January 3rd, 2010

#1875: This is almost right.

This Wired piece talks about the benefits of thorium-fueled nuclear reactors.

All of its pro-thorium statements are correct.

All of its anti-uranium statements are not.
Uranium is currently the actinide of choice for the industry, used (sometimes with a little plutonium) in 100 percent of the world’s commercial reactors. But it’s a problematic fuel. In most reactors, sustaining a chain reaction requires extremely rare uranium-235, which must be purified, or enriched, from far more common U-238. The reactors also leave behind plutonium-239, itself radioactive (and useful to technologically sophisticated organizations bent on making bombs). And conventional uranium-fueled reactors require lots of engineering, including neutron-absorbing control rods to damp the reaction and gargantuan pressurized vessels to move water through the reactor core. If something goes kerflooey, the surrounding countryside gets blanketed with radioactivity (think Chernobyl). Even if things go well, toxic waste is left over.
Let's take it from the top:

In most reactors, sustaining a chain reaction requires extremely rare uranium-235, which must be purified, or enriched, from far more common U-238. Typical reactor fuel is enriched to 3% U-235. We don't have a problem doing this. Reactor fuel can't be used to make a nuclear weapon.

The reactors also leave behind plutonium-239, itself radioactive (and useful to technologically sophisticated organizations bent on making bombs). It's true that uranium fuel leads to plutonium; but you don't have to separate the plutonium. You can leave it in.

And conventional uranium-fueled reactors require lots of engineering, including neutron-absorbing control rods to damp the reaction and gargantuan pressurized vessels to move water through the reactor core. A thorium reactor won't require "lots of engineering"? The "engineering" they're referring to are control systems and systems which extract the energy from the core. The water being moved through the reactor core serves two purposes: it acts as a neutron moderator, and it carries heat away from the core. The moderating effect slows down fast neutrons such that less nuclear material is required to sustain a chain reaction. The cooling effect does two things: it keeps the core from melting and the steam produced is what turns the turbines which make electricity. Which, y'know, is the whole reason to have a nuclear reactor in the first place.

Control rods let you regulate the speed at which a reaction takes place; it lets you "throttle" the reactor such that you can control its output. It's a feature, not a bug.

If something goes kerflooey, the surrounding countryside gets blanketed with radioactivity (think Chernobyl). Not in the United States it doesn't. The federal laws which regulate the nuclear industry specifically prohibit reactors like Chernobyl. (Thanks, Edward Teller!) But I've explained it over and over again until I'm blue in the face and sick of repeating myself.

Even if things go well, toxic waste is left over. ...as is the case with that tired old canard. If we just recycle our spent nuclear fuel, this won't be nearly as big a problem as everyone says it is, and the only thing keeping us from recycling our spent fuel is federal laws enacted by Carter and the Carter-era Congress. (Which, as I recall, were rescinded during the Bush years.)

*sigh*

The article goes on about how you can build a thorium reactor which can't melt down--well, duh, of course you can. We can build uranium reactors which can't melt down, too. There is nothing special about thorium.

Look, I'm all for building a fuck-ton of nuclear reactors and replacing coal and oil power. I think it's stupid to burn oil to make electricity when we can burn neutrons instead. But don't go making a new technology sound like it's the do-all be-all of fission when the stuff we have on the table right now works perfectly well as long as it's allowed to work. The problems with nuclear power are all political.

Period.