The results of implementation of the ISTC Project “Development of a Model of the Behavior of Nuclear Fuel in the Active Stage of the Chernobyl Accident” are summarized. The project work was jointly undertaken by the Russian Research Centre Kurchatov Institute (RNTs KI) and Nuclear Safety Institute, Russian Academy of Sciences (IBRAE RAN). The aim of the project was to systematize a huge amount of data on lava-like fuel-containing materials (LFCM), collected over the 20 years of research work at the Shelter, into database and to develop a model of LFCM formation and spread during early post-accident days. The model will be helpful in producing recommendations on accident prevention and promote development of the best technologies for lava removal, thereby reducing the financial expenses and dose burden. Also, with the model developed, the results of the virtually unique “experiment” with the nuclear fuel of the Unit 4 reactor, organized on a huge scale, can be used for finding solutions to the general nuclear safety problems.