When the primary system of nuclear reactors experiences overpressure, the overpressure discharge system can be utilized to release high-temperature and high-pressure fluid through the safety valve and downstream pipelines to achieve pressure reduction.

However, the rapid opening of the safety valve can lead to a violent fluid release, which may impose severe transient load impacts on the pipelines and the pool.

Analyzing the typical characteristics and influencing factors of the emission phenomenon can provide references for system operation and design. A systematic analysis model including the pressure vessel, pipelines, and water pool was established. The model was finely divided, with the length of the pipeline control body not exceeding 0.3 m, and the water pool was composed of multiple control bodies. The load was solved using the momentum balance method, and calculation results were compared with the EPRI/CE international test data. The established analysis model can quickly obtain the thermal response and load response during the discharge process.

The results show that during the overpressure discharge process, there is a water seal at the valve inlet and, the opening time reduction will cause the peak load on the pipelines and the water pool to increase.

A decrease in the nozzle immersion depth or an increase in the water pool cross-sectional area will result in a reduction in the peak load at the water pool.