Macroscopic rate equation modeling of trapping/detrapping of hydrogen isotopes in tungsten materials

Abstract

International audienceCode development to solve numerically the model equations of diffusion and trapping of hydrogen in metals. Parametrization of the model trapping parameters (detrapping energies and density): fitting of experimental TDS spectrum. Confrontation model/experiment: evolution of retention with fluence and implantation temperature. Investigation of period of rest between implantation and TDS on retention and depth profile. a b s t r a c t Relevant parameters for trapping of Hydrogen Isotopes (HIs) in polycrystalline tungsten are determined with the MHIMS code (Migration of Hydrogen Isotopes in MaterialS) which is used to reproduce Thermal Desorption Spectrometry experiments. Three types of traps are found: two intrinsic traps (detrapping energy of 0.87 eV and 1.00 eV) and one extrinsic trap created by ion irradiation (detrapping energy of 1.50 eV). Then MHIMS is used to simulate HIs retention at different fluences and different implantation temperatures. Simulation results agree well with experimental data. It is shown that at 300 K the retention is limited by diffusion in the bulk. For implantation temperatures above 500 K, the retention is limited by trap creation processes. Above 600 K, the retention drops by two orders of magnitude as compared to the retention at 300 K. With the determined detrapping energies, HIs outgassing at room temperature is predicted. After ions implantation at 300 K, 45% of the initial retention is lost to vacuum in 300 000 s while during this time the remaining trapped HIs diffuse twice as deep into the bulk

Dynamic fuel retention in tokamak wall materials: An in situ laboratory study of deuterium release from polycrystalline tungsten at room temperature

“…A modification of our experimental setup is planned in order to address precisely this point. We believe that our experimental results demonstrate the importance of deuterium trapping on natural defects of tungsten and we expect that this would help to rationalize the physical mechanism behind the law at 300 K [19,31,32] and would allow safer extrapolation of the tritium wall inventory for ITER.…”

Retention and release of hydrogen isotopes in tungsten plasma-facing components: the role of grain boundaries and the native oxide layer from a joint experiment-simulation integrated approach

“…One-dimensional (1D) MRE codes are frequently used for extracting energetic information about the interaction of PFC materials with ion beams and plasmas [2,5,13]. We have recently developed such a code, MHIMS (for migration of hydrogen isotopes in materials) [4], which describes numerous elementary steps encountered in real experiments. With MHIMS, one can simulate the implantation of hydrogen isotopes below the surface with their subsequent diffusion into the bulk or toward the surface and their trapping on bulk defects.…”

“…Secondly, we give an overview of the experimentally explored parameter space. Then we present the MRE codes MHIMS [4] and MHIMS-Reservoir [9] which are used to construct tungsten wall models that will be tested on the experimental results. In section 3, we first elaborate on the parametrization of the MHIMS code, mostly on experimental inputs, and we estimate how far the model is able to reproduce experimental observations and draw conclusions on its achievements and failures.…”

Object kinetic Monte Carlo simulations of irradiated tungsten for nuclear fusion reactors

“…Hodille et al [188] reported that H atoms should be retained in three different types of traps, with binding energies of 0.83, 1.0 and 1.5 eV between 300 and 700 K. This is in good agreement with the results presented in this Chapter, as the simulations reveal that the main trapping of H atoms is in monovacancies, from H 5 V 1 to H 1 V 1 . The values of the traps proposed by Hodille et al [188] can be assimilated to those used in the simulations presented in this Chapter, as can be seen in the comparison shown in …”

“…The values of the traps proposed by Hodille et al [188] can be assimilated to those used in the simulations presented in this Chapter, as can be seen in the comparison shown in …”