MANAGEMENT OF SNF/HLW: INSIGHTS FROM RISK MANAGEMENT OF SULFIDE-BEARING MINE WASTES

Evaluating the long-term management of spent nuclear fuel (SNF) and high-level nuclear waste (HLW) is routinely described as a complex, one-of-a-kind technical project conducted in a complex, if not recalcitrant policy environment. The project is widely considered to uniquely require significant advances in many disciplines of the geosciences (e.g., site characterization, hydrology, geochemistry) and engineering. The current inventory of commercial SNF in the U.S. is about 75,000 metric tonnes of heavy metal (tHM), accumulating at about 2,000 tHM/a, and would occupy about 0.5 ha of surface to a depth of about 8 m.

Sulfide mine wastes at closure of a single mine typically amount to millions to billions of metric tonnes by mass, occupy hundreds to thousands of hectares of surface, with some structures extending over several hundred meters of vertical relief, and for a large mine accumulate at rates up to 150,000 tonne/day. Regardless of the specific climate of the mine site, reaction rates for sulfide oxidation show that the wastes will remain geochemically reactive for geologic time, releasing trace elements to surface and ground waters that are known to be toxic to humans and ecological receptors. Additional issues, some related to geochemical ones, arise for hydrogeological, geomechanical, geomorphic, and seismic stability, and the opening, operation and closure of sulfide mines is routinely highly contentious in terms of social issues, often at national and even international levels.

It seems reasonable that societal approaches to risk management for conventional waste management should have some proportional relationship to the approaches society uses for management of SNF/HLW. We consider two aspects of the mine-waste approach: (a) the routine use of a safety-case approach, and (b) considerations of the period of time over which performance is to be considered effective.