Note that this very different to the molten salt LFTR design. With solid fuel it is very hard to prevent protactinium capturing neutrons, which means problems for breeding and waste and probably operational constraints as well.
The LFTR is such a beautiful consistent design but it is very different from ordinary reactors.<p>Also the title is inaccurate as different thorium reactors have been designed, built and operated. See MSRE and THTR-300 for example.