Artificial Radionuclides Research Articles

Comparison of 14C and 210Pb - 137Cs - 241Am dating methods of a recent bat guano deposit (Lot, SW France)

Bat guano deposits are increasingly used as records of past environmental changes, an approach that requires a precise chronology of the guano layers. This paper presents a comparison between the well-established 14 C dating method and methods based on natural 210 Pb excesses, ( 210 Pb) ex , and artificial radionuclides 137 Cs and 241 Am. The studied example is a bat guano deposit from a cave in SW France (the Brantites III cave), which is currently investigated for paleo-environmental reconstructions using stable isotopes. 14 C data show that the upper part of the guano deposit accumulated during the last 150 years with a marked increase in accumulation rates after around 1960 AD. While the incorporation of atmospheric 14 C in guano is a well-understood process, the origin of 210 Pb excesses is more complex. Based on consideration of 137 Cs and ( 210 Pb) ex inventories recorded in undisturbed soils in France, and the measured inventories in the guano deposit, we suggest that most of the 210 Pb excess is produced by 222 Rn decay in the cave air and then adsorbed onto the guano. As Radon concentrations in caves can vary significantly on both short and long-term timescales, one needs to be cautious before applying the often-used CRS (constant rate of supply of 210 Pb excess) model to guano dating. Our ( 210 Pb) ex data are best interpreted by two successive periods of roughly constant, but widely different accumulation rates (0.3 cm/y and 2.6 cm/y before and after 1960, respectively) and ( 210 Pb) ex fluxes. We suggest that these relatively abrupt variations result from a change in cave ventilation leading to a more favourable shelter for bats after 1960. The upper 40 cm of the deposit shows evidence of 210 Pb mobility, adding a further complexity to the interpretation of ( 210 Pb) ex profiles in guano deposits. However, the existence of well-defined 137 Cs and 241 Am peaks allows a precise identification of the year of maximum atmospheric fallouts (∼1963–1964). When the ages provided by artificial radionuclides are combined with the 210 Pb-derived accumulation rates, an age model can be built, which is in good agreement with the 14 C age model. This example shows that the ( 210 Pb) ex method, when associated with 137 Cs ( 241 Am) data, can be used to date recent guano deposit, although its application is not as straightforward as the 14 C method.

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.

Distributions of Radiocesium and Plutonium in the Korean Seas and North Pacific after the Fukushima Accident, 2011–2014

The distributions of artificial radionuclides, radiocesium (134Cs and 137Cs) and plutonium isotopes (238Pu and 239+240Pu), in the surface water around the Korean seas (East/Japan Sea and Yellow Sea) in 2011–2012 and in three sections in the North Pacific between 2011 and 2014 were examined. The 137Cs activities in the surface water in the Korean seas in 2011 (immediately after the Fukushima nuclear power plant (NPP) accident on 17 March 2011) were comparable or not significantly different relative to those in 2010 and 2012. However, 134Cs, which had been not detected in the study area before the Fukushima accident (under the detection limit of 0.1 mBq kg−1 level), were detected rapidly in 2011 after the accident (in about 60% of the 72 samples) and gradually disappeared due to their short half-life (t1/2 = 2.06 years) in 2012 (detected in about 16% of the 24 samples). In addition, the highest activities of radiocesium and Pu isotopes appeared locally in some stations of the Korean Strait region (located between Korea and Japan) within 1–2 months immediately after the accident. This suggests that the radioactive nuclides released immediately after the Fukushima accident were significantly introduced through the atmosphere, based on recent studies conducted in neighboring areas. We also showed that the spatial distribution of radiocesium in the North Pacific moved eastward from 2012 to 2014, and we attempted to quantify the residence time of radiocesium (137Cs) in the Korean seas based on the long-term (tens of years scale) temporal trends of 137Cs activity data, which have been collected since the 1960s and 1970s. The estimated retention time of 137Cs in the East/Japan Sea and Yellow Sea were 25 ± 0.6 and 8.0 ± 0.1 years, respectively. These results are expected to be used as a preliminary study for a potential future event of a marine radioactive accident (which, of course, cannot be predicted) and as basic data for predicting the influences of radionuclide releases in the ocean.

In Depth Analysis of a Sediment Core from North Aegean Sea

In this work a thorough analysis of the vertical distribution of natural and artificial radionuclides and trace elements in a sediment core sample was conducted. A sediment core of 39 cm length was grabbed from the deep-sea trench (1540 m depth) southern of Samothrace Island, Aegean Sea. The sediment core was then treated at the Hellenic Centre for Marine Research, separated at 1cm increment samples, ranging from 0cm to 39 cm, dried, and milled. A first analysis of the samples was also conducted at HCMR using gamma spectroscopic techniques. Further spectroscopic analysis continued at Nuclear Engineering Department of the National Technical University of Athens (NED-NTUA) using an Extended Range Germanium Detector. The following radionuclides were determined 210Pb, 234Th, 226Ra, 228Ra, 228Th, 137Cs and 40K. Additionally, Instrumental Neutron Activation Analysis was used and the following major and trace elements were identified and quantified: Al, V, La, Sc, Mn, As, Ga, Cr, Zn, Co, Rb, Fe, K, Na and Ce. Based on the analysis of each sample, the vertical distribution of most natural radionuclides showed no significant variation. The vertical distribution of anthropogenic 137Cs was very low and almost constant. Unsupported 210Pb activity was about six times higher than 226Ra, indicating high radon fluxes. Furthermore, neutron activation analysis results indicate that almost all elements are within the expected range based on literature, while K and Na show a slightly increased concentration. For the area, these findings indicate steady and calm sedimentation processes.

Spectral unmixing of multi-temporal data in gamma-ray spectrometry

A challenging problem in gamma-ray spectrum analysis is the rapid detection of artificial radionuclides at low activity levels. Until now, traditional methods focus on activity estimation based on single spectra, obtained by integrating over time the measured disintegration events. However, accounting for the well-constrained radionuclides decay should allow for a more accurate and sensitive activity estimation. For that purpose, we investigate a novel approach to estimate radionuclides’ activity, which is (i) first based on multi-temporal data, obtained from several short measurements rather than a single one, and (ii) built upon a dedicated spectral unmixing, which allows processing multi-temporal data. The proposed algorithm allows accounting for both the full spectrum of each radionuclide (i.e. peaks and Compton continuum) and their activity decay in time. To that purpose, different approaches are investigated to model the temporal dependencies of the radionuclides’ activities, and specifically to account for potentially out of equilibrium radionuclides’ decay chains. Experimental results on both simulated spectra and real measurements are presented and compared to standard methods, it is shown that the proposed approach leads to more accurate estimations and faster detection of artificial radionuclides.

Analysis of the Activities of the Website “Question and Answer about Radiation in Daily Life” after the Accident at the Fukushima Daiichi Nuclear Power Plant and Some Lessons Learned from It: To Pass on This Experience to the Future

After the accident at the Fukushima Daiichi Nuclear Power Plant, artificial radionuclides such as radioactive cesium and iodine were released into the environment. It caused great anxiety not only in the vicinity of the Fukushima Daiichi Nuclear Power Plant but also in other regions of the world. Some members of the Japan Health Physics Society (JHPS), a leading academic society in Japan in the field of radiation protection, volunteered to establish a website called “Question and Answer (Q&A) about radiation in daily life” shortly after the accident to help reduce the residents’ anxiety about the health effects of radiation. In August 2011, “Committee for Q&A about radiation in daily life” was established in JHPS, making the website-related activities a responsibility of JHPS. The Q&A website continued to respond to the questions from the general public with expertise and sincerity until February 2013 when the Committee members decided to end the activities because the number of questions received had gradually decreased with the passage of time. This paper aims to introduce the following: the activities of the Q&A website during the two years (2011–2013), the stance chosen for the activities, the information related to the website activities and the analysis of Twitter data. Building on the experience and the knowledge obtained from the activities, it also discusses issues and experiences that can be utilized in the initial response to emergencies for radiation protection experts as well as those in other fields.

Bioactive and radioactive properties of some edible wild Lactarius mushrooms

Lactarius delicious, Lactarius insulsus, Lactarius vellereus mantarlarının biyoaktif ve radyoaktif özellikleri araştırılmıştır ve bu amaçla Kastamonu ilinden toplanan mantarların protein ve toplam fenolik madde miktarları, antioksidan ve antimikrobiyal özellikleri belirlenmiştir. Ayrıca mantarlardaki bazı eser element (Mg, Al, Ca, Mn, Fe, Co, Ni, Cu, Zn, Se, As, Cr, Cd) miktarları, kurşunun üç izotopu (206Pb, 207Pb and 208Pb), doğal (238U, 232Th 40K) ve yapay radyonüklit (137Cs) seviyeleri de hesaplanmıştır. Mantarlar arasında; L. delicious, daha yüksek protein içeriği ve Mg, Ca, Mn, Fe, Co, Ni, Zn, Pb-206, Pb-208, Cr birikimleriyle dikkat çekmiştir. En yüksek toplam fenolik içerik ve antioksidan aktivite L. vellereus’da bulunmuştur. Bunlara ek olarak; en yüksek 232Th ve 40K radyonüklid içeriği de L. vellereus’ta belirlenmiştir. Yapay radyonüklid (137Cs) sadece L. insulsus mantarında gözlenmiştir. Sonuç olarak, aynı cinsten olmalarına ve aynı bölgeden toplanmalarına rağmen farklı mantar türlerinin farklı biyoaktif ve radyoaktif özelliklere sahip olduğu görülmüştür.

Artificial Radionuclides in the System: Water, Irrigated Soils, and Agricultural Plants of the Crimea Region

In the frame of the radioecological monitoring after the Chernobyl nuclear power plant accident, the features of migration and distribution of artificial radionuclides in the North Crimean Canal (NCC) irrigation system were studied. Standard methods of radiochemical analyzes and modern radiospectrometric equipment were used. It was determined that the irrigation system of the NCC retains 43–59% 90Sr, 59–60% 239+240Pu, and 66–70% 137Cs of the concentration radionuclides entering to irrigated fields with the Dnieper waters. The NCC irrigation system plays the role of a buffer against the radionuclide pollution of the Karkinitsky Bay (the Black Sea). Differences in the accumulation of radionuclides by agricultural crops were revealed. The 90Sr and 239+240Pu transfer factors (TF) for alfalfa were n × 10−2 and n × 10−1, respectively. The TF for wheat, corn, and rice for 90Sr were n × 10−3, and for 239+240Pu—n × 10−2. A radioecological assessment on the safety agriculture along the NCC was made: in the absence of an increase in the entry of the Chernobyl origin radionuclides with the Dnieper river waters to the NCC, the levels of activity concentration of artificial radionuclides in cultivated crops will not exceed the maximum permissible concentration for food raw materials in the coming years.

PET plastics as a Trojan horse for radionuclides

Mismanaged plastic waste interacts with secondary environmental pollutants, potentially aggravating their impact on ecosystems and human health. Here we characterized the natural and artificial radionuclides in polyethylene terephthalate (PET) bottles collected from the industrial littoral discharge of a phosphate fertilizer plant. The activity concentrations in littered bottles ranged from 0.47 (208Tl) to 12.70 Bq·kg-1 (226Ra), with a mean value of 5.30 Bq·kg-1. All the human health risk assessment indices (annual intake, annual effective dose, and excess lifetime cancer risk) estimated for radionuclides associated with ingestion and inhalation of microplastics were below international safety limits. Our results demonstrated that PET can be loaded with natural and artificial radionuclides, and potentially act as a carrier to transfer radionuclides to humans, posing a new potential health risk. Increased use, mismanagement and fragmentation of plastic waste, and continued interaction of plastic waste with radioelements may lead to enhanced radiation exposure in the future.

The Sedimentation Rate in the Crimean Hypersaline Lake Aktashskoye Estimated Using the Post-Chernobyl Artificial Radionuclide 90Sr as a Radiotracer

Artificial 90Sr is one of the most important long-lived radionuclides of global radioactive fallout from the atmosphere after the testing of nuclear weapons and the accident at the Chernobyl Nuclear Power Plant in 1986. In addition to fallout from the atmosphere, secondary radioactive contamination of Crimea was mainly from the Dnieper River and the North Crimean Canal, which occurred until 2014. 90Sr was used as the optimal radiotracer for estimating the rate of sedimentation in the Crimean hypersaline lake. Its vertical distribution in the bottom sediments was assessed. In the core of the bottom sediments, the detectable activity of 90Sr in layers 0–1.5 cm and 16.7–21.9 cm was absent, and it was determined again in the layer of 15.5 cm, which was associated with atmospheric fallout of the radionuclide after the Chernobyl NPP accident. There were well-isolated peaks of specific activity in layers at a depth of 4.6 and 13.3–14.3 cm. The calculated rate of sedimentation varied within 0.5–1.5 cm year−1: the minimum rate corresponded to the period 1971–2017, and the highest rate corresponded to the period 1954–1971.

Database of virtual spectrum of artificial radionuclides for education and training in in-situ gamma spectrometry

As the field of application of in-situ gamma spectroscopy is diversified, proficiency is required for consistent and accurate analysis. In this study, a program was developed to virtually create gamma energy spectra of artificial nuclides, which are difficult to obtain through actual measurements, for training. The virtual spectrum was created by synthesizing the spectra of the background radiation obtained through actual measurement and the theoretical spectra of the artificial radionuclides obtained by a Monte Carlo simulation. Since the theoretical spectrum can only be obtained for a given geometrical structure, representative major geometries for in-situ measurement (ground surface, concrete wall, radioactive waste drum) and the detectors (HPGe, NaI(Tl), LaBr3(Ce)) were predetermined. Generated virtual spectra were verified in terms of validity and harmonization by gamma spectrometry and energy calibration. As a result, it was confirmed that the energy calibration results including the peaks of the measured spectrum and the peaks of the theoretical spectrum showed differences of less than 1 keV from the actual energies, and that the calculated radioactivity showed a difference within 20% from the actual inputted radioactivity. The verified data were assembled into a database and a program that can generate a virtual spectrum of desired condition was developed.

Calibration of an airborne γ-ray spectrometer based on an unmanned aerial vehicle using a point source

Due to the lack of physical calibration models of artificial radionuclides for airborne γ-ray spectrometers, it is difficult to accurately deduce the content of artificial radionuclides on the ground based on airborne γ-ray spectrometry. According to the airborne radiation monitoring standard of the International Atomic Energy Agency (IAEA) and domestic and foreign industry experience, a calibration method for an airborne γ-ray spectrum survey system (AGS) based on an unmanned aerial vehicle (UAV) using point source is proposed in this paper. After calibrating the system with general methods and obtaining satisfactory test results, four artificial radioactive point sources were selected to calibrate the developed AGS and then obtain the calibration parameters for these point sources. Based on the calibration parameters of these four radionuclides, the calibration parameters of other artificial radionuclides can be estimated to realize the function of quantitative measurement of artificial radioactive sources by the AGS based on UAVs.

Radiological hazard assessment of natural radioactivity in Avcilar region, Turkey: a case of Istanbul University-Cerrahpasa Avcilar Campus

ABSTRACT Radionuclides 226Ra, 232Th, and 40K can be found in various concentrations in the surface soil. High concentrations of radionuclides in the surface soil may cause radiological risks. This study investigated natural radioactivity levels and artificial radionuclide (137Cs) levels in the Istanbul University-Cerrahpasa, Avcilar region, Istanbul, Turkey. Radioactivity concentrations were analyzed using the gamma-ray spectrometer. The mean activity concentration of 226Ra, 232Th, 40K, and 137Cs is 28.55, 29.57, 385.72, and 3.09 Bq kg−1, respectively. Radiological parameters radium equivalent activity, absorbed dose rate, annual effective dose equivalent, external hazard index, and excess lifetime cancer risk were calculated using activity concentrations. The radiological parameters values were lower than UNSCEAR values, except for the annual gonadal dose equivalent (approximately 10% higher). There is a strong correlation between radiological parameters and radionuclides. Generally, the activities of radionuclides in the region fall within the recommended limits, thus Istanbul-Avcilar region can be considered safe for settlement.

Accumulation of 137Cs by Thallus of Epiphytic Lichen Hypogymnia physodes (L.) Nyl on Different Trunk Height in Pine Stands

Lichens are considered by researchers as bioindicators of environmental pollution by artificial radionuclides, including 137Cs. One of these bioindicator species is epiphytic lichen Hypogymnia physodes (L.) Nyl, the use of which for radioecological monitoring can be modified by several factors: tree species, placement on the tree (branches – trunk), height of sampling, etc. The purpose of this study was to investigate the specific activity of 137Cs in thalli of hypogymnia in pine stands: on trunks of Pinus sylvestris L. and Betula pendula Roth at different heights of sampling in 3 height ranges: 0–65, 65–130, and 130–195 cm, and to analyse the intensity of radionuclide accumulation in the “lichen thallus – tree bark” link for both tree species in all height ranges. The study was conducted in August 2021 in the Korosten district of the Zhytomyr Oblast, Zhytomyr Polissia, on 4 test plots, in the Drevlianskyi nature reserve, mainly in middle-aged pine stands with an admixture of birch, where 130 samples of soil, tree bark, and lichen were taken. Specific activity of 137Cs in the samples was measured using a SEG-001 “AKP-s”-150 gamma-ray spectrometer with a BDEG-20R2 scintillation detector (NaI(Tl). It was demonstrated that the content of 137Сs in the thalli of Hypogymnia physodes at different altitude ranges did not differ statistically significantly at the 95% confidence level in all test plots on pine. A preliminary conclusion was made on the possibility of sampling Hypogymnia physodes thalli on pine trunks in the height range of 0–195 cm; however, for the convenience of sampling, it is recommended to perform sampling within 130–195 cm. It has been proven that both the specific activity of 137Сs in Hypogymnia physodes thalli and the intensity of 137Сs accumulation in the chain “Hypogymnia physodes - tree bark” are approximately 2 times higher on pine compared to birch. It was found that on a birch, the content of 137Сs in lichen between the height ranges of 0–65 and 65–130 cm, and 0–65 and 130–195 cm differs significantly at the 95% confidence level; therefore, it is recommended to sample Hypogymnia physodes on a birch in the range of 65–130 cm.

Radiation monitoring of foodstuffs and drinking water in the vicinity of the Rooppur Nuclear Power Plant (People’s Republic of Bangladesh)

The system of radiation monitoring of local foodstuffs and drinking water in the settlements of the area of the Rooppur Nuclear Power Plant was developed. An analysis of the results of a 4-year (2014–2017) cycle of studies on the assessment of the specific activity of natural (40K, 226Ra, 232Th) and artificial (90Sr, 137Cs) radionuclides in the components of the diet of the population of the 30-km zone of influence of the nuclear power plant is presented. Thus, the specific activity of the most radiologically significant 137Cs in cow's milk averages 0.05 Bq.L−1, beef − 0.14, poultry − 0.09, and fish − 0.15 Bq.kg−1. In cereals, the 137Cs content varies in the range 0.2–0.6, vegetables 0.03–0.11, fruits 0.05–0.1 Bq.kg−1 and is determined by the species characteristics of crops. It was noted that 90Sr accumulates in food products to a greater extent than 137Cs. In livestock production, this difference is 1.2–6.8 times, fish 1.5 times, grain 1.2–4.2, vegetables 1.5–8.2, fruits 1.8–5.8 times. In drinking water, the specific activity of 137Cs is at the level of 0.05, 90Sr − 0.03, 3H − 1.3 Bq.L−1. The coefficients of accumulation of 90Sr and 137Cs in foodstuffs of animal and plant origin have been calculated.

An In-Depth Examination of the Natural Radiation and Radioactive Dangers Associated with Regularly Used Medicinal Herbs.

The specific activity of U-238 and Th-232, as well as K-40 radionuclides, in twenty-nine investigated medicinal herbs used in Egypt has been measured using a high-purity germanium (HP Ge) detector. The measured values ranged from the BDL to 20.71 ± 1.52 with a mean of 7.25 ± 0.54 (Bq kg−1) for uranium-238, from the BDL to 29.35 ± 1.33 with a mean of 7.78 ± 0.633 (Bq kg−1) for thorium-232, and from 172 ± 5.85 to 1181.2 ± 25.5 with a mean of 471.4 ± 11.33 (Bq kg−1) for potassium-40. Individual herbs with the highest activity levels were found to be 20.71 ± 1.52 (Bq kg−1) for uranium-238 (H4, Thyme herb), 29.35 ± 1.33 (Bq kg−1) for thorium-232 (H20, Cinnamon), and 1181.2 ± 25.5 (Bq kg−1) for potassium-40 (H24, Worm-wood). (AACED) Ingestion-related effective doses over the course of a year of uranium-238 and thorium-232, as well as potassium-40 estimated from measured activity concentrations, are 0.002304 ± 0.00009 (minimum), 0.50869 ± 0.0002 (maximum), and 0.0373 ± 0.0004 (average)(mSv/yr). Radium equivalent activity (Raeq), annual gonadal dose equivalent (AGDE), absorbed gamma dose rate (Doutdoor, Dindoor), gamma representative level index (I), annual effective dose (AEDtotal), external and internal hazard index (Hex, Hin), and excess lifetime cancer risk were determined in medicinal plants (ELCR). The radiological hazards assessment revealed that the investigated plant species have natural radioactivity levels that are well within the internationally recommended limit. This is the first time that the natural radioactivity of therapeutic plants has been measured in Egypt. In addition, no artificial radionuclide (for example, 137Cs) was discovered in any of the samples. Therefore, the current findings are intended to serve as the foundation for establishing a standard safety and guideline for using these therapeutic plants in Egypt.

Study of radionuclides and heavy metal migration through soil profiles (0-60cm) at points near the targets of NATO strikes in 1995: environmental monitoring and assessment.

The activity concentrations of natural and artificial radionuclides (40K, 232Th, 226Ra, 238U, 137Cs) and concentrations of six heavy metals of interest (Cd, Cr, Cu, Ni, Pb and Zn) were investigated in 18 soil samples through soil depths (0-10, 10-20, 20-30, 30-40.40-50, 50-60cm) at the three selected sites in the Hadžići. Since at this area ammunition with depleted uranium had been used during the NATO strikes in 1995, this study was conducted with the aim to assess the radiological and environmental health hazards. Radioactivity was determined by gamma spectrometry using HPGe and LEGE detectors and content of heavy metals by using a flame atomic absorption spectrometry. The correlation with distribution of the radionuclides and their activity concentrations through depths was found only at the site 1 for 40K, 232Th and 226Ra, where minimum/maximum activity concentrations for 40K were 814.42Bq/kg/1039.48Bq/kg, for 232Th 53.98Bq/kg/74.12Bq/kg and for 226Ra 50.32Bq/kg/65.73Bq/kg. Vertical distribution of 137Cs along 3 site profiles was used for distinction of cultivated and uncultivated soil. Using the activity ratio of 238U/226Ra and 235U/238U, the presence of depleted uranium (DU) was established at the site 3. Obtained Igeo values for determined heavy metals showed that all of three sites were unpolluted to moderately polluted. Pb content in all three sites showed correlation with concentration decreasing with increasing soil depth.

МИГРАЦИЯ ТЕХНОГЕННЫХ РАДИОНУКЛИДОВ (137CS, 152EU, 60CO) В ДОННЫХ ОТЛОЖЕНИЯХ Р. ЕНИСЕЙ (БЛИЖНЯЯ ЗОНА ВЛИЯНИЯ КРАСНОЯРСКОГО ГХК)

The distribution nature of the artificial gamma-emitting radionuclides (137Cs, 152Eu, 154Eu, 155Eu, 60Co) in vertical columns of the Yenisei River bottom sediments selected in the near zone of influence of the Krasnoyarsk MCP was revealed. It is shown that the mineral composition of bottom sediments does not change with the depth and is mainly represented by quartz, plagioclase and potassium feldspar, with a small amount of amphibole, chlorite, mica. It was found that the exchangeable and carbonate forms contain, on average, 16% of 152Eu, 22% of137Cs and 15% of 60Co being found in bottom sediments. Radionuclides presented in these forms can pass into an aqueous solution and be involved in secondary migration under stable, natural conditions. Other fractions of the absorbing complex in the absence of catastrophic changes in physico-chemical conditions in the river ecosystem do not pass into an aqueous solution, and the redistribution of radionuclides associated with them can occur only with mechanical transfer of the matter.

A practical and general methodology for efficiency calibration of coaxial Ge detectors

The correct determination of artificial and natural radionuclides like 152Eu, 137, 134Cs, 60, 57Co, etc., and 234, 228Th, 228, 226Ra, 210Pb and 40K, respectively, is essential for many environmental science fields. For this, a general function was obtained for the full-energy peak efficiency (FEPE) by gamma-ray spectrometry using coaxial Ge detectors. Then, the experimental FEPE values, obtained fixing the energy, Eγ, were fitted varying the thickness, h, of cylindrical standards. The parameters resulted from these fittings were fitted, in turn, versus Eγ, obtaining a general efficiency function, εc (Eγ, h). εc (Eγ, h) was validated, obtaining very good zscore, except for Eγ affected by TCS effects. Consequently, a practical and general method was developed, recalibrating the detector by varying the sample-detector distance, d. εc (Eγ, h, d) was obtained, achieving very good zscore. Furthermore, this practical method was also employed to correct high self-absorptions and high dead times.

Speciation of 137Cs, 90Sr, 241Am, and 239+240Pu artificial radionuclides in soils at the Semipalatinsk test site

This paper reports the speciation of 137Cs, 241Am, 90Sr and 239+240Pu in the soil samples of the Experimental Field (EF). The EF is a testing ground of the Semipalatinsk nuclear weapons test site used for surface and atmospheric tests. The study revealed low mobility of artificial radionuclides in the EF site soils.The revealed high radionuclide concentrations in soil mainly exist in tightly bound form. On average, the content of the tightly bound form of 137Cs was revealed to be below 98%, that of 90Sr - 94%, 241Am - 89%, and 239+240Pu - 98%.The radionuclides occurrence forms were analyzed in correlation with the physicochemical parameters of soils. Reliable relationships have been established between the content of carbonates and the content of the exchangeable, acid-soluble and strongly bound 90Sr forms in soils, as well as the content of the water-soluble salts and the content of the strongly bound 239+240Pu form in the soil.Similarly, we compared the distributions of the radionuclides speciation and their stable isotopes with their analogous elements in the soil. Unlike 137Cs and 90Sr, which are in a tightly bound form in the soils of the Experimental Field site, the main content of soil “competitors” of the 137Cs radionuclide – K and Cs is observed in an exchange form, less significantly in an acid-soluble form. The alkaline earth metals (analogous elements for 90Sr) are mainly observed as a composition of the exchangeable and acid-soluble forms. The results allow to conclude that there is no equilibrium distribution of the physicochemical forms of radionuclides introduced into the soil and the natural presence forms of their stable analogs in the soil. Such equilibrium distribution can only be achieved at a complete isotopic exchange in phases and soil components, which under the conditions of the Experimental Field is not possible in the near future.It can be concluded that the behavior of the studied radionuclides in soils is stipulated by the initial form delivered by the fallouts from tests at the EF site.