Grant: Alliance Grants

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.