Effect of Temperature on the Degradation of Nuclear Reactor Containment Buildings of APR1400

Abstract

Reactor Containment buildings (RCBs) in nuclear power plant (NPPs) which is a structure playing an important role as the final barrier that provide safety functions in order to minimize or prevent the release of radioactive materials and also provides another important function as structural support to the equipment's inside it [2]. Therefore, it is very important to maintain the structural integrity of RCBs. It has been well known that RCBs in NPPs suffer from degradation and aging during the operation of NPP. Studies and experience show that there are various types of aging phenomena that occur in concrete and reinforcing steels. Among the aging phenomena, reinforcing steel corrosion has been identified as the most serious phenomenon governing the service life of concrete structures [3], which is mainly caused by chloride ions (Cl-) at the surface of reinforcing steels. The corrosion of reinforcing steels is affected by several environmental factors such as temperature, relative humidity, and salt content in air. Among them, atmospheric temperature has especially a significant effect on the diffusion of chloride ions as well as corrosion rate itself. However, only a few studies on the effect of temperature on corrosion of reinforcing steels have been done even though higher temperature may reduce significantly the service life of concrete structures including RCBs. In this project, the effect of temperature on the service life of RCBs is evaluated through performing electrochemical experiments and numerical analysis using finite element analysis (FEA). Major findings from the project were as follows: the time to depassivation (tinit) at 50°C was only 0.38 times that at 22°C, implying that the temperature effect is very significant on the time to. In addition, the localized corrosion current density at 50°C was 5.6 times higher than that at 22°C. This concludes that the temperature is an important parameter to consider in the design of the concrete structure and specially the RCBs since it has a safety functions. In UAE, the temperature difference is obvious, so it is important to put intensive investigation of temperature on the structural integrity of such structure. Indexing Terms: Reactor containment building, service life prediction, Depassivation, corrosion rate, Finite Element analysis,

Date of Award	Jul 2017
Original language	American English
Supervisor	Yongsun Yi (Supervisor)