MODELLING DUST FORMATION IN A FUSION DEVICE

点击翻译按钮获取中文摘要

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