Impact of delayed neutron constants on reactivity effects measured in a fast reactor

Delayed neutron parameters of fast VENUS -F reactor core configurations are determined with Monte Carlo calculations using various nuclear data libraries. Differences in the calculated effective delayed neutron fraction and the impact of the delayed neutron data (6- or 8 -group precursors) that are applied in the experimental data analysis on the measured reactivity effects are studied. Considerable differences are found due to application of U-235 and U-238 delayed neutron data from JEFF, JENDL and ENDF evaluations.