Study of space-energy effects in a subcritical reactor within a time-dependent multi-group 1-dimensional diffusion approach - 15478

The GUINEVERE facility hosted at the SCK-CEN site in Mol (Belgium) couples the fast subcritical lead reactor VENUS-F with an external neutron source provided by interactions of deuterons delivered by the GENEPI-3C accelerator and a tritiated target located at the reactor core center. Part of the experimental program is devoted to the study of subcriticality monitoring techniques. It includes the analysis of Pulsed Neutron Source experiments using the so-called Area Method technique which is based on Reactor Point Kinetics. Experimental results show that the extracted reactivity depends on the detector position inside the reactor. A time-dependent multigroup diffusion approach using a simplified description of the VENUS-F reactor is developed to compute correction factors which should allow one to overcome the shortcomings of the Area Method technique. Preliminary results are very promising since the application of the correction factors leads to an overall reduction in the spread of the area ratio reactivity measurements. (authors)