The waste footprint of electricity generated with the “cleanest” fossil fuel is tens of thousands of times bigger than that of nuclear energy.

Crunching the numbers from a recent NWMO report on CANDU fuel burnup and its implications for the design of a deep geological repository for spent fuel, I thought it might be fun to calculate the spent fuel intensity per kilowatt-hour of nuclear energy and see how it compares with the waste product of fossil fuels. As you can see from tables A1 and A2 on the left sidebar of this blog, the waste product of gas-fired power generation is quite substantial: between midnight and eleven a.m. on Monday July 13 gas-fired plants had dumped nearly 12,000 tons of carbon dioxide (CO 2 ) into our atmosphere. The gas plants had collectively contributed just over 11 percent of Ontario’s electrical energy over that period. Tables A1 and A2 are dynamic, so the values you see now will be different from those when I wrote this piece. No matter: the main thing is to note how much CO 2 is coming out of the gas plants. Also note that that amount is metric tons; one metric ton is one million grams.

And as you can also see, the nuclear fleet, which produced more than 65 percent of the electricity, produced zero CO 2 . But what about spent fuel? This is commonly referred to as “waste.” How much waste did the nuclear plants create, en route to generating the 135 million kilowatt-hours they contributed to Ontario’s grid from midnight to eleven a.m.?

I have mentioned elsewhere that a Darlington-size reactor will discharge around 16 used fuel bundles per day. The NWMO report corroborates this: in Table 1 on page 3 you can see that the Darlington units discharged 102,229 (unit 4) to 110,309 (unit 2) used fuel bundles from their start dates until late August 2012. This covers periods of 7,784 days (unit 1), 7,972 days (unit 2), 7,082 (unit 3), and 6,909 days (unit 4). Divide the bundles discharged by days and you get roughly 14 bundles per day for units 1 and 2, and 15 per day for units 3 and 4.

A Darlington-size CANDU fuel bundle weighs roughly 23 kilograms, or 23,000 grams.

If a reactor discharges 15 bundles per day, that is 345,000 grams (0.345 metric tons) of nuclear waste per day. That same reactor (let’s continue with Darlington-size machines, which were rated at 860 megawatts net but were subsequently uprated to around 930 MW) will generate roughly 18.5 million kilowatt-hours per day. So divide 345,000 grams of spent fuel by 18.5 million kilowatt-hours, and you get roughly 0.0185 grams of spent fuel per kilowatt-hour.

Now, look again at tables A1 and A2 on the upper left. For the gas-plants to produce the 1,966 and 11,723 metric tons of CO 2 from midnight to eleven a.m., while generating less than 12 percent of Ontario’s electricity, their CIPK must be over 500 grams. How much greater is that than the nuclear waste intensity per kilowatt-hour?

The nuclear WIPK is 0.0185 grams; the CIPK of the most efficient gas-fired generator is close to 400 grams.

Which means the gas-fired CIPK is more than 21,000 times greater than the nuclear WIPK.