Improves the stability of containment leakage rate in constant pressure method by linear fitting analysis model

• The linear fitting theoretical model developed in this study is validated and can be used for leakage rate analysis. • This study found a strong coupling relationship among the standard-condition gas volume inside the containment vessel , humidity change compensation volume and temperature change inside the containment vessel. • This study develops a theoretical model for calculating the leakage rate by using the linear fitting analysis model. The constant pressure method for measuring the leakage rate of containment in nuclear power plants is of great significance in high leakage and low-pressure plant environments for its simple testing process, short testing period and high reliable results Therefore, conducting research on the constant pressure method for measuring the leakage rate of containment in large spaces is of great significance. In order to explore a more stable constant pressure method for analyzing the leakage rate of containment, this study develops a theoretical model for calculating the leakage rate of containment by using the Linear fitting analysis model. In the study, many different volumes of containment vessel simulation bodies are used for experimental verification and application research, and the leakage rate data calculated by linear fitting method and mean analysis method are compared. Results show that the leakage rate fluctuation ratio of the Linear fitting method decreases by 51%, and the uncertainty decreases by 87%. Research has confirmed that the Linear fitting method has good stability, high reliability, and low sensitivity to the environment. Based on above advantages, the Linear line fitting analysis model proposed in this study can further support the engineering application of the constant pressure method for measuring the leakage rate of containment.