Flashing-driven natural circulation characteristics analysis of a natural circulation integrated pressurized water reactor

In this paper, the simulation model of a flashing-driven natural circulation integrated pressurized water reactor is established based on RELAP5/Mod3.4 code. The distinctive characteristics involved in the reactor, such as flashing-driven natural circulation and self-pressurization, are revealed. Based on the thermal-hydraulic characteristics of the reactor, the operation scheme that maintains both core outlet temperature and steam pressure constant is determined. A temperature-pressure joint control strategy is preliminarily determined. Based on the established reactor model, the thermal-hydraulic characteristics of the IP100 reactor at different thermal load are analyzed. The results indicate that, at lower load, the onset of flashing will move downwards and the coolant flow rate decreases, while the core inlet temperature is higher. However, the mutual coupling effect leads to the thermal-hydraulic parameters of the reactor non-linearly varies with the needed load. In the secondary loop, the steam temperature is higher at lower load. Furthermore, the effect of main system parameters is analyzed and the criteria for reactor operation parameters are discussed. The obtained research results are significant for deeper understanding the thermal-hydraulic performance of the flashing-driven NC-IPWR.