Carburization of stainless steel clad by uranium-plutonium carbide fuel

Abstract

Carburization of stainless steel clad by the fuel in fast reactor fuel pins, containing uranium-plutonium mixed carbide, would adversely affect the mechanical properties of the clad. The extent of carburization depends on the relative carbon potentials of the fuel and the clad. The measurement of the carbon potential of stainless steel as a function of temperature in the operating range of the fuel pins was recently reported from this laboratory. The method is based on equilibration of SS specimens with liquid sodium while simultaneously monitoring the carbon potential of sodium with an electrochemical carbon meter. In the present work, the same procedure was extended to the fuel and results obtained with both UC and (U,Pu)C in the range of 840 to 960 K are reported. Using the present results and the earlier data on carbon potential of SS, the possibility of clad carburization is analysed.