What’s green about thorium? First, thorium reactors are more efficient than uranium reactors, because they waste less fuel and produce far more energy. Most nuclear power plants are currently only able to extract between 3 and 5 percent of the energy in uranium fuel rods. In molten salt-cooled reactors, favored by many thorium proponents, nearly all the fuel is consumed. According to a pro-thorium group of British lawmakers, one metric tonne of thorium delivers the same amount of energy as 250 tonnes of uranium.I thought the main draw to thorium was safety? After Fukushima, that would seem to be a beneficial advantage:
Second, and perhaps most important from a “green” perspective, thorium yields little waste and is less radioactive. According to its proponents, residue from the thorium reaction will become inert within 30 years, compared to 10,000 years for radioactive waste currently generated from uranium reactors.
A further advantage thorium has over uranium is its relative abundance in the Earth's crust. The silvery-black metal is estimated to be three to four times more plentiful than uranium, with large reserves existing in China, Australia, the United States, Turkey, India and Norway. Tons of it are known to be buried in the U.S., since thorium is a by-product of rare earth mining.....
One large hole that can be punched in the argument for thorium involves the economics of thorium reactors. Experts say compared to uranium, the thorium fuel cycle is more costly and would require extensive taxpayer subsidies.
Another issue is time. With a viable thorium reactor at least a decade away if not more, the cost of renewable alternatives like solar and wind may come down to a point where thorium reactors won’t be economical. Critics also point out that the nuclear industry has invested too much in uranium reactors – along with government buy-in and a set of regulations around them – to be supplanted by thorium.
As for the “green nuclear” argument, thorium's detractors say that isn't necessarily the case. While thorium reactors produce less waste, they also produce other radioactive by-products that will need safe disposal, including U-232, which has a half-life of 160,000 years.
“It will create a whole new volume of radioactive waste from previously radio-inert thorium, on top of the waste from uranium reactors. Looked at in these terms, it's a way of multiplying the volume of radioactive waste humanity can create several times over,” said Oliver Tickell, author of Kyoto2, speaking to The Guardian.
Science writer Richard Martin states that nuclear physicist Alvin Weinberg, who was director at Oak Ridge and primarily responsible for the new reactor, lost his job as director because he championed development of the safer thorium reactors. Weinberg himself recalls this period:Clearly, there are some serious drawbacks, or we'd have thorium reactors at utility scale. I'm in favor of safe nuclear power, but I've got my doubts about the feasibility of thorium as a major energy source.
[Congressman] Chet Holifield was clearly exasperated with me, and he finally blurted out, "Alvin, if you are concerned about the safety of reactors, then I think it may be time for you to leave nuclear energy." I was speechless. But it was apparent to me that my style, my attitude, and my perception of the future were no longer in tune with the powers within the AEC.Martin explains that Weinberg's unwillingness to sacrifice potentially safe nuclear power for the benefit of military uses forced him to retire:
Weinberg realized that you could use thorium in an entirely new kind of reactor, one that would have zero risk of meltdown. . . . his team built a working reactor . . . . and he spent the rest of his 18-year tenure trying to make thorium the heart of the nation’s atomic power effort. He failed. Uranium reactors had already been established, and Hyman Rickover, de facto head of the US nuclear program, wanted the plutonium from uranium-powered nuclear plants to make bombs. Increasingly shunted aside, Weinberg was finally forced out in 1973.