Multiscale Simulation of Second Phase Particle Evolution in Zirconium

由于具有良好的性能和中子透明性，锆合金被广泛应用于核燃料组件中。微观组织控制是获得具有所需性能的锆合金的关键，而在较长的使用寿命内保持所需的组织和性能是反应堆性能和安全的核心。显微组织的一个重要特征是第二相析出粒子(SPP)。这些颗粒在加工过程中析出，对重要性能，特别是腐蚀性能有很大影响。众所周知，控制颗粒的大小和分布对于确保保持性能目标至关重要，但这是复杂的，因为SPP在热和辐射暴露下发生变化，可能对性能产生负面影响。为了理解和预测这些影响，SPP演化的微观结构模型将是非常有用的，但开发这样一个模型需要以足够简单的方式捕捉复杂的物理机制，以便能够进行时间效率的预测。在这个方向上已经采取了初步步骤，以建立一个基本的建模框架，但要成为量化预测和可靠的工业使用的有用工具，需要克服重大障碍，这些障碍必须通过对机制的实验洞察来了解。现在是解决这一问题的时候了，因为英国现在已经启动了一项重大活动(EPSRC Midas计划)，该活动将以以前无法达到的详细程度探索辐照后的锆合金的微结构演变，以及开发预测原子尺度行为的模拟工具。这项与MIDAS相关的项目将利用产生的数据来开发SPP演变的微观结构尺度模型，该模型包括辐射效应，以比以前可能的更高保真度捕捉基本物理过程，并针对新的和现有的实验对该模型进行验证，以提供对其应用的信心。这项工作的结果将是一个经实验数据验证的模型，可以更好地帮助核电行业了解和预测在加工和服务过程中用于反应堆的锆合金的组织和性能的演变。

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.