Radiation effects in concrete for nuclear power plants, Part II: Perspective from micromechanical modeling

•A micromechanical model for irradiated concrete is proposed.•Confrontation with literature data is successful.•Neutron radiation-induced volumetric expansion is a predominant degradation mode.•The nature of the aggregate alters the severity of damage to irradiated concrete. The need to understand and characterize the effects of neutron irradiation on concrete has become urgent because of the possible extension of service life of many nuclear power generating stations. Current knowledge is primarily based on a collection of data obtained in test reactors. These data are inherently difficult to interpret because materials and testing conditions are inconsistent. A micromechanical approach based on the Hashin composite sphere model is presented to derive a first-order separation of the effects of radiation on cement paste and aggregate, and, also, on their interaction. Although the scarcity of available data limits the validation of the model, it appears that, without negating a possible gamma-ray induced effect, the neutron-induced damage and swelling of aggregate plays a predominant role on the overall concrete expansion and the damage of the cement paste. The radiation-induced volumetric expansion (RIVE) effects can also be aided by temperature elevation and shrinkage in the cement paste.