One reason also very much overlooked is that the entire nuclear industry makes the majority of its money from fuel fabrication. Making the bundles of fuel rods for PWRs and BWRs is a recurring, reliable source of income for the lifetime of the plant and any innovation into thorium or other models would take away that cash cow.
To clarify your point: utilities aren't usually in the fuel fabrication business, but some engineering firms are, like Westinghouse. They provide the designs, expertise during and after construction and fuel. And there's only a couple of vendors, so if you want to open up a nuclear power plant it's on their terms.
Yes. You're right. Utilities are told by the regulations to pay the engineering firms so that they can operate. I wish they had more choice other then the big ones but no one seems to be able to enter the market.
That's true that thorium would upend the ceramic uranium pellet market if if was a prevalent design, but it's not. The fuel fabrication business is tiny compared to most other segments of the energy market. It's probably not even the main revenue stream for a company like Areva. Remember, the nuclear industry is not a vertical industry like oil that takes the product from the ground to the service pump. It's a scattering of smaller service companies, small mining companies, and construction that are dwarfed in size in comparison to fossil fuel companies.
