Modelica Modeling and Simulation for a Micro Gas-Cooled Reactor

Samll size and highly integral micro nuclear reactors which have broad energy advantages in the application of ocean, land, space, and sky, become a hot research topic in the international nuclear industry recently. Compared with a large-scale pressurized water reactor nuclear plant composed of a large amount of subsystems, the integral micro nuclear reactor has fewer subsystems but its subsystems are tightly coupled due to the constraints of the volume and weight. To handle the complexity aroused from this coupling issue and to better predict the reactor dynamic behavior, it is necessary to perform the system simulation across multiple disciplines and domains. In this paper, Modelica language was used in the system modeling and simulation of a micro gas-cooled reactor. The Modelica model was self-developed by China Nuclear Power Engineering Company and the MWorks developed by Suzhou TongYuan was chosen as the simulation platform. Two simulations of a conceptual micro gas-cooled reactor design were carried out, including an extreme accident scenario and a normal load-following operation scenario. The simulation results showed that the reactor has good inherent safety even under the extreme accident, in which the reactor shutdown can be achieved only by the negative reactivity result from the increase of core temperature and the fuels were not damaged since the decay heat was removed by passive air cooling from outside of the reactor pressure vessel. The reactor also has good load-following performance, which can be achieved by simply adjusting the helium inventory (or pressure) and the control rod position, while the core temperature and power generation efficiency kept constant.