Victor Stenger

snip

And so, it came as a surprise to me to learn recently that such an alternative has been available to us since World War II, but not pursued because it lacked military applications. When the war ended and nuclear reactors were developed to generate electrical power, the designs adopted were based on the same technologies that were used in the nuclear bombs dropped on Japan. These relied on the fission of uranium-235 (U-235) and plutonium-239 (Pu-239).

U-235 constitutes only 0.72 percent of natural uranium, which is mostly U-238, so costly separation is required. Plutonium is not found in nature and must be "bred" by uranium reactors, also a costly process.

It was well known to physicists of the time that another uranium isotope, U-233, is also fissionable. This isotope also does not occur in nature, but can be bred from the element, thorium, which is very common. However, a reactor breeding U-233 also produces U-232, which has a decay chain that generates high-energy gamma rays. This makes U-233 fusion unusable as a weapon, since these gamma rays are very destructive to a bomb's instrumentation and dangerous to the personnel handling it. Furthermore, U-233 is not an efficient breeder of plutonium, since it contains two fewer neutrons than U-235.

Because of its lack of application to weapons, a promising project at the Oak Ridge National Laboratory that was leading toward a thorium reactor was cancelled by the Nixon administration in 1969 in favor of a more efficient plutonium breeder. The Oak Ridge program was advancing the technology of using molten salt as a reactor fuel rather than the solid rods found in existing naval and commercial reactors. It had successfully operated such a reactor for 22,000 hours before being terminated. Liquid fuel offers great advantages in cost and safety over the solid fuel design.

Currently the liquid fluoride thorium reactor (LFTR) is having a resurgence of interest worldwide. Let me list the advantages of an electrical power plant based on LFTR compared to conventional nuclear and fossil-fuel plants:

• Thorium is plentiful and inexpensive. One ton costing $300,000 can power a 1,000-megawatt plant for a year. One pound of thorium yields as much power as 300 pounds of uranium or 3.5 million tons of coal.
• Unlike conventional high-pressure water reactors, LTFR operates at atmospheric pressure, obviating the need for a large, expensive containment dome and having little danger of explosion.
• LFTRs cannot melt down since the normal operating state is already molten.
• LFTRs are stable to rising temperatures since salt expands slowing the reaction. A salt plug kept solid by cooling coils will automatically melt if external power is lost and the fluid drain out to a safe dump tank.
• Salts used are solid at 100 F or higher, so any spilled fuel solidifies instead of escaping into the environment.
• Liquid fuel can be continually cycled through so all the available energy is used, unlike solid fuels that must be removed before they have generated 1-3 percent of the available energy because of damage.
• The radiative waste is much less than from conventional plants and far more manageable.
• Air-cooling possible where water is scarce.
• Should be cheaper than coal, especially if CO2 is sequestered.
• Proliferation resistant. Can't use to build bombs.
• Smaller size and lower cost.
• Could provide the world's energy needs carbon-free for a thousand years.

snip

Work on LFTR is going on worldwide, with research being done in China, France, the Czech Republic, Japan, Russia, Canada, and the Netherlands. The only significant U.S. research is on molten salt reactors, but with no emphasis on thorium. The U.S. may end up buying LFTRs from China. Perhaps WalMart will sell them cheap.

Read more here: http://www.huffingtonpost.com/victor-stenger/lftr-a-longterm-energy-so_b_1192584.html?ref=politics&ir=Politics

Interesting article blue