Abstract
Plans for extended operation of U.S. Nuclear Power Plants (NPPs) beyond 60 years has resulted in a renewed focus on the long-term aging of materials in NPPs and specifically to reactor cavity concrete. To better understand the effects of neutron irradiation on reactor cavity concrete, a select group of mineral analogues of concrete aggregates were irradiated at the Oak Ridge National Laboratory (ORNL) High Flux Isotope Reactor (HFIR) at three different fluence levels and at two temperatures. The purpose is to investigate degradation of mechanical properties at neutron doses above the levels expected in U.S. nuclear power plants (NPPs) at extended operation. Preliminary findings using nanoindentation clearly show that changes in the mechanical properties of these minerals can be observed and correlated to the neutron-induced damage. Scanning electron microscopy revealed changes in deformation and fracture mechanisms in the irradiated mineral analogies. Results on the nanohardness as a function of dose and temperature will be presented and discussed for quartz, calcite, and dolomite
