One year ago, a massive earthquake spawned a tsunami that nearly destroyed Japan’s Fukushima Daiichi nuclear plant, further frightening people who had been wary of nuclear power since accidents at Three Mile Island in 1979 and Chernobyl in 1986.
But a small group of scientists, entrepreneurs and advocates see the post-Fukushima era as the perfect opportunity to get the United States to consider a proposal they have made with no success for years. What about trying a new fuel, they say, and maybe a new kind of reactor?
The proposed fuel is thorium, an abundant silver-gray element named for the Norse god of thunder. It is less radioactive than the uranium that has always powered U.S. plants, and advocates say that not only does it produce less waste, it also is more difficult to turn into nuclear weapons.
They’re pushing the idea of adapting plants to use thorium as a fuel or replacing them with a completely new kind of reactor called a liquid-fluoride thorium reactor, or LFTR (pronounced “lifter”). The LFTR would use a mixture of molten chemical salts to cool the reactor and to transfer energy from the fission reaction to a turbine.
Proponents say such a system would be more efficient and safer than existing plants, which use pressurized water to cool uranium fuel rods and boiling water or steam to transfer the energy they create.
“A molten-salt reactor is not a pressurized reactor,” said John Kutsch, director of the Thorium Energy Alliance, a trade group based in Harvard, Ill. “It doesn’t use water for cooling, so you don’t have the possibility of a hydrogen explosion, as you did in Fukushima.”
Kutsch and others say that a thorium-fueled reactor burns hotter than uranium reactors, consuming more of the fuel. “Ninety-nine percent of the thorium is burned up,” he said. “Instead of 10,000 pounds of waste, you would have 300 pounds of waste.”
‘Small boatloads of fanatics’
Although the idea of thorium power has been around for decades — and some countries are planning to build thorium-powered plants — it has not caught on with the companies that design and build nuclear plants in the United States or with the national research labs charged with investigating future energy sources.
“There are small boatloads of fanatics on thorium that don’t see the downsides,” said Dan Ingersoll, senior project manager for nuclear technology at the Oak Ridge National Laboratory in Tennessee. For one thing, he said, it would be too expensive to replace or convert the nuclear power plants already running in this country: “A thorium-based fuel cycle has some advantages, but it’s not compelling for infrastructure and investments.”
He also pointed out that thorium would still have some radioactive byproducts — just not as much as uranium and not as long-lived — and that there is no ready stockpile of thorium in the United States. It would have to be mined.
Overall, he says the benefits don’t outweigh the huge costs of switching technologies. “I’m looking for something compelling enough to trash billions of dollars of infrastructure that we have already and I don’t see that.”
Credit: Kevin Cole
A summary of how this technology works:
ReplyDelete1) You start with a fluoride salt. In this reactor it will be heated so much that it melts.
2) You dissolve thorium fluoride in the liquid salt.
3) Thorium-232 absorbs neutrons and turns info Uranium-233.
4) The Uranium-233 fissions and produces heat plus more neutrons.
The fission products are relatively benign and short-lived compared to those of a traditional reactor.
Advantages include:
1) There is no pressure – unlike traditional nuclear reactors which contain high pressure steam. So the reactor cannot explode.
2) The fuel does not need to be shaped into pellets
3) The reactor can add fuel and remove waste at any time
4) There are no weapon-grade materials involved
5) Thorium is abundant and most of it is used up in the reaction
Is this not better than the current method of Nuclear power?