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We consider the main approaches and designs of using metal hydrides in supply systems of vacuum power plants with hydrogen isotopes as a working medium. By analyzing the results of investigations and developments in this field, we show that the most promising method is connected with the creation of multifunctional metal-hydride elements, which are a part of the structural units of the working zone of a vacuum chamber (e.g., the electrodes of a device supporting plasma) and are made of hydride-forming materials that are reversible absorbers of low-pressure hydrogen. In this case, in addition to the complex solution of auxiliary problems of compact storage, purification, and programmed bleeding-in of hydrogen isotopes into the vacuum chamber of a power plant, efficient pumping-out and improved operation of the plant as a whole can be ensured in certain cases.

The developed and implemented pilot sample of a heat-driven hydrogen compressorfor deep argon purification at the association Lviv Chemical Plant (Lviv, Ukraine) hasbeen described. Initial data for work implementation were the previously obtained RandD resultson the investigations of thermo-sorption hydrogen interaction with metal hydrides, as well as theauthors experience in the field of the development and implementation of metal-hydridecompressing technique. The compressor consists of dual-linked two-stage compressing cascades,including generator-sorbers filled with correspondingly high and low-temperaturehydride-forming materials of intermetallide LaNi5 doped by different quantities ofmanganese. Additionally, the compressor includes a gas-distributing line with locking andmeasuring elements, as well as the air-cooling system and control unit.

The correlation between phase composition hydride forming alloysZr-V-Fe and Zr-V-Fe-B-O, their hydrogen sorption characteristics, and electrotransfercharacteristics, in the gas phase of alloy-hydrogen systems under gas discharge burning in planarmagnetron whose cathode was covered with a powder metal hydride layer, has been established.It has been shown that the balance of gas discharge particles is primarily determined by thepeculiarities of the discharge plasma interaction with metal hydride.

A short review of RandD in the field of hydrogen hydride technologies in Russia and CIS countries is presented. As a result of basic research of physical and chemical features of intermetallic alloys and their hydrides, their structural peculiarities, absorption kinetics, thermal processes, etc., methods have been developed for creation high efficient alloys for different applications in metal hydride technology. Original devices such as hydrogen accumulators, thermal compressors, heat transformation systems and other experimental devices with unique characteristics have been created. The results of reviewed RandD demonstrate high efficiency of metal hydride technologies. These investigations and developments give reliable scientific and technical background for the development of the new research projects in the framework of the new Russian program of RandD in hydrogen energy and technology and for international cooperation.

A mathematical model of heat-and-mass transfer in “metal hydride-hydrogen-gas impurities” systems is presented. This model makes it possible to describe the heat-and-mass transfer taking into account the convective transfer in the metal-hydride modules, for gas mixtures containing impurities that are inactive or low-active to the hydride-forming material.

The authors review information available from Russian and international publications (including their own experimental results) wherein an effect of forming an excited hydrogen species in systems with hydride-forming materials, as well as some evidence of the effect in physical-chemical processes, are considered. Some possibilities of using the effect in vacuum physical-energy units and electrochemical energy conversion systems are shown. A connection of the said effect with a phenomenon of “cold fusion” is noted and illustrated with the “accelerating” model of the phenomenon as the most clear.

The institute for Problems in Machinery of the National Academy of Sciences of the Ukraine has developed an experimental batch of the single-stage metal hydride thermosorption compressors (TSCs) with different gas deliveries: TSC-70, TSC-80, TSC-150 and TSC-300. These have delivery pressure from 7.0 to 30.0 MPa at the initial pressure of 0.3–1.0 MPa. These devices can work in continuous mode or in periodic mode. They are characterized with the original design properties, caused by severe barometric working conditions. The technical parameters of these compressors as well as the results of their long-term operation in the different energy-technological systems are presented in the report. The prospective fields of their application are shown.

Comparative measurements of the H 2 + ion current obtained by the electron impact method (in the range of electron energy from 14 to 17 eV) in hydrogen desorbed from metal hydride samples (Zr-V-Fe)H x and in thermodynamic equilibrium hydrogen at room temperature are carried out. The fine structure of the ionization effectiveness curves (IECs) is investigated. The method of mathematical treatment of the IEC allowing one to obtain the spectrum of the ionization vertical potentals is described. An analysis of the spectra of the vertical ionization potentials for “activated” hydrogen and hydrogen in a state of thermodynamic equilibrium is carried out.

Results are presented on phase equilibria and hydrogen uptake characteristics for alloys in the Zr-V-Fe system. Effects have been determined from combining these alloys with scandium, lanthanum, and aluminum oxide. The hydrogenation uptake kinetics can be improved if the alloy contains Zr3V3O, and the hydrogen capacity is increased if lanthanum or scandium is added. The thermal decomposition conditions for the hydrogenated alloys have been examined.

Simulation of phase transitions in IMC-hydrogen systems on the basis of modified scheme of perturbation theory provides correct description of main characteristics of phase diagrams in the wide region of pressures of hydrogen isotopes (6 order and higher). The obtained data about thermodynamic parameters of α—β transition allows to describe inversion of isotopic effect in LaNi5-H2(D2) system. Data on solubility of hydrogen isotopes in LaNi5 at pressures up to 500 atm are obtainsed; data on parameters of the critical point of α—β equilibriums (experimental data for which are absent) are also obtained. Proposed calculation scheme does not use fitting parameters or empirical correlations and leans upon atomic characteristics of the hydrogen subsystem and metallic matrix which are physically meaningful.

The paper is devoted to an experimental research of the factors calling effect of pressure auto-stabilization of the gas discharge with the metal-hydride cathode. The experiments were carried out with low-pressure discharges in a magnetic field, using the cathodes made of hydrogen-saturated gettering alloys Zr - V, modified by oxide components. There were studied the dependencies of plasma density distributions and electron temperature in near-cathode zone, as well as temperature mode of the cathode, on the discharge current.

On the base of studying the heat regimes of the metal-hydride cathode in a Penning-like discharge cell it is shown, that up to 70 % of the energy of ions bombarding the cathode is spent for stimulation of hydrogen desorption from a metal hydride. It, in turn, results in extra cooling the cathode material with the flow of desorbed hydrogen. This flow forms a protective gaseous target near the cathode surface, which dissipates the energy of beam particles bombarding the metal-hydride material. As result, the sputtering of material by a flow of high-energy particles in vacuum is lesser extent than conventional construction materials. The model experiments on bombardment of composite material having the filler made of hydrogen-saturated zirconium getter alloy are show that this material has the increased stability under high current and high energy ion beams bombardment. Thus, the possibility of metal hydrides usage for sputtering protection of various construction elements under bombardement by high-energy beams in vacuum is shown.

The basic approaches and engineering solutions on metal hydrides usage in supply systems for vacuum physical-technical installations operating with hydrogen isotopes as a working medium are reviewed.

The processes of hydrides formation and decomposition at reversible interaction of a number of metals and alloys with hydrogen have a number of specific features. First of all it concerns to increased catalytic activity of hydrides of metals and intermetallic compounds in reactions connected to hydrogen transfer, i.e. hetero-phase isotope exchange [1], catalytic hydriding in gas and liquid phases [2,3], hydrogen saturation of alloys which are difficult for hydriding [4,5], low-temperature hydrogen oxidation with water formation [6], etc. The mentioned effects first of all were explained by hydrogen appearance in monatomic or any other excited state on metal surface or in a gas phase. In a number of experiments there was possible to identify and even “to preserve” for rather long time the H atoms formed during interaction of gaseous hydrogen with hydride forming materials. It has become possible due to spill-over effect of monatomic hydrogen along surfaces of A12O3, SiO2 and some other oxygen-containing phases. It has been shown, that hydrogen atoms migrating on a surface of these carriers have an effective positive charge [7,8]. The maximum emission of monatomic hydrogen was observed in a during its sorption-desorption using fresh palladium catalyst [7].

Metal-hydride thermosorption compressors (TSC) are expediently differ from conventional mechanical hydrogen compressors by that they have not moving parts working in hydrogen environment. Thus they have not moving seals. The given advantage is to the greatest extent exhibited at high pressure hydrogen force-pumping — 15.0 MPa and above. Besides, TSCs do not require the lubrications and characterised by dynamic steadiness and high purity of delivered hydrogen.

The problem «Hydrogen in Metals and in Intermetallic Compounds» is the subject of intensive investigations in quite a number of field both of fundamental character (solid state physics, inorganic, physical and structural chemistry, and others) and applicative character (hydrogen power and engineering, materials science, chemical current sources, etc.). During the past two decades this problem has been treated in hundreds of works, whose most exhaustive reviews were published in monographs [1,2]. To date investigated most exhaustively were the physico-chemical aspects of the given line of studies connected with obtaining of new hydride-forming materials, investigation of their structure and hydrogen sorption properties. Problems connected with the influence of hydrogen on the electron structure of metals and alloys, and elucidation of the essence of the metal-hydrogen bond in different hydrides are being intensively studied. A great number of works deal with investigation of the catalytic and electrochemical properties of metal hydrides.

Compression of gaseous hydrogen up to high pressure by conventional methods represents a difficult technical problem. The main problem here consists of a reliability of seals of moving parts. In this connection it would be tempting to use such engineering solutions which generally eliminate availability of mobile elements working in hydrogen medium.

An original compressor for generating hydrogen high pressures (up to 4 kbar) in a 30 cm 3 volume at room temperature is described. The construction has no moving mechanical components and consists of two different parts. The first one is a metal-hydride thermo-sorptive compression module based on the hydride-forming material MmNi 5 . Inlet pressure of the module is 1.5 MPa; discharge pressure is about 40 MPa. The second, cryogenic, part of the compressor consists of two cryo-stages that are designed as high-pressure containers of volume 60 and 30 cm 3 respectively. The cryogenic stages may be cooled to a temperature of 78 K and warmed to room temperature. At the lower temperature level in the cryo-stages, a hydrogen pressure of 40 MPa is generated by the hydride part of the compressor. Then, under consecutive heating-off of these two cryo-stages, the latter generates a pressure up to 400 MPa. A cycle period for generation of the maximal pressure is about 90 min. A combined construction of the compressor makes it possible to speed up significantly the process of hydrogen compression, to afford its high purity and at the same time to receive high pressure level in closed systems providing recovery of the working medium (hydrogen, deuterium, tritium) without any losses of the latter.

The hydrogen sorption and electrotransfer characteristics of hydride-coated cathodes were determined during plasma discharge experiments in a planar magnetron. The hydride alloys investigated were ZrVFe and ZrVFeBO. It is shown that the composition of the hydrogen gas discharge plasma is primarily determined by the peculiarities of the interaction of the plasma with metal hydride.

Features and testing results of experimental metal hydride cartridges (generators-sorbers) characterized with different ways of heat supply and dissipation are presented in this paper. The experimental data and heat-and-mass transfer calculations show that by an appropriate choice of working regime the coefficient of supplied energy transformation can be raised up to 0.3-0.4. Thermosorption compressors with improved dynamic characteristics, which provide single-step hydrogen compression up to 8.0–30.0 MPa, are described.

The sets of vertical ionization potentials for molecules of hydrogen (deuterium) desorbed from metal hydrides as well as for thermodynamically equilibrated molecular hydrogen (deuterium) at room temperature were obtained by means of the ionization efficiency curves method using mass-spectrometry measurements. Some sets of term differences are explained by thermoemission vibrational excitation of molecules. Comparative analysis to the data previously obtained is given. It was established that the anomalies of electrical transfer observed in the gas phase of metal-hydride-hydrogen systems are caused by vibrational excitation of H 2 -molecules, generated during recombination of H-atoms on the metal hydride sorbent surface.