I couldn't wait so dug up some numbers from various sources in advance. For coal:

• A 'typical' hard coal powerplant: 8.5 TWh electricity from 2.5 million tons, that's about 0.3 kg mined for 1 kWh.

• The most recent German brown coal (lignite) powerplant: 1.3 TWh electricity from 1 million tons, that's 0.77 kg mined for 1 kWh.

For nuclear: calculating with 0.85% U in U3O8, and a ratio of feedstock and enriched uranium of 8.5,

• With the 'current average' ore grade of 0.15%, a current modern plant extracting energy for 45,000 kWh electricity from 1 kg, we get 0.15 kg mined material for 1 kWh.

• With the 'current average' ore grade of 0.15%, and an EPR expectation of 60,000 kWh electricity from 1 kg, we get 0.11 kg mined material for 1 kWh.

• With current peak grade of 0.05% and the EPR, we get 0.33 kg mined for 1 kWh.

• With a cutoff grade of 0.02% and the EPR, we get 0.83 kg mined for 1 kWh.

• With a 0.0004% grade granite and the EPR, we get 41.7 kg mined for 1 kWh.

_{*Lunatic*, n.
One whose delusions are out of fashion.}

Regrettably I can't find my file, but I think I can reproduce parts of it as addition to the above. I remember looking at actual mining figures, so I did again.

For 2004, I find total global coal production was 5.524 billion tons, of which three-quarters, around 4.1 billion tons went for the production of 39.8% of a global electricity generation of just under 15,000 TWh, that is around 6,000 TWh. This gives an average of 0.68 kilograms of coal for 1 kWh. The figure is closer to the German brown coal power plant's figure I gave not because of the dominance of low-grade borwn coal (it is less than a fourth) but that of old inefficient plants. If we expect increasing efficiency for nuclear (EPR and all), we can also safely predict increased efficiency for coal, say to 0.55 kg giving 0 kWh.

For Uranium grades, current production (which is insufficient for current needs once material from decommissioned weapons runs out 5-7 years from now) seems to go rarely below 0.1%. (The current maximum is a staggering 18% at a Canadian mine, the minimum 0.035% at a Namibian mine.) But IAEA considers recoverable proven reserves those below $135/kgU, while most production is below $50/kgU. For a greatly broadened share of nuclear, these (and probably even more expensive) reserves have to be tapped. Unfortunately, in my current search I haven't found numbers on the grade of proven reserves close to $135/kgU, only found single examples that trend to above 0.01%.

At any rate, the figures for mined tonnage for coal and greatly increased non-breeder, non-thorium nuclear are in the same range.

_{*Lunatic*, n.
One whose delusions are out of fashion.}