The case for Thorium. 18. Russia has an active Thorium program.

Russia has an active Thorium program This is a self-contained Thorium Nuclear Reactor on a barge. Coolant readily available. Hoist it a couple of cables and the town to be serviced will have all the power it needs. This is especially useful in the Arctic. Russia is trying to establish Arctic domination, both commercially and militarily. They have over 30 ice breakers, some of them nuclear. U.S. has two, only one of which are operational.
Russia is also trying to commercialize hybrid fusion-fission reactors:
Nuclear Engineering International: 29 May 2018

Russia develops a fission-fusion hybrid reactor.
A new fission-fusion hybrid reactor will be assembled at Russia’s Kurchatov Institute by the end of 2018, Peter Khvostenko, scientific adviser of the Kurchatov complex on thermonuclear energy and plasma technologies, announced on 14 May. The physical start-up of the facility is scheduled for 2020.The hybrid reactor combines the principles of thermonuclear and nuclear power – essentially a tokamak fusion reactor and a molten salt fission reactor. Neutrons produced in a small tokamak will be captured in a molten salt blanket located around tokamak. The facility will use Thorium as a fuel, which is cheaper and more abundant than uranium. Moreover, unlike a fusion reactor, a hybrid will not require super high temperatures to generate energy.

  • A new paper describes computer simulations of a hybrid fusion-fission reactor that runs on thorium.
  • Thorium has benefits compared with uranium reaction and has been endorsed by Democratic presidential candidate Andrew Yang.
  • In the reactor, plasma fusion generates neutrons that fuel subsequent fission.

 

Hybrid reactors reduce the impact of the nuclear fuel cycle on the environment. The concept combines conventional fission processes and fusion reactor principles, comprising a fusion reactor core in combination with a subcritical fission reactor. The results of the fusion reaction, which would normally be absorbed by the cooling system of the reactor, would feed into the fission section, and sustain the fission process. Thorium in a molten salt blanket will enable breeding of uranium-233.

Some of the expected advantages include:

  • Utilization of actinides and transmutation from long-lived radioactive waste;
  • An increase in energy recovered from uranium by a large factor;
  • The inherent  safety of the system, which can be shut down rapidly; and
  • High burnup of fissile materials leaving few by-products.

The hybrid fission-fusion reactor is seen as a near-term commercial application of fusion pending further research on pure fusion power systems.

This is very interesting, and I will follow up when I get more information.

The case for Thorium. 17. Liquid Fluoride Thorium Reactors will lessen the need for an expanded national grid.

Liquid Fluoride Thorium Reactors will lessen the need for an expanded national grid. The National Electric grid is at the breaking point. It needs to be expanded, but neighborhood resistance is great in many areas where they need an expanded grid the most. The grid is also sensitive to terrorism activities.

As we can see the national grid is extensive. It is also under severe strain at peak demand. Wind power will only increase the strain since most wind power is generated where few people live and work. A way to lessen the dependency on the national grid is to sprinkle it with many small to medium sized Thorium Nuclear Power generators. They can be placed on barges in rivers and along the coast where the need is greatest, giving the grid maximum flexibility to respond in  case of an emergency. LFTR’s do not depend on water for their cooling, so they can be placed anywhere, even in extreme arid areas. Since LFTR can be placed very close to urban centers, transmission losses are kept low. (The Texas grid is separately controlled from the rest of the grid.)

The case for Thorium. 16. Liquid Fluoride Thorium Reactors will work both as Base Load and Load Following power plants.

Liquid Fluoride Thorium Reactors will work both as Base Load and Load Following power plants. LFTR’s operate at a much higher temperature than conventional power plants and operate at about 45% electricity conversion efficiency, as opposed to 38% or lower for steam generators. In addition, because of the higher operating temperature it is ideal for hydrogen generation. The reactor would use the electricity generation to satisfy the current demand and produce hydrogen during times of low demand. This hydrogen would be temporarily stored and used for electricity production at peak demand. And  hydrogen power produces only water when burned, no CO2  or polluting fumes are generated. With the objective of reducing the cost of hydrogen production,  solid oxide electrolyser cells (SOECs) are especially well suited.  SOECs operate at high temperatures, typically around 800 °C. At these high temperatures a significant amount of the energy required can be provided as thermal energy (heat), and as such is termed High temperature electrolysis.

The case for Thorium. 15. No need for evacuation zones, Liquid Fuel Thorium Reactors can be placed near urban areas.

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 leads to placing the nuclear plants where there is the least resistance, not where they are needed the most, adding to the strain 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.

The case for Thorium. 14. 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 case for Thorium 13. Virtually no spent fuel problem, very little on site storage or transport.

 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 after their useful life. 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 case for 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 every day 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 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.

The case for Thorium. 11. 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 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. In contrast,  graphite moderated generators can have a positive temperature coefficient which leads to complicated control, necessitating many safety circuits to ensure proper startup, operation and shutdown. Their worst failure mode is they 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 probably the best known.

The case for Thorium. 10. 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.

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 around 700C.  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. 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 case for Thorium. 9. 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.