Development of a Package of Codes for Radiation Safety Analysis in Severe Accidents at NPPs with VVERs

Modern regulatory documents impose strict requirements for substantiation of NPP safety in severe accidents, which cannot be satisfied using conservative approaches and require development of new realistic models. This article describes the approach to analysis of radiation safety of NPPs with VVER reactors in severe accidents, including fuel melting, developed and applied at the National Research Center Kurchatov Institute: phenomenology of fission product behavior in severe accidents, description of approaches to modeling fission product behavior, and description of codes developed at the National Research Center Kurchatov Institute for modeling fission product behavior in severe accidents. The final part of the article presents the results of modeling fission product behavior for the accident scenario “double-sided guillotine break of the main circulation pipeline with simultaneous complete blackout” for the AES-2006 project.