[en] Procedures and equipment for precise measurement and analysis of cross spectra for determining reactor parameters and analysis of reactor dynamic stability were developed in the Institute. Significant advantage of these methods is the possibility of direct application of frequency dependent response function. Measurements of response functions between system functions can be applied directly for verification of theoretical models. Evaluation of system parameters is done by comparison of measured and theoretical response functions. Measurement of response functions can be used for reactor stability study under different operation conditions even if precise theoretical description of reactor dynamics is not possible