Study of the VVER1000 reactor core fuel assemblies reaction to mass flux changes, caused by lose of coolant accident, by means of the sound effect

The article aims in the studying of thermal-hydraulic simulation of the VVER-1000 reactor core fuel assemblies’ reaction to the mass flux changes which are caused by the lose of coolant accident and its sudden pressure drop. The analysis of mentioned accident is performed in concise periods (mili second) by the use of the sound effect. Time-related thermal-hydraulic equations were analyzed by the method of a compressible fluid in a single heated channel and were evaluated by the results of the mentioned transient, in a PWR reactor. The mentioned transient was simulated in RELAP5 code and results were compared to the previous ones. Then, 28 reactor fuel assemblies were studied, considering the 1/6 symmetry of VVER-1000 reactor and unique features of every assembly. Mass flux drop was happened the end of the channel, after a few seconds. It was observed that mass flux is at dependent on the role of every assembly in the production of core heat power. The acoustic effect reveals some of the perturbations in mass flux changes, considering every fuel assembly features.