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Thorium Molten Salt Reactor uses thorium salt.


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Just watched https://www.youtube.com/watch?v=1EFfxMx6WJs

It blew my mind, I always thought an molten salt reactor used molten salt as coolant rater than water letting it run at higher temperatures. 
However this reactor uses thorium salt as both fuel and heat transfer medium. 
Make me think of nuclear salt water rocket engines who used salt as fuel but at an insane scale, here its just chain reacting in the reactor chamber. 
As its an liquid its easier to handle thermal issues. To shut it down in an emergency you just drain it down into multiple tanks, yes they need to survive the heat but that should be manageable. 
No high pressure steam and risk of hydrogen buildup, yes you need steam on the other end of the heat exchanger but that is just standard steam plant. 

See some downsides, first is that the salt is radioactive and corrosive and you need to pump it around and through an heat exchanger. Second is that if you cool it down you need to melt it again. 
You probably want to drain it into storage tanks for this as they are easier to heat up than pipes and pumps. 
You probably need to constantly clean the molten salt to remove transmuted elements who could might solidify in pipes.

 

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Removing the transmuted elements is actually a feature of thorium reactors. They are self-enriching as a result which means that you fully utilize the thorium instead of leaving it as unprocessed waste (uranium rods actually still have a lot of viable fuel left when they are taken out of service, but no one wants to re-enrich them to a usable rod).

They are also passively safe because they can make it so if it gets too hot it melts a plug and drains into storage tanks where it will shut down without the moderator.

For a deeper dive I highly recommend the Illinois Energy Prof's video:

 

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15 minutes ago, satnet said:

Removing the transmuted elements is actually a feature of thorium reactors. They are self-enriching as a result which means that you fully utilize the thorium instead of leaving it as unprocessed waste (uranium rods actually still have a

For a deeper dive I highly recommend the Illinois Energy Prof's video:

Note: "shorter lived waste products" also means "nastier and higher radioactivity" without further description, but I'll admit that the "ultra long lived waste" problem of fission is mostly a still strong myth (yes, it lives long.  But long lived isotopes tend not to be radioactive.  Glassify it and store it somewhere in an old mine and don't worry about it.

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2 hours ago, wumpus said:

Note: "shorter lived waste products" also means "nastier and higher radioactivity"

It's not quite that simple. The shorter half-life means you get more decay events in the same concentration, but short half-life products also don't accumulate as much, because shorter half-life, so you don't usually get the same concentrations as the longer lived stuff. Not to mention that the kind of radiation matters. In waste, gamma and alpha might be nasty for handling the waste, but they aren't going to poison ground water, dust, or what might have you. Basically, neutron radiation is the only one you really have to be paranoid about long term, and the energy of the neutrons matters a lot. Particularly slow neutrons will just bounce around and decay to trace amounts of hydrogen gas. Very high energy neutrons tend to either not interact or convert whatever they hit into something very unstable, causing immediate collapse, and generally, safer products. But if you hit the energy sweet spot for a particular nucleus that a neutron might encounter, something entirely harmless might become radioactive with long enough half-life to get out there and cause harm, and that's the kind of radiation you really have to watch out for with radioactive waste. Radiation that makes other things radioactive. And some isotopes are a lot worse for that than others and it has nothing to do with their half-life.

Now, reactors were never my jam, so I can't tell you off the top of my head how the waste is going to compare. There are complex decay chains for different isotopes of Uranium and Thorium all resulting in all kinds of candidates for bad neutrons, and it would take me entirely too long going through isotope table to sort it out. I'm sure people have done this work and there are probably some summaries out there on how the wastes of Uranium and Thorium reactors compares. The only point I'm trying to make here is that it's not as simple as "short-lived, therefore, nasty."

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I think this is the best possible design, the Liquid Fluoride Thorium Reactor (LFTR), a type of Molten Salt Reactor:

https://en.wikipedia.org/wiki/Liquid_fluoride_thorium_reactor

There's a lot of features in there.  This is still a nuclear power plant with dangerous chemicals (often including Beryllium, which is always dangerous), but not more than existing reactors or chemical plants--all of which our technical society depends upon having.  And it has a lot of good features.

  1. Thorium is the nuclear material.  Currently with all the demand for Rare Earth Elements, Thorium ores are a byproduct waste that needs to be stored.  There's already a lot of Thorium ore available right now.
  2. LFTR is a high-temperature reactor with moderate pressures to pump molten salts.  It does not have mass use of high pressure water or steam either radioactive or clean.  The current large-volume reactor containment buildings are to provide worse-case steam expansion space in case a huge high-pressure manifold cracks off--which can happen in hot-water or steam plants.  LFTR would only require a smaller more-compact containment building.
  3. The design of LFTR is to convert Th-232 salts into U-233 salts, where the U-233 is the fissile isotope.  Some creation of U-232 makes the salt unsuitable for nuclear weapons without separation of the U-233 from the U-232 (as well as the rest of the mix), which is hard.
  4. The operation of LFTR removes fission products by chemical processing on the fissile salt loop.  This is designed to remove short half-life and very-long half-life isotopes, leaving the more dangerous medium half-life isotopes in the loop for further transmutation into other isotopes.
    1. Short half-life fission products decay very quickly in a few years or less to low levels of radioactivity, comparable to the original Thorium ores.
    2. Very-log half-life products are already at low levels of radioactivity, comparable to the original Thorium ores.
    3. The dangerous waste products are those with medium half-lives (think Radium), a few 1,000 to a few 10,000 years, which are highly radioactive for a long time.  They stay in the fissile salt loop to be transmutated by further radiation.
    4. The input of new Th-232 and U-233 into the salts, power levels, and extraction of the wastes noted in #4.1 and #4.2 is designed to keep the molten salt in a state where operation can continue, for power production and the continued transmutation of the wastes noted in #4.3.
  5. LFTR is designed (like some current reactors, like CANDU) to run continuously receiving replacement fuel (Thorium and salts) and extracting appropriate waste products as detailed in point 4.  There is no need to shutdown for refuelling, only major maintenance or emergencies.
  6. LFTR is designed to shutdown gracefully and go from operation to cold shutdown or emergency cold shutdown without any needed external power or cooling.  The salt loops have a cold salt plug in a low point that is maintained by cooling.  Removing the power from this cooling has the plug melt and the liquid salt drain into tanks designed to passively allow the fuel to cool off.
  7. The Nuclear Industry is still the only industry that truly handles all its waste products and that volume of waste, as well as the rest of the technology's impact, is minimal compared to other power technologies, including current solar and wind.  Burning coal can't run under the same regulations as the Nuclear Industry because it gets a pass for all the "natural" radioactive material from the coal going up the smokestack.  (The only source of radioactive pollution that comes close to that from burning coal is Radon leaking from the soil in some places.)
Edited by Jacke
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11 hours ago, wumpus said:

Glassify it

Instructions unclear, all of Europe crying foul.

https://www.sciencealert.com/here-s-what-you-need-to-know-mysterious-radiation-cloud-over-europe-russia-ruthenium

11 hours ago, satnet said:

For a deeper dive I highly recommend

...anything that's not a video about a thorium-lowered car. Had to recently deal with someone who bought the hype. Ugh.

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6 hours ago, Jacke said:

I think this is the best possible design, the Liquid Fluoride Thorium Reactor (LFTR), a type of Molten Salt Reactor:

https://en.wikipedia.org/wiki/Liquid_fluoride_thorium_reactor

There's a lot of features in there.  This is still a nuclear power plant with dangerous chemicals (often including Beryllium, which is always dangerous), but not more than existing reactors or chemical plants--all of which our technical society depends upon having.  And it has a lot of good features.

  1. Thorium is the nuclear material.  Currently with all the demand for Rare Earth Elements, Thorium ores are a byproduct waste that needs to be stored.  There's already a lot of Thorium ore available right now.
  2. LFTR is a high-temperature reactor with moderate pressures to pump molten salts.  It does not have mass use of high pressure water or steam either radioactive or clean.  The current large-volume reactor containment buildings are to provide worse-case steam expansion space in case a huge high-pressure manifold cracks off--which can happen in hot-water or steam plants.  LFTR would only require a smaller more-compact containment building.
  3. The design of LFTR is to convert Th-232 salts into U-233 salts, where the U-233 is the fissile isotope.  Some creation of U-232 makes the salt unsuitable for nuclear weapons without separation of the U-233 from the U-232 (as well as the rest of the mix), which is hard.
  4. The operation of LFTR removes fission products by chemical processing on the fissile salt loop.  This is designed to remove short half-life and very-long half-life isotopes, leaving the more dangerous medium half-life isotopes in the loop for further transmutation into other isotopes.
    1. Short half-life fission products decay very quickly in a few years or less to low levels of radioactivity, comparable to the original Thorium ores.
    2. Very-log half-life products are already at low levels of radioactivity, comparable to the original Thorium ores.
    3. The dangerous waste products are those with medium half-lives (think Radium), a few 1,000 to a few 10,000 years, which are highly radioactive for a long time.  They stay in the fissile salt loop to be transmutated by further radiation.
    4. The input of new Th-232 and U-233 into the salts, power levels, and extraction of the wastes noted in #4.1 and #4.2 is designed to keep the molten salt in a state where operation can continue, for power production and the continued transmutation of the wastes noted in #4.3.
  5. LFTR is designed (like some current reactors, like CANDU) to run continuously receiving replacement fuel (Thorium and salts) and extracting appropriate waste products as detailed in point 4.  There is no need to shutdown for refuelling, only major maintenance or emergencies.
  6. LFTR is designed to shutdown gracefully and go from operation to cold shutdown or emergency cold shutdown without any needed external power or cooling.  The salt loops have a cold salt plug in a low point that is maintained by cooling.  Removing the power from this cooling has the plug melt and the liquid salt drain into tanks designed to passively allow the fuel to cool off.
  7. The Nuclear Industry is still the only industry that truly handles all its waste products and that volume of waste, as well as the rest of the technology's impact, is minimal compared to other power technologies, including current solar and wind.  Burning coal can't run under the same regulations as the Nuclear Industry because it gets a pass for all the "natural" radioactive material from the coal going up the smokestack.  (The only source of radioactive pollution that comes close to that from burning coal is Radon leaking from the soil in some places.)

Any time I see "flouride" I think there may be some issues involving just regular old chemical reactions.

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1 hour ago, mikegarrison said:

Any time I see "flouride" I think there may be some issues involving just regular old chemical reactions.

Molten Fluoride salts are hazardous but no more than many other chemicals and processes used in plants in every city and many towns around the world.  It has to be handled properly.

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I've often wondered about thorium reactors, because it all sounded fairly good, really. Almost to good to be true, actually. Is it all overblown? I don't really know. But the wariness around anything nuclear and the cost of new megaprojects makes it hard to gain traction. Although I seem to recall CANDU reactors (or maybe something else) could use thorium-based fuel rods, but I believe they're mostly fairly old by now

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18 minutes ago, StrandedonEarth said:

I've often wondered about thorium reactors, because it all sounded fairly good, really. Almost to good to be true, actually. Is it all overblown? I don't really know. But the wariness around anything nuclear and the cost of new megaprojects makes it hard to gain traction. Although I seem to recall CANDU reactors (or maybe something else) could use thorium-based fuel rods, but I believe they're mostly fairly old by now

It's a case of sunk cost and a small number of reactors.  Enriched high-pressure reactors were influenced by the US Navy's designs for ships and submarines.  Some variants, especially outside the United States, but only a few that were really different, like the CANDU which with heavy water could run on unenriched Uranium.

Now with growing world power needs and a requirement for low Carbon, there's a market for such power plants of all sizes.  So all the research on better reactor designs, including LFTR and especially smaller designs, now have an opportunity for implementation.  And that's taking place now.

A major benefit with Thorium is a lot of ores is already mined and it's a lot cheaper than Uranium.  The extra issue with Thorium is it needs a slow breeder design to create the needed U-233, then that U-233 needs to be put in a place where it can be used for power.  A modified conventional reactor can  do this, but to get the U-233 usable for power, it needs reprocessing.  The whole point about LFTR designs is that it's made to do both and make the whole process flow more smoothly.

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On 8/3/2021 at 2:56 AM, StrandedonEarth said:

I've often wondered about thorium reactors, because it all sounded fairly good, really. Almost to good to be true, actually. Is it all overblown?

Just use of thorium, everything else being equal? Definitely overblown. It's just a useful uranium substitute. It's not an anti-proliferation silver bullet - you can build nukes out of U-233 and if you can enrich uranium to weapons-grade in the first place, the high-rad impurities in U-233 fuel aren't going to stop you.

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