Abstract
The first version of the complex computer code COREMELT-2D for calculating in a two-dimensional geometry the nonstationary neutron-physical and thermohydraulic processes taking account of coolant boiling, melting of fuel elements and mixing of melted components of a fast-reactor core has been developed. The code consists of a thermohydraulic module COREMELT and the neutron-physical module RADAR. COREMELT implements a multicomponent and multiphase thermohydraulics model in R-Z geometry in the porous body approximation. RADAR solves a multigroup neutron diffusion equation in R-Z and X-Y geometry. In the RADAR module, a modified TRIGEX program with a built-in CONSYST module, associated with the BNAB-93 group-constants library, is used to prepare the dynamical neutron constants. A test calculation of a serious accident due to loss of system and reliable power with all emergency protection organs of the reactor failing simultaneously is performed for the BN-1200 design using the complex program developed. The results are compared with previous calculations of the same accident performed using a COREMELT version with a point model of neutron kinetics.