2016 | ANNUAL REPORT 65 Figure 2. Irradiation of a limestone disk using 2 MeV protons. Limestone (calcite) exhibits a strong luminescence in the visible spectrum during proton irradiation. The series of irradiation experiments we performed on concrete and its aggregates are some of the first of their kind. This is the first step in performing accelerated aging studies in this complex materials system. — ChrisWetteland, Lecturer,University ofTennessee on this magnitude can cause damage to internal accelerator and vacuum components and trigger safety valves during an experiment. Because of these restraints, experiments were conducted to determine the optimal experimental conditions, including sample mounting, vacuum requirements, and beam currents, to perform accelerated aging experiments. As the U.S. reactor fleet ages and receives extensions for operating outside the intended lifespan, it is critical to understand how the concrete structural components respond to long-term radiation exposure.The research in this Nuclear Science User Facilities (NSUF) sponsored study is the first step in qualifying concrete to perform beyond its intended lifetime.As future researchers examine radiation effects in concrete and its individual components (aggregate and cement), these preliminary experiments will be vital in designing accelerated aging studies. Furthermore, these types of studies will aid in the materials selection for future reactors.This is particularly true in the selection of aggregate products in order to limit potential radiation accelerated alkali– silica reaction (ASR). Accomplishments Concrete irradiations are extremely difficult.The difficulties arise in limiting damage to the concrete arising from conditions that are outside the normal equilibrium conditions in which the structure resides, e.g., atmospheric pressure.