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，然而到目前为止，它主要是通过对基本负荷发电做出贡献来做到这一点的。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技术选择。通过提高出口温度，核电站将能够产生过程热和电力。然而，更高的冷却液温度将要求燃料设计逐步改变。正在提议的一个设计变化是放弃UO2燃料颗粒，而使用Triso(三结构各向同性)颗粒燃料。在这些燃料中，UO2包含在一个球形燃料核中，由一个多孔的缓冲层和三个包覆层包围，旨在将裂变产物保留在粒子中。周期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裂纹。到目前为止，研究小组已经为TRISO燃料建立了一个2D热弹性动力学模型。该模型能够捕获TRISO涂层燃料颗粒每个组分的裂纹，并证明了缓冲层破裂的可能性，该缓冲层在覆盖的碳化硅层中充当应力提升器，其任务是提供密封，以防止裂变产物从燃料颗粒中泄漏。本文旨在通过引入蠕变和辐射膨胀来进一步发展当前的热弹性动力学模型，这两个模型都是各向异性的。这将使燃料颗粒的完整辐照历史得以模拟，并丰富目前的1.5D商业燃料性能模型，如STRESS3。该项目的主要目标如下：建立完整辐照历史的有限元模型，以确定核和缓冲器脱粘的影响，并实现动态模型的基准。为每种材料开发动态各向异性蠕变模型，并将其与有限元模型进行比较。为每种材料在整个燃料历史中建立动态体积膨胀模型，并将其与有限元模型进行比较。将这些模型组合成三元燃料粒子辐照的动态模型，并根据英国国家核实验室提供的辐照数据进行验证。使用该模型可以通过模拟在辐照后检查中观察到的特征来丰富当前的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.