Modelling the Fuel Performance and Structural Integrity of TRISO Nuclear Fuel

核能具有产生低碳能源的巨大潜力，但迄今为止，核能主要是通过促进基荷发电来实现这一目标。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量以及电力。然而，更高的冷却剂温度将需要燃料设计的阶跃变化。正在提出的一项设计变更是放弃UO2燃料芯块，而使用TRISO（三结构各向同性）颗粒燃料。在这些燃料中，UO2包含在球形燃料核中，由多孔缓冲层和三层涂层包围，旨在将裂变产物保留在颗粒中。周向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，研究小组已经建立了TRISO燃料的二维热弹性周波模型。该模型能够捕获TRISO涂覆的燃料颗粒的每个组分中的裂纹，并且已经证明了缓冲层中的裂纹的可能性，该缓冲层充当上覆SiC层中的应力集中器，该上覆SiC层的任务是提供气密密封以防止裂变产物从燃料颗粒流出。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波模型，这两者都是各向异性的。这将使完整的辐照历史的燃料颗粒进行建模和目前的1.5D商业燃料性能模型，如应力3丰富。该项目的主要目标如下：为整个辐照历史开发一个有限元模型，以确定内核和缓冲层脱粘的影响，并对周向模型进行基准测试。为每种材料开发一个周向各向异性蠕变模型，并将其与有限元模型进行基准测试。为每种材料开发一个在整个燃料历史中周向体积膨胀模型，并将其与有限元模型进行基准测试。将联合收割机这些模型组合成TRISO燃料颗粒辐照的周向模型，并根据英国国家核实验室提供的辐照数据对其进行验证。使用该模型，通过模拟辐照后检查中观察到的特征，丰富目前的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.