Advanced shielding materials to enable compact fusion reactors

为太阳能供电的过程可以作为清洁和安全的聚变能源来利用。核聚变的进展可以通过缩小反应堆的尺寸和成本来加速，英国政府最近宣布了2.2亿GB来开发这种较小的反应堆。然而，为了让它们连续运行几十年，反应堆的某些部分必须屏蔽高能粒子。以目前可用的屏蔽材料，这些部件将在几周或几个月内开始降解。我的工作方案将开发更有效的屏蔽材料，使这些反应堆能够持续运行。传统的防护罩使用重原子，反射较轻的粒子；类似于乒乓球从斯诺克球上反弹的方式。我的研究基于一种混合方法，将较重的元素与较轻的元素结合起来，相反地吸收和耗散粒子的能量；现在想想类似重量的球碰撞，就像斯诺克的破发一样。这种方法已经在理论上得到了证明，但我现在必须通过制造和测试真实的工程材料来将其变成现实。在这样做的过程中，我将与英国领先的核聚变工程公司托卡马克能源公司和英国原子能管理局密切合作，这两家公司都寻求在未来10-20年内建造产生能源的反应堆。我的首要目标是制造这些材料。因为它们非常硬，不容易融化，我将使用类似于其他硬材料的制造方法，例如家用钻头中的那些。它们是通过在高温下将粉末压缩在一起，使粉末熔化形成固体材料制成的。我要测试这些材料的性能，比如它们的强度。作为这项研究的一部分，我将试图了解材料中原子的几何排列--所谓的“微结构”--如何影响这些性质。第二个目标是了解这些材料在聚变反应堆环境中是如何降解的。它们将受到极端加热，在反应堆的某些区域，这类似于火箭发动机所经历的情况。我将测试这种材料的机械强度在这些温度下是如何退化的，就像钢在铁匠炉中被软化以变得可塑一样。同时，反应堆中的材料也会受到高能粒子的轰击。这往往会使原子的排列变得混乱，从而使材料变得更脆；同样，当你来回弯曲回形针时，它最终会折断。为了测试这一点，我将使用专业的粒子束设备来模拟损坏过程。由于损伤只发生在很小的范围内(大约是人类头发厚度的十分之一)，我将使用非常高倍数的显微镜来观察混乱的过程。我还将对受损区域进行小规模的力学测试，以了解混杂在一起对力量的影响。为了解释这些测试，我将与计算机建模专家合作，他们可以模拟个别的“原子跳跃”，以计算出哪种跳跃是造成损害的原因。该奖学金的最终目标是优化材料的原子排列，以提高其损伤容忍度。为了实现这一点，我将设计材料的积木，首先在积木之间添加一层类似水泥的层，然后将积木像煎饼一样压平。这样的工程是在自然界中发现的，海螺壳是由相对易碎的白垩状陶瓷薄层堆叠而成，中间夹杂着一种粘性物质。因此，当贝壳被捕食者击中时，裂缝要么停止在胶水中，要么在白垩层之间偏转，蜗牛活了下来。通过引入这种方法，我的工作将使聚变发电厂中的材料能够承受更极端的环境，从而使它们能够更长时间地运行，这反过来将降低聚变能源的成本。

The process powering the sun can be harnessed as clean and safe fusion energy. Progress in fusion could be accelerated by shrinking the size and cost of reactors and the UK Government has recently announced £220 million to develop such smaller reactors. However, for them to operate continuously for several decades, certain parts of the reactor must be shielded from high energy particles. With currently available shielding materials, these parts will begin to degrade within a matter of weeks or months. My programme of work will develop more efficient shielding materials so that these reactors can operate on a continual basis. Conventional shields use heavy atoms, which reflect the lighter particles; similar to how a ping-pong ball might bounce back off a snooker ball. My research is based on a hybrid approach, combining heavier elements with lighter ones, which instead absorb and dissipate the particle's energy; think now of similarly weighted balls colliding, like a break in snooker. The approach has been proven in theory, but I must now turn this into reality by fabricating and testing real engineering materials. In doing so I will work closely with the UK's leading fusion engineering company, Tokamak Energy, and the UK Atomic Energy Authority, both of whom seek to build energy-producing reactors within the next 10-20 years.My first aim is to fabricate these materials. Because they are very hard and do not melt easily, I will use similar methods to the way other hard materials are made, such as those within a household drill-bit. These are made by compressing powders together at high temperature so that the powders fuse to form a solid material. I will test the properties of the materials like their strength. As part of this I will seek to understand how the geometrical arrangement of the atoms within the material - the so-called "microstructure" - affects these properties. The second aim will be to understand how these materials degrade in the environment of the fusion reactor. They will be subjected to extreme heating, which in some areas of the reactor is similar to what is experienced in a rocket engine. I will test how the material's mechanical strength degrades at these temperatures, just like steel is softened in a blacksmith's furnace to become malleable. At the same time, the materials will also be bombarded by high energy particles in the reactor. This tends to jumble-up the arrangement of the atoms, which can make the materials more brittle; in the same way that when you bend a paperclip back-and forth, it eventually snaps. To test this, I will use specialist particle beam facilities to simulate the damage process. Because the damage only occurs on a small scale (about a tenth the thickness of a human hair) I will use very high-power microscopes to observe the jumbling-up process. I will also perform small-scale mechanical tests on the damaged areas to understand how the jumbling-up effects strength. To interpret these tests, I will work with experts in computer modelling, who can simulate individual "atomic jumps" to work out which sorts of jumps are responsible for the damage. The final aim of the fellowship is to optimise the material's atomic arrangement to improve its damage tolerance. To achieve this, I will engineer the material's building blocks by firstly adding a cement-like layer between blocks, and secondly by flattening the blocks like pancakes. Such engineering is found in nature, where sea-snail shells are built from thinly stacked layers of relatively brittle chalk-like ceramics, with a gluey substance in between. So, when the shell is struck by predators, cracks either stop in the glue, or deflect between the layers of chalk, and the snail survives. By bringing this approach, my work will enable the materials in fusion power plants to withstand even more extreme environments and thus enable them to operate for longer, which will in turn decrease the cost of fusion energy.