Microbes for managing waste

摘要

Over the last 60 years, the UK has accumulated over 4.77 million cubic metres of radioactive waste and spent nuclear fuel. More than 90% is low or very low-level waste, 9% is intermediate level waste, and only 0.03% is high level waste and spent fuel. Discharged spent fuel is stored under water, which provides an effective radiation shield and conducts away excess heat. But it can't stay there forever: higher activity waste contains long-lived radionuclides of technetium, neptunium and plutonium formed in the reactor, and uranium-238 (Ⅵ) from fuel, all of which remain radiotoxic for tens to hundreds of thousands of years - and, in the case of U 238, billions. Ultimately, the spent fuel and intermediate level wastes from handling it are destined for deep geological disposal. The plan is to grout intermediate level waste into steel canisters and bury it hundreds of metres underground in impermeable rocks such as argillaceous or plutonic rocks, before being backfilled with cementitious materials. This deep geological disposal facility (GDF) will be designed to keep waste encapsulated for thousands of years before the engineered barrier degrades, the waste gradually penetrates and integrates back into the environment.