2008-06-04

Essay: Pick Your Poison

Pardon for the diversion from my usual subject matter.

Someone I know by the name of John Ogilvie asked me to put into a letter what I've come to learn about nuclear power so he could have something to share with other Green Party members. Apparently the Green Party is flatly against nuclear power generation inspite of its benefits (not that it's without drawbacks).

I kept my policy of "back it up with facts". Here's what I shared with him.




Pick Your Poison


Facts to be used when discussing nuclear power


Our society is in the midst of a search for sources of power that are both safe and bountiful but none exist that can displace our current technologies - so we are left with a choice between the available evils. Is nuclear power one of these evils? Strong emotions are evoked when the words "nuclear power" (pronounced 'noo-clee-ar pow-er') are spoken. Prime among them is fear. Most people's nuclear knowledge extends only as far as WW2 mushroom clouds, Chernobyl, and waste disposal problems. It is only possible to have an educated discussion on the potential for nuclear power to fill our energy needs when the facts are examined as objectively and quantitatively as possible. After all, nuclear power is not as common as the combustion energy sources we're used to.

Let's consider the implications of shutting down all of the coal-, oil- and natural gas-fired generating stations in Ontario. This would remove 3.3 Gigawatts (17.7%) from Ontario's electrical generation capacity. How would this be replaced, assuming no change to consumption? There are no viable large hydroelectric sites, photovoltaic (PV) solar panels consume immense power for production, and wind turbines are almost as costly as PV cells. And as we know in government - management of hundreds of small projects would be cumbersome compared to management of several large projects, so it's "go big or go home" when we're taking about the electrical grid.

Let's look at the fuel used for nuclear power: uranium. Several forms of uranium exist. Uranium-238, unsuitable for use as fuel, accounts for over 99% of all natural uranium and has a half-life of 4,470 million years (higher the half-life, the less radioactive the material). Uranium-235, suitable for fuel and weapons, accounts for less than 1% and has a half-life of 704 million years. In other words, natural uranium is weakly radioactive. By comparison carbon-14 - a natural source of radioactivity found in all living things - has a half-life of 5,730 years (0.005 million years). C-14 is radiologically toxic in comparison to U-238 and U-235. The dreaded plutonium-239 has a half-life of 24,100 years and is chemically unstable in an oxygen atmosphere.

Let's also examine the nuclear reactor used in Canada - the legendary CANDU. I will not use the term "legendary" without qualification. The CANadian Deuterium Uranium rectors were conceived, designed, developed, and constructed in Canada by the predecessor of Atomic Energy Canada Limited (AECL) in the 1950s. But since Canada was (is?) a peaceful nation, the lack of Canadian uranium enrichment facilities led to a reactor design that used unenriched Uranium. Enrichment is the process which increases the concentration of U-235 from <1% to about 9% to reach criticality easier. In a nutshell, the geometry of the reactor core allows CANDU reactors to run on unenriched fuel, and is the reason that it takes days to start-up a CANDU. Remember how after the blackout of 2003 it took days to get electricity back in the province? A safety side-effect of the CANDU design is if the reactor starts to overheat, the core will soften and deform, breaking the geometry of the reactor core and thereby breaking criticality - the nuclear chain reaction will slow down and not run-away to a meltdown. Put simply, Three Mile Island and Chernobyl wouldn't have happened if they used CANDU reactors.

How much do we rely on nuclear power? There are 3 nuclear generating stations in Ontario: Darlington, Pickering and the privately operated Bruce. These 3 sites produce over 50% of the peak electrical demand for the most populated province in the country. That is without doubt an awesome amount of power generation for such a small number of stations of relatively small size.

Ok then, so how much material is used in generating electricity using CANDU reactors? One litre of diesel fuel - like that used in oil fired generating stations - has an energy density of 45.47 Megajoules per kilogram (or about 0.0126 Megawatt-hours per kilogram). According to the IAEA and the World Nuclear Fuel Market, more than 55.5 Megawatt-hours of electricity is generated in a CANDU for every kilogram of uranium. The energy density of nuclear fuel is therefore 4,400 times higher than oil and one kilogram of uranium would be enough to power a home for over 4.5 years. The main downside of nuclear power is the waste is just about the nastiest stuff imaginable. But the waste from a CANDU reactor can be refined and reacted a second and even a third time in a CANDU reactor. Once it's totally spent, the waste is stowed away and unusable as weapons matirial. By contrast, the waste products of combustion generation (i.e., coal, oil or natural gas) are emissions into the atmosphere and you know the CO2 story there. The key is safe long-term storage of nuclear waste.

Now what about the safety of combustion energy? Let's look at the tar sands as an example of safety. Here is a link to a satellite view of a settling pond where processing waste is left to separate. Notice how only 400 meters separates the pond from the Athabasca River (a 1,200 km river, 9th longest in Canada). If we talk about nuclear waste accidents and meltdowns, let's talk about the cost of a spill from one of these ponds into the Athabasca River. The cost would be incalculable. The Exxon Valdez spilled 41.6 million liters of oil across 760 kilometers of shoreline. A break in the levee of a single major settling pond in Fort McMurray would be on the same scale to downstream wildlife and human uses.

Uranium mining is nothing like working on a reactor in a power plant. Because of the relatively low concentrations of uranium in ore, most mines are open-pit and resemble a quarry. The workers don't wear protective equipment against the radiation because of the low radioactivity (high half-life). In fact, it's adequate that they're inside the cabin of a dump truck. The principal risk from uranium mining isn't the uranium itself (since it has such a low half-life); it is from one by-product of uranium decay - the noble gas radon. Though it is found in extremely low concentrations, radon is airborne and highly radioactive, with a half life measured in hours. Uranium is not airborne (being 70% denser than lead) and not a risk to any surrounding population - at least no more dangerous than mining for any other mineral.

So there you have it - a few details. Now that it's served on a silver platter you can call shenanigans on someone who spews nonsense. Our societal necessity - or at least dependence - on reliable electricity requires that we discuss the facts of generation and not the hyperbole and hearsay. We owe it to ourselves and the future of our society to make the most informed choices to prevent environmental consequences. Nuclear power isn't chocolate boxes and roses, but neither is any other source of energy. But with the proper facts in hand, we can discuss the options rationally. I hope this letter has served that purpose with respect to nuclear power.

References

  1. Uranium:
  2. Uranium mining:
  3. Carbon-14:
  4. Plutonium:
  5. The CANDU Nuclear Reactor:
  6. World uranium consumption and electrical generation:
  7. Electrical generation in Ontario:
  8. The 2003 Ontario and North Eastern US blackout:
  9. Diesel oil energy:
  10. Map of the Exxon Valdez disaster:
  11. Darlington Nuclear Generating Station:
  12. Single settling pond in Fort McMurray tar sands
  13. Rabbit Lake Saskachewan Uranium Mine

2 comments:

Jennifer J said...

Phenomenal essay. I learned a lot. Great references, too.

Now, in a different bent, can you tell me why we don't all recycle gray water into our toilets?

... Smells Like Fries said...

"Indeed" says the lady of the house!

Occam's Razor tells me: "because it's easier to plum a house without it".

Retro-fitting that kind of thing would be very tricky. We looked at waste water heat recovery - but most of our water use goes down a waste pipe that's hidden behind our basement bathroom wall. No way I'm going to tear that down untill I have to! I sense and idea for another post ... humm.