SENSITIVITY STUDIES ON THE NEUTRON EMISSION OF SPENT NUCLEAR FUEL BY MEANS OF THE ORIGEN-ARP CODE

摘要

SCK·CEN is engaged in Non Destructive Assay (NDA) R&D work on spent fuel elements (SFE). One of the traditional methods for the verification of the spent fuel elements is the so-called Fork detector, relying on passive neutron and gamma measurements for the assessment of the burnup of SFE. In order to better understand the principles behind total neutron counting in a "Fork-like" detection system, a significant effort was done in the past both in terms of Monte Carlo modelling and depletion and evolution code calculations. This paper focuses on the impact of some parameters of the irradiation history on the total neutron emission of a SFE. The tool used to determine the neutron emission was the ORIGEN-ARP code. The cases considered a Low Enriched Uranium (LEU) 17×17 PWR fuel with an initial enrichment of 4.5%. The burnup ranged between 5 and 70 GWd/t_U and 30 values of cooling time, from 0 up to 3 million years, were considered. The parameters that were varied were the average power level, the cooling time between cycles and the duration of the irradiation cycle. The obtained neutron emission values are presented and discussed. Conclusions on the role of the considered irradiation history parameters on the total neutron emission and on the impact of the main neutron emitters are drawn.