Compatibility of steel No. 1.4970 with liquid sodium at high temperatures

Abstract The sodium corrosion and the influence of liquid sodium at 873 and 973 K on the creep strength of cladding tubes of steel No. 1.4970 was studied in a sodium loop. The corrosion and creep tests with cladding tube specimens were extended up to 10 000 h. The mass losses showed an effect of the oxygen content in the sodium loop which was controlled by means of a cold trap. The exposure to sodium caused chemical changes as losses of chromium, nickel and manganese and the carbon concentrations were increased in the outer zones of the material. The boron content of the steel was significantly reduced. Despite the changes of the chemical composition of the material, the time to the creep deformation of 1% at 973 K was not influenced by the sodium corrosion. This might be due to the carburization of the steel. All corrosion effects were only marginal at 873 K.