Yesterday’s *Toronto Star* carried a curiously soft-hitting front page headline about nuclear “waste.” While trumpeting the fact that Canada has produced over 2 million bundles of it—which sounds like a lot—the *Star* gives no point of comparison with the waste products of other types of power plants. If comparators had been presented in the article, readers might get a better idea of how things really stack up.

Those 2 million used nuclear fuel bundles, each weighing about 20 kilograms, collectively weigh 40 million kilograms, or 40,000 metric tons. That’s from over four decades of operation.

If you think 40,000 tonnes over four decades is a lot, here is a point of comparison the *Star* could have provided. Gas-fired power plants in Ontario have dumped more than 5,300 tons of carbon dioxide (CO_{2}) between midnight September 1 and and 0830 September 2. They will likely have surpassed nuclear spent fuel by midnight tonight, i.e. within a single day. (They did surpass the weight of nuclear fuel, with extreme prejudice; see the Afterword below.)

Every year gas-fired plants dump literally millions of tons of CO_{2} into the air. Operators of gas-fired power plants could not possibly keep the stuff on site; at a production rate of thousands of tons of it per day, there is just too much of it. So those millions of tons of CO_{2} are simply dumped into our air. The now-unrecoverable CO_{2} will swirl around in the atmosphere for hundreds of thousands of years before dissolving in ocean water, making it more acidic.

The *Star *article asks us to picture we have “lived in the same house for more than half a century, and never taken out the garbage.” That is essentially the case with spent fuel in Canadian nuclear plants. Just about every used fuel bundle is indeed stored at the same plant that burned it to make electricity.

But that is where the *Star* analogy stops working. Most of us produce kilograms of garbage every day. For our garbage situation to be analogous to Canada’s nuclear used fuel, then we would be producing about a gram of it per day, or around one-third of one kilogram per year. Over four decades, we would each have accumulated about 14.6 kilograms of garbage.

Would this constitute a real problem, let alone a crisis? If it were solid garbage, say metal or plastic or paper, maybe. Fifteen kg of paper would be bulky, and we would want to get rid of it to open up space. But if we had some way of compacting it into a block the size of, say, a cinder block, then it would be essentially inconsequential. We could go for another forty years, and have two solid blocks of garbage, each the size of a cinder block.

That is essentially the situation with Canada’s nuclear “waste.” Bear in mind that this stuff contains significant amounts of hugely useful isotopes of plutonium, uranium, cesium, and strontium. The first two could be used (and reused) as fuel, and the latter two have numerous uses, including in health care.

[**Afterword: Ontario gas-fired power plants ended up dumping over 61,000 metric tons of CO _{2} into our air on September 2 2012. That is to say: in a single day, gas-fired plants in a single province—Ontario—produced 50 percent more garbage than the combined nuclear fleets of three provinces—Ontario, Quebec, and New Brunswick—have produced in over forty years of operation. And when I say the Ontario gas plants “dumped” 61,000 tonnes of CO_{2}, I mean exactly that. Those 61,000 tonnes are now in our air, and it will be impossible to get them back.**]

Let’s put the numbers into perspective. 40000 metric tonnes over 40 years. Assuming a density of about 2.5 (my guess but a reasonable estimate. Similar to a sandstone) the total volume would be 40000/2.5 = 16000 cubic metres. Still sounds like a lot. Now take the cubic root of 16000 and you get a bit over 25m. Since the fuel bundles aren’t made to fit into one cube, you would have to make the cube bigger than 25m a side. Make it 30m a side. Doesn’t seem like so much now, does it? 40 years worth of spent nuclear fuel fits into a cube 30m a side.

Now consider reprocessing. Reprocessing reduces the volume to 20% of the original. 20% of 16000 cubic metres is 3200 cubic metres. Take the cubic root and you get a bit less than 15m. So with reprocessing, 40 years of nuclear waste fits into a cube 15m a side. Such a small volume can easily be dealt with.

The numbers in the Toronto Star article aren’t adding up. 2273873 fuel bundles plus another 85000 or so equals 2358873 bundles. Each are supposed to be the size of a fireplace log. I imagine a fireplace log to roughly be a cylinder of about 40cm long (0.40m) with a radius of 15cm (0.15m). Volume of a cylinder= Pi X radius squared X length = 3.14 X (.15 squared) X 0.4 = 0.02826 cubic metres. Take that number and multiply by 2358873 and you get 66662 cubic metres. This would be the volume of a cube about 40.5m.

The article says that this would fill 6 NHL hockey arenas up to the boards. An NHL hockey arena is 61m X 26m. It is not a square but close enough. The boards are 1m high. 61 m X 26 m X 1m X 6 arenas = 9516 cubic metres. This would be the volume of a cube about 21.2 m a side.

Something isn’t right here. All these fuel bundles together weigh 40000 tonnes. So using the volume estimate of 66662 cubic metres, that means that the bulk density would be 40000/66662 = 0.6. That means the density of this stuff would be less than water with a density of 1. The stuff would float.

Using the other volume estimate (6 NHL arenas) you get 40000/ 9516 gives a density of 4.2. That is a very high density. Rocks seldom have a density of more than about 3.

What gives?

“Rocks seldom have a density of more than about 3” but fuel pellets are not your average rock. Uranium is a denser element than lead, and its compounds are also dense. Fuel pellets consist of UO2 ceramic, which has a relative density of 10.97. The fuel bundles, of course, are not solid UO2, so a bulk density of about 6 would be the right ballpark. It certainly sounds as if the hockey arena number is a factor of about 10 too big.

Thanks for the info. I have been trying to find out about the density of spent nuclear fuel for awhile and couldn’t find any. Do you have a reference to share with me? Where did you get the 10.97 number for ceramic UO2? Is the 6 number for bulk density of the whole bundle your own estimate?

Well, I just looked up “Nuclear fuel cycle” and “Uranium dioxide” in Wikipedia and guesstimated from there.

But now I’ve found something more relevant: http://en.wikipedia.org/wiki/Nuclear_fuel#CANDU_fuel . We see that each bundle is about 50cm long, 10cm in diameter, and weighs ~20kg. That works out to a density of 20,000/(5cm*5cm*3.14*50cm) = 5.1 g/cm3 for the overall bundle. The zirconium cladding (density=6.1) plus the coolant ducts (density 0) reduces the overall density from that of solid UO2.

Of course, the packing density of the bundles isn’t 100% because of their round shape, but about about 90% for a tidy pile of them. So that brings us down to a density of about 4.6 for the overall pile. So your calculation of 4.2 above looks pretty close.

PS: Spent fuel is of course still 98%+ uranium-oxide so the physical density doesn’t alter significantly.

PPS: The fuel bundles in the Candu EC6 reactor are described as weighing 24kg in this reference: http://www.candu.com/site/media/Parent/EC6%20Technical%20Summary_2012-04.pdf .

OK, so if the bulk density of the spent nuclear fuel, pellets, cladding tubes, space in between the tubes is about 6, then 40000/6=6667 cubic meters. Assuming a rectangular hockey rink (I know, the corners are rounded but close enough) has a volume of 61 X 26 X 1 = 1586 cubic meters. 6667/1586 = 4.2. So all of Canada’s spent fuel bundles collected over the past 40 years would easily fit into 5 hockey rinks with lots of space left over, right? Or to put it another way, all of it would fit into a cube 20m a side since the cubic root of 6667 is 18.8m. This really isn’t a very big problem.

Whoops, should have refreshed the page before I posted. Didn’t see your latest comments. So overall bulk density is 4.6. 40000/4.6 = 8696 cubic meters. A hockey rink is 1586 cubic meters. 8696/1586 is 5.5, so the article is about right when it says that it would all fit into 6 hockey rinks up to the boards.

Thanks for the references, by the way.

Whoops, should have refreshed the page before I posted. Didn’t see your latest comments. So overall bulk density is 4.6. 40000/4.6 = 8696 cubic meters. A hockey rink is 1586 cubic meters. 8696/1586 is 5.5, so the article is about right when it says that it would all fit into 6 hockey rinks up to the boards.

Thanks for the references by the way.

I also saw the article. Typical journalism wanting to scare people. Amounts to a tempest in a teapot.

More nonsensical FUD (fear, uncertainty, doubt) on the part of the anti-nukes.

http://www.lucknowsentinel.com/2012/08/27/time-to-open-up-about-pros-and-cons-of-dgr

What such alarmists fail to grasp is that more nukes means less waste. What makes nuc waste a waste is a small volume of it, making development of reprocessing technology an unprofitable enterprise. More nukes means rise of the cost of uranium, bringing about development of waste reprocessing and Gen IV inherently safe breeders. If you want to have almost almost absolutely safe nuc power, you must either develop it or close all existing plants. Reducing their number and stopping further development is the worst possible solution.