[en] Major experimental techniques designed for simulating fast reactors using BFS critical assemblies are described. At greater length given is a description of one of the largest facility, BFS-2, its design and equipment, and fuel assemblies used. Methods of measuring reactivity, cross section ratios, neutron spectra and importance are considered. Much attention is paid to the evaluation of data, such as extrapolation of measured reactivity coefficients to zero dimensions of samples and heterogeneous effects on physical characteristics