Effect of Temperature Gradient on Chloride Ion Diffusion in Nuclear Reactor Containment Building Concrete

Abstract

Chloride diffusion through concrete is influenced by harsh environmental conditions such as high ambient temperature and relative humidity. This paper examined the influence of temperature gradient on chloride diffusion in concrete under high ambient temperature conditions. Chloride diffusion tests using cylindrical concrete samples were performed in constant temperature and temperature gradient conditions. In a temperature gradient condition, a much higher chloride concentration was measured than at constant temperatures, which could not be explained only by the mass diffusion driven by the concentration gradient. A new analytical model of chloride diffusion with the mass diffusion term including the temperature effect and the thermo-diffusion term including the temperature gradient effect was applied to the results, which showed that the thermo-diffusion contribution was significant. Using the analytical model with the mass diffusion (DCl) and thermo-diffusion (DT) coefficients, the service life of reactor containment buildings (RCBs) in nuclear power plants (NPPs) in the Middle Eastern and North African (MENA) region was estimated. The results showed that the service life of the RCBs could be reduced by the temperature gradient, indicating the possible application of the proposed analytical model.

Influence of Mix Design on Chloride Diffusion in Concrete Structures under Temperature Gradient Conditions

“…The powder was then used to measure the chloride content by the potentiometric titration according to ASTM C1152/1152 M-04 (2012) standard. More details of the experimental setup for the chloride diffusion tests and the measurement of the chloride content in the concrete samples are referred to as An et al [4].…”

“…Consequently, the service life of the concrete structures is shortened. Environmental factors such as temperature and relative humidity have been reported to affect the rate of chloride ion diffusion in concrete [3,4]. Furthermore, the concrete microstructural properties such as porosity and permeability play a major role in the diffusion of chloride ions in concrete.…”

“…They reported that chloride content for the concrete samples exposed to the temperature gradient condition were much higher than that for the concrete samples exposed to the constant temperature condition. In our previous work [4], we examined the influence of a temperature gradient on chloride ion diffusion in concrete using experimental and numerical methods. It was estimated that the corrosion initiation time of reactor containment buildings at ambient temperature of 50 ℃ could be shortened by 30 ~ 40% due to thermal diffusion caused by a temperature gradient.…”

Chloride Diffusion in Concrete under Temperature Gradient Condition in Arid Climates

“…As such, a TG situation is created through the RCB walls. Previous studies have shown that the chloride ion diffusion increases significantly in concrete when the CG and TG are in the same direction [1,2]. However, none of these studies have extensively examined the effect of water-to-cement (w/c) ratio on chloride ion diffusion under CG and TG conditions.…”