Development of Advanced Ceramic Breeder Materials for Fusion Energy

用于聚变能的先进陶瓷增殖材料的开发

• 批准号: EP/R006288/1
• 负责人: Samuel Thomas Murphy
• 金额: $ 12.86万
• 依托单位: Lancaster University
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2018
• 资助国家: 英国
• 起止时间: 2018 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=EP%2FR006288%2F1
• 关键词: Development; Advanced; Ceramic; Breeder; Materials

Nuclear fusion offers the promise of abundant, clean, low cost energy. The fusion process involves fusing together two nuclei releasing large amounts of energy that can be harnessed for electricity generation. Future power stations will employ the reaction between two isotopes of hydrogen, tritium and deuterium, creating a helium atom and a neutron. Deuterium is available from seawater, however, tritium does not occur naturally due to its short half-life. Therefore, tritium will be created, or bred, in the reactor from lithium in a process called transmutation. Transmutation will occur immediately outside the main chamber of the reactor, in a region called the breeder blanket. One of the leading breeder blanket designs will use lithium containing pebbles, such as lithium metatitanate and lithium orthosilicate. Solid breeder materials are attractive as they have high lithium densities that will ensure excellent tritium production and their low reactivity with other reactor materials means they are safe. However the use of a solid breeder material means that following transmutation the tritium will be trapped in the pebbles and must be extracted from the crystal. For recovery the tritium must diffuse to the pebble surface where it can be carried away by the coolant. The rate at which the tritium can escape from the pebbles is a very important parameter to consider when designing a fusion reactor because if the rate drops too low and tritium is retained in the pebble the fusion reaction will be unsustainable. Therefore, the main goal of this research to understand the process of tritium diffusion in lithium ceramics to design materials that have high tritium release rates. The exact mechanism of tritium release will depend on the microstructure of the host material. All crystals contain defects, such as missing atoms (called vacancies), and these defects can either promote tritium release or act as traps and inhibit it. The types and concentrations of defects in a material depend on the exact conditions (i.e. temperature) and will evolve over time. Therefore, to understand the tritium release process we must first understand the microstructure of the ceramics and what defects are presentPrevious studies of tritium release have adopted a top down approach where experimentally observed tritium release rates under different conditions are used to infer the exact atomic level mechanism responsible. By contrast this proposal adopts a novel bottom up approach that uses advanced electronic structure calculations to build a tritium release model from first principles. A key advantage of this approach is that the calculations provide detailed understanding of the atomic rearrangement processes that constitute tritium diffusion and allow a rate to be determined for each process. Initially the intrinsic defect chemistry of the host materials will be examined. This will allow the identification of the defects present in the ceramic under different conditions. Once the intrinsic defect populations are established the interaction of tritium atoms with the defects will be studied. By examining the bonding between tritium and the defects it is possible to determine exactly where the tritium will sit in the crystal and to identify which defects will act as traps. The information gathered so far considers where tritium will sit in the crystal but it does not provide information about how quickly the tritium can move through the crystal. Therefore, the next step in the process is to understand how tritium hops between the defects available and to determine which types of hop are most likely under certain conditions. Finally, all of this information will be used to create a tritium release model from lithium ceramics. This model will be used to optimise the microstructure of the ceramics to deliver maximum tritium release to ensure the fusion process is sustainable.

核融合提供了丰富，清洁，低成本能源的希望。融合过程涉及将两个核融合在一起，以释放大量的能量，这些能量可用于发电。未来的动力站将采用两个氢，tri和氘的两个同位素之间的反应，从而产生氦原子和一个中子。海水可从海水购买，但是，由于其半衰期短，因此天然不会发生trium。因此，将在称为变异的过程中在锂的反应堆中创建或繁殖tritium。在一个称为育种者毯子的区域内，trans变将立即发生在反应堆的主腔室内。领先的育种毯设计之一将使用含锂的岩石，例如锂锂和矫置锂。固体材料具有很高的锂密度，因此具有吸引力，可以确保出色的trium产生且与其他反应堆材料的反应性低意味着它们是安全的。但是，使用固体材料意味着trans变后，trium将被困在卵石中，必须从晶体中提取。为了恢复，trium必须扩散到卵石表面，冷却液可以将其散开。设计融合反应器时，tri虫可以从卵石中逃脱的速率是一个非常重要的参数，因为如果速率下降得太低并且tritium被保留在卵石中，则融合反应将是不可持续的。因此，这项研究的主要目的是了解锂陶瓷中trif缩扩散的过程，以设计具有较高tri释放速率的材料。 trip释放的确切机制将取决于宿主材料的微观结构。所有晶体都包含缺陷，例如缺失原子（称为空位），这些缺陷可以促进tri骨释放或充当陷阱并抑制它。材料中缺陷的类型和浓度取决于确切条件（即温度），并且会随着时间的流逝而发展。因此，为了了解tri释放过程，我们必须首先了解陶瓷的微观结构，以及在trip释放的前提研究中采用了一种自上而下的方法，在这些方法中，在不同条件下实验观察到的trip释放速率在不同条件下用于推断精确的原子水平机制负责。相比之下，该提案采用了一种新颖的自下而上方法，该方法使用先进的电子结构计算来构建第一原理的tribe释放模型。这种方法的一个关键优点是，计算提供了对构成tripusion扩散的原子重排过程的详细理解，并允许确定每个过程的速率。最初将检查宿主材料的内在缺陷化学。这将允许在不同条件下识别陶瓷中存在的缺陷。一旦建立了内在的缺陷群体，将研究tri虫原子与缺陷的相互作用。通过检查tri骨和缺陷之间的键合，可以准确确定tri虫将位于晶体中的位置，并确定哪些缺陷将充当陷阱。到目前为止，这些信息考虑到了tri骨位于晶体中的位置，但它没有提供有关tri虫可以通过晶体移动的速度的信息。因此，该过程的下一步是了解可用缺陷之间的tri虫如何在某些条件下确定哪种类型的HOP。最后，所有这些信息都将用于创建锂陶瓷的trif释放模型。该模型将用于优化陶瓷的微观结构，以提供最大的tri释放，以确保融合过程可持续。