Modelling tritium adsorption and desorption from tungsten dust particles with a surface kinetic model

Abstract

A kinetic surface model is presented and used to explain the loading and desorption kinetics of tritium retained in micrometre-sized tungsten (W) dust particles. The model describes the sticking of hydrogen isotopes from the gas phase to W surfaces and the desorption from W surfaces. The initial sticking coefficient is set to one and independent of the temperature. The activation energy for desorption depends on the hydrogen coverage of the surface and is parametrised with density functional theory (DFT) calculations for W(100), W(110) and W(111) surfaces. The DFT-parametrised model is successfully compared to experimental results showing that the amount of measured tritium as well as the desorption kinetic can be modelled with only tritium adsorbed on the surface of W dust particles. Then, the model is used to explore possible scenarios to remove the tritium from the W surfaces by exposing the tritiated surfaces to either deuterium and hydrogen. The simulations suggest that it can be possible to remove all the tritium trapped on the W surfaces even at room temperature as soon as the hydrogen or deuterium pressure is higher than the tritium pressure. This gives opportunity to build tritium removal scenarios for ITER.

Hydrogen and oxygen on tungsten (110) surface: adsorption, absorption and desorption investigated by density functional theory

“…It follows that many experimental activities are led in laboratories to achieve a full understanding of hydrogen-tungsten interactions and their impact on the operation of the machine [4]. Surface effects were recently shown to play a significant role in absorption and release of hydrogen from tungsten, and models based on macroscopic rate equations (MRE) have emerged [5][6][7][8][9][10]. As often, these models are based on density functional theory (DFT) data that provide the required activation energies to the MRE models.…”

Elliptic Curve-Based Query Authentication Protocol for IoT Devices Aided by Blockchain

“…The proposes authentication mechanism can be applied on a wide range of domains. In practical applications for different disciplines, such as, nano or microstructured sur-face, the security of data and information systems involving different sensors can be ensured for applications in computational physics, such as [ 38 ] or [ 39 ].…”

Deuterium uptake, desorption and sputtering from W(110) surface covered with oxygen

“…DFT calculations [17,20] and experiments [10,23,42] suggest that the desorption energy of H from the W(110) surface depends on the H surface coverage. This dependency has already been implemented in rate equation models by using a continuous function E des (θ D ) [15,24,[43][44][45]. In MHIMS, this function had initially the form of a Fermi-Dirac distribution [24].…”

“…In equation ( 9), E FD (θ D ) is the part already shown in [15,24] and the second part is the exponential decrease where α (dimensionless) indicates the amplitude of the drop of E des and β (dimensionless) indicate how fast it drops. This oversaturation of H revealed at the W(110) surface by DFT can be created by H diffusion on the surface or from the bulk to the surface.…”

“…It is thus important to accurately model this interaction of H with the surface to have a good estimation of the overall fuel retention. In order to describe more accurately the different processes at the surface, recent rate equation models [10][11][12][13][14][15] started to use the kinetic surface model based on Pick and Sonnenberg model [16] which describes the different transition rates from the sub-surface to the surface and the recombination process. This model can straightforwardly introduce the energetics of the surface processes calculated by DFT [17][18][19][20] which allows a comparison of the DFT energetics with experimental TDS data.…”