What is a Liquid Fluoride Thorium Reactor? A type of Molten Salt Reactor, a completely different nuclear reactor than we have been using, with molten fuel cooled by stable salts. (We’ve been mainly using the Light Water Reactor, LWR, with solid fuel cooled by high-pressure water.)
A LFTR can use inexpensive Thorium for fuel (would become uranium inside the reactor). A slightly different type of Molten Salt Reactor (MSR) can consume the uranium/plutonium waste from solid-fueled reactors as fuel. MSRs make no long-term nuclear waste (the fuel is fissioned, not left as waste).
We know Molten Salt Reactors work since we built and operated one — decades ago!
Image “How Does a Fluoride Reactor Use Thorium” from PDF Kirk Sorensen – Thorium Energy Alliance.
- LFTRs, and all Molten Salt Reactors, have no high pressure to contain (no water coolant), and generate no combustible or explosive materials;
- A simple Freeze Plug melts in any emergency. The molten fuel drains to passive cooling tanks where fission is impossible;
- Reactor materials won’t melt under normal or emergency conditions, so radioactive materials stay contained. (Even if a bomb or projectile breaks the reactor vessel, it makes a spill that cools to solid, doesn’t interact with air or water, with most fission products chemically bonded to the salt);
- MSRs would passively cool even without electricity (never uses water);
- Salt coolant can’t boil away (the boiling point of the salt is much higher than the reactor temperature), so loss of coolant accidents are physically impossible.
- The molten fuel expands/contracts with temperature changes. Higher fission rate increases the temperature, which makes the fuel salt less dense, lowering the fission rate — all Molten Salt Reactors are very stable (a “strong negative temperature coefficient of reactivity”).
Much More Economical
- Ambient-pressure operation makes LFTRs easier to build while costing less (no high-pressure steam containment building, no high-pressure pipes);
- Operating cost is less since inherent safety means less complex systems;
- Fuel cost is lower since thorium is a cheap, plentiful fuel; (other MSR designs could eliminate LWR waste as fuel);
- No expensive enrichment or fuel rod fabrication is required, simply add solid or molten thorium or uranium to the molten fuel;
- Total to develop LFTR technology and a factory to mass-produce them, will be less than the $10-12 Billion cost of a single new LWR; then a 100MW LFTR would cost about $200 Million.
- Easy siting, no large water source needed, no large safety zone required. Reactor can be located several meters underground.
Much Less Nuclear Waste
LWR uses ~2% of the fuel, because fission products trapped in the fuel pellets block fission, and the pellets get damaged by radiation and pressure. The rest of the uranium is considered “waste”, to be stored for over 100,000 years. Well, that is waste only if we only use LWR, or other solid-fueled types of nuclear reactors. There are several types of nuclear reactor possible, that can fission All that uranium, plutonium, and other transuranic elements. (God didn’t make useful uranium and defective uranium; it’s the reactor design of LWR that only uses ~2% of the fuel.)
MSR has molten fuel, no fuel pellets, no fuel rods. Some of the fission products, that block fission the most, are gasses — in LWR they are carefully trapped in the pellets, in MSR they bubble right out of the fuel salt and are collected. Most other fission products are easily chemically separated from the circulating fuel salt. Most MSR designs, including LFTR, use over 99% of the fuel.
A LFTR’s waste is safe (radiation levels below the original uranium ore and below background radiation) within 350 years. To produce 1 gigawatt electricity for a year, takes 800kg to 1000kg of thorium or uranium/plutonium waste. 83% of the fission byproducts are safe in 10 years, 17% (135 kg, 300 lbs) within 350 years, no uranium or plutonium left as waste. After that, radiation is below background radiation levels. (Compare to 250,000kg uranium to make 35,000kg enriched uranium for a solid-fueled reactor like LWR, for that same gigawatt-year electricity, all needing storage for 100,000+ years.)
No uranium, plutonium, or other long-term elements in LFTR waste, since they are simply left in the reactor until they either fission or decay to short-term waste. (Standard industrial processing inefficiency of 0.1% leaves 1kg uranium; we can do better than that, but still much less per gigawatt-year than the 5500 kg uranium left from an average USA coal plant!)
Most of the fission products are valuable for industrial use. After a few years, radioactive decay brings them below background radiation, ready for use.
Can Consume Nuclear Waste
Instead of thorium, a Molten Salt Reactor can use uranium-235 or plutonium waste, from LWR and other reactors. (Fast-spectrum MSR can use all isotopes of uranium, not just the 0.7% U235 in natural uranium — with all the safety and stability of MSR.) 800kg of nuclear waste would work in the same reactor instead of 800kg thorium, with about the same fission byproducts, and the same electrical output. Convert 800kg to be stored for 100,000+ years, to 135kg for 350 years and 665kg for 10 years. No “PUREX reprocessing” needed, simply extract the uranium and plutonium (including fission products) from the fuel rod, and put it in a MSR. (In a MSR designed to use a different salt than LFTR, the zirconium cladding of a fuel rod could even be used to make the salt coolant.)
Since no MSR uses water for cooling, there is no storage of water containing radioactive materials, and no concern of stored radioactive water leaking. (MSR can transfer heat to existing equipment such as steam generators, for example replacing the boiler at a coal plant, but doesn’t use water anywhere in the reactor.) Instead of using water, MSR could produce heat to efficiently desalinate water for drinking or farming.
Without needing a huge steam containment building (since there is no high pressure and no steam), LFTRs use a much smaller site. A LFTR containment building would protect the reactor from outside impacts, and have extra radiation shielding, but would be much smaller and less expensive than a LWR containment building. LFTRs can be safely built close to where there is electrical need (10MW to 2GW or more), avoiding transmission line power loss. No water source required. LFTRs could even be deployed for military field use or disaster relief.
Can Desalinate Water and Produce Vehicle Fuel
In addition to delivering carbon-free electricity, LFTRs high temperature output can desalinate water (which we need in some areas even more than electricity, and we will need more as the world population grows).
LFTRs also can generate carbon-neutral vehicle fuels, from water and carbon dioxide (from the atmosphere or ocean or large CO2 sources such as coal plants). The high heat of a LFTR (over twice what a LWR can generate) can split CO2 and split water, so making gasoline will be affordable.
Carbon dioxide in the air enters the oceans, making acid. The acid is already killing plankton and other ocean life: the carbonic acid dissolves their “shells”. Researchers are exploring methods of using MSR heat to extract CO2 from solid materials containing a lot of CO2, store the carbon and release or use the oxygen, and then we could put those CO2-absorbing materials into the ocean to remove CO2 from the water. (Storing CO2 in a solid would work; storing compressed CO2 underground has a huge risk of leaks that would suffocate life on the surface.)
LFTRs are less expensive and more environmentally friendly than other sources of base-load power or grid power storage, needed to supplement wind and/or solar power.
The total cost of developing LFTR technology and building assembly line production (like assembly line production of aircraft, with better safety standards than is achievable with on-site construction, at much lower cost) will be much less than the $10-$12 Billion for a single new solid-fueled water-cooled reactor or single nuclear waste disposal plant. With sufficient R&D funding (around $1 billion), five years to commercialization is entirely realistic (including construction of factories, <$5 Billion), and another five years for a national roll-out is feasible. (Unfortunately, the U.S. Nuclear Regulatory Commission says they will start writing licensing and regulations in 30 years.)
Completely Different Reactor
There is very little LFTRs have in common with the solid fueled, water cooled reactors in use today. (Using thorium in a solid fueled, water cooled reactor, such as India is doing, does not give the safety and waste-reducing benefits of a molten fueled, salt cooled reactor.)
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