Dynamic response characteristics of DHRS in small pressurized water reactor under SGTR accident

摘要: Small modular reactors (SMRs) are considered a promising direction for the future development of nuclear power generation due to their enhanced safety, lower initial costs, shorter construction periods, and flexible deployment options. Some typical reactors ensure robust performance during both normal operation and accident scenarios by employing passive safety mechanisms. To further understand the capabilities of these passive safety systems, based on the NuScale integral pressurized water reactor, a simulation model was developed using RELAP5 code to analyze the thermal-hydraulic response characteristics of the decay heat removal system (DHRS) during a steam generator tube rupture (SGTR) accident. The results show that the decay heat removal heat exchanger (DHRHX) on the faulted side has a limited contribution to the dissipation of the core decay heat during the accident process. In contrast, the DHRHX on the intact side can independently eliminate the core decay heat and effectively control the core inlet and outlet temperatures. When the leakage in the primary loop causes the water level to drop below the baffle of the pressurizer, significant flow oscillations occur, triggering fluctuations in other parameters. Under the conservative setting of decay power, the DHRS can still effectively prevent core melting.