The nature of material found within active ‘legacy waste' storage vessels and other radiation shielded vessels coupled with the distinct lack of access makes representative sampling or visual inspection of the vessel extremely problematic and in some cases impossible. In recent years the use of non-intrusive and non-invasive imaging techniques to safely interrogate non-nuclear (industrial) storage vessel or process units has seen a significant increase. However, until recently the radiation shielding which is commonplace on all nuclear sites has rendered existing remote non-intrusive imaging techniques useless. This is due to the limiting penetrative power of X-rays and gamma-rays as well as lack of access for other semi-invasive techniques such as electrical and acoustic imaging. Here, the use of naturally occurring ubiquitous galactic and solar cosmic rays for imaging the inventories of shielded vessels are considered. More specifically, high energy secondary cosmic ray muons have been modelled, detected and attenuated (absorbed) which has provided a suitable platform for the design of a prototype muon imaging system. Such a system will enable the internal imaging of otherwise opaque shielded storage vessels by harnessing the muons superior penetrative power, thus providing valuable inventory measurements which will enable a safer and more economic legacy waste recovery strategy.