Analysis method on the break accident of the HTR-PM refueling line

In thermal hydraulics design and safety analysis of the HTR-PM, the THERMIX code was used to study the behavior of the helium in the primary system. Once the helium leaks from the primary loop through a break or a relief valve, it is hard to simulate the states of the leakage room with THERMIX. In this paper, the latest version of RELAP5/MOD4 was used to simulate the behavior of the helium released to the containment rooms. The heat structures with power were used to simulate the HTR-PM core. The flow rate, temperature and pressure drop in the core in steady state was compared with Thermix results. During a scram accident, both Thermix and Relap5 models were calculated to analyze the peak temperature varying in the core. After that, a RELAP5/MOD4 input deck of the HTR-PM, including the core, the primary system, the secondary loop and the containment, were developed. Based on the model, this paper studied the accident consequences of a small break on the refueling line of HTR-PM. The analysis showed that the scram function and the ability to monitor the reactor temperature and pressure after accidents will not be affected by the break. (author)