METHODOLOGY FOR RETROSPECTIVE ASSESSMENT OF RADIATION EXPOSURE FROM CARBON-14 RELEASE ON EXAMPLE OF THE BILIBINO NUCLEAR POWER PLANT

E. I. Nazarov

The paper presents a methodological approach to the retrospective assessment of the radiation impact of technogenic carbon-14 from nuclear industry enterprises. Using the example of the Bilibino Nuclear Power Plant, an analysis of the C-14 content in the annual rings of the Cajander larch growing in the vicinity of the plant was performed. The results obtained range from 103.5 to 139.7 pMC (from 233.9 to 315.7 Bq/kg C) and allow to trace the dynamics of C-14 entry into vegetation over the time interval from 1974 to 2022. The largest technogenic contribution to the C-14 content was 6.0 pMC in 2020. Using this data, the values ​​of the annual effective dose to the population from C-14 emissions from the Bilibino NPP were estimated. The maximum annual effective dose was 4.61 µSv in 2020, while it does not exceed the minimum significant dose of 10 µSv/year.

DYNAMICS OF SNOW POLLUTION IN THE AREA OF A COPPER PYRITE DEPOSIT DURING ITS OPEN-MINING

A. N. Medvedev, M. A. Medvedev

The article is devoted to the assessment of snow pollution levels in the area of the Safyanovsky copper pyrite deposit (Sverdlovsk region) during the whole period of its open-pit mining. The assessment was performed based on the data of snow sampling and analysis using the pollutant load (fallout intensity) index on the territory. It was found that, when mining operations were in full development, the impact of quarry dust emissions was concentrated within its sanitary protection zone (SPZ). The maximum dust load in the SPZ did not exceed 175 kg/km2/day, which corresponds to a low pollution level according to the current criteria. Taking into account the regional atmospheric transfer of emissions from industrial enterprises of Rezh city (primarily the Nickel Smelter), the quarry’s contribution to the dust load can be estimated at about 100 kg/km2/day, which corresponds to the lower limit of the low pollution level. Based on the assessment results, it was concluded that for ore quarries with a capacity of about 1,300 thousand tons ore per year, there is no need to include area studies of snow pollution in the environmental monitoring. It is possible to recommend the collection and analysis of point samples near the quarry, waste dumps and at the boundary of the sanitary protection zone for correction environmental protection measures if necessary.

ANALYSIS OF 2 х 2 TABLES. DICHOTOMOUS CORRELATION COEFFICIENT PHI AS A METRIC OF LINEAR RELATIONSHIP OF TWO DICHOTOMOUS VARIABLES

I. E. Subbotina, A. P. Sergeev, A. S. Butorova

2 x 2 tables are used to organize categorized data – data presented in the form of joint observation frequencies that fall into four classes. In this paper, 2 x 2 tables are used to analyze the relationship between two dichotomous variables using the example of the relationship between socio-economic status and the event of premature birth in women in labor. By estimating the dichotomous correlation coefficient Phi, it was shown that socio-economic status and the event of premature birth are negatively related. Two statistics were used to test the null hypothesis of no relationship. The obtained pvalue = 0.0016 allowed to reject this hypothesis at the level of a = 0.05.

SOME METHODS FOR ESTIMATING THE IMPORTANCE OF VARIABLES IN STATISTICS. I. EFFECT SIZE

Е. А. Kabakova, V. G. Panov

One of the important problems of data analysis is to identify those independent variables that have the most significant influence on the resulting variable (response), and to rank these variables in terms of importance. Obviously, this problem is related to, but not reducible to, the crucial task of determining the causal factors that lead to variability in the response. Nevertheless, at least to a first approximation, it can be assumed that variables with a weak importance characteristic should not be considered as causal. The urgency of the problem of determining the most important variables, the development of theoretical methods of statistical analysis and computational capabilities have led to intensive development of this problem. This paper reviews the main methods of statistical analysis of variables importance and their ranking, which can be considered classical.

The first part of the review discusses methods for determining the importance of variables based on the concept of effect size. The main effect size indicators from the r-family (indicators based on measures of the relationship between a given independent variable and the response) and the d-family (indicators based on standardized mean difference) are presented. The application of all measures is illustrated by analyzing a database of metallurgical workers. It is shown that all computed measures yield consistent lists of ranked variables, despite significant differences in the algorithms used to compute the measures. A visual comparison of the results obtained by different methods is presented, as well as a natural way to reduce them to a single ordered list.

A CONCEPTUAL METHODOLOGY OF INTEGRATED ASSESSMENT OF RADON HAZARD OF A BUILDING

I. Yarmoshenko, G. Malinovsky

A conceptual methodology of integrated assessment of radon hazard in buildings is introduced. The objectives of the integrated assessment include identification of radon entry sources, characterization of transport mechanisms and pathways, and determination of factors influencing indoor radon concentration dynamics. The methodology is based on a systems analysis approach that integrates direct measurements with reference and engineering data to provide a comprehensive qualitative and quantitative assessment of the radon hazard. Direct measurements are made of ambient dose equivalent rate, Ra-226 activity concentration in soil, soil air radon concentration, diffusive and advective radon flux density from soil, and atmospheric radon concentration in the area adjacent to the building. Inside the building, measurements include ambient dose equivalent rate, Ra-226 activity concentration in building materials, indoor radon concentrations, and radon concentration in water. Reference data include geological, climatic, and meteorological conditions, as well as technical information on building construction. The results of the system analysis are used to develop a model of radon entry and accumulation in a building. The model of the building is used to analyze current indoor radon exposure conditions, predict future trends, perform retrospective evaluations, and justify measures to reduce indoor radon concentration.

COMPUTATIONAL PHANTOM FOR DOSIMETRY OF FETAL RED BONE MARROW AT 24 WEEKS OF PREGNANCY

P. A. Sharagin, E. I. Tolstyh, E. A. Shishkina

Internal irradiation of the red bone marrow (RBM) is caused by the entry of osteotropic radionuclides into the human body. Some of the most dangerous radionuclides are man-made Sr-89,90, which enter the environment as a result of radiation incidents. These radionuclides were present in the composition of radioactive discharges into the Techa River and are the main source of RBM irradiation for residents of coastal areas. To assess doses from osteotropic radionuclides, computational phantoms are used that imitate the geometry of bone tissue, within which the transfer of radiation is imitated. The result of dosimetric modeling is the conversion factors (DF) from the activity of the incorporated radionuclide to the dose rate of irradiation of the RBM. Modern computational phantoms are based on postmortem CT and microCT images of skeletal bones. An alternative method of stochastic dosimetric modeling of bone structures (SPSD modeling) was developed at the Urals Research Center for Radiation Medicine (URCRM). In this method, the parameters of computational phantoms are based on published bone measurement results. The use of numerous literary sources allows us to do without the use of autopsy material, as well as to estimate the DF uncertainties associated with individual variability of bones. The cohort of people irradiated on the Techa River includes individuals of different ages, including those irradiated in utero, so it is important to estimate doses in the CMC for the fetus at different stages of pregnancy.

Objective: to develop computational phantoms for dosimetry of the CMC from incorporated Sr-89,90 in the fetal skeleton at the 24th week of pregnancy.

Within the SPSD approach, only skeletal areas with active hematopoiesis were modeled, which were determined based on published data on the distribution of CMC within the skeleton. The modeled skeletal areas were divided into smaller parts – segments, which were described by simple geometric shapes. The parameters of the model included the characteristics of bone microarchitecture, the thickness of the cortical layer, the linear dimensions of the bones, as well as the chemical composition and density of the CMC and bone tissue. In addition to the average values ​​of the parameters, their individual variability was estimated. Based on these parameters, a voxel phantom filled with spongiosa, including trabecular bone and CMC, was generated for each segment in the Trabecula program. Снаружи фантом покрыт плотным слоем кортикальной кости. The phantom was covered with a dense layer of cortical bone on the outside. Radiation transfer was simulated using the Monte Carlo method in the MCNP 6.2 program.

A phantom of the fetal skeleton at 24 weeks of pregnancy was developed. The phantom consists of 34 segments. The presented phantom will be used to estimate doses to the CMC from incorporated Sr-89,90 as part of improving the dosimetry system of the Techa River.