Concentration Of Hydrogen Isotopes Research Articles

Dynamics of Mu, H, D, and T Absorption into Pd(111): Isotope Effects

We perform quantum dynamical calculations on the absorption of hydrogen isotopes (viz., Mu, H, D, and T) into Pd(111) subsurface through the threefold fcc hollow site, under the influence of the corresponding potential energy curves, with and without surface relaxation. Our results indicate a strong mass dependent absorption process, dominated by two factors, viz., tunneling effect and interaction with the surface lattice vibration. We exhibit tunneling in absorption, esp., Mu, and surface lattice vibration predominantly affects the heavier isotopes, on the other hand, for which we observe transfer of translational energy to the surface lattice vibrational energy.

Applicability of a conical cavity as a target for generation of neutrons in a linear accelerator

Results of the study are presented, which demonstrate the applicability of targets with a tapered surface of the reaction layer for generation of neutrons in linear accelerators of hydrogen nuclides in the nuclear reactions T(d, n)4He, T(p, n)3He, and D(d, n)3He. An algorithm is proposed for calculating the neutron yield, taking into account possible changes in the concentration of hydrogen isotopes in the target with depth. As a result of computer simulations, the dependence of the neutron yield on the cone angle has been established, and the possibility has been shown of increasing the neutron yield from a target with a conical surface of its reaction layer without changing its thickness.

Impact of nuclear irradiation on helium bubble nucleation at interfaces in liquid metals coupled to permeation through stainless steels

The impact of nucleating gas bubbles in the form of a dispersed gas phase on hydrogen isotope permeation at interfaces between liquid metals, like LLE, and structural materials, like stainless steel, has been studied. Liquid metal to structural material interfaces involving surfaces, may lower the nucleation barrier promoting bubble nucleation at active sites. Hence, hydrogen isotope absorption into gas bubbles modelling and control at interfaces may have a capital importance regarding design, operation and safety.He bubbles as a permeation barrier principle is analysed showing a significant impact on hydrogen isotope permeation, which may have a significant effect on liquid metal systems, e.g., tritium extraction systems. Liquid metals like LLE under nuclear irradiation in, e.g., breeding blankets of a nuclear fusion reactor would generate tritium which is to be extracted and recirculated as fuel. At the same time that tritium is bred, helium is also generated and may precipitate in the form of nano bubbles.Phenomena modelling is exposed and implemented in openFROM® CFD tool for 0D to 3D simulations. Results for a 1D case show the impact of a He dispersed phase of nano bubbles on hydrogen isotopes permeation at an interface. In addition, a simple permeator simulation, consisting in a straight 3D pipe is exposed showing the effect of a He dispersed gas phase on hydrogen isotope permeation through different stainless steels. Results show the permeation reduction as a function of the interface area covered by He bubbles.Our work highlights the effect of gas bubble nucleation at interfaces and the importance of controlling these phenomena in nuclear technology applications.

The effect of a micro bubble dispersed gas phase on hydrogen isotope transport in liquid metals under nuclear irradiation

The present work intend to be a first step towards the understanding and quantification of the hydrogen isotope complex phenomena in liquid metals for nuclear technology. Liquid metals under nuclear irradiation in, e.g., breeding blankets of a nuclear fusion reactor would generate tritium which is to be extracted and recirculated as fuel. At the same time that tritium is bred, helium is also generated and may precipitate in the form of nano bubbles. Other liquid metal systems of a nuclear reactor involve hydrogen isotope absorption processes, e.g., tritium extraction system. Hence, hydrogen isotope absorption into gas bubbles modelling and control may have a capital importance regarding design, operation and safety.Here general models for hydrogen isotopes transport in liquid metal and absorption into gas phase, that do not depend on the mass transfer limiting regime, are exposed and implemented in OpenFOAM® CFD tool for 0D–3D simulations. Results for a 0D case show the impact of a He dispersed phase of nano bubbles on hydrogen isotopes inventory at different temperatures as well as the inventory evolution during a He nucleation event. In addition, 1D and 2D axisymmetric cases are exposed showing the effect of a He dispersed gas phase on hydrogen isotope permeation through a lithium lead eutectic alloy and the effect of vortical structures on hydrogen isotope transport at a backward facing step.Exposed results give a valuable insight on current nuclear technology regarding the importance of controlling hydrogen isotope transport and its interactions with nucleation event through gas absorption processes.

The hydrogen isotopic composition and water content of southern Pacific MORB: A reassessment of the D/H ratio of the depleted mantle reservoir

In this paper, we re-investigate the isotopic composition of hydrogen in MORB and the possible effects of contamination on δD and water content. A suite of 40 N-MORB from the Pacific–Antarctic ridge, far from any hotspot, was analyzed for chlorine content by electron microprobe and for water content and δD with silica tubes. Cl concentrations (from 29 to 2400 ppm) indicate widespread contamination, more intense with faster spreading rates, while water contents (from 840 to 7800 ppm) are mainly controlled by igneous processes. δD values range from −76 to −48‰, with an average value of −61‰. The lack of correlation between Cl content and either H2O/Ce or δD indicate that contamination has a negligible effect on δD for our samples, which is therefore characteristic of the mantle below the Pacific–Antarctic ridge. We suggest that the 20‰ lower δD value reported for the North Pacific and North Atlantic is highly unlikely from geodynamical arguments. We propose that the convecting mantle is characterized by a δD of −60±5‰, as supported by the most recent data from North Atlantic N-MORB.

Radiation enhanced deuterium absorption for Al2O3 and macor ceramic

Absorption, diffusion, and desorption of hydrogen isotopes are expected to occur during operation in future fusion reactors and these processes will strongly depend on the irradiation conditions, neutron flux and purely ionizing radiation. The main aim of the work is to address the ionizing radiation induced absorption of hydrogen isotopes in Al2O3. Thermo stimulated desorption (TSD) measurements were carried out for both electron irradiated and unirradiated samples in order to evaluate the possible radiation enhanced retention of the previously loaded deuterium. Deuterium enhanced absorption and stabilization have been observed. TSD measurements indicate that the temperature for desorption release of the previously absorbed deuterium increases due to the ionizing radiation.

Geochemical characteristics and identification of thermogenic CBM generated during the low and middle coalification stages

Six woody peat samples were heated to 150, 250, 300, 350, 370, and 400°C to determine their geochemical characteristics and identify whether the coal bed methane (CBM) was thermogenic or secondary biogenic. The experiments were conducted in a closed pyrolysis system, from which the generated pyrolysis gas was collected. The composition of the gas and its carbon and hydrogen isotope concentrations were also determined. The results indicate that methane and carbon dioxide were the main hydrocarbon and non-hydrocarbon gases generated from the samples. The carbon isotopic compositions of the generated methane, ethane, and propane became initially lighter and then heavier with increasing experimental temperature; conversely, the hydrogen isotopic composition of the generated methane and the carbon isotopic composition of the generated carbon dioxide became gradually heavier. Therefore, a strong positive correlation exists between the aforementioned parameters. In addition, relationships have been established between carbon and hydrogen isotopic contents and Ro values, and a model for the identification of the maturity and relative content of thermogenic CBM is proposed. Then, the model was applied in a case study to evaluate the gas source of CBM in the Luling CBM field in Anhui Province, China.

Tritium absorption of co-deposited carbon films

Co-deposited carbon film with different deuterium concentration, D/C, were exposed to tritium gas at the temperature of 423K, and then the atomic ratio of absorbed tritium to carbon, T/C, was evaluated. The obtained data were discussed with crystal structure of the carbon film. The T/C increased with decreasing D/C of carbon film. The carbon film with low D/C had more defective structure. The reduction of D/C by the heating before tritium exposure led to the increase of absorption amount. These results suggest that carbon film with more defective structure and low D/C film could absorb large amount of tritium. The hydrogen isotope concentration in the present experiment was saturated below the orders of 10−4, which was 3–4 orders of magnitude smaller than that of co-deposited carbon film with hydrogen isotope.

One-dimensional simulation of hydrogen isotopes diffusion in composite materials by FVM

Tritium diffusion and permeation in construct materials is one of the most important problems in fusion material research. For the tritium concentration evaluation within each sub-system of the fuel cycle of ITER, a finite volume computer program was developed for diffusion analysis of hydrogen isotopes in composite materials. The program calculates hydrogen isotope concentration distributions through composite materials such as tritium permeation barriers as function of the applied boundary conditions. The program can simulate hydrogen isotopes diffusion through single materials and composite materials in one-dimensional and can also make the output visualization. We look forward to making some comparison calculation for the present calculation with TMAP.

Heat Evolution from Pd Nano-powders Exposed to High-pressure Hydrogen Isotopes and Associated Radiation Measurements

Using a twin system for hydrogen absorption, experiments on heat evolution and charged particle generation by D2 (H2) gas absorption in nano-sized Pd powders were done for the 0.1 μm. Pd powder, the Pd-black, and the mixed oxides of Pd·Zr, Pd·Ni·Zr and Ni·Zr. It has been found that the D(H)/Pd loading ratio and the absorption energy per D (H) is an increasing function of fineness of the sample surface. The Pd·Zr oxide nano-composites showed anomalously large energies of hydrogen isotope absorption as well as large loading ratio in the phase of deuteride/hydride formation. Although the samples were deteriorated by the repeated baking-hydrogenation cycles, an artificial oxidation of the PZ and the PNZ samples recovered the excellent original performances, and gave hydride formation energies of 1.5–2.3 eV/D and 1.5–2.0 eV/H, which are anomalously high compared with values for bulk Pd metal. In the second phase after the deuteride formation, the Pd·Zr and Pd·Ni·Zr oxide composites charged exclusively with D2 sometimes gave significantly positive output, which should be subjected to repeated investigation. Nuclear reaction products including energetic charged-particles for a possible cause of the phenomena were examined using a variety of nuclear diagnostics.

Analysis of depth profiles of hydrogen isotopes in structural materials via reflected electron spectroscopy

Methods for measuring the layer-by-layer profiles of hydrogen in structural materials based on interpretation of the energy spectra of electrons reflected within a given spatial angle are discussed. Elastically reflected spectroscopy makes it possible to determine the hydrogen isotope content, but its implementation requires an energy resolution on the order of 1 eV. In the experimental implementation of the method based on analysis of the domelike part of the spectrum of reflected electrons, the required energy resolution of an analyzer is about 1%. Such a level of resolution makes it possible to measure the spectrum for several seconds. The possibilities of this method are illustrated with the use of hydrocarbon coatings.

Modeling of diffusivity of tritium interacting with F centers in Li2O

The diffusivity of tritium interacting with F centers in Li2O was modeled with a kinetic Monte Carlo simulation and classical diffusion theory. The migration energy and trapping/detrapping energy were set according to the previous studies using quantum mechanical calculations. The constructed mode clearly showed that the tritium diffusivity was lowered by F centers. It was also shown that the diffusion coefficient of tritium interacting with F centers depended not only on the concentration of F centers and on the trapping/detrapping energy, but also on the concentration of hydrogen isotopes (H+D+T). It was indicated that inclusion of hydrogen isotopes (H2, D2, etc.) in purge gas would suppress the influence of radiation defects on the tritium diffusivity, and thus reduce the uncertainty, which is caused by radiation defects, in tritium recovery rate under fusion reactor conditions.

Anomalous effects in charging of Pd powders with high density hydrogen isotopes

A twin system for hydrogen absorption experiments has been constructed to replicate the phenomenon of heat and 4He generation by D 2 gas absorption in nano-sized Pd powders reported by Arata and Zhang, and to investigate the underlying physics. For Pd ⋅ Zr oxide nano-powders, anomalously large energies of hydrogen isotope absorption, 2.4 ± 0.2 eV / D-atom and 1.8 ± 0.4 eV / H-atom , as well as large loading ratio of D / Pd = 1.1 ± 0.0 and H / Pd = 1.1 ± 0.3 , respectively, were observed in the phase of deuteride/hydride formation. The sample charged with D 2 also showed significantly positive output energy in the second phase after the deuteride formation.

Thermal transport properties of hafnium hydrides and deuterides

The thermal conductivities of δ′-, δ-, δ+ε-, and ε-phase hafnium hydrides and deuterides with various hydrogen isotope concentrations (HfH x , 1.48 ⩽ x ⩽ 2.03; HfD x , 1.55 ⩽ x ⩽ 1.94) were evaluated within the temperature range of 290–570 K from the measured thermal diffusivity, calculated specific heat, and density. The thermal conductivities of δ′-, δ-, δ+ε-, and ε-phase HfH x and HfD x are independent of the temperature within the range 300–550 K and are in the range 0.15–0.22 W/cm K and 0.17–0.23 W/cm K, respectively; these values are similar to and lower than the observed thermal conductivities of α-phase Hf. The experimental results for the electrical resistivities of δ′-, δ-, δ+ε-, and ε-phase HfH x and HfD x and the Lorenz number corresponding to the electronic conduction, obtained from the Wiedemann–Franz rule, indicated that heat conduction due to electron migration significantly influences the thermal conductivity values at high temperatures. On the other hand, heat conduction due to phonon migration significantly affects the isotope effects on the thermal transport properties.

降水の高時間分解能自動サンプリングのための装置開発

To develop a suitable water collection method for short-term hydrological process observation, the new water sampler, using automatic water sampler and modified plastic bucket with clock timer and electro magnetic valve, was developed. The actual application of this sampler in a study area shows that this system is applicable for the rainwater sampling for the throughfall intensity over 0.7 mm⁄h.The comparison result between isotopic content of hourly samples collected by this sampler and that of conventional bulk samples for selected four representative rainfall events shows that the weighted mean value of hydrogen and oxygen isotopic content in throughfall samples by this method showed almost same content as that in bulk throughfall samples. In addition, the isotopic content of the bulk throughfall samples in the δ-diagram was plotted on the regression line given by isotopic content of hourly throughfall samples of the specific rainfall event. This means that the precise time resolution samples collected by this new method represent time variation of isotopic content in the throughfall of the study area.

An object Kinetic Monte Carlo Simulation of the dynamics of helium and point defects in tungsten

In the near surface of plasma facing materials, high concentrations of hydrogen and helium isotopes can build up, which will interact with the point defects resulting from the bombardment of the surface as well as with the impurities of the materials. It is important to develop an understanding of the evolution of W microstructure in such conditions and to be able to model this evolution. The task is very complex, as many elements have to be included in the model which must be all parameterized correctly. Isochronal annealings experiments are simple experiments which can help in the making of more complicated models. In this work, an object Kinetic Monte Carlo technique parameterized on ab initio calculations as been used to model He desorption in W. The He atoms and the self interstitial atoms have been found to be very mobile but they can bind quite strongly with impurities such as carbon or molybdenum atoms. The evolution of the number of defects in the Kinetic Monte Carlo simulation was found to be in good agreement with the resistivity changes observed during an He desorption experiment of above threshold He implantation in a thin wire of tungsten.

Experimental studies on the hydrogen isotope recovery using low-pressure palladium membrane diffuser

In this paper, we introduce a set of low-pressure palladium membrane diffuser designed to recover hydrogen isotopes from inert mixture gases. Several gaseous mixtures (D 2/Ar and D 2/He) with different deuterium concentration have been used for cleanup test of the low-pressure palladium membrane diffuser at 723 K. Effect of the composition of feed gas on the pressure of permeate side has been observed by gas chromatography (GC) and pressure sensor. With the feed flow rate of the mixture gases increasing, the D 2 permeate pressure is increasing as well. Decontamination factor (DF) of more than 1000 and recovery efficiency greater than 99.9% have been obtained by controlling the feed gas flow rate. The same palladium membrane diffuser was used to process helium-3 gas with more than 10% hydrogen isotope and about 0.3% tritium gas. The pure helium-3 (above 99.4%) with low content of hydrogen isotopes (about 0.084%) has been obtained. Recovery efficiency of all hydrogen isotopes is 99.5% above.

Mapping of hydrogen isotopes with a scanning nuclear microprobe

Elastic recoil detection analysis using heavy ions with a scanning nuclear microprobe was applied to determine the content of hydrogen isotopes in carbon material facing fusion plasma in the JET fusion reactor. The hydrogen and deuterium concentrations in re-deposited material were obtained by mapping a cross sectional cut of a wall sample. De-trapping and hydrogen release caused by the primary ion beam were investigated. For both the deuterium and hydrogen concentration a drop of ∼75% was observed from an extrapolated initial value to a final steady state region. A procedure was used to determine the initial concentration. In this way a mapping of the initial deuterium concentration could be obtained.

Isotope effects in thermal neutron transmission and backscattering processes for ε-phase zirconium hydrides and deuterides

Distributions of hydrogen isotope concentrations in ε-phase zirconium hydrides and deuterides (ε-ZrH x and ε-ZrD x : 1.8 < x < 2.0) were investigated by neutron radiography (NRG). The NRG images of the thermal neutron transmission and backscattering revealed hydrogen concentration dependence and isotope differences. The thermal neutron mass attenuation coefficients in relation to the hydrogen isotope concentrations were determined from the transmission NRG images. The results showed the isotope effects of the thermal neutron mass attenuation coefficients for ε-ZrH x to be about 6–9 times higher than those for ε-ZrD x . The neutron scattering processes for transmission and backscattering NRG images of ε-ZrH x and ε-ZrD x were also analyzed using a general Monte Carlo neutron-particle transport (MCNP) code.

APPLICATION OF TREE-RING ISOTOPIC ANALYSES TO RECONSTRUCT HISTORICAL WATER USE OF RIPARIAN TREES

Historical patterns of water source use by trees inferred from long-term records of tree-ring stable isotopic content could assist in evaluating the impact of human alterations to natural stream flow regimes (e.g., water impoundments, stream flow diversions, and groundwater extraction). Our objective was to assess the utility of the hydrogen stable isotopic composition (SD) of tree rings as an index of historical water source use by riparian trees. We investigated the influence of site conditions that varied in climate and hydrology on the relationship between deltaD of Populus xylem water (deltaD(xyl)) and tree-ring cellulose (deltaD(cell)). deltaD(xyl) and deltaD(cell) were strongly correlated across sites (r2 = 0.89). However, the slope of this relationship was less than 1, indicating that factors other than deltaD(xyl) influenced deltaD(cell). Inverse modeling with an isotopic fractionation model for tree-ring cellulose suggested that the lack of one-to-one correspondence between deltaD(xyl) and deltaD(cell) was due to the influence of the hydrogen isotopic content of the atmospheric water vapor (deltaD(atm)). Empirically measured values of deltaD(cell) were typically within the seasonal range of deltaD(cell) predicted from the fractionation model. Sensitivity analyses showed that changes in deltaD(xyl) generally had a greater influence at high-elevation montane sites, whereas deltaD(xyl) and deltaD(atm) had about equal influence on deltaD(cell) at low-elevation desert sites. The intrasite relationship between deltaD(cell) and deltaD(xyl) among individual trees was poor, perhaps because of the within-site spatial variation in hydrologic conditions and associated tree physiological responses. Our study suggests that historical variation in deltaD(cell) of Populus provides information on historical variation in both time-integrated water source use and atmospheric conditions; and that the influence of atmospheric conditions is not consistent over sites with large differences in temperature and humidity. Reconstruction of xylem water sources of Populus in riparian ecosystems from deltaD(cell) will be more direct at higher elevation mountain sites than at low-elevation desert sites.