There are two rooms…

I love a good stark comparison. Like comparing a day’s worth of coal to the equivalent of uranium oxide. Or the whimsical but undeniable banana equivalent dose. Or how much electricity your smart phone truly uses. As well as more seriously, estimates of how many more people would have died had many countries chosen coal over nuclear. And don’t forget France.

And, of course…

But considering all the new coal generation coming online recently, I began doing some soft calculations, starting with the size of each of two average rooms which, assuming a 2.4 m ceiling, is 21.6 m3. With the average density of air at 1.225 kgm-3 one should expect 26.46 kg of air within each room. Given roughly a 400 ppm carbon dioxide concentration which is 591 ppm by mass, I estimated about 15.6 g of CO2 in the mix.

In the first room I put the byproducts of generating 1 kWh of electrical energy in the average coal plant, which will produce 1.001 kg of carbon dioxide. Taking the liberty of ignoring the change in air density despite the total mass in the room now equalling 27.46 kg, the concentration of this gas abruptly jumped to 36986 ppm or about 3.6%. For anyone with confined space training this sort of number probably makes you sit a little stiffly in your chair.

Fly ash when it’s not blowing around.

Didn’t I say byproducts? There would be an amount of fly ash and finer particulate waste which is dispersed into the atmosphere during normal operation. But wait: based on the ORNL yearly figures for an average 1 GW plant (8,760,000,000 kWh generated) which consumes 4,064,000 metric ton (thus 0.0004639 kWh per metric ton) this would include an average of 1.3 g of uranium and 3.2 g of thorium as oxides, dispersed randomly.

The second room was filled with the spent fuel from generating 1 kWh in an average LWR, and you can probably see where I’m going with this. 360,000 kWh from 1 kg of enriched UO2 fuel equated to 2.8 mg used in this example, which of course changed in mass very little due to the nature of the reactor and the process of fission itself. Regulation since the 1980s requires spent fuel to be sealed in dry cask storage for the long term, so I took the liberty of imagining a miniature steel-walled reinforced concrete cask sitting in the corner.

But the radioactivity reading was already small enough.

But the radioactivity reading was already small enough.

Choose your room. If you are still having trouble deciding, let’s call the waste and byproducts the equivalent of just one day‘s yearly average residential electricity use.

If my maths is off or my assumptions particularly ludicrous then please kindly let me know – I wasn’t initially expecting the comparison to be quite so stark!


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