Cs Isotopes Research Articles

Preliminary Study of Cesium Immobilization in a Geopolymer Matrix

Geopolymers are modern synthetic materials that have many beneficial characteristics, e.g. excellent mechanical properties, fire- and heat-resistance, minimal shrinkage and can be molded into shape. Given their aforementioned characteristics, geopolymers could be applicable as conditioning materials, e.g. to handle hazardous waste and radioactive materials. However, their long-term applicability needs to be investigated.The aim of this study is to investigate the mobility of Cs-137 radionuclides in embedding materials. Different geopolymeric matrices - namely kaolinite, bentonite, zeolites and red mud - were tested. The leach test was performed according to the ASTM C1308-08(2017) standard and the activity concentration of Cs-137 isotopes was measured by gamma spectrometry using a high-purity germanium (HPGe) semiconductor detector. According to our preliminary results, the matrices that resulted in the most significant immobilization effect were those in which bentonite, cement, fly ash and 8M NaOH were used, releasing approximately 10% of the cesium.

Sedimentation on the Siberian Arctic Shelf as an indicator of the arctic hydrological cycle

Siberia occupies a significant part of the Eurasian continent and environmental changes in this region can have an important impact on the climate system of the Northern Hemisphere. The sediment flux of Siberian rivers is sensitive to changes in physical, chemical, and biological processes taking place on the continent, and these changes can be recorded in marine sediments on the Siberian Arctic Shelf. This paper presents data on grain-size distribution of the sediments, the sedimentation rates, and the mass accumulation rates on the shelf over the past 100 years. Age models are based on the decay rate of excess lead isotope 210Pb, taking into account the sorption capacity of the marine sediments, and the presence of cesium isotope 137Cs peaks in the sediment cores. The highest sedimentation and mass accumulation rates were observed prior to the 1920–40 and coincide with larger particle sizes, indicate a period of active sediment-laden sea ice and iceberg melt. Systematic decrease in the sedimentation and mass accumulation rates against the background of an increase in the proportion of silt fractions in the shelf sediments in the second half of the 20th century can be explained by an acceleration of the arctic hydrological cycle.

Detection of 135Cs &137Cs in environmental samples by AMS

The detection of low abundances of 135Cs in environmental samples is of significant interest in different fields of environmental sciences, especially in combination with its shorter-lived sister isotope 137Cs. The method of Ion–Laser InterAction Mass Spectrometry (ILIAMS) for barium separation at the Vienna Environmental Research Accelerator (VERA) was investigated and further improved for low abundance cesium detection. The difluorides BaF2− and CsF2− differ in their electron detachment energies and make isobar suppression with ILIAMS by more than 7 orders of magnitude possible. By this method, samples with ratios down to the order of 135,137Cs/133Cs ≈10−11 are measurable and the 135Cs/137Cs ratios of first environmental samples were determined by AMS.

Estimation of radioactive activity by gamma spectroscopy

Radioactive sources of isotopes 22Na, 137Cs, 60Co, 133Ba and decay chains of Th and U are analyzed by means of gamma spectroscopy. The instrument used, a cylindrical NaI(Tl) scintillator from Mirion Technologies (Canberra) with dimensions of 2 × 2, is characterized by its calibration and absolute efficiency. The peak energies of the gamma spectra obtained are identified and related to corresponding isotopes and matter-radiation interactions according to nuclear and atomic databases. From these data, spectroscopic methods are implemented to compute radioactive activities for each source.

Structure and gamma-ray attenuation capabilities for eco-friendly transparent glass system prepared from rice straw ash

The current study investigates the physical structural and radiation shielding capabilities of a newly developed glass system incorporating silica extracted from rice straw ash (RSA). The purity and chemical composition of the silica are determined using XRF. XRD confirms the amorphous character of the synthesized glass. Moreover, molar volume, optical parameters, and density will be investigated. Gamma (γ)-rays shielding parameters like half-value layer, mass attenuation coefficient, the effective atomic number, and the mean free path are experimentally measured across a broad range of gamma-ray energies (81 keV–1408 keV) emitted from 152Eu, 133Ba, 137Cs, and 60Co radioactive isotopes. The exposure buildup factor will be evaluated with the geometric progression fitting approximation. In addition, Phy-X/PSD software is used to calculate theoretically the former shielding parameters. A good agreement between theoretical and experimental values has been revealed. Finally, a comparison was made to investigate the potential use of our glass to replace the common shielding material like concrete (ordinary and hematite-serpenite), commercial glass (RS 253), and the newly developed Ag2O doped boro-tellurite glass. The newly prepared glass has higher MAC, Zeff values and lowered HVL and MFP values. These properties make our prepared glass system superior in terms of shielding from γ-rays.

Сравнительная оценка распределения Cs-137 в почвенном покрове на территории Таджикистана

The article presents the results of a comparative assessment of the distribution of the technogenic radionuclide Cs-137 in the soil cover on the territory of the Republic of Tajikistan. It is noted that the accumulation of the 137Cs isotope in the territory depends on the terrain and soil type. At the foot of the mountains and in clay soils, a relatively high content of the Cs-137 isotope is observed compared to plains and sandy soils. The migration of radionuclide Cs-137 deep into the vertical is observed in the soils of sandy rock. It is shown that the values of the average specific activity of the Cs-137 isotope in the soil cover of Southern Tajikistan are 2.5 times lower than the average specific activities of the soils of Northern and Central Tajikistan. The highest values of specific soil activity of 17.0 Bq/kg were noted in the southeastern regions of Tajikistan. This circumstance is primarily due to the fact that precipitation and dust storms coming from the countries of South and Southeast Asia lead to the settling of particles, primarily on the slopes of the mountains. Thus, based on the analysis of the literature review in the direction under study and the results obtained, the authors revealed that the spatial distribution of Cs-137 radionuclide in the soil cover in the Republic of Tajikistan depends on the direction of the wind rose and the terrain. Analysis of the samples obtained allows us to conclude that the content of Cs-137 radionuclide is due to its long-range air transport.

Dynamics of 137Cs and 90Sr content in the soil cover of agricultural lands in Zhytomyr region

The article examines the results of monitoring radionuclide contamination the soils of Zhytomyr region with 137Cs and 90Sr. We summarized the results of agrochemical certification of agricultural land for the period of research in 2006–2020 years (IX–XI rounds). For field and laboratory research, methods of agrochemical certification of agricultural lands and gamma-surveying of the territory and determination of the specific activity of 137Cs and 90Sr in soil samples were used. It was established that during the 36 years that have passed since the accident, the radiation state of the territory of Zhytomyr region has currently stabilized and is formed mainly under the influence of long-lived radionuclides cesium-137 and strontium-90. During the time that passed after the accident, only due to natural radioactive decay, the activity of the isotopes 137Cs and 90Sr decreased approximately by half. This was facilitated by natural processes and the implementation of measures to prevent the removal of radionuclides beyond the exclusion zone. Turf-podzolic soils, which are most common in the Polissia zone, are characterized by high sorption capacity and weak migration along the 137Cs profile. It was established that the number of agricultural lands contaminated with 137Cs and 90Sr with a density <5.0 Ki/km2 and <0.15 Ki/km2 is 99.9% and 99.5%, respectively, the density of land soil contamination in the section of the surveyed areas with 137Cs pollution varied from 0.07 to 3.41 Ki/km2, and 90Sr from 0.013 to 0.164 Ki/km2, therefore, according to current legislation, the soils are considered conditionally clean. A direct correlation between the indicators of the reaction of the soil solution with 137Cs contamination (r=0.94) and a significant correlation with 90Sr contamination (r=0.69) was revealed. A moderate correlation (r=0.40) was found between the indicators of the density of contamination of agricultural land with radionuclides 137Cs and 90Sr. It is emphasized that the use of the land fund of Zhytomyr region requires constant monitoring of soil fertility and contamination with radionuclides. The implementation of the task is possible under the condition of permanent soil and agrochemical monitoring, which is conducted by carrying out agrochemical certification of agricultural lands.

Regularities of 137Cs distribution in the soil and vegetation cover of elementary landscape-geochemistry system within the forest test plot in the Chernobyl NPP exclusion zone.

The main goal of the investigation was to reveal the lateral and vertical regularities of element distribution in the elementary landscape-geochemical system (ELGS) type: summit-slope-closing depression. We used an isotope 137Cs as a tracer of migration of chemical elements in soil and vegetation cover. The study was performed in a test site characterizing undisturbed forest landscapes in the Russian zone of the Chernobyl accident. Investigated ELGS was 16-m long with a relative height difference of 1.5m. Field measurements of 137Cs activity was performed with a 1-meter step by the modified portable gamma-spectrometer Violinist-III (USA). Cs-137 content in moss and soil cores sampled with the same lateral step was determined in the laboratory using Canberra (USA, HPGe detector). The upper soil layer 8-cm thick contained from 70 to 96% of 137Cs, and 89-99% of the total inventory was fixed in the top 20-cm layer. Cs-137 activity in both the soil and moss cover demonstrated a cyclic type of variability, which was described and modeled using Fourier analysis. Correlation between the actual and modeled activity values (r0.01 = 0.868) showed that three main harmonics are sufficient for representative modeling of the observed cycles. We infer that the revealed patterns are characteristic for most of the chemical elements and may be useful for practical purposes.

Cesium-137 and 137Cs/133Cs atom ratios in marine zooplankton off the east coast of Japan during 2012–2020 following the Fukushima Dai-ichi nuclear power plant accident

We measured the concentrations of cesium isotopes (133Cs, 134Cs, and 137Cs) in zooplankton samples collected in waters off the east coast of Japan from May 2015 to June 2020. By combining these data with those obtained previously from May 2012 to February 2015, we evaluated the long-term impacts of the Fukushima Dai-ichi Nuclear Power Plant accident on marine zooplankton. Relatively high 137Cs concentrations in zooplankton, exceeding 10 Bq/kg-dry weight, were sporadically observed until June 2016, regardless of year or station. After May–June 2017, 137Cs concentrations decreased to below 1 Bq/kg-dry at most stations, and by May 2020, concentrations were below 0.5 Bq/kg-dry except those off Fukushima Prefecture. Since the accident, the 137Cs/133Cs atom ratios of zooplankton samples were higher than those of ambient seawater until 2019, but in May–June 2020 the ratios matched those of seawater except off Fukushima Prefecture. Highly radioactive particles were not detected in zooplankton samples by autoradiography using imaging plates after May–June 2017, although they were before. Therefore, the persistence of elevated 137Cs/133Cs ratios in zooplankton relative to seawater for nine years after the accident was probably due to the incorporation of highly radioactive particles (cesium-bearing particles or clay-mineral aggregates with highly adsorbed radiocesium) onto/into zooplankton for several years after the accident. However, since at least May–June 2017, these elevated ratios have likely been caused by small highly radioactive particles (or larger particles disaggregated into small pieces) entering the ocean from land via rivers or directly discharged from the Fukushima Nuclear Power Plant. Microplastics enriched with radiocesium with higher 137Cs/133Cs ratios than seawater may have also contributed 137Cs to the zooplankton.

Novel metallic Bi-Pb–Cd-Ag alloys for shielding against neutrons and gamma rays

Obtaining high-performance shielding alloys against mixed neutrons and γ-rays is vital in the field of nuclear radiation. In this work, shielding Bi-Pb–Cd-Ag alloys with superior thermal neutron shielding and high ability to attenuate γ-rays were developed. The microstructure, melting behavior, and mechanical properties of the prepared alloys were characterized. The γ-rays mass attenuation coefficients () were obtained using WinXCom program in the energy range of 0.015–15 MeV. The shielding parameters including atomic and electronic cross-sections (σ a and σ e), effective atomic number (Z eff ), effective electron density (N eff ) were calculated. The exposure buildup factor (EBF) using a geometric progression (GP) fitting method was estimated. The experimental measurements were carried out at 662 and 1173, 1332 keV of 137Cs and 60Co isotope sources, respectively using a scintillation gamma spectrometer NaI(Tl) detector. The calculated results of WinXCom are consistent and in agreement with the experimental values of The macroscopic effective removal cross-section () of the samples for fast neutrons were calculated. Also, the attenuation of thermal neutrons through the prepared alloys has been investigated. It was found that the alloy containing 30% Cd complies with the compromise between superior thermal neutron attenuation besides its superior ability to attenuate γ-rays with good mechanical strength and high ductility.

Sedimentation rates and sediment age of the high-altitude cold desert Ramsar Wetland, the Chandratal, inferred from radionuclide (210Pb and 137Cs) technique.

In the current scenario, the pristine Himalayan Wetlands are under endangerment due to higher sedimentation rate, including siltation, reduction of ecological value, pollution, and significant anthropogenic encroachment along with advanced civilization. The more increased sedimentation reduces the depth and existing expansion of the Wetland. This study articulates the record of sedimentation in the Chandratal present in Western Himalaya, Himachal Pradesh, India, at the altitude of 4300m. The sedimentation rate of the Chandratal was calculated based on a 1-m core sample considering isotopes of 137Cs and 210Pb dating techniques. The present study based on the Constant Rate of Supply (CRS) model of 210Pb reveals that the Wetland experienced an average sedimentation rate of 1.75 ± 0.04cm/year during the last 63years observed from 1953 to 2016. The 137Cs peak method-based calculated sedimentation rate of the Chandratal is 1.6 ± 0.02cm/year representing the years for about 62years from 1954 to 2016. The Wetland's functional survival prevalence was estimated to be 420 and 459years based on 210Pb and 137Cs dating techniques, respectively. The study communicates that the magnified human interference in the catchment area of the Chandratal is accountable for the faster sedimentation in recent years.

Novel Cesium Resistance Mechanism of Alkaliphilic Bacterium Isolated From Jumping Spider Ground Extract.

The radionuclide isotopes (134Cs and 137Cs) of Cesium (Cs), an alkali metal, are attracting attention as major causes of radioactive contamination. Although Cs+ is harmful to the growth of plants and bacteria, alkaliphilic bacterium Microbacterium sp. TS-1, isolated from a jumping spider, showed growth even in the presence of 1.2 M CsCl. The maximum concentration of Cs+ that microorganisms can withstand has been reported to be 700 mM till date, suggesting that the strain TS-1 is resistant to a high concentration of Cs ions. Multiple reports of cesium ion-resistant bacteria have been reported, but the detailed mechanism has not yet been elucidated. We obtained Cs ion-sensitive mutants and their revertant mutants from strain TS-1 and identified a Cs ion resistance-related gene, MTS1_00475, by performing SNP analysis of the whole-genome sequence data. When exposed to more than 200 mM Cs+ concentration, the intracellular Cs+ concentration was constantly lowered by MTS1_00475, which encodes the novel low-affinity Cs+/H+ antiporter. This study is the first to clarify the mechanism of cesium resistance in unexplained cesium-resistant microorganisms. By clarifying the new cesium resistance mechanism, it can be expected to be used as a bioremediation tool for treating radioactive Cs+ contaminated water.

In/CdTe/Au p–n junction-diode X/[formula omitted]-ray detectors formed by frontside laser irradiation doping

The fabricated In/p-CdTe/Au diode structures with Schottky (In/p-CdTe) and quasi-ohmic (Au/p-CdTe) contacts were transformed into p–n junction diodes by applying the developed frontside laser irradiation doping technique. The Schottky diodes with In and Au electrodes (both with thickness of 400 nm), deposited on the chemically pre-treated B- and A-face of the detector-grade CdTe(111) single crystals, respectively, were subjected to multiple (from tens to thousands times) irradiation from the In film side with series of nanosecond pulses of a KrF excimer laser. As a result of such irradiation, a thin heavily doped n-type CdTe:In layer was formed, a shallow abrupt p–n junction was created and thus the In/CdTe/Au Schottky diode was transformed into the In/CdTe/Au p–n junction diode. The temperature distributions in the In/CdTe/Au structure under laser irradiation were calculated and the I–V characteristics of the diodes were measured for different energy densities E and number N of laser pulses, respectively. The processes of frontside laser irradiation doping and carrier charge transport mechanisms in the created In/CdTe/Au p–n junction diodes were discussed. The samples with higher performance were obtained when only a part of the In electrode thickness was melted during a single laser action (E∼110 mJ/cm 2) and repeated (N∼300–500) irradiation was employed. The fabricated In/CdTe/Au p–n junction-diode structures with relative low reverse dark currents (∼20–50 nA/cm2) were quite sensitive to X/γ-rays and demonstrated sufficient ability to detect the emission of 241Am, 57Co, and 137Cs isotopes. It has been shown that applying the frontside laser irradiation doping technique to In/CdTe/Au structures, it is possible to transform Schottky diodes with low characteristics into highly rectifying In/CdTe/Au p–n junction diodes which are X/γ-ray detectors with moderate or even high detection parameters.

Separation of anthropogenic radionuclides from aqueous environment using raw and modified biosorbents

In this study, two types of biosorbents were used to remove 137Cs and plutonium isotopes from aqueous solutions - moss (Ptilium crista - castrensis) and oak sawdust (Quercus robur), both in the form of natural and modified state. Sorbent modification significantly increases the sorbent surface area (for moss sorbents - from 4.0 to 47.2 m2/g, and for sawdust sorbents - from 1.1 to 26.3 m2/g), pore volume (from 10−3 to 10−2), concentration and amount of basic cations and anions, as well as active functional groups on the sorbent surface. The main functional groups on the surface of natural sorbents modified with iron hydroxide interacting with analytes are carboxyl and hydroxyl groups. For carbonized sawdust and its subsequent activation with concentrated HCl, in addition to carboxyl and hydroxyl groups, acetyl groups also become active. Carbonated sawdust treated with HCl showed the highest average removal efficiency and sorption capacity for radiocesium and plutonium isotopes in laboratory column experiments - for 137Cs ∼78.6% and ∼196.6 Bq/g and for 239+240Pu ∼83% and ∼41.5 Bq/g, respectively. The moss and moss modified with iron hydroxide also showed good properties of adsorbing plutonium isotopes in field (in-situ) experiments. The best results on the sorption of 137Cs in field experiments were shown by carbonated sawdust activated with HCl, and for isotopes of plutonium - the raw moss and moss modified with iron hydroxide. The results of the study showed that sorbents can be used not only for purification of water from plutonium isotopes but allow the operational sampling and more accurate measurement of radiocesium and plutonium isotopes in the fresh water reservoirs by the dynamic flow method.

Correction: Strzałek et al. Activity of 137Cs and 40K Isotopes in Pine (Pinus sylvestris L.) and Birch (Betula pendula Roth) Stands of Different Ages in a Selected Area of Eastern Poland. Forests 2021, 12, 1205

The authors wish to make the following corrections to their paper [...]

Quantitative determination of 137Cs and 90Sr in dissolver solutions without pre-separation by isotope dilution thermal ionization mass spectrometry

Schematic representation of the measurement of isotopes of Cs and Sr present in a dissolver solution based on preferential evaporation.

Benthic macroinvertebrates as reference indicators for monitoring of anthropogenic isotope 137Cs contamination in the marine environment

Due to the limited studies dealing with isotopes levels in benthic macroinvertebrates other than Mytilus sp. in period 2011–2018, macroinvertebrates and seawater samples from the southern Baltic Sea were collected. Activity of 137Cs was measured in most common benthic macroinvertebrates inhabiting southern Baltic Sea in the context of choosing the best bioindicators. Taking into account the narrow range of CR coefficients, statistically significant correlation between 137Cs activities in seawater and species, a high frequency of occurrence and thus high biomass and the common occurrence, only Limecola balthica could potentially serve as indicators for shallow and deep-sea areas accordingly. Widely spread Mytillus trossulus was characterised by large size variability in samples and shows no significant correlation between activities in species and seawater and appears not so common as L. balthica.

Radioisotope identification using sparse representation with dictionary learning approach for an environmental radiation monitoring system

A radioactive isotope identification algorithm is a prerequisite for a low-resolution scintillation detector applied to an unmanned radiation monitoring system. In this paper, a sparse representation with dictionary learning approach is proposed and applied to plastic gamma-ray spectra. Label-consistent K-SVD was used to learn a discriminative dictionary for the spectra corresponding to a mixture of four isotopes (133Ba, 22Na, 137Cs, and 60Co). A Monte Carlo simulation was employed to produce the simulated data as learning samples. Experimental measurement was conducted to obtain practical spectra. After determining the hyper parameters, two dictionaries tailored to the learning samples were tested by varying with the source position and the measurement time. They achieved average accuracies of 97.6% and 98.0% for all testing spectra. The average accuracy of each dictionary was above 96% for spectra measured over 2 s. They also showed acceptable performance when the spectra were artificially shifted. Thus, the proposed method could be useful for identifying radioisotopes in gamma-ray spectra from a plastic scintillation detector even when a dictionary is adapted to only simulated data. Furthermore, owing to the outstanding properties of sparse representation, the proposed approach can easily be built into an in-situ monitoring system.

Прогнозування надходження радіонуклідів 137Cs і 90Sr у сільськогосподарські культури

Maps of the 137Cs contamination of abandoned agricultural land in Narodychi district (Zhytomyr region) were built using data of the radiological survey. Statistical characteristics of the soil contamination with 137Cs, 90Sr, and plutonium isotopes (median, geometric standard deviation, upper limit for Р = 0.9) were estimated. Contamination of the local crops with 137Cs and 90Sr as well as the risk of exceeding permissible levels were estimated. Recommendations for the return of these lands for commercial use are provided.

Activity of 137Cs and 40K Isotopes in Pine (Pinus sylvestris L.) and Birch (Betula pendula Roth) Stands of Different Ages in a Selected Area of Eastern Poland

Research Highlights: a forest is an ecosystem that allows for the assessment of radioactive contamination of the environment over several decades. (1) Background and Objectives: measurements of the activity of the 137Cs isotope in various elements of a forest ecosystem are one of the most important parameters in the assessment of radioisotope contamination. The translocation of 137Cs in the environment is determined by the activity of the natural 40K isotope in soil. The activities of 137Cs and 40K isotopes were assessed in two stands of Betula pendula and Pinus sylvestris, differing in age (30, 50, and 80 years old); (2) Materials and Methods: the research was conducted in one of the forest districts of eastern Poland. Wood, litter, and soil were collected for the tests from the sampling sites. The activity of 137Cs and 40K was determined using the γ-spectrometric method. Based on the activity of these isotopes in wood and soil, the values of translocation factors (TF) were determined; (3) Results: the highest activity of 137Cs was recorded in the wood of the oldest stands, the growth period of which coincided with the time period of intensive testing with nuclear weapons. With the growing age of the stand, the value of TF 137Cs increased, while the value of TF 40K was not dependent on the age of the stands. Birch wood accumulated more 137Cs and 40K isotopes than pine wood. (4) Conclusions: the results show a much greater radioactive contamination of the environment in eastern Poland during the testing with nuclear weapons than after the Chernobyl nuclear reactor explosion. The greater accumulation of radiocesium in birch wood than in pine wood predisposes this species to be more useful when assessing the radioactive contamination of the environment from the past.