It will be profitable when done with the right reactor design. Today's PWR, BWR, designs are too expensive. E.g. Hinkley C in Britain is horrendously expensive. ThorCon (a startup company aiming to make molten salt reactors (MSR), using thorium), reckon they can make a safer reactor, within 6 years, for 20% of Hinkley C prices. ThorCon are not unique. There are a host of other startups and molten salt reactor designs: Transatomic Power, Terrestrial Energy, Seaborg Technologies, Flibe Energy, Moltex SSR, Chinese designs, the Russian MOSART, the EVOL MSFR in France, Japanese, and Czech reactors. Bill Gates TerraPower are said to be working on a molten salt reactor too.
- There are 3 practical nuclear fuels (fissile materials): plutonium-239, uranium-235, and uranium-233 (Pu-239, U-235, U-233).
- Uranium consists of a natural mixture of two isotopes: U-238 : U-235, in a ratio of 1000 : 7. Only U-235 is fissile. It must generally be concentrated 5 times (or more) to be used as fuel. In a reactor some of the U-238 "breeds" to Pu-239. U-235 is the only naturally occurring fissile material.
- There is about 3½ times more thorium available in the world than uranium. Thorium can be 'bred' to make a kind of uranium not found in nature : U-233. (much like Pu-239 is bred from U-238) U-233 performs better than any other fissile material in a thermal nuclear reactor (and 99%+ of reactors are thermal). This is the reason nuclear engineers love it.
- A molten salt reactor is a very good natural fit for thorium. Molten salt reactors are also:
- safer - they do not use water compressed at 80 atmospheres. So the possibility of catastrophes like Chernobyl or Fukushima is eliminated.
- more efficient - because they operate at much higher temperatures (almost 400ºC above a PWR temperature), they convert more heat to electricity
- potentially less expensive - the intrinsic safety of a MSR allows many expensive safety boondoggles to be dispensed with.
- for more see: Advantages of molten salt reactors
The magic of thorium is really uranium-233. Poor uranium-233 had all its limelight stolen by the thorium upstart. U-233 has excellent neutronic performance in the thermal neutron spectrum : 90.3% of neutrons hitting a U-233 atom cause fission and release the atom's energy. Only 7.7% of neutrons are wasted (captured and absorbed). The fission : capture ratio (table below) shows that U-233 is 3.1 times better than Pu-239. I'm measuring this performance in terms of fissionable atoms (and neutrons) wasted. The more that are wasted the more difficult it is for nuclear power to be sustainable. To be sustainable we must be able to breed more fissile material from thorium or uranium-238 than we use up in make energy. The couple: thorium and uranium-233 are sustainable in both the thermal and fast neutron spectra.
In practice, uranium-233 can only be made from thorium. That's why thorium is talked about. But it's really about uranium-233.
The relative performance of 3 fissile materials U-233, U235, Pu-239 under thermal neutron bombardment (aka - in a reactor) :
|capture||fission||total||% fission||fission : capture ratio|
Now it's not so much that plutonium-239 and uranium-238 don't make a sustainable couple too. They do. But it's U-238 + Pu-239 for the fast neutron spectrum only, but thorium-232 + U-233 for either the fast or thermal neutron spectra.