The effects of neutron irradiation on the mechanical properties of mineral analogues of concrete aggregates

Abstract

Plans for extended operation of US nuclear power plants (NPPs) beyond 60 years have resulted in a renewed focus on the long-term aging of materials in NPPs, and specifically on 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 High Flux Isotope Reactor at three different fluence levels and at two temperatures. The purpose was to investigate the degradation of mechanical properties at neutron doses above the levels expected in US NPPs under 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 reveals changes in deformation and fracture mechanisms in the irradiated mineral analogies. Results for the nanohardness as a function of dose and temperature are presented and discussed for quartz, calcite, and dolomite.