Assessment of the radiation hazard of the use of burnt rocks in road construction

Pankov Vladimir Yur'evich PhD in Geology and Mineralogy Associate Professor; Department of Road and Airfield Construction; Northeastern Federal University 677027, Russia, Republic of Sakha(Yakutia), Yakutsk, ul. Belinsky, 58 pankov1956@gmail.ru Other publications by this author

Galkin Aleksandr Fyodorovich ORCID: 0000-0002-5924-876X Doctor of Technical Science Chief Researcher; P.I. Melnikov Permafrost Institute SB RAS 677010, Russia, Yakutsk, Permafrost str., 36, IMZ SB RAS. Cryolithozone Geothermy Laboratory afgalkin@yandex.ru Other publications by this author

Introduction. Burnt rocks, sometimes called "goreliki" or "gliezhi" - an abbreviation for "naturally burnt clay", are widely used in the construction industry in the main regions where coal and shale deposits are located^[1-6]. They are developed specifically or obtained as a by-product of coal mining. Deposits are usually used as binders and fillers for concrete for various purposes^[7-11], in the manufacture of building blocks and panels^[12-18], in decorative coatings and jewelry ^[19-20], as well as for fillings in the formation of road clothes^[21-26]. The very breadth of the possible application of burnt rocks indicates the diversity of their physico-chemical and mechanical properties. This is explained by the fact that gorenje rocks are thermally altered sedimentary rocks that have arisen as a result of underground coal fires or burning of terranes. The composition and properties of burnt rocks are highly variable and depend on the composition of the source rocks and the degree of their firing. Burnt sand rocks are used in road construction to build the underlying layers and foundations of roads. High-quality aggregates from burnt rocks can be used in all structural layers of highways, including road clothing ^[24,25].

At the same time, many researchers note a number of difficulties when using burnt rocks in construction, one of which is their possible radioactivity.

An analysis of literary sources has shown that insufficient attention is paid to this problem in the scientific community. Basically, researchers focus on simply determining radiation parameters and comparing them with acceptable regulatory values ^[27-33]. Although, in our opinion, many elements of uncertainty affecting the safety of the use of burnt rocks in road construction are embedded in the regulatory documents themselves.

The purpose of the presented research was to assess the objectivity of the environmental safety of the use of burnt rocks in road construction from the point of view of their radioactivity and compliance of current regulatory documents with practical realities.

Radiation safety of personnel, the public and the environment is considered to be ensured if the basic principles of radiation safety (justification, optimization, rationing) and the requirements of radiation protection established by Federal Law No. 3-FZ dated 09.01.1996 "On Radiation Safety of the Population", standards RB-99/2009 and current sanitary regulations are observed. Federal Law No. 3-FZ of January 9, 1996 "On Radiation Safety of the Population" (Date of revision: March 18, 2023) defines the legal basis for ensuring radiation safety of the population in order to protect their health. Radiation safety of the population is defined as the state of protection of present and future generations of people from the effects of ionizing radiation harmful to their health. The Law establishes both a list of measures to ensure radiation safety and basic hygiene standards (permissible dose limits) for exposure in the Russian Federation as a result of the use of ionizing radiation sources.

The law also declares the right of citizens to radiation safety and to receive objective information about the radiation situation in accordance with sanitary standards and regulations. The current standards are SanPiN 2.6.1.2523-09 "Radiation Safety Standards (NRB-99/2009)", which were approved by the Decree of the Chief State Sanitary Doctor of the Russian Federation dated 07.07.2009 N47 SanPiN dated 07.07.2009 N2.6.1.2523-09.(Hereinafter referred to as "Norms"). Based on these regulatory documents, we will analyze the possible negative impact of burnt rocks on humans and the environment when used in road construction.

The main radioactive isotopes found in Earth's rocks and, consequently, building materials, which include burnt rocks, are potassium-40, rubidium-87 and members of the two main radioactive families originating from uranium-238 and thorium-232, respectively. The family here refers to a number of intermediate decomposition products of these two elements. From the point of view of radioactive safety for humans, in addition to the elements mentioned above, caesium-137 and strontium-90 are also of interest. While maintaining chemical properties similar to those of a stable isotope, these elements can participate in the formation of tissues of living organisms, replacing calcium in them and, thus, become almost eternal internal sources of human radiation.

The ratio of different types of radiation in rocks depends on the ratio of radioactive isotopes in them. In the radioactive families of uranium and thorium, the transformation of one nuclide into another occurs in the vast majority of transitions as a result of alpha or beta decay. Many of the decay acts are accompanied by gamma radiation. Moreover, the most powerful pulse of gamma radiation occurs during the isomeric transition of nuclei. However, in all known series, a similar isomeric transition is observed only for Pa-234 in the uranium-238-lead-206 series.

Potassium-40 is not included in the series discussed above. It is a primary radionuclide formed simultaneously with other elements of the Earth. It decays in two ways: 88% of potassium-40 atoms are converted into stable calcium-40 as a result of beta decay (beta radiation); 12% are converted into metastable argon-40 by K-capture, which, after emitting a gamma quantum (gamma radiation), passes into the ground state.

The above data indicate that in natural processes, the total alpha and beta radiation should significantly exceed the number of gamma quanta. Moreover, this difference is also increased due to the phenomena of internal conversion, when gamma quanta (gamma radiation) are absorbed by the electron shells of nuclei, which release excess energy either in the form of characteristic X-ray radiation or in the form of electrons (beta radiation).

It is known that burnt rocks may contain increased concentrations of radionuclides of the family of uranium-238, thorium-232, and potassium-40. The level of concentration of these elements in different areas of the deposits varies greatly, due to a complex of geological, structural, hydrogeological, physical, chemical, hydrological and other factors. As a result of the peculiarities of geological processes, the concentration of these elements in different areas of the deposits is very heterogeneous. There may be areas with extremely high concentrations of radionuclides comparable to concentrations in uranium ores. At the same time, there are volumes of rocks in which the content of radionuclides does not exceed the standard contents for the most common types of geological rocks. The heterogeneity of the distribution of radionuclides in gorenje rocks is regulated primarily by the dynamics of the redistribution of gaseous products of coal combustion and, accordingly, the textural and structural features of the rocks overlying the burning coals.. The experience of previous studies and general geological patterns suggest that the scale of heterogeneity in the concentration of radioactive elements in deposits can range from the first tens of meters to several tens of kilometers.

Thus, in the most general terms, burnt rocks can pose a radiological danger to humans at the following main stages:

• At the stage of preparation and development of a quarry or an underground mine.

At this stage, the main danger is dust generated as a result of work. The radionuclides contained in dust particles are a source of ionizing radiation that affects the entire body, the skin, the lenses of the eyes and the lungs, into which dust particles penetrate during respiration.

In accordance with the Norms, when calculating the effect of corpuscular ionizing radiation (alpha and beta), the base area of the human body for calculating their effect on the human body is 300 square meters. cm, i.e., in fact, the area of open areas of the face and hands. In the rest of the body area, it is assumed that the corpuscular radiation is absorbed by clothing. If the clothes are indeed dustproof, this conclusion is valid. In air under normal conditions (760 mmHg), the path length (penetration), for example, of alpha particles formed during the decay of uranium-238, is 2.64 cm (22%) and 2.685 cm (78%), for thorium-232 – 2.436 cm (20%) and 2.503 cm (80%), for radium-226 – 3.083 cm (5.7%) and 3.274 cm (94.3%), radon-222 – 4.036 cm. The path length of alpha particles in the air largely depends on their energy. However, it is clear from the data provided that this radiation, which is destructive in its ionizing ability, is practically safe if there is no direct contact with biological tissues of the human body. At the same time, it becomes obvious that this radiation poses the greatest danger when dust particles contaminated with radionuclides enter the upper respiratory tract and lungs of humans, where the ionizing ability of corpuscular radiation is manifested to the maximum and in the most unfavorable contact for biological tissues.

The Norms also provide for standards on the conditions and the possibility of radionuclides entering the bloodstream and, accordingly, the internal organs of a person through the lungs and digestive tract. The question of the form of radionuclides in burnt rocks is currently completely unexplored. Depending on the structural state and chemical composition of rocks subjected to the combustion of coal seams to gorenje and enrichment with radionuclides, and the chemical properties of radioisotopes, the latter can form chemical compounds that are easily soluble in the acidic environment of the gastric tract, for example carbonates, oxides, hydroxides, fluorides. At the same time, silicate glasses and minerals can form, which can be practically insoluble even in the digestive tract, not to mention the lungs. Naturally, the question of the form of radioisotopes entering burnt rocks, and consequently the possibility of their absorption by living tissues, requires very complex and expensive studies over a long period of time and at various sites. In this regard, we will not consider this problem in the future.

In accordance with the current regulations on this item, several problems arise, the main of which are:

- clarifying the issue of the actual content of various radionuclides in the studied burnt rocks and, accordingly, the degree of their radiological effect on humans;

- assignment of quarry or mining workers to a certain regulatory category of exposed persons (personnel or the public).

As for the second question, the answer is obvious – due to the fact that the development of burnt rocks is included in the scope of their production activities, the workers belong to the personnel of Group A. This is not an idle question, because depending on the category of people exposed, according to the Norms, the limits of effective and equivalent doses vary significantly.

2. At the stage of shipment and transportation of deposits.

At these stages, all the specialists involved in the work also belong to the staff. Depending on the type of work, such as the tightness of machine cabins or loading mechanisms, personnel may belong to both Group A and group B.

3. At the stage of career development, all employees belong to group A.

At the stage of processing raw materials (crushing into fractions, sieving into fractions, obtaining marketable products, etc.), workers belong to group A.

4. At the stage of highway construction (filling of the earthbed, laying of pavement or thermal insulation layers, production of asphalt and cement concrete).

All workers involved in technological processes related to the construction of highways belong to the staff (Group A).

5. At the stage of road operation.

At this stage, absolutely all people passing or driving along the road are exposed to ionizing radiation emanating from dust particles. At the same time, this effect is outside the scope of their production activities and, accordingly, the limits of effective and equivalent doses for them correspond to those for the population.

At all stages, ionizing radiation, when exposed to the human body, can cause two types of effects that are classified as diseases in clinical medicine: deterministic (calculated) threshold effects (radiation sickness, radiation dermatitis, radiation cataracts, radiation infertility, fetal malformations, etc.) and stochastic (probabilistic) non-threshold effects (malignant tumors, leukemias. Hereditary diseases). The likelihood of such diseases depends on the effect of a certain type of radiation on a specific human tissue over time. Therefore, the Standards provide for certain coefficients that take into account the sensitivity of various organs and tissues to radiation (W(T)).

For example, for gamma radiation, the coefficient R is 1. For beta radiation - 1, and for alpha radiation - 20. Thus, alpha radiation induces biological effects twenty times more dangerous than gamma and beta radiation.

At the same time, the sensitivity of organs and tissues of the body to the occurrence of stochastic effects of radiation is maximal for glands, W(T) of which is 0.2. The multiplier of the equivalent dose for the lungs is 0.12, and the skin is 0.01.

The above coefficients are used to calculate the effective and equivalent radiation doses, which are one of the main controlled parameters of the Standards.

The effective dose is a value used as a measure of the risk of individual effects of radiation to the entire human body and its individual organs and tissues, taking into account their radiosensitivity. It is the sum of the products of the equivalent dose in organs and tissues by the corresponding weighting coefficients (W(T)). The radiation dose is measured by a special unit – sievert (Sv).

Calculations on radiation safety and measures to limit exposure to the population may not be carried out if the individual annual effective dose does not exceed 10 mSv, and the collective effective annual dose does not exceed 1 person. Or when, with a collective dose of more than 1 person, the evaluation based on the optimization principle shows the inexpediency of reducing the collective dose.

However, in order to determine the expected annual effective and equivalent doses, calculations are necessary in any case. Because of this, the Regulations specify that such calculations should be carried out at the design stage and taking into account all radiation sources.

Considering that several hundred different radioactive isotopes are currently known (at least, more than 300 of their varieties are discussed only in the Norms), before calculating the expected radiation hazard of certain rocks and the possibility of their influence not only on the radiation safety of an area or object, but also directly on human health, it is necessary to determine which radioisotopes They should be included in the research circle. For example, for the burnt rocks of the Kunkyu quarry (Yakutia), it is necessary to study in detail such elements as uranium-238, uranium-234, thorium-230, radium-226, radon-222, thorium-232 and potassium-40 (in relation to uranium and thorium, we recall that in chemical studies isotopes lead to itself as a single element). After determining the range of elements, the necessary analytical work is carried out, including not only the determination of the chemical composition of rocks and the content of trace elements in them, but primarily the determination of the specific activity of rocks for all three types of radioactive radiation, and preliminary calculations are carried out.

When determining the expected effective and equivalent doses, calculations are performed in accordance with the requirements of the Standards, based on the specific activities obtained through the absorbed dose. At the same time, at the initial stages of calculations, intermediate parameters should be determined that characterize the effect of ionizing radiation on individual organs and tissues (lungs, skin, lens, etc.) and separately for each type of radiation – alpha, beta and gamma. If their values exceed the permissible minimum doses, i.e. this research object is subject to the Norms according to their level, then it is necessary to make more in-depth calculations.

First of all, it is necessary to determine whether the potential exposure of the team is justified. The potential exposure of the team is calculated using a relatively complex probabilistic formula. The calculation takes into account:

- the average reduction in the activity of a full-fledged life as a result of the occurrence of stochastic effects (diseases), equal to 15 years;

- the average reduction in the duration of a full-fledged life as a result of severe consequences from deterministic effects (diseases), equal to 45 years;

- the monetary equivalent of the loss of 1 year of life of the population;

- income from production;

- the cost of basic production, except for damage from protection;

- damage from protection.

For each category of exposed persons, the value of the permissible level of radiation exposure for a given exposure pathway is determined in such a way that, with such a level of exposure to only one given exposure factor during the year, the dose is equal to the corresponding annual limit averaged over five years. The values of permissible levels for all exposure routes are determined for standard conditions, which are characterized by the following parameters: the volume of inhaled air with which the radionuclide enters the body throughout the year; the time of exposure during the calendar year; the mass of drinking water with which the radionuclide enters the body during the calendar year; the geometry of external exposure to ionizing radiation fluxes.

The Standards set standard values for personnel parameters: volume of inhaled air – 2400 cubic meters. m per year, the exposure time is 1,700 hours per year.

For the population, the Standards set the following standard values of parameters for calculations: exposure time – 8,800 hours per year, weight of drinking water – 730 kg per year for adults. The annual volume of inhaled air is set depending on age:

An analysis of the guidelines for methodological calculations shows that they do not specify some significant problems associated with the application of these guidelines. In particular, analytical issues are ignored. A wide variety of radionuclides can come with air and water and in a wide variety of states: in the form of gas (radon-222), in the form of aerosols (almost all radionuclides, compounds of which are soluble in water), in the form of solutions, in the form of dust insoluble particles. For most of the listed types of income in conditions, for example, Yakutia, there are seasonal peaks and troughs. At the same time, each type of intake has its own methodological and analytical recommendations and methods for sampling and analyzing the content of radionuclides in them or determining the level of their radioactivity. This is not to mention the fact that when determining the concentrations of many radionuclides (groups of radionuclides) or determining their specific activity, separate methods adapted only for them are required.

Some general principles and values of radiation exposure levels and requirements for monitoring compliance with Standards have been discussed above. At the same time, within the framework of this article, in order to achieve the goal, it is necessary to consider another important issue related to the limitation of natural radiation.

The effective specific activity (Aeff) of natural radionuclides in building materials (crushed stone, gravel, sand, rubble and sawn stone, cement and brick raw materials, etc.) extracted from their deposits or being a by-product of industry, as well as industrial waste used for the manufacture of building materials (ash, slag, etc.) is not must exceed the value calculated by the formula:

Aeff = A(Ra)+1.3A(Th)+0.09A(K)

Where: A(Ra) and A(Th) are the specific activities of radium-226 and thorium-232, which are in equilibrium with the rest of the members of the uranium and thorium series, and (K) is the specific activity of potassium-40, Bq/kg

Currently, the following classification is in effect for the use of materials in construction, which has five ranks.

1). For materials used in residential and public buildings under construction and reconstruction (Class I): Aeff = A(Ra)+1.3A(Th)+0.09A(K)<370 Bq/kg

2). For materials used in road construction within the territory of settlements and areas of prospective development, as well as during the construction of industrial facilities (Class II): Aeff<740 Bq/kg;

3). For materials used in road construction outside populated areas (Class III): Aeff<1500 Bq/kg

4). At 1500 Bq/kg<Aeff

5). When the Aeff is >4000 Bq/kg, the materials are prohibited from being used in the construction industry.

Despite the apparent simplicity of this formula, it also contains certain analytical problems and, to put it mildly, inconsistencies.

One of the analytical problems is the relatively difficult question, at least for regional SES, whether the studied radionuclides of the uranium and thorium family are in equilibrium. With respect to most natural building materials, with the exception of burnt rocks and some rock areas drained by surface waters in the zone of redox potential change, the issue of achieving radioactive equilibrium is not fundamental. There is no radioactive equilibrium in industrial waste used for the manufacture of building materials, especially in the ashes obtained from coal combustion. However, unambiguous evidence of these calculations can only be obtained as a result of complex analytical work.

The “absurdities” of this methodological formula are represented by two aspects. The first is reflected in the phrase “... radium-226 and thorium-232, which are in equilibrium with the rest of the members of the uranium and thorium series.” Radium-226 is indeed a member of the uranium family. Considering that, under the condition of radioactive equilibrium, one radium atom coexists with about 33600000 uranium atoms, it becomes unclear why radium is included in the formula, and not the ancestor of the uranium family, uranium–238. In our opinion, this is a multifaceted problem, in which analytical and political issues play an important role.

The second “absurdity" is related to potassium-40. The norms stipulate two factors:

1. Ionizing radiation in natural materials associated with potassium-40 is not taken into account.

It is believed that the content of radionuclide in natural materials corresponds to natural ones, i.e. it forms a natural background that cannot harm a certain group of people living in a particular area. Although, given today's economic relations, the movement of building materials over long distances often leads to rocks with a high content of potassium-40, such as granites, entering regions where such rocks were absent, which leads to an increase in the radioactive background. For example, a similar situation is relevant for the city of Yakutsk, where granite chips or granite facing slabs from the regions of the northeast and south of Yakutia are used for urban planning. An example is the monument to V.I. Lenin on the square of the same name in the city center. The granites of this monument have an activity of more than 40 microrentgens/hour with a norm of 20 microrentgens/hour (Yakutsk Evening, No. 15 (346), April 20, 2001, p. 8). Perhaps this is exactly the case provided for by the Norms, but in the absence of monitoring of potassium-40 activity in Yakutia almost any figures for individual regions lose their meaning.

2. All types of ionizing radiation are taken into account when conducting radiation safety measures.

In the practice of determining the specific activity of regional SES, when calculating according to the presented formula, only gamma radiation data on potassium-40 is given. It was already mentioned earlier that only 12% of potassium-40 atoms decay with the release of a gamma quantum. The decay of 88% potassium-40 nuclide is accompanied by the release of beta radiation. Thus, the practice of SES does not take into account 88% of the negative effects on the human body of the radioisotope potassium-40. In our opinion, this is primarily an analytical problem caused by the poor availability of specialized analytical instruments in regional SES.

As an example, let's consider a radiological study of the burnt rocks of the Kunkyui quarry, located 30 km from Yakutsk. Sampling for research was carried out from two locations – directly from the embankment of the road surface of the highway and the burnt rock transshipment areas directly in the Kungyu quarry. A fraction of less than 1 cm was selected for the analysis. The sample volume is 1.5-2 liters. Burnt quarry rocks have a dark color. These are mostly different shades of red, burgundy, and brown. If oxidized carbons or soot are present in the lens deposits, they turn black. A significant amount of crushed stone is observed in the bulk of the goreliki, the fragments of which have varying degrees of calcination.

Analytical work was carried out only in the testing laboratory Center of the Republican Center for State Sanitary and Epidemiological Supervision No. GSEN, RU.TSOA 097 of the Committee for Sanitary and Epidemiological Supervision under the Government of the Republic of Sakha (Yakutia). The results of gammaspectrometric studies of some burnt rock samples are given in the table.

Table.

Specific effective activity of burnt rocks of the Kungyu quarry

according to the CES RS(Ya)

In accordance with the data in the table and on the basis of the “Radiation Safety Standards” of the SES, the following conclusion was made: “The rock samples presented do not exceed 370 Bq/kg in terms of specific effective activity, belong to the 1st class of application and, according to hygienic indicators, can be used for any type of construction, without limitation.”

Without going into details of various rules and regulations, an independent expert examination should first answer the question of the actual radiotoxicity of a given object or breed. At the same time, one should not limit oneself to GOST standards, but use all available methods and equipment to clarify this issue. Using the center's data, as well as analytical materials from previous years, this task can be partially solved. First, we have the specific gamma activity of potassium-40. For the GB-5 sample, for example, it is 441 becquerels per kilogram of rock. One becquerel is equal to one decay per second. This means that 441 disintegrations occur in one kilogram of this rock sample. Each decay is accompanied by the emission of one gamma-ray quantum with an energy of 1.46 Mev, which is recorded by analytical equipment. However, as mentioned above, only 12% of potassium-40 atoms decay along this path, and 88% of isotope atoms form stable calcium-40 as a result of beta decay and emission of beta particles with an energy of 1.36 Mev. Accordingly, the specific beta activity of this sample for potassium-40 should be 3234 becquerels per kilogram of rock. The penetrating power of beta radiation is low and only a surface layer of crushed stone with a thickness of less than 1 mm can pose a danger to humans (the radiation from the inner parts is extinguished by the stone itself) and in direct contact with exposed areas of the body. Given this, it would be possible not to take into account the effects of beta radiation on the human body, which is actually done by the Centers of Sanitary and Epidemiological Surveillance, if not for the following circumstances:

1. Burnt rocks are mined and transported before becoming a building material. These production processes are accompanied by increased dust generation.

2. Burnt rocks are used for filling the road surface. The operation of the road is accompanied by increased dust emission.

Thus, during mining, transportation, dumping of burnt rocks and road operation, the released dust comes into direct contact not only with the surface areas of the body, but also with the internal organs of a person, primarily with the respiratory organs. It is in this interaction that the destructive power of beta radiation begins to manifest itself, which is not provided for by any norms, rules and GOST standards. To date, without conducting special studies, it is impossible to assess the degree of exposure to beta radiation through dust contamination, but there is no doubt that it exists.

Under certain assumptions, using the methodology of S. Kullander and B. Larsen, described in the book “Life after Chernobyl. A view from Sweden” (Moscow, Energoatomizdat, 1991), based on available data on potassium-40, for example, it is possible to approximately calculate the equivalent dose for one person engaged in filling the roadway with burnt rocks from the Kungyu quarry.

The calculations performed show that for the GB-5 sample, the total specific gamma and beta activity are 3675 Bq/kg (441 Bq/kg is gamma decay and 3234 Bq/kg is beta decay). It follows from the table that 1.459 Mev of energy is released during gamma decay alone, and 1.325 Mev is released during beta decay. It follows that in one second, 643+4285=4928 Mev of energy is released from one kilogram of rock. Since 1 ev corresponds to 1.6 x 10-19 joules, we can calculate that 4,928,000,000 ev equals 7,885 x 10-10 joules in one second.

Let's assume that the filling of a roadbed from burnt rocks in the summer lasts for 90 days. Hence, with a working day of 6 hours, the total working time will be 540 hours or 1944,000 seconds. Our main assumption is that there is about 1 gram of dust in the upper respiratory tract and lungs of one person during this time. One gram of burnt rock dust of the GB-5 sample will release 7,885 × 10-13 Joules of energy in one second. For 1944,000 seconds, respectively, 1.5 33x10-6 Joules of energy. Let's also assume, although this is a rough rounding, that of this energy, only beta decay energy (88%) is absorbed by the respiratory organs. Then it turns out that through the respiratory organs for the entire period we have adopted, the body will receive 1.349 × 106 joules of ionizing energy. Now it remains to calculate the absorbed dose in gray, which is equal to the energy absorbed per kilogram of body weight. Given the penetrating power of beta radiation, it is clear that it will be completely absorbed only by the upper respiratory tract and lungs, the total average mass of which is assumed to be 7 kg. Then the absorbed dose will be 0.193x10-6 Grams. Thus, with all the rough assumptions made, and only for potassium-40, the employee will receive an equivalent dose of 0.2 mSv.

It follows from the above calculations that, taking into account the corrections for potassium-40 alone, the Aeff for the GB-5 sample will be 347.1 Bq/kg. Accordingly, this sample is already at the limit of the tolerance of building materials to Class 1. GB samples- 1, 2, 10, 11, 13 they generally fall into the construction materials of the II class.

It should be borne in mind that, on the one hand, the effects of ionizing radiation on the skin, lens of the eye, esophagus, etc., and, on the other hand, the effects of ionizing radiation from elements of the uranium-238 and thorium-232 family are not taken into account.

The table shows, among others, data on the determination of activity for caesium-137 and strontium-90. These are synthetic isotopes produced either by reactions of uranium and plutonium with slow neutrons, or as a result of the explosion of atomic bombs. In terms of radiotoxicity, cesium-137 is moderately dangerous. It accumulates in cereal plants. Strontium-90 is more dangerous because of its chemical similarity to calcium, which it replaces in human bone tissue, creating constant additional radiation to the bone tissue and bone marrow itself - the so–called “strontium hazard". Based on the analytical data, it is safe to say that there is no contamination of the studied rocks with these elements.

Thorium-232 is one of the primary isotopes. It forms a family of radioactive isotopes in the series thorium-232 – lead-208. According to the table, gamma activity of thorium-232 was recorded in the samples. Upon decomposition, thorium-232 is converted to radium-228. The nature of the radiation is alpha, beta and gamma. Alpha radiation has an energy of about 3.9 Mev, beta radiation has an energy of 0.055 and 0.070 Mev, and the gamma quantum has an energy of 0.075 Mev. Based on this, it can be concluded that one decay is accompanied by the release of one alpha particle, one electron and one gamma quantum. Accordingly, when analyzing the data shown in the table, it is necessary to take into account corpuscular radiation and the degree of its effect on the body (And the effect in the table). However, the lack of equipment, standards, techniques, standards and GOST standards, unfortunately, does not allow the Gossanepidnadzor Center to give a more objective picture of the actual radiotoxicity of an element.

It should be noted that, in accordance with the Norms, the use of formulas for determining the suitability of building materials for radiation safety is possible only under the condition of an equilibrium state of radioactive elements. Considering that burnt rocks show obvious signs of disequilibrium, it can be concluded that this formula is inapplicable for burnt rocks without conducting special studies.

The above facts clearly prove that studying the radiation safety of burnt rocks for the possibility of their use as building materials without determining the total corpuscular radiation is not only impossible, but also dangerous, since it gives an inadequate, false picture of the real radiation situation. It is necessary to apply a set of measures to study the radioactive safety of burnt rocks at the stage of project development. The package of measures should include, at a minimum, the study of gamma activity, the determination of total corpuscular activity for a number of elements identified by us. To make calculations not only on the applicability of burnt rocks in construction, but also on the level of exposure of ionizing radiation associated with them to the human body, depending on the technological processes of preparation and processing of deposits.

Conclusion. Varieties of burnt rocks often exceed the characteristics of traditional building materials in their physical and mechanical characteristics. They can be successfully used as fillers of concrete and asphalt concrete, serve as the main material for transitional road surfaces in the form of crushed stone, have excellent thermal insulation properties, and can be used as soil stabilizers for the roadbed of cryolith zones. The use of deposits in the construction industry is especially relevant for regions with a poorly developed construction industry in terms of the production of building materials and complex logistics for their delivery. First of all, such regions include the Arctic and Subarctic zones of the Russian Federation, as well as most of Siberia. It is in these territories that the largest coal basins are located, each of which is accompanied by a number of industrial deposits of burnt rocks. Certain varieties of burnt rocks pose a significant threat to human health. Their use for various types of construction should be carried out using a set of measures to limit exposure to personnel and the public.

The legislation of the Russian Federation guarantees citizens the legal framework and the right to ensure their radiation protection. The Russian Ministry of Health has developed Standards and requirements for protecting the population from various types of radiation and monitoring the level of exposure. At the same time, even the most general analysis of the situation of radiation protection of the population when using deposits in the road construction field reveals a number of shortcomings caused primarily by the fact that, despite the full coverage of various conditions of exposure to the population, the calculated part has not yet been fully developed. At least in calculating the doses of deterministic effects of radiation exposure, the use of probabilistic functions is allowed. The Standards do not take into account the availability of analytical equipment remote from the center of regional SES, which is necessary for a full-fledged assessment of the radiation hazard of using burnt rocks in road construction. In this regard, before using the burnt rocks of a particular deposit, it is advisable for construction organizations to use the services of special scientific laboratories with appropriate methodological support and modern equipment for an objective assessment of radiation safety.