Multiscale Simulation of Second Phase Particle Evolution in Zirconium

锆合金由于其良好的性能和中子透过性的组合而广泛用于核燃料组件。微观结构控制对于获得具有所需性能的锆合金至关重要，并且在长使用寿命内保持所需的微观结构和性能对于反应堆性能和安全性至关重要。微观结构的一个重要特征是第二相沉淀颗粒（SPP）。这些颗粒在加工过程中沉淀，对重要性能，特别是腐蚀性能有很大影响。众所周知，控制颗粒的尺寸和分布对于确保保持性能目标是至关重要的，但这是复杂的，因为SPP在热和辐射暴露下演变，可能对性能产生负面影响。为了理解和预测这些效应，SPP演化的微观结构模型将具有很大的实用性，但是开发这样的模型需要以足够简单的方式捕获复杂的物理机制，以便进行时间有效的预测。在这个方向上已经采取了初步步骤，建立一个基本的建模框架，但要成为一个有用的工具，定量预测和可靠的工业用途，需要克服重大障碍，必须通过实验洞察机制。现在正是解决这个问题的时候，因为英国的一项主要活动（EPSRC MIDAS计划）已经启动，该计划将探索辐照锆合金中微观结构的演变，其细节程度以前无法达到，沿着开发模拟工具来预测原子尺度的行为。该项目与MIDAS合作，将利用所得数据开发SPP演化的微观结构尺度模型，包括辐照效应，以比以前更高的保真度捕获基本物理过程，并根据新的和现有的实验验证模型，以提供其应用的信心。这项工作的成果将是一个模型，用实验数据验证，有助于核电行业更好地了解和预测反应堆用锆合金在加工和使用过程中的组织和性能演变。

Zirconium alloys are widely used in nuclear fuel assemblies due to their favourable combination of properties and neutron transparency. Microstructural control is critical to obtaining zirconium alloys with the desired properties, and maintaining the desired microstructure and properties over long service lives is central to reactor performance and safety. An important feature of the microstructure is second phase precipitate particles (SPPs). These particles precipitate during processing and have a strong influence on important properties, particularly corrosion performance. It is known that control of the size and distribution of particles is vital to ensuring property targets are maintained but this is complex because the SPPs evolve under thermal and irradiation exposure, potentially negatively impacting on performance. To understand and predict these effects, a microstructural model for SPP evolution would be of great utility, but developing such a model requires capturing the complex physical mechanisms in a sufficiently simple way to enable time-efficient predictions to be made. Initial steps in this direction have already been made to establish a basic modelling framework, but to become a useful tool for quantitate prediction and reliable industrial use requires overcoming significant hurdles that must be informed by experimental insights into mechanisms. It is now timely to tackle this problem since a major UK activity (EPSRC MIDAS programme) has now launched which will explore microstructural evolution in irradiated zirconium alloys at a level of detail previously unattainable, along with development of simulation tools to predict atomic scale behaviour. This project, associated with MIDAS, will leverage the resultant data to develop a microstructure scale model for SPP evolution that includes irradiation effects, capturing the essential physical processes at higher fidelity than previously possible and validating the model against new and existing experiments to provide confidence in its application.The outcomes of this work will be a model, verified with experimental data, that can better help the nuclear power industry understand and predict the evolution of microstructure and properties of zirconium alloys used in reactors during processing and service.