Computational Analysis of Pressure Loading and Impulse Distribution in the Reactor Cavity During the Process of Ex-Vessel Steam Explosion

In order to investigate the magnitude and distribution of pressure and impulse in the reactor cavity during the process of fuel-coolant interaction includes both the premix and steam explosion, a three dimensional multiphase fluid simulation code MC3D has been used based on the structural and environmental characteristic of the sever accident state of 1000 MW level PWR Linao Nuclear Power Station Phase II with the consideration of both pressure variation and impulse variation. The results indicate that the process of premixing has a low level pressure variation with a long duration and the affect of this process is negligible. On the contrary, explosion stage creates a instant and sharp pressure pulse which threatens the integrity of the reactor cavity structure. In addition, the mass of the melting drop contacts the coolant all over the calculating grids has a significant effect regarding the magnitude of the impulse created by steam explosion.