Solubility Of Hydrogen Isotopes Research Articles

In-situ measurement of hydrogen isotope behavior in high temperature LBE: Diffusivity, permeability, and solubility

The Lead-Bismuth Fast Reactor (LBR) emerges as a promising concept due to its superior neutron economy, chemical stability, and thermal properties. From the nuclear safety standpoint, the focus has predominantly been on the behavior of 210Po and other fission products, while the issue of tritium in LBRs has not been sufficiently addressed due to the inconvenience of tritium experiments. Formation of tritium/helium bubbles induces significant local stress and volume expansion, leading to hardening and embrittlement of structural materials, thus expediting their degradation through irradiation effects. Current understanding of tritium transport within liquid Lead-Bismuth Eutectic (LBE) remains incomplete. To bridge this gap, a novel device employing the "permeation pot" method has been developed for the first experimental quantification of diffusivity, permeability, and solubility of hydrogen isotopes in liquid LBE. Notably, hydrogen diffusivity in this medium is found to be three to four orders of magnitude greater than in conventional 316L stainless steel structural material. Furthermore, the temperature-dependence of diffusivity in liquid metals is minimal compared to solids, as indicated by the activation energy. Conversely, solubility in 316L significantly surpasses that in LBE by three to four orders of magnitude. This discrepancy accelerates the tritium release from LBE to structural material, leading to the failure of the structural material.

Defect production in tungsten under sub-threshold energy irradiation: role of hydrogen and surface effects

Despite the low solubility of hydrogen isotopes (HIs) in tungsten (W), their concentration can reach up to ∼10 at.% after low-energy plasma irradiation. This is generally attributed to the vacancies that may accommodate excessive HIs. However, the kinetic energy of incident HIs transferred to W is far below the energy threshold to create a Frenkel pair, the underlying mechanism of defect production is still unclear. Here, we investigate the influence of H on the defect production in W using the molecular dynamic (MD) simulations. It is found that the threshold displacement energy (TDE) in bulk W slight decreases with the increasing of H concentration. This is due to the formation of H-vacancy complexes, which prevents the vacancy-interstitial recombination. More importantly, the H effects are significantly magnified in the surface region. On the one hand, the maximum kinetic energy transferred from 400 eV H to W can reach up to ∼21 eV due to the double-hit process, which is two times higher than that predicted by elastic collision model. On the other hand, the momentum transferred to W is completely random, including both the recoil direction upward and downward from the surface. Accordingly, the lowest TDE in W surface is only 15–21 eV at sub-surface layers with the depth of 6.7–11.1 Å, which is lower than the maximum kinetic energy transferred to W. Therefore, the low-energy HIs irradiation can create the defects in W surface directly. Our findings provide deep insight into defect production in W at sub-threshold energy and have wider implications for materials performance under low-energy ions irradiation.

“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.

Experimental determination of solubility values for hydrogen isotopes in eutectic Pb–Li

Hydrogen isotopes solubility in eutectic lithium–lead alloys is really important for the design of breeding blanket components that use this breeding material. The determination of the magnitude and kinetics of the tritium flux from the blanket to the helium cooling loop, along with the design of future tritium extraction systems of the breeding alloy or the He coolant purification system, will be defined on basic transport parameters such as solubility.The unacceptable scattering of Sieverts’ constant values in the historical measurements given by different experimental techniques, suggests that this is a very important and unresolved issue. In this work, it has been experimentally evaluated, using absorption and desorption techniques. The different measurement campaigns have been carried out in the temperature range from 523 to 922K and in the pressure range from 1 to 105Pa.This paper describes the work carried out in the preparation of the facility, the theoretical model developed to process the different results obtained by means of absorption and desorption runs. Final results obtained during several campaigns of measurements are provided.The obtained values of hydrogen solubility through the different campaigns show a similar value for the Sieverts’ constant, and therefore, a very little value for the activation energy in the solution process. Results are compared and discussed. The proposed correlation for hydrogen Sieverts’ constant in Pb–Li from these tests is KS [molm−3Pa−1/2]=8.64×10−3exp(–0.9/RT), R in (kJK−1mol−1).

Tritium Migration in HCLL and WCLL Blankets: Impact of Tritium Solubility in Liquid Pb-17Li

The next generation of fusion power plants (DEMO) should rely on a breeding blanket (BB) able to efficiently convert the neutrons kinetic energy into heat, to ensure the tritium self-sufficiency and to adequately shield the toroidal field coils from neutrons and gamma rays. The eutectic lithium-lead alloy is a consolidate liquid blanket material, which simultaneously includes the breeder (Li) and the neutron multiplier (Pb). The assessment of the tritium inventory inside the blanket and its environmental release requires knowledge of the hydrogen isotopes interactions with blanket materials, in particular the hydrogen solubility in lithium-lead, which is defined by means of the hydrogen Sievert's constant. Several experiments, aiming to determine the hydrogen isotopes solubility in lithium-lead, have been performed in the past giving values of the temperature-dependent Sieverts' constant, K , distributed in a wide range (covering about two orders of magnitude on the Arrhenius plot). Starting from a literature review of the K values, this paper provides a parametric analysis for the most influencing parameters related to tritium migration in helium-cooled and water-cooled lead-lithium DEMO BBs. This analysis has been performed using the computational code FUS-TPC for several operative scenarios and considering the different K values. This paper demonstrates that the tritium Sieverts' constant in Pb-17Li has a great impact on the assessment of tritium losses, whose value can spread in more than one order of magnitude. Furthermore, the analysis suggests suitable permeation reduction factors to be adopted in the different scenarios as well as the need of addressing new accurate experiments on the solubility constant.

Clarification of Tritium Behavior in Pb–Li Blanket System

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

Experiments of hydrogen isotope permeation, diffusion and dissolution in Li–Pb

The permeability, diffusivity and solubility of hydrogen isotopes (H, D) in a Li–Pb eutectic alloy are measured in the temperature range from 573 to 973K using a permeation method. Their isotope effects between H and D are obtained. It is shown that the solubility of hydrogen isotopes in Li–Pb obeys the Sieverts’ law. The solubility of D is around 1.4 times larger than that of H. The isotope effect of the diffusivity between H and D is very small.

Determination of hydrogen solubility in lead lithium using sole device

In the helium cooled lithium lead (HCLL) blanket for DEMO the breeding material is represented by eutectic lead lithium alloy flowing in poloidal–radial direction in the breeding module. The low solubility of hydrogen isotopes in the alloy generates an high partial pressure and, as a consequence, an high tritium permeation rate from the breeder into the He coolant and a considerable tritium inventory in the structural materials. Several experiments, devoted to determine the hydrogen solubility in lead lithium, have been performed in the past, giving contradictory results. To find a reliable value to be used in the safety analysis and in the design of both the tritium extraction system and the coolant purification system, the solubility of hydrogen (SOLE) experiment was launched in ENEA Brasimone in 2002. The SOLE device is based on the use of the absorption technique. The experimental results are in good agreement with the ones obtained in the past with similar techniques, varying from 1 × 10 −2 mol m −3 Pa −1/2 up to 7 × 10 −2 mol m −3 Pa −1/2. The experimental device and the obtained results are presented and discussed in this paper.

Solubility of hydrogen in Zircaloy-4: irradiation induced increase and thermal recovery

The solid solubility of hydrogen isotopes in neutron irradiated Zircaloy-4 core components removed after 10.3 years in service is studied by differential scanning calorimetry (DSC) in two cooling channels of the Atucha I Heavy Water Power Reactor, Argentina. For irradiated Zircaloy-4 samples containing 150–380 ppm-H eq the temperature for hydride dissolution, TSSd irrad, measured during the first DSC run was approximately similar to the reactor operating temperature (260–300 °C) and 50–150 °C lower than the TSSd for unirradiated material. This difference decreases in subsequent DSC runs and a stage of stable TSSd irrad intermediate values is reached. After further isothermal annealings the TSSd irrad values approach asymptotically TSSd. These results may be interpreted by assuming that a fraction of the total hydrogen isotope concentration, which is similar to the concentration that should be present in solid solution in unirradiated Zircaloy-4 at the operating temperature, is in solid solution in the irradiated Zircaloy-4 and the rest is trapped and slowly released from complex irradiation induced defects.

Behavior of deuterium implanted into W, Be and BeO

New results obtained during the study of D implanted W (001) single crystal are presented. The reemission curves at different temperatures, evolution of microstructure, in-depth profiling of radiation damage and implanted deuterium, retention of deuterium atoms and molecules are described. All the data are compared with the results on D implanted Be and BeO. The analysis includes consideration of the energetics of hydrogen isotopes solubility, diffusivity, trapping, and chemisorption for non-irradiated materials mentioned above.

Transport properties of hydrogen isotopes in boron carbide structures

The transport of implanted hydrogen isotopes in the refractory semiconducting ceramic, boron carbide, is investigated using the TMAP4 code. A review of experimental results for the diffusivity and solubility of hydrogen isotopes in boron carbide is presented, which provide Arrhenius expressions for the kinetics of hydrogen isotope transport. These expressions are utilized in the TMAP4 model to provide predictions for the hydrogen isotope implantation and desorption for experiments now in progress at the UCSD PISCES laboratory for the National Ignition Facility (NIF).

Hydrogen adsorption on and solubility in graphites

The experimental data on adsorption and solubility of hydrogen isotopes in graphite over a wide range of temperatures and pressures are reviewed. Langmuir adsorption isotherms are proposed for the hydrogen—graphite interaction. The entropy and enthalpy of adsorption are estimated, allowing for effects of relaxation of dangling sp 2 bonds. Three kinds of traps are proposed: edge carbon atoms of interstitial loops with an adsorption enthalpy relative to H 2 gas of −4.4 eV/H 2 (unrelaxed, Trap 1), edge carbon atoms at grain surfaces with an adsorption enthalpy of −2.3 eV/H 2 (relaxed, Trap 2), and basal plane adsorption sites with an enthalpy of +2.43 eV/H 2 (Trap 3). The adsorption capacity of different types of graphite depends on the concentration of traps which depends on the crystalline microstructure of the material. The number of potential sites for the ‘true solubility’ (Trap 3) is assumed to be about one site per carbon atom in all types of graphite, but the endothermic character of this solubility leads to a negligible H inventory compared to the concentration of hydrogen in type 1 and type 2 traps for temperatures and gas pressures used in the experiments. Irradiation with neutrons or carbon atoms increases the concentration of type 1 and type 2 traps from about 20 and 200 appm respectively for unirradiated (POCO AXF-5Q) graphite to about 1500 and 5000 appm, respectively, at damage levels above 1 dpa.

Diffusivity and Solubility of Hydrogen Isotopes in the Martensitic Steel DIN 1.4914 (MANET) after Thermal Exposure at 900 K*

Article Diffusivity and Solubility of Hydrogen Isotopes in the Martensitic Steel DIN 1.4914 (MANET) after Thermal Exposure at 900 K* was published on January 1, 1993 in the journal Zeitschrift für Physikalische Chemie (volume 181, issue 1-2).

Solubility of hydrogen isotopes in graphite

Solubility measurements of hydrogen and deuterium in isotropic graphites IG 110U and POCO AXF-5Q have been performed in the temperature range of 700–1000° C at pressures below 2×10 4 Pa by a constant volume method. All the solubility data closely obeyed Sieverts' law. The solubility of hydrogen was slightly different from that of deuterium. The solubility in IG 110U graphite was larger than that in POCO AXF-5Q graphite, while the enthalpy of solution was almost the same. On the basis of dilute solution model, the solubility of hydrogen isotopes in graphite was analyzed, and the partial thermodynamic functions were obtained. The isotope effect on solubility was discussed on the assumption that hydrogen isotope atoms behave as harmonic oscillators in the graphite matrix.

Poisoning effect on solubility of hydrogen isotopes in getter materials

Hydrogen and deuterium solubilities in Ti-C and Zr-N alloys with various compositions have been measured at pressures below 100 Pa. All of the solubility data were found to follow Sieverts' law. The presence of carbon in Ti increased the solubilities of hydrogen isotopes and reduced the enthalpies of solution. The solubility increased and the enthalpy of solution decreased with addition of nitrogen into Zr. The hydrogen solubility in Ti-C and Zr-N alloys was larger than the deuterium solubility. Partial thermodynamic functions of hydrogen and deuterium in Ti-C and Zr-N alloys were obtained by a dilute solution model and compared with those in Ti-(O, N) and Zr-O alloys. The isotope effect of hydrogen and deuterium solubilities in the Ti-(O, N, C) and Zr-(O, N) alloys was discussed, and the tritium solubility in Ti-C and Zr-N alloys was evaluated from hydrogen and deuterium data.

Effect of oxygen on solubility of hydrogen isotopes in titanium

Abstract Solubility measurements of hydrogen and deuterium gases in pure titanium and titanium—oxygen alloys with 10–30 at %O have been performed in the temperature range of 600–850°C at pressures below 100 Pa by a constant-volume method. All the solubility data obeyed Sieverts' law. The solubility of hydrogen in titanium and titanium—oxygen alloys was larger than that of deuterium. The solubility decreased with increasing oxygen content in titanium, while the enthalpy of solution was almost constant irrespective of the oxygen content. On the basis of the dilute interstitial solution model, the reduction in hydrogen solubility by solute oxygen was explained by the blocking effect. The isotope effect on solubility was discussed on the assumption that an interstitial hydrogen isotope atom behaves as a harmonic oscillator in the titanium matrix. The vibrational frequency of a hydrogen atom in titanium was obtained, which allowed a prediction of the tritium solubility. The estimated solubility of tritium in titanium and titanium—oxygen alloys was smallest, followed by deuterium and hydrogen.

Gas Bubble Nucleation and Tritium Permeation Through Metallic Walls in a Liquid 83Pb-17Li Blanket

Recent studies have given lower and lower values for the solubility of hydrogen isotopes in the eutectic 83Pb-17Li alloy, a candidate breeding material for the blanket of fusion machines. Therefore, thermodynamic stability for the gaseous phase under the high pressure reached at the bottom of the alloy containers can be achieved even for very low tritium concentrations in the liquid phase. A mathematical model to determine when tritium bubble nucleation occurs at an appreciable rate is presented. This model is used to predict tritium production behavior in the next European Torus (NET) tokamak.

Solubility of hydrogen isotopes in palladium

An all-metal facility has been built to handle about 1000 Ci of tritium for studies of the tritium behavior in metals. First measurements of the pressure-composition-temperature relationship for the palladium-tritium system $\mathrm{Pd}{\mathrm{T}}_{x}$ are reported for the pressure range $0.1\ensuremath{\le}p\ensuremath{\le}2$ bar, the composition range $0.02\ensuremath{\le}x\ensuremath{\le}0.65$, and the temperature range $35\ensuremath{\le}T\ensuremath{\le}125\ifmmode^\circ\else\textdegree\fi{}$C together with the results of the PdH and PdD systems measured under the same experimental conditions. The main conclusions are that the inequality ${p}_{{\mathrm{T}}_{2}}>{p}_{{\mathrm{D}}_{2}}>{p}_{{\mathrm{H}}_{2}}$ holds at equal concentrations and temperatures and that the $\ensuremath{\beta}\ensuremath{\rightarrow}\ensuremath{\alpha}$ transition enthalpies show a strong isotopic effect, whereas the entropies do not.

Solubility of lithium deuteride in liquid lithium

The solubility of LiD in liquid lithium between the eutectic and monotectic temperatures was measured using a direct sampling method. Solubilities were found to range from 0.0154 mol.% LiD at 199 °C to 3.32 mol.% LiD at 498 °C. The data were used in the derivation of an expression for the activity coefficient of LiD as a function of temperature and composition and an equation relating deuteride solubility and temperature, thus defining the liquidus curve. Similar equations were also derived for the Li-LiH system using the existing solubility data. Extrapolation of the liquidus curves yielded the eutectic concentrations (0.040 mol.% LiH and 0.035 mol.% LiD) and the freezing point depressions (0.23 °C for Li-LiH and 0.20 °C for Li-LiD) at the eutectic point. The results are compared with the literature data for hydrogen and deuterium. The implications of the relatively high solubility of hydrogen isotopes in lithium just above the melting point are discussed with respect to the cold trapping of tritium in fusion reactor blankets.

Hydrogen isotope diffusivity and solubility in nickel, palladium, and copper

An analysis is presented of diffusion coefficients and solubility of hydrogen isotopes in nickel, palladium, and copper. For describing the vibrational spectrum of solutions a harmonic approximation is used, and it is assumed that localized levels exist connected with oscillations of interstitial atoms. Atom jumps are described basing on absolute rate theory. Experimental data regarding the pre-exponentials in the temperature dependences of solubility, diffusion coefficients, and corresponding isotope effects are consistently described using an estimation model accounting for metal lattice deformation and charge of electron concentration upon dissolution of hydrogen, and assuming a jump mechanism: octa- tetra- octahedral interstitials. [Russian Text Ignored.]