Popis: |
Numerous experimental observations on the carburization-decarburization behavior of austenitic stainless steels in hightemperature flowing sodium have been reported; however, quantitative predictions of carbon diffusion in the steels under specific environmental conditions have been difficult. A mathematical analysis for the process has been developed that incorporates (1) the thermodynamic and kinetic information for carbon in the alloys, (2) the thermal-mechanical treatment of the material (solution annealed versus cold worked) that influences the microstructure, and (3) the carbon concentration in sodium and its dependence on sodium-system parameters. Carbon concentrationdistance profiles in Types 304 and 316 stainless steel were generated as a function of time, temperature, and carbon concentration in sodium and compared with experimental data. The analysis was used to evaluate the carburization -- decarburization behavior of Type 316 stainless steel fuel cladding exposed to sodium and to develop carbon-diffusion profiles in Type 304 stainless steel intermediate-heat-exchanger piping upon exposure to primary- and secondary-system sodium for periods to 30 y. (auth) |