氦在液态锂中的成核
Nucleation of helium in liquid lithium
摘要：
聚变能源是未来脱碳能源系统的一个有前途的替代方案。为了可持续发展，未来的核聚变反应堆必须自己生产氚。在所谓的反应堆增殖层中，锂的中子轰击将产生所需的氚，但也产生氦，由于氦在液态金属中的溶解度非常低，氦可以触发成核机制。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。在某些设计中用作繁殖材料的液态金属中自发产生氦滴或气泡可能是繁殖毯性能的严重问题。这一现象尚待充分研究和理解。这项工作的目的是提供一些洞察力的锂和氦的混合物在实验相应的操作条件下（843 K和0.1和7 GPa之间的压力）的行为。我们报告的热力学，结构和动力学性质的锂-氦混合物的微观研究，作为第一步，在核聚变发电厂的环境模拟。我们介绍了一个微观模型，旨在描述形成的氦滴在热力学范围内考虑。当压力增加到0.175 GPa以上时，观察到从可混溶的均匀混合物到相分离的混合物的过渡，其中氦滴成核。锂的扩散系数（2 μ 2 /ps）与参考实验数据非常一致，而氦的扩散系数在1 μ 2 /ps的范围内，并且随着压力的增加而趋于减小。已发现氦滴的半径在1到2 μ m之间。
英文摘要：
Fusion energy stands out as a promising alternative for a future decarbonised energy system. 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. A spontaneous creation of helium drops 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 behavior of lithium and helium mixtures at experimentally corresponding operating conditions (843 K and pressures between 0.1 and 7 GPa). 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 microscopic model devised to describe the formation of helium drops in the thermodynamic range considered. A transition from a miscible homogeneous mixture to a phase-separated one, in which helium drops are nucleated, is observed as the pressure is increased above 0.175 GPa. The diffusion coefficient of lithium (2 Å 2 /ps) is in excellent agreement with reference experimental data, whereas the diffusion coefficient of helium is in the range of 1 Å 2 /ps and tends to decrease as pressure increases. The radii of helium drops have been found to be between 1 and 2 Å.
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