Construction and preliminary testing of an NPP concrete containment wall with simulated defects

Portland cement concrete (PCC) is a highly heterogeneous, aging quasi-brittle material that is an important part of nuclear power plant (NPP) safety structures such as containment walls. This creates a need to develop technologies and methods that can nondestructively image and evaluate the condition of PCC to improve the reliability, sustain the safety, and extend the operating lifetimes of nuclear power plants. While current volumetric imaging techniques and results from previous studies on thinner, less densely reinforced PCC structures have shown promise, these methods should be comprehensively compared with respect to the challenges associated with thick reinforced concrete sections representative of NPP construction. However, large concrete samples that allow for comparative testing of various nondestructive evaluation (NDE) technologies and methods are not readily available. To address this limitation, a reinforced concrete sample was constructed with simulated defects to represent NPP concrete structures. The experiences, strengths, and limitations of the constructed specimen with respect to realistic aging concrete in NPP safety structures will be discussed in this study. The preliminary volumetric imaging results of an ultrasonic array-based approach will also be presented along with preliminary identification of the factors significantly affecting NDE capabilities with respect to large representative NPP containment walls.