Study on estimation of break diameter in the small break loss of coolant accident based on NSGA-II

Abstract

The break diameter estimation in the small break loss of coolant accident (SBLOCA) is an important work in the field of nuclear safety. It can help the operators to judge the severity of the SBLOCA in time and play an important role in reducing the damage caused by the accident. In this study, a break diameter estimation model for the blowdown process of the SBLOCA is built based on the NSGA-II and the blowdown model of the pressurizer in the SBLOCA. The model uses monitoring data such as liquid level, temperature and pressure of the pressurizer during the blowdown process to calculate the break diameter in the SBLOCA. It can be analyzed from the results that the break diameter estimation model can estimate the break diameters accurately and quickly in the SBLOCA, the errors between the calculating results of the break diameter estimation model and the actual results are no more than 18.9%, and the calculation time of the model is less than 310 s. When the calculation process reaches the maximum generation of the model, the values of fitness functions in the model approaches the minimum values.