A generic velocity-free calculation method of the blasting wave in nuclear power plants for designing venting system

摘要

Venting system, mainly composed of bursting discs, is designed to protect the structural integrity of the cabins in nuclear power plants (NPPs). During a loss of coolant accident (LOCA), much gas is rapidly released into the cabin, forming a kind of pressure longitudinal wave (PLW) named "blasting wave" and challenge the mechanical strength of the envelope structure. Simulation of the blasting wave is meaningful for designing bursting discs. CFD is a generic method for cabins with arbitrary geometric features, which consumes much time and computing resource; There exists a mathematical model based on wave equation describing PLW, but it has never been applied in the field of nuclear reactor accident because of some bottlenecks. In this study, the mathematical model based on wave equation is transformed into a generic method of simulating PLW without solving velocity field, which is in the form of a velocity-free PDE problem with velocity-related initial and boundary conditions. The boundary condition is not Dirichlet, Neumann nor Robbin, and provides condition for one-dimensional analytical solution. The problem can also be solved by finite element method (FEM). Both solutions are validated by CFD simulation in our previous study and can be extended to higher dimensions. In engineering application, the analytical solution can be directly used if the cabin's geometry is relatively simple, while FEM solution can be used on a coarse meshing if the geometry is complex. Both applications are convenient compared with CFD method.