Secondary system modeling and primary system coupled simulation using MARS-KS

Abstract

The flexibility of nuclear energy can be achieved by the load following operation and the thermal energy utilization for hydrogen production, desalination, district heating, and Thermal Energy Storage (TES). Thermal energy utilization is performed by transferring the remaining thermal energy over the energy required for electric power generation without changing the reactor power level significantly. For the Pressurized Water Reactor (PWR), it becomes possible by extracting steam from the secondary system and circulating it to a thermal energy application such as the TES system. However, the steam extraction operation affects the behavior of all thermal–hydraulic (TH) variables in the secondary system and further influences the primary system in terms of coolant temperature, reactivity, and reactor power. For thermal energy utilization, it is necessary to secure a technology that can examine the overall stability of the primary and secondary systems in a Nuclear Power Plant (NPP). In this study, based on the system analysis code MARS-KS, an NPP analysis model for SMART, a small-sized integral type PWR, was developed that can simulate major TH variables behavior in the primary and secondary systems at once. Its strength is that major components in the secondary system are modeled without any boundary conditions under matching the heat and mass balance. From the verification calculation of the steady state, it was confirmed that this SMART analysis model can predict the main TH variables of the primary and secondary systems similarly to the plant data. Furthermore, an example calculation was performed for the TES application. The analysis results show that the analysis model is sufficiently applicable to the transient calculation of the primary and secondary systems during the steam extraction operation. This analysis model is expected to be used for the development of technologies such as load following operation and thermal energy utilization in the future.