Thorium- A Safer Nuclear Alternative?

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.

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.

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.

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.