MAINTAiN - Multi-scAle INTegrity assessment for Advanced high-temperature Nuclear systems

本项目旨在为堆芯核部件在辐照损伤情况下的蠕变变形提供一个预测模型。蠕变变形是材料在名义上高于材料熔点一半的温度下所受载荷作用下的随时间变化的永久变形。蠕变变形对航天、推进、发电等高温环境下工作的工程构件的结构完整性起着至关重要的作用。高温是制约核电站寿命的主要因素之一。这包括聚变反应堆、第四代裂变核反应堆和英国独一无二的先进气冷反应堆。这个项目的背景是核项目。英国的能源结构目前正在并计划继续受益于核能的实质性贡献。此外，英国是世界上唯一在设计、建造和运营高温核电站方面拥有深入知识和知识的国家，其许多结构部件都在蠕变状态下工作。欣克利角、维尔法和摩尔赛德立即新建的反应堆不能在会导致蠕变的温度下工作。然而，聚变反应堆和第四代裂变核反应堆预计将在更高的温度下工作，以提高其热效率，因此它们容易受到蠕变变形和损坏。因此，到目前计划于2050年建造的下一代核电站建成时，英国很有可能失去目前在高温结构完整性方面无与伦比的权威。这项建议的目标之一是通过发展该领域的新知识和新的熟练科学家来保持英国在核工业高温结构完整性方面的领先地位。目前的蠕变工程结构完整性规范是基于在某些标准条件下的试验提取的经验公式。他们忽略了材料的微观结构，而材料的微观结构在发电厂60年的服务中不断演变。辐射损伤是目前工程规范中被忽视的一个重要限制因素，它将对下一代电厂部件的机械响应产生很大影响。因此，我们的目标之一是通过将辐射损伤对材料微观结构的改变包括在材料的本构关系中，从而包括辐射损伤对材料宏观力学响应的影响。为此，我们的主要目标是开发一个可预测的、多尺度的、微观结构信息的蠕变变形模型。该模型从控制高温下位错运动的基本物理方程(位错是材料晶体结构中的缺陷，它们在载荷下的运动占材料永久变形的大部分)到由均匀材料制成的具有复杂几何形状和不同加载历史和条件的工程部件的行为。该模型将帮助工程师预测核反应堆中关键部件的行为，并对它们的服务适宜性做出明智的决策，这是一个关键的安全决策。一旦我们的蠕变模型通过三个微米、细观和宏观长度的实验进行验证和验证，它将为新一代工程结构完整性规范提供基础，该规范基于对材料及其微观结构的机械理解，因此具有预测性，更准确，并且不限于它所基于的测试条件。这将是英国在设计、建造和运营未来核电站方面发挥重要作用的无价资产。

This project aims to provide a predictive model for creep deformation of in-core nuclear components in the presence of irradiation damage. Creep deformation is time-dependent permanent deformation of materials under load nominally at temperatures higher than half the material melting point. Creep deformation plays a crucial role in the structural integrity of engineering components that work at high temperature such as those in aerospace propulsion and energy generation. It is one of the main life limiting factors of nuclear power plants that work at high temperature. This includes fusion reactors, Gen IV fission nuclear reactors, and UK's unique Advanced Gas-cooled Reactors. The context of this project is nuclear. UK's energy mix currently is and planned to continue to benefit from substantive contributions from nuclear. In addition, UK is the only country in the world that has in-depth and knowledge of designing, building, and operating high temperature nuclear power plants with many of its structural components working in the creep regime. The immediate new build reactors at Hinckley Point, Wylfa, and Moorside do not work at temperatures that induce creep. However, fusion reactors and Gen IV fission nuclear reactors are envisaged to be working at much higher temperatures to increase their thermal efficiency and as such they are susceptible to creep deformation and damage. Therefore, there is a high risk that UK loses its current unrivalled authority on high temperature structural integrity by the time the next generation of nuclear power plants are built, currently planned for 2050. One of the objectives of this proposal is to maintain UK lead in high temperature structural integrity of nuclear industry by developing new knowledge and new skilled scientists in the field.The current creep engineering structural integrity codes are based on empirical equations extracted from tests in certain standard conditions. They ignore the material microstructure, which evolves during a 60 years' service of a power plants. An important limiting factor that is currently ignored in the engineering codes and will be highly influential in the mechanical response of components for next generation power plants is irradiation damage. One of our objectives is therefore to include the effects of irradiation damage on the macro-scale mechanical response of materials by including the changes it makes on the material microstructure in their constitutive laws. To this end our main objective is to develop a predictive, multi-scale, microstructurally informed creep deformation model. The model spans from the fundamental physical equations that govern the dislocation mobility at high temperature (dislocations are imperfection in material crystal structure and their movements under load account for most the material permanent deformation) to the behaviour of engineering components with complex geometries and varied loading history and conditions made from homogenised material. The model will help engineers to predict the behaviour of critical components in a nuclear reactor and make informed decision on their fitness for service which is a crucial safety decision.Once our creep model is validated and verified by experiments across three mico, meso, and macro length scales, it will provide the foundation for a new generation of engineering structural integrity codes that are based on a mechanistic understanding the material and its microstructure and therefore is predictive, more accurate and not confined to the test conditions it is based on. This will be an invaluable asset for the UK to play a major role in designing, building, and operating future nuclear power plants.