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Session Chair: Andreas Schiffer, Khalifa University of Science and Technology, United Arab Emirates
Effect of aging on the aircraft impact to reactor containment buildings of APR 1400
Fatema Al Muhairi2, Yongsun Yi1, Andreas Schiffer1
1Federal Authority for Nuclear Regulation; 2Khalifa University of Science and Technology
The aircraft impact on reactor containment buildings (RCBs) in nuclear power plants has been one of the major concerns since it may cause the release of radioactive materials to the environment. In this study the impact of a commercial aircraft (Airbus A320) on RCBs of APR 1400 was investigated using finite element analysis (FEA). A new approach was developed for calculating the temporal profile of the dynamic pressure applied on the RCB surface during the impact, taking into account the change of the aircraft’s cross section during crushing. The calculated pressure vs. time history was applied on a three-dimensional RCB model developed using a commercial FE code (ABAQUS), and the dynamic response was determined. Compared to previous studies on this subject, this work goes a step further in the analysis by analyzing the effect of aging on the impact response of an APR1400 RCB. Three degradation mechanisms were considered in modeling the aging conditions of the containment, which are liner corrosion, rebar corrosion and pre-stress loss of tendons. In the simulations, the aircraft impact was analyzed for aircraft speeds in the range of 215 - 300 m s-1, and three degradation conditions were simulated: unaged, 25% degradation and 50% degradation. The results showed that the unaged and 25% degraded RCBs were able to withstand the impact load of an Airbus A320 aircraft without liner or rebar failure for impact velocities as great as 300 m s-1. It was also found that the RCBs could fail by an aircraft with 300 m s-1 speed when they were degraded by 50%, which are clearly unreasonable conditions. Although this study showed that aged RCBs could withstand severe aircraft impact, it is suggested that the degradation of RCBs by aging should be evaluated and monitored over the service period.
Electrochemical Behavior of Carbon Steels Under Simulating Containment Liner Plate Environments
Won-Jun Choi, Chi Bum Bahn
Pusan National University
Containment Liner Plate (CLP) of containment in nuclear power plants is made of carbon steels and plays an important role for the safety of nuclear power plants. It behaves as a concrete mold during construction and as a barrier during operation in order to prevent the leakage of radioactive materials in case of accidents. However, since early 2000s, the corrosion occurring at the interface between CLP and concrete has been reported worldwide. The CLP corrosion was also detected in Korean nuclear power plants recently. The CLP corrosion may be affected by various environment factors, such as pH, chloride ion concentration, oxygen concentration and humidity. However, the environmental effects on carbon steel corrosion under simulated CLP conditions have not been studied systematically. Therefore, this study investigated the transition behavior from passive to active corrosion of carbon steels immersed in saturated Ca(OH)2 solution according to the change in pH or chloride ion concentration by using various electrochemical techniques. The corrosion rates estimated from the polarization tests were compared with them from long term immersion tests. The surface analysis was also conducted to determine the morphology of oxide films formed in each environment. These results showed that the depassivation of carbon steels in simulated CLP pore solution can occur when the solution pH becomes less than 10 and the chloride ion concentration becomes higher than a several hundred of ppm. The results of this study are expected to be used as basic data for understanding the CLP corrosion and developing maintenance strategy.