Kinetics of decarburization of 2 1/4% Cr--1% Mo steel in sodium

Recent data and published data on the de-carburization kinetics of Cr–1% Mo steel in sodium from 800 to 1300°F were correlated by expressing changes in bulk carbon content of samples of different thicknesses and geometry as carbon loss per unit of surface area exposed to sodium. This parameter, when plotted as a function of the square root of time, produced straight lines consistent with the expected diffusion control of the decarburization process. New data from this investigation yielded a decarburization rate constant that was in excellent agreement with the correlation obtained from the published data. A design curve prepared from the correlation was used to predict the end-of-life carbon contents of typical steam generator tubes in sodium systems.