Microstructural characterization of reactor cavity concrete

Reactor cavity concrete, a major component of Light Water Reactors (LWRs), serves as a biological shield and as a structural support. The most important aging mechanisms that affect the structural integrity of reactor cavity concrete are neutron irradiation, alkali-silica reaction (ASR), and loss of moisture. All these phenomena reduce the strength and can generate cracks in the cavity concrete structures. Neutron irradiation can lead to the gradual amorphization of the minerals that form the aggregates. With time the amorphization of minerals induces the expansion of mineral phase resulting in radiation-induced volumetric expansion (RIVE) [1]. In a similar fashion, ASR induces swelling in the concrete. In this manuscript, the authors will present results from a series of complimentary microscopy techniques that can be used to characterize the RIVE and ASR effects to develop a more coherent understanding of how these effects degrade the integrity of the concrete. These techniques include x-ray computed tomography (XCT), transmission electron microscopy (TEM), x-ray fluorescence (XRF) and electron backscatter diffraction (EBSD). Using these techniques in combination is necessary to develop an understanding of the fundamental mechanisms that lead to concrete degradation.