4th Gen is not a technology so much as an effort to select candidate technologies and push their development forward.

The most general problem with the various Thorium fuel cycles in particular is that they are pretty much useless for making nuclear weapons, and because they were only useful for energy production, they did not attract attention from those aiming to use nuclear power production as a rationalization for spending on nuclear weapons technologies.

Now, from some perspectives, that disadvantage is an advantage.

The proliferation question raised in the post seems a bit off:

The energy amplifier would produce very little plutonium, so the design is believed to be more proliferation-resistant than conventional nuclear power (although the question of uranium-233 as nuclear weapon material must be assessed carefully).

In the Thorium fuel cycles, a certain portion of Uranium 232 is produced, which cannot be chemically separated from Uranium 233, but which is highly radioactive and so easier to detect in transit than U233.

As far as this:

Each reactor needs its own facility (particle accelerator) to generate the high energy proton beam, which is very costly.

... I am not sure that this applies to a molten salt thermal thorium reactor. This appears to be a different technology.

The big problem is that the proposed molten thorium trials all seem to involve 20 year time horizons, so they are more promising as paths to process long lived transuranium nuclear wastes than as options as a medium term stopgap to fill any supposed "energy gaps" in the shift to an all-renewable energy system.


I've been accused of being a Marxist, yet while Harpo's my favourite, it's Groucho I'm always quoting. Odd, that.