Hydrogen Isotope Permeation Research Articles

Thickness impacts on permeation reduction factor of Er2O3 hydrogen isotopes permeation barriers prepared by magnetron sputtering

In hydrogen energy and thermal fusion energy, hydrogen isotopes permeation barriers (HIPB) are used to reduce hydrogen isotopes permeation, which may result in hydrogen isotopes leak and construction materials brittleness. Here, we made Er2O3 HIPB by magnetron sputtering and studied the relation between deuterium-permeation reduction factor (D-PRF) and coating thickness, micro-morphology. The 0.2 μm Er2O3 coatings can reduce deuterium permeation by 1/10 ∼ 1/20 at 600 °C ∼ 300 °C. However, the reduction ability decreases gradually with the increase in coating thickness when the coatings are thicker than 0.2 μm. The reason may be ascribed to the deuterium invasion in deuterium permeation test. After deuterium invasion into coatings, the coatings suffer intrinsic stress, thermal stress and expansion stress from deuterium invasion. As a result of grain size dependence on coating thickness in PVD-derived coatings, i.e. grains become coarse with increasing coating thickness, the sum of stresses in various type increases with increasing coating thickness. The coatings crack easily when they suffer more strong tensile stress. So, the damages of coatings become serious and D-PRF reduces with increasing coating thickness.

Study of Al2O3–Er2O3 composite coatings as hydrogen isotopes permeation barriers

Composite coatings as Hydrogen Isotopes Permeation Barriers have seldom been studied. In this work, the Al2O3–Er2O3 component composite HIPB were prepared on 316L stainless steel by radio frequency reactive magnetron sputtering. The deuterium permeation reduction factor (D-PRF), structure and nano-hardness of the Al2O3–Er2O3 composite HIPB were investigated. The Er4Al2O9 (012), (023) diffraction peaks appeared. The D-PRF of 1.2 μm Al2O3–Er2O3 composite HIPB could reach 160 at 600 °C, the D-PRF was 210 at 450 °C and increased sharply to 1380 at 250 °C. The coatings kept dense during the deuterium permeation tests while the Er4Al2O9 phases changed. The nano-hardness decreased from 9.55 GPa to 7.46 GPa after the deuterium permeation tests. It was inferred that the deuterium atoms invasion and formation of oxygen vacancies should be responsible for the performance and structure changes of the Al2O3–Er2O3 composite HIPB during deuterium permeation tests.

Performances of AlN coatings as hydrogen isotopes permeation barriers

Hydrogen isotope permeation barriers (HIPB) have great potential applications in the fields of hydrogen energy and thermonuclear fusion. In this study, the AlN-HIPB were prepared on 316L stainless steel by RF magnetron sputtering. The properties of AlN-HIPB were studied, including the deuterium permeation reduced factor (D-PRF), structures and nano-hardness. The D-PRF of 0.4μm AlN-HIPB could reach 36 at 600°C, and gradually rise with decreasing permeation temperature. The D-PRF reached 53 at 400°C and 144 at 250°C, respectively. The coatings remained dense and the grains were spherical after the deuterium permeation test. The AlN (100) diffraction peaks appeared and maintained stable during the deuterium permeation process. The nano-hardness of the coatings increased from 5.96GPa to 7.41GPa and the elasticity modulus also increased from 156.6GPa to 210.6GPa after the deuterium permeation.

Hydrogen isotope dissolution, diffusion, and permeation in Er2O3

We report the fabrication and characterization of nanocrystalline Er2O3 thin films, as well as the calculations of interstitial deuterium (D) behaviors in bulk Er2O3 using first-principles calculations based on density-functional theory. Our results show that the prepared Er2O3 thin films possess a regular cubic phase with a phase structure consisting mainly of bulk and grain boundaries. Transport of hydrogen isotopes in bulk is predicted to occur by translocation between empty interstitials (e.g., tetrahedral or octahedral sites), and involves hopping from one empty interstitial to another. The rate-determining process of diffusion and permeation is hydrogen isotope movement from tetrahedral site to octahedral site. Transport of hydrogen isotopes within grain boundaries is predicted to be dominant based on the comparison of D permeability or permeation activation energy between experiments and DFT calculations. At a typical temperature of 873 K, the solubility, diffusion coefficient, and permeability of D in bulk Er2O3 are predicted to be 2.94 × 10−15 mol m−3, 3.56 × 10−10 m2 s−1, and 3.68 × 10−27 mol m−1 s−1 Pa−1/2, respectively.

Performances of Cr2O3–hydrogen isotopes permeation barriers

Hydrogen isotopes permeation barriers (HIPB) play an important role in reducing hydrogen isotopes permeation and leakage in hydrogen energy and thermonuclear fusion energy. In this study, the Cr2O3–HIPB were prepared on 316L stainless steel by RF magnetron sputtering. The performances of the Cr2O3–HIPB were investigated, including the deuterium-permeation reduction factor (D-PRF), micro-structure and nano-hardness. The D-PRF of 0.5 μm Cr2O3–HIPB could reach 48 at 700 °C and 152 at 400 °C in the first permeation test cycle. However, it reduced to 20 at 700 °C and 89 at 400 °C in the second permeation test cycle. The (012), (104), (113) and (116) diffraction peaks occurred and the morphologies became loose after high temperature hydrogen annealing. The nano-hardness decreased by 31% from 9.1 GPa to 6.3 GPa with increasing annealing time to 64 h. It was inferred that the hydrogen isotopes invasion should be responsible for the performance evolution of the Cr2O3–HIPB under high temperatures. Furthermore, the FeCr2O4 phase formed at the interfaces as a result of element diffusion, which might contribute to the cracking of Cr2O3–HIPB.

Study on Hydrogen Isotopes Permeation in Fluidized State of Liquid Lithium-Lead

Hydrogen transfer under a fluidized condition of Li-Pb is investigated experimentally to design a Li-Pb blanket system. Li-Pb eutectic alloy flows through inside of a Ni tube in the experimental system, where H2 permeates into and out of the forced Li-Pb flow. The overall H2 permeation rate is analyzed using a mass balance model. Hydrogen atoms diffuse in Ni and Li-Pb. The steady-state H2 permeation rate obtained by this experiment is smaller than the result of the calculation model. A resistance factor is introduced to the present analysis in order to evaluate the influence of other H2 transfer mechanisms, such as diffusion in Li-Pb and dissolution reaction between Ni and Li-Pb. The contribution of the resistance to the overall H2 permeation rate becomes large when the flow rate of Li-Pb is low. This is because the boundary layer thickness between Ni and Li-Pb affects the overall H2 permeation rate. When the flow velocity of Li-Pb is large, the thickness of the boundary layer becomes thin, and the driving force of H2 permeation through Ni wall becomes large.

Mechanical Properties and Permeabilty of Hydrogen Isotopes through CrNi35WTiAL Alloy, Containing Radiogenic Helium

The paper presents research results of permeability of hydrogen isotopes through CrNi35WTiAl alloy containing radiogenic helium, and results of hydrogen and radiogenic helium impact on mechanical properties of this alloy.The impact of hydrogen and radiogenic helium on mechanical properties of CrNi35WTiAl alloy was determined by tensile tests of cylindrical samples in inert and hydrogen atmospheres. For this research samples with various concentrations of 3He (90, 230 and 560 appm) were prepared. The buildup of 3He has been fulfilled using the “tritium trick” technique. Maximal influencing of hydrogen and radiogenic helium on mechanical properties of CrNi35WTiAl was observed at 873 K on samples with 560 appm of 3He.Testing of permeability of hydrogen isotopes was made in temperature range from 723 to 973 K.

Gas- and plasma-driven hydrogen permeation through a reduced activation ferritic steel alloy F82H

The first wall of a magnetic fusion power reactor will be subjected to hydrogen isotope permeation by the two mechanisms: one is gas-driven and the other is plasma-driven. Hydrogen transport through a reduced activation ferritic steel alloy F82H has been investigated using a steady-state laboratory-scale plasma device. Permeation parameters including permeability, solubility and diffusivity have been measured in the temperature range from 150 to 520°C. The surface recombination coefficient for hydrogen has also been estimated by a one-dimensional steady-state permeation model with the input data taken from experiments. Using these parameters, the hydrogen plasma-driven permeation flux and inventory for a 0.5cm thick first wall around 500°C are estimated to be ∼1.0×1013atomcm−2s−1 and ∼2×1016atomcm−3, respectively. Also, the implications of all these data on reactor operation are discussed.

Laboratory Experiments and Modeling on Bi-Directional Hydrogen Isotopes Permeation through the First Wall of a Magnetic Fusion DEMO Reactor

The first wall of a magnetic fusion DEMO reactor serves to separate the edge plasma from breeding blanket, the latter of which is required to operate at elevated temperatures. To minimize the thermo-mechanical stress, the wall thickness is often limited to be less than 1 cm. As a result, the first wall is subjected to hydrogen isotopes permeation in the two opposite directions via plasma-driven permeation (PDP) by D+ (or D0) and T+ (or T0) in the edge plasma region and via gas-driven permeation (GDP) by T2 bred in the blanket. In the present work, the bi-directional hydrogen permeation behavior through a candidate first wall material, F82H, has been studied, using a laboratory-scale plasma device. Experimental data indicate that GDP tends to dominate the overall hydrogen isotopes transport. The effects of surface roughness and contamination on PDP have been investigated. Also, a one-dimensional diffusion code has been used to simulate bi-directional PDP and GDP under reactor-relevant conditions where multiple hydrogen isotopes flow through the first wall.

Modelling of Hydrogen Permeability of Structural Materials Through Protective Coating Defect

An efficient reduction of gaseous hydrogen isotope permeation through a metal wall is essential in several applications like hydrogen storage and distribution, hydrogen embrittlement protection, and tritium inventory in future fusion reactors like ITER. Hydrogen permeation barrier films often exhibit lower efficiency than anticipated. It is very difficult to identify and quantify the responsible mechanism since the defects can be of submicrometer dimensions and very sparsely populated. We considered hydrogen permeability through a cylindrical membrane (barrier) in the presence of protective coating defect at the inlet surface of a structural material. For various materials, when the processes of diffusion, desorption and dissolution are limiting, we present the mathematical models in the form of boundary value problems with non-linear and dynamic boundary conditions. On the basis of the implicit difference scheme, a computational algorithm of a boundary value problems solution is developed. Numerical simulation results of hydrogen permeation flux and diffusant distribution are presented. Qualitative regularities of steady state permeability regime establishment and delay times registered experimentally and depending on geometric characteristics of the membrane and physical parameters are identified.

Numerical study of the effects of physical parameters on the dynamic fuel retention in tungsten materials

Effects of different possible values of physical parameters on the fuel retention in tungsten (W) materials are studied in this work since W is considered as the primary plasma-facing surface material and fuel retention is a critical issue for next-step fusion devices. The upgraded Hydrogen Isotope Inventory Processes Code is used to conduct the study. First, the inventories of hydrogen isotopes (HI) inside W with different possible values of diffusivities and recombination rate coefficients are studied; then the influences of uncertainties in diffusivity, trap concentration, and recombination rate on the effective diffusion are also analyzed. Finally, an illustration of effective diffusion on the permeation and inventory is given. The enhancements of HI permeation flux and inventory in bulk W due to the presence of a carbide WxC layer on the PFS are explained.

Design and development of hydrogen isotope sensor in liquid PbLi

Indian LLCB – TBM uses liquid Lead-Lithium (Pb-Li) as tritium breeder, neutron multiplier and coolant. Tritium bred in liquid PbLi stream has to be recovered by tritium extraction system. Therefore, a reliable sensor with quick response time for measurement of hydrogen isotope is essential.A hydrogen isotope sensor in liquid Pb-Li, based on permeation of hydrogen isotopes through metal (sensor material) is designed. The capsule shaped sensor, made of iron membrane coated with Pd from inside (downstream side), allow hydrogen isotope to permeate through it. The design work mainly includes the selection of proper material, its thickness and surface conditions, which is to be supported by numerical calculations for optimization of maximum permeation flux, fast response and fabricability. The numerical calculation utilizes a physical model having recombination of two hydrogen isotope atoms at the surface and atomic diffusion through the bulk. In this work, design calculations based on numerical simulation and fabrication procedure of the hydrogen isotope sensor are presented.

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.

Adsorption of H atoms on cubic Er2O3 (0 0 1) surface: A DFT study

First-principles plane wave calculations based on spin-polarized density functional theory (DFT) and generalized gradient approximation (GGA) have been used to study the adsorption of H atoms on cubic Er2O3 (001) surface. We identify stable adsorption positions and find that H preferentially adsorbs on top of fourfold-hollow sites and transfers electrons to the surface, resulting in the formations of covalent bonds to the nearest neighboring four oxygen atoms. In the most energetically favorable adsorption sites, It was found that H bonds with O atoms at the cubic Er2O3 (001) surface with an adsorption energy of −295.68kJmol−1 at coverage 1/8ML, and the adsorption energy is inclined to decrease with the increase of H coverage (>1/4ML). In addition, our calculations indicate that the dissociative H atom configurations have adsorption energies that are at least 152.64kJmol−1 greater than the H2 molecule configurations on the surface. These results discussed in the context of erbium oxide slabs are employed to rationalize some processes regarding to the hydrogen isotope permeation behavior of tritium permeation barrier.

Investigating permeation and transport of H isotopes in tungsten by first-principles

We have investigated permeation and transport of hydrogen (H) isotopes in tungsten (W) single crystal employing first-principles calculations in junction with Fick’ law. Permeability was approximately evaluated according to the solubility and diffusion coefficient of H. The solubility for H in bulk W from present calculation is consistent with the experimental results measured by Frauenfelder. The permeation fluxes of H isotopes are examined at the different thickness of W wall. The permeation fluxes of deuterium with the W thickness of 21μm at the temperature of 770K and with the W thickness of 50μm at the temperature of 893K were 0.68×1013 atom/m2s and 0.34×1014 atom/m2s, respectively. The dissociation coefficients of H isotopes are also evaluated. We believe that the present first-principles combined with Fick’ law method can be also generalized to investigate permeation and transport of H isotopes in most metals since such H isotopes behaviors in most metals are similar to those of H isotopes in W.

Stability of Y2O3 hydrogen isotope permeation barriers in hydrogen at high temperatures

Hydrogen isotope permeation barriers (HIPB) have great potential applications in the fields of hydrogen energy and thermonuclear fusion energy. Here, we report the stability of Y2O3 HIPB in gaseous hydrogen at high temperatures including the structures, mechanical properties and electrical properties. With increasing hydrogen treatment time at 700 °C, the high-index diffractions of Y2O3 became weak gradually whereas the (400) diffraction was strengthened. The color of the Y2O3 HIPB changed from brown to gray. The bonding strength decreased by 61% with increasing hydrogen treatment time, and finally remained unchanged. Meanwhile, the electrical resistivity of the Y2O3 HIPB decreased from 8.2 × 109 Ω cm by over two orders of magnitude and then tended to be constant. The oxygen loss as well as hydrogen incorporation was proposed to be responsible for these modifications and indications of the present work for preparation of HIPB with high reliability were discussed.

Clarification of Tritium Behavior in Pb–Li Blanket System

In order to clarify the tritium behavior in Pb–Li blanket system, the solubility of hydrogen isotopes in the Pb–Li eutectic alloy was experimentally investigated. The effects of (i) Li preferential evaporation from Pb–Li, (ii) thermal convection in a quartz-glass reaction tube and (iii) difference in crucible materials between Al2O3 and W on the solubilities were discussed. Another important issue of the Pb–Li blanket system is to develop a new ceramic coating to decrease tritium permeation rate. Tritium permeation test was performed for Er2O3 coating on F82H. The permeation reduction factor achieved here was higher than 103. Precise experiments were carried out to determine the solubility, diffusivity and permeability of hydrogen isotopes in Pb–Li eutectic alloy by means of a transient permeation method. The isotope effects in solubility and diffusivity between H and D were clarified. No isotope effect in solubility was observed between H and D, and the H diffusivity was 1.4 times larger than the D one. The ratio was near to a value predicted from the classical theory. Experiment using tritium is designed under the collaboration work with INL.

Effect of water vapor on tritium permeation behavior in the blanket system

It is found that most hydrogen supplied to the purge gas changed to water vapor due to the water formation reaction in the early stage of the blanket operation and that physical or chemical adsorbed water is released in the high concentration into the blanket purge gas when the blanket temperature becomes higher than several hundreds of degrees K if the pre-treatment is not applied to the solid breeder materials. Effect of coexistence of water vapor in the purge gas on permeation behavior of hydrogen through F82H ferritic steel in the breeding part and palladium–silver (Pd–Ag) in the recovery part is discussed because use of them is generally considered for recovery of bred tritium from the solid blanket. Almost no decrease in permeation rate of F82H is observed in this study when water vapor exists in the blanket purge gas. The permeability of hydrogen isotopes through the Pd–Ag pipe gradually decreases when water vapor exists in the blanket purge gas. Properties required in estimation of the hydrogen permeated to the purge gas are experimentally obtained in this study.

Material Improvement of Hydrogen Isotope Permeation Monitor for Liquid Lithium

Titanium plates coated by iron were fabricated electrochemically as a candidate hydrogen isotope permeation window for liquid lithium. Contacting the window to liquid lithium containing deuterium between 673 and 873 K, its permeation behavior and resistance to degradation were investigated. The iron-coated window showed less permeability than the bare titanium window as well as good agreement with the theoretical value. Furthermore, the iron layer at the vacuum side surface strongly improved oxidation resistance. Decrease of permeability for 2 hours air exposure could be recovered within 30 hours in the case of the coated window, while that of the bare titanium window could not. The coated permeation window is promising regarding high permeability and antidegradation properties.