Research on Characteristics of U-tube Backflow in Natural Circulation Steam Generator under Ocean Conditions

Abstract

When the pressurized water reactor is in natural circulation, reverse flow may occur in the U-tube of the steam generator, which will increase the flow resistance of the primary circuit and decrease the flow of natural circulation, which will adversely affect the safe operation of the reactor. Based on the RELAP5 program, the additional force model under ocean conditions and the spatial coordinate solution model of the control body are established, all U-tubes of the steam generator are modeled and node division are conducted, and the steam generator under ocean conditions (inclination, undulation, swing) is calculated. The critical mass flow rate of the reverse flow and the pressure difference between the inlet and outlet of the inner U-shaped pipe are analyzed. Finally, the influence of three ocean conditions on the reverse flow of the fluid in the U-shaped pipe is analyzed. The results show that the backflow phenomenon may be changed under inclined conditions; the undulating conditions that may be encountered during navigation cannot change the backflow phenomenon; the backflow phenomenon may be changed when the sway conditions are severe.