Behavior Of Radionuclides Research Articles

Bio-Dissolution Process as Environmental Technology for Uranium Leaching from El-Sella Ore Material by Aspergillus sulphureus

Research into radionuclide leaching behavior in the treatment of low-level radioactive waste solidification has been a widespread concern. Bioleaching of uranium was carried out using Aspergillus sulphureus isolated from El-Sella ore material. This area is located in the southern eastern desert of Egypt. The maximum bioleaching of U(VI) was found to be 83.1 % at these optimum conditions: 9 days incubation period, 0.5% pulp density, 30 °C incubation temperature at shaking speed 175 rpm. Glucose and NH4Cl were considered the best carbon and nitrogen sources for fungal growth through direct bioleaching process. A. sulphureus exhibits good potential in generating varieties of organic acids which effective for bioleaching of uranium. It produced 45.2 and 17 µg/ml from gallic and ellagic acids, respectively in the culture filtrate under the optimum conditions. This work represented the environmental technology for leaching of uranium where this is method is more save and low cost.

Identification of radionuclides’ altitudinal distribution In soil and mosses In highlands of Armenia

The present study was conducted in mountain regions of Armenia with the aim to assess the activity concentrations of natural K-40 and artificial Cs-137 in soil and mosses and reveal the distribution similarities and differences. Most widespread moss species and surface soils were sampled concurrently from eight mountain ridges and massifs by different altitudinal belts. Statistical analysis revealed significant differences and opposite characteristics for K-40 and Cs-137. In case of K-40 the activity concentrations decreased in mosses by altitude but with no significant correlation. The mean activity concentrations of K-40 in the soils of different altitudinal belts are close, nevertheless, the higher activity concentrations are common for soils derived from ingenious rocks. For Cs-137 in mosses, the correlation with altitude is statistically insignificant, but the altitudinal dependence is noticeable within separate ridges and massifs. A significant correlation was identified between Cs-137 in soil, altitude and precipitation rate. Studying natural K-40 and artificial Cs-137 radionuclides together yielded interesting contrasting results confirming the dissimilar behaviour of radionuclides with different origins in the environment.

Ten Years from the Fukushima Daiichi Nuclear Accident: Were the Predicted Effects Reported by Worldwide Experts Correct?

Since the Fukushima Daiichi Nuclear Power Station accident (hereinafter referred to as the "Fukushima Daiichi accident") occurred in March 2011, many experts around the world have conducted the assessments on radiation doses and health effects attributed to the Fukushima Daiichi accident. During the months soon after the accident while the state of the nuclear reactor was not accurately grasped, the radiation exposure of the residents was estimated based on the predicted environmental behavior of various radionuclides. However, there were significant differences in the estimated doses and effects presented by different researchers and research institutes. As investigations on the causes and progress of the Fukushima Daiichi accident have progressed in last 10 years, now we know better the situation and consequence of the accident. In this article, the contents of relevant papers and reports published during the three years (-2014) after the Fukushima Daiichi accident are briefly reviewed and then compared with the relatively new scientific information obtained in 2015 or later. Through these analyses, the author tries to look back on how correct or incorrect the initial estimates were.

Current Status of Studies of 90Sr Behavior in the Soil–Agricultural Plant System (Overview)

The necessity to study the mechanisms of 90Sr behavior in ecosystems is conditioned by the radioactive contamination of the environment due to global fallout as a result of nuclear weapon tests, as well as incidents and accidents at radiation-hazardous facilities. The basic regularities of radionuclide behavior in soils and in the soil–agricultural plants system are described. The role of various factors affecting radionuclide migration in ecosystems is assessed. The key characteristics required for the parameterization of migration mathematical models used for predicting the radionuclide uptake by plants are presented.

Colloid-facilitated transport of 238Pu, 233U and 137Cs through fractured chalk: Laboratory experiments, modelling, and implications for nuclear waste disposal

The influence of montmorillonite colloids on the mobility of 238Pu, 233U and 137Cs through a chalk fracture was investigated to assess the transport potential for radioactive waste. Radioisotopes of each element, along with the conservative tracer tritium, were injected in the presence and absence of montmorillonite colloids into a naturally fractured chalk core. In parallel, batch experiments were conducted to obtain experimental sorption coefficients (Kd, mL/g) for both montmorillonite colloids and the chalk fracture material. Breakthrough curves were modelled to determine diffusivity and sorption of each radionuclide to the chalk and the colloids under advective conditions. Uranium sorbed sparingly to chalk (log Kd = 0.7 ± 0.2) in batch sorption experiments. 233U(VI) breakthrough was controlled primarily by the matrix diffusion and sorption to chalk (15 and 25% recovery with and without colloids, respectively). Cesium, in contrast, sorbed strongly to both the montmorillonite colloids and chalk (batch log Kd = 3.2 ± 0.01 and 3.9 ± 0.01, respectively). The high affinity to chalk and low colloid concentrations overwhelmed any colloidal Cs transport, resulting in very low 137Cs breakthrough (1.1–5.5% mass recovery). Batch and fracture transport results, and the associated modelling revealed that Pu migrates both as Pu (IV) sorbed to montmorillonite colloids and as dissolved Pu(V) (7% recovery). Transport experiments revealed differences in Pu(IV) and Pu(V) transport behavior that could not be quantified in simple batch experiments but are critical to effectively predict transport behavior of redox-sensitive radionuclides. Finally, a brackish groundwater solution was injected after completion of the fracture flow experiments and resulted in remobilization and recovery of 2.2% of the total sorbed radionuclides which remained in the core from previous experiments. In general, our study demonstrates consistency in sorption behavior between batch and advective fracture transport. The results suggest that colloid-facilitated radionuclide transport will enhance radionuclide migration in fractured chalk for those radionuclides with exceedingly high affinity for colloids.

Penetration of fission product ions into complex solids and the effect of ionic wash methods.

During washing of radiologically impacted building surfaces, penetration of radionuclide ions into complex solids associated with these surfaces may occur. This study investigates the penetration of 137Cs, 85Sr, and 152Eu solutions into numerous common building materials and radionuclide behavior when these materials were exposed to a static bath or low-pressure flow of tap water, 0.1 M potassium chloride (KCl), and 0.5 M KCl. The decontamination efficacy and the depth profile for residual contamination were measured to determine the conditions under which applying a wash solution has benefit compared to physically removing the surface material. On asphalt, 70-80% of the radionuclides were found to be within 0.02 mm of the surface. Concrete is more porous than asphalt, and 80% of the radionuclides were within 0.2 mm of the surface for 137Cs and 152Eu and 50-80% for 85Sr. Water effectively removed all contaminants from hard nonporous surfaces. Finally, this paper illustrates that a wash penalty factor concept-defined as ratio of the depth at which 50% of the radioactivity is found in the washed sample divided by the depth at which 50% of radioactivity is found in the control-can serve as a way to quantify whether the wash method increases the depth at which contamination penetrates into the material and thus the material becomes more difficult to decontaminate.

Behaviour of heavy metals and natural radionuclides in the mixing of phosphogypsum leachates with seawater

Phosphogypsum (PG) is disposed worldwide in large stacks usually placed in coastal zones, as in the case of Huelva (SW of Spain), where around 100Mt of PG are stored on the salt marshes of the Tinto River estuary covering a surface of about 1000ha. This management generates the weathering of PG, and due to its high acidity (pH≈2) and pollutant load can provoke significant emissions into their surroundings. In this work were evaluated by laboratory experiments the effects of pH increase in the behaviour of heavy metals and natural radionuclides during the mixing of phosphogypsum leachates with seawater. The acidic phosphogypsum leachates showed concentrations of heavy metals from two to three orders of magnitude higher than natural continental waters, and natural radionuclides (U-isotopes and 210Po) from four to five orders of magnitude higher than unperturbed aquatic systems. Major elements and some heavy metals as Mn, Ni, Cd, As, Sb and Co showed a conservative behaviour during the neutralisation of the leachates with seawater, remaining in the liquid phase, while other ones as Al, Fe, Cr, Zn, Cu, Pb precipitated and/or were adsorbed onto the solid phase. The U-isotopes and 210Po showed a clear non-conservative behaviour probably due to coprecipitation/adsorption processes onto the formed precipitates, but while 210Po reached a total removal at pH≈7, U- isotopes after a total removal at pH≈5 returned into the liquid phase due to redissolution/desorption processes at near neutral pH. The formed precipitates, mainly composed by iron phosphates particles, showed heavy metal and natural radionuclide concentrations from one to three orders of magnitude higher than unperturbed soils. All these facts demonstrate the serious environmental impact produced by the PG stacks into their surroundings and the urgency of effective restoration measures.

Radionuclides from the Fukushima Daiichi Nuclear Power Plant in terrestrial systems

The 2011 Fukushima Daiichi Nuclear Power Plant (FDNPP) accident, Japan, released the largest quantity of radionuclides into the terrestrial environment since the 1986 accident at Chernobyl. This accident resulted in 2.7 PBq of radiocaesium (137Cs) contaminated forests, agricultural lands, grasslands and urban areas, which subsequently migrated through soil and waterways in the Fukushima Prefecture. In this Review, we synthesize knowledge regarding the deposition, distribution and transport of fallout radionuclides, especially 137Cs, in the terrestrial environment after the FDNPP accident, which were revealed by extensive and continuous environmental monitoring. Anthropogenic activities, high run-off and steep topography led to a rapid decline in the activity concentration of 137Cs in soils and rivers, especially in the first year after the accident. The decline in exposed radioactivity was notably faster than that seen after the Chernobyl Nuclear Power Plant accident, likely related to differences in geography and climate, and the intensive remediation activities in Fukushima. However, forests in Fukushima have retained a notable amount of 137Cs in the upper centimetres of soil and could persist as a source of 137Cs into rivers. For continued understanding of both natural and fallout radionuclide behaviour in the environment, there must be long-term accessibility of the data collected in response to the FDNPP accident. The 2011 nuclear accident in Fukushima, Japan, released large amounts of radionuclides, including 10 PBq of relatively long-lived radiocaesium, into the atmosphere. This Review details the distribution, migration and impact of fallout radionuclides in the terrestrial environment in the subsequent years.

Leaching behavior of radionuclides from samples prepared from spent fuel rod comparable to core debris in the 1F NPS

ABSTRACT To investigate the leaching behavior of radioactive nuclides in leaching samples comparable to core debris (partially molten ZrO2/UO2 between fuel rods) in the Fukushima Daiichi Nuclear Power Station (1 F NPS), the concentration of radionuclides in the leaching solution was measured. The leaching behaviors of actinides (U, Pu, and Np) and Cs from the samples were similar to those from spent fuel. As predicted from the current thermodynamic database, the leaching of U and Pu depends on the pH in the cooling water of the core debris. However, if Mo and Tc are surrounded by zircaloy in the core debris, their leaching amount may increase by one order of magnitude than those from spent fuel.

Применение концептуальной модели зональности хронического действия мощностей доз ионизирующих излучений на объекты биосферы Г. Г. Поликарпова в прикладной гидробиологии

В работе кратко рассмотрена эволюция подхода к оценке воздействия ионизирующей радиации на живые организмы. На примере черноморских гидробионтов показана возможность применения концептуальной радиохемоэкологической модели зональности действия хронического облучения ионизирующих излучений в природе Г. Г. Поликарпова для оценки уровня экологического воздействия ионизирующего излучения от техногенных радиоизотопов на водную биоту. Эта модель может служить в прикладной гидробиологии основой комплексного подхода к оценке экологического состояния водной биоты и его прогноза для широкого диапазона концентраций активности 239,240Pu в морской воде. Подчёркивается необходимость совместного применения биогеохимического и эквидозиметрического показателей поведения радиоизотопов в водоёме. В частности, для прогнозных дозиметрических оценок важно учитывать количественные характеристики концентрирующей способности черноморских гидробионтов и тип биогеохимического поведения радиоэлемента, отражающие особенности биогеохимической миграции плутония в морской экосистеме.

Chaos and regularity of radionuclides with maximum likelihood estimation method

In this study, we considered the fluctuation properties of some energy levels of even and odd mass radionuclides, which are used in complex phenomena. Different sequences are prepared by using all the available experimental data and analyzed by using the maximum likelihood estimation technique to get the chaoticity parameter of Abul-magd distribution. The dependence of chaoticity degrees of different radionuclides to their mass regions, their decay modes, and also their physical half-lives are studied. Our results show more chaotic behavior of odd-mass radionuclides in comparison with even–even mass and also the most Poisson-like behavior for even–even mass in the A > 150 mass region. The results offer the most regular behavior for long-lived, even mass radionuclides in comparison to other categories of half-lives. Also, we got an obvious difference between the chaoticity degrees for nuclei which undergo β + decay in comparison with radionuclides which show electron capture mode.

Water\u2013rock interactions in the Bruchsal geothermal system by U\u2013Th series radionuclides

Uranium and thorium decay series disequilibria in deep geothermal brines are a result of water–rock interaction processes. The migratory behavior of radionuclides provides valuable site-specific information and can therefore be an important tool for reservoir characterization and sustainable management of geothermal sites. In this study, we present data from long-term monitoring of naturally occurring 238U, 232Th and 235U series radionuclides analyzed in brine samples collected from the Permo-Triassic sedimentary reservoir rock at the Bruchsal geothermal site (SW Germany). The results show that radionuclides of the elements radium (226Ra, 228Ra, 224Ra, 223Ra), radon (222Rn), and lead (210Pb, 212Pb) are rather soluble in brine, while isotopes of uranium (238U, 234U, 235U), thorium (232Th, 228Th, 230Th), polonium (210Po), and actinium (227Ac, 228Ac) have low solubilities and are mostly immobile. Activities of radium isotopes in the geothermal brine exceed those of their thorium progenitors (average 226Ra = 29.9 Bq kg−1, about 103 times that of its 230Th parent). Modelling the observed disequilibria allows the following conclusion on water–rock interaction processes: (1) supply from alpha-recoil depends on isotope half-life because it is limited by the rate of diffusion through microfractures causing isotopic fractionation. (2) Radium retardation due to adsorption is low (226Ra/222Rn = 1.3) resulting in adsorption–desorption rate constants in the order of 10−10 s−1 for k1 and 10−9 for k2. (3) Scavenging of 226Ra from brine can best be explained by co-precipitation with barite resulting in an observed 226Ra anomaly in the solids of the reservoir section. The precipitation rate constant amounts to ca. 3.4 × 10−8 s−1 corresponding to a mean removal time of radium from brine by mineral precipitation to approximately 1 year.

Long term behaviour of radium rich deposits in a lake ecosystem

Behaviour of radionuclides released into environment is crucial for further evaluation of any kind of possible effects. Possibility of observation how does a radionuclide behave in natural environment is limited to very few post accidental areas. However, valuable observation can be collected at areas where enhanced concentration of natural radionuclides is presented caused by activity of non-nuclear industry. One example is area affected by release of radium rich brines from coal mines (Upper Silesia, south of Poland) that let one observe radium and its decay product behaviour in freshwater ecosystem from long-term perspective.Selected as long-term observatory site former mine water reservoir allowed identification of processes leading to accumulation of radium in bottom sediments and observation of its further behaviour from 17-years-time perspective. New data were collected during two-years monitoring campaign and compared with archive data on radioactivity in water and sediments collected in 1999. Radium-barium co-precipitation process was identified as main source of sediments heavy contamination, however, radium chemical form resulted from this process is insoluble and not easy migrate to other environmental compartments, what was proved by low 226Ra and 210Pb transfer to water measured under laboratory condition and to biota observed on site. As barium is not always present in mine radium rich brines a discussion is launched what would happen when such waters are released into environment based on simple laboratory experiment.In main conclusion is underlined that the current radium activity concentration in sediments is lower than expected only considering radioactive decay. Distribution of 226Ra, 228Ra and 210Pb in sediment profiles suggest that bio- or mechanical turbation (e.g. local flood) is responsible for significant 226Ra deficiency observed.

Kinetic Theory Analysis of Radionuclide Behavior in the Vacuum-Cesium System of a Thermionic Converter Reactor

The behavior of radionuclides (Kr and Xe) and process gases (CO) in the vacuum-cesium channel of a thermionic converter reactor is modeled by solving Boltzmann’s equation numerically. Modeling techniques and a software system were developed in the course of this work. Series of calculations were performed for the variation of the initial flux of radionuclides, the dependence of the radionuclide flux at the egress on the flux at the ingress was obtained, the dependence of the carbon monoxide pressure in the opening of the connecting channel on the size of the opening was obtained, and the overgrowth time of the opening due to the condensation of cesium carbonate was estimated.

Sorption and separation performance of certain natural radionuclides of environmental interest using silica/olive pomace nanocomposites

This study is concerned with the sorption behavior of natural radionuclides (226Ra, 210Po, 228Th—originated from TENORM waste associated with petroleum industry) onto silica/olive pomace nanocomposite. Initially, nanocomposites of extracted silica and olive pomace are prepared and characterized by physicochemical techniques. In the batch technique, 60% SiO2 40% olive pomace (AM3) nanocomposite showed a considerable group sorption for 226Ra and 210Po larger than 228Th in 1M HNO3 and HClO4 solutions. In case of sorption by the compacted disc, sorption of 226Ra was similar to batch method, sorption of 228Th increased slightly to ~ 17%, while sorption of 210Po was decreased to 77%. Thus, AM3 nanocomposite can be considered as an efficient nano-adsorbent for sorption and separation of Ra-isotopes and 210Po-radionuclides from 226Ra–210Po–228Th admixture associated with nuclear and non-nuclear industries.

Computer models of gas-dynamic processes of radionuclides behavior in thermal emission converter of nuclear power plant

The paper is devoted to the application of numerical solution of the Boltzmann equation method for modeling the behavior of radionuclides (Xe and Kr) in the inter-electrode gap and the vacuum-cesium channel of a thermionic reactor-converter, which is used in a space nuclear power generator. In this work, we developed modeling techniques and implemented them in a software package, that is using the algorithm of simultaneous calculations for the left side of the Boltzmann equation. We performed series of calculations for different initial flux of radionuclides and evaluated the dependence of the radionulcides output flux on the input flux for two areas of the reactor.

Influence of γ-irradiation and oxygen conditions on the diffusion of I-125 in crushed Beishan granite

The diffusion of iodine (labeled with 125I-) in compacted Beishan granite (BsG) was investigated using the in-diffusion capillary method at pH ~2.0 to ~11.0 under oxygen and irradiation conditions. With the advantages of simple and easy operation of the capillary diffusion devices, this work makes a preliminary investigation on the irradiation condition that cannot be performed by the traditional diffusion experiment. In this study, Da values of 125I as a tracer in the form of iodide were determined to investigate and assess the influence of irradiation and oxygen conditions, which must be considered in-situ environment of the geologic repository. The results indicate that capillary method is a simple and efficient method to study the diffusion behavior of radionuclides, which is a relatively feasible to quickly obtain the diffusion coefficient, especially for some special conditions, e.g., oxygen and irradiation conditions. The diffusion results showed that Da values of 125I- range from 1.4 × 10-10 to 1.5 × 10-9 m2∙s-1, which was much faster than other nuclides, such as 79Se (10-11 m2∙s-1). The batch adsorption experiments in this paper and related studies showed that the sorption could be neglected, i.e., 125I- is a weak adsorbent nuclide. Its diffusion and sorption process were hardly affected by pH、oxygen and irradiation conditions, which is very different from 79Se. Besides, ionic strength has a significant impact on the diffusion rate of 125I-, which is closely related to the double electric layer. Overall, this study indicates that natural BsG couldn't greatly attenuate the mobility of 125I- in the deep geologic repository and new retardation method or materials need to be explored.

Sorption of anthropogenic radionuclides onto river sediments and suspended solids: dependence on sediment composition

The purpose of the study is to explore the sorption behaviour of anthropogenic radionuclides in the Vltava River catchment in the Czech Republic, which could be influenced by an assumptive severe nuclear accident. Radionuclide sorption was described by distribution coefficients between water and sediment or suspended solids, respectively. Then, possible correlations between radionuclide sorption and sediment properties were investigated using simple and multiple regressions. The sorption of radionuclides was affected by sediment granularity and mineralogical composition, each radionuclide having its group of influencing sediment parameters.

Release behavior of radionuclides from MOX fuels irradiated in a fast reactor during heating tests

In order to obtain the release rate coefficients from fuels for fast reactors (FRs), heating tests and the subsequent analyses of the fission products (FPs) and actinides that are released were carried out using samples of uranium-plutonium mixed oxide (MOX) fuel pellets irradiated at the experimental fast reactor Joyo. Three heating tests targeting temperatures of 2773, 2973 and 3173 K were conducted using an FP release behavior test apparatus equipped with a high-frequency induction furnace and solid FP sampling systems consisting of a thermal gradient tube (TGT) and filters. Irradiated fuel pellets were placed into a tungsten crucible, then loaded into the induction furnace. The temperature was raised continuously at a heating rate of 10 K/s to the targeted temperature and maintained for 500 s in a flowing argon gas atmosphere. The FPs and actinides released from the MOX fuels and deposited in the TGT and filters were quantified by gamma-ray spectrometry and inductively coupled plasma mass spectrometry analysis. Based on the analysis, the release rates of radionuclides from MOX fuels for FRs were obtained and compared with literature data for light water reactor (LWR) fuels. The release rate coefficients of FPs obtained in this study were found to be similar to or lower than the literature values for LWR fuels. It was also found that the release rate coefficient data for actinides were within the range of variation of literature values for LWR fuels.

Short-term elemental release from Portland cement concrete in hypersaline leaching conditions

In the context of the long-term safety assessment of high-level nuclear waste (HLW) disposal, the initial release of metal ions from cementitious materials used as technical barriers is of great interest due to their possible interactions with HLW radionuclides (e.g. influencing the retention behaviour of radionuclides in engineered and natural barriers) due to water ingress. In the geochemical conditions in northern Germany, the porewater is of very high salinity, with salt contents of up to 2·5 M. In this work, the elemental composition of leaching water (with different types and amounts of salt) after 24 to 72 h contact with concrete was studied in order to simulate different water intrusion scenarios. It was found that in, addition to the main concrete elements (calcium, silicon, aluminium and iron), many trace elements were quantified in the concrete leachate. The influence of the concrete grain size in the leaching experiment showed that the use of particles <100 μm is necessary to obtain reproducible results. The influences of different solution salinities and the addition of calcium chloride and sodium sulfate on the leaching process were examined. For most elements, an increase in sodium chloride concentration enhanced the leaching process.