High Deuterium Concentration Research Articles

Deuterium Ingress at the Rolled Joints in CANDU Reactors: Where Does It Come From and How Can It Be Reduced?

AbstractSimple, small-scale, experiments demonstrate that the initial protium in stainless-steel end fittings contributes to the high deuterium concentrations found in the zirconium pressure tubes at CANDU rolled joints. This protium isotopically exchanges becoming deuterium that is then gettered by the zirconium pressure tube. We propose to reduce the concentration of hydrogen isotopes at the ends of pressure tubes in heavy-water nuclear reactors with yttrium getters placed in the outer regions of the stainless-steel end fittings away from the heat-transport heavy water. Simple, small-scale, experiments demonstrate the operating principle showing that yttrium can getter hydrogen isotopes from the zirconium through the stainless steel.

In-situ ToF-SIMS analyses of deuterium re-distribution in austenitic steel AISI 304L under mechanical load

Hydrocarbons fuel our economy. Furthermore, intermediate goods and consumer products are often hydrocarbon-based. Beside all the progress they made possible, hydrogen-containing substances can have severe detrimental effects on materials exposed to them. Hydrogen-assisted failure of iron alloys has been recognised more than a century ago. The present study aims to providing further insight into the degradation of the austenitic stainless steel AISI 304L (EN 1.4307) exposed to hydrogen. To this end, samples were electrochemically charged with the hydrogen isotope deuterium (2H, D) and analysed by scanning electron microscopy (SEM), electron back-scatter diffraction (EBSD) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). It was found that deuterium caused a phase transformation from the original γ austenite into ε- and α’-martensite. Despite their low solubility for hydrogen, viz. deuterium, the newly formed phases showed high deuterium concentration which was attributed to the increased density of traps. Information about the behaviour of deuterium in the material subjected to external mechanical load was gathered. A four-point-bending device was developed for this purpose. This allowed to analyse in-situ pre-charged samples in the ToF-SIMS during the application of external mechanical load. The results indicate a movement of deuterium towards the regions of highest stress.

In Vitro Study of Deuterium Effect on Biological Properties of Human Cultured Adipose-Derived Stem Cells.

In current in vitro study we have shown the impact of deuterium content in growth medium on proliferation rate of human cultured adipose-derived stem cells (ADSC). ADSCs have also demonstrated morphological changes when cultured in deuterated growth medium: the cell cultures did not reach confluence but acquired polygonal morphology with pronounced stress fibers. At high deuterium concentrations the ADSCs population doubling time increased which indicated the cell cycle retardation and decrease of cell proliferation rate. The deuterated and deuterium-depleted growth media demonstrated acute and chronic cytotoxicity, respectively. The minimal migration ability was observed in deuterated medium whereas the highest migration activity was observed in the medium with the deuterium content close to natural. The cells in deuterated growth medium demonstrated decrease in metabolic activity after three days in culture. In contrast, in deuterium-depleted medium there was an increase in ADSC metabolic activity.

Direct depth distribution measurement of deuterium in bulk tungsten exposed to high-flux plasma

Understanding tritium retention and permeation in plasma-facing components is critical for fusion safety and fuel cycle control. Glow discharge optical emission spectroscopy (GD-OES) is shown to be an effective tool to reveal the depth profile of deuterium in tungsten. Results confirm the detection of deuterium. A ∼46 μm depth profile revealed that the deuterium content decreased precipitously in the first 7 μm, and detectable amounts were observed to depths in excess of 20 μm. The large probing depth of GD-OES (up to 100s of μm) enables studies not previously accessible to the more conventional techniques for investigating deuterium retention. Of particular applicability is the use of GD-OES to measure the depth profile for experiments where high deuterium concentration in the bulk material is expected: deuterium retention in neutron irradiated materials, and ultra-high deuterium fluences in burning plasma environment.

Concentration Dependence of the Rate of Catalytic Isotopic Exchange of Hydrogen with Water Vapor on the Catalyst RKhTU-3SM

One method of separating hydrogen isotopes is chemical isotopic exchange of hydrogen with liquid water, combined with electrolysis of water. At present, different mathematical models are used to calculate the characteristics of newly developed setups. They all have the problem of inadequate data on the characteristics of the chemical isotopic exchange process occurring at medium and high deuterium concentrations. The present work is devoted to investigating one stage of chemical isotopic exchange – catalytic isotopic exchange between hydrogen and water vapor at high deuterium concentrations in application to the catalyst RKhTU-3SM. It is shown that the experimental rate constant of isotopic exchange for the pair protium – deuterium increases by almost a factor of two, while for exchange with tritium increasing the deuterium concentration from 5 to 95% does not change the experimentally observed rate constant to within the measurement error.

Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) imaging of deuterium assisted cracking in a 2205 duplex stainless steel micro-structure

In the present work, the influence of deuterium on the microstructure of a duplex stainless steel type EN 1.4462 has been characterized by Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) supported by scanning electron microscopy (SEM), focused ion beam (FIB), electron back scattered diffraction (EBSD) and energy dispersive x-ray (EDX) investigations. Characterization has been carried out before and after electrochemical charging with deuterium which has been used as a tracer, due to its similar behavior to hydrogen in the steel microstructure. In a first approach, the distribution of the deuterium occurring at temperatures above −58°C has been visualized. Further it turned out that sub-surface micro blisters are formed in the ferrite-austenite interface, followed by the formation of needle shaped plates and subsequent cracking at the ferrite surface. In the austenite phase, parallel cracking alongside twins and hexagonal close packed (martensitic) regions has been observed. In both phases and even in the apparent interface, cracking has been associated with high deuterium concentrations, as compared to the surrounding undamaged microstructure. Sub-surface blistering in the ferrite has to be attributed to the accumulation and recombination of deuterium at the ferrite-austenite interface underneath the respective ferrite grains and after fast diffusing through this phase. Generally, the present application of chemometric imaging and structural analyses allows characterization of hydrogen assisted degradation at a sub-micron lateral resolution.

EPR and photoluminescence spectra of smooth CD x films from T-10 tokamak: The effect of iron impurity

The electron and spin structure of thick smooth hydrocarbon CDx films (“flakes”) with a high relative deuterium concentration of x ~ 0.5, redeposited from deuterium plasma discharge onto the walls of the vacuum chamber of the T-10 tokamak and containing ~1 at % of 3d-metal impurities due to erosion of the chamber walls, are studied using electron paramagnetic resonance (EPR) and photoluminescence (PL). The resulting spectra are compared for the first time to the EPR and photoluminescence spectra of polymer (soft) a-C:H(D) films (H(D)/C ~ 0.5), which are considered model analogues of smooth CDx films. A certain similarity of the CDx films with a-C:H films was found in the electronic structure of the valence band. At the same time, the differences in the EPR and photoluminescence spectra were observed due to the presence of 3d-metal impurities in the CDx samples, contributing to the conversion of sp3 → sp2 in the formation of films in the tokamak and upon heating and thermal desorption. An impurity of, presumably, 3d metals was detected for the first time by EPR in the a-C:H films in an amount of approximately 0.2 ppm, related to the evaporation of graphite.

Isotopic effects of low concentration of deuterium in water on biological systems

Isotopic effects of deuterium in water are studied in a broad range of concentrations on a number of biological objects of different organization levels. The results obtained show that biological objects are sensitive to variations of isotope composition in water. A decrease or increase in deuterium concentrations in water may cause activation or inhibition of biological functions. The values of biological isotopic effects of low deuterium concentration may even be higher than those of high deuterium concentration. No regularity in response for all the objects studied failed to find out in a range of deuterium concentration in water from 4 ppm to 1%.

Study on rapid growth of 98% deuterated potassium dihydrogen phosphate (DKDP) crystals

Tetragonal 98% deuterated potassium dihydrogen phosphate (DKDP) crystals were grown rapidly from synthetic DKDP solution with higher deuterium concentration by using point-seeds technique. Crystallization was carried out under high supersaturation at different temperatures ranging from 38.3°C to 51.0°C. It is found that the metastable region of DKDP solution is non-specific and DKDP crystal can be grown from high starting temperature beyond the traditional metastable region. For comparison, monoclinic DKDP crystals were grown from the same solution. Surface morphologies of tetragonal and monoclinic DKDP crystals were investigated by AFM technique. The different growth habits between tetragonal and monoclinic DKDP crystals were analyzed according to their crystal structures with bond valence model.

Microanalysis of deposited layers in the divertor of JET following operations with carbon wall

Elemental mapping of cross sections of deposited layers on inboard tiles in the JET divertor after exposure to plasma operations with carbon wall are presented. The study was made using microbeam ion beam analysis methods in combination with optical microscopy and SEM. The surfaces had been exposed to plasma through different periods of operation (1998–2007, 2007–2009 and 1998–2009). The texture and composition of the layers are non-uniform. The physical structures include columnar, lamellar and disordered globular appearances. The distribution of trapped deuterium was frequently found to be lamellar, with well-defined sub layers with higher deuterium concentration. However, 3D regions with dimensions of about 100 μm with enhanced deuterium content were also found, both at the layer surfaces and in the layer cross sections. The distributions of beryllium and Inconel components were lamellar but did not otherwise show large non-uniformity on the same scale length as the deuterium.

Structural transformations in the deuterium-containing intermetallic compound (Ti3Al)D1.2 induced by high-pressure torsion

The intermetallic compound Ti3Al (which is a very brittle material) with a high deuterium concentration (x = 1.2) is fabricated in a monolithic state by high-pressure torsion at room temperature. The structure of the intermetallic samples is studied by X-ray diffraction and transmission electron microscopy after deformation at various degrees. Under certain conditions, the main volume of the material is found to transform into an amorphous state, and areas 1–2 nm in size with an atomic arrangement close to the initial arrangement are also present in the material. The possible causes of the deformation-induced amorphization of the material alloyed with interstitial atoms are discussed.

Deuterium retention in carbon flakes and tungsten–carbon mixed flakes produced by deuterium arc discharge

In order to estimate the in-vessel tritium inventory of carbon flakes or dust, deuterium gas absorption and deuterium ion irradiation experiments were conducted on carbon flakes prepared by using electron beam evaporation of graphite. The retained amount of deuterium after the deuterium gas absorption was very low; D/C = 10−3 atomic ratio. The retained amount of deuterium after the deuterium ion irradiation was very similar when compared with that for graphite. The deuterium concentration of the carbon flakes resulting from ion irradiation becomes close to zero if the wall temperature is higher than 1000 K. Co-deposited carbon flakes were prepared by a deuterium arc discharge with carbon electrodes at different gas pressures and substrate temperatures. The co-deposited carbon flakes had a high deuterium concentration. Under such conditions with gas pressure of 1 Pa and wall temperature of 573 K, the deuterium concentration becomes approximately D/C = 0.2. In a DT fusion device like ITER, we therefore, expect a T/C ratio of 0.1. This value is presumed to be an upper limit of carbon flakes in ITER since the wall temperature may be higher than 573 K. Tungsten–carbon mixed flakes were also produced by the deuterium arc discharge with carbon and tungsten electrodes. The deuterium was trapped mainly in the carbon atoms and the structure of carbon in the tungsten–carbon mixed flakes was more amorphous compared with that of the co-deposited carbon flakes. Then, the deuterium concentration was higher than that of the carbon flakes, and increased with the increase in the concentration of tungsten. The higher concentration in the tungsten–carbon mixed flakes may not affect the in-vessel tritium inventory if the tungsten concentration is low.

Neutron scattering study of the Cs 5H 3(SO 4) 4·0.5H 2O crystal and its deuterated analog

This paper describes studies of the effect of deuteration on the structure and dynamics of the Cs 5H 3(SO 4) 4·0.5H 2O lattice at low temperatures by inelastic neutron scattering and neutron powder diffraction. It has been found that diffraction spectra of Cs 5H 3(SO 4) 4·0.5H 2O and its deuterated analog with a high deuterium concentration differ by the number of reflex.

The Effect of Forming Gas Annealing on Pt/(Ba,Sr)TiO3/Pt Thin Film Capacitors for Future Dram Applications: Electrical Properties and Degradation Mechanisms

AbstractWe have used electrical characterization and secondary ion mass spectroscopy (SIMS) to investigate the influence of hydrogen or deuterium (H/D) on the degradation of the electrical properties of Pt/Ba0.7Sr0.3TiO3/Pt thin film capacitors after forming gas exposure. Deuterium SIMS depth profiling shows that high deuterium concentrations can be incorporated into Pt/BSTO/Pt capacitors after forming gas annealing. The increase in H/D concentration in the film is accompanied by an increase in the leakage and dielectric relaxation current density. Voltage offsets in the capacitance-applied voltage (C-VA) characteristics after forming gas exposure at lower temperatures (20 °C) and a suppression in the capacitance density near zero applied D.C. bias after forming gas exposure at higher temperatures, suggests that one effect of forming gas exposure to Pt/BSTO/Pt thin film capacitors is to introduce positive space charge into the BSTO film. Using an equivalent model for a ferroelectric thin film capacitor, which incorporates lower permittivity interfacial layers and a nonlinear electric field-electric displacement relationship for the film interior, the effects of a uniform distribution of positive space charge on the theoretical C-VA and current density applied voltage (J-VA) characteristics are investigated. It is shown the model can account for many of the observed changes that occur in the experimental C-VA and J-VA characteristics after forming gas exposure.

Effect of temperature and deuterium concentration on the growth of deuterated potassium dihydrogen phosphate (DKDP) single crystals

The growth condition of tetragonal phase deuterated potassium dihydrogen phosphate (DKDP) with higher deuterium concentration is optimized for the growth of large size crystals. The variation of lattice parameter values of the crystal in comparison with potassium dihydrogen phosphate (KDP) crystal is found. Etching studies have been done for both monoclinic and tetragonal phases of the DKDP crystals. The percentage and range of transmission of KDP and DKDP crystals were found from uv – visible spectroscopy.

Theoretical analysis of ICRF heating in JET DT plasmas

A number of experiments with heating of DT plasmas using ICRF waves have been carried out at JET. The results of these experiments have been analysed by comparing experimentally measured quantities with the results of numerical simulations. In particular, four scenarios have been examined: (a) heating of minority (∼5-20%) deuterons at the fundamental ion cyclotron frequency, ω = ωcD; (b) second harmonic heating of tritium, ω = 2ωcT; (c) fundamental minority heating of 3He with a few per cent of 3He; (d) second harmonic heating of deuterium, ω = 2ωcD. An important aim of the analysis was to assess whether the present understanding of the ICRF physics is adequate for predicting the performance of ICRF in DT plasmas. In general, good agreement between experimental results and simulations was found which increases the confidence in predictions of the impact of ICRF heating in future reactors. However, when a relatively high deuterium concentration was used in the ω = ωcD scenario, discrepancies were observed. In order to increase confidence in the simulations, the sensitivity of the simulation results to various plasma parameters has been studied.

Hydrogen Internal Friction and Interaction of Solute Atoms in Niobium- and Vanadium-Based Alloys

A computer model has been proposed to be used to calculate the internal friction spectrum, caused by the “diffusion under stress” of hydrogen atoms in a solid solution with a b.c.c. lattice containing substitutional atoms. The model takes into account the long-range pair interaction of dissolved atoms. It is suggested that such interaction acts on diffusion by producing short-range order of mobile hydrogen atoms and by changing their energy. These changes occur in the tetrahe- dral (before the jump) as well as in the octahedral (at the saddle point of the diffusion barrier) interstitial sites and, therefore, produce local changes of the hydrogen diffusion activation energy (the activation energy of internal friction). The relaxation strength is calculated from the local fields of atomic displacements around every atom that participates in diffusion. The model has been used to study the nature of hydrogen relaxation in Ti- and Zr-containing Nb- and V-based alloys and to calculate the “chemical” interaction energy of the H(D)±Ti(Zr) pairs. It was shown that the hydrogen relaxation mechanism in Nb(V)–Ti(Zr)–H(D) alloys consists in diffusion under stress of hydrogen or deuterium atoms in the vicinity of single substitutional atoms at low concentration of substitutional atoms and high hydrogen or deuterium concentration, and in the vicinity of substitutional pairs — at high concentration of substitutional atoms and low hydrogen or deuterium concentration. The “chemical” interaction H(D)–Ti(Zr) in niobium and vanadium is stronger or is of the same order, as the strain-induced (elastic) interaction.

Lattice Ion Trap: Classical and Quantum Description of a Possible Collision Mechanism for Deuterons in Metal Lattices

The dynamics of deuterons inside a palladium lattice around tetrahedral sites at high deuterium concentration is studied by using both a classical description and a quantum mechanical representation, and the results are compared. The classical representation takes advantage of the similarity between the electrodynamic confinement of charged particles stored in a quadrupolar radio-frequency trap and the palladium lattice. The quantum mechanical description of the dynamics of a charged particle interacting with another charged particle within a lattice radio-frequency trap is carried out by solving the time-dependent Schrödinger equation with a numerical procedure. Both descriptions produce an interaction effect between the deuterons inside the metal lattice.

Hydrogen migration in polycrystalline silicon.

Hydrogen migration in solid-state crystallized and low-pressure chemical-vapor-deposited (LPCVD) polycrystalline silicon (poly-Si) was investigated by deuterium diffusion experiments. The concentration profiles of deuterium, introduced into the poly-Si samples either from a remote D plasma or from a deuterated amorphous-silicon layer, were measured as a function of time and temperature. At high deuterium concentrations the diffusion was dispersive depending on exposure time. The dispersion is consistent with multiple trapping within a distribution of hopping barriers. The data can be explained by a two-level model used to explain diffusion in hydrogenated amorphous silicon. The energy difference between the transport level and the deuterium chemical potential was found to be about 1.2--1.3 eV. The shallow levels for hydrogen trapping are about 0.5 eV below the transport level, while the deep levels are about 1.5--1.7 eV below. The hydrogen chemical potential ${\mathrm{\ensuremath{\mu}}}_{\mathrm{H}}$ decreases as the temperature increases. At lower concentrations, ${\mathrm{\ensuremath{\mu}}}_{\mathrm{H}}$ was found to depend markedly on the method used to prepare the poly-Si, a result due in part to the dependence of crystallite size on the deposition process. Clear evidence for deuterium deep traps was found only in the solid-state crystallized material. The LPCVD-grown poly-Si, with columnar grains extending through the film thickness, displayed little evidence of deep trapping, and exhibited enhanced D diffusion. Many concentration profiles in the columnar LPCVD material indicated complex diffusion behavior, perhaps reflecting spatial variations of trap densities, complex formation, and/or multiple transport paths. Many aspects of the diffusion in poly-Si are consistent with diffusion data obtained in amorphous silicon. \textcopyright{} 1996 The American Physical Society.

Analysis of long term samples in Tore Supra

Long term samples have been installed on the inner wall in Tore Supra to monitor the surface modification of the graphite tiles. Surface analyses have shown a very low metallic impurity concentration (∼ 10 16 at/cm 2) dominated by stainless steel compounds. The high deuterium concentration (> 10 18 at/cm 2) is due to a codeposition with carbon atoms. Carbon layers of about 1 μm have been measured from which we deduced a carbon recycling coefficient R C = 0.99.