A key challenge in disposing of nuclear legacy facilities and planning a new nuclear plant is how to assess the extent or likelihood of radioactive contamination in construction materials and the ground. This paper summarises the status of two techniques based on the analysis of emitted radiation from materials that comprise such structures, and describes how this analysis can be used to infer the depth of contamination without the need to penetrate the structure or to destroy it in the process. Two experimental facilities have been developed to test the efficacy of these techniques, and data are provided for the most widespread contaminant experienced in the sector: caesium-137. Finally, the influence on the technique of the likely variety of silica-based media to be encountered in the nuclear industry is described, together with a summary of challenges to be addressed in future research.