[en] General data on radioactive releases of the damaged Chernobyl NPP unit (ChNPP-4) are given. The method of its obtaining is described. These data are analyzed and revised on the basis of investigation results obtained in the USSR and abroad after August 1986 on the issues of the accident course and consequences. Fission and neutron activation products inventory data in the ChNPP-4 core before the accident are presented including isotopes of U and transuranic elements. Dynamics, physical and chemical processes of the radioactive releases formation are considered including urgent mitigation measures. Major scientific on-side and of-side investigations planned and performed are described