90Sr Concentrations Research Articles

COMPREHENSIVE RADIOLOGICAL AND HYGIENIC MONITORING OF PARTICULAR SETTLEMENTS OF KYIV REGION IN 2019.

to identificate the main factors and assess their impact on the formation of radiation doses to the population of radioactively contaminated areas of Kyiv region at the current stage of the accident based on complexradiation and hygienic monitoring in the reference settlements in 2019. Comprehensive radiological and hygienic monitoring was carried out in eight settlementsof Kyiv region - villages of Ragivka, Lygovyky, Mar'yanivka, Zelena Poliana of Polis'kyi district and villages ofHornostaipil, Dytiatky , Pisky, Karpylivka of Ivankiv district. The content of incorporated 137Cs was determined withdirect measurement on whole body counters (WBC) samples of basic foodstuffs were collected to determine the content of radionuclides 90Sr and 137Cs, residents were interviewed about the levels of consumption of these products,and work was performed to estimate external radiation doses. Mathematical, dosimetric, radiochemical methods areused in the work. There was a further decrease in annual doses of internal radiation in the surveyed settlements in 1.3 times, bothin Polis'kyi district (0.041 mSv · year-1 in 2016, 0.030 mSv · year-1 in 2019) and in Ivankiv district (0.023 mSv · year-1in 2016, 0.018 mSv · year-1 in 2019). It is possible to state a slowdown in the reduction of radiation doses comparedto previous years: from 2010 to 2013, the annual doses of internal radiation in the surveyed settlements decreasedby 1.8-2.4 times, from 2013 to 2016 - by 2.3-3.6 times. The content of 137Cs and 90Sr in milk and potatoes in theinspected settlements is lower than the permissible level of the Hygienic Standard HS 6.6.1.1-130-2006 and the useof these foods can not significantly affect the formation of the internal radiation dose. The content of 90Sr in milksamples in the settlements of Ivankiv district is in the range of 2.1-9.9 Bq · kg-1 (in 2016: 1.3-7.4 Bq · kg-1), whichdoes not exceed the permissible level of 20 Bq · kg-1, but due to the dynamics needs further monitoring. The content of 137Cs in samples of dried mushrooms collected from residents of Kyiv region in 2019, as in previous years, issignificantly (up to 100 times) higher than permissible level, and has a high uncertainty - from 1.4 kBq · kg-1 to223.7 kBq · kg-1. It is established that the annual effective radiation doses of the population in the surveyed settlements in the current year are formed due to internal radiation doses that do not exceed 0.46 mSv · year-1 in Ivankivdistrict and 0.51 mSv · year-1 in Polis'kyi district, which below the RCT criterion 1 mSv · year-1. The main factor that forms the dose of internal radiation of the residents of the surveyed state of emergency of Kyiv region is the intake of 137Cs in the body with forest products, primarily mushrooms.

CAESIUM-137 AND STRONTIUM-90 CONCENTRATION IN PINE FOREST MEAT IN DIFFERENT ECOLOGICAL ZONES OF THE REPUBLIC OF SAKHA (YAKUTIA)

The article discussesthe current problem of food quality control, the content ofstrontium-90 and cesium - 137 in the body of wild game birds-wild game inhabiting the territory of the Republic of Sakha (Yakutia). The object for research were carcasses of wild game 3 species: black grouse; partridge; grouse. Radiation safety of wild game as a food product was determined by its compliance with permissible levels of specific activity of radionuclides, in particular 137Cs and 90Sr. These indicators are regulated by TR CU 021/2011 “on food safety”. According to the long-term (2013-2017) results of our studies 137Cs and 90Sr in carcasses of wild game, Northern, Central, Vilyuisk and southern ecological zones of the Republic of Sakha (Yakutia) was not found to exceed the permissible concentration. As a result of our research, the following results were obtained: the content of 137Cs and 90Sr in grouse carcasses: southern - 70.54±0.71 and 26.43±2.54; Central-64.81±0.18 and 20.89±1.95; Vilyuiskaya - 73.12±0.01 and 28.48±1.18. Black grouse does not live in the Northern ecological zone. The results of the study of partridges are as follows: South-69.04±2.95 and 28.17±0.05; Central - 58,69±2,18 19,87 and±0,39; Vilyui - 70,84±1.55 and 27,87±0,04; North - 28,17±0.05 and of 10.83±0,50. In the study of grouse is established: the content of radionuclides in the southern zone - 71,24±1,95; Central was 60.05±0.01 and of 21.11±1,95; Vilyui - 71,11±0.55 and of 11.47±0,32. According to the results of our studies, the data of exceeding the maximum concentration of 137Cs and 90Sr in the carcasses of wild game in all ecological zones of Yakutia were not established.

Radioactive dispersion in groundwater resulting from postulated accident at a proposed nuclear power plant, northwestern coast of Egypt

Egypt announced a nuclear power program to secure and diversify the country's energy supply. The radiation risks to workers, public and to the environment that may arise from these applications have to be assessed and if necessary, controlled. The radioactivity concentration of groundwater has been predicted for 50 years after a postulated accident at a proposed Nuclear Power Reactor at El-Negila, Northwestern Coast of Egypt. The accident is assumed to be resulting from a loss of coolant accident (LOCA) of a 1000 MWe Nuclear Power Reactor of the pressurized water type. The radioactive releases were estimated and a conservative estimate of dispersion in air and the consequent contaminant transport of radioactive pollutants through groundwater around the reactor were modeled. Of greatest interest in terms of long term radiation contamination hazard of the surface are 137Cs and 90Sr isotopes as their radiological significance increased with time. The analysis results from RASCAL code are used as the input data to MODFLOW-MT3D model, to predict radioactive contamination of groundwater for 50 years of simulation. Two scenarios for groundwater dispersion are assumed. The 1stscenario considered no pumping, while the second scenario assumes stressing of the system through pumping wells. The results of groundwater modeling show that the radioactive concentration of 137Cs and 90Sr were higher at the point source location of the released source term compared to WHO limits on drinking water borne radionuclides and decreased in all directions during 50 years of simulation indicating radionuclides retention in the aquifer matrix taking into consideration that 90Sr was retained more than 137Cs. Applying the 2nd scenario revealed that still low concentrations appear in a pumping well at the coast for both 137Cs and 90Sr, due to the fact that several factors affect the dispersion in groundwater (half life time, dispersion, adsorption-desorption).

Модель біогенних потоків і депо 90Sr у забруднених соснових насадженнях

Лісові екосистеми вважають найбільш постраждалими внаслідок радіаційного забруднення після аварій на Чорнобильській і Фукусімській АЕС. Потрапивши у довкілля 137Cs і 90Sr, швидко включилися у біогеокругообіг речовини деревних фітоценозів. Останнього із перелічених радіонуклідів стосується значно менша кількість наукових публікацій за цим напрямом досліджень, тому подано розроблену модель біогенних потоків та депо 90Sr типового соснового насадження Чорнобильської зони відчуження. Спираючись на вихідні дані спостережень упродовж 2016–2019 рр. за сосновою ділянкою: концентрації і запаси радіонукліда у вивчених депо та потоках органічної речовини та інші показники, здійснено оптимізацію параметрів системи рівнянь потоків 90Sr між його депо імітаційної математичної моделі біокругообігу досліджуваного радіоізотопу методом стохастичного градієнтного спуску шляхом мінімізації суми квадратів відхилень цільової функції. Оцінено динаміку перерозподілу активностей 90Sr у компонентах біогеоценозу. Встановлено можливість депонування компонентами біомаси більшої половини активності 90Sr від наявної у сосновому біогеоценозі. Прогнозовано часові ряди коефіцієнтів переходу радіонукліда від ґрунту до елементів стовбура. Виявлено "стабілізацію" значень коефіцієнтів переходу 90Sr розрахованих, використовуючи щільність забруднення метрового шару ґрунту, що в разі підтвердження на більшому масиві спостережень за лісовими ділянками з контрастними ґрунтами та іншим деревним складом можна використовувати як простий спосіб прогнозування вмісту радіонукліда в компонентах біомаси.

Investigation on 90Sr concentrations in foods near Ningde Nuclear Power Plant in 2013-2017

Objective To investigate the 90Sr concentration levels in the monitoring areas and the control area at Ningde Nuclear Power Plant (NPP). Methods Food samples were collected from the monitoring areas in 30 km of Ningde NPP and the control area far away. The radioactive levels of 90Sr in food samples were analyzed using the chromatography with 2-(2-ethylhexyl) phosphate fast extraction method. Results In this survey, 90Sr radioactive concentrations in 30 varieties of foods in 6 categories were analyzed. In the monitoring area, 90Sr radioactivity concentration in the samples collected were in the range of 0.017-1.830 Bq/kg for cereals, beans and potatoes, 0.021-0.318 Bq/kg for vegetables, 0.007-7.690 Bq/kg for quatic products, and 0.009-0.184 Bq/kg for meats; whereas, in the control area, cereals, beans and potatoes in 0.017-0.700 Bq/kg, vegetables in 0.034-0.677 Bq/kg, aquatic products in 0.038-3.360 Bq/kg, and meats in 0.019-0.054 Bq/kg. Conclusions The 90Sr radioactive concentrations in foods were far below the food standard limits in this survey. The contribution of evaluated to the public from the 90Sr in foods was neglectable. Key words: Nuclear power plant; Food; Radioactive levels; 90Sr

Radionuclide distributions and migration pathways at a legacy trench disposal site

This paper examines the distributions of several anthropogenic radionuclides (239+240Pu, 241Am, 137Cs, 90Sr, 60Co and 3H) at a legacy trench disposal site in eastern Australia. We compare the results to previously published data for Pu and tritium at the site. Plutonium has previously been shown to reach the surface by a bath-tubbing mechanism, following filling of the former trenches with water during intense rainfall events. This has led to some movement of Pu away from the trenched area, and we also provide evidence of elevated Pu concentrations in shallow subsurface layers above the trenched area. The distribution of 241Am is similar to Pu, and this is attributed to the similar chemistry of these actinides and the likely in-situ generation of 241Am from its parent 241Pu. Concentrations of 137Cs are mostly low in surface soils immediately above the trenches. However, similar to the actinides, there is evidence of elevated 137Cs and 90Sr concentrations in shallow subsurface layers above the trenched area. While the subsurface radionuclide peaks suggest a mechanism of subsurface transport, their interpretation is complicated by the presence of soil layers added following disposals and during the subsequent years. The distribution of 90Sr and 137Cs at the ground surface shows some elevated levels immediately above the trenches which were filled during the final 24 months of disposal operations. This is in agreement with disposal records, which indicate that greater amounts of fission products were disposed in this period. The surface distribution of 239+240Pu is also consistent with the disposal documents. Although there is extensive evidence of a mobile tritium plume in groundwater, migration of the other radionuclides by this pathway is limited. The data highlight the importance of taking into account multiple pathways for the mobilisation of key radioactive contaminants at legacy waste trench sites.

Оценка радиационной обстановки в районе расположения судоремонтных предприятий, осуществляющих утилизацию судов с ядерной энергетической установкой

Purpose: To study radiation and health physics situation in the vicinity of the shipyards “The 10th Shipyard, a Holder of Order of the Red Banner of Labor” (JSC “10 SRZ”) and “The Nerpa Shipyard” – a branch of the JSC “The Shipyard Center “Zvezdochka” (SRZ “Nerpa”) after the completion of the main stage of nuclear submarine dismantling and to assess potential effect of on-going activities to the environment and population.
 Material and methods: The following methods were used in radiation survey: pedestrian gamma survey of the site using portable gamma spectrometry complexes, gamma spectrometry and radiochemistry methods to determine the activity of manmade radionuclides in samples of environmental media. 
 Results: Radiation and health physics studies were carried out from 2013 till 2017. It was shown that gamma dose rate within the health protection zones and supervision areas (SA) of the shipyards including the territories of the nearest cities – Snezhnogorsk and Polyarnyi – was at the level of regional values and did not exceed 0.14 µSv/h. The activities of radionuclides in soil from the surveyed sites did not exceed 23 Bq/kg for 90Sr and 100 Bq/kg for 137Cs. Concentrations of 90Sr and 137Cs in plants (mosses) at the surveyed sites did not exceed 70 and 48 Bq/kg, respectively, this is a bit higher than the background levels of the reference village of Belokamenka (1 and 20 Bq/kg, respectively, for 90Sr and 137Cs). The activity of seawater (Barents Sea) in 2016–2018 reached 60 mBq/l for 90Sr and 4 mBq/l for 137Cs, at mean values from 2 to 4 mBq/l over the period between 1990 and 2000 for the studied radionuclides. Data for 137Cs and 90Sr measured in samples of local wild plants, in particular, mushrooms, did not exceed 100 Bq/kg, this is much lower than the established permissible specific activities.
 Conclusion: Considerable impact of the work on the dismantling of nuclear submarines, maintenance ships and ships with a nuclear energy installation on the radiation situation in the areas of shipyards and health effects in the population of Snezhnogorsk and Polyarnyi was not revealed. However, along the external border of the surveyed shipyards some local parts of the sites of 5500 m2 area were found, where the specific activities of 90Sr and 137Cs in soil exceeded background levels and bordered by the level of permissible specific activity for unlimited use of solid materials (137Cs – 100 Bq/kg).

The progeny of Chernobyl Arabidopsis thaliana plants does not exhibit changes in morphometric parameters and cellular antioxidant defence system of shoots

Morphometric parameters and functional state of the cellular antioxidant defence system of shoots were studied in the progeny of Arabidopsis thaliana (L.) Heynh. (A. thaliana) plants, previously and chronically exposed in the Chernobyl Exclusion Zone (ChEZ). Changes in cellular antioxidant enzyme activities in the progeny of exposed plants were assumed because antioxidant status of cell may be altered by inherited epigenetic changes, resulting in changes in antioxidant-response genes expression. These changes can be inferred as induced expression of CAT and SOD genes was found previously for A. thaliana plants by another group of scientists. It is well-known that ionizing radiation may induce changes in hormonal-signalling net-work, shifting balance in growth factors that may cause changes in morphometric parameters of plants. Seeds from A. thaliana plants were collected in the ChEZ at different levels of the external dose rate from 0.28 ± 0.01 to 12.93 ± 0.08 μGy/h. Internal dose rate for parent plants was calculated on the basis of the activity concentration of 90Sr and 137Cs in the plants, using dose conversion coefficients for wild grass. Total dose rate, absorbed by parent plants, was calculated as the sum of the external and internal dose rate and was in a range between 2.8 ± 0.2 and 99 ± 8 μGy/h. Seeds were then grown in the standard laboratory conditions (nutrient-agar, light-dark cycle and appropriate temperature) to analyse morphometric parameters of seedlings and final germination percentage. No significant changes in the morphometric parameters (root length and rosette diameter of shoots) of the seedlings were observed. Changes in the final germination percentage of the studied seeds were found, but low correlation was observed between found changes and the dose rate, absorbed by parent plants. In contrast to the results obtained in A. thaliana plants directly sampled in the field, no effect on the functional state of the cellular antioxidant defence system of shoots in the progeny of Chernobyl A. thaliana plants was observed.

Radiation-hygienic assessment of the concentration and distribution of <sup>90</sup>Sr and <sup>137</sup>Cs in ichthyofauna of the Ob’-Irtysh river system

The aim of the work is the radiation-hygienic assessment of 90Sr and 137Cs content in fish of the Ob-Irtysh river system and the study of the basic laws of the radionuclides accumulation in the ichthyofauna of these rivers. To perform this task, long-term results of radioecological studies of fish from the Techa, Irtysh and Ob rivers for the period 2004-2016 were used. Fish as a food product was evaluated according to two criteria: a) permissible levels of radionuclides specific activity (SanPiN 2.3.2.1078-01); b) using the indicator of conformity В and uncertainty of its definition ΔВ (GOST 32161-2013 and GOST 32163-2013). It is shown that a higher content of radionuclides is observed in the ichthyofauna of the Techa river (1379.1 Bq/kg for 90Sr and 41.9 Bq/kg for 137Cs). On the Ob and Irtysh rivers, the average specific activity of radionuclides in fish was significantly lower and slightly changed during the surveyed area: for 90Sr in the range of 6.0 ÷ 8.1 Bq/kg (mean 6.8), for 137Cs – 0.6 ÷ 1.9 Bq/kg (mean 1.3). Assessment for compliance with radiation safety criteria using the indicator of compliance and its uncertainty (В+ΔВ) confirmed the unsuitability of use for food purposes by the radiation factor of all studied fish species from the Techa river (45÷55 >1). Fish from all other studied areas of the Ob-Irtysh river system can be used for food without restrictions (0,06÷0,53 < 1). The distribution of 90Sr and 137Cs in the ichthyofauna of the Ob-Irtysh river system part over a 2400 km is presented in the form of empirical regression models. The models describe a sharp decrease in the radionuclides specific activity in fish in the Techa and Iset rivers by two orders for 90Sr (from 2000 to 20 Bq/kg), and by one order for 137Cs (from 40 to 2 Bq/kg). With a high degree of reliability (R2>0.86 for 90Sr and R2>0.92 for 137Cs), the presence of power relationships between the content of radionuclides in the ichthyofauna and their content in water was shown, with adequacy confirmed by Fisher’s F-criteria. This can be used for a preliminary assessment of the radionuclides level in fish based on the results of measurements of the average annual concentrations of these radionuclides in water.

Interpretation of FISH Results in the Case of Nonuniform Internal Radiation Exposure of Human Body with the Use of Model Approach

The fluorescence in situ hybridization (FISH) technique allows for the estimation of the number of stable chromosomal aberrations (translocations) in human blood T-lymphocytes decades after radiation exposure. Therefore, it is used for retrospective assessment of irradiation doses received by red bone marrow (RBM). Cytogenetic analysis of individuals exposed on the Techa River in the 1950s to 89,90Sr, locally irradiating RBM, showed that dose assessment based on FISH data led to underestimation of the actual dose estimated from measurements of whole-body 90Sr content. The purpose of current study was to evaluate the dose–effect relationship and the frequency of translocations per 1 Gy of RBM irradiation dose and T-lymphocytes dose for donors living in Techa riverside villages (n = 178; translocation yield = 2389; number of genome equivalents GE = 96 446). Irradiation doses were estimated using the latest version of the Techa River dosimetry system and the T-cell irradiation model. Statistical analysis showed that the frequency of translocations per 1000 GE per 1 Gy of RBM dose was 8.0 ± 0.7; this value was statistically significantly lower than the value estimated for Sellafield radiation workers under external exposure (11.6 ± 1.6). At the same time, the use of T-cell and their progenitor doses led to re-evaluation (increase) in the slope of the dose–response curve to 11.8 ± 1.6 per 1 Gy per 1000 GE, which agreed well with the published data. The obtained estimates of the background frequencies of translocations also were close to the published values ​​for unexposed donors. These findings demonstrate the legitimacy of using a model approach for estimation of irradiation doses in T-lymphocytes and their progenitors and the need to take into account complex T-cell dynamics in interpretation of cytogenetic data for the purposes of biodosimetry.

Radiation-hygienic monitoring and assessment of the doses of the public residing on the radioactively contaminated territories of the Tula region

Aim of the study: analysis of the results of the radiation-hygienic monitoring of the territories of the Tula region, contaminated due to the Chernobyl NPP accident; concentration of 137Cs and 90Sr in the locally produced food products and analysis of the annual effective dose of the public. Materials and methods: the study was performed in the Tula region in 1997-2018. It included the evaluation of the indicators of the radiation safety of more than 50 thousand samples of the main food products, sampled in the areas of the radioactive “Chernobyl” contamination of the region with the simultaneous measurement of the external gamma-radiation dose rate in the stationary control points. Additionally, it included the assessment of the dynamics of concentration of 137Cs and 90Sr in food products, maximal values of mean annual effective doses of the public and contribution of the collective dose from medical exposure into the structure of the annual collective dose of the public. Results: The study allowed estimating the concentration of 137Cs and 90Sr in the main local food products. Estimated values of gamma radiation dose rate were stable and laid in the range of normal variations specific to the middle latitudes of the European part of Russia. The values of maximal mean annual effective doses of the public indicate the stable radiation environment and do not exceed 1 mSv. It should be mentioned that the contribution of collective dose from medical exposure into the annual collective dose of the public as well as the values of mean individual effective doses from medical exposure are reducing with the increase in the number of X-ray examinations. Conclusions: The lack of exceedances of the permissible levels of 137Cs and 90Sr in the locally produced food products and the reduction of the mean annual effective dose of the public indicates the possibility of the transfer of the settlements affected by the Chernobyl NPP accident into the normal living conditions within the program of the transfer of the settlements from the “Chernobyl” zone.

Radioecological monitoring in the vicinity of Rostov NPP. The analysis of results of long-term investigations

The purpose of this work was to assess the influence of the Rostov NPP (consisting of 4 units with VVER1000 reactors) on the radioecological situation in the region of the station location within 18 years from the start of the first power reactor. Based on the results of observations at the radioecological monitoring network established in 2001, which included seven control sites and five control points, the content of natural and artificial radionuclides in environmental objects, agricultural products and foodstuffs was analyzed. It was shown that over the entire period under consideration, the average content of 90Sr in the soils of agroecosystems of the 15-km zone of influence of the Rostov NPP varied within 1.7-7.4 Bq/kg, and 137Cs – 7.5-14.9 Bq/kg. It was not detected any trends to increase in the concentrations of artificial radionuclides in the soil throughout the considered territory. The variation range of the average content of natural radionuclides in soils was 561-634 Bq/kg for 40K, 23.4-27.5 Bq/kg for 226Ra and 32.7-35.9 Bq/kg for 232Th. The average concentration of 90Sr in the grain was in the range of 0.1-0.68 Bq/kg, and 137Cs – 0.23-0.54 Bq/kg. Even the maximum specific activity values of artificial radionuclides in food grain were below the SanPiN standards 55 times for 90Sr and 65 times for 137Cs. The maximum levels of 137Cs in vegetables and potatoes and vine crops were 80 times lower than the SanPiN standards. The maximum levels of specific activity of 90Sr in milk were more than 400 times lower than the SanPiN standard (25 Bq/kg), and for 137Cs (standard 100 Bq/kg) this difference was 600 times. Vegetable crops were characterized by minimal transfer factors (TFs) of radionuclides. TFs of 90Sr in vegetables, depending on the product type, was in the range of 0.04-0.17, and for 137Cs it was in the range of 0.008-0.2 (Bq/kg)/(kBq/m2 ). Maximum TFs of radionuclides were noted in grasses. TF of 90Sr in natural and perennial grass was 0.75-2.2, and for 137Cs it was 0.28-0.86 (Bq/kg)/(kBq/m2 ). The differences in transition factors between vegetables and grass reached 50 times, and on average, they were 10-20 times. It was noted that all types of crops accumulated 90Sr on average 2-5 times more in comparison to 137Cs ac cumulation. It was shown that the content of artificial radionuclides in the water of the Tsymlyansk reservoir is 163 and 183 times lower than the permissible level for 90Sr and 137Cs, respectively. The analysis of 18-year results of observations of the radioecological situation in the vicinity of the Rostov NPP allows to conclude that the operation of this NPP in normal mode and the commissioning of new power-generating units did not lead to a recorded increase in the content of artificial radionuclides in agricultural products, foodstuffs and environmental objects.

Influence of Physicochemical Factors on Radionuclide Leaching from Soil

The degree of radionuclide leaching from soil in the region of the Atomic Lake (Kazakhstan) was determined. The 3H and 90Sr concentrations in aqueous extracts increase with increasing time of interaction of the soil with the leaching solution. A decrease in the 239+240Pu transfer into the solution with time may be due to the formation of colloids in the course of leaching, followed by their deposition or sorption onto soil components. Despite relatively high initial content of γ-emitting radionuclides (137Cs, 241Am, 152,154Eu, 60Co) on the level from n × 102 to n × 104 Bq kg−1 in the soil, in leaching experiments the content of these radionuclides in aqueous extracts was below the detection limit of the procedure used (<1 Bq L−1). The influence exerted on the leaching by the grain-size distribution of soil, pH of the medium, degree of mineralization, and chemical composition of water was determined. The tests performed suggest that the transfer of artificial radionuclides from the soil into water by leaching is one of the main mechanisms of radioactive contamination of the Atomic Lake water.

Crystallization behavior, structure and properties of glasses in SrO–Fe2O3–P2O5 system

Crystallization behavior, structure and properties of the glasses in SrO–Fe2O3–P2O5 ternary system, with the content of P2O5 fixed to be 60, 50 and 40 mol%, were studied systematically. For vitreous samples, thermal expansion coefficients (TEC) and characteristic temperature were obtained by using a thermal dilatometer, while their thermal stability was examined by using a differential scanning calorimeter (DSC). Accordingly, their heat treatment schedules were determined. Furthermore, their chemical durability was characterized according to the dissolution rate (DRwater) in distilled water at 90 °C. Glass forming region of the SrO–Fe2O3–P2O5 ternary system at 1250 °C has been identified. It was found that crystallization behavior, crystalline phase compositions, structure and properties of the samples are closely related to the ratios of O/P and Fe/P. Specifically, the iron phosphate glasses were explored as the host matrices to immobilize high-level radioactive wastes (HLWs) with high contents of 90Sr.

Levels of radionuclide concentrations in benthic invertebrate species from the Balearic Islands, Western Mediterranean, during 2012-2018.

Baseline levels of radionuclides in the marine environment of the Balearic Islands in Western Mediterranean have not been reported in literature. Because of their ecological role and acknowledged sensitivity to pollutants, herein, the activity concentrations of 210Po, 40K, 210Pb, 90Sr, and 234Th were measured in two types of benthic invertebrate species (mussels and sea urchins) sampled during 2012-2018. The activity concentrations of 210Po, 40K, 210Pb, and 234Th ranged from 38 ± 1 to 325 ± 11 Bq kg-1 dry weight (d.w.), 220 ± 10 to 996 ± 46 Bq kg-1 d.w., ND (lower than the limit of detection) to 55 ± 8 Bq kg-1 d.w., and ND to 70 ± 15 Bq kg-1 d.w., respectively. In all cases, no artificial 90Sr activity was detected in the collected samples. The committed effective dose to humans was calculated to be in the range of 48-640 μSv year-1.

137Cs and 90Sr in surface waters of the Sea of Japan: Variations and the Fukushima Dai-ichi Nuclear Power Plant accident impact

90Sr and 137Cs activity concentrations in surface waters of the Sea of Japan (SOJ) decreased during the period of 1993–2010 with effective half-lives of 18 and 15 y, respectively. The longer effective half-life of 90Sr in the SOJ may suggest a surplus of 90Sr to SOJ surface waters, however, no clear evidence of possible 90Sr source has been found. After the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident, temporal variations of 137Cs in the surface water of the SOJ have changed, while 90Sr variations followed the pre-accident trends. The 90Sr/137Cs ratios reveal that increases of 137Cs due to the FDNPP accident continued in surface waters of the SOJ until 2016.

Current state and trends in the content of 137Cs and 90Sr in abiotic and biotic components of Arctic ecosystems (Barents and Kara Seas case study)

This publication summarizes long-term data on radioactive contaminants in seawater, bottom sediments, and marine fish and describes current patterns in radionuclide distribution using data collected by the Murmansk Marine Biological Institute during cruises to the Barents and Kara Seas in 2015–2017. During the study period, no short-lived artificial radionuclides were found in the Barents and Kara Seas. 137Cs and 90Sr isotopes with a longer half-life are still registered in Atlantic waters that are the main source of radioactive contamination in these Arctic seas. Volumetric activity of 137Cs and 90Sr was compared at different depths. A uniform distribution of 137Cs in the vertical column of water and a tendency to increase the volume activity of 90Sr from surface to bottom were observed in the Barents Sea. Bottom sediments in the Kara Sea contain on average 2 times more 137Cs than the Barents Sea. Atlantic cod is characterized by an extremely low concentration of 137Cs in muscular tissue, about an order of magnitude lower than in the period of maximum contamination of Barents Sea waters observed in 1982. Currently there is a decreasing trend in concentrations of anthropogenic radioisotopes in the environment and biota. Processes of 137Cs and 90Sr removing from biotic and abiotic components are described with exponential functions. Due to natural marine purification processes, the decrease of 137Cs and 90Sr concentrations in the Barents and Kara Seas occur 2–4 times faster than the physical radioactive decay of these radionuclides.

Комплексные организационные и методические подходы к выводу из эксплуатации хранилищ РАО

Purpose: Development of comprehensive organizational and methodical approaches to decommissioning of shallow radwaste (RW) repositories.&#x0D; Material and methods: The following researches were conducted during assessment of radiation and hygiene situation:&#x0D; - assessing the state of physical barriers of repositories (tanks) of solid and liquid RW;&#x0D; - assessing radiation situation at the repository site before and after remediation;&#x0D; - measuring specific activity of 90Sr and 137Cs in ground and subsurface water, core sample, soils, building structures.&#x0D; Methods: on foot gamma survey; gamma-ray spectrometric measurement of radionuclides in environmental samples using a stationary spectrometer; radiochemical extraction of radionuclides and their radiometry.&#x0D; Results: The surveys were performed in 2014–2016. They delivered data on gamma dose rate at the RW repository site, specific activity of 90Sr and 137Cs in ground and subsurface water, core sample, soils, building structures.&#x0D; The surveys showed that content of 90Sr in subsurface water varied from 0.25 to 0.4 Bq/kg, while content of 137Cs was below the detection threshold (0.01 Bq per sample). It was founded that distribution of 90Sr and 137Cs in soil (core sample) forming the top layer of the area is highly uneven. In some cases specific activity of soil exceeded 1000 Bq/kg (C-23 well at the depth of 2.75 m and C-24 well at the depth of 5 m). In all other cases specific activity of the core sample did not exceed 10 Bq/kg, and specific activity of soil was up to 50 Bq/kg which is over background values. The ambient dose equivalent rate at the site varied from 0.1 to 0.3 µSv/h.&#x0D; After remediation activities content of radionuclides in soil and subsurface water was at the levels of background values.&#x0D; More than 6700 measurements were performed (more than 2400 measurements of the ambient dose equivalent rate, more than 4100 measurements of beta-contamination of work surfaces and equipment, and more than 200 measurements of specific and volumetric activity of environmental samples). &#x0D; Conclusions: This work allowed to substantiate technical solutions, procedure of RW accounting and control, using of shelters and mobile systems for radiation safety of the personnel and environmental protection.&#x0D; It was demonstrated that average external radiation doses for the workers involved in decommissioning activities did not exceed 0.7 mSv (variation from 0.16 to 1.7 mSv), while internal radiation doses varied from 0.35 to 3.3 µSv. &#x0D; Density of beta-contamination of the site did not exceed 38 beta-particles/(cm2∙min) which corresponds to background values. The ambient dose equivalent rate of the site was within 0.09-0.15 µSv/h after the work has been done.

Nuclear contamination sources in surface air of Finnish Lapland in 1965\u20132011 studied by means of 137Cs, 90Sr, and total beta activity

Radionuclides 137Cs and 90Sr and total beta activity were determined from air filters collected in Rovaniemi (Finnish Lapland) in 1965–2011. Nuclear contamination sources present in the air filter samples as well as temporal changes in radionuclide concentrations were examined. Ozone observations and meteorological modeling were used in combination with radionuclide analyses to study the reasons behind the observed seasonal concentration variation. In general, the magnitude and variation in activity concentrations of 137Cs and 90Sr and total beta activity in the surface air of Rovaniemi in 1965–2011 corresponded well with values from other countries. However, the obtained results prove in practice that hardly any refractory or intermediate radionuclides from the destroyed Chernobyl reactor fuel were introduced to Finnish Lapland. The main source of 137Cs and 90Sr and total beta activity in the surface air of Rovaniemi in 1965–2011 has been intense atmospheric nuclear weapon testing in 1950s–1960s and later tests performed in 1965–1980, as well as leakages from underground nuclear tests in Semipalatinsk, 1966, and Novaya Zemlya, 1987. For 137Cs and total beta activity, the influence of Chernobyl and Fukushima accidents was detected.

Determination of 90Sr in environmental samples using solid phase extraction chromatography

A simple and rapid method based on solid phase extraction chromatography (SPEC) has been developed for the determination of 90Sr in environmental samples. The SPEC method consists of three steps, namely, (1) carbonate precipitation of alkaline earths, (2) column separation of strontium using 4,4′(5′)-bis(tert-butylcyclohexano)-18-crown-6 based Sr spec resin and (3) beta counting of SrCO3 using low background gas flow counter. Minimum detection limit (MDL) of low beta gas flow counter is 1.42 Bq/kg for 10,000 s counting time. The capacity of the column for strontium was about 12.2 ± 0.5 mg of Sr per g of Sr spec resin. The SPEC method using Sr spec resin was standardized with 90Sr spiked samples and tested on sediment samples of Mumbai harbour bay. The average activity concentration of 90Sr in sediment samples was found to be 2.2–13.7 Bq/kg. The results obtained by SPEC method have been found to be in good agreement with conventional gravimetric method.