Theoretical Modeling of the Effects of Neutron Irradiation on Properties of Concrete

Abstract

To ensure safe operation of nuclear power plants (NPPs) during their extended service life, comprehensive investigation of the behavior of concrete structures and their components under long-term nuclear radiation is needed. In this paper, a theoretical model is developed to predict the deterioration in modulus of elasticity and volume change of concrete under neutron radiation, taking into account both the effects of neutron radiation and radiation-induced heating on the mechanical properties and volume changes of concrete. The internal structure and components of concrete were represented by a multiphase and multiscale model that was based on the generalized self-consistent scheme. The effects of neutron radiation and elevated temperature on the elastic modulus of aggregates and elastic properties of hardened cement paste were characterized based on available test data. Three different types of volumetric strains in concrete under neutron irradiation were considered in the model: expansion of aggregates, shrinkage of hardened cement paste, and thermal expansion of the two phases under the heat of neutron irradiation. It is shown that the volume change of concrete is dominated by the expanding characteristic of aggregates. The proposed model provides a general framework that can estimate the degradation of elastic properties and volume change of concrete under neutron radiation and radiation heating and can be further improved when new experimental results become available.