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Relevance. A submersible electric motor is the most vulnerable component of an electric centrifugal pumping unit used in in-situ leaching uranium mining. The accuracy of calculating the need for new electric motors directly affects the profitability of the uranium production. Aim. Development of a probabilistic reliability model for a submersible electric motor that provides the calculation of its failure probability for the upcoming period of time and allows estimating with sufficient accuracy the number of motors required to replace the failed ones. Methods. Statistical methods, survival analysis, statistical hypothesis testing. Results and conclusions. The authors conducted a study of three probabilistic reliability models for electric motors of submersible well pumping units used in in-situ leaching uranium mining. As a result of the study, the maximum likelihood estimates of model parameters were determined for each model; the adequacy of the models under study was checked based on nonparametric goodness-of-fit tests. Despite the fact that the test results did not allow excluding any of the considered models, a model based on a mixture of two Weibull distributions was selected as a probabilistic reliability model demonstrating higher consistency with real data, compared to the other models. At the same time, the analysis of the components of the mixture distribution indicated the presence of a group of electric motors with an uncharacteristically low time-to-failure value compared to the average value calculated for the entire set of equipment under study, and made it possible to estimate the share of such motors, which amounted to 8% of the total population. Possible reasons explaining such heterogeneity of data, according to the authors, are hidden manufacturing defects or more severe operating conditions in which some submersible electric motors operate.

Introduction. A considerable amount of conflicting reports creates conditions for concern about the effects of radiation on health. The adequacy of the assessment of problems and responses to these challenges depends on the sources used by a person, his culture and education level, as well as the emotional overtone of this assessment. The aim of the study is to determine dynamic changes in the prevalence and structure of population’s radiation anxiety states under stable social conditions based on a psychological and hygienic assessment. Materials and methods: In order to research and assess the perception of Kropyvnytskyi residents about the degree and prevalence of radiation anxiety states, a survey was conducted on Facebook and Instagram social networks from February to December 2019 using Google Form. For assessment of dynamic changes in radiation anxiety, data from our own studies in 2014 were used [9]. The questionnaire methodology was based on the principles of the previously tested and patented "Methodology for determining radiation anxiety among the population" and the monograph "Radiation anxiety among the population". Three hundred and twenty four residents of Kropyvnytskyi aged 18 to 73 were included in the study, 155 (47.8%) men and 169 (52.2%) women. The average age of the interviewees (Me (LQ; HQ)) was 27 (20; 33) years old. Results. A specific psycho-emotional state is developed and maintained at some level in the residents of cities with nuclear power plants – radiation anxiety, which is manifested by a complex of neuropsychological and somato-physiological disorders against the fear of ionizing radiation sources background. At the same time, such a psychogenic effect may not be related to the degree of actual effects of ionizing radiation on human health. It was determined that in 2019, before the COVID-19 pandemic and Russia's full armed aggression against Ukraine, more than 90% of the surveyed residents of Kropyvnytskyi, regardless of gender and age, were concerned about potential radiation pollution of the environment and foodstuffs, medium level of radiation anxiety was in 34,9%, and high level in 14.8% . Low radiation anxiety was detected in 41.4% of respondents, and in 8.9% it was absent. Conclusions. Over 5 years (from 2014 to 2019), there were noticeable negative changes in the structure of the radiation anxiety states among the surveyed urban residents, namely: the amount of people without signs of radiation anxiety halved (8.9% vs. 16.0%) and respondents with the high level of this psycho-emotional state increased almost four times (14.8% versus 3.9%). The obtained results encourage the authors to future studies of specific radiation anxiety states among the population to clarify their dynamics.

With increasing depth of exploration and process boreholes (at small drilling diameters), the probability of deviation of the borehole path from design trajectory increases many times; i. e. zenith curvature and azimuth deviation of the borehole path occur. Therefore, developing methods for keeping vertical path of the borehole when drilling deeper horizons of ore bodies is a very topical issue. The paper presents the results of developing a new bottom-hole assembly for drilling boreholes in soft rocks using screw casing centralizers, which provide good stabilizing and centering effects to mitigate horizontal departure of the hole axis from the design direction and minimize vertical curvature of the hole path (zenith angle) while maintaining sufficient drill string flexibility. The developed technical solutions provide simplicity of design and ability to adapt to wide range of mining, geological and technological drilling conditions. The feasibility of manufacturing the centralizers by own efforts and the technological feasibility of quick and easy connecting the centralizer with other elements of the bottom-hole assembly have been substantiated. The manufacture efficiency is proved by the use of inexpensive and wear-resistant materials in the centralizer armouring, for which tungsten-cobalt or titanium-cobalt hard-alloy inserts were used. In addition, prevailing volume of borehole drilling in soft rocks allowed using replaceable centering elements, as well as their repair and restoration to increase their service life. The manufactured centralizer has a low production cost due to the design simplicity and the use of inexpensive wearresistant material and will compete in the market of drilling tools and technical devices for drill string stabilization. The economic effect from the introduction of the self-produced centralizers amounted to more than 170,000 tenge per a borehole.

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Purpose. Development of recommendations on the choice of rational type of excavation support and its junctions. Methodology. To develop the recommendations we used the following special and general scientific research methods: analysis of literature, method of critical analysis and synthesis of theoretical studies, system approach; method of economic and mathematical modeling. Findings. We have developed the recommendations on the choice of rational type of excavation support and its junctions for uranium mines of State-Owned Enterprise SKhIDHZK. It takes into account, not only the stability class of rocks and their level of stress state, but also the width of excavation and its operating life. We gave recommendations for the characterization of the roof bolting, sprayed concrete lining and combined support, and presented the examples of calculations of the parameters for different kinds of support in given conditions. Originality. We have determined the dependence of the stability of rocks on their stress state level corresponding to the stability class, affecting the size of mine tunnels and their operating life. Practical value. We have determined the values of the coefficient of structural weakening of the massif. We have suggested the methods for calculating the required length of the anchor; anchor depth of setting into the massif; length the anchor should stand proud from the tunnel wall. We have determined the optimal distance between anchors depending on the section of the anchor, tensile strength of the material of the anchor, and load factor. The method for determining the required thickness of the sprayed concrete lining depending on its tensile strength in uniaxial compression in the case the sprayed concrete lining is separate type of support. When using the combined support (anchor with sprayed concrete, anchor with additional tightening of the metal mesh and the subsequent application of sprayed concrete, anchor with additional welded lattice tightening or metal frame supports) the parameters of each of these types of lining are calculated by the improved method. [ABSTRACT FROM AUTHOR]

Purpose. To justify the geotechnical parameters for preparation mode and schemes of development of hydrogenic uranium deposits in Mongolia by the underground in-situ leaching method. Methods. Physical and mathematical modeling of leachates during in-situ leaching of uranium have been carried out by the finite difference method using software Modflow (Schlumberger WS). The model was verified through comparison with the field data, taking into account hydrogeological conditions of the "Ulzit" deposit in Mongolia and necessary precision of calculations. Engineering and technical foundation of by-layer approach for mining deposits with ore bodies on different depths has been made. Results. A finite-difference model of uranium leaching for the conditions of hydrogenic deposit "Ulzit" in Mongolia has been developed using the special software Modflow. As a result of modeling the parameters of leachate flow have been evaluated; the changes of uranium concentration in mining blocks were reproduced, which enabled estimating the dynamics of its extraction by pumping wells. The by-layer approach for mining separated ore bodies by grouped wells of changing diameters and depth has been justified; it allows keeping the mined out horizons separated. The parameters of the hexagonal pattern for placing wells for deposits of Mongolia have been evaluated using the MathCad software. The financial expenses for mining uranium are estimated on the example of the "Ulzit" deposit. Application of the by-layer approach for preparing separated ore bodies enables saving of up to $ 2.5 million and reducing of up to 62% of the total time to be spent for mining of reserves. The use of sustainable mining cell radius at the location according to the hexagonal pattern of wells at the "Haraat", "Khairkhan", and "Gurvan-Saykhan" deposits allows to save up to $ 0.9 million. Originality. Increasing efficiency of mining uranium deposits of Mongolia through applying the by-layer approach for preparation of separated ore bodies using the wells placed by hexagonal pattern. Practical value.Justification of parameters of hexagonal pattern of wells location in underground leaching of uranium under the conditions of Mongolia deposits accounting for the time variations of uranium concentration in leachates. The method for calculation of geotechnical parameters of mining uranium deposits using in-situ leaching based on modeling of leachate flow in mined out blocks has been modified. A resource- saving way to prepare separate ore bodies combining the wells of different diameters and filter designs has been proposed. [ABSTRACT FROM AUTHOR]

Experience received during work in mines and studies of dynamic behavior of rock pressure shows that the problem of resistance to various forms of rock pressure can be successfully solved under the condition of implementation of recommendations on improvement of efficiency and reliability of rock massif geomechanical state estimation, rock bursts prognosis and prevention at the stages of planning and development of deposits. Therefore, improvement of rock massif geomechanical state and its stability degree estimation efficiency in uranium mines is important and required. Applied method of the research included geomechanical monitoring results analysis, experimental investigations held mines and laboratories, mathematical and physical modeling, and theoretical analysis and generalization of the results. On the basis of data collected in research carried out since 1970 to 2011 and taking into account advanced heading-and-stall methods following results were achieved. Charts of dependency of elastic impact sounds frequency on stress rates taking into account strength margin expressed by ratio of the critical (breaking) load affecting structural element to working stress were designed. It was suggested an empirical dependence of stress value on the frequency of elastic impact sounds - the number of pulses per minute. It was suggested the classification of rock massif stressed state depending on the orientation of maximum stress in relation to mine working and composition of rules and the frequency of observation of the stressed-deformed state of rock massif. The "Regulation of the operational monitoring and prediction of stress-strain state of rocks and ore in the mines "Ingulskaya" and "Smolinskaya" of GP "Vost- GOK" was created. The Regulation concerns methods of operative control and the prognosis of stress-strain state of rocks in mines of GP "VostGOK" up to 1000 m depth for development of uranium deposits by heading-and-stall methods. Criteria of estimation of intensity and mechanisms of mountain pressure behavior depending on the level of stressed state of rocks and their deformation characteristic. [ABSTRACT FROM AUTHOR]

Lixiviating of the mountain mass dumps of uranium mines in Ukraine, as one of initial stages of technology of grouped lixiviating, is the basis of rehabilitation of polluted territories and the source of obtaining additional uranium; it also is the source of building macadam and the source of the tails sent in the book-mark of exhaust volumes of mine space. Technical and economic estimation of the obtained results of laboratory researches and experimental-industrial experiments rotined that at joint application of traditional technologies of processing of ore and grouped lixiviating of concentrate of second radiometry separation of waste dump can help to achieve the substantial decline of unit cost, and thus to engage in working off dumps of gobs and tails of primary radiometry separation, which are unprofitable for traditional technology. The offered technology is developed on the basis of the obtained parameters of laboratory researches and experiments on the grouped lixiviating. [ABSTRACT FROM AUTHOR]