Mixtures Of Hydrogen Isotopes Research Articles

Experimental study of the electrochemical hydrogen pump based on proton exchange membrane for the application in fusion fuel cycle

An electrochemical hydrogen pump (EHP) can be used in the fuel cycle of fusion devices for purifying (separating) and compressing fuel (a mixture of hydrogen isotopes). One of the distinguishing features of the fuel cycle of fusion devices is a relatively narrow range of operating pressures of the fuel mixture from high vacuum (∼1–10 Pa) to several atmospheres (2–3·105 Pa), and in most of the fuel cycle systems, especially in transmission systems (like gas lines), the pressure shall not exceed atmospheric. In this study, the possibility of using EHP with a proton exchange membrane (PEM) in the fuel cycle of fusion devices in the pressure range of 0.01 – 0.30 MPa and temperatures of 20 – 70 °C was considered, and i-V curves were obtained. A regression analysis of the i-V curves was carried out. The temperature dependence of limiting current and resistance of EHP cell was obtained as follows: lnilim=−1140±1001T+(3.0±0.3) and lnρ=1780±2801T+(6.5±1.1). It is shown that there is no dependence of these parameters on pressure. The EHP cell productive capacity was determined in the studied ranges of pressure and temperature as follows: lni2F=−0.0119×T−4.2×Ecell0.05+Ecell+20.4. The results obtained allow one to predict the performance of the EHP device under conditions of subatmospheric hydrogen pressure at the anode and to select the most effective operating parameters of the EHP.

A squarate-pillared titanium oxide quantum sieve towards practical hydrogen isotope separation

Separating deuterium from hydrogen isotope mixtures is of vital importance to develop nuclear energy industry, as well as other isotope-related advanced technologies. As one of the most promising alternatives to conventional techniques for deuterium purification, kinetic quantum sieving using porous materials has shown a great potential to address this challenging objective. From the knowledge gained in this field; it becomes clear that a quantum sieve encompassing a wide range of practical features in addition to its separation performance is highly demanded to approach the industrial level. Here, the rational design of an ultra-microporous squarate pillared titanium oxide hybrid framework has been achieved, of which we report the comprehensive assessment towards practical deuterium separation. The material not only displays a good performance combining high selectivity and volumetric uptake, reversible adsorption-desorption cycles, and facile regeneration in adsorptive sieving of deuterium, but also features a cost-effective green scalable synthesis using chemical feedstock, and a good stability (thermal, chemical, mechanical and radiolytic) under various working conditions. Our findings provide an overall assessment of the material for hydrogen isotope purification and the results represent a step forward towards next generation practical materials for quantum sieving of important gas isotopes.

Startup methods analysis of a cryogenic distillation system with two interlinked columns for hydrogen isotope separation

Effective startup methods are crucial for the successful operation of a distillation facility. In order to design a viable startup method for a cryogenic distillation demonstration system with two interlinked columns for hydrogen isotope separation, which is under construction at Institute of Materials, China Academy of Engineering Physics, Aspen Plus and Aspen Dynamics were employed in combination to generate a dynamic numerical model for the startup analysis. Total four conventional startup methods were analysed. The most time-effective method was identified and the other of the four startup methods were found to be able to lead to successful startup results but with varied operation complexity and length of time to reach the steady state. The effective startup method that involved in charging the two distillation columns with equilibrated hydrogen isotope mixtures respectively, took only 50.36 h to reach the target steady state. And the identified method would be employed into the cryogenic distillation demonstration system to check its startup efficient.

Enhance Hydrogen Isotopes Separation by Alkali Earth Metal Dopant in Metal-Organic Framework.

Kinetic quantum sieving (KQS) based on pore size and chemical affinity quantum sieving (CAQS) based on adsorption site are two routes of porous materials to separate hydrogen isotope mixtures. Alkali earth metals (Be, Mg, and Ca) were doped into UiO-67 to explore whether these metal sites can promote H2/D2 separation. Based on the zero-point energy and adsorption enthalpy calculated by density functional theory calculations, the Be dopant shows better H2/D2 separation performance than other alkali earth metal dopants and unsaturated metal sites in metal-organic frameworks based on CAQS. Orbital interaction strongly relates to the chemical affinity and further influences the D2/H2 selectivity. Moreover, the predicted D2/H2 selectivity of Be-doped sites (49.4) at 77 K is even larger than the best experimental result (26). Finally, the different dynamic behaviors of H2 and D2 on Be-doped UiO-67 indicate its strong H2/D2 separation performance via KQS.

Parameters of the UNIQUAC model for describing the vapor-liquid phase equilibrium of D<sub>2</sub>-T<sub>2</sub>, D<sub>2</sub>-DT, DT-T<sub>2</sub> hydrogen isotope mixtures

Objectives. Determination of the parameters of the binary energy interaction of the (UNIversal QUAsiChemical) UNIQUAC model on the basis of mathematical processing of experimental literature data on the phase equilibrium of hydrogen isotopic mixtures D2-T2, D2-DT, DT-T2 to calculate the activity coefficients of the components D2, DT, and T2.Methods. The method of successive approximations was used in junction with the “from stage to stage” method, which consists in calculating a single evaporation process on a theoretical plate.Results. Equations were written for calculating the activity coefficients of hydrogen isotopes on the basis of the Sherwood theory as applied to binary D2-T2, D2-DT, DT-T2 and ternary D2-DT-T2 hydrogen isotope mixtures. The graphical dependences of the activity coefficients and separation coefficients of mixtures D2-T2, D2-DT, and DT-T2 are compared in the range of the concentration of a highly volatile component from 0 to 100 mol % at atmospheric pressure for three options: ideal mixtures; non-ideal mixtures using the Sherwood theory; non-ideal mixtures on the basis of the UNIQUAC model. The dependences of the separation coefficients a were found to be similar for all binary isotopic mixtures. However, when considering mixtures as ideal, a increases.According to Sherwood's theory, a remains a practically constant value, which is independent of the composition of the mixture. The UNIQUAC model predicts a decrease in a with an increase in the concentration of a less volatile component in the mixture. The profile of the distribution of hydrogen isotopes D2, DT, and T2 of a three-component mixture D2-DT-T2, along the height of a distillation column operating in a closed mode was calculated for three variants. It was accepted that: pressure along the height of the column is constant and equal to atmospheric 760 mm Hg. Art.; number of theoretical plates 21; concentration of components in the liquid phase on the first plate (stage), in mol %: XD₂ = 65; XDT= 10; XT₂= 25; the accuracy of calculating the composition of the vapor phase is 10-10.Conclusions. The parameters of the binary energy interaction of the UNIQUAC model of hydrogen isotopic mixtures D2-T2, D2-DT, and DT-T2 are determined. The UNIQUAC model is adequate in relation to experimental data on the coefficient of separation. Due to systematic deviations in the theoretical Sherwood and ideal models, they are not suitable for further calculations of phase equilibrium of isotopic mixtures of hydrogen D2-T2, D2-DT, DT-T2, and D2-DT-T2.

Kinetic and Chemical Affinity Quantum Sieving Effects of ZIF-67 for H2 and D2 and Gas Chromatographic Separation of Hydrogen Isotopes on Columns Packed with ZIF-67@NH2-γ-Al2O3

Hydrogen isotopes have extremely important roles in many fields, but they have almost the same chemical and similar physical properties, which makes the separation process very difficult. In this work, ZIF-67 was selected for the separation of hydrogen isotopes. The theoretical calculation results showed that the adsorption selectivity of ZIF-67 for hydrogen isotope mixtures (D2/H2 = 1:1) increased from 1.66 to 2.08 with the temperature decreasing from 77 to 20 K, indicating that ZIF-67 has a chemical affinity quantum sieving (CAQS) effect. Meanwhile, the diffusion coefficients of H2 and D2 were also different; the kinetic selectivity of D2/H2 was 4.41 at 70 K, indicating that ZIF-67 has a kinetic quantum sieving (KQS) effect at low temperatures. When the temperature was higher than 72 K, the diffusion coefficient of H2 was higher than that of D2; ZIF-67 showed a typical kinetic sieving effect and the kinetic selectivity of H2/D2 was 1.29 at 77 K. Based on the fact that due to the CAQS effect, the adsorption capacity of D2 in ZIF-67 was higher at 77 K and the diffusion coefficient of D2 was lower at the same time, it is expected that ZIF-67 can effectively realize the separation of hydrogen isotopes. In contrast, ZIF-8, isostructural to ZIF-67, has no difference on H2 and D2 in view of adsorption capacity and adsorption heat and, consequently, has no effect on separation, indicating the importance of the incompletely filled d-orbitals (Co2+ versus Zn2+). To verify the separation performance of ZIF-67, the composites ZIF-67@NH2-γ-Al2O3 were synthesized by the layer-by-layer (LBL) method and used as a gas chromatographic stationary phase packed in a 1 m column (1.0 m × 2.0 mm I.D.) for separation of hydrogen isotopes H2 and D2. Under optimal chromatographic separation conditions, the resolution (R) reached 1.79 and the separation time was 5.55 min with the optimal composite ZIF-67@NH2-γ-Al2O3 at 77 K.

An Analytical Solution to the Problem of Hydrogen Isotope Passage through Composite Membranes Made from 2D Materials

An analytical solution to the problem of wave transport of matter through composite hyper-fine barriers is constructed. It is shown that, for a composite membrane consisting of two identical ultra-thin layers, there are always distances between the layers at which the resonant passage of one of the components is realized. Resonance makes it possible to separate de Broiler waves of particles with the same properties, which differ only in masses. Broad bands of hyper-selective separation of a hydrogen isotope mixture are found at the temperature of 40 K.

Ballistic model of recycling of atomic and molecular hydrogen and its application to the ITER main chamber

A simple, computationally efficient 1D model is suggested for the recycling of atomic and molecular hydrogen between the main chamber first wall (FW) of a tokamak and the peripheral plasma. The model is based on iteratively solving the kinetic equation for the 1D velocity distribution function (VDF) of hydrogen neutral atoms in the projection of velocity on the direction normal to the FW. The model results in a fast-converging routine due to the domination of the contribution to the VDF from long-distance, ballistic flights of the neutral atoms produced by the charge exchange of colder atoms with hotter plasma ions. The proposed modification of the ballistic model (BM) enhances its original version along the following lines: the account of the inelastic reflections of the neutral atoms from the wall; parameterisation of the boundary condition for the VDF of the atoms produced by the reflection of ions from the wall with immediate recombination, without capture in the wall and thermalisation there; extension to a mixture of hydrogen isotopes; elaboration of algorithms for speeding up computation on graphical processing units. The complete set of equations of the BM is published for the first time. The model is verified by comparison with the EIRENE code simulations of the VDF of neutral atoms and molecules in the scrape-off-layer around mid-plane for typical conditions of ITER operation. The applicability of the BM to the synthetic diagnostics developed for the H-alpha high-resolution spectroscopy is demonstrated. That is, the simple 1D model reproduces reasonably well the 1D projection of the data computed with the 3D Monte-Carlo code on a 2D plasma background.

Overview about cryogenic distillation control and safety approach for Isotopes Separation Facility (ISF)

Abstract Isotopes separation technologies are used in both Tritium Removal Facilities associated with CANDU reactors (to remove tritium from heavy water) and fusion applications (eq. ITER Isotope Separation System) to recover and enrich tritium for further operation. The expertise gained during design, manufacturing, building, commissioning and operation of the Cryogenic Distillation System (CDS) with proprietary four column design built at ICSI Rm. Valcea, could be applied for various tritium recovery applications, regardless of the type of front-end process used, Liquid Phase Catalytic Exchange or Combined Electrolysis and Catalytic Exchange. Cryogenic Distillation feed is a mixture of hydrogen isotopes which presents hazards in operation (explosion and tritium contamination), therefore the CDS of PESTD was designed to meet industrial and nuclear applicable standards. In this paper we present an overview of the CDS focusing on the process control and safety approach which meet specific conditions of Romanian codes and standards required for operation. However, specific information may be used later as reference for design consideration for other CDS. The cryogenic distillation process from ICSI Rm. Valcea is designed as four columns cascade inside a cold-box which acts as second barrier against hydrogen release and thermal insulation. The CDS process control is based on a Programmable Automation Controller (PACs), a Supervisory Control and Data Acquisition (SCADA) and specific low temperature field equipment and devices. The control room operator supervises the process using a specific designed Human Machine Interface (HMI) which permits to monitor process parameters, alarms acknowledgment and acts to adjust the process or override normal PACs control.

Use of breakthrough experiment to evaluate the performance of hydrogen isotope separation for metal-organic frameworks M-MOF-74 (M=Co, Ni, Mg, Zn)

The unique adsorption performance of metal-organic frameworks (MOFs) indicates a new direction for gas separation and purification. The low-temperature distillation, as a traditional technique for hydrogen isotope separation, is limited as it is a high energy- and cost-intensive process. Instead of utilizing such a conventional separation route, we use ordered microporous frameworks based on a physical adsorption mechanism to solve the challenge of hydrogen isotope separation. Herein we analyze M-MOF-74 (M=Co, Ni, Mg, Zn), featuring a hexagonal channel about 11 A and high density of open metal sites, for their ability to separate and purify deuterium from the hydrogen isotope mixture by dynamic column breakthrough experiments. Our results show that the combination of the strength of binding sites, density of coordinatively unsaturated metal sites and hydrogen isotope adsorption capacity of materials renders Co-MOF-74 as an optimal adsorbent for the capture of deuterium from hydrogen isotope mixtures in a simulated industrial process.

Exploiting Dynamic Opening of Apertures in a Partially Fluorinated MOF for Enhancing H2 Desorption Temperature and Isotope Separation.

Deuterium has been recognized as an irreplaceable element in industrial and scientific research. However, hydrogen isotope separation still remains a huge challenge due to the identical physicochemical properties of the isotopes. In this paper, a partially fluorinated metal–organic framework (MOF) with copper, a so-called FMOFCu, was investigated to determine the separation efficiency and capacity of the framework for deuterium extraction from a hydrogen isotope mixture. The unique structure of this porous material consists of a trimodal pore system with large tubular cavities connected through a smaller cavity with bottleneck apertures with a size of 3.6 Å plus a third hidden cavity connected by an even smaller aperture of 2.5 Å. Depending on the temperature, these two apertures show a gate-opening effect and the cavities get successively accessible for hydrogen with increasing temperature. Thermal desorption spectroscopy (TDS) measurements indicate that the locally flexible MOF can separate D2 from anisotope mixture efficiently, with a selectivity of 14 at 25 K and 4 at 77 K.

A Liquid-Tritium Target for Studying ptμ-Fusion Reactions

A cryogenic liquid-tritium target was developed by RFNC−VNIIEF for studying ptμ fusion. In 2016, it was regularly used for more than 270 h on the muon channel of the JINR Phasotron, thus confirming the compliance with the specified requirements and the correctness of the proposed engineering solutions. At a maximum operating pressure of 4 MPa, an irradiated ampoule volume as large as 80 cm3, and three lines of protection, the target was able to liquefy up to 40 L of a hydrogen-isotope mixture and maintain a temperature in the range of 20−22 K with an accuracy of ±0.05 K or better. Based on the results of the ptμ‑fusion experiments, the reaction channel with the emission of electron−positron pairs was detected for the first time and evidence for the existence of a new reaction channel with the emission of a pair of γ-ray photons was obtained.

Plasma composition control by mixture pellets at ASDEX Upgrade

Experiments were performed that aimed to control the plasma isotopic mixture by delivering supplemental components into the plasma via pellet injection. Pellets, mm-sized solid bodies of frozen fuel, are either formed from a mixture of different hydrogen isotopes or from deuterium (D) with added elements. Mixed HD pellets were produced reliably and reproducibly providing the required 1:1 ratio of the protium (H) and D, mimicking the situation in a future fusion reactor with D and tritium (T). By applying pellet fuelling, control of the plasma isotope composition was established while gaining access to the reactor-relevant high-density regime. However, the approach was mainly to demonstrate the controlling capability. Yet, experiments provided information on the impact of the isotopic composition on the plasma performance. There is a strong indication that adding H to a D reference plasma causes a reduction of both the particle and energy confinement. The deleterious impact of H on the particle confinement is, apparently, even stronger than on the energy confinement. Furthermore, small amounts of H can cause a loss of energy confinement that is stronger than anticipated by the H98(y,2) scaling, which is usually employed in reactor design studies. In the course of this experiment, pellets were demonstrated to be an effective and powerful tool for detailed investigations of the isotope effect. A first test demonstrated that producing and launching pellets that contain a mixture of different elements is a feasible technique. The latter was achieved by doping a D host pellet despite technical reasons limiting the permissible amount of processed N.

Electronic model «FC-FNS» of the fusion neutron source DEMO-FNS fuel cycle and modeling hydrogen isotopes flows and inventories in fueling systems

The conceptual design of the fuel cycle systems of a hybrid fusion neutron source DEMO-FNS is conducted in this paper. Fusion neutron source is promising for research, testing of structural materials of future fusion and fusion-fission hybrid reactors, utilization of nuclear waste, fuel breeding and control of subcritical nuclear systems. The facility operation requires the continuous injection of the fuel mixture of hydrogen isotopes (deuterium and tritium) into the vacuum chamber, as well as its subsequent pumping and processing. The key task of the fuel cycle (FC) design is to create a closed system providing the conditions for fusion burning in plasma, with reduce tritium inventory in the system elements. For this purpose “FC-FNS” electronic model has been actively developing as a tool for estimating fluxes of DT fuel and T inventories in systems where tritium is used. The paper describe the conceptual fuel cycle design for the DEMO-FNS facility and results of the modeling of hydrogen isotopes flows and inventories in fuel systems for steady-state operation mode. The paper compares various conceptual approaches to neutral beam injection system gas supply and chooses the optimal variant for its integration into the DEMO-FNS FC.

“Isotope effect” of hydrogen and deuterium interaction with vanadium alloys VCrTi

V-Ti-Cr vanadium alloys have many perspective applications, particularly, they are considered as a main structural material of the first wall and blanket of fusion reactor with lithium coolant. Also, they are used as a high-temperature membrane for hydrogen isotopes separation and effective sorbents for hydrogen purification installations by PSA (Pressure Swing Adsorption) adsorption method (under the control of sorbent surface composition). The use of vanadium alloys can be extremely interesting because of the possibility of hydrogen isotopes separation in hydrogen systems. The fact is that vanadium has unique properties with respect to hydrogen: protium atoms typically occupy octahedral interstices in vanadium bcc lattice, while the deuterium atoms - mainly tetrahedral interstices. That all considerably affects diffusion and solubility of hydrogen isotopes in vanadium. This paper presents the results of experiments on sorption of hydrogen isotopes with V4Cr4Ti vanadium alloy from a mixture of hydrogen isotopes. According to the obtained time dependence of hydrogen isotopes partial pressure change in gas mixture the following parameters were determined: rate of dissolution and heat of dissolution of hydrogen and deuterium in vanadium alloys V4Cr4Ti, V10Cr5Ti. The conclusion about the prospects of using vanadium alloys in storage systems, separation and purification was made.

Dynamic Nuclear Polarization and Relaxation of H and D Atoms in Solid Mixtures of Hydrogen Isotopes

We report on a study of Dynamic Nuclear Polarization and electron and nuclear spin relaxation of atomic hydrogen and deuterium in solid molecular matrices of H$_{2}$, D$_{2}$, and HD mixtures. The electron and nuclear spin relaxation times ($T_{1e}$ and $T_{1N}$) were measured within the temperature range 0.15-2.5$\,$K in a magnetic field of 4.6 T, conditions which ensure a high polarization of electron spins. We found that $T_{1e}$ is nearly temperature independent in this temperature range, while $T_{1N}$ decreased by 2 orders of magnitude. Such strong temperature dependence is typical for the nuclear Orbach mechanism of relaxation via the electron spins. We found that the nuclear spins of H atoms in solid D$_{2}$ and D$_{2}:$HD can be efficiently polarized by the Overhauser effect. Pumping the forbidden transitions of H atoms also leads to DNP, with the efficiency strongly dependent on the concentration of D atoms. This behaviour indicates the Cross effect mechanism of the DNP and nuclear relaxation, which turns out to be well resolved in the conditions of our experiments. Efficient DNP of H atoms was also observed when pumping the middle D line located in center of the ESR spectrum. This phenomenon can be explained in terms of clusters or pairs of H atoms with strong exchange interaction. These clusters have partially allowed transitions in the center of the ESR spectrum and DNP may be created via the resolved Cross effect.

Early evaluation of hydrogen isotopes separation by V4Cr4Ti-based sorbents at low temperatures

This paper presents the results of experiments on hydrogen isotopes sorption with V4Cr4Ti vanadium alloys from a mixture of hydrogen isotopes. The studies were carried out at temperatures of 353K, 393K, 423K; and pressures of 103–104Pa in gas mixture of hydrogen isotopes. The α-phase domain of V-H (D) system was studied, where the concentration of hydrogen isotopes atoms should not exceed 0.015H (D) atoms per metal atom. The separation parameters were derived for several saturation conditions accordingly to registered time dependences of hydrogen isotopes partial pressure drop.The conclusion was made about the prospects of using vanadium alloys in hydrogen isotopes separation and purification systems.

Comparison of models for multi-component hydrogen isotope mixtures absorbing in or permeating through metals

In the first place, dependences of isotope effects on temperature and compositions are discussed among hydrogen isotopes (H, D and T) absorbing in, diffusing or permeating through metals. Relation between the isotope effects and isotope separation factor is investigated when hydrogen isotope mixtures are absorbed in, diffuse or permeate through metals. Previous experimental results for the absorption of hydrogen isotopes in Pd or Li are correlated as a function of composition and temperature, and they are discussed based on several models proposed previously to explain the relation between the isotope effects and the isotope separation factor. It results in a fact that the ideal solution model with dissociation on metal surfaces can correlate most cases of absorption of hydrogen isotopes in Pd or Li. However, unresolved experimental results still remained that there is a quantitative difference in permeation rates when either H2+D2 or H2+D2+HD mixture is supplied to the high-pressure side of a gaseous phase.

Quantum Sieving for Separation of Hydrogen Isotopes Using MOFs

Hydrogen isotope mixtures can be separated either by confinement in small pores [i.e., “kinetic quantum sieving” (KQS)] or by strong adsorption sites [i.e., “chemical affinity quantum sieving” (CAQS)]. MOFs are excellent candidates for study of these quantum effects, due to their well‐defined, tunable pore structures and the potential to introduce strong adsorption sites directly into the framework structure. In this microreview we summarize the recent status of hydrogen isotope separation using MOFs and future strategies relating to it. Furthermore, a state‐of‐the‐art technique for the direct measurement of selectivity with regard to isotope mixtures is introduced. Experimental results relating to separation factors with different pore apertures in the case of KQS and the role of open metal sites in that of CAQS as a function of temperature and gas pressure are given. Furthermore, technologically relevant parameters such as feasible operating pressure and temperature are discussed with respect to possible applications in a temperature swing process.

Simulation studies of the characteristics of a cryogenic distillation column for hydrogen isotope separation

Cryogenic distillation is a very widely applied technique for separating the components of a mixture of hydrogen isotopes, which may contain up to six isotopic species. This work presents a simple dynamic model for evaluating the major performance characteristics of a cryogenic distillation column for hydrogen isotope separation. Liquid hold up, pressure drop and flooding point have been predicted for the tower using known packing characteristics and fluid properties. The column has been modelled as an equivalent tray tower using a known value of the height equivalent to theoretical plate (HETP) and its dynamic behaviour and separation performance under various conditions have been predicted. The effect of parameters like temperature, reflux ratio, feed point location and feed composition on the final isotopic contents of top and bottom products at steady state has also been studied. Consequences of neglecting the decay heat of tritium in distillation calculations have also been evaluated. This model is intended for preliminary column design work using data from literature, without the need for prior experimental activity.