The effects of nuclear fusion plasma excursions on the performance of Eurofer-97 components

聚变反应堆内的高工作温度和核辐射会显著改变其部件的微观结构，进而改变材料特性和机械行为。为聚变反应堆选择的材料是专门为减少诱导辐射量而设计的，但了解此类材料在聚变等离子体高温下的表现也很重要。Eurofer-97是一种低活性铁素体-马氏体钢，建议用于热核实验堆和示范聚变反应堆内的许多结构和冷却部件，包括水冷锂铅增殖堆包层中的覆层材料和冷却剂管道，这是热核实验堆正在试验的四种冷却机制之一。使用冷却系统发电是实现核聚变发电商业化的关键一步。DEMO上的等离子体预计在1亿摄氏度左右，使用聚焦磁场进行遏制。界面分析中心(IAC)的初步工作表明，即使是几个小时的高温(-1s 0℃)暴露也会导致用于结构支撑和冷却管道的Eurofer-97不锈钢材料的组织结构显著退化。这可能会影响机械性能和耐腐蚀性，进而导致部件寿命缩短。这个博士项目将研究非常短期的热漂移的影响，并评估它们对材料微观结构和腐蚀行为的影响。学生将使用COMSOL软件包的高级计算模型来探索等离子体漂移引起的热瞬变对反应堆内部件温度的影响。然后将这些温度行为输入ABAQUS，以研究重复热循环对部件应力的结构完整性影响。同时，利用Matcalc等相化学软件研究了反复热漂移对显微组织的影响。学生将使用这些模拟结果的组合来预测组件对蠕变和腐蚀等退化机制的抵抗力，作为它们接近热偏移位置的一个因素。在计算工作的同时，学生将建立在布里斯托尔现有的实验研究基础上，研究Eurofer-97在重复短期热暴露后的行为。这将包括设计短期热处理的实验。然后，将使用扫描和透射电子显微镜、X射线衍射和断层扫描对暴露的样品进行表征，以观察随着热暴露增加钢的结构的变化，并确定是否发生任何脆化或机械性能变化，如果在聚变反应堆中使用，可能会导致问题。也可能有机会将这项工作与辐射和/或腐蚀的影响相结合。该项目是一种多技术方法，以了解聚变动力的重要材料的结构完整性。学生将有机会学习如何使用先进的模拟包和表征技术，并将与UKAEA和NNL的行业合作伙伴密切合作。

The high operating temperatures and nuclear radiation within a fusion reactor can significantly change the microstructure of its components, which in turn can change the material properties and mechanical behaviour . The materials chosen for fusion reactors have been specifically engineered to reduce the amount of induced radiation, but it is also important to understand how such materials will behave when exposed to the high temperatures of the fusion plasma.Eurofer-97 is a reduced-activation ferritic-martensitic steel that is proposed for many of the structural and cooling components within the ITER and DEMO fusion reactors, including the cladding material and coolant pipes in the water-cooled lithium-lead breeder blanket, one of four cooling mechanisms being trialled at ITER. Generating power using a cooling system is a key step in achieving commercialisation of nuclear fusion power generation. The plasma at DEMO is expected to be around 100 million C, using focused magnetic fields for containment. However, in the event of a loss of this containment it is possible for the plasma to contact with wall, leading to dramatic increases in temperature over short timeframes.Preliminary work in the Interface Analysis Centre (IAC), has shown that even a few hours of high temperature (- 1s 0 C) exposure can cause significant microstructural degradation of the Eurofer-97 stainless steel material used for structural support and cooling pipes. This could affect mechanical properties and corrosion resistance, in turn leading to a shortening of component life. This PhD project will study the effect of very short-term thermal excursions and assess their effect on the microstructure and corrosion behaviour of the material.The student will use advanced computational modelling using the software package Comsol to explore the effect of thermal transients due to plasma excursions on the temperatures of components within the reactor. This temperature behaviour will then be input into Abaqus to investigate the structural integrity implications of repeated thermal cycling on component stress. Meanwhile, the impact of repeated thermal excursions on the microstructure will be explored using phase chemistry software such as Matcalc. The student will use a combination of these simulations results to predict the resistance of components to degradation mechanisms such as creep and corrosion as a factor of their proximity to thermal excursion locations.In parallel with the computational work, the student will build on existing experimental research at Bristol studying the behaviour of Eurofer-97 after repeated short-term thermal exposure. This will include design of experiments for short-term thermal treatments. Exposed specimens will then be characterised using scanning and transmission electron microscopy, x-ray diffraction and tomography to observe the change in the steel's structure with increasing heat exposure and determine if any embrittlement or change in mechanical properties occur that might cause problems if used in a fusion reactor. There may also be opportunities to combine this work with the effects of irradiation and/or corrosion.This project is a multi-technique approach to understand the structural integrity of an importar:,t material for fusion power. The student will have the opportunity to learn how to use advanced simulation packages and characterisation techniques, and will work closely with industry partners at the UKAEA and NNL.