Assessing the feasibility of interrogating nuclear waste storage silos using cosmic-ray muons

Muon radiography is a fast growing field in applied scientific research. In recent years, many detector technologies and imaging techniques using the Coulomb scattering and absorption properties of cosmic-ray muons have been developed for the non-destructive assay of various structures across a wide range of applications. This work presents the first results that assess the feasibility of using muon radiography to interrogate waste silos within the U.K. Nuclear Industry. Two such approaches, using different techniques that exploit each of these properties, have previously been published, and show promising results from both simulation and experimental data for the detection of shielded high-Z materials and density variations from volcanic assay. Both detection systems used are based on scintillator and photomultiplier technologies. Results from dedicated simulation studies using both these proven technologies and image reconstruction techniques are presented for an intermediate-sized legacy nuclear waste storage facility filled with concrete and an array of uranium samples. Both results highlight the potential to identify uranium objects of varying thicknesses greater than 5 cm within real-time durations of several weeks. Increased contributions from Coulomb scattering within the concrete matrix of the structure hinder the ability of both approaches to resolve similar objects of 2 cm dimensions even with increased statistics. These results are all dependent on both the position of the objects within the facility and the locations of the detectors. Results for differing thicknesses of concrete, which reflect the non-standard composition of these complex, legacy structures under interrogation, are also presented alongside studies performed for a series of data collection durations. It is anticipated that with further research and optimisation of detector technologies and geometries, muon radiography in one, or both of these forms, will play a key role in future industrial applications within the U.K. Nuclear Industry.