The lowest radiation levels (to 10 мcR/hour) is noted in a northern part dated for sandy breeds of river terraces of the Seversky Donets basin, and also a small location in the northeast Krasnoarmeysk [3].

5. Assessment of radiological safety in the village Donskoye

Capacity exposition dose measurements, described above, aren't carried out by times for small settlements, close to which there is not any large enterprise. The similar situation is characteristic for small settlements of the Volnovakha area, in particular for settlement of city-type Donskoye.

The main city-forming object in Donskoye is the chemical and metallurgical factory. This enterprise treats a metallurgical complex in which territory carrying out radiological control is obligatory. It consists on regular measurement of exposition dose capacity in strictly certain places two times a month. On figure 1, is presented dynamics of capacity change from 2007 for 2012.

Figure 1 – Dynamics of change of exposition dose capacity at the Don chemical and metallurgical factory for 2007-2012

Figure 1 – Dynamics of change of exposition dose capacity at the Don chemical and metallurgical factory for 2007-2012

As appears that, value of capacity fluctuates slightly from 13,9 мcR/hour in 2008 to 16,04 мcR/hour in 2011.

In the same time for a high-grade assessment of a radiological condition, is essential to carry out measurements also in the settlement territory. We carried out measurements of exposition dose capacity, using dosimeter DRG-01T. The received values of capacity of an exposition dose in 15 points on the district were is placed settlement of city-type Donskoye which is presented at figure 2.

Figure 2 – The Schematic map of distribution of exposition dose capacity in settlement of city-type Donskoye

Figure 2 – The Schematic map of distribution of exposition dose capacity in settlement of city-type Donskoye

According to the figure, in the settlement territory the exposition dose capacity, on the average, fluctuates in the same limits, as in the territory of chemical and metallurgical factory, namely within 13-16 мcR/hour. However, as a result of measurements, two points in which values of capacity made 20 and 36 мcR/hour were received. Such excess can be caused by random factors or specifics of territory building that demands further researches.

Findings

By the time of writing this report the master's thesis wasn't finished. The full text of work can be received from the author after December, 2012 when writing request for the address: dasha-tasbash@mail.ru

References

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