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

本研究将对燃料棒Zr包层的微观结构演变及辐照损伤动力学进行研究。了解Zr的行为是下一代核反应堆的关键，尤其是燃料设计尚未确定的小型模块化反应堆（smr）。相变的统计模型将与连续扩散模型相结合，利用扩散的多组分描述来评估包层的动力学。热力学数据库将用于确定相稳定性，平衡成分，并最终确定相变的化学驱动力。将探索发展流动数据库，以补充现有的热力学数据库。通过实现动力学的热力学描述，有可能捕获多个亚稳和平衡相的演变。该模型将探讨关于Zr包层内辐照损伤动力学的不同假设。这些模型将根据国家核实验室（NNL）从现役反应堆包壳中产生的实验数据进行开发和验证。了解辐照损伤动力学对于在反应堆中以及在储存期间移除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中使用的燃料包层类型的决策，以及寿命和随后的存储考虑。最后，该项目还具有基于建模的优势，因此在当前COVID限制下是可以实现的。

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.