SOCRAT: The System of Codes for Realistic Analysis of Severe Accidents

Abstract

For a long time in the Russian Federation the computer code for analysis of severe accidents is being developed. The main peculiarity of this code from the known computer codes for analysis of severe accidents at NPP such as MELCOR and ASTEC, is a consequent realization of the mechanistic approach for modeling of the melt progression processes, including beyond design basis accidents with the severe core damage. The motivation of the development is defined by the new design requirements to the safety of nuclear power plants with the improved economic factors, by the modernization of existing NPPs, by the development of instructions to the accident management and emergency planning. The realistic assessments of Nuclear power plants safety require usage of the best estimate codes allowing description of the melt progression processes accompanying severe accident at the nuclear installation and behavior of the containment under abnormal condition (in particular, rates of the steam and hydrogen release, relocation of molten materials to the concrete cavity after failure of the reactor vessel). The developed computer codes were used for the safety justification of NPP with the new generation of VVER type reactor such as Tyanvan NPP in China and Kudamkulam NPP in India. more » In particular using this code system the justification of the system for hydrogen safety, analysis of core degradation and relocation of the molten core to the core catcher used for the guarantied localization of the melt and prevention of the ex-vessel melt progression. The considered system of codes got recently name SOCRAT provides the self consistent analysis of in-vessel processes and processes, running in the containment, including melt localization device. In the paper the structure of the computer code SOCRAT is presented, functionality of the separate parts of the code is described, results of verification of different models of the code are also considered. (authors) « less