This tutorial provides a comprehensive overview of the OpenModelica architecture and development environment. It covers the basics of the Modelica language, OMEdit GUI operations, and model compilation principles. The hands-on session will guide beginners through component library usage and drag-and-drop modeling to complete a full workflow from environment setup to simulation execution.

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.

Nuclear power systems are complex multi-disciplinary systems involving thermal hydraulics, fluid mechanics, control engineering and electrical engineering. Comprehensive performance analysis and optimization of such systems require coupled multi-disciplinary modeling and simulation. Nevertheless, co-simulation via interfaces between separate single-discipline simulation software brings numerous inherent drawbacks. Hualong One is China’s domestically developed third-generation pressurized water reactor. To accelerate system modeling and simulation efficiency, this paper independently develops the unified multi-disciplinary modeling library CGN_HPR V1.0 based on Modelica and the hierarchical modeling method, with the domestic MWorks simulation platform as the core development environment. Adopting a four-tier architecture consisting of basic, component, equipment and system levels, the library supports modular, parameterized and visual modeling for streamlined simulation analysis, and addresses the technical bottleneck of insufficient deep coupling in traditional multi-disciplinary simulation workflows. Typical operating conditions of Hualong One are modeled and simulated using the proposed library, which preliminarily verifies the validity of the Modelica-based system simulation model. The results demonstrate that the Modelica-enabled simulation framework enables seamless integration of cross-disciplinary subsystems, mitigates the difficulties in multi-disciplinary coupled simulation for nuclear power plants, and improves overall system analysis and design capacity, providing key technical support for unit safety assessment and operational optimization.