Condition assessments and corrosion measurements of cooling water chambers in a nuclear power plant

This research was done as a part of the project Aging Management of Concrete Structures in Nuclear Power Plants (MANAGE) in The Finnish Research Programme on Nuclear Power Plant Safety 2011-2014, SAFIR 2014. The aim of this research was to carry out condition assessments and corrosion measurements to evaluate the condition of the reinforced concrete structures of the cooling water chambers in a Finnish nuclear power plant and to verify the possible state of corrosion of the reinforcement. The condition assessment was based on concrete samples taken from the structures above the water level, at the range of the water level, and under the water level. The concrete samples were subjected to the following analyses: the carbonation depth, the chloride profile, and the study of the microstructure based on thin sections. Concrete cover measurements and visual inspection of the concrete structures and exposed reinforcements were done to approve the corrosion measurements. These determinations and measured Half-Cell potentials were used with the Pourbaix-diagrams for steel to estimate the state of corrosion of reinforcement. The measured depths of concrete cover correlated the design value 60 mm. The average depth of carbonation of concrete was very small; varying between 0 mm and 12 mm. Estimations for the state of corrosion of reinforcement according to the Pourbaix-diagrams showed the reinforcement to be in passive state. Visual inspections confirmed the estimation; all of the exposed reinforcing bars were intact.