MODELLING DUST FORMATION IN A FUSION DEVICE

在聚变反应堆中，燃料（氢同位素）被加热到必须通过极端磁场限制的等离子体状态。然而，约束损失会使反应堆壁暴露在等离子体载荷下，从而造成损坏和灰尘颗粒。粉尘的形成是影响聚变反应堆性能和安全的主要问题。灰尘保留了大量的氢，这会影响反应堆的效率，失去燃料，如果它从墙壁上逸出，就会产生潜在的辐射危害。此外，由于其高化学反应性，在意外失去冷却剂或水的情况下，它可能导致爆炸和损坏容器。虽然尘埃形成的几种机制是众所周知的，例如1)沉积膜部分的断裂和分层，以及2)由于等离子体破坏导致熔融金属（通常是铍）凝固液滴的再活化，但对未来聚变装置材料的选择有必要进行更全面的了解。在这个项目中，我们的目标是建立一个能够模拟和预测沉积层断裂和分层以及再沉积颗粒分层的有限元模型。该模型将使用由等离子体热负荷得出的温度分布来计算产生的应力。使用已知的界面和体积强度和韧性值将使我们能够确定沉积膜何时以及如何破裂和界面脱粘发生，从而模拟粉尘是如何形成的。该模型将用于分析和预测世界上最大的核聚变反应堆ITER中的粉尘形成及其行为，预计将被广泛使用，因此将能够处理其他候选材料和材料混合物，用于未来的反应堆，如DEMO和STEP。该项目将与另一个博士实验项目一起进行，该项目为JET壁的沉积物和熔体液滴的界面特性模拟提供必要的数据，JET壁是ITER之前具有类似特征的原型反应堆。承担该项目的学生将在Culham聚变能中心（CCFE）工作，同时也将成为工程科学领域固体力学和材料工程小组（SMMEG）的成员，并受到两个组织的联合监督。该项目属于EPSRC能源研究领域

In fusion reactors, the fuel (hydrogen isotopes) is heated to the plasma state which must be confined through extreme magnetic fields. However, confinement losses expose the reactor walls to plasma loads that cause damages and dust particles.Dust formation is a major concern for fusion reactors performance and safety. Dust retains significant amounts of hydrogen, which affects the efficiency of the reactors losing fuel and being a potential radiation hazard if it escaped from the walls. Furthermore, due to its high chemical reactivity, it may cause explosions and damage to vessels in the case of an accidental loss of coolant or water.Although several formation mechanisms of dust formation are well-known, such as 1) fracture and delamination of parts of deposited films and 2) remobilisation of solidified droplets of molten metal (usually beryllium) due to plasma disruptions, a more complete understanding is necessary for the choice of materials of future fusion devices. In this project, we aim to develop a finite element model capable of simulating and predicting the fracture and delamination of deposition layers and the delamination of redeposited particles. The model will use temperature distributions derived from the thermal loads of the plasma to calculate the resulting stresses induced. The use of known values of interfacial and bulk strength and toughness will allow us to determine when and how deposition films break and interfacial decohesion occurs, and thus simulate how the dust is formed.The model will be used for the analysis and prediction of dust formation and its behaviour in ITER, the world's largest fusion reactor, with the expectation to be of general usage and as such will be able to tackle other candidate materials and material mixes for future reactors as DEMO and STEP. The project will be performed in conjunction with another PhD experimental project which provides data necessary for the simulations from interfacial properties of deposits and melt droplets of the JET walls, a prototype reactor previous to ITER with similar characteristics.The student undertaking this project will be based at the Culham Centre for Fusion Energy (CCFE) and will also be a member of the Solid Mechanics and Materials Engineering Group (SMMEG) in Engineering Science with joint supervision from both organisations.This project falls within the EPSRC Energy research area