Results of study in long-term properties of austenitic steels in liquid sodium

The long-term creep properties as affected by liquid sodium were investigated of austenitic chromium-nickel steels used for the manufacture of fast reactor steam generators. Tests proceeded for 102 to 104 hours at 550, 600 and 650 degC. For maintaining the desired life of pipe fittings and components of 30 years, ie., 2.63x105 hours, the permissible value of long-term creep strength was shown to be 127 MPa. Extrapolation of the results to a value of 105 hours gave the permissible stress level of about 147 MPa. (J.B.)