It is proposed to use 14 MeV neutrons tagged by the associated particle neutron time-of-flight technique (APnTOF) to identify
the fillers of unexploded ordnances (UXO) by characterizing their carbon, nitrogen and oxygen contents. To facilitate the
design and construction of a prototype system, a preliminary simulation model was developed, using the Geant4 toolkit. This
work established the toolkit environment for (a) generating tagged neutrons, (b) their transport and interactions within a
sample to induce emission and detection of characteristic gamma-rays, and (c) 2D and 3D-image reconstruction of the interrogated
object using the neutron and gamma-ray time-of-flight information. Using the modeling, this article demonstrates the novelty
of the tagged-neutron approach for extracting useful signals with high signal-to-background discrimination of an object-of-interest
from that of its environment. Simulations indicated that an UXO filled with the RDX explosive, hexogen (C3H6O6N6), can be identified to a depth of 20 cm when buried in soil.