Abstract:

In order to study thermal behavior characteristics of natural circulation of the system and related equipment's safety, a PRHRS thermal model of sodium-cooled reactor was established based on coupling of energy balance and flow balance. Then, influence mechanism of passive characteristics on system was explored, including potential difference and density difference. Finally, the model was verified with experimental results of PFBR, and influence laws of the number of tube passes, fin thickness, chimney diameter, and air door opening degree on thermodynamic cycle were clarified. The results show that along with increase of tube passes, heat transfer coefficient of air heat exchanger (AHX) decreases by 13.6% while pressure drop increases by 66.4%, and the system's heat transfer performance is better when the number of tube passes smaller. When inner diameter of exhaust chimney or fin thickness increases, the coefficient and pressure drop increase while heat transfer coefficient per unit pressure drop decreases, and there is an optimal solution in the design. Reducing area of inlet air door can effectively increase operating temperature of equipment and heat transfer effect of system in extreme low temperature conditions, which ensures safe operation of the system.

Key words: sodium-cooled reactor, passive residual heat removal system (PRHRS), prototype fast breeder reactor (PFBR), natural circulation, flow balance