No need for evacuation zones, can be placed near urban areas. Molten Salt Thorium reactors operate at atmospheric pressure and have a very high negative temperature coefficient, so there is no risk for a boil-over. They are easily made earthquake-safe and no pressure vessel is needed. This will greatly simplify the approval process, no need for elaborate evacuation plans have to be developed. Since the Three Mile Island accident there was a thirty year gap in approvals for new nuclear plants. The “not in my backyard ” mentality reigned supreme, and delay and denial was the rule of the years. But the lawyers still got their share, leading to escalating cost for new nuclear power. In the early days of nuclear power France took the approach of building some of their nuclear plants near the Belgian and German border, so they only had to develop half of an evacuation plan, leaving the other half to their ‘understanding’ neighbors. It also lead to placing the nuclear plants where there was least popular resistance, not where they were needed the most, adding to the strain and efficiency losses on the electric grid. Liquid Fluoride Thorium Reactors have one additional advantage. They do not need access to water, so they can be placed even in desert areas. When a coal fired, or even a natural gas fired plant is decommissioned, it can be replaced in the same place, the electric connections are already there, so there is no need to go through lengthy and costly eminent domain processes ‘to acquire more land, or even expand the electric grid for that location. Thorium power is clean power.
Category: energy
Why Thorium? 16. Liquid Fluoride Thorium Nuclear reactors scale beautifully from small portable generators to full size power plants.
Thorium Nuclear Power generators scale beautifully from small portable generators to full size power plants. One of the first applications was as an airborne nuclear reactor.
Granted this was not a Thorium breeder reactor, but it proves nuclear reactors can be made lightweight. Thorium reactors can be made even lighter as long as they are not of the breeder type.
Lawrence Livermore, Los Alamos, and Argonne national laboratories are designing a self-contained nuclear reactor with tamper-resistant features. Called SSTAR (small, sealed, transportable, autonomous reactor), this next-generation reactor will produce 10 to 100 megawatts electric and can be safely transported on ship or by a heavy-haul transport truck.
This type of reactor can be transported to disaster areas, and provide emergency power, during rescue and rebuilding efforts. This particular reactor still uses solid fuel and steam heat exchanger. A LFTR reactor with a supercritical CO2 gas heat exchanger would be even more compact and efficient.
From these compact designs, Thorium power can be scaled up to any size. The LFTR reactor will be placed on barges and left moored in navigable rivers or in ocean harbors. This will typically be a one or two 250 MW LFTR with reprocessing capabilities. Where there is only road access the LFTR’s will be one or up to six 100 MW LFTR with one reprocessing fuel capability servicing the nuclear units one at a time on a rotary basis. These will come as complete units tested and ready for use on a number of trucks. It is to be noted that no water is necessary for cooling. There can also be 5 and 10 MW power units for freight trains and large towboats. They will not have reprocessing capabilities on board, but will be serviced regularily by refueling and reprocessing stations in key locations. Oceangoing ships will be fitted with LFTR reactors with reprocessing capability. When all of this is done the need for diesel fuel for nearly all shipping by train, barge or ship will be nearly eliminated.
Admittedly there are security risks associated with this arrangement. Locomotives and barges can be stolen, ships can be hijacked, when the whole reactor vessel came on a truck it can be stolen. By having minimum fuel at all time, it increases safety, but it also makes it possible for terrorists and common thieves to steal shipments of fuel and fissile by-products. This means that there must still be strict security measurements for maintaining chain of security for U-233 and Protactinium.
Why Thorium? 15. Virtually no spent fuel problem, very little on site storage or transport. U-232 is the preferred radioactive tracer.
Virtually no spent fuel problem, very little on site storage or transport. I have been following the events at Fukushima Nuclear Power plants disaster with great interest. How ironic that one of the greatest problems was 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. The cost of reprocessing and storing spent reactor fuel will burden us for centuries after the reactors themselves have been decommissioned when their useful life is ended. Molten Salt Thorium nuclear power works differently from conventional Uranium fueled Reactors 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 ten thousand to one in the size of the problem. It is high time to rebuild and expand our Nuclear power generation by switching to Thorium..
The detractors of Thorium like to point out that the Thorium-U233 process generates some U 232 in the presence of free neutrons. U-232 decays with a 69-year half-life through 1.9-year half-life Th-228 to Tl-208, which emits a 2.6 MeV gamma ray upon decay. Gamma rays are easily shielded by clean water, so transportation and storage is not a problem. Rather than being a problem, this is a great asset. The 232U decay chain is the source of the high energy gamma rays that make 232U the preferred tracer isotope. Uranium-232 has a half-life of 69.8 years, and the decay chain terminates at 208Pb (National Nuclear Data Center).
Why Thorium? 14. 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, making possible a simple and safe design enabling simple and consistent feedback. What does that mean? It means that when the temperature of the fissile core rises, the efficiency of the reaction goes down, leading to less heat generated. There is no risk for a thermal runaway. This advantage is also true for Molten Salt Enriched Uranium Reactors. In contrast, graphite moderated generators can have a positive temperature coefficient which leads to complicated control, necessitating many safety circuits to ensure controlled startup, operation and shutdown. Their worst failure mode is they can go prompt critical, and no containment vessel can contain the explosion that would occur, so they were built without one. There have been several major accidents in graphite moderated reactors, with the Windscale fire and the Chernobyl disaster being the largest and best known..
Why Thorium? 13. Molten Salt Liquid Fluoride Thorium Reactors cannot have a meltdown, the fuel is already molten, and it is a continuous process. No need for refueling shutdowns.
refueling shutdowns.
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 to lower the melting point, the operating temperature is held below 650C to allow reasonably priced and available alloys that also withstand high radiation. In its molten form the salt has a very low vapor pressure. The salt flows easily through the heat exchangers and the separators. The salt is very toxic, but since it is completely sealed it is not corrosive. 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. This problem is not yet solved for conventional Nuclear power plants, so spent fuel is stored on site, sometimes for years. In a LFTR the fuel is spent as it is produced, so the fissile inventory is constantly kept at a minimum, and fission products and extra generated U-233 is separated out. this is a much cleaner process than reprocessing spent fuel. The high operating temperature gives the LFTR a much more efficient carnot cycle conversion factor of more than 40%, whereas conventional nuclear plants with water as a coolant medium cannot exceed 38% efficiency.
Why Thorium? 12. Atmospheric pressure operating conditions, no risk for explosions. Much safer and simpler design.
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, leading to a much safer design. (From Wikipedia:)
The LFTR needs a mechanism to remove the fission products from the fuel. Fission products left in the reactor absorb neutrons and thus reduce neutron economy. This is especially important in the thorium fuel cycle with few spare neutrons and a thermal neutron spectrum, where absorption is strong. The minimum requirement is to recover the valuable fissile material from used fuel.
Removal of fission products is similar to reprocessing of solid fuel elements; by chemical or physical means, the valuable fissile fuel is separated from the waste fission products. Ideally the fertile fuel (thorium or U-238) and other fuel components (e.g. carrier salt or fuel cladding in solid fuels) can also be reused for new fuel. However, for economic reasons they may also end up in the waste.
On site processing is planned to work continuously, cleaning a small fraction of the salt as often as practical and sending it back to the reactor. There is no need to make the fuel salt very clean; the purpose is to keep the concentration of fission products and other impurities (e.g. oxygen) low enough. The concentrations of some of the rare earth elements must be especially kept low, as they have a large absorption cross section. Some other elements with a small cross section like Cs or Zr may accumulate over years of operation before they are removed.
As the fuel of a LFTR is a molten salt mixture, it is attractive to use pyroprocessing, high temperature methods working directly with the hot molten salt. Pyroprocessing does not use radiation sensitive solvents and is not easily disturbed by decay heat. It can be used on highly radioactive fuel directly from the reactor. Having the chemical separation on site, close to the reactor avoids transport delays and risks and keeps the total inventory of the fuel cycle low. Ideally everything except new fuel (thorium) and waste (fission products) stays inside the plant.
One potential advantage of a liquid fuel is that it not only facilitates separating fission-products from the fuel, but also isolating individual fission products from one another, which is lucrative for isotopes that are scarce and in high-demand for various industrial (radiation sources for testing welds via radiography), agricultural (sterilizing produce via irradiation), and medical uses (Molybdenum-99 which decays into Technetium-99m, a valuable radiolabel dye for marking cancerous cells in medical scans).
Mo-99 is used in hospitals to produce the technetium-99m employed in around 80% of nuclear imaging procedures. Produced in research reactors, Mo-99 has a half-life of only 66 hours and cannot be stockpiled, and security of supply is a key concern. Most of the world’s supply currently comes from just four reactors in Belgium, the Netherlands, Russia and South Africa, and recent years have illustrated how unexpected shutdowns at any of those reactors can quickly lead to shortages. Furthermore, most Mo-99 is currently produced from HEU targets, which are seen as a potential nuclear proliferation risk.
With the Mo-99 having a half-life of 66 hours and being continuously separated out from the fertile core in a LFTR, this seems to be the ideal vehicle to cheaply produce ample supplies of this valuable medical resource.
While LFTR reactors can be built today safely and profitably, much work remains to be done to achieve the full eight to ten thousand times reduction in TRU waste and maximize the breeding rate of U-233 for optimal speed of expanding the Thorium program.
Why Thorium? 11. Liquid Fluoride Thorium Reactors are earthquake safe, only gravity needed for safe shutdown.
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 or complete electric failure the cold air flow automatically shuts off, and since the fuel is already molten, it will melt the plug, and the molten fluid will run down into channels like pig-iron into heat exchangers that absorb the residual heat.
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 even then the reactor shutdown will be complete safe without any additional power.
One of the advantages of the LFTR reactor is that the fissile compartment is always kept just above critical point for needed power delivery. This means, once it starts draining, the fission process ends immediately. The only nuclear reaction remaining is that the Protactinium generated in the fertile blanket and separator gets converted to U-233 over time, but the amounts are so small that it is always in the safe range.
Why Thorium? 10. Produces isotopes that helps identify, treat and cure certain cancers and other medical conditions.
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. One byproduct generated is a valuable isotope for medical uses, Molybdenum-99 which decays into Technetium-99m, a valuable radiolabel dye for marking cancerous cells in medical scans.
In 2019 The US Department of Energy’s National Nuclear Security Administration (NNSA) selected four companies to begin negotiations for potential new cooperative agreement awards for the supply of molybdenum-99 (Mo-99) without using highly enriched uranium (HEU).
Mo-99 is used in hospitals to produce the technetium-99m employed in around 80% of nuclear imaging procedures. Produced in research reactors, Mo-99 has a half-life of only 66 hours and cannot be stockpiled, and security of supply is a key concern. Most of the world’s supply currently comes from just four reactors in Belgium, the Netherlands, Russia and South Africa, and recent years have illustrated how unexpected shutdowns at any of those reactors can quickly lead to shortages. Furthermore, most Mo-99 is currently produced from HEU (Highly enriched Uranium) targets, which are seen as a potential nuclear proliferation risk.
Why Thorium? 9. Thorium based nuclear power is not suited for making nuclear bombs.
Thorium based Nuclear Power does not produce much Plutonium-239, which is the preferred material used in nuclear bombs. The higher Plutonium isotopes and other TRansUraniums are about as nasty as they get, 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 and to some extent with the Indians. Sweden was and to some extent still is a non-aligned country, so it was not privy to any nuclear 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 nearly all Pplutonium-238, not fissile and as such 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 a 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 wish for were developed the greatest asset of nuclear power became its greatest liability.
Why Thorium? 8. Radioactive waste from a Liquid Fluoride Thorium Reactor decays down to background radiation in 300 years compared to a million years for U-235 based reactors. A Limerick.
The nuclear waste meant for Yucca
would destine Nevada the sucka
But with Thorium we rid
us of waste that is hid
No need for that waste to be trucka!
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.
Where is the storage for spent nuclear fuel and other nuclear waste now? Look at the map, it is scary.
And these are just the U.S. installations!
Many years ago I studied Engineering at Chalmers’ University in Sweden and I thought I would become a nuclear engineer. Sweden had at that time a peaceful heavy water based nuclear power program together with Canada and India. The advantage with heavy water as moderator is that it can use natural, un-enriched Uranium. One of the end products is of course Plutonium 239, the preferred material to make nuclear bombs, but it could also use Thorium, and the end product is then mostly Plutonium 238, used in space exploration, and we were dreaming big. One of the advantages of Thorium as fuel is that it produces about 0,01% of trans-Uranium waste compared to Uranium as fuel. About that time the U.S. proposed we should abandon the heavy water program and switch to light water enriched Uranium based nuclear power. They would sell the enriched Uranium, and reprocess the spent fuel at cost. They also had the ideal final resting place for the radioactive waste products in Nevada. This was an offer the Swedish government could not refuse, at the height of the cold war. This was in the 1960’s! India on the other hand did refuse, and they eventually got the nuclear bomb. Since that meant Sweden was never going to use Thorium as nuclear fuel, and I could not figure out how to get rid of all the radioactive waste products, I switched my attention back to control engineering.
.What did President Trump mean with innovative approaches?
Is this where Thorium comes in!? Thorium solves many problems with nuclear energy. Meanwhile the Biden administration and Congress keep hoarding nuclear waste in local storages.
Len Bilén's blog, a blog about faith, politics and the environment. 
