The surrounding conditions of the shielding concrete, (moisture and temperature), affect the water content within it, and therefore, the attenuation coefficient of the concrete. In this study, the impact of changing the amount of water, in four types of local candidate shielding concretes was investigated. The concrete attenuation coefficient of gamma-rays has been identified experimentally and computationally using the MCNP-4C code. The results show a significant decrease in the attenuation coefficient of each the four concrete samples due to the water losses, especially between 20- 100 oC. Acceptable compatibility was noticed between the measured and calculated results of the attenuation coefficient of the studied concrete samples.

Keywords : Radiation shielding, Reactor concrete, Gamma Attenuation