The effect of hydrogen isotopes and helium on tritium diffusion and extraction from candidate fusion breeder blanket ceramics

在未来的核聚变电站中，放射性燃料氚将在聚变堆芯（增殖包层）周围的区域中产生（增殖），世界各地正在开发固体和液体氚增殖设计。氚增殖材料将包括元素锂，其可以吸收聚变中子并转化为氚和氦（嬗变）。在谢菲尔德大学，正在研制固体增殖材料，并在与聚变有关的环境中进行试验。大多数固体增殖剂是多晶陶瓷，特别是含锂陶瓷，例如偏钛酸锂（Li 2 TiO 3），气态氚将通过其扩散并被提取。先前的工作已经发现陶瓷晶粒尺寸和有效的氚扩散和提取之间的直接相关性，以及陶瓷抵抗/恢复聚变中子辐照引起的损伤的能力。在我们以前的工作中，我们发现Li 2 TiO 3包含小的空位型缺陷，其在熔融相关温度下生长。这些空位型缺陷和氦产生的嬗变有可能捕获氚，因为它通过材料扩散，并且如果Li 2 TiO 3是增殖包层材料的有力竞争者，则必须确定这种捕获的程度。因此，这个博士项目的重点是确定候选含锂陶瓷固有的缺陷以及氦如何影响抗辐射损伤性和氚扩散和提取。

In the fusion power stations of the future, the radioactive fuel tritium will be produced (bred) in a region surrounding the fusion core (the breeder blanket), with both solid and liquid tritium breeder designs being developed around the world. The tritium breeding material will comprise the element lithium, which can absorb fusion neutrons and transform into tritium and helium (transmutation). At the University of Sheffield, solid breeder materials are being developed and tested in fusion-relevant environments. Most solid breeders are poly-crystalline ceramics, specifically lithium-containing ceramics such as lithium metatitanate (Li2TiO3), through which the gaseous tritium will diffuse and be extracted. Previous work has found direct correlations between ceramic grain size and efficient tritium diffusion and extraction, as well as the ceramics ability to resist/recover from fusion neutron irradiation induced damage. In our previous work we found that Li2TiO3 contains small vacancy-type defects which grow at fusion relevant temperatures. These vacancy-type defects and the helium generated transmutation have the potential to trap tritium as it diffuses through the material, and the extent of this trapping must be determined if Li2TiO3 is to be a serious contender for a breeder blanket material. Therefore, the focus of this PhD project is to determine how defects, intrinsic to candidate Li-containing ceramics, as well as helium, impact radiation damage resistance and tritium diffusion and extraction.