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

Safe disposal of radioactive waste, especially spent fuel, ex-military fiss ile materials and other forms of high-level waste (HLW), is one of the majo r challenges facing contemporary science. Currently, the internationally pr eferred solution is for geological disposal by interment in a mined and eng ineered, multi-barrier repository. Although this is often referred to as "d eep" 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 adv ances in the knowledge of continental crustal rocks and fluids at depths of several kilometres suggest that much deeper disposal might offer a safer a nd environmentally more acceptable solution to the HLW problem. The new sch eme seeks to capitalise on this potential while turning the problematical h eat output of the waste to advantage. It appears to offer significant benef its over both mined repositories and earlier borehole scenarios, particular ly in terms of safety. (C) 1999 Elsevier Science Ltd. All rights reserved.