Measurements of the ratios of the average effective cross-sections of threshold 234U (n,f), 236U (n,f), 237U (n,f) reactions and average cross section of the 235U (n,f) reaction in the BTS-4 critical assembly

The ratios of the average effective cross-sections of threshold 234U8 (n,f),236U(n,f), 237U(n,f) reactions and average cross-section of 235U(n,f) reaction in the center of critical assembly (BTS-4) by solid track detectors have been measured. The target calibration measurements have been conducted on the state special standard for flux density and fluence units 14.7 Mev neutrons. A thorough analysis of measurement errors is being carried out and possibility of obtaining these values with an error of about 5% and confidence probability of 0.95 is shown. The effective cross-section ratios calculated from DRZM code of the NF-6 complex are compared with experimentally determined ones and their agreement within the measurement errors is shown. The measurements are of interest in the analysis of the used methods of the fast reactors design, systems of group constants and in the neutron spectrum unfolding