The paper presents the estimated doses to the population of six eastern districts of the Orenburg region, Russia, based on the results of a comprehensive radiation survey conducted in 2019 in 34 settlements with previously found elevated levels of activity concentration of natural radionuclides in tap water from groundwater sources of drinking water supply. It is shown that the average individual annual effective dose due to all natural sources of ionizing radiation in 18 of 34 settlements corresponds to ‘elevated level’ of exposure due to natural sources according to established classification (from 5 to 10 mSv/year), and in another 7 settlements to ‘high level’ (over 10 mSv/year) with radon being the main contributor to the dose. Four settlements of Kvarkensky and Adamovsky districts, where the highest indoor radon concentrations had been found, were selected for a detailed survey, which included measurements of density of radon flux from the soil, radon concentration in soil gas, activity concentration of natural radionuclides in samples of building materials and in soil samples, and activity concentration of radon in tap water from groundwater sources of drinking water supply. Results of the detailed survey proved that the main source of radon in the buildings was the soil gas infiltration; compared to it, the contribution of waterborne radon release was insignificant.

Current patient release criteria established in NRB-99/2009 relate to four radionuclides used in Russia that period of the document preparation. These criteria were calculated only considering the radionuclide decay. Thus, these criteria give conservative assessments which require the patient to stay in dedicated protected room (“hot” room) of the radiotherapy department for several days and do not allow to radionuclide therapy to be given in the outpatient hospital which certainly reduces the availability of this type of treatment. Consideration of the biological excretion of the radiopharmaceutical will be able to make the patient release criteria after radionuclide therapy significantly softer. Recently, new promising radionuclides and radiopharmaceuticals for therapy have appeared, the introduction of which into medical practice is obstructed by the lack of the patient release criteria. Current study is devoted to justification of improvement the approach to definition of patient release criteria after radionuclide therapy with promising and applied radiopharmaceuticals considering biological excretion of radiopharmaceutical. As examples, calculations of patient release criteria were performed for 177Lu-PSMA, 177Lu-DOTA-TATE, 131I-mIBG и Na131I. The dosimetric model used for calculation is based on the model which was used for definition of the current patient release criteria in NRB-99/2009. Additionally, the biological excretion of the radionuclide in radiopharmaceutical, which was assessed according to the published data, was considered. Two phases of biological excretion were evaluated for considered radiopharmaceuticals (fast and slow fractions). The main contribution of the radionuclide decrease in the patient’s body during the first hours after the injection is made by the fast-eliminated fraction. During 4-6 hours after the administration about 50% of these radiopharmaceuticals eliminated via urine. The calculation of patient release criteria were performed for slow-elimination fractions which characterize the decrease of radionuclide activity in the body after the patient release. The following effective half-lives were used: 177Lu-PSMA – 60 hours, 177Lu-DOTA-TATE – 100 hours, 131I-mIBG – 45 hours, Na131I – 7.5 days. The calculations demonstrate when planning a course of radionuclide therapy with four administrations of 177Lu-PSMA, the release of a patient is allowed at the dose rate of 20 μSv/h from the patient at the distance of 1 m; in case of radionuclide therapy with 177Lu-DOTA-TATE, release of a patient is allowed at the dose rate of 12 μSv/h. Considering the fast-eliminated fraction in the first hours after the administration, it can be assumed that more patients with normal renal function can undergo radionuclide therapy with 177Lu-PSMA in the outpatient hospital. Some patients after the 177Lu-PSMA administration and patients in the therapy with 177Lu-DOTA-TATE may be held in the department in the “hot” rooms for 1-2 days until the dose rate decrease to the acceptable levels. The consideration of biological excretion of radiopharmaceutical makes it possible to soften patient release criterion for 131I-mIBG by four times and for Na131I – by 10%. It will allow to release patients after radionuclide therapy earlier without reduce of radiation safety of people around the patient and will increase the capacity of radionuclide therapy department.

Dosimetric modeling of radiation transport in skeletal bone tissues using computational phantoms provides the doses of internal exposure to active marrow. Computational phantoms of ICRP are created for reference people with anatomical and physiological characteristics typical of an average individual. The doses calculated with such phantoms will correspond to certain population-average values. Individual variability will introduce a stochastic component of uncertainty into the dose estimation. The objective of this study is to assess the influence of variability of chemical composition and bone density on the results of dosimetric modeling. The phantoms are represented by simple geometry figures filled with trabecular structures and bone marrow and covered with a cortical layer. Radiation transport was simulated using the Monte Carlo method. The dose factors to convert the radionuclide activity concentration to absorbed dose rates in active marrow were calculated assuming uniform radionuclide distribution in the volume of the trabecular and cortical bone. As a result of the numerical experiments, it has been shown that variations in chemical composition do not introduce an error of more than ± 4% into dosimetric modeling. The effect of bone density on active marrow dose formation depends on the size of a phantom. For computational phantoms with linear dimensions exceeding two electron free path lengths (~ 0.44 cm), variability of bone density within ± 3% leads to a similar relative uncertainty of the dose conversion factor. However, for smaller phantoms, bone density variability leads to uncertainties of 6% or 13% for a source deposited in the trabecular or cortical bone, respectively. The results obtained will be used to assess the uncertainty of bone marrow dosimetry, taking into account the uncertainty of all parameters including the variability of morphometric characteristics of bones, the variability of the active marrow distribution in skeletal sites, as well as the uncertainties introduced by model approximations.

The analysis was performed, whether the following characteristics correspond with each other: data on the annual release of the radionuclide by the enterprise, the calculation model used for establishing the annual permissible release levels of radionuclides, and the annual average volume activity of the radionuclide, determined using the data of routine radiation monitoring of the surface air. Such analysis was carried out for the release of 131I from the L.Ya. Karpov Scientific Research Institute of Physics and Chemistry (Obninsk) in 2013–2022. It is shown that for the enterprise release in 2013–2022, the results of environmental radiation monitoring confirm both the data of radiation control of the ¹³¹I release source and the correctness of the radionuclide air transfer calculation model. The average annual meteorological dilution factor of the ¹³¹I for the enterprise release in the surface layer of the atmosphere, estimated from monitoring data, does not exceed the model calculated value. Strong correlation was revealed between the average annual volume activity of ¹³¹I in the surface air, obtained using measurement results, and data on annual air releases of the enterprise. No correlation was found for the variability of the dilution factor estimated by the transfer model and monitoring data. It may be caused by the heterogeneity of the ¹³¹I releases by the enterprise during the year.

The article presents results of a long-term (1998–2021) radiological monitoring survey of a recreation base located in a wooded area in the zone of radioactive contamination after the accident at the Chernobyl nuclear power plant. Local mechanical decontamination of the soil had been made on the territory of the base in 1997. The evaluation of the secondary radioactive contamination of the decontaminated territory was performed by comparing dynamics of the radiological situation at the treated plot and the control, nondecontaminated, part of the base according to four main criteria: 1) dose rate of gamma radiation in the air from cesium radionuclides; 2) inventory of ¹³⁷Cs in soil; 3) vertical distribution of ¹³⁷Cs in soil; 4) activity concentration of ¹³⁷Cs in plants and fungi. In 1998, the value of the ¹³⁷Cs inventory in the upper 20 cm of soil in the control part of the territory of the base and in the decontaminated plot was 930 kBq/m² and 143 kBq/ m², respectively. By 2015, the value of the ¹³⁷Cs inventory in the control area and the decontaminated plot had significantly decreased: by 35% and 36%, respectively. A decrease in the dose rate of gamma radiation in the air at the decontaminated plot and control area proceeded at the same rate, which is currently mainly determined by the decay of ¹³⁷Cs. There was a gradual self-restoration of the forest ecosystem at the plot subjected to decontamination. Activity concentration of ¹³⁷Cs in biota (pine, edible mushrooms) in the treated plot was many times lower than that in the control part of the recreation base. In general, there was no significant secondary radioactive contamination of the decontaminated plot in the 24 years after the intervention.

Currently, there is no methodological support for radiation monitoring and sanitary and epidemiological assessment of radon concentration (or radon EEC) and other parameters of the radiation situation in existing operated buildings. The paper presents a review of the protocols for conducting measurements of indoor Leningrad region with previously found elevated levels of radon concentration using long-term measurements. The survey revealed that highest values of indoor radon ECC were obtained using instant measurements in several educational institutions both in the normal operation mode of the buildings (up to 1106 Bq/m³) and after leaving the premises for 12 hours with closed windows and doors (up to 1586 Bq/m³) according to the requirements of paragraph 6.5 of MU 2.6.1.2838-11. High values of radon concentration were also obtained using long-term and short-term measurements (up to 4900 and 1420 Bq/m³, respectively). In addition, high values of radon flux density were detected (up to 2030 mBq/(m²·s)). The established hygienic norms for ambient dose equivalent rate indoors and outdoors were not exceeded in the surveyed educational institutions. The levels of gross alphaand beta activities in tap water sampled from the surveyed educational institutions were below the control levels, and an exceedance of intervention level for activity concentration of radon in analyzed samples was not detected. The results of the survey will be used for hygienic assessment of doses and health risks for students (pupils) and employees of several educational institutions of the Leningrad region due to exposure to radon and its progeny and can be used to improve the method for indoor radon concentration monitoring in existing operated public buildings in the Russian Federation, which in turn will make it possible to obtain correct values of public doses and health risks.

The goal of the research was determination of the level of annual tritium intake in the air from coastal plants of Lake Kyzyltash in 2021 and compliance of tritium content in the air of the coastal area of Lake Kyzyltash in 2021 with radiation safety standards. In the period May-September, 2021, a study of coastal plants near Lake Kyzyltash, a technological reservoir of the Mayak Production Association, was conducted. Within 100 m from the lakeside, humidity level of plants ranged from 41% to 87%, tritium volume activity level in the water of plants and transpiration water varied from 96 Bq/l to ~8.0 kBq/l and from 64 Bq/l to ~9.0 kBq/l, correspondingly. Based on the Cheddock scale, rank correlations between tritium volume activity and: time from the beginning of a vegetation period (weak reverse); distance from the lakeside (marked reverse); humidity of the plants (moderate positive), were revealed. To predict tritium intake in the air in the form HTO during the post-vegetative period, exponential decrease models of humidity and tritium volume activity in the plants with time were developed. The estimates of general periods of semi-decrease in humidity and tritium volume activity in the water of the plants, were 262 and 64 days, correspondingly. Total annual HTO intake in the air in 2021 from coastal plants was 6.92 E+11Bq, with contribution 0.35% of annual tritium intake from Lake Kyzyltash surface. The plants from the zone 0…~5m contribute 81.8% of total annual intake from coastal plants of Kyzyltash Lake (5.66E+11Bq). Annual HTO intake from the plants of Lake Kyzyltash coastline (0…~5m) only, was 5.66E+11Bq and was consistent with tritium release in 2021 from the Kursk Nuclear Power Plant (5.32E+11Bq), and tritium intake from all coastal plants of Lake Kyzyltash – with release from the Leningrad Nuclear Power Plant (6.90E+11Bq). In the course of two expeditions, if there were no precipitations, the mean HTO volume activity in the air of Lake Kyzyltash coastal areas was ~60 Bq/ m³, which is ~30 times less than permissible volume activity in the inhaled air for population 1.9E+3Bq/m³, according to NRB-99/2009. In the case of a hypothetical residence on the lakeside of Lake Kyzyltash in 2021 and a permanent level of tritium volume activity in natural environments, an annual committed effective dose of internal radiation conditioned by inhalation of super-heavy water vapor, will be 31 μSv/year for a critical group of children aged 1-2 years and 8.7 μSv/year for adult residents, according to NRB-99/2009. These estimates are conservative as far as they do not take into account the ice-free period during which there is practically no evaporation of water from Lake Kyzyltash surface and intake from plants.

The article considers the experience of development of public exposure scenarios for land sites with residual radioactive contamination on the example of three sites located in Moscow and St. Petersburg. The study was intended to identify the anticipated groups of land users and select parameters for calculating radiation doses. Exposure scenarios regarding use of land sites for living or working were described by such parameters as duration of the stay, staying indoors or outdoors, physical activity, etc. Exposure pathways for selected users were identified using the conceptual site model approach. For calculations within a number of scenarios, geomigration modeling of radionuclide transport in the environment was performed using the GeRa code. Exposure doses for population groups were calculated using the Ecorad-Aqua software module. Doses were calculated for each exposure pathway. The study demonstrates that the proposed scenario “Office worker” can be applied to various sites that are planned for placing administrative, industrial, scientific, commercial buildings and structures, scenario “Construction worker” – for sites with construction and excavation activities underway. The parameters of the “Resident” scenario allow for its application for the multiapartment residential development in large cities. In the future, it is practical to develop a typical scenario for an outdoor worker whose activity is to provide care and maintenance of the site. These scenarios can be used as ready-made solutions for calculating radiation doses for the population from residual radioactivity at the nuclear sites under decommissioning and remediated areas. Estimates of annual effective doses for the population are needed for decommissioning and remediation planning and determination of the values of radiation factors in the relevant projects.

The article provides an overview of the problems associated with the uranium tailings in Istiqlol city. Many uranium heritage sites in Central Asia, including the uranium tailings in Istiqlol, hadn’t been mothballed before the collapse of the USSR. The burial complex consists of a quarry, dumps of the “Poor Ores Factory”, an unpreserved open mine, destroyed industrial buildings and four tailings which contain 12 million tons of the uranium production waste. In the area of the tailings, the ambient dose rate of gamma radiation is 0.5–0.6 μSv/h, and at some points it reaches 3.0–4.0 μSv/h. The average annual radon emission from the surface is estimated at 3.9×10¹¹ Bq/year. The contaminated areas also include the Sarym-Sakhly Sai stream, mine, industrial and quarry waters, which are characterized by an increased content of ²³⁴U, ²³⁸U and 226Ra. The facilities aren’t physically fenced, allowing free access for the public and livestock. Natural disasters such as mudflows, landslides, and earthquakes can lead to an ecological disaster. Attention is paid to the ways of solving problems such as monitoring radionuclides in water, soil, and air; working with the local population to inform and involve them in rehabilitation work; donors search. The Program for the Implementation of the National Concept for the Rehabilitation of Tailings of Uranium Ore Processing Wastes for 2016–2024 was developed and approved by the Government of the Republic of Tajikistan to minimize the radiation impact on the population and the environment. Implementation of the Program requires significant financial investments and trained personals in the field of radiation safety. Only through the joint efforts of the state, population and international organizations is it possible to fully carry out rehabilitation works. Only by joint the state, public, and international organizations efforts, it is possible to solve these problems. Also, one of the main reasons why the population had received unnecessary overexposure was its ignorance of the danger of using water, soil and building materials contaminated with radionuclides. Therefore, the culture of radiation safety should be studied starting from middle school, where students will be taught about ionizing radiation and possible ways of exposure. Then, both cases of intake of radionuclides into the body, which could have been avoided, and radiophobia among the population living near the extraction and processing of uranium ore, will be much lower. Some social and economic aspects are also touched upon.

This study is aimed at the analysis of perspectives of provision of radiation safety from natural sources of ionizing exposure on the territories included into the Russian Federation in 2022. The study contains comparison of the requirements of legislative acts and regulations on the radiation safety that were active in 4 new subjects of the Russian Federation (Donetsk and Lugansk republics, Zaporozhye and Kherson regions) on the time of their integration with their Russian equivalents. The results indicate the lack of harmonization between acting radiation safety sanitary acts of the Russian Federation and the Ukraine with recommendations of the international organizations. The study contains results of the surveys on the exposure of the public of the Donbass republics and Zoporozhye region by natural sources of ionizing exposure, analysis of the perspectives of the provision of radiation safety of the public of these regions and the Kherson region. Additionally the study includes the evaluation of the existing legislative base on the protection from natural sources of ionizing exposure in the Russian Federation and perspectives of harmonization with the recommendations of international organizations.

Analysis of levels of exposure of public of the Russian Federation by sources of ionizing exposure is one of main parts of the activities conducted by the Federal Service for Surveillance on Consumer Rights Protection and Human Wellbeing. Data on the doses of public of the Russian Federation from medical exposure on facility, regional and federal levels is collected using the form of federal governmental statistical surveillance № 3-DOZ “Data on patient doses from medical X-ray examinations”, that is active since 2000. For the last 20 years there were no significant updates of the form № 3-DOZ. According to the decision of the Board of the Rospotrebnadzor from 11.09.2020, a complex program on update and modernization of form № 3-DOZ was initiated, that has resulted in the approvement of new form № 3-DOZ by the order of Rosstat № 880. The form has been significantly changed to reflect the modern condition of X-ray diagnostics in the Russian Federation. The aim of the current study was to analyze main components of medical exposure dose data collection system that required update and modernization. The study was performed based on the results of assessment of the forms № 3-DOZ from different medical facilities and regions in 2015-2020. The results of the study allowed developing main approaches to the update of the form № 3-DOZ that were implemented in a new edition of the form.