Institute of Fundamental Technological Research

This article examines the problem of the service life of reinforced concrete structures intended for nuclear power plants and radiation waste storage bunkers when exposed to radiation. This research focused on assessing the corrosion resistance of steel bars under conditions of simultaneous exposure to gamma radiation and various environmental conditions affecting the rate of carbonation. Electrochemical measurements of steel bars were carried out on samples in three environmental conditions: in a laboratory–dry; enclosed in a can at RH = 50%; and enclosed in a can at RH = 100%. The durability of the passivation layer of steel on non-irradiated and irradiated specimens after 8 months of exposure to gamma radiation was compared. A lower degradation effect of gamma radiation was visible in fully water-saturated specimens

corrosion of steel, relative humidity variability, carbonation condition, EIS, polarization curve

A viable prediction of service life of reinforced concrete structures exposed to irradiation environment is necessary to support a license extension for currently operating nuclear power plants as well as to support concrete mix optimization for new builds. An experimental study was carried out to evaluate the corrosion performance of mild steel reinforcing bars under gamma irradiation at environmental conditions favoring accelerated carbonation. in elevated temperature. The electrochemical impedance spectroscopy and potentiodynamic electrochemical tests were performed to assess the corrosion rates on the rebar surfaces. Effects of irradiation were also examined in regard to capillary pore size distribution by mercury intrusion porosimetry and mesopore distribution based on nitrogen desorption data. Companion tests were performed to determine the compressive and flexural strength of mortar exposed to gamma irradiation. Relative effects of gamma irradiation are reported for mortar specimens containing fly ash or limestone powder used for partial replacement of Portland cement up to 40% by mass. Gamma irradiation dose up to 2 MGy was found to affect the properties of passive layer of steel in comparison to non-irradiated specimens. A decrease of corrosive potential and passivation potential was found. An increase of corrosion current density by an order of magnitude due to gamma irradiation was observed. Parameters of polarization curves of steel indicated unstable passive layer on steel reinforcement in irradiated mortars.

gamma irradiation, steel corrosion, supplementary cementitious materials, modification, electrochemical impedance spectroscopy, corrosion potential, Barrett-Joyner-Halenda porosity