Analyzing Elemental Composition Using Nrta With An Isotopic Neutron Source

Farheen Naqvi - Massachusetts Institute of Technology
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Neutron resonance transmission analysis technique (NRTA) uses the resonance phenomenon to identify the isotopic composition of unknown materials. Several mid-Z to high-Z elements have discrete energy levels 1 eV- 100 eV above the neutron separation energy. In this energy range, the transmission spectra of epithermal neutrons for these elements show unique resonant signatures due to which NRTA has found its applications in the field of geology, warhead verification and spent fuel analysis. Presence and quantification of special nuclear materials such as U-235, U-238, Pu-239 and Pu-240 with NRTA is being explored, however its application is currently limited due to the availability of calibrated, strong neutron sources only at large experimental facilities. To alleviate this limitation, we have studied the feasibility of doing NRTA with a mobile, small-scale setup using an isotopic neutron source. Time-of-flight is measured between two detectors to provide the energy of the transmitted epithermal neutrons. Proposed experimental geometry, measurement times and acceptable source count rates investigated using Monte Carlo based GEANT4 code will be presented. Preliminary results on resolution and background levels in the transmitted energy spectrum will be discussed to demonstrate confidence for future experiments.