Timely detection of HEU is one of the greatest challenges in homeland security applications, especially if any amount of shielding material is present. The specific activity of spontaneous 35U neutron emission is two orders of magnitude lower than that or 238U and six orders of magnitude lower than that of 240Pu. However, 235U has a sizable cross-section for the (n,f) reaction that can be exploited through interrogation with neutrons. In this work, AmLi sources were used to interrogate kilogram-scale masses of HEU at the Device Assembly Facility on the Nevada National Security Site. The response was recorded using the dual particle imaging system (DPI) developed at the University of Michigan, which is a combined Compton and neutron-scatter camera capable of spatial and spectral characterization of nuclear material. The response time of the liquid scintillators used in the DPI is on the order of nanoseconds, which is on the same time-scale of the fission chains induced in the HEU. This capability presents the possibility to directly analyze the fission chain dynamics to characterize the multiplication of the HEU samples. Results will show the discrimination of different quantities of HEU using the DPI.