"Not only is uranium expensive and rare, it can also be used to build nuclear weapons. These reactors also generate radioactive waste that needs to be safely stored"

Nuclear waste problem only exists today because some people prevented construction of kind of nuclear reactors, which can use spent fuel from others as fuel, by claiming that would cause nuclear proliferation! However, the real world evidence clearly shows that not constructing such reactors never actually prevents any willing countries (like N Korea & Iran) from nuclear proliferation!
Building one and making it work are completely different things. And China's recent history on nukes is not good.
Not the World's first Thorium Reactor. The Oak Ridge National Laboratory operated an experimental Thorium Reactor for 15,000 hours from 1965 to 1969. https://en.wikipedia.org/wiki/Thorium-based_nuclear_power
Expanded Viewpoint
Someone needs to sit down and do an energy audit on this before going one step more. Back in about 1998, an energy audit was done on the nuclear power industry, and it was determined that the amount of carbon based fuels burned in mining and processing Uranium ore into fuel, etc, was MORE than what would have been needed to generate the same amount of electricity in a regular steam plant, if it had just been burned there instead!! What then, was the point of building nuclear power plants?? Here we go again, spending 50 dollars to generate 20 dollars' worth of electricity!
Another case in which the US could have and should have been a generation ahead of the Chinese in this technology. Absent a reliable, robust, affordable grid-scale energy storage solution, clean nuclear is by far the best, most viable alternative to carbon-based energy for base load power.
Reply to Expanded Viewpoint -Thorium comes from waste products of mining. Thorium is estimated to be over three times as abundant as uranium in the Earth's crust and is chiefly refined from monazite sands as a by-product of extracting rare-earth metals.
As FB36 points out, nuclear waste from uranium-fuel reactors can be reprocessed and re-used to extract even more energy from current reactors. Other reactor designs can reduce the high-level nuclear so it has a relatively short half-life on the order of hundreds of years. The amount of waste generated is miniscule, even from current reactors. All the burnt reactor cores from all the reactors in the U.S. since the 1950's would fit in a football field, stacked several feet high. Producing energy from uranium is so efficient that only small amounts are needed. Now that uranium extraction from seawater has been proved practical and economical, there is enough uranium diluted in seawater to provide all the energy needs of humans for a billion years. For all practical purposes, that's "sustainable". Uranium only needs to be enriched to 3 to 5 percent for reactor fuel, far below the amount (20% or higher) that can be used for a weapon. New reactor designs are far safer than previous generations, which were already so safe that nuclear power accidents have resulted in far fewer deaths (dozens) than any other base load power production technology (hundreds to thousands).
Regarding the energy cost of processing uranium, I think most of it is consumed in isotopic separation, not necessary for thorium.

For me, molten salt reactors, particularly using thorium, sound like a good idea, but build one, operate it for a suitable period of time, and then do a proper audit to see if it really is a good idea. There are too many unknowns to start mass-producing them.
Dr. Arjun Makhijani is not a fan or thorium reactors. Read his articles at: https://ieer.org/resources/subject-index/ Use your Edit/find function to find the relevant articles.
There is a Wikipedia article on thorium reactors. Safe nuclear and clean coal are oxymorons. Read the book Insurmountable Risks, by Brice Smith.
Eric Robinson
"One major issue molten salt reactors have to contend with is corrosion, with the radioactive molten salt prone to eating away at piping or other components." - this was solved by, corrosive resistant, Hastelloy-N in the 1960s Molten Salt Reactor Experiment that ran for 5 years at Oak Ridge National Labs, Knoxville TN.