SiC fuel cladding: Macroscopic effects of radiation on mechanical and thermal properties from microstructural-scale characterisation and modelling

由于碳化硅在轻水反应堆中具有良好的中子性能、高温强度、辐照下的优异稳定性，并且与传统的锆合金燃料包壳相比，在事故条件下可减少氧化，因此碳化硅是核反应堆中耐事故燃料包壳应用的候选材料。鉴于福岛核事故以及随后对事故容忍燃料概念（ATF）的重视，这些材料的开发和研究尤为重要。最近的研究尝试了几种基于sic的包层设计在实际轻水堆运行条件下的行为模型，并给出了整个燃料寿命期间的应力和失效概率预测。这些模型将非常复杂，高度结构化的SiC-SiC复合材料视为均质材料。这一假设严重限制了这些模型的适用性和准确性，使得这些模型不能有效地用于熔覆宏观和微观结构的优化。为了设计这些材料以产生最佳的性能，需要一个更精细的模型来准确地表示复合材料的微观结构和各种成分的行为。对于这样一个全面的模型，需要将复合材料组成成分的材料特性、它们的相互界面以及它们对辐照的响应方式作为输入参数。本项目旨在开发本地化的材料评估技术，在相关的微观尺度上直接测量辐射前后sic基包层各个成分的机械和热性能，为将在本项目中开发和验证的综合模型提供输入参数。

Silicon carbide is a candidate material for accident tolerant fuel cladding applications in nuclear power reactors due to its good neutronic performance for light water reactors, high temperature strength, exceptional stability under irradiation, and reduced oxidation compared to conventional Zircaloy fuel cladding under accident conditions. The development and investigation of these materials is particularly important in the light of the Fukushima event and the subsequent emphasis on Accident Tolerant Fuel concepts (ATF). Recent efforts have attempted to model the behaviour of several SiC-based cladding designs under realistic LWR operating conditions, and give predictions of stresses and failure probabilities throughout the fuel life. These models treat the very complex, highly structured SiC-SiC composite as a homogenous material. This assumption seriously limits the applicability and accuracy of these models and such models cannot be used effectively to optimize the cladding macro and microstructure.In order to design these materials to produce the best possible performance, a more refined model is needed representing accurately the composite microstructure and the behaviour of the various components For such a comprehensive model, the material properties of the constituent components of the composites, their mutual interfaces, and the way these respond to irradiation, are needed as input parameters.This project aims to develop localized materials assessment techniques to directly measure mechanical and thermal properties of the individual constituents of SiC-based claddings at the relevant micro-scale, before and after irradiation, in order to provide input parameters for a comprehensive model which will be developed and validated in this program.