Uncertainty of Uranium Mass Measurement by Active Neutron Multiplicity

Abstract: Recently, the international society pays more and more attention to nuclear material protection,control and accounting. The focus on the material unaccounted for (MUF) is enhanced. The uncertainty assessment of uranium mass measurement plays an essential role in estimating the production of uranium. Due to the relatively weak radioactivity of uranium, the active neutron multiplicity counting (ANMC) method is usually applied to assess the mass of uranium material. In this paper, the relations and parameters between the masses of the uranium objects and the features of the ANMCs are formulated by fitting the simulated results of different sets of uranium shells. The result indicates that,each mass of the objects could be obtained by analyzing the ANMCs of different orders. In order to study the effects of the detection system settings on the mass estimation, the propagation of the aleatoric and epistemic uncertainty of the method is quantitatively studied by the simulations with different detection onditions. The optimized settings of source intensity and detection coincidence gate width, which result in the minimal uncertainty of the mass estimation, are obtained for the simulated detection system.