The UK has a nuclear legacy that includes nuclear power stations, nuclear fuel fabrication plants, waste processing plants, and also radioactive materials in industry, medicine, research & development including military nuclear programmes. The wastes are produced during the operating lifetime of such facilities, where characterisation is a key challenge facing by the nuclear industry. Many such facilities were built in early 1940 where, it is difficult to understand the nature of the problems need solving, for example due to poor record keeping etc. The removal of radioactive materials from these sites requires radiation detection and localisation. This project involves a comprehensive investigation of integrating recently developed mixed-field radiation imaging system with a Ground-Penetrating Radar (GPR) to characterise decommissioning nuclear sites and facilities. The project is supported by funding from the Nuclear Decommissioning Authority and EPSRC.