Addressing different active neutron interrogation signatures from fissionable material

Abstract

-In a continuing effort to examine portable methods for implementing active neutron interrogation for detecting shielded fissionable material research is underway to investigate the utility of analyzing multiple time-correlated signatures. Time correlation refers here to the existence of unique characteristics of the fission interrogation signature related to the start and end of an irradiation, as well as signatures present in between individual pulses of an irradiating source. Traditional measurement approaches in this area have typically worked to detect die-away neutrons after the end of each pulse, neutrons in between pulses related to the decay of neutron emitting fission products, or neutrons or gamma rays related to the decay of neutron emitting fission products after the end of an irradiation exposure. In this paper we discus the potential weaknesses of assessing only one signature versus multiple signatures and make the assertion that multiple complimentary and orthogonal measurements should be used to bolster the performance of active interrogation systems, helping to minimize susceptibility to the weaknesses of individual signatures on their own. Recognizing that the problem of detection is a problem of low count rates, we are exploring methods to integrate commonly used signatures with rarely used signatures to improve detection capabilities for these measurements. In this paper we will discuss initial activity in this area with this approach together with observations of some of the strengths and weaknesses of using these different signatures.

Estimation of the performance of multiple active neutron interrogation signatures for detecting shielded HEU

“…In most early work, research focused on choosing one type of irradiation source and one signature to be measured. [9] More recent work has recognized the value of measuring multiple signatures simultaneously. Swanekamp et al have presented compelling research about the value of using one single, intense pulse of x-rays to serve as an active interrogation source for detecting SNM.…”

Parametric evaluation of active neutron interrogation for the detection of shielded highly-enriched uranium in the field

“…Active neutron interrogation (ANI) has the capability of sensing further into a shielded assembly to detect HEU [14]- [19]. ANI involves the use of a pulsed neutron source, most often an accelerator-based electronic neutron generator (ENG), to irradiate a suspect object (e.g., shipping container, pallet, storage drum, vehicle, wall, floor, etc.)…”