Study on Gas Relaxation Process in Leakage Rate Measurement Stage of Containment Test Based on Time Series Analysis Method

During the containment test, upon the leakage rate measurement plateau, the temperature, steam partial pressure, and other parameters of gases in the containment fluctuate and then go into the steady relaxation process. This article analyzes the criteria for reaching new steady state, the gas relaxation time, the factors that affect the relaxation process and other aspects to provide the criterion for steady state by performing steady state test via test statistic calculation. Also, this article conducts time series decomposition for various parameters involved in the relaxation process to analyze the relaxation process of each parameter separately. As seen from the study results, the relaxation time is mainly affected by the non-uniform steam partial pressure due to containment pressurization. On this basis, this study further proposes controlling the steam partial pressure imbalance trend to shorten the relaxation time of the leakage rate results.