GAMMA-RAY IMAGING SPECTROMETERS FOR NUCLEAR MATERIAL ACCOUNTING

The process of extracting useful fissile material for commercial benefits or even disposal from spent commercial nuclear fuel or decommissioned nuclear weapons is a critical aspect of ensuring global nuclear security and safety. The current tools used to ensure that a facility prevents diversion or unplanned accumulation of fissile material are relatively rudimentary and require a great deal of human effort and dose, as a worker must manually measure every point along a pipe or subsystem to determine the activity level of each isotope within. H3D, Inc. has already introduced the Polaris-H gamma-ray imaging spectrometer, based on 3D position sensitive CdZnTe crystals, to the commercial nuclear power operators to help them identify unexpected sources of radiation. However, the device is not capable of accurately quantifying the activity of each isotope within a pipe, especially at the lower energies of interest in the fuel cycle. This work proposes a new detector based on the principles of the Polaris-H but optimized for high resolution coded aperture imaging and quantification of fissile material within a pipe. An improved readout system will be used to improve the energy and spatial resolution of the Polaris technology and an optimized coded aperture will be designed to address this particular scenario. The phase I effort will begin with simulations to determine the ideal mask and detector geometry to characterize the activity along a pipe. Once the mask and detector design has been selected then a readout system with improved spatial and energy resolution will be built to meet the geometric guidelines derived from the simulation results. This proof-of-concept system will then be tested with laboratory sources to validate the simulations and make determinations on the feasibility of such a product. If the simulations and measurements indicate that it is possible to quantify the activity of each isotope along the pipe with acceptable levels of confidence then a variety of commercial applications will follow. For inspectors of nuclear facilities it will allow quicker and easier characterization of the facilities. For plants that are processing fuel it will allow them to monitor their processes more regularly and accurately with less dose to their employees. For customers in the commercial nuclear power industry they will be able to measure contamination within their pipes and other subsystems at a lower cost.