Speaker
Description
The trapping of helium in crystal defects in tungsten is one of the mechanisms of bubble nucleation. Due to its low solubility and high mobility, helium tends to accumulate by self-trapping or trapping in defect sites such as dislocations, grain boundaries, and vacancies, leading to bubble formation. When these bubbles come close enough, they can coalesce and form large bubbles. Large bubbles near the surface can burst due to their internal pressure and cause changes in the surface of the material [1]. These phenomena have been extensively studied at the atomic scale by molecular dynamics, both for bubble formation along dislocations [2] and for bubble coalescence [3].
In this work, we propose a model of cluster dynamics in a one-dimensional continuous medium describing the formation of helium bubbles by trap mutation as well as by nucleation at dislocations and vacancies. This model, extended from [4], is implemented in FEniCSx [5] and it includes bubble depletion model depending on the bubble distance from the surface and bubble coalescence model. The analysis revealed the influence of helium trapping and bubble nucleation at dislocations and preexisting vacancies on bubble concentration and size. Several hypotheses are considered regarding the evolution of dislocation densities, such as their annihilation during bubble nucleation and their creation during growth. The results obtained were compared with experimental observations (radius size, porosity and growth kinetic) from literature [1,6,7].
The project leading to this publication has received funding from the ANR under Grant No ANR-23-CE08-0026-04 (HEBUTERNE). This work has also been carried out within the framework of the EUROfusion Consortium, funded by the European Union via the Euratom Research and Training Programme (Grant Agreement No 101052200—EUROfusion).
[1] Ialovega et al. Nuclear Fusion, 62(2022)126022
[2] Wang et al. Comput. Mater. Sci. 230 (2023) 112457
[3] Zhan et al. Comput. Mater. Sci. 187 (2021) 110076
[4] Delaporte-Mathurin et al. Sci. Rep. 11 (2021) 14681
[5] I. A. Baratta et al. preprint (2023) see https://fenicsproject.org
[6] Corso et al. Nucl. Mater. Energy (2025)101894
[7] Pappalardo et al. submitted to J. Phys. D: Appl. Phys. (2025)