Martí Jordi, Mazzanti Ferran, Astrakharchik Grigori E, Batet Lluís, Portos-Amill Laura, Pedreño Borja
Department of Physics, Polytechnic University of Catalonia-Barcelona Tech, 08034 Barcelona, Spain.
Barcelona School of Telecommunications Engineering, Polytechnic University of Catalonia-Barcelona Tech, 08034 Barcelona, Spain.
Materials (Basel). 2022 Apr 13;15(8):2866. doi: 10.3390/ma15082866.
Fusion energy stands out as a promising alternative for a future decarbonised energy system. In order to be sustainable, future fusion nuclear reactors will have to produce their own tritium. In the so-called breeding blanket of a reactor, the neutron bombardment of lithium will produce the desired tritium, but also helium, which can trigger nucleation mechanisms owing to the very low solubility of helium in liquid metals. An understanding of the underlying microscopic processes is important for improving the efficiency, sustainability and reliability of the fusion energy conversion process. The spontaneous creation of helium droplets or bubbles in the liquid metal used as breeding material in some designs may be a serious issue for the performance of the breeding blankets. This phenomenon has yet to be fully studied and understood. This work aims to provide some insight on the behaviour of lithium and helium mixtures at experimentally corresponding operating conditions (843 K and pressures between 108 and 1010 Pa). We report a microscopic study of the thermodynamic, structural and dynamical properties of lithium-helium mixtures, as a first step to the simulation of the environment in a nuclear fusion power plant. We introduce a new microscopic model devised to describe the formation of helium droplets in the thermodynamic range considered. Our model predicts the formation of helium droplets at pressures around 109 Pa, with radii between 1 and 2 Å. The diffusion coefficient of lithium (2 Å2/ps) is in excellent agreement with reference experimental data, whereas the diffusion coefficient of helium is in the range of 1 Å2/ps and tends to decrease as pressure increases.
聚变能源是未来脱碳能源系统中一个很有前景的替代方案。为了实现可持续发展，未来的聚变核反应堆将必须自行生产氚。在反应堆所谓的增殖包层中，锂受到中子轰击会产生所需的氚，但同时也会产生氦，由于氦在液态金属中的溶解度极低，这可能会引发成核机制。了解潜在的微观过程对于提高聚变能量转换过程的效率、可持续性和可靠性非常重要。在某些设计中，用作增殖材料的液态金属中自发形成氦滴或气泡可能会对增殖包层的性能造成严重问题。这一现象尚未得到充分研究和理解。这项工作旨在深入了解锂和氦混合物在实验对应的运行条件（843K和10⁸至10¹⁰Pa之间的压力）下的行为。我们报告了对锂 - 氦混合物的热力学、结构和动力学性质的微观研究，作为模拟核聚变发电厂环境的第一步。我们引入了一个新的微观模型，旨在描述在所考虑的热力学范围内氦滴的形成。我们的模型预测在10⁹Pa左右的压力下会形成氦滴，半径在1至2埃之间。锂的扩散系数（2埃²/皮秒）与参考实验数据高度吻合，而氦的扩散系数在1埃²/皮秒范围内，并且随着压力的增加而趋于减小。
