General rightsThis document is made available in accordance with publisher policies. Please cite only the published version using the reference above. Full terms of use are available: http://www.bristol.ac.uk/pure/about/ebr-terms ABSTRACT: The non-invasive imaging of dense objects is of particular interest in the context of nuclear waste management, where it is important to know the contents of waste containers without opening them. Using Muon Scattering Tomography (MST), it is possible to obtain a detailed 3D image of the contents of a waste container on reasonable timescales, showing both the high and low density materials inside. We show the performance of such a method on a Monte Carlo simulation of a dummy waste drum object containing objects of different shapes and materials. The simulation has been tuned with our MST prototype detector performance. In particular, we show that both a tungsten penny of 2 cm radius and 1 cm thickness, and a uranium sheet of 0.5 cm thickness can be clearly identified. We also show the performance of a novel edge finding technique, by which the edges of embedded objects can be identified more precisely than by solely using the imaging method.

General rightsThis document is made available in accordance with publisher policies. Please cite only the published version using the reference above. Full terms of use are available: http://www.bristol.ac.uk/pure/about/ebr-terms Abstract: An analysis method of identifying materials using muon scattering tomography is presented, which uses previous knowledge of the position of high-Z objects inside a container and distinguishes them from similar materials. In particular, simulations were performed in order to distinguish a block of Uranium from blocks of Lead and Tungsten of the same size, inside a concrete-filled drum. The results show that, knowing the shape and position from previous analysis, it is possible to distinguish 5 × 5 × 5 cm 3 blocks of these materials with about 4h of muon exposure, down to 2 × 2 × 2 cm 3 blocks with 70h of data using multivariate analysis (MVA). MVA uses several variables, but it does not benefit the discrimination over a simpler method using only the scatter angles. This indicates that the majority of discrimination is provided by the angular information. Momentum information is shown to provide no benefits in material discrimination.

With time hydrogen gas is produced, which can accumulate in bubbles. These pockets of gas may result in bitumen overflowing out of the waste containers and could result in spread of radioactivity. Muon Scattering Tomography is a non-invasive scanning method developed to examine the unknown content of nuclear waste drums. Here we present a method which allows us to successfully detect bubbles larger than 2 litres and determine their size with a relative uncertainty resolution of 1.55 ± 0.77%. Furthermore, the method allows to make a distinction between a conglomeration of bubbles and a few smaller gas volumes in different locations.

A method was developed to determine the edge position of uranium blocks embedded in concrete, using Muon Scattering Tomography. This method is useful for nuclear waste management, as it provides a precise image of high-Z materials inside nuclear waste drums. Simulations were performed of uranium blocks with different sizes, encased in a concrete tube, and their lengths were reconstructed. The resolution obtained for the reconstructed lengths was 2.9 ± 0.5 mm and the method works down to a smallest size of 5 mm. This result was obtained without including the muon momentum. The same method was then applied including the momentum information, resulting in a better resolution of 0.96 ± 0.03 mm, and works down to a smallest size of 2 mm. K : Analysis and statistical methods; Search for radioactive and fissile materials 1Corresponding author.

A method was developed to determine the edge position of uranium blocks embedded in concrete, using Muon Scattering Tomography. This method is useful for nuclear waste management, as it provides a precise image of high-Z materials inside nuclear waste drums. Simulations were performed of uranium blocks with different sizes, encased in a concrete tube, and their lengths were reconstructed. The resolution obtained for the reconstructed lengths was 2.9 ± 0.5 mm and the method works down to a smallest size of 5 mm. This result was obtained without including the muon momentum. The same method was then applied including the momentum information, resulting in a better resolution of 0.96 ± 0.03 mm, and works down to a smallest size of 2 mm. K : Analysis and statistical methods; Search for radioactive and fissile materials 1Corresponding author.