If I may direct your attention to the excellent blog, Energy From Thorium run by a man who's father used to be a researcher at the Oak Ridge National Laboratory (ORNL). ORNL was a government project that was setup during the mid 1960's to test the viability of a molten salt reactor. A molten salt reactor is unlike a light water reactor in that it does not use solid fuel pellets of enriched uranium. Instead, the radioactive isotopes are chemically bonded with a halogen such as chlorine or flourine to form a liquid mineral salt that recirculates around the reactor chamber during the reaction.
A molten salt reactor has several advantages over the traditional light water reactor design. First and foremost, it is physically impossible for a molten salt reactor to experience a meltdown since the nuclear fuel is already in a molten state as the reactor operates at a much higher temperature than a light water reactor. There is a cooled plug of sodium at the bottom of the reactor chamber that would heat up and melt during abnormally high temperatures. This would cause the reactor core to drain out into an underground container where it can cool and be safely disposed of during an emergency. Secondly, the actinides that result as a byproduct of nuclear fission would never leave the reactor chamber so there would be little, if any leftover material to be disposed of. As a third advantage, it has a much higher fuel efficiency to energy production ratio than a light water reactor for the same amount of fuel consumed. There is also the fact that molten salt reactors are quite flexible in the isotopes that they can use for energy.
As a variant of the MSR design, the MSR can operate on a closed nuclear fuel cycle between thorium and U233. This produces 10% more fuel than it consumes each year which can eventually be collected to start a new MSR. Finally, the use of flourine instead of chlorine for the fused salt mixture would be advantageous because of the ease of isotopic seperation. In short, this variant of the MSR design is known as a liquid flouride thorium reactor (LFTR).
There is an intriguing article about the history of the Oak Ridge project on the Energy From Thorium blog I mentioned earlier and how it was single handily ruined by one man named Milton Shaw. Because of this, the LFTR project has been dead and buried since the early 1970's. There were managerial issues that resulted from Shaw's mismanagement of the Oak Ridge staff and the bitterness that resulted.
Also, due to the political climate in the US which is deeply paranoid about all things with the word "nuclear" in the title, the LFTR has little hope of ever being built in America. However, all is not lost as France, Japan, India, and Russia are all evaluating the LFTR concept which will probably enter the construction phase very soon in these countries. The US will probably continue to waste time and money on "renewables" and "clean coal" for its energy supply in the foreseeable future, leading to rolling blackouts being the norm for much of the country at peak demand.