A study on self-terminating behavior of sodium–concrete reaction

Abstract

ABSTRACTA sodium–concrete reaction (SCR) is one of the important phenomena to cause the structural concrete ablation and the release of hydrogen (H2) gas in the sodium (Na) leak accident. In this study, the long-time SCR test had been carried out to investigate the self-termination mechanism under the condition to keep the temperature of Na on the concrete more than the reaction threshold temperature during 24 hours. The test results showed the SCR terminated by itself even if enough amount of Na remained on the concrete. In addition, quantitative data were collected on the SCR terminating behavior such as the temperature, the concrete ablation depth, the H2 generation behavior and the concentration profiles of Na, silicon (Si), aluminum (Al) and calcium (Ca) in the reaction products after the test. In the concentration profiles, the calculation by the sedimentation diffusion model of the steady state was comparable with the experimental results. Though the reaction products were suspended by H2 bubbling and Na ablated the concrete surface with the high H2 generation rate, the reaction products gradually settled down with decreasing of the H2 generation rate. Therefore, the Na concentration decreases at the reaction front with time and the SCR terminates of itself.