Advanced shielding materials to enable compact fusion reactors

为太阳提供动力的过程可以作为清洁和安全的聚变能源加以利用。核聚变的进展可以通过缩小反应堆的尺寸和成本来加速，英国政府最近宣布投入2.2亿英镑开发这种小型反应堆。然而，为了使它们连续运行几十年，反应堆的某些部分必须与高能粒子屏蔽。使用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。我的工作计划将开发更有效的屏蔽材料，使这些反应堆能够持续运行。传统的屏蔽使用重原子，它反射较轻的粒子;类似于乒乓球如何从斯诺克球上反弹回来。我的研究是基于一种混合方法，将较重的元素与较轻的元素结合起来，吸收并耗散粒子的能量;现在想想同样重量的球碰撞，就像斯诺克中的一个突破。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为现实。在此过程中，我将与英国领先的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，这两家公司都希望在未来10-20年内建造能产生能量的反应堆。因为它们非常坚硬，不容易融化，我将使用类似的方法来制造其他坚硬的材料，例如家用钻头。这些是通过在高温下将粉末压缩在一起，使粉末熔融形成固体材料而制成的。我将测试材料的性能，比如强度。作为其中的一部分，我将试图了解材料中原子的几何排列-所谓的“微观结构”-如何影响这些性质。第二个目标将是了解这些材料如何在聚变反应堆的环境中降解。它们将受到极端的加热，在反应堆的某些区域，这与火箭发动机的情况类似。我将测试材料的机械强度如何在这些温度下下降，就像钢铁在铁匠的熔炉中软化，变得有韧性。与此同时，这些材料也将在反应堆中受到高能粒子的轰击。这往往会打乱原子的排列，使材料更脆;就像你前后弯曲回形针，它最终会折断。为了验证这一点，我将使用专业的粒子束设备来模拟破坏过程。因为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），我将使用高倍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机械测试，以了解混乱对强度的影响。为了解释这些测试，我将与计算机建模专家合作，他们可以模拟单个的“原子跳跃”，以确定哪种跳跃是造成损害的原因。该奖学金的最终目的是优化材料的原子排列，以提高其损伤容限。为了实现这一点，我将工程材料的积木，首先添加一个水泥样层之间的块，其次是通过扁平的块像煎饼。这种工程学在自然界中随处可见，海螺的外壳是由相对易碎的白垩状陶瓷层薄薄地堆叠而成的，其间有一种粘性物质。所以，当蜗牛壳被捕食者袭击时，裂缝要么在胶水中停止，要么在白垩层之间偏转，蜗牛生存了下来。通过采用这种方法，我的工作将使核聚变发电厂中的材料能够承受更极端的环境，从而使它们能够运行更长时间，这反过来又会降低核聚变能源的成本。

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.