Simulation and Analysis for Hualong Reactor Advanced Integrated Test Facility Based on RELAP5

Abstract Hualong One and its subsequent rectors are the third-generation pressurized water reactor (PWR) and constructed by the China National Nuclear Corporation (CNNC) which possess completely independent intellectual property rights. China Nuclear Power Engineering Co., Ltd. (CNPE) designed and built an integrated test facility for the Hualong’s subsequent rectors emergency core cooling system (referred as Integrated Test Facility). The Integrated Test Facility is a large-scaled facility and designed based on the Hualong’s subsequent rectors’ safety systems, which adopts a passive safety design. The Integrated Test Facility includes main loop system, High-Pressure Makeup Tank (HPMT), Accumulator (ACC), Automatic Depressurization System (ADS), Outside Reactor Water Storage Tank (ORWST), Direct Vessel Injection (DVI) pipeline, Sump, Passive Residual Heat Removal System (PRS), Passive Containment Cooling System (PCS), etc. These systems and equipment work together to achieve passive emergency core cooling function. In this paper, a RELAP5 model is establish to analyze a small LOCA accident sequence. Simulations are conducted for five stages after the accident, including natural circulation, automatic depressurization, safety injection, and long-term sump recirculation. A 4MW core power (with operation pressure 15.5MPa, core inlet temperature 292.4 Celsius degrees, core outlet temperature 327.7 Celsius degrees) and medium pressure model was established. The emergency core cooling system operational characteristics were investigated under small break loss of coolant accident (SBLOCA). The simulation results demonstrated that the RELAP5 model can simulate the transient key system parameters accurately. This paper investigates the operational characteristics of the emergency core cooling system under different LOCA conditions, elucidates the interaction mechanisms of passive safety systems, and explores the physical mechanisms of thermal-hydraulic phenomena and processes in the integrated test facility. Based on numerical simulation analysis, the experimental data under accident conditions are obtained, thereby validating the rationality of the safety system design for the integrated test facility and the effectiveness of the accident analysis modeling method.