Any Molten Salt Reactor, whether using U-235 (what current Light Water Reactors use), or converting Thorium to U-233, or converting U-238 to Plutonium-239, or using U-238 directly, has big advantages over LWR.
LWR uses <3% of the fuel, because of the solid fuel encased in “pellets”. The uranium isn’t somehow defective, the design of the pellets blocks fission as fission products accumulate inside them. (Thorium in those pellets, like India is doing, doesn’t change fuel usage much.)
Most designs of Molten Salt Reactors use over 99% of the fuel. In a Molten Salt Reactor, such as LFTR, thorium’s big benefit is how plentiful it is. There is No Long-Term Toxic Waste Storage with a Molten Salt Reactor.
The safety issues and expense of LWR come from use of water as a coolant (very high pressure, and safety systems, and steam containment building, all from using water). Molten Salt Reactors use very chemically stable salts, several hundred degrees below their boiling points, to transfer the heat outside the reactor. Atmospheric pressure operation (since far below boiling temperature) is safer and easier to build.
The fuel is dissolved in, and chemically bound to, the salt, and simple thermal expansion gives it an extremely stable reaction rate. The fuel can not get hot enough to melt through the reactor material. (In LWR, the center of the fuel pellets is always hot enough to melt the reactor materials.) http://liquidfluoridethoriumreactor.glerner.com/2012-liquid-fluoride-thorium-reactors-have-passive-and-inherent-safety/
MSRs use no water. (We can transfer heat to current steam-driven electric generators, like are used at coal plants, but the reactor uses no water.) They would be factory assembled, and shipped in standard trucks. They can produce electricity in deserts, or desalinate water, or make CO2-neutral gasoline from CO2 and water, or be deployed to disaster areas.
Wind and solar are intermittent. They simply can not power the world without using “base load” power to fill in when they aren’t generating enough. Sorry, power storage systems capable of supplying a city during a month of bad weather are enormously expensive, except of course compared to the cost of trans-global power grids!
Nuclear power is the only base load power without CO2 and/or methane, and MSR is the low pressure, low risk, low waste type of nuclear reactor.