Deuterium Permeation Research Articles

Formation of hydrogen resistant oxides of titanium alloy in water corrosion environment

The structure changes and hydrogen permeation behavior of Titanium alloy TA17 in simulated water environment of small modular reactor (SMR) at 320°C for 8000h was investigated. We found a corrosion layer consist of TiO2 and FeTiO3 with a good hydrogen permeation resistance. The structure and hydrogen permeation resistance change with the increase of corrosion period. At the first corrosion period of 3000h, FeTiO3 grows rapidly with an exponential parameter of 0.663 fitted by parabolic law. As the initial TiO2 layer destroyed, the deuterium permeation flux increases. After the thickness of FeTiO3 reaches a limit at corrosion time of 4000h, there exists a dynamic balance between the growth and the dissolution of FeTiO3, result in a small fluctuant deuterium permeation flux at corrosion periods of 5000－8000h. The deuterium permeation flux of the corrosion layer can be two orders of magnitude lower to that of Titanium alloy TA17 substrate. The formation process of corrosion layer and its effect on hydrogen permeation resistance are discussed in detail.

Tailored Permeation Through ≈1 nm Thick Carbon Nanomembranes by Subtle Changes in Their Molecular Design.

Due to their nanoscale thickness (≈1 nm) and exceptional selectivity for permeation of gases, nanomembranes made of 2D materials possess high potential for energy-efficient nanofiltration applications. In this respect, organic carbon nanomembranes (CNMs), synthesized via electron irradiation-induced crosslinking of aromatic self-assembled monolayers (SAMs), are particularly attractive, as their structure can be flexibly tuned by choice of molecular precursors. However, tailored permeation of CNMs, defined by their molecular design, has not been yet demonstrated. In this work, it is shown that the permeation of helium (He), deuterium (D2) and heavy water (D2O) for CNMs synthesized from biphenyl-based SAMs on silver (C6H5-C6H4-(CH2)n-COO/Ag, n = 2-6) can be tuned by orders of magnitude by changing the structure of the molecular precursors by just a single methylene unit. The selectivity in permeation of D2O/D2 with an unprecedented value of 200000 can be achieved in this way. The temperature-dependent study reveals a clear correlation between the molecular design and the permeation mechanisms facilitating therewith tailored synthesis of molecular 2D materials for separation technologies.

Effect of Deuterium Loading on Permeation of Deuterium Through Niobium at Relative Low Pressure

Effect of Deuterium Loading on Permeation of Deuterium Through Niobium at Relative Low Pressure

Deuterium permeation studies through bare and Er2O3 coated SS 316L

Hydrogen isotope permeation through the structural walls of a fusion reactor poses concern for both fuel loss and safety. A primary focus in the International Thermonuclear Experimental Reactor (ITER) is the reduction of hydrogen isotopes, particularly tritium permeation through structural materials. In this work, an experimental setup has been developed to study the permeation of deuterium through thin samples such as bare and erbia (Er2O3) coated 100 µm thick stainless steel (SS 316 L). Permeation results through a bare SS 316 L sample yielded deuterium diffusivity and permeability of SS 316 L. Erbia coating on SS 316 L was developed using dip coating technique and its performance was tested as a permeation reduction barrier (PRB). A permeation reduction factor of ∼87 and 359 have been achieved with coating thickness ∼ 100 and ∼200 nm respectively. No measureable permeation flux was obtained for coating thickness of 492 nm. These results indicate the effectiveness of erbia coating in reducing deuterium permeation through SS 316 L.

Multi-layer structured AlN/Er2O3 coating: Enhanced thermal stability and hydrogen isotope permeation resistance

AlN/Er2O3 multi-layer coatings, as a novel hydrogen isotope permeation barrier for nuclear reactor and hydrogen energy field, were prepared by magnetron sputtering coupled with metal-organic decomposition on the surface of reduced activation ferrite/martensitic steel. The thickness of the Er2O3 layers was adjusted by spin coating several times, the adhesion of the layers was tested with a micron scratch tester, and the microstructure and surface composition of the layers were analyzed by TEM and XPS. The results indicate the absence of evident crack holes on the coating surface, uniform distribution of elements without segregation, and satisfactory densification. In comparison with the individual Er2O3 coating, the multi-layer coating incorporating AlN as the interlayer exhibits enhanced adhesion strength, which could effectively mitigate the thermal mismatch phenomenon of Er2O3 under high temperature conditions. Electrochemical hydrogen permeation and high temperature gas pressure driven deuterium permeation tests demonstrated that the permeability resistance of the AlN/Er2O3 coating does not linearly increase with its thickness. The hydrogen permeation reduced factor of the coating reaches its maximum value when the thickness of the Er2O3 coating is 1500 nm.

Preparing high performance FeAl/Al2O3 coating as tritium permeation barrier

Preparation of tritium permeation barrier (TPB) coating on the surface of structural materials is one of the most effective solutions to solve the issue of tritium permeation in tritium breeder blanket. The FeAl/Al2O3 coating is considered as the most promising candidate material for TPB coating due to its low hydrogen isotopes permeability, good adhesion and excellent radiation resistance. However, the current reported performance of FeAl/Al2O3 coating is much lower than its theoretical value. This work proposed a three-step process to prepare FeAl/Al2O3 TPB coating. By magnetron sputtering deposition, aluminizing and in-situ oxidation, a layer of high quality γ-Al2O3 about 250 nm thick was successfully formed on the 304 stainless steels. The Al2O3 layer was dense and no obvious defects were found. The gas-driven permeation measurements showed that the coating sample had strong ability to inhibit deuterium permeation, where the deuterium permeation flux was reduced by 5 orders of magnitude compared to the uncoated one at 600 °C, which is the best reported performance. Meanwhile, the thermal shock resistance test showed that the coating had no cracks after 50 thermal cycles. Moreover, the coating had a high electrical resistivity of approximately 3.42 × 1014 Ω cm, which could effectively reduce the magneto-hydrodynamic pressure drop (MHD) effects.

Deuterium permeation and retention behavior in copper-based brazing filler materials

Copper-based brazing filler materials are commonly employed in vacuum brazing techniques to achieve joining of plasma-facing components for ITER. In this work, gas-driven permeation (GDP) and thermal desorption spectroscopy (TDS) experiments have been performed to study the hydrogen isotopes permeation and retention behavior in two types of brazing filler materials (CuMnNi and CuGeNi metals). Experimental results show that CuMnNi filler exhibits the similar deuterium (D) permeability with CuMnNi filler but lower diffusion coefficients than CuGeNi filler. Three distinct peaks are observed between 380 K and 980 K for CuMnNi filler. However, no evident desorption peak is observed for CuGeNi filler. CuGeNi filler may be considered as a potential brazing filler material for reducing tritium inventory.

Deuterium permeation performance of V4Cr4Ti/RAFM steel joint with in-situ formed carbide interlayer during diffusion bonding

Vanadium alloy (V4Cr4Ti) is a structural material used in future fusion reactors owing to its inherent advantages of high-temperature strength and neutron irradiation resistance. Oxygen pickup and high hydrogen isotope permeability are the two major concerns for their application in various types of blankets. To solve these issues, a bimetallic joint was designed with a CLF-1 layer of reduced-activation ferritic/martensitic (RAFM) steel to resist corrosion and a CLF-1/V4Cr4Ti bonding interface to suppress hydrogen isotope permeation. Samples were prepared from joints bonded via solid-state diffusion under hot isostatic pressing (HIP). Deuterium (D) gas permeation tests were performed at various temperatures in the range 400–600 °C at 100 kPa. After deuterium permeation tests, the thermal desorption spectra (TDS) of the samples were analyzed. And the permeation behavior of deuterium atom across the joints was schematically discussed. The results showed that bonding with steel could be an effective solution for resisting hydrogen isotope permeation through the V4Cr4Ti alloy. Thermal desorption spectrum (TDS) analysis of the tested samples revealed a desorption peak temperature equivalent to that of TiC. The formation of a 1 µm-wide B2 ordered α'- [Fe, (V, Ti)] phase layer, together with a large number of dispersed carbides around the interface, played a significant role in the deuterium permeation resistance. In addition, microstructural changes in the steel base material after the 900 °C bonding process were beneficial for suppressing deuterium diffusion.

Hydrogen isotope transport parameters in materials for tritium extraction systems. Focus on the low pressure

This work aims to fill a gap in the H transport database for niobium and vanadium, materials proposed for the fabrication of tritium extraction systems. The permeability, key parameter for this application, has not been properly determined in niobium so far. Values are given for H2 and D2 permeability in two different Nb samples from different suppliers but with similar microstructure from ∼300 °C to 500 °C and tested with loading pressures from 20 mbar to 500 mbar:ϕ(Nb/H2)[mol·m−1·s−1·Pa−0.5]=4.49·exp(−19,258T)ϕ(Nb/D2)[mol·m−1·s−1·Pa−0.5]=1.31·exp(−19,332T)For vanadium, new measurements for material from different suppliers and with very different microstructure allow to confirm values for the permeability recently published (in contrast to the traditionally accepted values indirectly derived from solubility and diffusivity). In this work, the following expression is given for deuterium:ϕ(V/D2)[mol·m−1·s−1·Pa−0.5]=1.31·exp(−11,603T)There are very few documented attempts to measure surface rate constants for either of the two materials under consideration. These parameters are especially important and define the permeation process under certain conditions, in particular at low pressures. Hydrogen and deuterium permeation data in Nb and V has been therefore obtained in a wide range of pressures, with special focus in the low pressure region, the role of the microstructure being also evaluated. Surface rate constants σk1 and σk2, which are fundamental parameters for the modelling of H isotope transport through the materials, have been determined in vanadium and niobium with different surface finishes, this factor resulting determinant of the result.

Improving hydrogen isotope permeation resistance of (TiVAlCrZr)O multi-component metal oxide coating by O+ Ion implantation

Oxygen vacancy can greatly affect the performance of metal oxide to hydrogen isotope permeation resistance. In this work, we report a new strategy to improve the permeation resistance by oxygen ion implantation. A (TiVAlCrZr)O multi-component metal oxide film was prepared as a tritium permeation barrier on a 316 L substrate by RF magnetron sputtering deposition, and then implanted by oxygen ions to fill the oxygen vacancies inside. The grazing incidence X-rays (GIXRD) analysis showed that the pristine and the oxygen-implanted coatings were in an amorphous phase. The deuterium permeation resistance of the four coatings was tested by a gas-driven device. The result showed that the pristine coating had a permeation reduction factor (PRF) of 5,610 at 500 °C, while there was a 13.6 times of increase in PRF with an oxygen concentration of 11.4 at.% with the best-reported value of 76,500, and more oxygen ions implanted, the better the deuterium permeation resistance of the coating. The GIXRD showed that after the test the pristine coating remained amorphous, while some crystals were formed in the oxygen-implanted coating with an oxygen concentration of 11.4 at.%. Oxygen ion implantation enhanced the deuterium permeation resistance by filling the oxygen vacancies and forming of more stable state of amorphous multi-component metal oxide, which is expected to be a new type of deuterium permeation barrier.

Deuterium permeation of low-activation vanadium alloys possible for reuse in a short time in fusion reactors

Low-activation vanadium (V) alloys are alternative to reduced-activation ferritic/martensitic steels for the blanket structural material. To make the reusage of the alloys possible in a short time, new-design concepts of V alloy have been suggested in National Institute for Fusion Science. In the present study, the deuterium permeation properties of the new-designed V alloys were investigated.The new-designed V-4Cr-4Ti alloy samples with high and low purity, named H44 and L44, respectively, were used. For comparison, the NIFS-HEAT-2 V alloy samples, named NH2 were also used.It was found from the permeation experiments that deuterium permeability coefficient of L44 was smaller than that of NH2, while the permeability coefficient of H44 was comparable with NH2. These results suggest the permeation coefficient of D of the new-designed V alloy was similar to those of the conventional V alloy, if Ti and O content was the same. Estimated activation energies of diffusion and permeation indicated that the permeation behaviors significantly depended on titanium oxides at the surface and in the bulk. Data obtained by a microscope with Auger electron spectroscopy indicated that the concentration and the composition of the oxide must change with air exposure during the maintenance and with hydrogen isotope exposure during the reactor operation. The obtained results suggest these changes of the concentration and the composition result in the change in the permeation characteristics of hydrogen isotopes.

A novel method for preparing α-Al2O3 (Cr2O3)/Fe–Al composite coating with high hydrogen isotopes permeation resistance

α-Al2O3 as a preferred material for hydrogen isotopes permeation barrier (HIPB) can effectively prevent hydrogen embrittlement in structural steel and has higher thermal stability. However, its application is limited by the issue that it is hard to prepare α-Al2O3 at relatively low temperature and its formation temperature is too high (>1000 °C) to damage the mechanical properties of structural steel. To overcome this issue, this paper presents a novel method (combining Al electrodeposition, aluminizing, Cr deposition and air oxidation) for the preparation of α-Al2O3 (Cr2O3)/Fe–Al composite coating on 316 L stainless steel for the first time. The formation temperature of α-Al2O3 was successfully reduced to 800 °C. The post-oxidation samples were characterized by SEM, XPS, XRD, EDS and TEM. The results showed that the oxide film was composed of highly crystalline α-Al2O3 and Cr2O3 nanoparticles, where the later were diffusely distributed in the internal α-Al2O3 film. And there was an epitaxial growth relationship between α-Al2O3 and Cr2O3. The low-temperature formation of the α-Al2O3 film was due to the fact that the Cr2O3 nanoparticles formed during the oxidation process acted as templates and nucleation sites, which reduced the nucleation barrier of α-Al2O3. Deuterium permeation tests showed that its deuterium permeation reduction factor (DPRF) was 8892 at 500 °C, which met the standard for practical application.

Determination of the Surface-Rate Coefficients of Deuterium Through Nickel by Gas-Driven Permeation Experiments in Surface-Limited Regime

Tritium permeation through structural materials of fusion reactors is an important issue from both safety and tritium self-sufficiency points of view. Mutual influences among hydrogen isotopes are also important in assessments of tritium permeation fluxes, and although some theoretical and experimental works have been carried out so far—which have all focused on steady-state permeation—their conclusions are insufficiently clear about how one isotope affects the permeation of another. This was motivation to further investigate this problem, both theoretical and experimental in a non-steady-state approach and also in the surface-limited regime (SLR) of permeation. After initial theoretical work, a dedicated experimental installation for gas-driven permeation experiments was designed and assembled. Then, initial experimental work was completed for testing monoisotope permeation of deuterium through a very thin (0.075-mm) nickel membrane in the temperature range of 473 to 773 K and for a driving pressure of deuterium gas in the range of 10−2 to 1 Pa. This work was done in preparation for subsequent multi-isotope experiments, with the proposed goal to observe how hydrogen affects the permeation of deuterium. The main objectives of the work were to confirm experimentally the achievement of the SLR of permeation for the selected conditions of testing; to determine experimentally the kinetic coefficients of surface transport for deuterium in nickel; and to test and validate the experimental setup, procedures, and methods used and their reliability to more stringent requirements of the multi-isotope experiments. Within this paper, the experimental setup and all the operating procedures used both in calibration operations and in permeation experiments are presented in detail, as well as their results. The obtained results confirmed that permeation occurred in the SLR in the tested range of pressure for each testing temperature. The surface-rate coefficients of dissociation and recombination were both determined experimentally. The values obtained for the dissociation coefficient were in very good agreement with other similar experimental data available in the literature. For the recombination coefficient, agreement was not quite satisfactory, but comparison could be made with values calculated based only on the dissociation and solubility coefficients, as data for these coefficients for the nickel-hydrogen system (determined directly from gas-driven permeation experiments) were not found in the literature. However, these results indicated good reliability of the installation, its calibration, and operating procedures in order to proceed to experimental testing of multi-isotope permeation.

Deuterium permeation and lithium‑lead corrosion behaviors of ceramic‑iron joint coating

In fusion reactor blanket design, the main challenges are to control the permeation of tritium and prevent the corrosion of the structural materials. This study focuses on investigating the behavior of ceramic‑iron joint coatings in terms of deuterium permeation and Li-Pb corrosion aiming to develop effective barriers against permeation while providing corrosion protection. The research involved fabricating ZrO2 and Fe2O3 ceramic coatings on F82H steel substrates using metal-organic decomposition followed by joining the coated samples with Fe foils using a hot press machine. Deuterium permeation measurements were conducted to assess the effectiveness of the coating, and liquid Li-Pb exposure tests in a flow environment were performed to evaluate its resistance against corrosion. The results showed that the coating reduced deuterium permeation flux by a factor of 2000 at 400 °C and 7000 at 550 °C compared to uncoated samples suggesting an improved crystallinity or grain growth without degradation due to the joining process. Furthermore, the corrosion layers formed on the surface of the Fe layer after the flowing Li-Pb exposure test. Although this layer gradually decreased in thickness over time while not significantly affecting the underlying Fe layer's thickness. This observation indicates that the corrosion layer performed mitigating the corrosion rate of the Fe layer. This paper aims to demonstrate how ceramic‑iron joint coatings can be compatible with the advanced fusion reactors.

Deuterium Permeation Through a Self-Supported Palladium-Silver Membrane in Helium Gas Mixtures

Deuterium Permeation Through a Self-Supported Palladium-Silver Membrane in Helium Gas Mixtures

Apparatus design of operando hydrogen microscope for visualization of time-dependent distribution of hydrogen

The operando hydrogen microscope is an original apparatus that has been developed to visualize the time-dependent permeation of hydrogen through a sample. This apparatus is developed based on an ultrahigh vacuum scanning electron microscope (UHV SEM). The system consists of a lens system to focus ions produced by electron-stimulated desorption (ESD), an ion detector optimized for ESD-signal detection, and a two-dimensional measurement program synchronized with the position information of the electron beam. The developed detectors and electrostatic lenses enable highly sensitive detection of the ions. In this paper, we show the details of the instrumentation of the operando hydrogen microscope. We have succeeded in recording hydrogen and deuterium flowing from the rear of metals to the surface as a series of time-lapse images, showing the time-dependent changes in the surface distribution of hydrogen and deuterium. Deuterium permeation through the metal sample was dynamically visualized at the surface by the two-dimensional mapping of the desorbed ions induced by scanning electron beam irradiation.

Optimization of alumina tritium permeation barrier with consideration of the thickness and the surface coverage

Alumina is considered as one of the most promising candidates for tritium permeation barrier. Coating preparation parameters such as the thickness and the surface coverage both affect the hydrogen isotope resistant performance of TPBs. Alumina coatings with thickness in the nanometric scale are considered in this work. Reduced thickness in the coatings leads to an improvement in the thermal conductivity and the reduction of mismatch problems with the substrate due to differences in the thermal expansion coefficients. Alumina coatings with different thickness were prepared on differentiated manufactured substrate by radio frequency magnetron sputtering with varying sputtering time. Deposited alumina layers are maximal 104.2 nm in thickness. Gas-driven permeation experiments have been performed to investigate the deuterium permeation behavior of the coating samples. It is noted that the alumina coating with only approximately 100 nm in thickness whose permeation reduction factor could achieve 1784 at 823 K and maintain its excellent performance at elevated temperatures, which indicates that the coating at nanometer scale with high surface coverage is capable of possessing extraordinary hydrogen permeation resistance property.

Investigation of gas and plasma driven deuterium permeation through a vanadium membrane for particle exhaust application in a fusion reactor

The process of particle exhaust based on the cryopump in fusion reactor presents a severe issue of deuterium and tritium retention. However, the metal foil permeation pump represents an effective means to solve the problem of deuterium and tritium retention during the particle exhaust process. How to enhance the permeability performance of metal films to meet the requirements of practical engineering applications of fusion reactor is the main content of the research. This article focuses on the simulation and experimental investigation of V membrane, aiming to explore methods for enhancing membrane permeation flux. Through simulation analysis, the influence of thickness, membrane surface state, and temperature on both plasma-driven and gas-driven permeation has been studied. Among these, the downstream surface condition is changed during the PDP process, resulting in an almost twofold increase in permeation flux. Based on the permeation experiments the influence of temperature on permeation was proved and the impact of plasma source power on permeation was also studied. It was found that the permeation flux increased more than two orders of magnitude when the radio frequency power changed from 0 to 500 W, which indicates that plasma incident flux serves as a more effective means to enhance permeation flux compared to temperature.

Hydrogen and deuterium permeation in Hastelloy N

Hastelloy N was chosen as the fluoride salt-contacting structural material for the Molten Salt Reactor Experiment due to its excellent compatibility with the fuel salt FLiBe. FLiBe is currently investigated for several advanced fusion and fission reactor concepts where tritium generation in the FLiBe is anticipated. Knowledge of hydrogen transport properties through Hastelloy N is important to understand how tritium would permeate through this material and result in an unintentional release. In this study, the hydrogen and deuterium permeability, diffusivity, and solubility were measured from 500 to 700 °C at a primary-side pressure of 10 kPa in a well-characterized sample of Hastelloy N. The prepared polycrystalline Hastelloy N had C and O impurities present on the surface. These impurities were investigated using Auger Emission Spectroscopy and Ar depth profiling. The adventitious C was removed upon the first Ar sputter cycle whereas O persisted deeper into the sample. For permeation experiments, applied deuterium pressures ranged from 13 Pa to 100 kPa and deuterium transport remained in the diffusion-limited regime (J ∝ P0.5) throughout the pressure range examined. Two methods are employed to measure the effective hydrogen and deuterium diffusivity: rise and decline. The decline method produced improved statistical model fits for calculating the effective diffusion coefficient compared to the rise method. The resultant transport properties compared well to published values for other nickel alloys.

Experimental Progress in the Development of a Metal Foil Pump for DEMO

Experimental findings to contribute to the preliminary design of a metal foil pump for fuel separation in the Direct Internal Recycling loop of the DEMO fusion device are presented. In parametric studies on a small-scale superpermeation experiment with a microwave plasma source and two different metal foil materials, niobium Nb and vanadium V, a substantial increase in permeation with plasma power and with a decrease in pressure was observed. To ease operation in the typical fusion environment, in-situ heating procedures were developed to recover from impurity contamination. The temperature independence of plasma-driven permeation from 600 to 900 °C metal foil temperature was demonstrated. No proof of an isotopic effect for plasma-driven permeation of protium and deuterium could be found. The highest repeatable permeation flux achieved was 6.7 Pa∙m3/(m2∙s) or ~5.5 × 10−3 mol H/(m2∙s). The found compression ratios do safely allow the operation of the metal foil pump using ejector pumps as backing stages for the permeate. In a dedicated experimental setup, the operation of the plasma source in a strong magnetic field was tested. Parametric studies of pressure, power input, magnetic flux density, field gradient and field angle are presented.