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Description
A very simple cartoon representing a Liquid Fluoride Thorium Reactor or LFTR (pronounced like "lifter"), and coupled power system.

After some thought, I decided to expound a bit on nuclear power, since I mentioned it briefly in my previous chapter of SW:TotOR . I am a strong proponent of nuclear power. I know that nuclear power is a highly contentious subject and can be a hot-button issue for some folks, so hopefully this won't smash people's toes too hard.

While nuclear fusion (the smashing of light elements together to make heavier ones) is the holy grail of all nuclear technology, no one seriously considers that fusion power can be made ready earlier than the next 50 to 100 years (and 50 years ago, people thought fusion power would be ready by now). So while nuclear fusion is the future, nuclear fission (the splitting of heavy atoms to make lighter ones) is still the present.

That said, the fission technology currently employed by today’s nuclear power plants is terribly deficient and outdated. Vastly superior technologies exist, but their adoption is hindered by problems more political than technical. So, while I believe nuclear power should be expanded to meet the majority of humanity’s energy needs, it’s not with what’s currently in use.

The problem with virtually all nuclear tech in the world today is that it’s based on one concept, unchanged since the 1950s: the Pressurized Water Reactor (PWR). Solid fuel heats up liquid water. That is essentially the beginning and end of the issue: liquid water is directly touching the nuclear core. Because water boils at 100*C, and that is not nearly hot enough to generate electricity efficiently, the primary coolant loop must be held at extreme pressure so the water can reach +300*C without boiling. If this pressure is lost, the water will instantly flash to steam and escape the core, usually damaging or destroying it in the process. The now coolant-free nuclear core rapidly heats up, to the point even the ceramic fuel rods can melt down into what’s charmingly known as corium lava. We’ve seen this happen in the Chernobyl and Fukishima disasters and the Three Mile Island accident.

There’s another issue, less catastrophic but just as pressing: current reactors do a really crummy job at releasing the energy in their nuclear fuel. Most reactors “burn” U-235, a specific isotope of uranium that only accounts for 0.07% of all uranium in the world. The remaining 99.3% is U-238 or “depleted" uranium, and that gets tossed or only partially converted into Pu-239, an isotope of plutonium that can also be “burned”. So, yeah — less than 1% of the energy of uranium actually gets used. And then low thermodynamic efficiency of converting the heat released into electricity, due to the relatively low temperature of the heated water, is just insult to injury. If your car had an efficiency of less than 1%, I think you’d throw a fit and junk it.

There’s a better way: the Liquid Fluoride Thorium Reactor (LFTR). The nuclear fuel is dissolved in a carrier salt, like lithium-beryllium fluoride or "FLiBe". When in operation, this salt is already melted, so “meltdown” is now an irrelevant term. This salt does not need to be pressurized — it boils well above 1400*C. No water touches the core. Even the turbines that spin in the generators can be water-free. A liquid-fueled reactor is so much different than a solid-fueled one, and is vastly superior.

And the main fuel of a LFTR, thorium, is 4X more abundant than all the uranium on earth, 400X more abundant than U-235, and 100% of it is converted into useful fuel, unlike natural uranium. And you can dig up thorium anywhere. Thorium converts into U-233 in a LFTR, the second isotope of uranium than can be fissioned, and is not found in nature. In a properly running reactor, the total quantity of U-233 remains the same: Thorium goes in, short-lived fission products come out. That’s the true beauty of the thorium fuel cycle. In regular reactors, nuclear waste from uranium and plutonium remains dangerous for nearly a million years. A LFTR produces less than 2% of the long-lived actinide wastes of regular reactors, and the rest remains dangerous for at most only 300 years. Most of it is safe in only 10 years. While not a trivial length of time, thorium beats the pants off the conventional U-Pu fuel cycle. So little waste is produced that long-term storage costs are no longer insurmountable.

Even better, a LFTR can be configured to consume the long-lived actinide wastes produced by current U-Pu cycle reactors. Our growing stockpiles of spent nuclear fuel can be managed and eliminated.

The primary salt loop in a LFTR holds the fissile U-233 fuel. On contact with a graphite moderator in the core, the U-233 splits and releases heat (graphite-free designs exist, but require more U-233 to “turn on”). The secondary loop holds the thorium. This loop, which blankets the first, captures neutrons released from fission and converts the thorium into more U-233, which is then extracted and sent to the primary salt loop. The third and final salt loop carries no uranium, thorium, or nuclear fuel/products at all — its job is simply to carry the heat to the generators, which can use helium, nitrogen, or carbon dioxide to turn the turbines. The only place water enters the facility is to cool the turbines, and even then they can be air-cooled instead, completely locking out water from the equation.

LFTRs manage to be both fuel-efficient and thermodynamically efficient at the same time. 100% of mined thorium can be converted into U-233 and fissioned. If nickel plumbing is used, salt temperatures up to 750*C can be used, with more expensive molybdenum or carbon-fiber plumbing, up to 1350*C. Thermodynamic efficiency in a heat engine is determined almost entirely by the hottest and coldest parts of the system. For the hottest possible salt, cooled to room temperature by air or water, efficiencies up to 57% can be achieved. Compare that to ~30% for regular reactors that have an operating temperature of only 300-350*C.

Being liquid-fueled, LFTRs have two safety features no solid-fueled reactors can boast. When the salt heats up, it expands and gets less dense, pushing the dissolved fuel out of the core — the reaction rate drops. A “runaway” reaction is virtually impossible, especially with the graphite-free designs. Even then, if the salt does get too hot, a freeze-plug will melt and all the salt in the reactor will drain away into criticality-safe drain tanks, where it will cool and solidify, stopping the reaction in its tracks. Even if all power is lost or there is physical damage to the reactor. No steam explosions, no meltdowns — everything stops.

We can run the world on thorium, and there’s enough to last a thousand years. And when fusion power comes of age, we won’t even need it that long.

It would be a mistake to ignore this technology and wait for fusion. Fossil fuels we rely on today, like coal, do far more damage than just release greenhouse gasses into the air. Sulfur dioxide, nitrogen dioxide, and carbon dioxide fall back to earth as acid rain. Coal-fired power plants release uranium and mercury and other hazardous wastes into the air that you and I breathe (ironically, coal releases more radioactive waste into the environment than actual nuclear reactors do!) and the water we drink. You don't need to believe in anthropological global warming to see how stupid it is to keep releasing billions of tons of pollutants into our air, water, and soil every single year. Contrary to the humorous rhyme, the solution to pollution is **not** dilution.

Thorium reactors are also very resistant to weapon proliferation, despite the fact they breed fissile U-233 out of non-fissile thorium. Due to inevitable and unavoidable side reactions, all the fissile fuel in a LFTR is contaminated with U-232, which is a very powerful gamma-ray emitter, and cannot be separated. No harm is done while inside the reactor, but these gamma rays will fry the sensitive electronics of any nuclear bomb with out very heavy and bulky shielding, as well as any hapless idiot who tried to build one. These gammas are also easily detectable with long-range sensors, so any movement of the fissile fuel will be noticed. Bomb-grade Plutonium-239 can be extracted from our current spent nuclear fuel, and its requires only minimal shielding to handle.

Admittedly, not everything is known about salt reactors, including the LFTR. The technology has been mothballed since the 1970s, despite its success, mostly because these reactors couldn't be used to make nuclear bombs for the government. But interest has seen a resurgence since the early 2000s. Attacking the tech because "It's nuclear, therefore evil" will not help our planet's energy needs. Wind, solar, and hydro power can't scale that far, and fossil fuels will only continue to foul our nest.

We need more energy, not less.

For a much more detailed primer on molten salt reactors and the LFTR, see Liquid Fluoride Thorium Reactor .

Description
A very simple cartoon representing a Liquid Fluoride Thorium Reactor or LFTR (pronounced like "lifter"), and coupled power system.

After some thought, I decided to expound a bit on nuclear power, since I mentioned it briefly in my previous chapter of SW:TotOR . I am a strong proponent of nuclear power. I know that nuclear power is a highly contentious subject and can be a hot-button issue for some folks, so hopefully this won't smash people's toes too hard.

While nuclear fusion (the smashing of light elements together to make heavier ones) is the holy grail of all nuclear technology, no one seriously considers that fusion power can be made ready earlier than the next 50 to 100 years (and 50 years ago, people thought fusion power would be ready by now). So while nuclear fusion is the future, nuclear fission (the splitting of heavy atoms to make lighter ones) is still the present.

That said, the fission technology currently employed by today’s nuclear power plants is terribly deficient and outdated. Vastly superior technologies exist, but their adoption is hindered by problems more political than technical. So, while I believe nuclear power should be expanded to meet the majority of humanity’s energy needs, it’s not with what’s currently in use.

The problem with virtually all nuclear tech in the world today is that it’s based on one concept, unchanged since the 1950s: the Pressurized Water Reactor (PWR). Solid fuel heats up liquid water. That is essentially the beginning and end of the issue: liquid water is directly touching the nuclear core. Because water boils at 100*C, and that is not nearly hot enough to generate electricity efficiently, the primary coolant loop must be held at extreme pressure so the water can reach +300*C without boiling. If this pressure is lost, the water will instantly flash to steam and escape the core, usually damaging or destroying it in the process. The now coolant-free nuclear core rapidly heats up, to the point even the ceramic fuel rods can melt down into what’s charmingly known as corium lava. We’ve seen this happen in the Chernobyl and Fukishima disasters and the Three Mile Island accident.

There’s another issue, less catastrophic but just as pressing: current reactors do a really crummy job at releasing the energy in their nuclear fuel. Most reactors “burn” U-235, a specific isotope of uranium that only accounts for 0.07% of all uranium in the world. The remaining 99.3% is U-238 or “depleted" uranium, and that gets tossed or only partially converted into Pu-239, an isotope of plutonium that can also be “burned”. So, yeah — less than 1% of the energy of uranium actually gets used. And then low thermodynamic efficiency of converting the heat released into electricity, due to the relatively low temperature of the heated water, is just insult to injury. If your car had an efficiency of less than 1%, I think you’d throw a fit and junk it.

There’s a better way: the Liquid Fluoride Thorium Reactor (LFTR). The nuclear fuel is dissolved in a carrier salt, like lithium-beryllium fluoride or "FLiBe". When in operation, this salt is already melted, so “meltdown” is now an irrelevant term. This salt does not need to be pressurized — it boils well above 1400*C. No water touches the core. Even the turbines that spin in the generators can be water-free. A liquid-fueled reactor is so much different than a solid-fueled one, and is vastly superior.

And the main fuel of a LFTR, thorium, is 4X more abundant than all the uranium on earth, 400X more abundant than U-235, and 100% of it is converted into useful fuel, unlike natural uranium. And you can dig up thorium anywhere. Thorium converts into U-233 in a LFTR, the second isotope of uranium than can be fissioned, and is not found in nature. In a properly running reactor, the total quantity of U-233 remains the same: Thorium goes in, short-lived fission products come out. That’s the true beauty of the thorium fuel cycle. In regular reactors, nuclear waste from uranium and plutonium remains dangerous for nearly a million years. A LFTR produces less than 2% of the long-lived actinide wastes of regular reactors, and the rest remains dangerous for at most only 300 years. Most of it is safe in only 10 years. While not a trivial length of time, thorium beats the pants off the conventional U-Pu fuel cycle. So little waste is produced that long-term storage costs are no longer insurmountable.

Even better, a LFTR can be configured to consume the long-lived actinide wastes produced by current U-Pu cycle reactors. Our growing stockpiles of spent nuclear fuel can be managed and eliminated.

The primary salt loop in a LFTR holds the fissile U-233 fuel. On contact with a graphite moderator in the core, the U-233 splits and releases heat (graphite-free designs exist, but require more U-233 to “turn on”). The secondary loop holds the thorium. This loop, which blankets the first, captures neutrons released from fission and converts the thorium into more U-233, which is then extracted and sent to the primary salt loop. The third and final salt loop carries no uranium, thorium, or nuclear fuel/products at all — its job is simply to carry the heat to the generators, which can use helium, nitrogen, or carbon dioxide to turn the turbines. The only place water enters the facility is to cool the turbines, and even then they can be air-cooled instead, completely locking out water from the equation.

LFTRs manage to be both fuel-efficient and thermodynamically efficient at the same time. 100% of mined thorium can be converted into U-233 and fissioned. If nickel plumbing is used, salt temperatures up to 750*C can be used, with more expensive molybdenum or carbon-fiber plumbing, up to 1350*C. Thermodynamic efficiency in a heat engine is determined almost entirely by the hottest and coldest parts of the system. For the hottest possible salt, cooled to room temperature by air or water, efficiencies up to 57% can be achieved. Compare that to ~30% for regular reactors that have an operating temperature of only 300-350*C.

Being liquid-fueled, LFTRs have two safety features no solid-fueled reactors can boast. When the salt heats up, it expands and gets less dense, pushing the dissolved fuel out of the core — the reaction rate drops. A “runaway” reaction is virtually impossible, especially with the graphite-free designs. Even then, if the salt does get too hot, a freeze-plug will melt and all the salt in the reactor will drain away into criticality-safe drain tanks, where it will cool and solidify, stopping the reaction in its tracks. Even if all power is lost or there is physical damage to the reactor. No steam explosions, no meltdowns — everything stops.

We can run the world on thorium, and there’s enough to last a thousand years. And when fusion power comes of age, we won’t even need it that long.

It would be a mistake to ignore this technology and wait for fusion. Fossil fuels we rely on today, like coal, do far more damage than just release greenhouse gasses into the air. Sulfur dioxide, nitrogen dioxide, and carbon dioxide fall back to earth as acid rain. Coal-fired power plants release uranium and mercury and other hazardous wastes into the air that you and I breathe (ironically, coal releases more radioactive waste into the environment than actual nuclear reactors do!) and the water we drink. You don't need to believe in anthropological global warming to see how stupid it is to keep releasing billions of tons of pollutants into our air, water, and soil every single year. Contrary to the humorous rhyme, the solution to pollution is **not** dilution.

Thorium reactors are also very resistant to weapon proliferation, despite the fact they breed fissile U-233 out of non-fissile thorium. Due to inevitable and unavoidable side reactions, all the fissile fuel in a LFTR is contaminated with U-232, which is a very powerful gamma-ray emitter, and cannot be separated. No harm is done while inside the reactor, but these gamma rays will fry the sensitive electronics of any nuclear bomb with out very heavy and bulky shielding, as well as any hapless idiot who tried to build one. These gammas are also easily detectable with long-range sensors, so any movement of the fissile fuel will be noticed. Bomb-grade Plutonium-239 can be extracted from our current spent nuclear fuel, and its requires only minimal shielding to handle.

Admittedly, not everything is known about salt reactors, including the LFTR. The technology has been mothballed since the 1970s, despite its success, mostly because these reactors couldn't be used to make nuclear bombs for the government. But interest has seen a resurgence since the early 2000s. Attacking the tech because "It's nuclear, therefore evil" will not help our planet's energy needs. Wind, solar, and hydro power can't scale that far, and fossil fuels will only continue to foul our nest.

We need more energy, not less.

For a much more detailed primer on molten salt reactors and the LFTR, see Liquid Fluoride Thorium Reactor .