[magicalhippo]

Just running the numbers here.

As per your Wikipedia article, current technology limits the borehole to 50 cm. That gets us 500 to 1000 m^3 worth of storage per borehole, assuming the lower 1km to 2km is used for storage.

From this[1] page, as far as I understand, on a global scale the current amount of nuclear waste in need of such storage is 482000 m^3. So roughly 500-1000 boreholes to store the current waste inventory.

Anyone got any ideas on how much it costs to drill a 5-6km 50cm hole?

[1]: http://www.world-nuclear.org/information-library/nuclear-fue...

[Krasnol]

It costs something around 1000€ for a 6m well. Without the paperwork.

But this is your usually drilling equipment for those depths.