Modelling the kinetics of microstructure evolution and irradiation damage within Zr cladding for nuclear fuel

本研究将探讨核燃料棒锆包壳内微结构演化与辐照损伤的动力学。了解锆的行为是下一代核反应堆的关键，特别是小型模块化反应堆（SMR），其中燃料设计尚未决定。相变的统计模型将与扩散的连续模型相结合，以评估整个包层的动力学，利用扩散的多组分描述。一个热力学数据库将被用来确定相稳定性，平衡组成，并最终为相变的化学驱动力。将探讨开发一个流动性数据库，以补充现有的热力学数据库。通过实施动力学的热力学描述，可以捕获多个亚稳相和平衡相的演变。该模型将探讨不同的假设，在Zr包层内的辐照损伤的动力学。这些模型将根据国家核实验室（NNL）在役反应堆包壳产生的实验数据进行开发和验证。了解辐照损伤的动力学对于在反应堆中和储存期间取出后做出有关组件寿命的明智决策至关重要。这项工作将指导SMR中使用的燃料包壳类型的决定，以及寿命和随后的储存考虑。最后，该项目亦具有以模型为基础的优势，因此在当前COVID限制下可实现。

This research will investigate the kinetics of microstructure evolution and irradiation damage within Zr cladding of nuclear fuel rods. Understanding Zr behaviour is key for next generation of nuclear reactors, especially Small Modular Reactors (SMRs), where fuel design has yet to be decided. Statistical models of phase transformation will be coupled with continuum models of diffusion to assess kinetics across the cladding, utilising multi-component descriptions of diffusion. A thermodynamic database will be used to determine phase stability, equilibrium compositions, and ultimately the chemical driving forces for phase transformations. Development of a mobility database will be explored to complement the existing thermodynamic database. Through implementing a thermodynamic description of kinetics, it is possible to capture the evolution of multiple metastable and equilibrium phases. The modelling will explore different hypotheses regarding the kinetics of irradiation damage within the Zr cladding. The models will be developed and validated against experimental data generated by National Nuclear Laboratory (NNL) from inservice reactor cladding. Understanding the kinetics of irradiation damage is vital in enabling informed decisions regarding component lifespan, both in reactor and after removal during storage. This work will steer decisions for the type of fuel cladding used in SMRs, as well as the lifespan and subsequent storage considerations. Finally, this project also has the advantage of being modelling based, and hence achievable given the current COVID restrictions.