LAUSR

Abstract A Subchannel Analysis Code for Annular Fuel (SACAF) capable of modeling dual-cooled annular fuel pins was developed. The coolant flow distribution was adjusted until a uniform pressure drops was formed in all the subchannels. The heat transfer fraction was determined by the criterion that the temperature of the fuel pins was continuous and a burnup-dependent fuel thermal conductivity model was incorporated into the code to analyze the effect of the thermal conductivity degradation. In this paper, the characteristics and verification of the SACAF are described. The thermal-hydraulic performance of the annular fuel was determined for the major thermal-hydraulic parameters and was compared with that of the cylindrical fuel assembly. For the same power distribution, the annular fuel exhibited a greater departure from nucleate boiling ratio (DNBR) and a much lower fuel pellet temperature than the cylindrical fuel. The fuel pin temperature profiles at different burnup levels were obtained and the effects of the thermal conductivity at different burnup levels on the temperature profile and the heat split were determined.