Effective delayed neutron fraction measurement in the critical VENUS-F reactor using noise techniques

This paper present the measurements of VENUS-F kinetic parameters using the Rossi-Alpha methods. The VENUS-F reactor is a zero-power reactor based in Mol, Belgium at SCK-CEN [1]: its fuel is made of metallic enriched uranium with pure lead in order to simulate the behavior of a lead fast reactor. The reactor can be operated in a sub-critical state when it is coupled with the GENEPI-3C neutron source [2]. At the beginning of 2014, a measurement campaign was performed in the critical state in order to estimate the kinetic parameters of the reactor. In this paper, two measurements are analyzed at two different powers (approximately 2W and 30W) with 7 different fission chambers (with a 235-U deposit that varies from 1g to 10mg). All the correlation functions needed for the Rossi-Alpha method have been built for each possible set of two detectors for the two power levels and values of the effective delayed neutron fraction obtained are then compared. Experimental results show the importance to operate at a very low power. The final value for the effective delayed neutron fraction is finally estimated to be (730 ±11) pcm and the prompt neutron generation time is estimated to be equal to (0.41 ± 0.04) μsec.