DESIGN OF A NEUTRON DETECTOR ARRAY FOR SNM OPTIMIZED BY RADIATION TRANSPORT METHODS

摘要

The research work presented here includes our efforts to develop a useful neutron detection device using He-3 detectors, a standard neutron detection methodology widely used in homeland security applications. The design of a He-3 neutron spectroscopy system, simulated entirely via computational methods, is proposed to resolve the spectra from Special Nuclear Materials (SNM) neutron sources of high interest. We incorporate a unique ability to effectively perform robust large-scale radiation transport simulations for SNM detection, using parallel computing methods. To demonstrate our methodology, we present the optimally detected spectral differences between SNM materials (Plutonium and Uranium), metal and oxide, using ideal filter materials. Specific focus was made to establish the limits of He-3 spectroscopy using ideal filter materials. The proposed design was then determined by replacing ideal filters with real materials, and comparing reaction rates with similar data from the ideal material suite. In our approach, we considered various configurations of moderating and attenuating materials placed around neutron sensitive detectors with a goal of isolating different parts of the neutron spectrum. To accomplish this, neutron transport simulations were performed among a suite of moderators and detectors in a "transport optimized" detector array; this enabled an optimum neutron interactions to facilitate positive detection and characterization of the incident neutrons.