Specific Activity Of Radionuclides Research Articles

Study on induced radioactivity in proton therapy accelerators

The study focuses on the investigation of induced radioactivity resulting from the operation of a proton therapy accelerator which poses an enduring risk to both staff and the public. Therefore, it is imperative to conduct research on this topic. The Monte Carlo code FLUKA is utilized to study the residual dose rate of a 250 MeV proton therapy accelerator under various operational and cooling durations, as well as the types and specific activities of radionuclides produced in the structural components, concrete walls, cooling water, cooling water pipe, soil, and underground water. The findings indicate that after continuous operation for 100 days followed by a 1-h cooling, the residual dose rate at the distance of 30 cm from the surface of the structural components is 0.98 mSv/h. At this point, maintenance personnel can safely enter the hall. During emergency equipment maintenance after shutdown, it's advised to keep maintenance personnel at least 1 m away. After 30 years, cooling water, soil, and underground water meet exemption requirements. Air and concrete walls necessitate cooling for 30 min and 3 days, respectively. Directly exemption cannot be granted for metal components due to long-lived nuclides present in these materials, such as 60Co which takes over several years to decay to safe levels. Consequently, highly activated metal components require remote disassembly and storage.

Assessment of Radioactivity of Some Samples of Healthy Drinking Water and Liquefied Water in Some Areas of the Capital Baghdad Using HPGE Detector System

In this work, a total of 20 water samples were collected from various locations inside the city of Baghdad. Each sample consists of a volume of 1 litre of water which had been obtained from multiple geographical locations. There were twelve water samples representing pure tap water sourced from various locations additionally, eight samples of mineral water were obtained from several marketplaces in Baghdad. A total of six radionuclides were detected in the water samples using the HPGe detector. These radionuclides were identified as Bi 214, Ra 226, TI 208, Bi 212, Pb 212, and K 40. Among these, Bi 214 and Ra 226 are part of the U-238 series, while TI 208, Bi 212, and Pb 212 belong to the Th 232 series. Additionally, K 40 is a naturally occurring radionuclide. The observed minimum value for the average specific activity of radionuclides in pure tap water samples was Al-Yarmouk Pure tap water. However, the sample Hay Al-qahira pure tap water exhibited the highest recorded specific activity values of radionuclides in pure tap water. The observed minimum value for the average specific activity of radionuclides in mineral water samples was Bardaa mineral water. However, the sample (W15) exhibited the highest recorded values for the specific activity of radionuclides in mineral water. The measured external dosage of natural radioactivity in water samples from Baghdad was found to be relatively low, at 0.366 mSv.y-1. This value falls below the recommended limit the United Nations Scientific Committee set on the Effects of Atomic Radiation (UNSCEAR), 1 mSv.y-1.

Spatial distribution of 137Cs; 40K, 226Ra, 232Th in soils of Monchegorsk city (Murmansk region)

The purpose of the study was to establish the patterns of spatial distribution of radioactivity of technogenic 137Cs and natural radionuclides 232Th, 226Ra, 40K in urban soils of Monchegorsk. Location and time of the study. Soil samples, were collected in summer 2018 in the Monchegorsk city, Murmansk region, Russia. To study the specific activity of radiocesium and natural radionuclides, soil samples were taken from topsoil (0-5 cm) at 82 sites, including 68 sites within the city territory (urban soils) and 14 sites beyond the city limits in the subtorch areas strongly affected by the Severonickel factory. Similar studies of urban soils in Monchegorsk had not been carried out previously. Methods. During expeditionary work and laboratory research, soil, radiological, and mathematical and statistical methods were used. When carrying out gamma spectrometric measurements, radionuclides 137Cs, 226Ra, 232Th and 40K were determined on a low-background semiconductor gamma spectrometer ORTEC (USA) based on a high-purity coaxial germanium detector GEM10P4–70 (HPGe) with a SBS-75 pulse signal processor and Gamma-software. The resolution of the gamma spectrometer along the 1.33 MeV line (60Co) was 1.75 keV, and the relative efficiency was 15%. Calibration and quality control of gamma spectrometric measurements was carried out using volumetric activity measurements with 1-L Marinelli vessels of different densities (RITVERZ, Russia-Germany). Main results. The values of specific activity of radionuclides in soil samples were as following: in the technogenic 137Cs up to 31.3 Bq/kg and in the subtorch soils up to 63.4 Bq/kg. Specific activity of natural radionuclides in urban soils reached to 14.2 Bq/kg for 226Ra, whereas in the subtorch soils it reached 21.6 Bq/kg. The specific activity of 232Th in urban soils reached 18.3 Bq/kg, with 17 Bq/kg registered for the subtorch soils. As for 40K, its specific activity reached 498 Bq/kg in the urban soils and 317 Bq/kg. Conclusion. The gamma survey of the Monchegorsk territory did not reveal any anomaly in radiation. The dose rate of gamma radiation in the city does not exceed 0.074 μSv/hour, which is less than the values elsewhere in Russia, ranging from 0.04 to 0.20 μSv/hour. The obtained data about specific activity of technogenic 137Cs and natural radionuclides 232Th, 226Ra, 40K in the Monchegorsk soils are typical for the Murmansk region.

Radioactivity study of EAST structural materials based on neutron activation system

The plasma operation in the Experimental Advanced Superconducting Tokamak (EAST) would generate 2.45 MeV neutrons and a small fraction of 14 MeV neutrons. Neutrons react with structural materials, leading to the production of radioactive isotopes. The identification of nuclides and the determination of radioactive activity are of great significance for radiation protection and fusion material applications. In this study, structural materials including stainless steel 316L(SS316L), stainless steel 304L(SS304L), aluminum(Al), tungsten(W) and copper(Cu) were transported to the activation terminal for fusion neutron irradiation. The gamma ray spectra were measured using high-purity germanium (HPGe) detector, and the main radioactive nuclides of SS316L and SS304L are 56Mn, while the main radioactive nuclide of Al is 28Al. For Cu and W, the main radionuclides resulting from neutron reactions are 66Cu and 187W, respectively. The uncertainty of the radioactivity is 2.27∼7.94 % for W, 1.95∼5.84 % for SS316L, 2.10∼6.07 % for SS304L, 0.68∼1.69 % for Al and 2.59∼6.75 % for Cu. The specific activity of radionuclides is proportional to neutron yield, so the material activation is the main source of radiation dose during irradiation with high-yield neutron. The neutron activation coefficients of SS316L, SS304L, Al, Cu and W are 2.74538 × 10−14, 3.6411 × 10−14, 2.50711 × 10−12, 1.76506 × 10−12 and 3.51725 × 10−14, respectively. The coefficient represents the radioactive activity generated by each fusion neutron. In addition, the predicted activity was calculated using FISPACT program and compared with experiments.

Radioecological monitoring of 90Sr and 137Cs accumulation in fish organisms in certain water bodies of the forest-steppe zone of Ukraine

The study aims to determine the radionuclide contamination formation patterns in ichthyofauna representatives of some Forest Steppe of Ukraine water bodies and to establish reference values for the specific activity of 90Sr and 137Cs in the fish body as of 2021. To determine the radionuclide pollution levels in the industrial ichthyofauna representatives in the water areas of the Kaniv Reservoir, the Kosivskyi, the Bila Tserkva Middle, and the Bohuslav Reservoirs on the Ros River and in the unregulated sections of the Ros River (above the city of Bila Tserkva) and Hnyliy Tikych (the village of Stavyshche) as of 2021, the following fish species were selected: red snapper - Rutilus rutilus L., flatfish - Blissa bjoerkna L., common bream - Abramis brama L., silver crucian carp - Сarassius gibelio (Bloch), bream - Alburnus alburnus alburnus L.; pike - Esox lucius L. (peaceful species); pike perch – Stizostedion lucioperca L.; European-Asian river perch – Perca fluviatilis fluviatilis L. (predatory species). The specific activity of 90Sr and 137Cs was determined in the entire fish body by generally accepted radiochemical and gamma spectrometric methods. In 2021, the registered average specific activity of 90Sr in fish of various species of the Kaniv Reservoir ranged from 0.6 to 1.3; 137Cs - from 2.4 to 13.2 Bq/kg. The average specific activity of 90Sr in fish of different species of the Kosiv Reservoir ranged from 0.1 to 0.5, that of 137Cs – from 0.2 to 2.1 Bq/kg, Bila Tserkva Middle ranged, respectively, from 0.2 to 0.8 and from 0.8 to 4.0, Bohuslav – from 0.1 to 0.5 and from 0.5 (bream) to 3.1 Bq/kg. The average content of 90Sr and 137Cs in the body of fish fished in unregulated sections of the Ros and Hnyliy Tikych rivers was 0.1–0.5 and 0.5–2.0 Bq/kg, respectively. The specific activity of 90Sr in peaceful and predatory fish of most of the studied reservoirs probably did not differ, and we can note only the tendency to the formation of higher levels of accumulation of the radionuclide by peaceful species. However, the values of the specific activity of 137Cs of predatory species exceeded the corresponding values that were registered in peaceful fish. The levels of fish radionuclide contamination in all the studied reservoirs, except for the Kaniv Reservoir, did not differ reliably. The increased content of radionuclides in the Kaniv Reservoir fish compared to other reservoirs of the Forest Steppe can be explained by the constant influx of radionuclides from the ecosystem of the Kyiv Reservoir through the Kyiv HPP dam. During the research period, 58–74% of the total activity of peaceful fish in forest-steppe reservoirs was formed by 137Cs, that of predatory species made 82–93%. The research results made it possible to determine reference and screening values in the specific activity of radionuclides in the fish of the forest-steppe reservoirs as of 2021. For peaceful fish, the value of the reference 90Sr activity in the studied reservoirs of the Forest Steppe is 1.0, the screening activity - 3.0, predatory fish - 0.5 and 2.0 Bq/kg, respectively. For 2021, the reference value of the specific activity of 137Cs in the body of peaceful fish of the Kaniv Reservoir makes 3.2, the screening value - 10.0, the Kosiv, Bila Tserkva Middle, Bohuslav reservoirs,the Ros and Hnyliy Tikych rivers are 2.0 and 6.0 Bq/, respectively kg; that of predatory fish of the Kaniv Reservoir - 12 and 36, respectively, Kosiv, Bila Tserkva Middle, Bohuslav Reservoirs, the Ros and Hnyliy Tikych rivers - 3.0 and 10.0 Bq/kg, respectively. Key words: water bodies of the Forest Steppe, fish, radionuclides.

Estimation of Background Radiation from A Soil Sample from A Barley Farm Area and Malt Factory in East Arsi, Ethiopia

The aim of this work is to estimate the background radiation of a soil sample from the barley farm area and Malt factory in East Arsi, Ethiopia. The technique of gamma-ray spectrometry with a high-purity germanium (HPGe) gamma-ray detector and a PC-based MCA was used. The activity concentration levels due to 40K, 137Cs, 238U, and 232Th were measured within the study area at a depth of 30 cm. The soils of the study region are used as construction material by many farmers. The measured specific activity of those radionuclides was compared with the data reported worldwide. The specific activity of radionuclides was estimated in both study locations. The specific activity 238U of soil samples ranged from 41.0 Bq kg-1 to 30.7 Bq kg-1 in the barley farm, with a mean value of 37.7 Bq kg-1, and for malt ranged from 23.8 Bq kg-1 to 40.6 Bq kg-1, with a mean value of 32.5 Bq kg-1. The specific activity of 232Th in soil samples ranged from 89.9 Bq kg-1 to 156.0 Bq kg-1, with a mean value of 118.6 Bq kg-1, whereas for the Malt factory ranged from 121.0 Bq kg-1 to 128.0 Bq kg-1, with a mean value of 123.7 Bq kg-1. In barley soil samples, the specific activity of 40K ranged from 401.0 Bq kg-1 to 530.0 Bq kg-1 with a mean value at the Malt plant ranged from 518 Bq kg-1 to 598.0 Bq kg-1, with a mean value of 553.6 Bq kg-1. Similarly, the specific activity of 137Cs was determined in both the barley farm and the malt Factory. In barley farm soil samples, it ranged from 3.3 ±0.6 Bq kg-1 to 5.34±0.6 Bq kg-1, and with a mean value of 4.3 Bq kg-1 whereas, in the Malt factory it varied from 3.1 ±0.7 Bq kg-1 to 5.3 ±0.7 Bq kg-1, and with a mean value of 4.5 Bq kg-1. The absorbed dose rate within the barley farm ranged from 24.6 ±2.9 nGyh-1 to 34.1 ±2.9 nGy h-1, and with a mean value of 30.6 nGyh-1, whereas, in the Malt factory, it varied from 31.3 ±1.3 nGy h-1 to 35.5 ±1.3 nGyh-1, and with a mean value of 33.5 nGy h-1. The annual effective radiation dose for BSS and MFSS was calculated to be 37.6 mSv y-1and 41.1mSv y-1. This study revealed that this region lies within a medium radiation background when compared with the world's average. The marginal value of dose is higher within the Malt factory area because of fertilizer consumption for cultivation. Since these estimated background and radiological impact factors are below the recommended values, it seems that there is no potential radiological health hazard related to the soils from both BSS and MFSS in Arsi Asella, Oromia, Ethiopia.

Радиоэкологическая обстановка в районе вводимого в эксплуатацию рудника № 6 пао «Приаргунское горно-химическое производственное объединение»

Purpose: Study of the radioecological situation around mine No. 6 of PJSC ‘Priargunsky Industrial Mining and Chemical Association’ named after E.P. Slavskiy" before commissioning. Material and Methods: During the radiation survey, to measure the ambient dose equivalent rate, the pedestrian gamma survey method was used using the portable spectrometric complex MKS-01A ‘Multirad-M’ (Russia) and the dosimeter-radiometer MKS-AT6101s (Belarus). To study the specific activity of radionuclides in the soil, samples were taken in accordance with GOST 17.4.3.01-2017. The activity of gamma-emitting radionuclides was measured on a stationary gamma spectrometer manufactured by Canberra (USA). The activity of 210Po and 210Pb was measured on the radiometric system UMF-2000 (Russia) after their radiochemical extraction from samples. Dose assessment of exposure to biological objects was made using dose coefficients established in ICRP Publication 136, considering recommendations R52.18.820-2015. Results: The results of the study showed that the ambient dose equivalent rate of gamma radiation varied in a wide range from 0.1 to 4.9 µSv/h. The average value in the background areas is 0.14±0.02 µSv/h. The specific activity of natural radionuclides outside the rock dumps, except for 40K, in some areas exceeds the background values up to 10 times. The ecological risk for the considered terrestrial biological objects (grass, shrub, soil worm and mouse-like rodents) does not exceed 10‒2. Conclusion: There are areas on the territory with traces of anthropogenic activity, which led to man-made radiation contamination. The highest levels of ambient dose equivalent of gamma radiation occur near rock dumps. The rest of the territory has local areas with radioactive contamination. Doses of exposure to biological objects don’t have a significant effect on the incidence, reproduction, and life expectancy of terrestrial biological objects.

Radiation and Environmental Safety in the Exploration and Development of Metal Deposits in South Yakutia

Radiometric surveys of mining dumps on spent placers of gold, monazite and the exploited gold-uranium ore deposit in South Yakutia were carried out. It is established that the dumps of alluvial, overburden and waste rocks in terms of the effective specific activity of radionuclides when used in construction work are characterized by different degrees of tolerance. It is shown that stacked radioactive ore dumps at the “Lunnoye” deposit after heap leaching of gold become powerful uncontrolled sources of radioactive pollution of the environment. It is recommended to conduct periodic monitoring of their radioactivity levels by express methods of field radiometry for the safe use of mining dumps as building materials.

RADIOECOLOGY MONITORING SYSTEM FOR MOUNTINE AREAS OF THE TISZA RIVER BASIN (TRANSCARPATHIA, UKRAINE)

Regularities of distribution, migration and accumulation of natural gamma-active nuclides 40K, series of uranium 238U (214Pb, 214Bi) and thorium 232Th (212Pb, 212Bi, 228Ac, 208Tl), as well as technogenic 137Cs in the bottom sediments of the Tisza region in Transcarpathia (Ukraine) have been established. It is shown that the content of these radionuclides in the bottom sediments is relatively stable along the entire length of the Tisza river and is proportional to the level of its siltation, which largely depends on the morphology of the river. It was found that the total specific activity of natural gamma-active radionuclides (excluding 40K) in bottom sediments ranges from 110…139.7 Bq/kg. Areas of accumulation of gamma-active nuclides in the bottom sediments of the studied river have been identified, and the probable causes of this phenomenon have been substantiated. The averaged data of the content of specific activity of radionuclides in the bottom sediments of the Tisza river were used for mapping and forecasting of migration processes, as well as for identification of the studied sections of the river taking into account the geochemical features of the region.

Monitoring of the radionuclides and heavy metals content in the agroecosystems of the forest-steppe zone of the Central Chernozem Region of Russia

The research was carried out as part of the state agroecological monitoring program in the southwestern part of the Central Chernozem region in the Belgorod region. The soil cover of the forest-steppe zone was represented by typical chernozems. All analytical studies were carried out in an accredited testing laboratory according to generally accepted methods. The territory of the region after the accident at the Chernobyl NPP in 1986 was subjected to radioactive pollution. As a result of the studies, it was found that the average gross content of typical heavy metals in arable chernozems forms the following decreasing series (mg/kg): Mn (345) > Zn (36.5) > Cu (13.9) > Pb (10.3) > Co (8.48) > As (4.18) > Cd (0.23) > Hg (0.022). In terms of the content of mobile forms of heavy metals, the pattern is slightly different: Mn (16.7) > Pb (0.40) > Zn (0.39) > Cu (0.09) > Co (0.08) > Cd (0.05). According to the specific activity of radionuclides, they form a series (Bc/kg): 40К (530.2)>232Th (38.1)>226Ra (23.8)>137Cs (17.3). There was no excess of the standards of the approximate permissible and maximum permissible concentrations of the studied elements in the studied arable soils. The availability of arable soils with mobile forms of Zn, Cu and Co is assessed as low, in which microfertilization containing these elements is recommended to increase crop yield. In winter wheat grains, the content of the studied elements and the specific activity of the 137Cs were significantly lower than the maximum permissible levels.

Distribution of Natural Radionuclides and 137Cs in Urban Soil Samples from the City of Novi Sad, Serbia-Radiological Risk Assessment.

This work presents the natural radioactivity distribution of 21 surface soil samples taken in the city of Novi Sad, Serbia. The analysis for radioactivity was performed using a gas low-level proportional counter for gross alpha and gross beta activity, while the specific activities of radionuclides were determined using HPGe detectors. The gross alpha activity of 20 samples was below the minimum detectable concentration (MDC), while in 1 sample it was 243 Bq kg-1; the gross beta activity ranged from the MDC (11 samples) to 566 Bq kg-1. The gamma spectrometry measurements showed naturally occurring radionuclides 226Ra, 232Th, 40K, and 238U in all investigated samples, with average values (Bq kg-1) of 33.9, 36.7, 513.8, and 34.7, respectively. Natural radionuclide 235U was detected in 18 samples with activity concentrations in the range of 1.3-4.1 Bq kg-1, while in the other 3 samples, the values were below the MDC. The artificial 137Cs radionuclide was detected in 90 percent of the samples, with a maximum value of 21 Bq kg-1, while the other artificial radionuclides were not detected. Based on the obtained concentrations of natural radionuclides, hazard indexes were estimated, and radiological health risk was assessed. The results present the absorbed gamma dose rate in the air, annual effective dose, radium equivalent activity, external hazard index, and lifetime cancer risk.

Способ кислотного извлечения радионуклидов из увеличенных навесок почвы с использованием автоклавного разложения

The specifics of the nuclear tests carried out on the territory of the former Semipalatinsk test site (STS) led to the emergence of various sites that differ in levels of radioactive contamination and radionuclide composition. This also led to a significant difference in the solubility of radioactive particles. Traditionally, the “Experimental Field” testing ground was characterized by the presence of sparingly soluble, vitrified particles, which was determined by the features inherent in ground tests of nuclear weapons, namely, the interaction of the high-temperature explosion region with soil particles. The presence of such sparingly soluble particles in the soil cover makes it impossible to use 6–8 М HCl and 7–8 М HNO 3 solutions which are most often used radiochemical analysis to determine the content of 90Sr and 239+240Pu. This paper considers methods for the acid extraction of anthropogenic radionuclides from soils of the STS using autoclaving. The aim of the research is to develop a method for the acid extraction of anthropogenic radionuclides from enlarged soil samples using autoclave decomposition. A blank soil sample was used to determine the optimal autoclave decomposition parameters; to test the acid extraction method, a soil sample was taken from the territory of the “experimental field” testing ground. The radionuclide 137Cs has been used as the most optimal indicator of acid extraction due to its strong fixation on clay and mineral soil particles and ease of detection by the gamma radiation. Autoclave decomposition has been carried out by dissolving the studied samples in a mixture of mineral acids (HCl, HNO3, HF, H2SO4). The specific activity of radionuclide has been determined on a BE3830 gamma spectrometer with a high-purity germanium detector (Canberra, USA), the amount of undecomposed soil residue has been determined gravimetrically (PA214C analytical balance, Ohaus, USA). The data obtained indicate that the most complete extraction of 137Cs occurs when using concentrated HF solutions (individually or in a mixture with other mineral acids). The degree of extraction of 137Cs varied from 85 to 100%. The worst results have been shown by the use of a mixture of acids 3HCl:HNO 3. In this case the degree of extraction of 137Cs did not exceed 20%. The efficiency of decomposition of soil samples weighing 10 g with a concentrated solution of HF at a temperature of 120 to 160 ºC was ≥95%.

РЕКОМЕНДАЦИИ ПО ВНЕСЕНИЮ ИЗМЕНЕНИЙ В НРБ-99/2009 И В ОСПОРБ-99/2010

Purpose: In Russia, the main regulatory documents on radiation safety are being adjusted: Radiation Safety Standards (NRB-99/2009) and Basic Sanitary Rules (OSPORB-99/2010). The purpose of the work is to remove and correct certain incorrect provisions of these documents. Results: The disadvantages of NRB-99/2009 related to the values of the minimum significant activity and the minimum significant specific activity of radionuclides were identified and justified. In OSPORB-99/2010, the inadmissibility of introducing minimally licensed activity of radionuclides in closed sources of ionizing radiation into Sanitary Rules was identified and justified. An unacceptably large amount of this activity can lead to overexposure of personnel and the public in incidents with these sources. Conclusions: The following recommendations were made for the adjustment of NRB-99/2009 and OSPORB-99-2010: – in NRB-99/2009, it is recommended to completely remove the minimally significant specific activities, and use the minimally significant activities in accordance with NRB-76/87. – in OSPORB-99/2010, it is recommended to remove all provisions related to the minimum licensed activity of radionuclides in closed sources of ionizing radiation.

Emission Pattern of NORMs and 137Cs in the Sediments of the Gaz River and the Gorgan Bay, North Iran

Information on the distribution and emission patterns of natural and artificial radionuclides and their radiation level in the environment is very important for assessing the health effects of people living in a given region. In this study, the specific activity of radionuclides was measured using high purity germanium detector and a map of their distribution was drawn. The samples were collected from the Gaz River sediment in northern Iran, in the mountains of Golestan Province, and sediments on the middle and southern side of Gorgan Bay. The average of specific activities of 226Ra, 232Th, 40K, and 137Cs was 17.61, 35.91, 398.65, and 4.01 Bq/kg, respectively, which for natural radioactive nuclei are lower than the global average. The highest concentration of 40K was obtained in the sediments of the Gaz River estuary due to the use of potassium fertilizers for agriculture in this region. The highest concentration of 137Cs was obtained in the sediments of Gorgan Bay because 137Cs is injected both directly through the atmosphere and transfer by river water from upstream points to the Gorgan Bay. The diffusion pattern of 137Cs in the Gorgan Bay was exactly the opposite of 232Th and showed the tendency of 137Cs to precipitate in calm areas in the middle of the Bay.

Radioactivity analysis of commonly available building and flooring material in Kerala, India

Building materials are primary sources of indoor gamma radiation. Therefore, we have made a detailed study of building materials which are being used extensively in the region. Primordial radionuclides namely uranium (238U), Thorium (232Th) and potassium (40K) were studied in the building materials. As of the results acquired, we can arrive at the following inferences: We have estimated specific activities of radionuclides, the radium equivalent and radiological risk parameters resulting from the gamma originating from building materials. The highest Radium equivalent activity was obtained for red clay brick and the minimum value obtained was for M-sand. M-sand is processed sand being used widely now a days in the region. Most of the building materials were found to have very low levels of Radium. As of the results we obtained, none of the building materials were found to pose any notable radiological health hazard.

Influence of operation of thermal and fast reactors of the Beloyarsk NPP on the radioecological situation in the cooling pond: Part II, Macrophytes and fish

The influence of waste technological waters of thermal and fast reactors of Beloyarsk NPP (Russia) on the accumulation of 60Co, 90Sr and 137Cs in macrophytes and ichthyofauna of the cooling pond has been studied. Critical radionuclides, routes of their entry into the ecosystem and periods of maximum discharge of radioisotopes into the cooling pond have been determined. It is shown that the technology of electricity generation at the Beloyarsk NPP, based on fast reactors, has a much smaller effect on the release of artificial radionuclides into the environment. Therefore, during the entire period of monitoring studies (1976–2019), the decrease in the specific activity of radionuclides of NPP origin in macrophytes was 13–25800 times, in ichthyofauna 1.5-44.5 times. The maximum discharge of artificial radionuclides into the Beloyarsk reservoir was noted during the period of restoration and decontamination work aimed at eliminating the emergencies at the AMB reactors of NPP. The factors influencing the accumulation of artificial radionuclides in the components of the freshwater ecosystem of the Beloyarsk cooling pond have been determined, including: the physicochemical nature of radioisotopes, their concentration in surface water, the temperature of the aquatic environment, the trophicity of the reservoir, the species of hydrobionts.

АНАТОМО-МОРФОЛОГИЧЕСКИЙ БАЗИС ДЛЯ ДОЗИМЕТРИЧЕСКОГО МОДЕЛИРОВАНИЯ ТРАБЕКУЛЯРНОЙ КОСТИ ЧЕЛОВЕКА С ИСПОЛЬЗОВАНИЕМ СТОХАСТИЧЕСКОГО ПАРАМЕТРИЧЕСКОГО ПОДХОДА

Purpose: To create an anatomical and morphological basis for a Stochastic Parametric Skeletal Dosimetric model (SPSDmodel) for a human of different age, which includes an assessment of the parameters of the trabecular bone microstructure in the hematopoietic regions of the human skeleton. The model is necessary to estimate the doses to red bone marrow from osteotropic radionuclides (89,90Sr). The model is being created as a part of the dosimetric support for epidemiological studies of the South Ural cohorts, the members of which lived in territories radioactively contaminated in the 1950s. Materials and methods: Estimation of model parameters is based on the collection and analysis of published data. The selection of publications was made using Internet search engines: Google, PubMed, Academia, e-library, etc. Original articles in peerreviewed publications were selected, atlases, manuals, monographs and dissertations were considered. Information was collected only on healthy individuals. The collected data reffered to the following parameters of the trabecular bone: trabecular thickness, intertrabecular space, the proportion of bone in the total tissue volume. The parameters were assessed using histomorphometry and micro-CT. To make a decision about bone modeling, the data on a hematopoietic activity in it, obtained by MRI and PET, were considered. Result: Based on the results of the analysis of published information, primary data files were generated containing bibliographic data on the source of information, data on the subjects of the study and the measurement results of trabecular bone parameters. On this basis, average population estimates of the parameters were obtained and their variability (standard deviation, coefficients of variation) was estimated. Data on the duration of hematopoiesis in various parts of the skeleton and data on age-related changes in the microstructure were analyzed. The paper presents a description of a full set of parameters of the SPSD model of trabecular bones for newborns, children aged 1, 5 and 10 years, as well as for adolescents aged 15 years and adults. Conclusion: The obtained numerical values are used as input data (parameters) for generating dosimetric phantoms in voxel form. Our results will make it possible in the future to calculate conversion factors that relate the specific activity of radionuclides in the source tissue (bone trabeculae) to the dose rate in the detector tissue (red bone marrow), as well as the uncertainty of their estimates.

Экологические особенности накопления радионуклидов компонентами наземных экосистем зоны отчуждения

The studies were carried out 30 years after the Chernobyl accident on the lands of the former land use subject to natural successional changes. The patterns of the lateral distribution of 137Cs, 90Sr, 241Am in the upper 20-cm soil layer of various biogeocenoses, including those depending on the height fluctuations of the relief, have been studied. The values of the coefficient of variation (V) of the content of radionuclides in the upper soil layer decrease with the time that has passed since the accident. The highest value of the coefficient of variation (75.2 %) was obtained for 90Sr in the soil in the pine forest. The influence of various soil conditions on the entry of radionuclides into birch sap, cap mushrooms, and meadow grasses was studied. Despite the significant excess of the density of soil contamination with 137Cs of all the studied communities (up to 9.1 times), its volumetric activity in the juice is significantly lower than 90Sr, which indicates a lower availability of 137Cs compared to 90Sr. Dynamic processes of accumulation of radionuclides during the entire period of the movement of sap are studied. With increase in extent of moistening of the soil, accumulation of radionuclides in mushrooms tends to decrease. At the same time differences between types is established that connected with feeding habits of mushroom and variability of microclimatic conditions. The effect of soil moisture content, the ratio of 137Cs mobility forms in the soil on the biological availability of the radionuclide by meadow grasses was studied. A decrease in the specific activity of radionuclides in the plant components of ecosystems was found as the phytocenoses moved away from the epicenter of the accident at an identical density of soil contamination. A relationship has been established between the accumulation of radionuclides and the agrochemical parameters of the soil: maintenance of humus, absorption capacity, cation exchange capacity, hydrolytic acidity, content of exchange phosphorus, concentration of mobile calcium, magnesium and potassium on post-agrogenic lands. The analysis of the soil-to-plant transfer factors (Cf) and aggregated transfer factors (Tag), the discrimination coefficient (DF) of 137Cs by a chemical analog element (potassium) was carried out. Species features of plants associated with the transport of K+ - Cs+ cations make significant adjustments to the mechanisms of 137Cs accumulation. Attention is drawn to the significant increase in the concentration of 90Sr in all components in recent years.

Radionuclide activity in cryoconite from glaciers of the Central Caucasus, Russia

This work presents the results of a study of radionuclide activity in cryoconite from glacier and glacial soil of the Central Caucasus. Cryoconite were sampled from the surface of the Garabashi glacier, and soil samples were taken from the humus horizon of periglacial mountain forest-meadow soil. Measurements were performed with low-background germanium gamma spectrometers located inside a passive shield consisting of ∼20 cm of copper, ∼15 cm of lead, and ∼8 cm of borated polyethylene. The specific activity of radionuclides (Be-7, K-40, Th-232, U-235, U-238, Cs-137) was established. It was revealed that all measured spectra contain γ-lines from decays of K-40, decay chains of U-238, U-235 and Th-232. In addition, the spectra of cryoconite samples from the Garabashi glacier show a 477.6 keV line from the decay of the cosmogenic isotope Be-7, and in the soil sample a 661.7 keV line from the radionuclide Cs-137. No radionuclide Be-7 was detected in the mountain forest-meadow soil. Radionuclide Cs-137 is present in the soil sample, while in cryoconite, is not detected. Radioisotope activities in the Garabashi glacier cryoconite, except for the cosmogenic isotope Be-7, do not differ significantly in terms of mass, i.e., the content of K-40, U-238, U-235 and Th-232 in them is approximately the same. The activity of all the studied radionuclides in the soil sample compared to cryoconite samples is lower, although the differences are not significant, except for Th-232, whose activity in soil is almost two times lower.

Radiation exposure and risk assessment to earthworms in areas contaminated with naturally occurring radionuclides.

The assessment of radiation exposure on biota is one of the main parts of environment protection system. Earthworms have been recognized as an important organism group in the terrestrial ecosystems. According to many researchers the potential risks of naturally occurring radionuclides for soil invertebrates were not significant because the exposure doses to the invertebrate populations were low. Our study aimed to assess the radiation exposure and the radiological risks from naturally occurring radionuclides for earthworm populations at four sites. This research was based on three dosimetric approaches simultaneously: ERICA and RESRAD-BIOTA-the commonly used ones, and also on the original method proposed by Thomas and Liber (Environment International, 27, 341-353,2001) for aquatic organisms. To calculate radiation dose rates to soil invertebrates inhabiting background and contaminated areas, the specific activities of radionuclides in soil, and, depending on the model, the default, or determined in this study, input mass-geometric parameters had been applied. The weighted absorbed dose rates calculated by different models and site-specific data were 0.3-1.4μGy/h for the background and from 3.4 to 170μGy/h for the contaminated sites. Analysis of radiation risks for earthworms indicated that 226Ra was the key contributor to the external dose rate; 226Ra and 210Po played a dominant role in formation of internal dose rate for radioecological situations in our study. More conservative radiation risk assessments were derived from RESRAD-BIOTA tool. Dose assessments obtained using various models had shown that there are real environmental situations in which the radiological risks to reference organisms are significantly higher than the lowest benchmark protection level proposed for ecosystems.