Many known defects that develop in concrete overtime may threaten the safety and security of theinfrastructure in nuclear power plants (NPPs). Thesedefects also exist in other concrete infrastructures, but theharsher nuclear environment adds significant difficulty totheir detection and correction. To monitor the structuralhealth of a concrete facility, coring and other destructivetesting methods are typically employed, but this is not theideal solution for NPP concrete infrastructure. Developinga reliable nondestructive evaluation (NDE) method toevaluate the damage in these structures will greatlyimprove the long-term operation and safety of NPPs. TheUniversity of Tennessee, in collaboration with Oak RidgeNational Laboratory, developed a large-scale experimentto study one known defect due to the reaction betweenhydroxyl ions of the alkalis in cement paste and thesiliceous minerals present in some aggregates known asalkali-silica reactions (ASRs). Alkali-silica gel forms andswells due to its hygroscopic characteristic, causingcracking and material failure. This paper discusses theNDE measurements performed on the large concretespecimens and the reconstructed images from thesemeasurements.
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