Verification of Simplified Primary and Secondary Models of Small Pressurized Water Reactors for Analysis of Passive Autonomous Load Following

Abstract A novel reactor dynamics methodology for passive autonomous load following (PALF) of small pressurized water reactors (small PWRs) is proposed. This methodology enhances steam generator (SG) modeling by subdividing the heat transfer process into two stages: “primary to metal” and “metal to secondary,” A secondary circuit model based on linear regression captures the steam pressure and turbine power, thus avoiding the need for detailed modeling of turbine or valve dynamics. To enhance the accuracy of the simulation, the methodology incorporates Mann's model and the delay time for coolant flow. The methodology is validated using experimental data from reference studies within a ±5% load disturbance range. The simulated values of indicators such as primary power and coolant temperature are highly consistent with experimental measurements, while the secondary circuit steam pressure and turbine power are estimated with reasonable accuracy. This work also provides new insights for future PALF feasibility studies, such as system reliability issues caused by the reduced heat transfer capacity of SGs. Overall, the proposed method balances accuracy, computational efficiency, and ease of implementation, laying the foundation for a wider range of load regulation scenarios and long-term safety assessments.