Radioactive Tritium Research Articles

Influence of plasma impurities on the fuel retention in tungsten

The retention of radioactive tritium in the reactor wall is a safety issue and should be kept to a minimum. We investigated the influence of helium, argon, neon and nitrogen as plasma impurities on the deuterium retention in tungsten in the linear plasma devices PSI-2 and PISCES-A. Following mixed plasmas were produced: pure D, D + He, D + Ar, D + Ne, D + N and D + He + Ar, with impurity fractions between 3% and 10%. Experiments were performed at tungsten sample temperatures of 500 and 770 K. The incident ion energy was 70 eV, above the tungsten sputtering threshold for argon and nitrogen, but below it for deuterium and helium. For neon, in addition, it was varied between 20 and 70 eV, below and above the tungsten sputtering threshold, respectively. The admixture of helium reduced the deuterium retention by a factor of 3–100, with a stronger reduction at a higher sample temperature. In the D + He + Ar case the retention was similar as for pure D. Argon sputtered the near-surface helium nanobubble layer and thus overrode the effect of helium. The effect of neon is sensitive to the incident ion energy. Addition of nitrogen increased the deuterium retention by a factor of ~10 and ~100 for 500 and 770 K, respectively. In general, the effect of impurities on the deuterium retention appears to be sensitive to the properties of the affected near-surface layer of tungsten. Admixed species, i.e. helium, can form a layer with open porosity, which serves as an additional release channel for deuterium thus decreasing the retention. However, if the process is dominated by sputtering, as for argon, such a layer cannot be formed. The nitrogen enriched layer, in contrast, serves as a desorption barrier for deuterium increasing the retention.

Climate change impact on residual contaminants under sustainable remediation

This study investigates the potential impact of climate change on residual contaminants in vadose zones and groundwater. We assume that the effect of climate changes can be represented by perturbations in the natural recharge through the aquifer system. We perform numerical modeling of unsaturated/saturated flow and transport and consider different performance metrics: contaminant concentrations at observation wells and contaminant export at the site's boundary. We evaluate the effect of increasing and decreasing recharge as well as the impact of potential failure of surface capping structures employed to immobilize vadose zone contaminants. Our approach is demonstrated in a real case study by simulating transport of non-reactive radioactive tritium at the U.S. Department of Energy's Savannah River Site. Results show that recharge changes significantly affect well concentrations: after an initial slight dilution we identify a significant concentration increase at different observation wells some years after the recharge increase and/or the cap failure, as a consequence of contaminants' mobilization. This effect is generally emphasized and occurs earlier as the recharge increases. Under decreased aquifers' recharge the concentration could slightly increase for some years, due to a decrease of dilution, depending on the magnitude of the negative recharge shift. We identify trigger levels of recharge above which the concentration/export breakthrough curves and the time of exceedance of the Maximum Contaminant Level for tritium are remarkably affected. Moreover, we observe that the contaminant export at the control plane, identified as the risk pathway to the downgradient population, may only be minimally affected by shifts in the natural recharge regime, except for some extreme cases. We conclude that more frequent sampling and in-situ monitoring near the source zone should be adopted to better explain concentrations' anomalies under changing climatic conditions. Moreover, the maintenance of the cap is critical not only to sequester residual contaminants in the vadose zone, but also to reduce the uncertainty associated with future precipitation changes. Finally, realistic flow and transport simulations achieved through proper calibration processes, rather than conservative modeling, should be adopted to identify non-trivial trade-offs which enable better allocation of resources towards reducing uncertainty in decision making.

Tracing natural groundwater recharge to the Thiaroye aquifer of Dakar, Senegal

Urban groundwater in Sub-Saharan Africa provides vital freshwater to rapidly growing cities. In the Thiaroye aquifer of Dakar (Senegal), groundwater within Quaternary unconsolidated sands provided nearly half of the city’s water supply into the 1980s. Rising nitrate concentrations traced to faecal contamination sharply curtailed groundwater withdrawals, which now contribute just 5% to Dakar’s water supply. To understand the attenuation capacity of this urban aquifer under a monsoonal semi-arid climate, stable-isotope ratios of O and H and radioactive tritium (3H), compiled over several studies, are used together with piezometric data to trace the origin of groundwater recharge and groundwater flowpaths. Shallow groundwaters derive predominantly from modern rainfall (tritium >2 TU in 85% of sampled wells). δ18O and δ2H values in groundwater vary by >4 and 20‰, respectively, reflecting substantial variability in evaporative enrichment prior to recharge. These signatures in groundwater regress to a value on the local meteoric water line that is depleted in heavy isotopes relative to the weighted-mean average composition of local rainfall, a bias that suggests recharge derives preferentially from isotopically depleted rainfall observed during the latter part of the monsoon (September). The distribution of tritium in groundwater is consistent with groundwater flowpaths to seasonal lakes and wetlands, defined by piezometric records. Piezometric data further confirm the diffuse nature and seasonality of rain-fed recharge. The conceptual understanding of groundwater recharge and flow provides a context to evaluate attenuation of anthropogenic recharge that is effectively diffuse and constant from the vast network of sanitation facilities that drain to this aquifer.

Research on water interconnections within the Sar Mountains aquatorium by radioactive hydrogen isotope tritium

The waters of two lakes and two streams that dominate in the Sar Mountains aquatorium were analyzed. The tritium profile of soil was also recorded. All samples were taken at approximately the same time, together with samples of precipitation. During the period of taking samples, the ambient temperature conditions were taken into account for ten days around the time of sampling. Monitoring of the seasonal maximum with taking into account the obtained tritium soil profile and the temperature on and around the day of sampling unambiguously showed that all tested water in the Sar Mountains aquatorium is of atmospheric origin and as such unsuitable for any major transformation for commercial purposes.

Моделирование параметров бетавольтаического элемента на основе тритида титана

AbstractThe simulation of β-voltaic power cells consisting of a combined β-source and a converter was performed. The TiT_2 compound containing the radioactive tritium isotope was selected as the source. As the converter, structures based on semiconductor materials, most commonly used in developing power cells, i.e., Si, SiC, GaAs, were considered. Using the Monte Carlo method, the main source parameters were calculated, in particular, the maximum achievable short-circuit current was estimated.

Simulation of the Parameters of a Titanium-Tritide-Based Beta-Voltaic Cell

The simulation of β-voltaic power cells consisting of a combined β-source and a converter was performed. The TiT2 compound containing the radioactive tritium isotope was selected as the source. As the converter, structures based on semiconductor materials, most commonly used in developing power cells, i.e., Si, SiC, GaAs, were considered. Using the Monte Carlo method, the main source parameters were calculated, in particular, the maximum achievable short-circuit current was estimated.

Time-dependent simulation of the flow reduction of D2 and T2 in the KATRIN experiment

The KArlsruhe TRItium Neutrino experiment (KATRIN) aims to measure the effective electron anti-neutrino mass with an unprecedented sensitivity of 0.2 eV/c2, using β-electrons from tritium decay. Superconducting magnets will guide the electrons through a vacuum beamline from the windowless gaseous tritium source through differential and cryogenic pumping sections to a high resolution spectrometer. At the same time tritium gas has to be prevented from entering the spectrometer. Therefore, the pumping sections have to reduce the tritium flow by at least 14 orders of magnitude. This paper describes various simulation methods in the molecular flow regime used to determine the expected gas flow reduction in the pumping sections for deuterium (commissioning runs) and for radioactive tritium. Simulations with MolFlow+ and with an analytical model are compared with each other, and with the stringent requirements of the KATRIN experiment.

Study on optimization of liquid scintillation counting during tritium measurements

This study was intended toward the evaluation of the correlation between the quenching coefficients and the counting efficiency for the physical quenching phenomenon and the effects of the properties of the standard sources for quenching on the tritium radioactivity concentration in the process of analyzing the tritium radioactivity concentration. Accordingly, a series of standard sources for quenching was prepared using three types of vials with different properties used for correction by the quenching phenomenon; the calculated values of the counting efficiency of a series of standard sources for quenching, relative errors in the counting values, uncertainty, and properties of the quenching correction curve were evaluated. On the basis of the results, nine samples (three glass-vial-type samples, three plastic-vial-type samples, and three Teflon-vial-type samples) were obtained and evaluated by applying Parameter Groups 1, 2, and 3, for which the efficiency was calibrated using the WinQ program in accordance with the properties of a series of standard sources for quenching. The results of this study are expected to serve as an aid in accurately understanding the standard sources for quenching, counting, and analyzing environmental samples that are subject to counting and analysis.

Hydrogen and deuterium isotope effects beyond the electromagnetic force

A mechanism is presented concerning electrolysis of deuteriated water with a palladium cathode that is infused with deuterium (palladium deuteride) resulting in the formation of small amounts of radioactive tritium, excess energy (more than allowed by EMF chemistry alone) and the concomitant liberation of 4He. These net electron catalyzed nuclear chemical reactions (2H + 2H + e− → 4He + e− + heat) and (2H + 1H + e− → 3H + e−) appear to be a result of respectively four and three isotope effects acting in combination with each other in a non-linear (chaotic) fashion to produce a metastable nuclear isomer of hydrogen-4 or hydrogen-3. The four isotope effects begin with the influx of electrons into the –PdDPdD Bravais lattice conduction band and consequent preferred rupture of individual weak Pd-D bonds (over those of PdH) in the cathode liberating D2. This is followed by the newly freed deuterium capturing an electron yielding a di-neutron (onon). The onon then reacts with a deuterium or hydrogen (from protic impurity in the lattice) via phonon enforced quantum tunneling resulting in 4mH or 3H respectively. The 4mH quickly undergoes nuclear internal conversion to form 4He. These reactions involve the weak force (Feynman Diagrams are shown), but they take place in simple electrochemical systems that are normally thought of in terms of the electromagnetic forces only. The combined influence of the four isotope effects explains thousands of, what were considered, anomalous observations by top electrochemical researchers. The newly described mechanistic effects involve a very important and almost forgotten intermediate (the di-neutron) and may even involve unique safety concerns.

Off-gas processing system operations for mercury target vessel replacement at J-PARC

An off-gas processing system was installed in the J-PARC spallation neutron source to reduce radioactivity of xenon-127 and tritium contained in a helium cover gas in a surge tank of a mercury circulation system to obey the regulation by law. In addition to this role it has been utilized to a purging process before the target vessel replacement and an air-flow control procedure to minimize uncontrollable radioactivity release during the replacement. An standard and urgent model plans of the off-gas processing system operation were established indicating that 31 days were required at least to replace the target vessel.

The caesium and strontium adsorption properties of bamboo charcoal-containing concrete blocks

The Fukushima Daiichi Nuclear Power Plant accident was caused by the Great East Japan Earthquake that occurred in March 2011 in Japan. Large amounts of radioactive materials (radioactive caesium, radioactive strontium, radioactive tritium and radioactive iodine.) were released from the power plant into ecosystem components such as air, soil, and water. One way to use bamboo is to produce bamboo charcoal, which is used to purify water and condition soil. Its minerals and adsorption properties are also used for soil conditioning, humidity regulation, water purification, and as electromagnetic shield material. It has also been discovered that bamboo charcoal has a high capacity to adsorb caesium and strontium. The objective of the research described herein was to develop materials that can efficiently recover radioactive substances that exist in water. It is because caesium and strontium are scattered a lot and bamboo is inexpensive, a ubiquitous and harmless material and excellent in adsorption performance. We fabricated concrete blocks mixed with bamboo charcoal and assessed their capacity to adsorb caesium and strontium. Bamboo charcoal and cement were mixed at a 1 : 1 weight ratio and water was added to the mixture. After drying for a day, the hardened mixture was formed into concrete blocks containing bamboo charcoal. Scanning electron microscopy was performed, and factors such as pH and thermal change of the samples were investigated. To study the adsorption capacity of the samples, 1.00 g of the samples was immersed in 100 mL of a 10.0 mg/L caesium solution and strontium solution. After an hour, the concentration of caesium dropped by 40.3% and strontium by 83.1%, indicating that concrete blocks containing bamboo charcoal had a high capacity to adsorb caesium and strontium. Furthermore, the results of thermal analysis showed that the bamboo charcoal-contained in the concrete blocks burned at approximately 400°C. The boiling point of caesium is 670°C and that of strontium is 1381 °C, which suggests that weight can be reduced by burning away the bamboo charcoal at 400°C without the caesium, etc. volatilising. In addition, because the concrete blocks can be formed in various shapes, it holds promise for application in rivers, lakes, sewers.

Theoretical investigation on the point defect formation energies in beryllium and comparison with experiments

Beryllium will be used as a plasma-facing material for ITER and will retain radioactive tritium fuel under normal operating conditions; this poses a safety issue. Vacancies play one the key roles in the trapping of tritium. This paper presents a first-principles investigation dedicated to point defect in hcp beryllium. After showing the bulk properties calculated herein agree well with experimental data, we calculated the formation energy of a single-vacancy and henceforth propose an estimate of 0.72 eV. This value is discussed with regard to previous theoretical and experimental studies.

Leaching Tests of the Tritium Waste Immobilized in New Cement Mixtures

The study was conducted in order to determine the immobilization performance of low-level tritium waste in new cement mixtures. The grouts analyzed are fine mortars, fluid, self- compacting, with flowability, able to fill the smallest gaps in the solid waste container. The grouts curing showed compact and structural integrity without pores and cracks, so as to ensure radioactive tritium waste encapsulation.Two types of solid/liquid tritium radioactive waste with known tritium activity have been prepared: one type containing a hydrophilic tritium compound and the other one a hydrophobic tritium compound.The tritium waste was mixed with three different types of grout and poured in a cylindrical mould. The leaching of tritium from waste solidified/encapsulated in the cement mixtures immersed in an aqueous environment has been studied in order to select the most appropriate grout type as waste immobilization matrix.Samples from the liquid surrounding the cements blocks were collected at predetermined time intervals and placed in the liquid scintillation cocktail and measured. The activity of the tritium released was then calculated.

Operational Maintenance Philosophy for Tritium Processing Systems

The high contamination potential of the release of radioactive tritium facilitates the demand for and development of a stringent and comprehensive approach to operational maintenance of tritium systems. Prompt and efficient maintenance is necessary to ensure the accepted operational safety basis is adhered to and a continued safe state of operation is achieved. This will help to mitigate and avoid potential hazards that result from a tritium release to the public and facility personnel. Because of the hazards associated with a release of tritium contamination the process systems are in large kept within a series of inerted glovebox environments that must be maintained to keep structural integrity. The nature of a tritium release from a glovebox could have significant consequences for the general public as well as for personnel. As such, the maintenance philosophy is developed to help facilitate operations in the adherence to the facility’s safety code of conduct.To effectively facilitate the safe operation goals mentioned a well-defined maintenance philosophy has been developed that encompasses routine and non-routine maintenance activities. Examples of routine activities include preventative maintenance such as line-break inspections, helium leak tests to ensure components are leak tight, weld inspections and overall surveillance testing of essential components and infrastructure. Predictive maintenance also falls into this category. Predictive maintenance activities are developed over time in response to non-routine maintenance work. Non-routine maintenance or corrective maintenance activities are performed in response to a specific failure or to resolve a particular inadequacy in performance of tritium systems. When corrective maintenance is performed trends are often studied and more predictive maintenance can be scheduled to compensate for more routine failures.This technical note will identify key operational maintenance considerations which when applied, will ensure that tritium handling systems are operated safely.

Hydrogen saturation and permeation barrier performance of yttrium oxide coatings

In fusion power plants a tritium permeation barrier is required in order to prevent the loss of the fuel inventory. Moreover, the tritium permeation barrier is necessary to avoid that the situation the radioactive tritium accumulates in the first wall, the cooling system, and other parts of the power plant. Oxide thin films, e.g. Er2O3 and Y2O3, are promising candidates as tritium permeation barrier layers. With regard to the application, this is especially true for Y2O3 due to its favorably low activation behavior compared to the other candidates. Y2O3 thin films are deposited on the reduced activation steel Eurofer97 by means of magnetron sputtering. To quantify the permeation reduction factor of the Y2O3 thin films a new gas-driven deuterium permeation measurement setup was constructed. Comparing the permeation flux through a bare substrate and a coated Eurofer97 substrate, the permeation reduction factor can be determined. The measurement results suggest that the permeation reduction factor is in the same range as for Er2O3. Moreover, the morphological analysis and the permeation measurements indicate that the long term stability of the permeation barrier performance depends on the deuterium saturation in the Y2O3 thin film.

Scintillation imaging of tritium radioactivity distribution during tritiated thymidine uptake by PC12 cells using a melt-on scintillator

A scintillation image of tritium fixed in a melt-on scintillator was obtained using a charged-coupled device (CCD) imager, and a linear relationship was observed between the intensity of the scintillation image and the radioactivity of tritium. In a [3H]thymidine uptake experiment, a linear correlation between the intensity of the CCD image and the dilution ratio of cells was confirmed. Scintillation imaging has the potential for use in direct observation of tritium radioactivity distribution.

Fusion reactor fuels up with bomb ingredient

Radioactive tritium promises a bigger bang for Sandia's Z machine but poses safety issues.

Laser-Plasma Interaction in Presence of an Obliquely External Magnetic Field: Application to Laser Fusion without Radioactivity

In this paper, the nonlinear interaction of ultra-high power laser beam with fusion plasma at relativistic regime in the presence of obliquely external magnetic Geld has been studied. Imposing an external magnetic Geld on plasma can modify the density profile of the plasma so that the thermal conductivity of electrons reduces which is considered to be the decrease of the threshold energy for ignition. To achieve the fusion of Hydrogen-Boron (HB) fuel, the block acceleration model of plasma is employed. Energy production by HB isotopes can be of interest, since its reaction does not generate radioactive tritium. By using the inhibit factor in the block model acceleration of plasma and Maxwell's as well as the momentum transfer equations, the electron density distribution and dielectric permittivity of the plasma medium are obtained. Numerical results indicate that with increasing the intensity of the external magnetic field, the oscillation of the laser magnetic field decreases, while the dielectric permittivity increases. Moreover, the amplitude of the electron density becomes highly peaked and the plasma electrons are strongly bunched with increasing the intensity of external magnetic field. Therefore, the magnetized plasma can act as a positive focusing lens to enhance the fusion process. Besides, we find that with increasing θ-angle (from oblique external magnetic field) between 0 and 90°, the dielectric permittivity increases, while for θ between 90° and 180°, the dielectric permittivity decreases with increasing θ.

A Study and Analysis on Tritium Radioactivity and Environmental Behavior in Domestic NPPs

A Study and Analysis on Tritium Radioactivity and Environmental Behavior in Domestic NPPs

Fusion of Multi-Pinched Plasma Beams Converging with Spatial Symmetry**supported by the Fund for the Construction of Graduate Degree, China (No. 2014XWD-S0805)

Fusion reactions can be achieved by using deuterium from sea water as the fuel. The amount of deuterium in one gallon of sea water contains energy equivalent to three hundred gallons of gasoline. Satisfactory conditions of plasma temperature and density necessary to initiate fusion have been achieved in various research facilities. However, the confinement time is not sufficient for ignition due to plasma instabilities. Here we show that fatal plasma instabilities could be suppressed by the ingenious arrangement of multi-pinched plasma beams converging symmetrically in space based on the minimization principle of plasma potential energy. Confirmation tests are proposed using tiny wires containing deuterium. If successful, the results could lead to a feasible approach to obtaining commercial fusion power from sea water, hence without the need to use expensive and radioactive tritium as the fuel.