Design of a cosmic-ray muon tomography system for dry storage cask imaging

The overarching goal of this project is to develop an imaging system to monitor the content of a dry storage cask (DSC) with cosmic ray muons. The imaging technique utilizing multiple Coulomb scattering was demonstrated to be a good nondestructive assay method for high-Z materials, such as used nuclear fuel assemblies in DSCs. In this paper, we report our simulation work on the 2D and 3D muon tomography of a DSC. The Point of Closest Approach (POCA) and Maximum-Likelihood Expectation-Maximization (ML-EM) algorithms are used for image reconstruction. The reconstructed image showed good spatial resolution and good material discrimination ability, even though the detector has only 1cm by 1cm spatial resolution. The prototype design uses EJ-200 plastic scintillator as the detector for muon detection. Saint-Gobain BCF-92 wavelength shifting (WLS) optical fiber is used for the light transfer providing multi-channel position information. The optical fibers are coupled to two Hamamatsu H8500C MAPMTs. The PMT signals could then be measured with multi-channel QDCs. SiPM arrays are also being evaluated for readout. This prototype system is currently under construction. Preliminary tests results are shown in this paper. Full experimental results will be presented and discussed in the future.