[en] This report presents an assessment of the quantity parameters influence of the Common Cause Failures (CCF) on the final result from the Probabilistic Safety Analysis (PSA) performed for the Kozloduy NPP Units 3 and 4. The monoparametric model 'β-factor' is used for CCF modeling. This analysis includes assessment of the 'β-factor' change influence on the final result. The obtained results show high sensibility of the reactor core damage frequency to the CCF parameters of High Pressure Injection Pump (HPIP). This frequency increases with 78%, and the CCF relative share of HPIP - over 10 times in approximately 12 times rise of the CCF probability. The unpreparedness of the technological systems of the nuclear reactors is basically defined by CCF and their equipment. As a conclusion the authors consider the investigations of the final result sensibility to the quantitative parameters of the CCF give the base for engineering assessment of the right interpretation of the results from the probabilistic safety analysis