Development of Materials Surveillance Technology for Small Modular Reactors

由于高温、高应力、具有化学侵蚀性的冷却剂和强烈的辐射通量的组合，SMR的核心为材料提供了异常恶劣的环境。这对用于制造SMR结构部件的材料的长期可靠性提出了严重挑战。在这些条件下，结构材料的主要失效模式是蠕变-疲劳失效，即在恒定或缓慢变化的载荷下，由于循环载荷夹杂着保持期而导致的裂纹的萌生和随后的扩展。不幸的是，尽管做了大量的工作，但蠕变-疲劳相互作用的根本原因仍然不清楚，特别是当与腐蚀和辐射损伤结合在一起时。本提案的目的是开发SMR的材料监测技术，以确保关键结构部件在其整个设计寿命内保持其功能和完整性。该项目将设计和验证现场被动加载的试件，这种试件可以通过两种材料的热膨胀系数不匹配并由核反应堆中的温度变化驱动来被动地对测试材料产生循环热机械载荷，而不需要在反应堆边界内安装任何电线或致动器。然后，测试样品将被安装在反应堆的关键位置，经历与部件相同的环境和降解机制，并定期进行监测，以确保它们没有发生故障。这些试件可以被设计成在预定的时间长度之前失效，以表明结构设计存在问题，并要求采取纠正措施。拟议的研究将为SMR的安全结构设计提供关键信息，并确保关键结构部件在整个设计生命周期内保持其功能和完整性。它还将帮助加拿大制定SMR安全设计和运行的标准和规范。

The core of a SMR presents an exceptionally harsh environment for materials due to the combination of high temperature, high stresses, a chemically aggressive coolant and intense radiation fluxes. This poses a serious challenge to the long-term reliability of the materials used to construct the structural components of SMRs. Under these conditions the dominant failure mode of structural materials is creep-fatigue failure which is the initiation and subsequent growth of flaws due to cyclic load interspersed with hold periods at constant or slowly varying load. Unfortunately, despite a great deal of effort, the fundamental cause of creep-fatigue interaction is still unclear, particularly when combined with corrosion and irradiation damages. The objective of the present proposal is to develop the materials surveillance technology for SMRs to ensure that key structural components retain their function and integrity throughout their full design life. The project will design and validate the in-situ, passively loaded test specimens that can generate cyclic thermomechanical load to the test material passively through a mismatch in the thermal expansion coefficient of two materials and driven by a temperature change in the nuclear reactors, without requiring any wiring or actuators within reactor boundaries. The test specimens would then be installed at the key locations of reactors, experiencing the same environment and degradation mechanisms as the components, and monitored periodically to ensure that they have not failed. These specimens could be designed to fail before a predetermined length of time, to indicate a problem with the structural design and call for corrective actions. The proposed research will provide critical information for the safe structural design of SMRs and ensure that key structural components maintain their functionality and integrity over the entire design life. It will also help Canada develop standards and codes for the safe design and operation of SMRs.