It is important to study the thermal-hydraulic safety issues of the fuel assembly during the transportation in the fuel transfer tube. The flow and heat transfer mechanism is complicated when cooling the fuel assembly by natural circulation in the transfer tube. After analyzing the flow field in the transfer tube, the position of highest surface temperature is determined. The test facility was designed by the sampling the high temperature zone. A set of similarity criterion was developed for distortion analysis of the test facility. The analysis results show that the test facility is conservative to evaluate the thermal-hydraulic safety of the assembly.

During the refueling of PWR, the spent fuel assemblies are transferred from the reactor building to the fuel building through an underwater tube. The heat transfer characteristics of the spent fuel assembly in the top-corner area of the carrier with poor heat transfer conditions is important for the safety design. Experiments were carried out and single phase natural convection and pool boiling heat transfer coefficients of the three fuel rods in the top-corner area of the carrier under different heat flux was measured and obtained. The new correlations were presented. The results can provide a reference for evaluating the thermal safety state and the maximum surface temperature of the fuel assembly during the transportation process in future engineering applications.