Molecular dynamics simulations of cascade overlap with Void/Helium bubble

• Published in: Nuclear materials and energy 2022-09, Vol.32, p.101232, Article 101232
• Main Authors: Cui, Jiechao, Hou, Qing, Li, Min, Qiu, Mingjie
• Format: Article
• Language: English
• Subjects: Cascade damage; Helium bubble; Molecular dynamics; Tungsten; Void
• ISSN: 2352-1791; 2352-1791
• DOI: 10.1016/j.nme.2022.101232

•Bubbles with He/V values between 1 and 2 inhibit defect formation.•The relationship between the evolution of the stress field and the cascade was systemically analyzed.•Two mechanisms for generating dislocation loops were identified. When tungsten (W) is used as a plasma-facing material in fusion reactors, it will suffer irradiation from the high-energy neutron and high-flux low-energy helium (He) plasma, affording voids and He bubbles with varying helium-to-vacancy ratios (He/V). With the accumulation of irradiation dose, an energetic neutron is very likely to trigger collision cascades close to the pre-existing voids/He bubbles. Therefore, in this study, we ran systematic molecular dynamics simulations of the cascades that overlapped with voids/He bubbles in W. We investigated the relationship between the evolution of the stress field and defect formation. Cascades overlapping with the bubbles with He/V values between 1 and 2 produced the least defects; alternatively, other bubbles could facilitate defect formation. Furthermore, two mechanisms for generating dislocation loops, the cascade-destruction and the over-pressured bubble-assist types, were identified and can be attributed to subcascade formation. When there are voids or under-pressured bubbles, the cascade-destruction mechanism can yield vacancy-type dislocation loops; however, the existence of He atoms can inhibit this behavior. In contrast, when the bubbles are over-pressured, the bubble-assist mechanism can contribute to the formation of self-interstitial atom-type dislocation loops. This study helps to improve our understanding of radiation damage in a complicated environment in experiments with multiple irradiations or fusion reactors.