GASFLOW: The Theoretical Model to Analyze Accidents in Nuclear Containments, Confinements and Facility Buildings

Abstract

This report documents the governing physical equations for GASFLOW, a finite- volume computer code for solving transient, three-dimensional, compressible, Navier-Stokes equations for multiple gas species. The code is designed to be a best- estimate tool for predicting the transport, mixing, and combustion of hydrogen and other gases in nuclear reactor containments, confinements, and other facility buildings. An analysis with GASFLOW will result in time-dependent gas species concentrations throughout the structure analyzed, and in the event of combustion the pressure and temperature loadings on the walls and internal structures. GASFLOW can model geometrically complex containment systems with multiple compartments and internal structures. It can calculate gas behavior of low-speed buoyancy-driven flows, of diffusion-dominated flows, and during deflagrations. The code can model condensation heat transfer to walls and internal structures by natural and forced convection; chemical kinetics of combustion of hydrogen or hydrocarbons fuels; and fluid turbulence. Heat conduction within walls and structures is considered one-dimensional.