High-temperature, very deep, geological disposal: a safer alternative for high-level radioactive waste?

Safe disposal of radioactive waste, especially spent fuel, ex-military fissile materials and other forms of high-level waste (HLW), is one of the major challenges facing contemporary science. Currently, the internationally preferred solution is for geological disposal by interment in a mined and engineered, multi-barrier repository. Although this is often referred to as “deep” disposal, the depths involved are usually quite shallow in geological terms. A new scheme, currently under development, for the high-temperature disposal of concentrated HLW in very deep boreholes is outlined. Recent advances in the knowledge of continental crustal rocks and fluids at depths of several kilometres suggest that much deeper disposal might offer a safer and environmentally more acceptable solution to the HLW problem. The new scheme seeks to capitalise on this potential while turning the problematical heat output of the waste to advantage. It appears to offer significant benefits over both mined repositories and earlier borehole scenarios, particularly in terms of safety.