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.
Authors:R. Brodzinski, R. Craig, W. Hensley, E. Lepel, R. Seymour, and J. Smart
A pilot plant operation at the Savannah River Site will remove 90Sr, 137Cs, and transuranics from a high-level liquid waste stream prior to encapsulation in a Saltstone Facility. Monitors are required to determine the concentrations of all radionuclides, including transuranics, in real-time on this processed waste stream. A neutron counter used to measure the concentration of each actinide isotope present in the stream is described. The neutron counter assembly consists of nested annular layers of shielding, reflectors, detectors, and moderators. On-line, live-time system control and calibration is provided by a time-tagged neutron source embedded in the moderator assembly.