Distribution Of Tritium Research Articles

Intensive agriculture, a pesticide pathway to >100 m deep groundwater below dryland agriculture, Cordoba Pampas, Argentina

Groundwater pesticide pollution in shallow groundwater is a well-established global phenomenon. However, deep aquifers are widely thought to be naturally protected from such modern contaminants, by confining geological barriers and upwards hydraulic gradients. Here we document pervasive pesticide pollution in >100 m deep artesian wells in a sedimentary aquifer below dryland agriculture. The vertical distribution of key groundwater markers, including numbers and concentrations of pesticides, stable (δ18O & δ2H) and radioactive (3H &14C) isotopes and ion concentrations were used to develop a conceptual model of pollutant transport to deep groundwater. Tritium, stable isotope and pesticide distributions in unconfined groundwater indicate that water table rise to <1 m below the surface (due to anthropogenic landscape modification and periodic flooding), has created a rapid pollutant ‘doorway’ to groundwater. Despite a lack of deep borehole pumping for irrigation, these rising water tables have permanently inverted previously upward hydraulic gradients towards the underlying semi-confined aquifer in some areas. Physical heterogeneities and/or leaky domestic boreholes then act as preferential transport avenues for surface pollutants to both unconfined and semi-confined groundwater. These pathways allow small aliquots of highly contaminated surface water and modern unconfined groundwater to mix with the pre-existing pre-modern deep groundwater, resulting in mixed isotopic signatures in deep wells (e.g., radiocarbon <5 pMC but detectable tritium) and detections of multiple synthetic pesticides in the deep aquifer, including AMPA at concentrations up to 4.93 µg/L and Metolachlor up to 0.015 µg/L. Our results demonstrate how semi-confined deep groundwaters may be contaminated by current agricultural techniques even where deep groundwater exploitation is limited. We urge measures to eliminate these pollutant pathways.

Tritium distribution in the 'water-soil-air' system in the Semipalatinsk Test Site.

This article presents research findings on 3H in abiotic environmental compartments, specifically, the 'water-soil-air' system. All of the research areas are located within the Semipalatinsk Test Site (STS): the perimeter of the 'Degelen' site, the riverside zone of the Shagan river and the 'background' area-the southeastern part of the STS (SEP). As research progressed, numerical values of 3H and its species were revealed in various environmental compartments. The presence of 3H was registered not only in underground nuclear test locations but also in the 'background' area-SEP. Maximum 3H tritium concentrations in the water were detected at the 'Degelen' site (up to 57000±5000 Bq/kg) and the Shagan riv (up to 61500±6000 Bq/kg), in the air of the 'Degelen' site (up to 56±11 Bq/m3), in the soil of the 'Degelen' site (up to 5170±500 Bq/kg) and the Shagan riv (4100±400 Bq/kg) in the free water, at SEP (up to 1710±170 Bq/kg) in the organic constituent. Based upon all of the findings, 3H was found to be readily distributed in abiotic environmental compartments depending on certain conditions. Research suggests that water plays a key role in 3H migration processes in the natural system of interest. The second most but equally important constituent is soil and microorganisms of plant and animal origin living there. These assumptions are indirectly proven by research findings that show the HTO and HT air concentration dynamics depending on the sampling location.

Tritium uptake in crops in the area with a high level of atmospheric tritium oxide in the territory of the former Semipalatinsk test site.

During the period from 2019 to 2021, a series of experiments were carried out to study the uptake of tritium by crops in an area heavily contaminated with atmospheric tritium oxide (HTO), at the former Semipalatinsk test site in Kazakhstan. A quantitative assessment is given of the tritium uptake by typical crops (lettuce, tomatoes, peppers and beans) cultivated all over Kazakhstan in the case of a short-term tritium oxide vapor exposure. The plant samples were collected during and after exposure and analyzed for the tritium concentration in two chemical forms: tissue-free water tritium (TFWT) and organically bound tritium (OBT). During the entire series of experiments, the tritium concentration in free water from leaves and ambient air was of the same order of magnitude. The tissue water tritium concentrations of stems and edible parts was 1 to 2 orders of magnitude lower than in the surrounding air. The average value of the TFWT/HTOatm ratio in the leaves and the edible part was (0.73±0.2) and (0.04±0.002), respectively. The organically-bound tritium concentration is 1-2 orders of magnitude lower than the tissue water tritium and ambient air concentrations. Under aerial tritium oxide uptake, the distribution of tritium in non-leafy crops was as follows: leaf-stem-fruit (in decreasing order). After exposure, a non-significant amount of tritium is firmly retained in plants for a long time. The tissue water tritium concentrations correlate closely with atmospheric tritium oxid (r = 0.76), correlate weakly with temperature (r = 0.43) and relative humidity (r = -0.43), and correlate moderately with solar radiation intensity (r = 0.56). There was no reliable correlation between the concentration of tritium in organic matter and in ambient air. The concentration of tritium in the free water of leaves is closely correlated with the concentration in the free water of the stems (r = 0.95) and fruits (r = 0.78). The organically-bound tritium concentration in leaves is closely correlated with the organically-bound tritium concentration in stems (r = 0.99) and fruits (r = 98). The results of the study should be considered when evaluating the impact of tritium oxide emissions on the population living near nuclear power.

A simulation study of tritium distribution in a 10WM(e) thorium-based molten salt reactor

The TMSR, with its thorium fuel cycle and molten salt technology, is an increasingly popular alternative to traditional nuclear reactors. In this study, an enhanced computational model was used to assess the distribution of tritium in SINAP's proposed 10 MW(e) TMSR system. The findings reveal that, in the absence of tritium removal measures, approximately one-third of the produced tritium could contaminate the environment. Moreover, the saturation of graphite adsorption can result in even greater tritium permeation over time. However, by implementing a method akin to the MSRE spray gas removal, approximately two-thirds of the tritium can be eliminated, reducing permeation to around 10 % and facilitating control. Furthermore, reducing the tritium yield from the reactor can further diminish the overall tritium amount and the proportion of permeation. For instance, substituting FNaBe salt for FLiBe salt as the fuel carrier yields lower tritium, thereby rendering control unnecessary or significantly reduced.

Lysozyme binding with amikacin and levofloxacin studied by tritium probe, fluorescence spectroscopy and molecular docking

Lysozyme complexes with amikacin and levofloxacin were studied by spectroscopy approaches as well as using a tritium probe. Tritium was used as a labeling agent to trace labeled compound concentration in a system of two immiscible liquids and in the atomic form to determine the possible position of the binding site. Co-adsorption of protein and drug at the liquid-liquid interface was analyzed by scintillation phase method that allowed us to directly determine the amount of protein and drug in the mixed adsorption layer. Also, tensiometric measuring of the interfacial tension was used for calculation of binding parameters accordingly to Fainerman model. The treatment of complexes with atomic tritium followed by trypsinolysis and analysis of tritium distribution in the lysozyme peptides reveals the binding sites, binding energies in which were analyzed using molecular docking. Formation of complexes with amikacin and levofloxacin preserves secondar structure of protein. However, the formation of complex with amikacin leads to the almost total loss of the enzymatic activity of lysozyme and the redshift of the maximum on the lysozyme fluorescence band. A slight decrease in the distribution coefficient of lysozyme in the presence of amikacin assumes that the complex has higher hydrophilicity in comparison to lysozyme without additives. The most favorable for binding were the positions of the active centers that included amino acids Asp52 and Glu35, as well as in the vicinity of peptide His15-Arg21, with the participation of amino acids Tyr20, Arg14. In the case of levofloxacin, the formation of lysozyme-ligand complex in aqueous solution is possible without changing the microenvironment of the active center of the protein. Binding of levofloxacin to the active center of the enzyme was the most favorable, but Asp52 and Glu35 that are responsible for the enzymatic activity of lysozyme, were not affected.

Overview of tritium retention in divertor tiles and dust particles from the JET tokamak with the ITER-like wall

Divertor tiles after Joint European Torus-ITER like wall (JET-ILW) campaigns and dust collected after JET-C and JET-ILW operation were examined by a set of complementary techniques (full combustion and radiography) to determine the total, specific and areal tritium activities, poloidal tritium distribution in the divertor and the presence of that isotope in individual dust particles. In the divertor tiles, the majority of tritium is detected in the surface region and, the areal activities in the ILW divertor are in the 0.5–12 kBq cm−2 range. The activity in the ILW dust is associated mainly with the presence of carbon particles being a legacy from the JET-C operation. The total tritium activities show significant differences between the JET operation with ILW and the earlier phase with the carbon wall (JET-C) indicating that tritium retention has been significantly decreased in the operation with ILW.

Tritiated stainless steel (nano)particle release following a nuclear dismantling incident scenario: Significant exposure of freshwater ecosystem benthic zone

Nuclear facilities continue to be developed to help meet global energy demands while reducing fossil fuel use. However, an incident during the dismantling of these facilities could accidentally release tritiated particles (e.g. stainless steel) into the environment. Herein, we investigated the environmental dosimetry, fate, and impact of tritiated stainless steel (nano)particles (1 mg.L−1 particles and 1 MBq.L−1 tritium) using indoor freshwater aquatic mesocosms to mimic a pond ecosystem. The tritium (bio)distribution and particle fate and (bio)transformation were monitored in the different environmental compartments over 4 weeks using beta counting and chemical analysis. Impacts on picoplanktonic and picobenthic communities, and the benthic freshwater snail, Anisus vortex, were assessed as indicators of environmental health. Following contamination, some tritium (∼16%) desorbed into the water column while the particles rapidly settled onto the sediment. After 4 weeks, the particles and the majority of the tritium (>80%) had accumulated in the sediment, indicating a high exposure of the benthic ecological niche. Indeed, the benthic grazers presented significant behavioral changes despite low steel uptake (<0.01%). These results provide knowledge on the potential environmental impacts of incidental tritiated (nano)particles, which will allow for improved hazard and risk management.

Influence of tritium distribution in aluminum and iron for shape of the beta-ray induced X-ray spectrum

Beta-ray induced X-ray spectrometry (BIXS) is commonly used for qualitative measurement of tritium in solids. We considered that BIXS could also be used quantitatively to determine the depth of tritium in solids. To determine the change in the shape of the BIX spectrum with tritium depth, spectra in aluminum and iron were calculated using the Monte Carlo simulation code (Galet-BIXS). The spectral shape was determined by the relative fractions of the characteristic X-ray components and bremsstrahlung. It was changed with the tritium depth, even when the number of tritium decay events was held constant in the simulations. Specifically, the spectral shape gave information about the tritium depth. However, the accuracy of the estimated tritium depth depended not only on the elements that interact with the beta particles but also on the tritium depth. In some cases, the tritium depth could not be evaluated from the BIX spectra. For example, the spectral shape for aluminum in helium was kept up to 10 µm deep of the tritium depth. When the atmosphere was replaced from helium to argon, the spectral shape was changed with the tritium depth up to 10 µm. Nevertheless, our method allows quantitative analysis of tritium in solids based on the BIX spectrum in most cases. We believe that the Monte Carlo simulation of the BIX spectrum is crucial to the further development to determine the tritium depth in solids.

Tritium and trees: A bomb peak perspective on soil water dynamics in semi-arid apple orchards

Understanding the relationship between agroforest age and soil water dynamics is crucial for effective land and water resources management. However, the complexities of these dynamics, such as soil water recharge and depletion, hamper in-depth understanding, particularly in water-scarce regions. In this study, we examined soil water recharge and depletion in relation to the stand age of apple trees, a widely planted and representative deep-rooted agroforest, over four years in a semi-arid region on China’s Loess Plateau (CLP). We collected soil cores to >20 m depth from four apple orchards (referred to as ‘agroforests’) with variable stand ages (established in 2008, 2005, 1998, and 1994). For comparison, we selected adjacent cropland as land use prior to agroforestry practices (‘control’). We measured soil water content and tritium distributions to model soil water dynamics and estimate water ages across different soil profiles. Our results show that recharge amounts (and depths) in shallow soils were 298.4 mm (7 m), 303.4 mm (6.6 m), 300.6 mm (5.4 m), and 483.1 mm (7.6 m), whereas deep soils had net depletions of 111.1 mm, 391.9 mm, 192.8 mm, and 108.9 mm for AP2008, AP2005, AP1998, and AP1994, respectively. The tritium peak depths, which indicate the 1963 bomb peak depth, significantly differed between agroforested and non-agroforested plots. In particular, agroforestation reduced the seepage velocity of soil water over 20 years. Furthermore, our tritium tracer water age model suggests that the age of transpired deep soil water exceeded 200 years in the oldest orchard. These findings highlight a complex interaction between newly infiltrated water and existing water, possibly due to variations in soil pore size distributions. The results of this study offer valuable insights into the ecohydrological impacts of agroforestation on the CLP and in similar climatic regions.

Tritium-titanium target degradation due to deuterium irradiation for DT neutron production

In the present article, we have investigated tritium removal from tritium-titanium targets during fusion neutron production and the impact of tritium degradation on neutron production. The removal of tritium from the target is predicted for deuterium ion irradiation with the SDTrimSp code. We adopt the binary collision approximation method to simulate the recoils and projectile trajectories and concentration of constituents in the target. We have modelled four phenomena in our simulations; ion exchange, sputtering, outgassing of tritium, and thermal diffusion of hydrogen isotopes in the target caused by deuterium irradiation. Insignificant contributors such as burn-up of tritium in neutron production and loss of tritium due to radioactive decay are not included in our model. This tritium removal results in the nonuniform distribution of tritium in the target. A Python-based script is developed to investigate the effects of tritium removal on neutron production with these pristine and irradiated targets. This script uses the layered composition of the constituents’ atoms, DT reaction cross-section, and stopping power of deuterium ions in the target. The script is validated with the NeuSdesc code for the pristine target. Using the layered composition of tritium atoms in the target obtained from the SDTrimSp simulations, the script predicts the degradation in neutron production for different irradiation scenarios.

Distribution of hydrogen isotope in the soil around the Qinshan Nuclear Power Plant

When a different types of reactor are operating at the same area and the same period of time, released radionuclides are hard to follow in the environment. In general, isotopic techniques can be used for source localization. To obtain the distribution of hydrogen isotope in soil, eight sampling points were selected along the local dominant wind direction with different distances away from Qinshan Nuclear Power Plant, and soil samples at different depths (0–2, 2–5, 5–10, 10–20, 20–30 cm) were collected in December 2019 and December 2020, respectively. The concentrations of hydrogen isotopes were measured in the soil samples at different depth. The spatial distribution of tritium and deuterium in the surface soil was related to soil properties and the distance from the nuclear power plant. It was found that tritium and deuterium are generally enriched in the upper layer. Determination of the deuterium concentration in the environment may be a new way to trace the released tritium from the reactors.

Tritium distributions in castellated structures of Be limiter tiles from JET-ITER-like wall experiments

Tritium retention in the castellated structure of beryllium limiters used in JET with the ITER-like wall (ILW) during the first (ILW1), third (ILW3) and all three (ILW1-3) campaigns were examined and evaluated. Tritium was deposited on the surfaces inside the castellation grooves together with deuterium, beryllium, oxygen, carbon and small amounts of metallic impurities such as nickel, copper and tungsten. The tritium content after the ILW1 campaign was greater than after the ILW3 campaign. This is attributed to the steadily decreasing amount of carbon impurities in JET from campaign to campaign. The majority of tritium was retained in shallow regions in the grooves, up to 2 mm from the entrance to the gap. It was comparable on all sides of the castellation, i.e. no difference has been detected between the toroidal and poloidal gaps. Secondly, the tritium retention in the gaps was similar on all specimens independent of their position in the tokamak, while the retention on the plasma-facing surfaces clearly depended on the tile position. The tritium deposition patterns in the castellation were also compared with the deuterium distribution determined in earlier studies.

Experimental Measurement and Multiphysics Simulation of Tritium Transport in Neutron-Irradiated Flibe Salt

Predicting the distribution and release of tritium remains a technical challenge for advanced nuclear reactors with molten Flibe (2LiF-BeF2) salt coolants. Tritium transport models, which are currently used to forecast release behavior, are limited by uncertainty in Flibe-related tritium transport properties and by a lack of relevant benchmark experiments to test input parameters and solution methods. A new test facility has been developed at the Massachusetts Institute of Technology Research Reactor (MITR) to irradiate a molten Flibe target in an ex-core neutron beam port to further investigate tritium transport mechanisms at prototypical reactor conditions. The experiment monitored the time-dependent release of tritium from the salt-free surface and the permeation rate of tritium through the stainless steel Flibe-containing test stand. Measured results were benchmarked with a multiphysics tritium transport simulation to resolve complex effects in the test. Trends in tritium release rates from the irradiation were in agreement with the multiphysics simulation of the test, which combined computational fluid dynamics, radiative heat transfer in participating media, and tritium transport in STAR-CCM+.

Incorporation of tritium by pepper and eggplant cultures with short-term exposure to tritium oxide

Incorporation of tritium by pepper and eggplant cultures with short-term exposure to tritium oxide

Application of the UNDBE Model in Combination with the RALG Method to Solve the Problem of Radioecology of Water Bodies

Introduction. The presence of radioactive pollution releases into the aquatic environment of NPPs operating in the normal mode, as well as during various emergency situations, requires the use of means for predicting the impact of such releases on the condition of surface water bodies. The existing developments either do not have a sufficient accuracy or are complicated and require a large amount of initial data and knowledge of the exact values of the parameters of the running processes. To ensure accuracy of forecasting pollutants spreading in surface water under conditions of limited measuring and computing facilities a box model (UNDBE) of pollution transfer was developed taking into account the time of pollution transportation through the water body and dilution of pollution in the incomplete box volume. The method of model adjustment according to measurement data has been developed, which additionally improves forecasting accuracy. This was made possible due to the short implementation time of the proposed model on a computer and the use of parametric identification using the RALG program. Purpose of work. Presentation of the general description of the developed model. Demonstration of modeling possibilities and parametrical identification by means of the offered model in combination with program means of search of extremum of not differentiable function. Results. In addition to a general description of the developed model, a modification for modeling tritium and strontium-90 propagation is given. The results of modeling and parametric identification are shown on examples of tritium distribution in the Loire river basin and strontium-90 in the Kiev reservoir. Conclusions. Application of UNDBE model in combination with RALG procedure provides fast calculation at preservation of modeling accuracy, possibility of fast and exact adjustment for the concrete water object that makes possible its application as an emergency response system. There is a possibility to apply the outlined approach for modeling the transport of other types of pollutants in surface water bodies. Keywords: pollution transport, surface water bodies, UNDBE box model, parametric identification, RALG experience.

Developments and Challenges in the Design of the ITER DRGA

The ITER Diagnostic Residual Gas Analyzer (DRGA) will measure the distribution of gas species, i.e., deuterium (D), tritium (T), and impurities, in the divertor exhaust stream and in the plasma periphery, with time resolution relevant to fusion plasma–wall particle dynamics. The uniqueness of the DRGA, over previous implementations of plasma dynamics residual gas analysis, is an integrated approach, combining mass and low-temperature plasma-activated optical spectroscopy, in a differentially pumped analysis station. A further unique feature of the ITER divertor-specific DRGA is an ~8-m separation of the analysis station from the sampled pumping duct, while still maintaining a ~1-s response time for hydrogen isotopic concentrations. ITER DRGA final design activities are strongly benefiting from testing of prototypical DRGA components and methods on present fusion devices, most currently on JET and W7-X. DRGA systems are implemented on both these devices and include sensors (and pumping methods) that are directly relevant to the ITER DRGA design. The recent JET-DTE2 campaign has provided the first experience on operating the combined ITER DRGA sensors with D-T plasmas. While enhancing system design for ITER, this experience on operating devices has also revealed additional engineering challenges, which further guide the continuing final design project. Meanwhile, the recent determination that the ITER DRGA, with slight optimization, will resolve the helium isotopes well enough to support an ITER pre-DT, He-3-based heating scheme, has greatly increased ITER Research Program interest in the DRGA and its implementation well ahead of the DT phase.

Insights into near-surface distribution characteristics of multi-form tritium with consideration of atmospheric buoyancy and gravitational deposition

Tritium contributes majority to the total airborne radioactive effluents from the nuclear facility because of its considerable production and difficulty in separation. Tritium inventory in the fusion reactor would reach an unprecedented magnitude which brings new safety concern. After being released into the atmosphere, inconsistent atmospheric dispersion behaviors might appear regarding different physicochemical forms such as gaseous state HT, gaseous-aerosol-droplet state HTO. In this study, atmospheric dispersion characteristics of multi-form tritium were investigated based on the computational fluid dynamics method validated by multi-fan type wind tunnel experiments. Species transport model and discrete phase model were used to describe atmospheric dispersion of gaseous and aerosol-droplet state tritium, respectively. Deposition velocity was predicted for gaseous and aerosol-droplet state tritium with different particle sizes. Conditions for describing the changes of particle diameter and its influencing on near-surface tritium distribution due to condensation were provided. The results show that buoyancy effect would strengthen along with the increasing gaseous tritium mass fraction in the airborne effluents. We also indicated that obvious gravitational deposition would appear once gaseous HTO was transformed into droplet state HTO with the particle diameter larger than 20 μm. Both the atmospheric buoyancy and deposition phenomenon would result in a quite different near-surface tritium distribution.

Reconstruction of the record of tritium in precipitation in the temperate zone of South America

AbstractTritium, a radioisotope of hydrogen, is an ideal tracer for groundwater and surface dating and tracking since it is part of the water molecule. The knowledge of the history of tritium in precipitation and recharge is the key link for the calculation of groundwater tritium age. However, records of tritium in precipitation are usually sparse and discontinuous, especially in regions like South America, and often need to be reconstructed. To solve this problem, different reconstruction methods of the tritium input function have been analysed and compared. Clustering of Global Network of Isotopes in Precipitation stations by regions and the correlation with the complete and continuous data recorded in Kaitoke (New Zealand) proved to be the most effective approach, having low relative errors and a much more extended coverage in time compared to other interpolation or reference curves methods. Thus, tritium time series for five different regions of the temperate zone of South America were obtained. These curves can be used as representative tritium input curves in future studies for these regions. The results obtained also allow a quick qualitative analysis of groundwater ages in these areas, based on their current or past tritium concentrations. In addition, they contributed to the understanding of the patterns and characteristics of tritium distribution in the atmosphere of the southern sector of South America.

Numerical Simulation of Tritium Diffusion Behavior in FeCrAl Cladding

In this article, a simulation code for tritium diffusion behavior analysis in FeCrAl cladding is developed based on the COMSOL platform. The simulated results are in good agreement with experimental and theoretical results. The effects of different concentrations of tritium and temperature distributions on the diffusion behavior of tritium in FeCrAl cladding were further investigated. Finally, the optimal effect of different coating schemes on the tritium resistance of the FeCrAl cladding was investigated. The results show that higher temperatures lead to higher cladding diffusion coefficients, which will further lead to higher fluxes of tritium into and out of the cladding, which is found to further result in a higher tritium flux into and out of the cladding, as well as shorter tritium diffusion times. It is found that higher temperature will lead to more tritium flux into and out of the cladding and shorter time for the tritium flux to reach a steady state on the right side of the cladding. At the same time, the higher tritium partial pressure on the fuel side of the cladding will lead to a longer time for the tritium flux to reach a steady state on the water side of the cladding. The longer time to reach the steady state on the water side of the cladding increases the tritium flux into the cladding.

Levels and behavior of environmental tritium in East Asia

For a more systematic understanding of the levels of environmental tritium and its behavior in East Asia, a database on environmental tritium was established based on the literature published in the past 30 years. Subsequently, the levels and behavior of the environmental tritium were further studied by statistical analyses. The results indicate that the distribution of environmental tritium is inhomogeneous and complex. In areas without nuclear facilities, the level of environmental tritium has decreased to its background level, even though a certain number of atmospheric nuclear tests were performed before 1980. In general, the level of atmospheric tritium was marginally higher than the levels in precipitation and surface water; the levels in shallow groundwater and seawater were considerably lower. Furthermore, the levels of tritium in the atmosphere, precipitation, and inland surface water were strongly correlated with latitude and distance from the coastline. In soil and living organisms, the level of tissue-free water tritium (TFWT) was comparable to the tritium levels in local rainfall, whereas the persistence of organically bound tritium (OBT) in the majority of organisms resulted in an OBT/TFWT ratio greater than one. Conversely, extremely high levels of environmental tritium were observed near certain nuclear power plants and the Fukushima accident sites. These results highlight the requirement to know the tritium baseline level and its behavior in the environment beforehand to better assess the impact of tritium discharge. Further investigations of environmental tritium in East Asia using more efficient and adequate monitoring methods are also required.