Hydrogen Inventory Research Articles

Contribution of the Moon-forming Impactor to the Volatile Inventory in the Bulk Silicate Earth

The timing and mechanism by which the present-day inventory of life-essential volatiles hydrogen–carbon–nitrogen–sulfur (H–C–N–S) in the bulk silicate Earth (BSE) was established are debated. In this study we have modeled the equilibrium partitioning of H–C–N–S between core, magma ocean (MO), and atmosphere to determine whether the Moon-forming impactor (MFI) was the primary source of volatiles in the BSE. Our findings suggest that the MFI’s core and MO-degassed atmosphere were its primary H–C–N–S reservoirs. Since the MFI likely lost its MO-degassed atmosphere before the giant impact, most of the BSE’s volatiles must come from the small fraction of the MFI’s core which reequilibrated with Earth’s post-impact MO. This implies a high H–C–N–S inventory in the MFI (up to 50% of volatile-rich carbonaceous chondrites) to establish the BSE’s volatile budget. Although isotopic compositions of nonvolatile elements do not rule out the possibility of substantial volatile-rich, carbonaceous material accretion, MFI’s collisional growth from thermally metamorphosed/differentiated planetesimals makes it improbable that it contained ∼50% carbonaceous chondrite equivalent of H–C–N during its differentiation. Therefore, the MFI was unlikely the primary source of volatiles in the BSE. A significant portion of the BSE’s volatile inventory (especially H and C) likely predates the Moon-forming event. To prevent loss to space and segregation into Earth’s core, volatile-bearing materials must be delivered during the final accretion event(s) preceding the Moon-forming event. The substantial size of the proto-Earth at this stage, combined with limited metal–silicate equilibration during the Moon-forming event, facilitated the retention of these volatiles within the BSE.

3D effects on hydrogen transport in ITER-like monoblocks

The influence of recombination on the poloidal gaps of ITER-like monoblocks on hydrogen transport simulations is investigated. A 3D FESTIM model is first built and transient simulations up to 1×107 s of continuous exposure are run with or without instantaneous recombination on the poloidal gaps. In the case of instantaneous recombination, the poloidal gaps act as a strong sink for hydrogen leading to a decrease in the monoblock inventory. The total desorption flux on the poloidal gap is greater than on the toroidal gap but remains orders of magnitude lower than the retro-desorbed flux at the top surface. For a monoblock thickness of 4 mm, the relative difference in the hydrogen inventory per unit thickness between the two cases is 500%. As the thickness of the monoblock increases, this difference decreases (55% at 14 mm). The monoblock’s response to baking is then studied at different baking temperatures. At 600 K, almost all the hydrogen content in the monoblock is removed after 15 days of baking. Assuming a non-instantaneous recombination on the tungsten surfaces would not have a major impact on the monoblock desorption for baking temperatures above 600 K.

Experimental studies on a closed cycle compressor operated metal hydride based cooling system with large hydrogen inventory

The current manuscript reports the experimental results of a closed loop metal hydride (MH) based compressor driven cooling system (CDCS) employing large-scale reactors. Two identical tube bundle reactors (TBR) with 19 MH tubes were designed, constructed and packed with 26.5 kg La0.8Ce0.2Ni5 alloy each for the experiments. The TBR modules were coupled with a custom-built compressor to provide cooling effect in quasi-continuous mode of operation. The compressor was tested to operate smoothly up to a hydrogen flow rate of 0.5 g. s−1 in the temperature range of 10–35 °C, yielding pressure ratio up to 12.8. Test runs were performed by altering refrigeration temperature (10–20 °C), sink temperature (30–35 °C), and half-cycle time (120–600 s). The maximum cooling power attained at 20 °C refrigeration temperature and 30 °C sink temperature was 1.44 kW, generating 537.3 kJ cooling within 600 s. The corresponding mean coefficient of performance (COP) and specific cooling power (SCP) were 0.95 and 36.4 W.kg−1 for 480 s half-cycle time. To avoid overheating of the compressor base, the half-cycle time was restricted to maximum of 600 s.

Testbed for the Pellet Launching System for JT-60SA

As part of the European contribution to the large size superconducting tokamak project JT-60SA, a new Pellet Launching System (PLS) is designed and built. The aims of the PLS are to provide efficient fuelling to the plasma and to control and mitigate Edge Localised Modes (ELMs). Two pellet sources, one for fuelling pellets, one for pacing pellets, are delivering pellets to a centrifuge launcher. The centrifuge enables precise launch of pellets according to already proven control schemes. Furthermore, this system opens a way towards a test bed for the EU-DEMO fuelling system. The new PLS has to be completed and commissioned first at the IPP Garching pellet lab and then to be shipped to QST Naka site after having demonstrated its performance. This dedicated test bed has been set up, providing suitable vacuum conditions to operate the PLS in similar conditions (except magnetic field and radiation). Maximum hydrogen throughput is about 400 mbar·L/s per pellet source. Safety issues must be considered for hydrogen inventory of pellet sources (∼100 bar·L each). In a first step, the pellet sources will be put on a test vessel providing inherent safety by a huge volume (10 m³) which makes sure that the hydrogen concentration is below 1% under all circumstances. A hydrogen safety survey prior to assembly confirmed the concept to be followed by an assessment after the installation in order to get the required license for operation. The PLS as a whole, for the time being equipped with two pellet sources, is to be certified according to explosion prevention rules (ATEX) as a product to be shipped to Naka site. To obtain this, an appropriate declaration of explosion zones inside the vacuum system and the use of suitable and certified equipment is mandatory. Such, the integration of this system can be planned and assessed on a clear technical and regulatory basis.

Analytical model of hydrogen inventory saturation in the subsurface of the wall material and comparison to Reaction-Diffusion simulations

We herein introduce an analytical model of hydrogen inventory saturation in the subsurface of materials (several micrometers depth) under plasma implantation. This model is valid for materials for which the desorption process is not limited by hydrogen recombination at the surface. It is based on a simplified assumption for the implantation of both hydrogen ions and atoms (point sources) and on a stationary approach. The model provides an approximation of the density profile of mobile/interstitial hydrogen and of the density profile of hydrogen trapped at materials defects in the subsurface layer. The analytical model shows good agreement with Reaction-Diffusion simulations of deuterium implantation in tungsten at different material temperatures. For the fusion relevant materials tungsten and beryllium, it is shown that most of the inventory is found in traps. The model gives the filling ratio of traps in the subsurface at steady-state fstat,iBULK. This simple parameter indicates how the total subsurface inventory builds up during plasma exposure and provides a simple way to understand the retention dynamics observed during non-linear Reaction-Diffusion simulations.

Influence of traps reversibility on hydrogen permeation and retention in Eurofer97

The presence of three trapping sites in Eurofer97 and the diffusion and trapping parameters obtained in a previousarticle are confirmed using an additional thermal desorption spectrometry experiment. Using these parameters, permeation cycles are simulated using the diffusion–reaction code mhims in order to study the influence of each trapping site on the permeation dynamics. The concept of traps reversibility is used to qualify this influence. The analysis indicates that the reversibility of the trapping sites is a key parameter in diffusion and permeation dynamics, which must be accounted for to get accurate predictions of hydrogen inventory and permeation.

Design of an in-situ measurement system for ortho and para liquid hydrogen fractions at ESS

The Cryogenic Moderator System (CMS) is equipped with a catalyst to convert hydrogen from the ortho state to the para state, to keep desirably high parahydrogen fractions in the cold moderators, which is required to deliver a high brightness cold neutron beams to the scientific instruments using neutron scattering. An in-situ measurement system for the ortho and para fractions of liquid hydrogen (OPMS) where a Raman spectroscopy will be used is being developed. The required measurement precision is 0.1% to detect an undesirable shift towards a high orthohydrogen fraction caused by neutron scattering driven para-to-ortho back conversion. The dedicated OPMS sampling line has been designed and is placed in a bypass line from and to the CMS to minimize the hydrogen inventory and to make it physically isolated from the CMS if a sapphire window failure happens. Accident analysis for a hydrogen leak due to the sapphire window failure was carried out using an inhouse-developed simulation code, and the required safety relief size has been determined.

The pre-atmospheric hydrogen inventory of CM carbonaceous chondrites

Understanding the quantity and isotopic composition of water that has been delivered to Earth over its history is crucial for models our planet’s evolution, and predicting habitability across the solar system. Here we have used stepwise pyrolysis to measure the hydrogen inventory of CM carbonaceous chondrites, which are likely to have been a major source of volatiles for the early Earth. Stepwise pyrolysis potentially enables the carriers of pre-terrestrial hydrogen to be identified, and distinguished from hydrogen that may have been added during the meteorite’s time on Earth. Twelve CM meteorites were analysed, and from their bulk hydrogen composition, petrologic type and nature of parent body processing, they can be divided into three subsets. The CMs of subset A have been mildly aqueously altered. Their hydrogen is hosted by isotopically light phyllosilicate, isotopically heavy organic matter, and adsorbed terrestrial water that is comparable to or slightly heavier than phyllosilicate. The subset B meteorites have been heavily aqueously altered and their hydrogen is also in phyllosilicate, organic matter and adsorbed terrestrial water. Their pyrolysis profiles differ from subset A in that the phyllosilicates dehydroxylate at higher temperatures owing to differences in mineralogy and chemical composition. The hydrogen that was evolved from organic matter may also have been isotopically lighter owing to loss of deuterium during aqueous alteration. Subset C meteorites were heated on their parent body after aqueous alteration, leading to loss of hydrogen from phyllosilicates and organic matter such that half of the water that they evolve was added after falling to Earth. Taking the 12 CMs together, an average of 0.20 wt.% H (21 % of total H) is terrestrial, and recalculation of bulk compositions without this component can raise bulk δD of individual meteorites by up to 73‰. Carbonaceous chondrites in our collections differ in the abundance and isotopic composition of hydrogen relative to their parent asteroid(s). An accurate understanding of the nature of water that was delivered to early Earth can only come from the analysis of materials that have been isolated from the terrestrial atmosphere, such as those returned from Ryugu and Bennu.

Hydrogen safety retrofit of ASDEX Upgrade pellet centrifuge - Explosion prevention on fuelling devices

• Explosion prevention rules and their application are evolving over the years. • Both loss of power and loss of vacuum are to be considered at once. • No hazardous zone required for normal operation pressure below 0.5 kPa. • Additional volumes in critical areas avoid the need to declare hazardous zones. • Hydrogen concentration below 1 % under disturbed conditions considered safe. Future fusion reactors will require fuelling by cryogenic pellets made from a mixture of deuterium and tritium. Nowadays fusion experiments are running with protium or deuterium plasmas in order to reduce radiological licensing issues but the hydrogen safety has to be addressed as well. The ASDEX Upgrade pellet centrifuge is serving for experiments to fuel the plasma or to pace Edge Localized Modes (ELMs) since 1991 and was continuously adapted to new tasks. The hydrogen safety was based on a limited hydrogen inventory, preventing the system from explosive atmosphere in case of incidents: loss of vacuum or loss of power. In order to get the system licensed, both failure scenarios must be considered at once. The actual system did not meet these requirements. Furthermore, part of the present equipment was not licensed to be operated in hazardous zones according to explosion protection regulations. Many of these components could not be replaced by classified ones, in particular components of the cryostat and the centrifuge itself. The goal of the new concept is to minimize the part of the system classified as hazardous zones. Such classification can be avoided in case the following two conditions apply at the same time: a pressure level below 50 mbar under normal operating conditions and a hydrogen concentration below 1 % (25 % of the lower explosion limit) under disturbed conditions. A new setup was developed in order to reduce the complexity of the existing vacuum system, introducing buffer volumes and implementing proper safety routines to withstand the presence of two incidents at once. Doing so, the classifications of hazardous zones could be reduced to areas, where appropriate licenced components were available (e.g. rough vacuum gauges and dry pumps). The system was successfully licensed and commissioned, first experimental results show enhanced system performance.

Hydrogen induced lattice expansion and site occupation analyzed by ion beam methods

We study the absorption of H in ultrathin crystalline Fe/V stacks using elastic recoil detection (ERD) and resonant nuclear reaction analysis (NRA) combined with Rutherford backscattering spectrometry (RBS). Probing with the resonant 1H (15N,αγ) 12C nuclear reaction allows us to profile the hydrogen concentration with high depth resolution, while ERD permits us to quantify the integral hydrogen inventory while minimizing possible ion-beam induced hydrogen desorption. We perform angular scans in order to directly identify the interstitial site occupancy. A detailed analysis of channeling patterns permits us the deduction of crystal strain in as-deposited films as well as H-loaded targets. We observe tetragonal strain formation resulting in c/a = 1.06 and find qualitative indications for tetrahedral site occupation.

Parametric study of hydrogenic inventory in the ITER divertor based on machine learning

A parametric study is performed with the 2D FESTIM code for the ITER monoblock geometry. The influence of the monoblock surface temperature, the incident ion energy and particle flux on the monoblock hydrogen inventory is investigated. The simulated data is analysed with a Gaussian regression process and an inventory map as a function of ion energy and incident flux is given. Using this inventory map, the hydrogen inventory in the divertor is easily derived for any type of scenario. Here, the case of a detached ITER scenario with inputs from the SOLPS code is presented. For this scenario, the hydrogen inventory per monoblock is highly dependent of surface temperature and ranges from 10^{18} to 6 times 10^{19} H after a 10^{7} s exposure. The inventory evolves as a power law of time and is lower at strike points where the surface temperature is high. Hydrogen inventory in the whole divertor after a 10^{7} s exposure is estimated at approximately 8 g.

Numerical analysis of hydrogen release, dispersion and combustion in a tunnel with fuel cell vehicles using all-speed CFD code GASFLOW-MPI

Hydrogen energy is expanding world-widely in recent years, while hydrogen safety issues have drawn considerable attention. It is widely accepted that accidental hydrogen release in an open-air environment will disperse quickly, hence not causing significant hydrogen hazards. A hydrogen hazard is more likely to occur when hydrogen is accidentally released in a confined place, i.e. parking garages and tunnels. Prediction the main accident process, including the hydrogen release, dispersion, and combustion, is important for hydrogen safety assessment, and ensuring the safety installations during accidents. Hence, a postulated accident scenario induced by the operation of Thermal Pressure Relief Device in a tunnel is analysed for hydrogen fuel cell vehicles with GASFLOW-MPI in this study. GASFLOW-MPI is a well validated parallel CFD code focusing on the transport, combustion, and detonation of hydrogen. It solves compressible Navier-Stokes equations with a powerful all-speed Arbitrary-Lagrangian-Eulerian (ALE) method; hence can cover both the non-compressible flow during the hydrogen release and dispersion phases, and the compressible flow during deflagration and detonation. In this study, a 3D model of real-scaled tunnel is modelled, firstly. Then the hydrogen dispersion in the tunnel is calculated to evaluate the risk of Flame acceleration and the Deflagration-Detonation Transient (DDT). The case with jet fire is analysed with assuming that the hydrogen is ignited right after being injected forming a jet fire in the tunnel, the consequence of this case is limited considering the small hydrogen inventory. The detonation in the tunnel is calculated by assuming a strong ignition at the top of the tunnel at an unfavourable time and location. The pressure loads are calculated to evaluate the consequence of the hazard. The analysis shows that the GASFLOW-MPI is applicable at a widely range for tunnel accidents, meanwhile, the safety issues related to tunnel accidents is worthy further study considering the complexity of tunnels.

Hydrogen isotopic evidence for early oxidation of silicate Earth

The Moon-forming giant impact extensively melts and partially vaporizes the silicate Earth and delivers a substantial mass of metal to Earth's core. The subsequent evolution of the magma ocean and overlying atmosphere has been described by theoretical models but observable constraints on this epoch have proved elusive. Here, we report thermodynamic and climate calculations of the primordial atmosphere during the magma ocean and water ocean epochs respectively and forge new links with observations to gain insight into the behavior of volatiles on the Hadean Earth. As accretion wanes, Earth's magma ocean crystallizes, outgassing the bulk of its volatiles into the primordial atmosphere. The redox state of the magma ocean controls both the chemical composition of the outgassed volatiles and the hydrogen isotopic composition of water oceans that remain after hydrogen escape from the primordial atmosphere. The climate modeling indicates that multi-bar H2-rich atmospheres generate sufficient greenhouse warming and rapid kinetics resulting in ocean-atmosphere H2O-H2 isotopic equilibration. Whereas water condenses and is mostly retained, molecular hydrogen does not condense and can escape, allowing large quantities (∼102 bars) of hydrogen – if present – to be lost from the Earth in this epoch. Because the escaping inventory of H can be comparable to the hydrogen inventory in primordial water oceans, equilibrium deuterium enrichment can be large with a magnitude that depends on the initial atmospheric H2 inventory. With rapid kinetics, the water molecule concentrates deuterium and, to the extent that hydrogen in other forms (e.g., H2) are significant species in the outgassed atmosphere, pronounced D/H enrichments (∼1.5-2x) in the oceans are expected from equilibrium partitioning in this epoch. By contrast, the common view that terrestrial water has a carbonaceous chondritic source requires the oceans to preserve the isotopic composition of that source, undergoing minimal D-enrichment via equilibration with H2 followed by hydrodynamic escape. Such minimal enrichment places upper limits on the amount of primordial atmospheric H2 in contact with Hadean water oceans and implies oxidizing conditions (logfO2>IW+1, H2/H2O < 0.3) for outgassing from the magma ocean. Preservation of an approximate carbonaceous chondrite D/H signature in the oceans thus provides evidence that the observed oxidation of silicate Earth occurred before crystallization of the final magma ocean, yielding a new constraint on the timing of this critical event in Earth history. The seawater-carbonaceous chondrite “match” in D/H (to ∼10-20%) further constrains the prior existence of an atmospheric H2 inventory – of any origin – on post-giant-impact Earth to <20 bars, and suggests that the terrestrial mantle supplied the oxidant for the chemical resorption of metals during terrestrial late accretion.

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.

Pressure peaking phenomenon for indoor hydrogen releases

The pressure peaking phenomenon can be observed when hydrogen is released in enclosures with vent(s). The unforeseen physical phenomena of pressure peaking has been described and explained. This phenomenon occurs for hydrogen releases in enclosures where the vent(s), volume, and leak rate are such that there will be no air ingress to the enclosure. Pressure peaking describes the physical phenomenon of a peak in the pressure transient during such a release for some release conditions in a vented enclosure. This phenomenon is pronounced only for gases lighter than air, e.g. hydrogen and helium. For particular release flow rates and vent sizes the peak can be an order of magnitude higher compared to the steady-state overpressure that is reached when the enclosure is fully filled with hydrogen over time. This finding is relevant to all hydrogen applications indoors from a fuel cell in an enclosure or laboratory scale storage up to a forklift in a warehouse. The peak magnitude depends on the release flow rate, hydrogen inventory, enclosure volume and the ventilation area, and potentially can exceed the maximum pressure which the enclosure can withstand. A look up nomogram for applicability of the developed theory that is based on vent area and leak rate has been created for sustained releases. Experimental evidence of the phenomena is described. Reduced analytical equations are presented for the case of a constant flow rate release, and the associated nomogram is presented for use by hydrogen safety engineers and regulators.

Deflagrations of localised homogeneous and inhomogeneous hydrogen-air mixtures in enclosures

Two original models for use as novel tools for the design of hydrogen-air deflagration mitigation systems for equipment and enclosures are presented. The first model describes deflagrations of localised hydrogen-air mixtures in a closed space such as a pressure vessel or a well-sealed building while the second model defines safety requirements for vented deflagrations of localised mixtures in an enclosure. Examples of localised mixtures include ‘pockets’ of gas within an enclosure as well as stratified gas distributions which are especially relevant to hydrogen releases. The thermodynamic model for closed spaces is validated against experiments available from the literature. This model is used to estimate the maximum hydrogen inventory in a closed space assuming the closed space can withstand a maximum overpressure of 10 kPa without damage (this is typical of many civil structures). The upper limit for hydrogen inventory in a confined space to prevent damage is found to be equivalent to 7.9% of the closed space being filled with 4% hydrogen. If the hydrogen inventory in a closed space is above this upper limit then the explosion has to be mitigated by the venting technique. For the first time an engineering correlation is presented that accounts for the phenomena affecting the overpressure from localised vented deflagrations, i.e. the turbulence generated by the flame front itself, the preferential diffusion in stretched flames, the fractal behaviour of the turbulent flame front surface, the initial flow turbulence in unburnt mixture, and the increase of the flame surface area due to the shape of an enclosure. Validation of the new vented deflagration model developed at Ulster has been carried out against 25 experiments with lean stratified hydrogen-air mixtures performed by the Health and Safety Executive (UK) and Karlsruhe Institute of Technology (Germany).

Reduction of hydrogen content in deuterium plasma with mixed graphite and tungsten divertors in EAST

Reduction of hydrogen content in deuterium-fueled fusion plasmas is important not only to avoid diluting reacting core deuterons but also so as to allow the optimization of hydrogen-minority-heating efficiency in those fusion devices which employ ion-cyclotron-radio-frequency heating systems. In EAST, the amount of hydrogen released from plasma-facing components has been shown to depend strongly on both their composition and their temperature. As measured by thermal desorption spectroscopy, the hydrogen inventory in graphite – used in EAST as lower divertor material – has been determined to be >25 times larger than that of tungsten which comprises the upper divertor. This difference in hydrogen inventory is attributed mostly to the intrinsically porous nature of bulk graphite. Thus the main source of hydrogen release into EAST discharges was identified as the graphite tiles used in the lower divertor. The hydrogen content in EAST plasmas were clearly reduced by first employing a high-temperature vacuum baking of all graphite tiles and then renewing a 100–200 μm thick SiC coating before an EAST experimental run campaign. Subsequent active surface conditioning of all wall components with elemental silicon and then with elemental lithium were seem to again reduce the plasma hydrogen content significantly – with lithium proving to be more effective than silicon. Combining these several techniques, H/(H + D) levels as low as ∼3% have been achieved in EAST discharges.Additionally, the effects of lithium thickness on H surface implantation and retention has been re-examined semi-quantitatively using data from a previous run campaign. These data suggest that relatively thick Li films coated on the first wall can effectively isolate the rich source of hydrogen stored in the porous bulk of the underlying graphite from the deuterium-fueled plasma so as to minimize hydrogen release.Finally an operational maneuver whereby a diverted plasma is repetitively switched from an upper single null configuration to a lower single null configuration is presented. This switching maneuver has been shown to suppress hydrogen influx into a 35s-long EAST discharge by alternately mitigating the rise in divertor temperature.

Influence of near-surface blisters on deuterium transport in tungsten

The effect of near-surface blisters on deuterium transport in tungsten is studied by means of nuclear reaction analysis (NRA) and scanning electron microscopy (SEM). Gentle deuterium plasma loading of different durations and subsequent NRA depth profiling is performed in heavily pre-blistered and unblistered areas on self-damaged tungsten samples. Comparison of the deuterium depth profiles reveals a considerable reduction of the deuterium transport into the bulk due to the presence of near-surface blisters. SEM and NRA results identify the enhanced re-emission of deuterium from the sample due to open blisters as the underlying mechanism, which reduces the deuterium flux into the bulk. Based on a simple analytical hydrogen retention model, the re-emitted deuterium flux by open blisters is determined to be 80% of the implanted deuterium flux in the present conducted experiment. In addition, the deuterium flux into the bulk is reduced by 60% compared to the unblistered case. Hence the presence of blisters is not a general disadvantage in the context of retention, but can be beneficial in slowing down the build up of a certain hydrogen inventory and in reducing the permeation flux.

Hydrogen inventory control for vanadium by Ti metal powder mixing in molten salt FLiNaK

Titanium powder mixed molten salt FLiNaK, which has larger hydrogen solubility than that pure FLiNaK, was investigated for its capability to mitigate hydrogen inventory in vanadium, in expectation of molten salt/vanadium alloy liquid blanket. The hydrogen fluence from gas to vanadium plate through molten salt containing μm- and nm- size Ti powder was quantified as hydrogen inventory in the vanadium plate. The experiment was performed at 823K, feeding hydrogen gas for 10–1000Pa. FLiNaK containing nm-size Ti powder showed less hydrogen inventory than pure one, whereas μm-size Ti powder showed less difference. nmTi-FLiNaK was found to be an effective buffer for hydrogen transfer.

Predicting hydrogen isotope inventory in plasma-facing components during normal and abnormal operations in fusion devices

Hydrogen isotope behavior and inventory in plasma-facing components (PFCs) of fusion devices are key concerns for safe, reliable, and economical operation. To accurately estimate hydrogen isotope retention and recovery in tungsten (the current leading candidate as a PFC), we have developed a model that was recently benchmarked against isotope depth profile and retention level in a tungsten target under various conditions and compared with both experimental data and simulation results. In this research, we have extended the model to include details of transient events. Therefore, one can use this model to estimate hydrogen isotope retention behavior in tungsten and potential other PFC candidates during normal operational pulse, effects of edge-localized modes (ELMs), and a possible cleaning processes scenario.