Recovery Of Hydrogen Isotopes Research Articles

Low temperature hydrogen superpermeation in vanadium composite metal foil pumps

Palladium-based foil membranes are an effective option for hydrogen isotope recovery from the plasma exhaust of future fusion plants, but cost and availability are concerns. Vanadium (V) is a relatively low cost, neutron tolerant material with high hydrogen permeability. It has been well-studied as a superpermeable membrane at high temperature (>500 °C), but V displays negligible superpermeation at low temperature (75–200 °C) due to catalytic limitations. Composite membranes were fabricated by depositing thin layers (∼100 nm) of either Pd or BCC PdCu on sputter-cleaned vanadium foils (100 μm). Symmetric membranes elevated superpermeation to levels approaching bulk Pd or PdCu foils, with ∼5X higher flux in the latter reflecting the superior properties of PdCu. Asymmetric membranes revealed that the Pd-based catalyst layer was critical for both efficient absorption of superthermal hydrogen upstream as well as catalyzing re-combinative desorption downstream. At T ≥ 150 °C composite membrane superpermeation was equivalent to the Pd-based foils, but the flux was attenuated by a factor of 2-3X as the temperature was reduced. This deviation from pure foil performance coincided with the formation of vanadium hydride (β-V2H), which also impacted the transient response. Nevertheless, no embrittlement was observed under the conditions examined and elevating the temperature >150 °C removed the hydride and restored full performance. The achievement of palladium-level performance with a >99% reduction in Pd inventory makes these V composite metal foils pumps an attractive option for low temperature hydrogen isotope recovery in future fusion plants.

Experimental and Numerical Analysis of a Pd-Ag Membrane Unit for Hydrogen Isotope Recovery in a Solid Blanket.

The interest of the fusion community in Pd-Ag membranes has grown in the last decades due to the high value of hydrogen permeability and the possibility of continuous operation, making it a promising technology when a gaseous stream of hydrogen isotopes must be recovered and separated from other impurities. This is the case of the Tritium Conditioning System (TCS) of the European fusion power plant demonstrator, called DEMO. This paper presents an experimental and numerical activity aimed at (i) assessing the Pd-Ag permeator performance under TCS-relevant conditions, (ii) validating a numerical tool for scale-up purposes, and (iii) carrying out a preliminary design of a TCS based on Pd-Ag membranes. Experiments were performed by feeding the membrane with a He-H2 gas mixture in a specific feed flow rate ranging from 85.4 to 427.2 mol h-1 m-2. A satisfactory agreement between experiments and simulations was obtained over a wide range of compositions, showing a root mean squared relative error of 2.3%. The experiments also recognized the Pd-Ag permeator as a promising technology for the DEMO TCS under the identified conditions. The scale-up procedure ended with a preliminary sizing of the system, relying on multi-tube permeators with an overall number ranging between 150 and 80 membranes in lengths of 500 and 1000 mm each.

Study on CH4 Oxidation and H2O Adsorption for Hydrogen Isotope Recovery

This study deals with the processes of converting trace CH4 in the oxidation reaction and adsorbing H2O. The conversion of CH4 was confirmed at various reaction temperatures and flow rates by injecting O2 above the equivalence ratio of CH4 in Ar. The conversion was higher at a higher reaction temperature and a lower flow rate. Also, the impurity effects of CO2, CO, and H2O coexisting in the feed gas with CH4 were investigated. When CO2 and H2O were included in the feed gas, CH4 conversion was decreased, and CO contained in the feed gas increased CH4 conversion by the heat of oxidation reaction. When CH4 is converted to CO2 and H2O through oxidation and H2O is adsorbed on the adsorbent, complete recovery of hydrogen isotopes can be obtained. Molecular sieve was used as the adsorbent, and the water adsorption capacity of the adsorbent was confirmed by generating water through the generator. Finally, it was confirmed that converted H2O from CH4 was adsorbed on the absorbent.

Adsorption of hydrogen and deuterium on A-type zeolites at 77 K after various heat treatments

Abstract Molecular sieves (MSs) are a potentially useful means of hydrogen isotope recovery as well as the temporary storage and supply of such isotopes. In this study, the hydrogen adsorption isotherms for various MS samples were acquired after applying different water removal processes to activate the MSs. MS-3A sample was found not to adsorb hydrogen regardless of the activation conditions. MS-4A sample adsorbed hydrogen at 77 K after heating at 473, 513, and 673 K. However, the adsorption amount after heating at 473, 513 K was considerably less than that at 673 K. Consequently, heating at 673 K was required to activate this type of MS. In the case of an MS-5A sample, the presence of residual water had little effect on hydrogen isotope adsorption at 77 K. From these results, it is evident that MS-5A is the most suitable hydrogen adsorption material because it is readily activated and is less affected by water adsorption.

Effects of structural and concentration polarization on the efficiency of Pd membrane permeator

For the processes of extracting hydrogen from the mixed gas of fusion reactors, it is of benefit to find an efficient method for hydrogen isotopes recovery and cyclic utilization. To enhance the hydrogen extraction efficiency, the properties of hydrogen permeation under various operating conditions in the tubular Pd membrane reactor system have been first investigated using the computational fluid dynamics (CFD) and material diffusion model. The results show that the predominated factor for the hydrogen extraction efficiency of tubular Pd membrane reactor is the fluid field of permeation pipe, further the effects of flux velocity, membrane length and thickness on the extraction efficiency at different pressures, as well as the concentration polarization effect at different conditions have been evaluated. The results could be significant for improving the engineering design of a highly efficient extraction Pd reactor by greater aspect ratio reactor. In addition, this method can also be used to simulate isotope separation process in Pd membrane reactor.

Adsorption kinetics on the recovery of hydrogen isotopes from helium using palladium particle bed

The recovery and separation of hydrogen isotopes from helium purge gas is one of the critical steps in nuclear fusion based fuel cycle. In the present study, the adsorption kinetics of hydrogen and deuterium from helium using palladium particle bed is generated at different temperatures varying from 30 °C to 150 °C in a recirculating packed bed batch adsorption system. The system is modeled as a combination of packed bed adsorber and a mixing vessel connected in closed loop. The overall mass transfer coefficient is estimated at different temperatures by minimizing the error between the simulated results and the experimental data. The apparent activation energy is estimated for both the hydrogen isotopes using Arrhenius plot. Based on the estimated values of apparent activation energies, it is concluded that the overall adsorption rate is limited by internal diffusion for both hydrogen and deuterium.

Experiment to Recover Tritium from Li-Pb Blanket and Understanding Chemistry of the Li17Pb83–H System

Various properties of Li-Pb eutectic alloys have been reported aiming at adopting the tritium breeder for the next-step fusion reactor, DEMO. Relations among several physical or chemical properties are reinvestigated here based on not only macroscopic views of the H isotope solubility in Li-Pb and the chemical activity of Li and Pb atoms in the alloy but also a microscopic view on the state of being of H and Li atoms in alloy based on the 1st principle molecular dynamic (MD) numerical calculation. The Sieverts’ constant of H dissolved in Li-Pb is closely related with the chemical activity of Li in Li-Pb. It is found that H dissolved in Li-Pb eutectic alloy has an ionic Li+-H− bond with a single Li atom independent of other Li or Pb atoms and the Li+-H− ionic bond is isolated from another Li atom surrounded by Pb ones. The isotope effect for the Sieverts’ constant is also understood in terms of the state of being of the Li+-H− bond in the alloy. The amounts of inert gases dissolved in the Li-Pb eutectic alloy are evaluated, and it is found that their solubilities are in proportion to the square of the molecular diameter which is estimated from exclusive volume of dissolved gas and consequently with the open space volume among Li-Pb atoms. Two experimental results of hydrogen isotopes recovery are introduced using a permeation window and a Li-Pb and inert gas direct contact method, and mass-transfer coefficients to correlate the overall hydrogen transfer process are determined as a function of diffusivity and flow velocity.

Experiment on Recovery of Hydrogen Isotopes from Li17Pb83 Blanket by Liquid-Gas Contact

Recovery of hydrogen dissolved in Li-Pb eutectic alloy by mean of a bubbling tower is experimentally investigated. Mass-transfer coefficients to predict tritium recovery rate are experimentally determined when Ar and Ar+H2 gas bubbles are injected into Li-Pb through an I-shaped nozzle under the conditions of temperature 573–773 K and H2 partial pressure of 1 Pa–0.1 MPa. The results are fitted by an analytical equation based on diffusion and solution in Li-Pb. So that, the rate-determining step is hydrogen diffusion through a boundary layer formed in Li-Pb-gas interface and absorption and desorption are found to be almost reversible.

Study on Transfer Behavior of Hydrogen Isotopes from Fluidized Li to Y for Li Blanket

In order to make proof of the recovery of hydrogen isotopes from a liquid lithium (Li) blanket, we experimented the recovery of deuterium (D) dissolved in Li by means of yttrium (Y) metal at 300°C. In the experiment, 160 wppm D dissolved in Li was removed down to 1 wppm by means of the Y trap maintained at 300°C under fluidized Li conditions. The ratio of the final-state D concentration dissolved in Li to the initial one is defined as a removal efficiency, and the removal efficiency was found to be in proportion to the D concentration remained in Li. In addition, judging from its dependence on D concentration remained in Li, it was found that the removal efficiency is well consistent with the secondary-order reaction process and the removal efficiency was correlated to a function of contact time.

Poisoning effect of oxygen on hydrogenation performance of a Zr-V-Ni Laves phase alloy

Zr-based Laves phase alloys have been considered as suitable getter materials for hydrogen isotopes recovery, storage and delivery and received considerable attention during past decades. This work focuses on hydrogenation performance of a pseudo-binary Zr-V-Ni Laves phase alloy with the composition of Zr(V0.95Ni0.05)2 after pre-exposure in different contents of O2. It is found that introduced pure oxygen can be rapidly absorbed by the fully activated Zr(V0.95Ni0.05)2 alloy within 40 s. All of the experimental samples pre-exposed in oxygen consist dominant C15 type ZrV2 Laves phase and minor Zr3V3O oxides. With the further increase the oxygen pressure to 4.0 kPa in specimen chamber, Bragg peaks of Zr2V, V-rich BCC solid solution phase and ZrO2 phase, including baddeleyite (α-ZrO2) with monoclinic structure and a small amount of tazheranite (γ-ZrO2) with cubic structure are observed in addition to the dominant ZrV2 and minor Zr3V3O phases. Meanwhile, it can be seen that the lattice parameter of cubic C15 type ZrV2 calculated from Rietveld refinement increases from 7.402 to 7.432 Å with the increase of O2 content and the corresponding unit cell volume increases 0.86 vol.% as the O2 pressure from 1.0 to 4.0 kPa, which indicates more oxygen atoms have been dissolved into the lattice of ZrV2. All of the oxygen poisoned Zr(V0.95Ni0.05)2 alloys can absorb hydrogen and the capacity decreases from 3.39 to 2.22 H A−1 with the increase of oxygen pressure from 1.0 to 4.0 kPa, comparing with the maximum hydrogen storage capacity (4.34 H A−1) of the fully activated fresh alloy. The existence of oxygen is found to decrease both capacity and kinetics of Zr(V0.95Ni0.05)2 by forming passivation layer oxides which block the dissociation of H2 molecule on the surface.

Pd-Ag-Cu dense metallic membrane for hydrogen isotope purification and recovery at low pressures

Purification and recovery of hydrogen isotopes using palladium based dense metallic membranes is of utmost importance in fusion fuel clean-up systems. Permeation behavior of hydrogen isotopes in the dense metallic membrane is the deciding factor for their applicability. Here, we report the hydrogen and deuterium permeation behavior of 100 µm thick Pd0.77Ag0.23 and Pd0.77Ag0.10Cu0.13 alloy membranes using a closed recirculatory feed gas loop at low transmembrane pressures of 50, 100 and 150 kPa in the temperature range 523–673 K. These membranes were found to have infinite hydrogen selectivity. This study revealed the higher permeability of hydrogen and deuterium in Pd0.77Ag0.10Cu0.13 than Pd0.77Ag0.23 at all experimental temperatures and transmembrane pressures. Further, the deuterium permeability was found to be lower than that of hydrogen in both the membranes. Diffusion of hydrogen/deuterium in the bulk of the membrane was found to be the rate liming step. We also report here the pertinence of Pd0.77Ag0.10Cu0.13 membrane in purification of 3He contaminated with tritium to obtain high purity 3He for use in neutron detector.

핵융합 배가스 중 수소 회수를 위한 촉매반응 특성 연구

In D-T fusion reaction, <TEX>$D_2$</TEX> (duterium) and <TEX>$T_2$</TEX>(tritium) are used as fuel gas. The exhaust gas of nuclear fusion includes hydrogen isotopes <TEX>$Q_2$</TEX> (Q means H, D or T), tritiated components (<TEX>$CQ_4$</TEX> and <TEX>$Q_2O$</TEX>), CO, <TEX>$CO_2$</TEX>, etc. All of hydrogen isotopes should be recovered before released to the atmosphere. This study focused on the recovery of hydrogen isotopes from <TEX>$CQ_4$</TEX> and <TEX>$Q_2O$</TEX>. Two kinds of experiments were conducted to investigate the catalytic reaction characteristics of SMR (Steam Methane Reforming) and WGS (Water Gas Shift) reactions using Pt catalyst. First test was performed to convert <TEX>$CH_4$</TEX> into <TEX>$H_2$</TEX> using 6% <TEX>$CH_4$</TEX>, 6% CO/Ar feed gas. In the other test, 100% CO gas was used to convert <TEX>$H_2O$</TEX> into <TEX>$H_2$</TEX> at various reaction conditions (reaction temperature, S/C ratio, GHSV). As a result of the first test, <TEX>$CH_4$</TEX> and CO conversion were 41.6%, 57.8% respectively at <TEX>$600^{\circ}C$</TEX>, S/C ratio 3, GHSV <TEX>$2000hr^{-1}$</TEX>. And CO conversion was 72% at <TEX>$400^{\circ}C$</TEX>, S/C ratio 0.95, GHSV <TEX>$333hr^{-1}$</TEX> in the second test.

Fabrication and experimental validation of a full-scale depleted uranium bed with thin double-layered annulus configuration for hydrogen isotopes recovery and delivery

Metal hydride beds play an important role in the application of hydrogen-related energy. In the present work, a full-scale DU (depleted uranium) bed with the newly proposed bed design of thin double-layered annulus configuration was fabricated for hydrogen isotopes recovery and delivery. The hydrogen recovery/delivery properties and the thermal effect of the fabricated bed were experimentally investigated. It was found that the fabricated bed was able to achieve the hydrogen storage target of 17.5 mol H2 with a fast hydrogen recovery rate. Not only hydrogen delivery amount as high as 16.5 mol (∼94% of recovery amount) but also an average delivery rate of 20 Pa m3/s could be obtained at 450 °C, even though the hydrogen delivery time of the bed reached as long as 30.9 min. The fabricated DU bed also exhibited outstanding cyclic hydrogen recovery/delivery performances. Deterioration in both hydrogen recovery/delivery amount and rate was not observed even up to 10 cycles. Besides, it was shown that utilization of the water cooling loops drilled in the DU bed was beneficial to enhance the heat transfer and promote the hydrogen recovery process of the bed. Meanwhile, the internal structure of the fabricated bed was observed by ICT (industrial computed tomography). And the ICT results demonstrated that DU expanded seriously after hydrogen recovery/delivery cycles, resulting in the deformation of the filters in the bed. The experimental results suggested that the fabricated DU bed was technically feasible to be applied for hydrogen isotopes recovery and delivery in the International Thermonuclear Experimental Reactor.

Comparative study of full-scale thin double-layered annulus beds loaded with ZrCo, Zr0.8Hf0.2Co and Zr0.8Ti0.2Co for recovery and delivery of hydrogen isotopes

Metal hydride bed is a necessary component for deuterium–tritium fusion energy under development in International Thermonuclear Experimental Reactor (ITER), which is used for rapid and safe recovery/delivery of hydrogen isotopes. In the present work, full-scale thin double-layered annulus beds loaded with ZrCo, Zr0.8Hf0.2Co and Zr0.8Ti0.2Co were fabricated. The corresponding hydrogen storage behaviors including hydrogen recovery/delivery and cycling properties of the three beds were systematically investigated and compared. It was found that all the three fabricated beds could reach the hydrogen storage target of 17.5 mol. Compared with ZrCo bed and Zr0.8Hf0.2Co bed, Zr0.8Ti0.2Co bed exhibited superior hydrogen delivery properties in terms of higher hydrogen delivery amount, faster delivery rate and better cyclic delivery performance, which could deliver 17.06 mol H2 (∼94.7% of total capacity) at 450 °C within 31.8 min holding at the critical delivery rate of 20 Pa m3/s. Although the hydrogen delivery amount gradually decreased during the recovery/delivery cycles, which was revealed to be caused by the characteristic disproportionation of ZrCo based alloy, significant improvement had been gained for Zr0.8Ti0.2Co bed relative to ZrCo bed and Zr0.8Hf0.2Co bed. In addition, the industrial computed tomography (ICT) results showed that the thin double-layered annulus bed owned good structural stability during the hydrogen recovery/delivery cycles. In view of its beneficial hydrogen recovery and delivery performances, the Zr0.8Ti0.2Co bed with thin double-layered annulus configuration appeared to be a potential option for hydrogen isotopes recovery and delivery in ITER if the anti-disproportionation property could be further enhanced.

Application of Computational Fluid Dynamics for the Simulation of Cryogenic Molecular Sieve Bed Adsorber of Hydrogen Isotopes Recovery System for Indian LLCB-TBM

One of the most challenging tasks in the design of the fuel cycle system lies in the effective design of Tritium Extraction System (TES) which involves proper extraction and purification of tritium in the fuel cycle of the fusion reactor. Indian Lead Lithium cooled Ceramic Breeder Test Blanket Module (LLCB-TBM) would extract hydrogen isotopes through Cryogenic Molecular Sieve Bed (CMSB) adsorber system. A prototype Hydrogen Isotopes Recovery System (HIRS) is being developed to validate the concepts for tritium extraction by adsorption mass transfer mechanism. In this study, a design model has been developed and analyzed to simulate the adsorption mass transfer kinetics in a fixed bed adsorption column. The simulation leads primarily to effective design of HIRS, which is a state-of-the-art technology. The paper describes the process simulation approach and the results of Computational Fluid Dynamics (CFD) analysis. The effects of different operating conditions are studied to investigate their influence on the hydrogen isotopes adsorption capacity. The results of the present simulation study would be used to understand the best optimized transport phenomenon before realizing the TES as a system for LLCB-TBM.

Chemical Analysis of Hydrogen Isotopes Dissolved in Li and Y for Hot Trap of IFMIF Target Loop

IFMIF-EVEDA progresses in Japan as one of the EU-Japan Broader Approach Activities. The research is performed to decide whether or not IFMIF is constructed after some uncertainties included in the design are clarified. One of the uncertainties included in the Li purification process is to prove experimentally the removal of 1 weight ppm (wppm) T and 10 wppm D from flowing Li for safety.Our research group is experimentally investigating the recovery of hydrogen isotopes including T not only in static Li but also in fluidized Li. In the past study, hydrofluoric acid (HF) treatment of Y is successful in removing oxide inevitably formed on its surfaces. The recovery of hydrogen isotopes including T less than 1 wppm is successfully proved with use of the HF-treated Y at 300°C, which is the IFMIF hot-trap temperature. Mass-transfer rates of hydrogen isotopes in the liquid Li and Y under stirred conditions were determined.In addition, we developed a way to determine an amount of D or T dissolved in Li and Y by using a dissolution method. The quantitative D analysis is performed by using techniques of HNO3 solution for Y and H2O one for Li. The distribution coefficient between Li and Y is determined as a function of temperature and contact time.

Hydriding and dehydriding characteristics of small-scale DU and ZrCo beds

With the development of fusion technology, it will be necessary to store large amounts of tritium during the nuclear fusion fuel cycle. Stable metal tritides are viewed as potential candidates for the high-density storage of tritium. Metal tritide formers offer a safe and convenient method for tritium storage. For the storage, supply, and recovery of hydrogen isotopes, zirconium cobalt (ZrCo) and depleted uranium (DU) have been extensively proposed. Thus, we have designed and fabricated two identical small-scale getter beds for a comparison of ZrCo with DU on the hydriding/dehydriding properties. After the powderization of the metals, the hydriding/dehydriding performance at different stoichiometries of ZrCo and DU was measured. We provide preliminary experimental results of our ZrCo and DU beds.

Hydrogen sorption–desorption studies on ZrCo–hydrogen system

The ZrCo–H2 system was investigated in this study owing to its importance as a suitable candidate material for storage, supply, and recovery of hydrogen isotopes. Desorption hydrogen pressure-composition isotherms were generated at six different temperatures in the range of 524–624 K. A van’t Hoff plot was constructed using the plateau pressure data of each pressure-composition isotherms and the thermodynamic parameters were calculated for the hydrogen desorption reaction of ZrCo hydride. The enthalpy and entropy change for the desorption of hydrogen were found to be 83.7 ± 3.9 kJ mol−1 H2 and 122 ± 4 J mol−1 H2 K−1, respectively. Hydrogen absorption kinetics of ZrCo–H2 system was studied at four different temperatures in the range of 544–603 K and the activation energy for the absorption of hydrogen by ZrCo was found to be 120 ± 5 kJ mol−1 H2 by fitting kinetic data into suitable kinetic model equation.

Adsorption Behavior of Hydrogen and Deuterium on Natural Mordenite Adsorbent at 77 K

Cryogenic adsorption is effective for the recovery of low-concentration hydrogen isotopes in bulk helium gases. In a fusion power plant, application of this process is foreseen for the recovery of tritium from the blanket sweep gas and cleanup of the helium discharge exhaust gas. The authors performed a screening test to find more suitable adsorbents for the recovery of hydrogen isotopes from the bulk helium gas at liquid nitrogen temperature. The screening test indicated that a natural mordenite adsorbent has a quite high adsorption capacity for hydrogen under a helium atmosphere. For the adsorption of deuterium, it was found that the natural mordenite adsorbent possesses a high adsorption capacity even at the lower pressure range of hydrogen and deuterium. The adsorption rates of hydrogen and deuterium were quantified by analyzing breakthrough curves obtained in experiments. Evaluated effective pore diffusivities of hydrogen isotopes in the mordenite adsorbents are considerably higher than those in MS5A adsorbents. Thus, it can be said that the natural mordenite adsorbents are suitable for adsorption of hydrogen isotopes from the viewpoint of adsorption rates, as well. The results suggest that mordenite-type adsorbents are promising for the recovery of low-concentration hydrogen isotopes from the helium bulk gas.

Extraction of hydrogen into vacuum by electrochemical hydrogen pump for hydrogen isotope recovery

For hydrogen isotope recovery, an electrochemical hydrogen pump using CaZr0.9In0.1O3−α under vacuum in the cathode compartment has been proposed. Two types of electrodes—pasted and electroless plated electrodes—were used to evaluate the mass transfer process. When the hydrogen pump was operated using direct current, the voltage between electrodes under vacuum was less than that under atmospheric pressure, regardless of electrode type. This result indicates that the hydrogen pump performance is improved under vacuum. In the case of the pasted electrode, however, the voltage decrease was larger than that in the case of the plated electrode. Electrochemical impedance spectroscopy revealed that the diffusivity in the pasted electrode was smaller under atmospheric pressure than under vacuum. From comparing the microstructures of the two electrode types, the pasted electrode has larger pores and would be more suitable for the hydrogen pump under vacuum.