With an ID of around 10-in (260-mm), I get the sense they would need multiple boreholes to dispose of any significant quantity of waste.The waste would be sealed within two stainless steel canisters, and placed within a permanent steel casing that is grouted into place. The bottom of the hole would be plugged first, and the top would have some kind of backfill. I imagine the key to this technology is the geologic media the waste is being stored in. Obviously a site with a deep groundwater table would be significant. Any thoughts on what else one would be looking for in terms of the site and specifically the geology? Do you think the U.S. would ever implement such a system?
As the U.S. continues to fight over hurdles for its Yucca Mountain Nuclear Waste repository, Finland is on track to become the first country with a permanent storage facility for spent fuel rods from nuclear reactors. Their Onkalo tunnel, on the western coast of Finland will eventually stretch for 5-km (2-miles) and reach a depth of 500-m (1,600-ft) in solid granite bedrock. Once at depth a grid of horizontal tunnels will be constructed. Vertical storage holes will be excavated in these horizontal shafts, and the spent rods, encased in steel cannisters with copper corrosion protection, will be placed on layers of bentonite clay. The clay will cushion the cannisters and protect them against long term geologic movement. The clay also serves as a barrier to water, swelling in its presence to seal off any cracks or conduits for water that could potentially transport nuclear contamination in the distant future if the primary measures of protection are compromised. The tunnels will eventually be backfilled with bentonite and rock. The facility is projected to open in approximately 15 years at a cost of about 3 billion euros. The projected life of the facility is through 2100. Links after the break. (Illustration by BBC)