Numerical Calculation on Recycling Ratio of Tritium from Tungsten Wall Used in Current CFETR Design
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ORIGINAL RESEARCH
Numerical Calculation on Recycling Ratio of Tritium from Tungsten Wall Used in Current CFETR Design Qiang Yan1 • Zhongwen Chen1 • Zhijun Wang1 • Defeng Kong3 • Xiang Wang4 • Fujun Gou1,2 Kun Zhang1,2
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Ó Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract The recycling of tritium from plasma facing wall is an important neutral fuel source (in atomic and molecular form) for plasma confinement and particle control. In this study, the recycling process at tungsten wall based on current CFETR design was modeled. Monte Carlo code SRIM was used to model the implantation of energetic tritium ions into pure tungsten and to get back-scattering fraction of ions and the distribution of implanted tritium ions. The diffusion process of atoms in materials, with recombination at surface as boundary condition, was simulated using numerical approach for both stead and transient state. The total recycling ratio was contributed by fast process (implantation and back scattering) and slow process (diffusion and recombination) and its value nearly equals to 1 for stead state. Temporal dependence of total recycling ratio mainly depended on the slow process and was limited by diffusion coefficient in the bulk near surface and existence of traps in material. For tungsten material with good surface condition, the time of 90% recycling was characterized as 1 ms and affected by temperature, recombination coefficient and concentration of traps while the thickness of material had less affection. Isotope effect that recycling ratio of tritium was larger than that of deuterium at the same situation was also found in the simulation and this effect may affect particle balance and fueling in D-T plasma operation. A collection of theoretical models to estimate the recycling ratio and its time dependence were also summarized and validated by the simulation results. Keywords Wall tritium recycling Tungsten Plasma material interaction Fusion energy
Introduction
& Fujun Gou [email protected] & Kun Zhang [email protected] 1
Institute for Advanced Study, Chengdu University, No.2025, Chengluo Avenue, Chengdu 610106, People’s Republic of China
2
Institute of Nuclear Science and Technology, Sichuan University, Chengdu 610064, People’s Republic of China
3
Institute of Plasma Physics, Chinese Academy of Science, Hefei 230031, People’s Republic of China
4
College of Nuclear Science and Technology, Harbin Engineering University, Harbin 150001, People’s Republic of China
In the extreme environment of fusion device, plasma facing materials (PFM) will suffer the high ion radiation flux (D, T, He), high flux of fast neutrons (14 MeV) and high thermal load. One of the most important challenges in promoting nuclear fusion energy, the ideal ultimate energy resource for human beings in future, is selection and developing materials to be used to construct the controlled fusion devices [1–3]. Experience and lessons gained from the research on PFM used in ITER (Intern
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