Liquid Fluoride Thorium Power: Pros and Cons

There is no perfect energy source. Each and every one has its own advantages and compromises. This series will explore the pros and cons of various energy sources.  Learn about other forms of energy generation here.

Last August, I posted an article on Thorium reactors, a form of nuclear power that supposedly overcomes many of the concerns associated with traditional nukes. Despite my admittedly anti-nuclear bias, I had heard enough good things about this technology to want to learn more and share what I learned. The technology has attracted an enthusiastic following, many of who feel that this is the best of all currently available alternatives. Supporters claim that it sufficiently addresses the numerous issues that have made nuclear a less attractive, if not outright frightening option.

Among the concerns about traditional nuclear are the following:

  1.  Proven risks of dangerous meltdowns (e.g. Fukushima. Japan is now shutting down all reactors).
  2.  Very long time required for approval and construction.
  3.  Potential terrorist target.
  4.  Too big to be liable, taxpayers will likely pick up the cost of an accident.
  5.  Highly centralized and capital intensive.
  6.  Non-renewable and rare fuel source: Uranium (much of it controlled by indigenous tribes).
  7.  High level of embedded CO2 in concrete and steel.
  8.  Dangerous radioactive waste lasts 200 – 500 thousand years.
  9.  No operating long-term waste storage sites in the U.S.
  10.  Shipping nuclear waste poses an increased potential risk of spills or interception by terrorist groups.
  11.  Fissile material can be converted into nuclear weapons.
  12.  High construction costs generally requiring subsidies and loan guarantees.
  13.  Competes with renewables for investment dollars.

Unlike conventional light water reactor designs, the liquid fluoride thorium reactor (LFTR) is a type of molten salt reactor (MSR), that was first demonstrated in the 1960s. It is generally considered inherently safer, cleaner and more economically viable than conventional reactors, but was not chosen by DOE as the technology of choice  because it did not produce weapons grade material as a byproduct, something DOE was looking for at the time. That would be considered an advantage today. (11)

This design is less radioactive and more proliferation resistant. Its reaction in a molten-salt reactor (MSR) does produce U233 but that is apparently not a weapons-grade material. Thorium is about four times more abundant in nature than uranium (6). The largest reserves are in Australia, India, and the U.S.

LFTR reactor cores are not pressurized. Any increase in temperature results in a reduction in power, thus eliminating the problematic runaway meltdown scenario. If the fluid should get too hot, a salt plug at the bottom of the tank simply melts dumping the entire mess in to a storage vessel directly below the reactor. (1,4)

The question of waste (8,9,10) is also far better. Thorium produces about a thousand times less waste throughout the supply chain than uranium. It is mostly consumed in the reaction. Of the remaining quantity, which is quite small (I’ve been told it’s  about the size of a coke can for every billion kilowatt hours), 83 percent is safe within ten years and the remaining 17 percent requires 300 years of storage before it becomes safe. While that is still a long time, it is far more manageable than the 10,000 years required for today’s spent fuel.

It is expected to cost far less than conventional reactors and because of its simplicity, it can be assembled in a factory (2) scaled down to the point where one can be carried on the back of a tractor-trailer and used in a distributed manner. (5,12)

The technology already has a large following at sites like Nuclear Green and Energy From Thorium.


  • Carbon-free operation
  • Inherently far safer than conventional light water reactors
  • Abundant fuel (thorium)
  • Chemically stable
  • Currently being developed in China and by US  companies like Flibe
  • Very small amount of  low-level radioactive waste. Should be much easier to manage.
  • Concentrated energy source, requiring far less land than solar
  • Runs round the clock, good base-load and load-following source
  • Less suitable for weapons proliferation that conventional nuclear
  • Relatively low cost and scalable
  • Could potentially be used in a distributed manner
  • Technology is currently at the demonstration phase
  • Requires less cooling water than conventional reactors


  • Non-renewable fuel
  • Still produces hazardous waste (though far less)
  • Can still facilitate proliferation of nuclear weapons
  • Quite different than current technology
  • Primarily conceived as a centralized plant
  • Like all big plants, could be a terrorist target
  • Technology not ready for prime time yet
  • Competes with renewables for investment dollars

Because of the first two items on the cons list, I consider thorium to be ultimately unsustainable in the very long term, though I do believe it can play a significant role for several generations, if needed. For me, the perfect energy source requires no fuel and, like nature, produces no waste. But those that meet that criteria today (e.g. wind, solar) are intermittent and have a low energy density which means they require quite a bit of land, which is also a problem. I suggest you become familiar with thorium energy, as I expect you will be hearing more about it in the future.


What about other energy sources?

[Image credit: US National Archives: Flickr Creative Commons]

RP Siegel, PE, is the President of Rain Mountain LLC. He is also the co-author of the eco-thriller Vapor Trails, the first in a series covering the human side of various sustainability issues including energy, food, and water. Now available on Kindle.

Follow RP Siegel on Twitter.

RP Siegel

RP Siegel, author and inventor, shines a powerful light on numerous environmental and technological topics. His work has appeared in Triple Pundit, GreenBiz, Justmeans, CSRWire, Sustainable Brands, PolicyInnovations, Social Earth, 3BL Media, ThomasNet, Huffington Post, Strategy+Business, Mechanical Engineering, and among others . He is the co-author, with Roger Saillant, ofVapor Trails, an adventure novel that shows climate change from a human perspective. RP is a professional engineer - a prolific inventor with 52 patents and President of Rain Mountain LLC a an independent product development group. RP recently returned from Abu Dhabi where he traveled as the winner of the 2015 Sustainability Week blogging competition.Contact: