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Does anyone know how much less waste Thorium produces when used compared to Uranium? Both this article and Peter Thiel's linked article say "less", but neither

by Permit 14y ago

Does anyone know how much less waste Thorium produces when used compared to Uranium? Both this article and Peter Thiel's linked article say "less", but neither are exact.

pkrein 14y ago
It's actually a bit hard to quantify. The true cost of radioactive waste is related to what type of radiation it emits (gamma? alpha particles?), how long-lived the radiation is i.e. it's half-life, and the actual quantity of that material that is produced per Watt. This triple-axis makes it a bit hard to quantify in simple terms, but the main idea behind thorium is that the waste has a significantly shorter half-life[1]. Depending on the exact reactor design, there may also be ways to reduce the quantity of secondary waste (like water that's been exposed to heavy neutron flux while transferring energy from nuclear core --> steam turbines). [1] : http://www.forbes.com/sites/williampentland/2011/09/11/is-thorium-the-biggest-energy-breakthrough-since-fire-possibly/ http://www.forbes.com/sites/williampentland/2011/09/11/is-th...
- ScotterC 14y ago
  The best way to think of it is since U-233 is so much easier to burn then U-235 is like tinder instead of lumber. It reduces to much less and burns thoroughly.
- WiseWeasel 14y ago
  There's also the huge difference between solid fuel rods used in uranium-fueled nuclear reactors and the liquid fuel used in molten salt thorium reactors. Solid fuel rods break down beyond use after less than one percent of the fissile material has been consumed, at which point the entire reactor must be shut down and the fuel rods replaced. With molten salt reactors, the fuel is constantly being replenished and the waste removed during operation, allowing a much larger portion of the fissile material (up to 99%) to be consumed before being treated as waste. http://en.wikipedia.org/wiki/Liquid_fluoride_thorium_reactor#Economy_and_efficiency http://en.wikipedia.org/wiki/Liquid_fluoride_thorium_reactor...
- g8oz 14y ago
  Offtopic: how did you get a .pk domain?
  - umairsiddique 14y ago
    http://www.pknic.net.pk http://www.pknic.net.pk
JohnRandall 14y ago
There is a misconception about the waste from current reactors. In short, the waste is not waste (as in something useless to be discarded, disposed of). This is all explained in the long video linked in my first post so I'll not repeat it. So much so that two MIT students (and their Professors) have come up with the acronym WAMSR, Waste Annihilating MSR, http://web.mit.edu/nse/inaround/dewan-massie.html http://web.mit.edu/nse/inaround/dewan-massie.html and started a company. http://transatomicpower.com/products.php http://transatomicpower.com/products.php The LFTR itself can also burn the waste from a conventional reactor. http://en.wikipedia.org/wiki/Liquid_fluoride_thorium_reactor http://en.wikipedia.org/wiki/Liquid_fluoride_thorium_reactor (the item "Destruction of existing long lived nuclear wastes" in the "Advantages" section) This infographic is a nice compact presentation http://imgur.com/pm4Ux http://imgur.com/pm4Ux
Gravityloss 14y ago
You have to understand a bit about the subject. 1. Current reactors have U-238 and U-235. U-238 turns into Plutonium and some of that fissions but some is turned into heavier long lived transuranics. U-235 is very rare so we can't run just on that: this is what is enriched with centrifuges (no chemical separation possible as it's chemically similar to U-238) and what people mean when they say we will run out of uranium. Most of spent nuclear fuel is still just U-238. Maybe one could simplify and say that the spent fuel is not "used up" : instead it is "poisoned". 2. Thorium reactors have Th-232 and U-233. Simplified, the Th-232 turns into U-233 when it absorbs a neutron. U-233 fissions very well and releases more than two neutrons when it captures a neutron. There's quite many steps up to transuranics from that where fission can still happen, so you get very little transuranics. 3. There is the "breeder reactor" that would use just U-238 by making plutonium out of that. But you need fast spectrum and it's hard to control. It would have plenty of fuel though since there's lots of U-238. 4. What's more significant is that since U-233 is so good, you only need very little. AND you can use thermal spectrum making control easy. The thorium system is very clever in so many ways but it only works well if you design the whole reactor concept understanding what you have - neutronics and chemistry. It's not very complex at all, just read up on it, the basics can be understood in a couple of hours. Then you understand why it produces less waste, consumes less fuel, why putting thorium rods to solid fuel reactors doesn't make sense (protactinium) etc etc...
KitemanSA 14y ago
The answer, when compared to typical light water reactors is... A hell of a lot less. First, since Thorium is a byproduct of Rare Earth Element mining and Uranium is mined specifically, there is all the mining waste that is saved. Second, since Thorium is used up ~completely and Uranium is used only about 0.5%, you need about 200 times more raw Uranium metal than Thorium meaning even MORE mining waste. Third, all the extra metal is RadioActive Waste. Fourth, in making the solid fuel elements, various reactants etc. become even more RAW. Fifth, the pellets are clad, then assembled into bundles using metal that gets irradiated and becomes ever more RAW. Sixth, the vast majority of the fuel pellet is U238 which gets irradiated and some becomes transUranic elements, significantly more than in a LFTR. only then do the two become ALMOST equivalent in the amount of fission products made, though even there the LFTR can be substantially more efficient at turning heat into electricity, so less fuel needs to be converted. Oh, and most fission products decay to stability in hours, some take years, a few take a few hundred years and the rest are transmutable. It is the TRUs that represent the big storage problem. But guess what, LFTRs can burn them up too. Not only do LFTRs not generate significant amounts of "wastes" but they can burn the problem waste from PWRs. How cool is that?!!!

by Permit 14y ago

Does anyone know how much less waste Thorium produces when used compared to Uranium? Both this article and Peter Thiel's linked article say "less", but neither are exact.

pkrein 14y ago

It's actually a bit hard to quantify. The true cost of radioactive waste is related to what type of radiation it emits (gamma? alpha particles?), how long-lived the radiation is i.e. it's half-life, and the actual quantity of that material that is produced per Watt. This triple-axis makes it a bit hard to quantify in simple terms, but the main idea behind thorium is that the waste has a significantly shorter half-life[1]. Depending on the exact reactor design, there may also be ways to reduce the quantity of secondary waste (like water that's been exposed to heavy neutron flux while transferring energy from nuclear core --> steam turbines). [1] : http://www.forbes.com/sites/williampentland/2011/09/11/is-thorium-the-biggest-energy-breakthrough-since-fire-possibly/ http://www.forbes.com/sites/williampentland/2011/09/11/is-th...

ScotterC 14y ago
The best way to think of it is since U-233 is so much easier to burn then U-235 is like tinder instead of lumber. It reduces to much less and burns thoroughly.
WiseWeasel 14y ago
There's also the huge difference between solid fuel rods used in uranium-fueled nuclear reactors and the liquid fuel used in molten salt thorium reactors. Solid fuel rods break down beyond use after less than one percent of the fissile material has been consumed, at which point the entire reactor must be shut down and the fuel rods replaced. With molten salt reactors, the fuel is constantly being replenished and the waste removed during operation, allowing a much larger portion of the fissile material (up to 99%) to be consumed before being treated as waste. http://en.wikipedia.org/wiki/Liquid_fluoride_thorium_reactor#Economy_and_efficiency http://en.wikipedia.org/wiki/Liquid_fluoride_thorium_reactor...
g8oz 14y ago
Offtopic: how did you get a .pk domain?
- umairsiddique 14y ago
  http://www.pknic.net.pk http://www.pknic.net.pk

JohnRandall 14y ago

There is a misconception about the waste from current reactors. In short, the waste is not waste (as in something useless to be discarded, disposed of). This is all explained in the long video linked in my first post so I'll not repeat it. So much so that two MIT students (and their Professors) have come up with the acronym WAMSR, Waste Annihilating MSR, http://web.mit.edu/nse/inaround/dewan-massie.html http://web.mit.edu/nse/inaround/dewan-massie.html and started a company. http://transatomicpower.com/products.php http://transatomicpower.com/products.php The LFTR itself can also burn the waste from a conventional reactor. http://en.wikipedia.org/wiki/Liquid_fluoride_thorium_reactor http://en.wikipedia.org/wiki/Liquid_fluoride_thorium_reactor (the item "Destruction of existing long lived nuclear wastes" in the "Advantages" section) This infographic is a nice compact presentation http://imgur.com/pm4Ux http://imgur.com/pm4Ux

Gravityloss 14y ago

You have to understand a bit about the subject. 1. Current reactors have U-238 and U-235. U-238 turns into Plutonium and some of that fissions but some is turned into heavier long lived transuranics. U-235 is very rare so we can't run just on that: this is what is enriched with centrifuges (no chemical separation possible as it's chemically similar to U-238) and what people mean when they say we will run out of uranium. Most of spent nuclear fuel is still just U-238. Maybe one could simplify and say that the spent fuel is not "used up" : instead it is "poisoned". 2. Thorium reactors have Th-232 and U-233. Simplified, the Th-232 turns into U-233 when it absorbs a neutron. U-233 fissions very well and releases more than two neutrons when it captures a neutron. There's quite many steps up to transuranics from that where fission can still happen, so you get very little transuranics. 3. There is the "breeder reactor" that would use just U-238 by making plutonium out of that. But you need fast spectrum and it's hard to control. It would have plenty of fuel though since there's lots of U-238. 4. What's more significant is that since U-233 is so good, you only need very little. AND you can use thermal spectrum making control easy. The thorium system is very clever in so many ways but it only works well if you design the whole reactor concept understanding what you have - neutronics and chemistry. It's not very complex at all, just read up on it, the basics can be understood in a couple of hours. Then you understand why it produces less waste, consumes less fuel, why putting thorium rods to solid fuel reactors doesn't make sense (protactinium) etc etc...

KitemanSA 14y ago

The answer, when compared to typical light water reactors is... A hell of a lot less. First, since Thorium is a byproduct of Rare Earth Element mining and Uranium is mined specifically, there is all the mining waste that is saved. Second, since Thorium is used up ~completely and Uranium is used only about 0.5%, you need about 200 times more raw Uranium metal than Thorium meaning even MORE mining waste. Third, all the extra metal is RadioActive Waste. Fourth, in making the solid fuel elements, various reactants etc. become even more RAW. Fifth, the pellets are clad, then assembled into bundles using metal that gets irradiated and becomes ever more RAW. Sixth, the vast majority of the fuel pellet is U238 which gets irradiated and some becomes transUranic elements, significantly more than in a LFTR. only then do the two become ALMOST equivalent in the amount of fission products made, though even there the LFTR can be substantially more efficient at turning heat into electricity, so less fuel needs to be converted. Oh, and most fission products decay to stability in hours, some take years, a few take a few hundred years and the rest are transmutable. It is the TRUs that represent the big storage problem. But guess what, LFTRs can burn them up too. Not only do LFTRs not generate significant amounts of "wastes" but they can burn the problem waste from PWRs. How cool is that?!!!