Evaluation of a novel bismuth-loaded plastic array for X-ray and neutron radiography

Abstract

Some novel organic plastic scintillators offer substantial improvements in light-yield, detection efficiency, and pulse-shape discrimination over more traditional plastic materials. One promising application for select organic scintillators is in lowcost, portable, and durable dual-particle imaging (DPI) systems to support nuclear safety, security, and safeguards purposes. All candidate materials should first undergo investigation utilizing industry standards to quantify and evaluate their capabilities. In this work, a 21% bismuth-loaded polyvinyl toluene (BiPVT) fabricated by Lawrence Livermore National Laboratory (LLNL) was computationally and experimentally evaluated as a small, pixelated radiographic array, with individual pixel dimensions of 2×2×19 mm. For comparison, the same evaluations were conducted for two samesized arrays made from EJ-200 and EJ-256. ASTM standard test methods and practices were utilized to calculate the modulation transfer function and basic spatial resolution for each array, both from measured and simulated data. Measurements were recorded by pressure coupling all three arrays to a commercial a-Si digital radiographic panel, and the computational model replicated the experimental design. Computational and experimental results were compared for all three arrays in the x-ray environment, whereas only computational results are available at this time for comparison in a fast neutron environment. The x-ray results demonstrate that BiPVT outperformed nearly identical arrays made from EJ- 200 and EJ-256, and the agreement between the simulated and experimental x-ray results validates the applied computational methodology for comparative predictions of neutron performance. Based on these simulations, the BiPVT array is also expected to outperform arrays made from EJ-200 and EJ-256 in fast neutron environments. These findings suggest that DPI systems utilizing BiPVT hold promise over more traditional material alternatives for continued development.