Assessment and improvement of resilience of NPP through advanced modelling and simulation

这个与Candu能源公司的合作研究项目包括五个研究主题，包括a)材料水平的长期性能，b)钢筋混凝土（RC）外壳元件的非弹性行为，c)集成最先进的分析工具来模拟结构系统，d)使用模拟工具来评估核电厂系统的地震弹性，e)结果的可视化。为了了解钢筋混凝土结构的长期蠕变和收缩行为，将在实验室对一个具有与典型核电站安全壳结构相似的表面体积比的试件进行测试。湿度和温度边界条件将根据一个典型的安全壳结构的内部环境来定义。实验结果将用于开发更精确的蠕变和收缩模型，通过该模型可以预测安全壳建筑的长期除湿和收缩过程。在结构单元层面，将基于修正压缩场理论（MCFT）建立集成点减少的壳单元。数值单元将能够预测RC单元在静、动荷载作用下的刚度和破坏过程，包括裂纹的发展和扩展。在系统层面，新开发的元素将与多伦多大学开发的其他复杂的数值模拟工具相结合。综合数值模型将允许在超出设计水平的地震和随后的潜在内部压力增加下对大型核电站系统进行建模和模拟。将进行一系列的分析，以建立一个结构反应的数据库，并将开发一个软件工具来将结果可视化。响应数据库和可视化工具将用于在地震事件发生后立即为决策者提供支持。考虑到安大略省超过50%的电力依赖于核电，对核电站弹性的准确理解将导致一个可持续和有弹性的社会。

This collaborative research project with Candu Energy, Inc. includes five research topics which encompass a) long-term performance at the material level, b) inelastic behaviour of a reinforced concrete (RC) shell element, c) integration of state-of-art analysis tools to simulate a structural system, d) to assess seismic resilience of NPP system using the simulation tool and e) visualization of results. To understand the long-term creep and shrinkage behaviour of reinforced concrete structures, a specimen with surface-to-volume ratio similar to a typical NPP containment structure will be tested in the laboratory. The humidity and temperature boundary condition will be defined based on the internal environment of a typical containment structure. The experimental results will be used to develop a more accurate creep and shrinkage model through which the long-term dehumidification and shrinkage process of a containment building can be predicted. In the structural element level, a shell element with a reduced number of integration points will be developed based on modified compression field theory (MCFT). The numerical element will be able to predict the stiffness and failure process of an RC element including crack development and propagation under both static and dynamic loads. At the system level, the newly developed element will be integrated with other sophisticated numerical modelling tools that have been developed in University of Toronto. The integrated numerical model will allow modelling and simulation of a large nuclear power plant system under beyond-design level earthquakes and subsequent potential internal pressure increases. A series of analyses will be carried out to build a database of the structural responses, and a software tool will be developed to visualize the results. The response database and visualization tool will be used to support decision makers immediately after an earthquake event. Considering more than 50% of electric energy in Ontario relies on nuclear power, the accurate understanding on the resilience of NPPs will lead to a sustainable and resilient society.