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

Abstract

Abstract-Parametric studies using numerical simulations are being performed to assess the performance capabilities and limits of active neutron interrogation for detecting shielded highly enriched uranium (HEU). Varying the shield material, HEU mass, HEU depth inside the shield, and interrogating neutron source energy, the simulations account for both neutron and photon emission signatures from the HEU with resolution in both energy and time. The results are processed to represent different irradiation timing schemes and several different classes of radiation detectors, and evaluated using a statistical approach considering signal intensity over background. This paper describes the details of the modeling campaign and some preliminary results, weighing the strengths of alternative measurement approaches for the different irradiation scenarios.

Development of a new multiplying assembly for research, validation, evaluation, and learning

“…However, ample access to high performance computing resources can augment parameter-bounding experiments to perform parametric analysis of variables not accessible through experiments, and to exhaustively carry-out sensitivity analyses for varying different parameters singly and in combination. [10] In a complimentary fashion, for computationally focused research efforts key measurements performed during experimental efforts are critically important for validating the accuracy and legitimacy of using simulation codes and associated post-processing algorithms for analysis and interpretation. [11] An important subset of activities that takes place at INL's ZPPR facility is testing to evaluate the performance and use of commercial instrumentation designed to detect and characterize radioactive materials.…”

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

“…This approach, using the MCNP5 and MCNPX radiation transport codes, has been presented previously. [30][31][32] These large-volume shields were not chosen to be specifically representative of particular scenarios (cargo containers, vehicles, buildings, etc.) but rather to provide a generalized representation of several shield configurations that can be very difficult for both passive screening and ANI to deal with (to successfully detect HEU).…”

“…[30] x Interrogation source: o DD10 6 : Deuterium-deuterium (DD-) ENG (E n = 2.5 MeV) with yield of 10 6 n s o Wood, 0.45 g cm -3 o Polyethylene, 0.95 g cm -3 o Aluminum, 0.6 g cm -3 o Steel, 0.6 g cm o The interrogation source was always centered on the HEU location at the face of the bulk shield. DD-ENGs with a yield of 10 6 n s -1 and DT-ENGs with a yield of 10 8 n s -1 are currently available.…”

“…The detector array was located 0.1 m from the outside of the shield area, 0.1 m to one side of the ANI source. [30] x Ideal neutron detectors: To allow a more universal comparison, the 3 He detector results from the 'concpetual' detector were also scaled to represent an idealized detector with a 0.25 m 2 detection area with 25% intrinsic efficiency for fission spectrum neutrons.…”

“…The simulations calculated the energy-and timedependent neutron and gamma-ray flux values at a measurement position 0.1 m from the outside of the shield area, 0.1 m to one side of the ANI source. [30] For neutron detection an energy-dependant efficiency function, corresponding to the measured response of a 7.62-cm u 7.62-cm Ø liquid scintillator cell filled with EJ-309 scintillator, was applied to the flux tallies. [33] For photon detection a simplified scaling efifeicny of 25% was applied for all events with photons more than 3 MeV in energy.…”