Add new comment

       I thought it was time to revisit the idea of using thorium as a fuel for nuclear power reactors. India is interested in thorium fuel because it has a lot of thorium and little uranium.
       One selling point for thorium is the idea that you cannot use thorium reactors to create materials for nuclear bombs. In 2005, the International Atomic Energy Agency stated that “Thorium-based fuels and fuel cycles have intrinsic proliferation resistance.”  Simply put, this is just not true. The most abundant isotope of thorium is Th-232 which can be bombarded with neutrons to produce protactinium 233. Ph-233 naturally decays to uranium 233 which is highly radioactive and can be used for nuclear weapons production. U-233 allows simpler nuclear bombs to be created with less materials than U-235. It is possible to build molten salt breeder reactors that use thorium as a fuel and produce U-233 in a continuous process.
       While it is true that thorium does not need to be enriched to be used in a reactor, it is also true that thorium is not fissile. In order to be used in a reactor, thorium must be primed with a neutron producing materials such as plutonium. If the reactor is a breeder reactor, it can eventually produce more radioactive materials than it burns and will not require further inputs of radioactive materials.
       
      Another supposed advantage of thorium is that there is more thorium in the crust of the Earth than there is uranium. While this is true, there is vastly more uranium in the ocean than thorium. Scientists are on the brink of extracting uranium from sea water at a cost near that of mining uranium without all the environmental problems. (India also have a very long coastline with the ocean and would be able to extract uranium.)
      It is often claimed that the waste produced by a thorium reactor is not as nasty as that produced by a conventional uranium fueled power reactor. A thorium reactor produces fewer transuranic elements which have half lives in the ten thousand years and beyond. But there are fast breeder reactors fueled by uranium and plutonium which also produce fewer transuranics, so this is not unique to thorium reactors.
       A concern about waste from thorium reactors is that it contains U-232. U-232 emits powerful abundant gamma rays which are very dangerous making the spent fuel more difficult to handle. This means that more shielding is required which raised the cost of thorium fuel handling and/or reprocessing.
     Thorium reactors have been a subject of research for seventy years. Not one commercial thorium reactor has ever been built. It will take a decade or more to license, construct and turn on the prototype of a thorium reactor. Then it would need to be tested for more years to better understand the impact of the conditions in the reactor on the materials that it is constructed from.
       With the cost of new renewable power plants dropping below the cost of conventional nuclear power plants, there is just no good economic reason to develop thorium power plants. The development of a thorium power plant would require massive government subsidies that could be much better spent advancing the technologies required by renewable power plants.