柱状晶钨中晶界对氘滞留与起泡行为的影响研究

The realization of the future commercial fusion reactor depends strongly on the self-sufficiency of tritium. Tritium retention and blistering in fusion wall material will increase the inventory of tritium in materials, thus affect tritium self-sufficiency. This is one of the key material issues of building a commercial fusion reactor. Tungsten is the most promising candidate for the wall material in fusion devices due to the low tritium retention in tungsten. Grain boundary is an important factor when considering hydrogen isotopes (deuterium and tritium) transportation in tungsten. It could not only serve as a trap site, but also as a migration channel to affect hydrogen diffusivity. At present, researches on the effect of grain boundary on tritium retention and blistering in tungsten are quite limited, resulting in a poor understanding of the grain boundary effect on irradiation damage and hydrogen transportation. In this project columnar grain tungsten samples with different grain boundary parameters will be exposed to high flux deuterium plasma. Combined with calculation and simulation, the effect of grain boundary on irradiation defects, deuterium retention and blistering will be studied to reveal related mechanisms. This will provide a guideline for the mitigation of tritium retention based on the material design with consideration of grain boundary.

未来商业聚变电站的实现极大依赖于电站自身能否持续产生足量的氚燃料（即氚自持）。聚变堆壁材料中氚滞留及起泡将增加材料中氚的残存量，严重影响氚自持过程，是关乎聚变电站商业化的关键材料问题之一。钨材料由于具有低氚滞留特性，是聚变装置壁材料的首要候选材料。晶界是影响钨中氢同位素（氘、氚）输运的关键因素，可作为捕获位捕获氢，也可作为输运通道改变氢扩散。目前关于晶界对钨中氢滞留及表面起泡行为影响的研究较少，对等离子体辐照条件下晶界参数对辐照损伤缺陷状态与氢输运行为的影响规律及机理缺乏清晰、系统的认识。本项目采用具有不同晶界参数的柱状晶钨，开展氘等离子体辐照实验，结合计算模拟研究方法，系统研究柱状晶钨中辐照缺陷状态、氘滞留行为与表面起泡行为随晶界参数的变化规律，阐明晶界参数对等离子体辐照损伤缺陷、氢滞留的影响规律及机理。从基于晶界特性的材料设计出发，为寻找抑制氚滞留的有效方法提供参考和依据。

限制聚变能商业应用的瓶颈之一是如何维持聚变燃料氚的循环利用（氚自持），壁材料中氢同位素滞留可显著影响自持过程中氚的回收。针对聚变装置对氚自持与氚滞留行为研究需求，本项目采用直线等离子体装置在实验室复现托卡马克聚变装置边界辐照条件，使用柱状晶钨等多种类型材料开展辐照实验，研究了氢致起泡、氢滞留等典型材料辐照损伤行为，从而揭示了晶界特征对辐照损伤行为的影响与机制。研究结果表明：柱状晶钨中氢致起泡密度与氢滞留量均低于其他类型材料，同时低晶界密度的柱状晶钨性能略优于高晶界密度；柱状晶钨所具有的晶界面与表面平行的几何构型具有显著抑制氢致起泡生长的作用，同时柱状晶钨所具有的（001）择优取向晶面也具有抗氢致起泡特性；根据氢致起泡诱导缺陷主导的氢滞留机制，由此给出了柱状晶钨在抗氢致起泡和与低氢滞留行作用机理。项目研究成果为深入理解聚变堆钨基壁材料在等离子体辐照下的缺陷/微结构演化、氘滞留行为及微观机制奠定了基础，所提出的钨中氢滞留机制为理解未来聚变装置中氢同位素滞留规律、开发先进低氢滞留钨材料提供了实验依据。