Amidst the darkening clamor over global warming, declining fossil fuel reserves, conflicts over oil supplies, and rumors of heavy-handed governmental attempts to curb our carbon-hungry lifestyles, a welcome glow of hope is emerging on the energy technology horizon. To most viewers, it looks green, or at least "greenish." And--perhaps surprisingly to those of us who remember Three Mile Island and Chernobyl--it's radioactive.
As a climate scientist, I'm well-aware of the perils of global warming and I've long favored a timely switch to alternative energy sources. However, I've also drawn the line at nuclear power, having been an anti-nuke protester in college. I was therefore horrified when prominent environmentalists first began to suggest that nuclear power is preferable to fossil fuels, as though their apocalyptic climate rhetoric had trapped them into minimizing the risks of meltdowns, radioactive waste, bomb proliferation, and nuclear terrorism.
But my attitude changed recently when I raised this subject with an environmental scientist friend whose son is training to become nuclear engineer. "He's working on a new kind of reactor," my friend explained, "It can't melt down, it makes only minimal waste, and it can't be used for making bombs. It doesn't even use uranium, which is rare and dangerous to handle; it uses thorium instead, which is common and safer to work
A self-education tour of the Google-verse soon convinced me that his summary was accurate. Much of the most reliable-looking stuff online is written by engineers who aren't particularly lucid communicators, but I'll try here to sift out some of the key concepts for you, show where you can listen in on what experts are saying (try here ), and get you thinking and talking about this up-and-coming technology.
In other words, I want you to help save the world. If green nukes are even half as promising as their proponents claim, then supporting their development may be our best hope for a sane, sustainable, and abundant energy future.
So how does it work? Thorium is a heavy, silvery-looking metal similar to uranium but, although it's named after Thor, the Norse god of thunder, it's not as fiercely reactive. A thorium plant works much like a uranium-driven system, with nuclear chain reactions heating a liquid that drives turbines and generates electricity. But unlike uranium, it can't start or easily sustain the process on its own. To set a reluctant thorium reaction in motion, some designs use small amounts of uranium or plutonium as a sort of nuclear spark plug, while others use a quick shot from a particle accelerator.
One of the safest-sounding designs would dissolve thorium in molten fluorine salts and let the hot reactions bubble away in open-ended tubes. Should things get too intense in that sort of "liquid fluoride thorium reactor" (LFTR, pronounced "lifter"), the fluid would simply boil out of the tubes and kill the reaction automatically.
What about the waste? Thorium reactors produce relatively wimpy wastes that fade away much more quickly than uranium-derived stuff does, over several centuries rather than millennia. The waste is lousy for making bombs, unlike the plutonium formed in uranium reactors. And best of all, thorium reactions can burn and destroy other, more powerful radioactive materials. In other words, thorium nukes might not only provide gobs of cheap, non-polluting electricity--they might solve our already-vexing nuclear waste storage problems, too.
Thorium is abundant; India and Australia own the largest deposits, but the USA and Canada also have enough of it to last virtually forever. Once fully deployed on a large scale, the technology could be incredibly inexpensive. Thorium doesn't need as much costly refinement as uranium fuel does and, according to some estimates, the lack of meltdown risks alone could drop the price of thorium plant construction and operation by as much as 80%.
Some proponents envision "a nuke in every home," because self-contained thorium reactors can be built small enough to fit on a trailer truck bed. Such green nukes would dam no rivers and produce no acid rain or greenhouse gases, and their electrical output could create clean hydrogen fuels from water as well as seemingly limitless direct heating and lighting.
So why are we using uranium today instead of thorium? Apparently, it's because, well, thorium is too safe. Back in the Cold War setting of the 1970s, thorium technology was sidelined because it can't do what uranium reactors do so well: creating the plutonium needed for nuclear weapons arsenals.
Now, what's the catch? My gut tells me that anything that sounds too good to be true probably is. And I've spent enough time around religious and political extremists to sense blind evangelical fervor in some of the more vocal supporters of thorium. There's also an unhelpful dose of ego and machismo in some of the technical discussions online, as in "I'm right because my resume is longer than yours," that can drive potentially informative dissenters into silence (see it in the comment string following an article in Wired ).
This topic is too important to be left in the hands of a few tech-wizards who excel at building these machines but who may overlook other aspects of introducing it into the real world. Even without a degree in nuclear engineering, I think I've already found one rarely mentioned problem that will need attention before we push too hard for a green nuke in every home: low-tech terrorism.
Concerns about weapons proliferation from thorium reactors tend to be shouted down quickly in the engineering blogosphere, but one of the most-frequently cited worries is that some of the substances involved in thorium reactions, especially uranium-233, can be used to make bombs. A typical counter argument is that this kind of uranium is easily disabled by adding uranium-232 to it, a process that tends to happen naturally in reactors and that can also be applied manually as a safeguard. Another counter argument is that the U-232 contaminants in thorium reactors are so intensely radioactive that attempts at theft would be both suicidal and easily revealed by radiation detectors.
But danger is no deterrent to someone who is willing to die for a cause. In some future society that runs on thousands of small, decentralized thorium nukes, terrorists need only to break into a poorly guarded mini-reactor and dump its contents into water supplies, sprinkle it over a city from a plane, or dribble it along some busy roads from the back end of a car. Imagine the sheer panic that would result, not to mention the contamination of the target area. Remember, the primary aim of terrorism is not necessarily total annihilation, but terror itself.
And what about that relatively "short-lived" radioactivity in thorium-reactor waste that will still need to be stored safely for centuries; how many nations have remained reliably stable and conflict-free for hundreds of years?
Now don't get me wrong. These new nukes give me great hope, and I'm even starting to drink some of that evangelical green Kool-Aid myself, hence this post. But that's why I want to see us fully address the problems as well as the positive aspects of a thorium future, so we have a good shot at making it work as well and as soon as possible. If overly rosy sales pitches for this new technology mislead us or even just make people suspicious, they may slow its implementation. And time is of the essence; cheap fossil fuels are running out, further greenhouse gas buildups could trigger a runaway super-hothouse, and designing, testing, and mobilizing enough green nukes to service our energy demands will take decades.
There's no such thing as a perfect solution to our energy crisis and it's important to acknowledge that even LFTR-nukes have a bit of a dark side. Choosing the best path forward will require a thoughtful and open discussion of all aspects of that choice, not just the nuts and bolts but the practical human costs as well. By choosing to run the world on fossil fuels, our recent forebears also unwittingly caused much death and destruction due to mining accidents, pollution, and wars. We can surely do better than that as we face this new energy revolution within our own century, by planning our route more carefully in advance. Now's the time to learn as much as you can about green nukes, and to join the global conversation. It's your world, too, so let your voice be heard--we're going to need it.
Curt Stager is an ecologist, paleoclimatologist, and science journalist with a Ph.D. in biology and geology from Duke University. His new book is DEEP FUTURE: The Next 100,000 Years of Life on Earth  (St. Martin's Press, March 2011).