Evaluation of Irradiation Effects on Concrete Structure: Gamma-Ray Irradiation Tests on Cement Paste

In assessing reduction of concrete strength under irradiated conditions, reference levels are introduced: 1×1020 n/cm2 for fast neutrons and 2×1010 rad (2×105 kGy) for gamma-rays. Concrete structures are regarded as sound as long as irradiance levels accumulated during long-term operation are less than the reference levels. Most experimental investigations of irradiation effects on concrete were performed in the 1960’s and 1970’s. However, there is no good explanation of how concrete deteriorates under neutron and gamma-ray irradiation. Hilsdorf put the primal irradiation test data together to investigate effects of irradiance levels on residual strength ratio of concrete [1]. The reference levels were obtained from his paper. However, the test conditions in which the data quoted by Hilsdorf were obtained are very different from the irradiation and heat conditions usually found in a Light Water Reactor (LWR). This paper summarizes the interactions between radiation and concrete components and presents the results of gamma-ray irradiation tests on cement paste in order to provide a better understanding of the deterioration mechanisms of concrete under irradiation and heat conditions in LWRs.