Modelling the Fuel Performance and Structural Integrity of TRISO Nuclear Fuel

核能在生产低碳能源方面具有巨大潜力，但到目前为止，它主要是通过促进基本负荷发电来实现这一目标的。高温反应堆提供了超越这一点的机会，并已被选为英国先进核反应堆示范工厂的首选技术。通过提高出口温度，核电站将能够产生过程热和电力。然而，更高的冷却剂温度将要求燃料设计的逐步改变。提出的一项设计变更是放弃UO2燃料颗粒，转而使用三结构各向同性颗粒燃料。在这些燃料中，UO2被包含在一个球形燃料内核中，被多孔缓冲层和三层涂层包围，旨在保留粒子中的裂变产物。周动力学是一种新兴的计算力学工具，用于预测各种复杂材料和载荷下的开裂。到目前为止，研究小组已经为TRISO燃料建立了一个二维热弹性动力学模型。该模型能够捕捉到TRISO涂层燃料颗粒的每个组成部分的开裂，并证明了缓冲层开裂的可能性，缓冲层作为上覆碳化硅层的应力增加器，其任务是提供密封以防止裂变产物从燃料颗粒中逸出。本博士将通过引入蠕变和辐照膨胀来进一步发展当前的热弹性周动力学模型，这两种模型都是已知的各向异性。这将使燃料颗粒的完整辐照历史得以建模，并使目前的1.5D商业燃料性能模型（如应力3）得到充实。该项目的主要目标如下：开发完整辐照历史的有限元模型，以确定核和缓冲层脱粘的影响，并使周动力模型成为基准。为每种材料建立各向异性蠕变动力学模型，并将其与有限元模型进行比较。建立每一种材料在整个燃料历史过程中的围动力学体积膨胀模型，并将其与有限元模型进行比较。将这些模型合并成三iso燃料颗粒辐照的周动力学模型，并与英国国家核实验室提供的辐照数据进行验证。利用该模型，通过对辐照后检验中观察到的特征进行建模，丰富现有的1.5D燃料性能模型。

Nuclear energy has great potential to generate low-carbon energy, however it has until now, largely done this by contributing to baseload electricity generation. High temperature reactors offer the opportunity to move beyond this and have been selected as the technology of choice for the UK's advanced nuclear reactor demonstration plant. By raising the outlet temperatures, nuclear power stations will be able to generate process heat as well as electricity. Higher coolant temperatures will however require a step change in fuel design. One design change being proposed is to move away from UO2 fuel pellets and utilise TRISO (tristructural isotropic) particle fuel. In these fuels, the UO2 is contained in a spherical fuel kernel, surrounded by a porous buffer layer and three coating layers, intended to retain fission products in the particle. Peridynamics is an emerging computational mechanics tool for predicting cracking in a diverse range of complicated materials and loadings. To date, the research team have built a 2D thermo-elastic peridynamic model for TRISO fuel. This model is able to capture cracking in each component of the TRISO coated fuel particle and has demonstrated the possibility of cracking in the buffer layer acting as a stress raiser in the overlying SiC layer which is tasked with providing a hermetic seal to prevent the egress of fission products from the fuel particle. This PhD will aim to further develop the current thermo-elastic peridynamics model by introducing creep and irradiation swelling, both of which are known to be anisotropic. This will enable the complete irradiation history of the fuel particle to be modelled and the current 1.5D commercial fuel performance models such as STRESS3 to be enriched. Key aims for the project are as follows:To develop a finite element model for the complete irradiation history in order to determine the impact of debonding of the kernel and buffer and enable benchmarking of peridynamic models.To develop a model for anisotropic creep in peridynamics for each material and benchmark this against finite element models.To develop a model for volumetric swelling in peridynamics for each material during the entire fuel history and benchmark this against finite element models.To combine these models into a peridynamic model for the irradiation of TRISO fuel particles and validate this against irradiation data made available by the UK National Nuclear Laboratory.To use the model to enrich the current 1.5D fuel performance models by modelling features observed in post-irradiation examination.