Methods for assessing the soundness of concrete exposed to irradiation are being developed within the framework of a project of the Nuclear Regulation Authority (NRA) “Japan Ageing Management Program for System Safety”. This paper presents the background of this project and recent research works. The major reason for deterioration of concrete under irradiation conditions is expansion of aggregate due to neutron and gamma-ray irradiation. Dislocation of atoms in covalent structures of aggregate minerals, and resultant lattice constant change and alteration to amorphous phase are produced by fast neutrons. In addition, through electronic exertion, some energy deposition is accumulated as permanent distortion/strain in atomic structures. Other effects are also summarized. We plan to conduct a neutron irradiation test from May 2013. In selecting mix proportions and concrete components for the irradiation test program, sample size as a function of capsule size and gamma-heating, cement type, and aggregate size and type are determined based on preliminary experiments.

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