Simulation study of helium bubble coalescence in tungsten at various temperatures relevant to fusion conditions

Molecular dynamics (MD) methods are used to study nanosized helium (He) bubble coalescence process in tungsten (W) at various temperatures relevant to fusion conditions, on an atomistic scale. Bubble coalescence in W is observed at a higher temperature and He/V ratio, while the calculated internal bubble pressure due to virial stress increases with the increase in the He/V ratio; bubble coalescence is significantly dependent on the bubble distance. In these MD simulations, coalescence occurs, only when the surface distance between the two bubbles is equal to 1a0, where a0 denotes the lattice constant and is approximately 0.317 nm at 2100 K. On the other hand, a bubble diameter between 1a0 and 3a0 may have relatively limited effect on the coalescence, although larger-sized bubbles may have higher migration energy. Local stress profile calculated indicates that initial bubbles can interact with each other, which may enhance the He atoms diffusion between bubbles and their coalescence. Physical contact at the initial stage of coalescence may occur between two nearby bubbles accompanied by W lattice distortion because of the limited displacement of W atoms near the bubbles and rapid migration of He atoms within the two bubbles. These results are beneficial for understanding the evolution of He bubbles in bulk W

Exploratory tritium breeding performance study on a water cooled lead ceramic breeder blanket for EU DEMO using Serpent-2

Innovative Water cooled Lead Ceramic Breeder (WLCB) blanket concepts are being developed at Karlsruhe Institute of Technology (KIT) to explore alternative options for the European demonstration fusion power plant (DEMO). Compared to the Helium Cooled Pebble Bed blanket (HCPB, which is one of the two driver blanket concepts of the European DEMO), Lead/ Lead-alloy is used as neutron multiplier instead of Be/Be-alloy and pressurized subcooled water is used as coolant instead of Helium in the WLCB. The tritium self-sufficiency is the vital function that a Breeding Blanket has to achieve. The absorption of neutrons by water leads to a decrease in the number of neutrons, so the requirement to improve the tritium breeding capacity of the water-cooled blankets is particularly prominent. The Monte Carlo neutron transport code Serpent-2 developed by VTT in Finland has already been benchmarked to be applicable to neutronics calculations in the fusion reactors in a previous study. In this paper, an exploratory TBR study on Water cooled Lead Ceramic Breeder Blanket is presented

Atomistic study to evaluate interactions between helium bubbles and an edge dislocation

原型炉統合設計・技術検討の一環として実施している低放射化フェライト鋼の研究開発において、核融合環境下における中性子照射効果の予測は原型炉ブランケット開発における最重要課題の１つに位置付けられている。この実現には、既存の代替照射場による材料照射データを理論的に整理し、核融合中性子照射の影響を予測するための方法論の開発が必要となる。本発表では、既存照射場との最も大きな相違であるHe生成量の影響を定量化するため，He原子と結晶欠陥との相互作用を原子レベルの挙動から解析した結果に関して報告した。日本原子力学会　2020年秋の大

Development of Vacuum Vessel Design and Analysis Module for CFETR Integration Design Platform

An integration design platform is under development for the design of the China Fusion Engineering Test Reactor (CFETR). It mainly includes the integration physical design platform and the integration engineering design platform. The integration engineering design platform aims at performing detailed engineering design for each tokamak component (e.g., breeding blanket, divertor, and vacuum vessel). The vacuum vessel design and analysis module is a part of the integration engineering design platform. The main idea of this module is to integrate the popular CAD/CAE software to form a consistent development environment. Specifically, the software OPTIMUS provides the approach to integrate the CAD/CAE software such as CATIA and ANSYS and form a design/analysis workflow for the vacuum vessel module. This design/analysis workflow could automate the process of modeling and finite element (FE) analysis for vacuum vessel. Functions such as sensitivity analysis and optimization of geometric parameters have been provided based on the design/analysis workflow. In addition, data from the model and FE analysis could be easily exchanged among different modules by providing a unifying data structure to maintain the consistency of the global design. This paper describes the strategy and methodology of the workflow in the vacuum vessel module. An example is given as a test of the workflow and functions of the vacuum vessel module. The results indicate that the module is a feasible framework for future application