ABSTRACT
In fact, radiation in the form of either fast and thermal neutrons, primary gamma rays or gamma rays produced as a result of neutron capture can affect concrete. Changes in the properties of concrete appear to depend primarily on the behavior of concrete aggregates that can undergo a volume change when exposed to radiation (Kaplan 1989). Radiation damage in concrete aggregates is caused by changes in the lattice structure of the minerals in the aggregates. Fast neutrons are mainly
1 INTRODUCTION
With this work, a recently developed extension of a Finite Element (F.E.) code, NEWCON3D, that can perform fully coupled hygro-thermomechanical 3D analyses for cementitious materials, is outlined; the research code is applied to study the effects of nuclear radiation on a concrete shielding for the specific neutron source of the study case, in conjunction with a Monte Carlo code developed by CERN and INFN of Milan, Fluka, used to describe the radiation field (neutron fluence and
responsible for the considerable growth, caused by atomic displacements (Naus 2007), that has been measured in certain aggregates (e.g., flint). Quartz aggregates, made of crystals with covalent bonding, seem to be more affected by radiation than calcareous aggregates that contain a weaker ionic bonding (Hilsdorf et al., 1978). Neutron fluences of the order of 1019n/cm2 (neutrons per square centimeter) and gamma radiation doses of 1010 rad seem to become critical for concrete strength (Hilsdorf et al., 1978; Naus 2007) and there is also evidence that a prolonged exposure to nuclear radiation significantly increases the reactivity of silica-rich aggregates to alkali (Ichikawa & Koizumi 2002).
