Virtually no spent fuel problem, very little on site storage or transport. I am following the events at Fukushima Nuclear Power plants with great interest. How ironic that the greatest risk is with the spent fuel, not with the inability to shut down the working units. The spent fuel issue is the real Achilles’ heel of the Nuclear Power Industry. Molten Salt Thorium nuclear power works differently from conventional Uranium as the fissile fuel gets generated in the breeding process itself and nearly all fuel gets consumed as it is generated. When the process shuts down, that is it. Only the radioactivity that is en route so to say will have to be accounted for, not everything generated thus far in the process. The difference is about one to ten thousand in the size of the problem. It is high time to rebuild and expand our Nuclear power generation by switching to Thorium.
Category: thorium
The need to develop Thorium based Nuclear Energy as the major electric energy supply. 11. Atmospheric pressure operating conditions, no risk for explosions.
Molten Salt nuclear Reactors operate under Atmospheric pressure conditions, no risk for explosions. Materials subjected to high radiation tend to get brittle or soften up. Molten Salt Thorium nuclear reactors operate under atmospheric conditions so the choice of materials that can withstand both high temperatures and high radiation is much greater, leading to a superior and less expensive design. There is no high pressure gas buildup and the separation stage can be greatly simplified.
The need to develop Thorium based Nuclear Energy as the major electric energy supply. 10. Molten Salt Nuclear Reactors have a very high negative temperature coefficient leading to a safe and stable control.
Molten Salt Nuclear Reactors have a very high negative temperature coefficient leading to a safe and stable control. This is another beauty of the molten salt design. The temperature coefficient is highly negative, leading to a safe design with simple and consistent feedback. What does that mean? It means that if temperature in the core rises, the efficiency of the reaction goes down, leading to less heat generated. There is no risk for a thermal runaway. In contrast, graphite moderated generator can have a positive temperature coefficient which leads to complicated control, necessitating many safety circuits to ensure proper operation and shutdown. Their failure mode is they go prompt critical, and no containment vessel can contain the explosion that would occur, so they are built without one.
The need to develop Thorium based Nuclear Energy as the major electric energy supply. 9. Molten Salt Thorium Reactors cannot have a meltdown, the fuel is already molten.
With Molten Salt nuclear Reactors there is no risk for a meltdown, the fuel is already molten, and that is a safe design. The fissile fuel in a Thorium reactor is U-233 in the form of UraniumFluoride (UF4) salt which also contains Lithium and Beryllium. In its molten form it has a very low vapor pressure. The salt flows easily through the heat exchangers and the separators. The salt is very toxic, but it is completely sealed. Being a fluid, it is constantly mixed for optimum efficiency. The reactor will never have to be shut down for refueling, it is a continuous flow process. Uranium-235 Nuclear reactors on the other hand have to be shut down for refueling and rebalancing of the fuel rods a little more often than once every two years. The average shutdown is 35 days, or about 5% of the time. Then comes the major problem of safely and securely transporting and reprocessing the spent fuel.
The need to develop Thorium based Nuclear Energy as the major electric energy supply. 8. Molten Salt Thorium Reactors are earthquake safe.
Molten Salt Thorium Reactors are earthquake safe. Thorium reactors have a very simple and compact design where gravity is the only thing needed to stop the nuclear reaction. Conventional nuclear reactors depend on external power to shut down after a SCRAM, where poison rods fall down to halt the reaction. The next figure shows the concept of a Thorium reactor.
The idea is to empty the fissile U-233 core through gravity alone. All that is needed is a melt-plug that is constantly cooled by cold air. In an earthquake the cold air flow automatically shuts off, and since the fuel is already molten, it will then run down into channels like pig-iron into cooling heat exchangers with water supplied through gravity alone. 
As we can see the reactor hardened structure is compact, and can be completely earthquake and tsunami proof. What can be sheared off are the steam pipes and external power, but the reactor shutdown will complete safely without additional power, even if the earthquake is so bad the reactor is broken into pieces.
The need to develop Thorium based Nuclear Energy as the major electric energy supply. 7. Produces isotopes that helps cure certain cancers.
Produces isotopes that helps cure certain cancers. For decades, medical researchers have sought treatments for cancer. Now, Alpha Particle Immunotherapy offers a promising treatment for many forms of cancer, and perhaps a cure. Unfortunately, the most promising alpha-emitting medical isotopes, actinium-225 and its daughter, bismuth-213, are not available in sufficient quantity to support current research, much less therapeutic use. In fact, there are only three sources in the world that largely “milk” these isotopes from less than 2 grams of thorium source material. Additional supplies were not forthcoming. Fortunately, scientists and engineers at Idaho National Laboratory identified 40-year-old reactor fuel stored at the lab as a substantial untapped resource and developed Medical Actinium for Therapeutic Treatment, or MATT, which consists of two innovative processes (MATT-CAR and MATT-BAR) to recover this valuable medical isotope.
The need to develop Thorium based Nuclear Energy as the major electric energy supply. 6. Thorium based nuclear power is not suited for making nuclear bombs.
Thorium based Nuclear Power does not produce Plutonium239, which is the preferred material used in nuclear bombs. The higher Plutonium isotopes and other TRansUraniums are about as nasty as they get, and need expensive protection against terror attacks, and need to be stored for a very long time.
One anecdote from my youth. The time had come to apply to University, and to my delight I was accepted to Chalmers’ University in Sweden as a Technical Physics major. I felt, maybe I can do my part by becoming a Nuclear Engineer and help solve the energy needs of the future. The Swedes at that time championed the heavy water – natural Uranium program together with the Canadians. Sweden is a non-aligned country, so it was not privy to any atomic secrets, it had to go it alone. They settled on the heavy water moderated natural Uranium process because Sweden had an ambition to produce its own nuclear bomb. Officially this was never talked about, and I was not aware of it at that time. They could have gone with Thorium instead, but a Thorium based nuclear reactor produces very little Plutonium, and what it produces is PU-238, not suitable for bomb making.
I was excited to learn about all the possibilities and signed up for a couple of nuclear classes. One lab was to design a safety circuit, then run the heavy water research reactor critical and hopefully watch the reactor shut down from the safety circuit before the system safety circuit shutdown. About that time the word came that U.S. will sell partially enriched uranium at bargain basement prices if Sweden agreed to abandon the heavy water project and sign the nuclear non-proliferation treaty, a treaty being formulated by U.N.
Sweden was in awe about U.N, all the problems of the world were to be solved through it, and it had such capable General Secretary in Dag Hammarskjöld, a Swede. I looked at the light water, partially enriched Uranium nuclear power plants being developed and decided to have no part with it, not due to safety concerns but it was the design that produced the most nuclear waste of any of the available designs. At that time there was still optimism that fusion would be ready by about the year 2010 or so. The cost of maintaining spent fuel in perpetuity was never considered, so light water reactors became the low cost solution.
India on the other hand refused to join the nuclear non-proliferation treaty, kept their heavy water program going and had by 1974 produced enough plutonium for one nuclear bomb, which they promptly detonated. They still use heavy water moderated reactors, but since India is low on Uranium but rich in Thorium they have now converted one heavy water reactor to thorium with a Plutonium glow plug. It went on-line in 2011.
They are also developing molten salt Thorium reactors, but full production is still a few years off.
There we have it. We could have gone with Thorium from the beginning, but the cold war was on, and the civilian peaceful use of nuclear energy was still all paid for by nuclear weapons research and development. Once all the bombs we could ever need were developed the greatest asset of nuclear power became its greatest liability.
The need to develop Thorium based Nuclear Energy as the major electric energy supply. 5. Radioactive waste from an LFTR decays down to background radiation in 300 years compared to a million years for U-235 based reactors.
Radioactive waste from an LFTR (Liquid Fluoride Thorium Reactor) decays down to background radiation in 300 years instead of a million years for U-235 based reactors. Initially LFTRs produce as much radioactivity as an U-235 based nuclear reactor, since fission converts mass to heat, but the decay products have a much shorter half-life. See the figure below.
The need to develop Thorium based Nuclear Energy as the major electric energy supply. 4. Thorium based nuclear power produces Pu-238, needed for space exploration.
A Thorium based nuclear power generator produces Pu-238 as one of the final TRansUranium products, which is in short supply and much in demand for space exploration nuclear power.
NASA relies on pu-238 to power long-lasting spacecraft batteries that transform heat into electricity. With foreign and domestic supplies dwindling, NASA officials are worried the shortage will prevent the agency from sending spacecraft to the outer planets and other destinations where sunlight is scarce. Thorium reactors produce PU-238 as a “free” byproduct. In 2009 Congress denied a request to produce more Pu-238 by traditional means, instead relying on Russia to sell us the plutonium. (Remember the Russian reset?) Russia made their last delivery in 2010. PU-238 production has since been restarted by converting Ne-237 to Pu-238 at a cost of 8 million dollars per kilogram. The Ceres-Dawn spacecraft used over 22 Kg of Pu-238 as electricity generator.
The need to develop Thorium based Nuclear Energy as the major electric energy supply. 3. One ten-thousandth of the TRansUranium waste compared to a U-235 based fast breeder reactor.
A Thorium based fast breeder nucear reactor produces much less TRansUranium waste, 0.01% waste products compared to a Uranium-235 fast breeder. The Thorium process has a much higher efficiency of fission than the Uranium process. See the figure below. 
Pu = Plutonium, Am = Americum, Cm = Curium, all TRansUraniums, nasty stuff.
With Thorium based Nuclear power, there are no real problems, with traditional U235 power long tern storage is an immense and urgent problem, and has been since the 1960’s. At that time Sweden had a heavy water U-238 nuclear power program going, but abandoned it in favor of traditional U-235 power. U.S. promised to provide the material and take care of the reprocessing and final storage of all nuclear waste at cost if Sweden joined the nuclear proliferation treaty. Reprocessing was to be done in Washington State, and one of the final storage sites mentioned was Yucca Mountain in Nevada, having the ideal Geological properties.
Time goes by and in 1982 – Congress passed the Nuclear Waste Policy Act, requiring the establishment of a deep geologic repository for nuclear waste storage and isolation. Yucca Mountain was high on the list out of of 9 possible sites.
Time goes by, and Congress is still not able to decide on a solution. Meanwhile, TRU’s from spent and reprocessed fuel is piling up in less than ideal locations. Thorium based nuclear power would go a long way to alleviate this problem.
Len Bilén's blog, a blog about faith, politics and the environment. 