In this application, based on the CGN_NHR1.0 model library, an overall simulation model of the intermediate loop of the low-temperature heating reactor was built using a visual drag-and-drop modeling method. The multi-domain coupling and collaborative simulation
verification were carried out using the MBSE method. The typical working condition selected was the step reduction of rated full power (100% FP) to 70% FP load disturbance. Oriented by the SysML functional requirements, a joint simulation framework for reactor physics, thermal-hydraulic, and control systems was constructed. The simulation conditions were divided into two stages: the first 100 seconds of the system maintained a steady state operation, and at the 100-second moment, a 70% FP step load reduction disturbance was applied. The simulation results showed that the various thermal-hydraulic parameters of the intermediate loop could return to stability within 450 seconds after the disturbance occurred, and the dynamic response performance of the system control was better than the design-expected indicators. Research has confirmed that the SysML-Modelica joint modeling approach is applicable to the design and analysis of complex nuclear energy systems. The "requirement driven - functional mapping - dynamic verification" closed-loop verification mode constructed in this study can provide reliable theoretical and methodological support for the digital design and development of nuclear energy equipment.

While Modelica has become a standard for multi-domain modeling in various complex engineering fields, professional and systematic model libraries specifically tailored for the nuclear power sector remain scarce. To bridge this gap, this paper presents the development of a specialized Modelica fluid component library for Small Modular Reactor (SMR) systems. Serving as a critical module within the broader CGN_NHR library, this framework bridges the gap between fundamental fluid mechanisms, equipment-level modeling, and system-level assembly. We detail the library’s architecture, design philosophy, and the mathematical formulation of its core components. To verify its validity and reliability, a systemlevel model was constructed and benchmarked against the industry-standard RELAP5 model. Comparative results confirm that the proposed library offers high efficiency and accuracy, establishing a robust technical foundation for the rapid design, simulation, and verification of nuclear power systems.

As the pivotal equipment connecting the primary and secondary loops of pressurized water reactor nuclear power plants, the dynamic thermo-hydraulic characteristics of the nuclear steam generator are directly related to the safe and stable operation of the unit. However, traditional modeling approaches suffer from poor versatility and low efficiency, making it difficult to meet the R&D demands for diverse application scenarios and iterative optimization. Addressing these bottlenecks, this paper proposes a modular modeling and dynamic simulation method for nuclear steam generators based on the Modelica language. First, based on a hierarchical modeling approach, component-level models covering plena, pipes, heat structures, steam-water separators, and feedwater plena are constructed to achieve free configuration and visual simulation modeling. Second, according to the operating principles and structure of the nuclear steam generator, a complete dynamic simulation model is assembled using these component-level models. Finally, the established model is validated against the RELAP5 code to verify the effectiveness and reliability of the proposed method. The results indicate that the Modelica-based steam generator simulation model combines high accuracy with high efficiency, providing significant technical support for the rapid design and verification of nuclear power systems.