Due to perpetual radiation exposure, radioactive waste stored in bituminized containers can generate various gases, which may pose significant safety and handling concerns for storage facilities. This paper introduces a novel 3D imaging method that uses muon scattering tomography to detect and map gas bubbles. Our study demonstrates that this technique can detect gas volumes as small as 0.55 L at a 95% confidence level after 27 days of muon exposure in a 200 L bituminized waste container. Our approach is versatile and can be applied to various waste management scenarios and other industries for gas and void control.

Inspection of ageing, reinforced concrete structures is a world-wide challenge. Existing non-destructive evaluation techniques in civil and structural engineering have limited penetration depth and don’t allow to precisely ascertain the configuration of reinforcement within large concrete objects. The big challenge for critical infrastructure (bridges, dams, dry docks, nuclear bioshields etc.) is understanding the internal condition of the concrete and steel, not just the location of the reinforcement. In most new constructions the location should be known and recorded in the as-built drawings, where these might not exist due to poor record keeping for older structures. Muon scattering tomography is a non-destructive and non-invasive technique which shows great promise for high-depth 3D concrete imaging. Previously, we have demonstrated that individual bars with a diameter of 33.7 ± 7.3 mm can be located using muon scattering tomography. Here we present an improved method that exploits the periodicity of bar structures. With this new method, reinforcement with bars down to 6 mm thickness can be detected and imaged.

Inspection of the world's ageing population of reinforced concrete infrastructure is a multi-billion dollar problem. Historically, it has not been uncommon for structures to deviate from their designs,or for design drawings to be lost. This leaves asset managers the challenging task of making structural health assessments and maintenance decisions with incomplete knowledge. While current techniques for detecting rebars in concrete are typically limited to penetration depths of less than 50 cm, muon scattering tomography (MST) is a non-destructive, non-invasive technique which shows great promise for high-depth 3D concrete imaging. This paper uses Monte Carlo simulations to demonstrate that MST can be used to detect and locate 100 cm length rebars with a diameter of 33.7 7.3 mm independently of the rebar's location within a concrete structure. This corresponds to a volume of inclusion of 894 386 cm(3). The volume of the inclusion can be reconstructed with a resolution of 5.4 0.3% for volumes above 2 500 cm(3). It is furthermore demonstrated that 30 mm diameter rebars can be distinguished as two separate objects provided their separation is more than 40-60 mm, and that single and double layers of rebars are distinguishable using the technique. It is anticipated that MST could inform practical studies which support more informed maintenance and modeling, eventually allowing digital twins to be created for a larger subset of historical steel and concrete structures.

Methods for the non-destructive assay of nuclear waste drums are of great importance to the nuclear waste management community, especially where loss in continuity of knowledge about the content of drums happened or chemical processes altering the contents of the drums may occur. Muon scattering tomography has been shown to be a promising technique for the non-destructive assay of nuclear waste drums in a safe way. By measuring tracks of muons entering and leaving the probed sample and extracting scattering angles from the tracks, it is possible to draw conclusions about the contents of the sample and its spatial arrangement. Within the CHANCE project, a newly built large-scale mobile detector system for scanning and imaging the contents of nuclear waste drums using atmospheric muons is currently undergoing commissioning.

There is a need for non-destructive assay of large concrete objects like bridges and buildings. Key issues are the thickness, density and reinforcement configuration as well as indications of cracks or delamination. Furthermore, changes in the condition of concrete structures like corrosion, degradation or cavitation and voids due to ageing can pose problems. Muon scattering tomography is a non-invasive method well suited to scan large concrete samples and detect low- and high-density inclusions such as iron bars or cracks/voids in concrete. The work presented here demonstrates that with muon scattering tomography it is possible to detect rebars of a volume of 894 ± 386 cm 3 in a thick concrete floor. For iron volumes above 2 500 cm 3 , the rebar volume can be reconstructed with a resolution of 5.4 ± 0.3% and the relative uncertainty is better than 10%. It is also shown that it is possible to image rebar structures in reinforced concrete and distinguish between single and a double layer of a rebar grid. The method was developed using Monte Carlo simulations, but it is foreseen to compare simulated data to real data collected with our muon detection system in the future.