Reply #81: Lets go through the math:

[struggle4progress]

... specific radioactivity of natural uranium (25 kBq/g) ... http://www.world-nuclear.org/info/inf14.html
This is essentially the number I gave: 25,280 Bq/g

1 Bq is about 2.7027027027E-011 Ci (See: http://online.unitconverterpro.com/conversion-tables/convert-alpha/radiation---activity.html )
So 1 kBq = 2.7027E-08 Ci and 25.28 kBq = 6.8234E-07 Ci and 25,280 Bq/g = 0.000000683 Ci/g = 0.683 Ci/metric ton, since there are 1000000 g/metric ton. These are the numbers I gave

Current world coal consumption is about 7075 million short tons (See 2007 figures: http://www.eia.doe.gov/emeu/aer/txt/ptb1115.html )
This is essentially the figure I used. Reckoning a short ton as about 10/11 of a metric tonne would give something like 6500 million metric tonnes

.. In the majority of samples, concentrations of uranium fall in the range from slightly below 1 to 4 parts per million ... http://pubs.usgs.gov/fs/1997/fs163-97/FS-163-97.html
This is the link I cited before

The total natural uranium in 6500 million metric tonnes of coal is expected to be about 6500 - 26000 metric tonnes

According to Table 12.4 at p303 in Coal Geology (Larry Thomas) about 1.5% of the uranium in coal is released in flue gases and the rest in concentrated in the ash; see http://books.google.com/books?id=4oYWx90ybY8C&pg=PA303&lpg=PA303&dq=coal+%22fly+ash%22+fraction&source=web&ots=2pioUqF5j1&sig=-JEzm_SP_MHBprBoGsZ3SfOJg4M&hl=en&sa=X&oi=book_result&resnum=34&ct=result
We therefore expect an annual world atmospheric release of 0.015*6500 - 0.015*26000 metric tonnes of U from coal combustion. These numbers are 98 - 390 metric tonnes of U. In the link cited, I used the figure 392 metric tonnes U

Compute now the Ci released by 0.683 Ci/metric ton: 98 - 390 metric tonnes of U = 67 - 268 Ci
In the link you don't like, I gave the figure 267 Ci

So if you want to fuss about my calculation here, I think you shouldn't fuss about the arithmetic. You might sensibly fuss that I left out thorium or that I ignored daughter products in equilibrium. The specific activity of natural thorium is about 2.2E−7 Ci/g = 0.22Ci/metric tonne (see: http://www.fmcsa.dot.gov/rules-regulations/administration/fmcsr/fmcsrruletext.aspx?chunkKey=09016334800475ed ) which is a bit less than that of natural uranium. Uranium and thorium occur in comparable concentrations in coal, so including natural thorium wouldn't quite double the estimate. What about correcting for daughters in the actinide chains? If one assumes equilibrium, the total decays from the daughters at each stage of the chain must equal the total decay of their parents, so the total activity can't exceed the above estimates multiplied by the length of the longest chain. Looking up the actinide decay chains suggests a factor of maybe 8. So if you want to be grumpy, we'll say 10 and estimate that world coal combustion releases 2670 Ci radioactivity from natural U and Th and their daughters -- as un-captured flyash particulates approximately as radioactive as shale

It's not uncommon for a nuclear power site to release about that much radioactivity to the environment in a year: in 2004, for example, Beaver Valley reported releasing 2449 Ci tritium, Byron Station reported releasing 2520 Ci tritium, and Diablo Canyon reported releasing 2951 Ci tritium

So NNadir's link is actually bullshit