The micromechanics of ductile to brittle fracture in polycrystals

气候变化是我们时代应该应对的最重要挑战之一。它是由温室气体浓度增加引起的。为了减少排放，提出了几项建议，例如，使用电动汽车或将可再生能源和无排放电力生产结合到电网中。在安大略，这已转化为250亿美元的投资，用于翻新加拿大氘铀（CANDU）核反应堆，该反应堆自2013年开始进行，计划于2033年完成。作为稳定电网的可靠能源，CANDU反应堆在安大略生产了50%以上的零排放电力，在全国范围内生产了15%。为了进一步保持清洁核能的生产，加拿大国家资源部最近制定了一份开发和部署小型模块化反应堆（SMR）的路线图。然而，要使用这些先进技术，必须克服几个障碍。这包括提高公众对核能的接受程度，并通过延长反应堆堆芯所用材料的寿命来降低运行CANDU或建造SMR的成本。提高这些材料的寿命需要开发先进的工具箱，以帮助了解控制其降解的潜在机制。该计划的重点是开发和验证先进的多物理场多尺度数值模型，以研究用于核反应堆堆芯的金属合金的退化机制。这些模型将用于研究短裂纹如何在纳米和微米尺度上成核，以及它们如何传播并最终影响工程部件的寿命。最重要的是，将首次研究裂变反应产生的中子辐照对金属合金脆化和断裂的影响。将给予关注的CANDU堆的核心和SMR的潜在候选人使用的材料。此外，将开发或使用先进的基于衍射和基于图像的实验技术来验证数值模型。结果将与机器学习算法相结合，以提高开发方法的效率。该计划的结果将有助于了解控制金属合金延性和脆性失效的潜在机制。这将减少对反应堆材料进行过多实验的成本，并将为估计部件寿命提供更准确的方法。这将有助于放宽核工业中过于保守的安全标准，从而有助于降低反应堆的运营成本。此外，该方案旨在通过培训一批高素质的多元化人员，提高核能领域的公平性、多样性和包容性，从而提高公众对核能的接受程度。

Climate change is one of the most important challenges of our time that should be addressed. It is caused by the increase in the concentration of greenhouse gases. To reduce the emissions, several recommendations are made, e.g., the use of electric vehicles or the integration of combined renewable and non-emitting power production to the electricity grid. In Ontario, this has translated to $25B investment on the refurbishment of the CANada Deuterium Uranium (CANDU) nuclear reactors which has been taking place since 2013 and is scheduled to finish in 2033. As a source of reliable energy that stabilizes the electricity grid, CANDU reactors have been producing more than 50% of zero-emission electricity in Ontario, and 15% nationwide. To further maintain the production of clean nuclear energy, the National Resources Canada has recently prepared a roadmap for developing and deploying Small Modular Reactors (SMRs). To use such advanced technologies, however, there are several barriers that should be overcome. This includes improving the public acceptance of nuclear energy, and reducing the cost of running CANDUs or building SMRs by improving the lifespan of the materials used in the core of the reactors. Improving the lifespan of these materials requires the development of advanced toolboxes that help understand the underlying mechanisms that control their degradation. This program focuses on the development and validation of advanced multiphysics multiscale numerical models to study the degradation mechanisms of the metal alloys used in the core of nuclear reactors. The models will be used to study how short cracks nucleate at the nano and microscales and how they propagate and eventually affect the lifespan of engineering components. Most importantly, for the first time, the effects of neutron irradiation from fission reactions on the embrittlement and fracture of metal alloys will be studied. Attentions will be given to the materials used in the core of CANDU reactors and the potential candidates for SMRs. In addition, advanced diffraction-based and image-based experimental techniques will be developed or used to validate the numerical models. The results will be coupled with machine learning algorithms to enhance the efficiency of the developed methods. The outcomes of this program will help understand the underlying mechanisms that control both ductile and brittle failure of metal alloys. This will reduce the cost of excessive experimentation of reactor materials and will provide more accurate methods for estimating components lifespans. It will help relax the over-conservative safety standards used in nuclear industry which will subsequently help reduce the cost of running the reactors. In addition, this program is designed to improve the public acceptance of nuclear energy by improving equity, diversity, and inclusion in this field through training a diverse group of highly qualified personnel.