5 ms·

I have been doing my best to find critical information on the viability of Thorium based nuclear reactors (because they sound too good to be true). Everyone si

I have been doing my best to find critical information on the viability of Thorium based nuclear reactors (because they sound too good to be true). Everyone sings their praises, but what engineering challenges are there and are those engineering challenges large enough to discourage their development/adoption? The biggest thing I have found is that the salt solution for Thorium reactors is quite corrosive and that is challenging to contain. It generally sounds really promising - even the Wiki page for thorium MSR sings its praises. Why wouldn't it work? Why isn't the world throwing shit-loads of money at this? Is China enlightened or is this some kind of meme-ware technology they fell for (or are trying to convince others to waste their money on)?

NonContro 5y ago
Because corrupt politicians close down existing nuclear power industries and force their countries to import natural gas. They then get cushy roles at those foreign natural gas companies once their political career is over: https://www.theguardian.com/world/2005/dec/13/russia.germany https://www.theguardian.com/world/2005/dec/13/russia.germany And if something goes wrong with Nuclear, they get the blame, whereas climate change cooks the frog slowly and blame and impacts are distributed across the entire planet.
philipkglass 5y ago
Here's a well cited perspective, written by one of HN's own active commenters: https://whatisnuclear.com/thorium-myths.html https://whatisnuclear.com/thorium-myths.html
- godelski 5y ago
  Has anyone seen AcidBurn recently? They've been notably absent for some time. They used to appear in essentially any HN forum with nuclear. I miss their expert insight.
  - acidburnNSA 5y ago
    I'm around. I thought there were just fewer nuclear articles going around! I guess I missed some.
    - godelski 5y ago
      Haha well I've just made a habit of searching for you if there's a nuclear thread. Good to see you around.
- apatheticonion 5y ago
  Thanks for sharing this
  - acidburnNSA 5y ago
    I should add this to the page linked, but another excellent resource to kind of help answer your question is the paper the Oak Ridge National Lab folks put together as they lost funding for the molten salt breeder reactor program in the early 1970s: ORNL-5018 -- Program plan for development of molten-salt breeder reactors[1]. This basically is them saying: "ok folks, we're wrapping up for now but when you inevitably pick up this work, here's what you have in front of you." Though a lot of time has passed since it was written, it's still largely relevant. [1] https://www.osti.gov/biblio/4227904 https://www.osti.gov/biblio/4227904
- TimSchumann 5y ago
  Good write up from a great guy. IIRC the author of that page, Nick Touran, works (worked?) for one of the Nuclear Startups that Gates funded. Met him and had a few drinks once, guy knows his stuff.
- AtlasBarfed 5y ago
  Hm, reading that, it doesn't seem to disprove or actually illuminate that much IMO: Misconception #1: I assume this is listed first because it is the biggest reason Thorium reactors weren't pursued? But really most MSR people seem to view it as political, and the bullet points in "Misconception #1" only underline that. Misconception #2: Almost all MSR presentations seem to assume a fissile "ignition" supply of uranium, that isn't hidden. And it seems to dovetail with the political opposition, since the regulatory agencies will block the supply of fissile uranium to start an MSR with. So this point seems to again highlight artificial/bureaucratic blockades. Miconception #3: Well, ok, this seems to be a decent answer based on the fundamentals of the science and engineering. Misconception #4: This seems to ignore the fact that a very very small amount of uranium is naturally fissile, while the Thorium all breeds to fissile. It also spouts off about seawater extraction, which hasn't happened AFAIK. This answer seems very misleading. Plus, the fact the author is from a competing design (a pebble design I believe, and one of the reasons pebble designs seem to exist is because of the prohibition on research labs from booting up a liquid reactor). I do agree the unknowns are the vessel degradation from the salts, but materials engineers these days are just so amazingly good. It just seems frustrating that the overarching influence of regulatory agency stubbornness and lobbying influence of solid fuel rod reprocessors and other fuel makers (who have a monopoly on nuclear fuel production I believe due to the regulatory agencies) is evident in this article. If it is true that China gets breeder/thorium/liquid reactors going, it all doesn't matter. The US will be a decade behind, and with the anti-nuclear opinions of the US voting populace, that will afford the entrenched interests cover to keep suppressing nuclear. I suppose it doesn't matter right now. Solar/Wind/Battery is improving so quickly you can't forecast/target a price/budget for a reactor design that is invariably 5-10 years out.
  - techdragon 5y ago
    It matters geopolitically speaking in a big way, since any significant improvements to nuclear reactors built by China will have corresponding potential for improvement in their nuclear powered submarines and their future aircraft carriers which are being designed around a similar electric power heavy design philosophy as the US Navy’s Gerald Ford class, with the Chinese Type 004 aircraft carriers being designed as “full size” nuclear powered carriers using electromagnetic catapults to their launch aircraft.
arcticbull 5y ago
Extant CANDU reactors can utilize Thorium fuel too. [1] I believe India is planning to utilize them in this way. [2] [1] https://www.osti.gov/etdeweb/servlets/purl/20823329 https://www.osti.gov/etdeweb/servlets/purl/20823329 [2] https://en.wikipedia.org/wiki/CANDU_reactor https://en.wikipedia.org/wiki/CANDU_reactor
- petre 5y ago
  I think they plan to use the PFBR (Stage II) to produce U-Th MOX and fuel the AHWR with it. However both reactors are far from complete. https://en.wikipedia.org/wiki/India%27s_three-stage_nuclear_power_programme#Advanced_Heavy_Water_Reactor_(AHWR) https://en.wikipedia.org/wiki/India%27s_three-stage_nuclear_...
haecceity 5y ago
Existing energy industry is too entrenched in current technology to innovate? Widely publicized nuclear energy disasters prevents popular support? I don't know but this guy seems pretty smart https://www.youtube.com/watch?v=1EFfxMx6WJs https://www.youtube.com/watch?v=1EFfxMx6WJs
lamontcg 5y ago
> The biggest thing I have found is that the salt solution for Thorium reactors is quite corrosive and that is challenging to contain. If you can figure out the molten salt problem you can replace the nuclear reactor with concentrated solar thermal and get solar baseload power without having to worry about meltdowns for way less than the cost of a nuke plant.
- pfdietz 5y ago
  The salt in MSRs has different requirements from that in solar thermal systems, so there's not really a connection. Also, solar thermal is pretty much a dead technology now; PV (and batteries) killed it.
  - lamontcg 5y ago
    Still way more viable than thorium nuclear reactors.
    - mycall 5y ago
      What about filling the radiation chamber with solar cells that could convert the wave energy into electricity? Something similar to this [0] but scaled way way up. [0] https://www.youtube.com/watch?v=6byi-RFrgtU https://www.youtube.com/watch?v=6byi-RFrgtU
credit_guy 5y ago
Nuclear reactors are complex beasts. Very complex. For example, here's [1] the webpage with NRC's safety evaluation documents for NuScale's small modular reactors. Dozens of documents, totaling more than one thousand pages. In many cases, there are years of work behind a single paragraph. Here's [2] an example where the NRC replies to some concerns raised by some advisory committee regarding some potential scenarios where the reactor may turn unsafe because of some boron technicality: >>4.Operator recovery actions raise the possibility of an influx of deborated water into the core, which may result in recriticality, return to power, and the potential for core damage. Staff Response: In the staff’s SER for Chapter 19, dated July 17, 2020, (ADAMS Accession No. ML20196L734), the staff identified two post-event recovery scenarios that could pose a challenge to reactivity control. The first scenario is recovery from a non-LOCA extended decay heat removal system (DHRS) cooling condition which can occur following initiating events such as general transients and losses of off-site power. The second scenario is recovery from a LOCA ECCS cooling condition which can occur following initiating events such as breaks in the primary coolant lines. The staff notes that either action to inject would likely be governed by plant-specific procedures; however, such procedures are not required at the design certification stage and have not been developed. The staff evaluated the potential core damage risk for the two scenarios. For reasons discussed in the SER which are supported by two papers developed by the Office of Nuclear Regulatory Research (RES) (ADAMS Accession Nos. ML20191A069 and ML20205L317), the staff concludes that enough margin exists such that these recovery scenarios are unlikely to lead to core damage based on the physical effects of fluid mixing, reactivity feedback mechanisms, and associated time constants. Based on the SER and the two RES papers, the staff found that there is reasonable assurance that there are no known significant risk contributors that are unaccounted for and that the identified risk insights are acceptable to support the uses of probabilistic risk assessment (PRA) at the design stage. My point is: there are plenty of corner cases, maybe thousands, and in many of these corner cases the outcome can be either a nuclear boom, or at least a Chernobyl or Fukushima scenario. They are low probability but high danger scenarios, so you need to spend a lot of time (and research money) to either rule out each corner case, or to develop foolproof mitigants. When people say that this or that reactor design is inherently safe, they are talking about first order effects. When the NRC goes into all the details, things always get a bit more complex. Edit: by the way, nuclear fission reactors can be supercritical (all current commercial ones), or subcritical (those need an external source of neutrons or protons, such as an accelerator). Only subcritical reactors [3] can be truly pasively safe. There are concepts of subcritical reactors that use Thorium as a fuel, but that's not what China is trying here. China is trying a classical Thorium reactor, where Thorium is used to breed fissile Uranium (not the classical U-235, but rather the isotopes U-232 and U-233), and that Uranium in turn proceeds to undergo the (supercritical) fission chain reaction. [1] https://www.nrc.gov/docs/ML2002/ML20023A318.html https://www.nrc.gov/docs/ML2002/ML20023A318.html [2] https://www.nrc.gov/docs/ML2023/ML20231A598.pdf https://www.nrc.gov/docs/ML2023/ML20231A598.pdf [3] https://en.wikipedia.org/wiki/Subcritical_reactor https://en.wikipedia.org/wiki/Subcritical_reactor
pfdietz 5y ago
Here's a useful slide deck from ORNL (2017): https://gain.inl.gov/SiteAssets/MoltenSaltReactor/Module2-OverviewofMSRTechnologyandConceptsML17331B114.pdf https://gain.inl.gov/SiteAssets/MoltenSaltReactor/Module2-Ov... Note page 23! Almost all the 137Cs ends up outside of the core, due to sparging of precursors. "Over 40% of [fission products] leave core" Lots of other issues, particularly with radiation damage and corrosion of reactor structural elements. Unlike in a solid fuel reactor, there is fission going on right at the boundary of the salt. In a LWR, there is a layer of water between the fuel and the reactor structure to provide shielding. There will be non-fuel components of a MSR that are not lifetime components, but will have to be swapped out due to degradation. Some MSR designs are proposing to just swap out the entire reactor vessel because of this.

NonContro 5y ago

Because corrupt politicians close down existing nuclear power industries and force their countries to import natural gas. They then get cushy roles at those foreign natural gas companies once their political career is over: https://www.theguardian.com/world/2005/dec/13/russia.germany https://www.theguardian.com/world/2005/dec/13/russia.germany And if something goes wrong with Nuclear, they get the blame, whereas climate change cooks the frog slowly and blame and impacts are distributed across the entire planet.

philipkglass 5y ago

Here's a well cited perspective, written by one of HN's own active commenters: https://whatisnuclear.com/thorium-myths.html https://whatisnuclear.com/thorium-myths.html

godelski 5y ago
Has anyone seen AcidBurn recently? They've been notably absent for some time. They used to appear in essentially any HN forum with nuclear. I miss their expert insight.
- acidburnNSA 5y ago
  I'm around. I thought there were just fewer nuclear articles going around! I guess I missed some.
  - godelski 5y ago
    Haha well I've just made a habit of searching for you if there's a nuclear thread. Good to see you around.
apatheticonion 5y ago
Thanks for sharing this
- acidburnNSA 5y ago
  I should add this to the page linked, but another excellent resource to kind of help answer your question is the paper the Oak Ridge National Lab folks put together as they lost funding for the molten salt breeder reactor program in the early 1970s: ORNL-5018 -- Program plan for development of molten-salt breeder reactors[1]. This basically is them saying: "ok folks, we're wrapping up for now but when you inevitably pick up this work, here's what you have in front of you." Though a lot of time has passed since it was written, it's still largely relevant. [1] https://www.osti.gov/biblio/4227904 https://www.osti.gov/biblio/4227904
TimSchumann 5y ago
Good write up from a great guy. IIRC the author of that page, Nick Touran, works (worked?) for one of the Nuclear Startups that Gates funded. Met him and had a few drinks once, guy knows his stuff.
AtlasBarfed 5y ago
Hm, reading that, it doesn't seem to disprove or actually illuminate that much IMO: Misconception #1: I assume this is listed first because it is the biggest reason Thorium reactors weren't pursued? But really most MSR people seem to view it as political, and the bullet points in "Misconception #1" only underline that. Misconception #2: Almost all MSR presentations seem to assume a fissile "ignition" supply of uranium, that isn't hidden. And it seems to dovetail with the political opposition, since the regulatory agencies will block the supply of fissile uranium to start an MSR with. So this point seems to again highlight artificial/bureaucratic blockades. Miconception #3: Well, ok, this seems to be a decent answer based on the fundamentals of the science and engineering. Misconception #4: This seems to ignore the fact that a very very small amount of uranium is naturally fissile, while the Thorium all breeds to fissile. It also spouts off about seawater extraction, which hasn't happened AFAIK. This answer seems very misleading. Plus, the fact the author is from a competing design (a pebble design I believe, and one of the reasons pebble designs seem to exist is because of the prohibition on research labs from booting up a liquid reactor). I do agree the unknowns are the vessel degradation from the salts, but materials engineers these days are just so amazingly good. It just seems frustrating that the overarching influence of regulatory agency stubbornness and lobbying influence of solid fuel rod reprocessors and other fuel makers (who have a monopoly on nuclear fuel production I believe due to the regulatory agencies) is evident in this article. If it is true that China gets breeder/thorium/liquid reactors going, it all doesn't matter. The US will be a decade behind, and with the anti-nuclear opinions of the US voting populace, that will afford the entrenched interests cover to keep suppressing nuclear. I suppose it doesn't matter right now. Solar/Wind/Battery is improving so quickly you can't forecast/target a price/budget for a reactor design that is invariably 5-10 years out.
- techdragon 5y ago
  It matters geopolitically speaking in a big way, since any significant improvements to nuclear reactors built by China will have corresponding potential for improvement in their nuclear powered submarines and their future aircraft carriers which are being designed around a similar electric power heavy design philosophy as the US Navy’s Gerald Ford class, with the Chinese Type 004 aircraft carriers being designed as “full size” nuclear powered carriers using electromagnetic catapults to their launch aircraft.

arcticbull 5y ago

Extant CANDU reactors can utilize Thorium fuel too. [1] I believe India is planning to utilize them in this way. [2] [1] https://www.osti.gov/etdeweb/servlets/purl/20823329 https://www.osti.gov/etdeweb/servlets/purl/20823329 [2] https://en.wikipedia.org/wiki/CANDU_reactor https://en.wikipedia.org/wiki/CANDU_reactor

petre 5y ago
I think they plan to use the PFBR (Stage II) to produce U-Th MOX and fuel the AHWR with it. However both reactors are far from complete. https://en.wikipedia.org/wiki/India%27s_three-stage_nuclear_power_programme#Advanced_Heavy_Water_Reactor_(AHWR) https://en.wikipedia.org/wiki/India%27s_three-stage_nuclear_...

haecceity 5y ago

Existing energy industry is too entrenched in current technology to innovate? Widely publicized nuclear energy disasters prevents popular support? I don't know but this guy seems pretty smart https://www.youtube.com/watch?v=1EFfxMx6WJs https://www.youtube.com/watch?v=1EFfxMx6WJs

lamontcg 5y ago

> The biggest thing I have found is that the salt solution for Thorium reactors is quite corrosive and that is challenging to contain. If you can figure out the molten salt problem you can replace the nuclear reactor with concentrated solar thermal and get solar baseload power without having to worry about meltdowns for way less than the cost of a nuke plant.

pfdietz 5y ago
The salt in MSRs has different requirements from that in solar thermal systems, so there's not really a connection. Also, solar thermal is pretty much a dead technology now; PV (and batteries) killed it.
- lamontcg 5y ago
  Still way more viable than thorium nuclear reactors.
  - mycall 5y ago
    What about filling the radiation chamber with solar cells that could convert the wave energy into electricity? Something similar to this [0] but scaled way way up. [0] https://www.youtube.com/watch?v=6byi-RFrgtU https://www.youtube.com/watch?v=6byi-RFrgtU

credit_guy 5y ago

Nuclear reactors are complex beasts. Very complex. For example, here's [1] the webpage with NRC's safety evaluation documents for NuScale's small modular reactors. Dozens of documents, totaling more than one thousand pages. In many cases, there are years of work behind a single paragraph. Here's [2] an example where the NRC replies to some concerns raised by some advisory committee regarding some potential scenarios where the reactor may turn unsafe because of some boron technicality: >>4.Operator recovery actions raise the possibility of an influx of deborated water into the core, which may result in recriticality, return to power, and the potential for core damage. Staff Response: In the staff’s SER for Chapter 19, dated July 17, 2020, (ADAMS Accession No. ML20196L734), the staff identified two post-event recovery scenarios that could pose a challenge to reactivity control. The first scenario is recovery from a non-LOCA extended decay heat removal system (DHRS) cooling condition which can occur following initiating events such as general transients and losses of off-site power. The second scenario is recovery from a LOCA ECCS cooling condition which can occur following initiating events such as breaks in the primary coolant lines. The staff notes that either action to inject would likely be governed by plant-specific procedures; however, such procedures are not required at the design certification stage and have not been developed. The staff evaluated the potential core damage risk for the two scenarios. For reasons discussed in the SER which are supported by two papers developed by the Office of Nuclear Regulatory Research (RES) (ADAMS Accession Nos. ML20191A069 and ML20205L317), the staff concludes that enough margin exists such that these recovery scenarios are unlikely to lead to core damage based on the physical effects of fluid mixing, reactivity feedback mechanisms, and associated time constants. Based on the SER and the two RES papers, the staff found that there is reasonable assurance that there are no known significant risk contributors that are unaccounted for and that the identified risk insights are acceptable to support the uses of probabilistic risk assessment (PRA) at the design stage. My point is: there are plenty of corner cases, maybe thousands, and in many of these corner cases the outcome can be either a nuclear boom, or at least a Chernobyl or Fukushima scenario. They are low probability but high danger scenarios, so you need to spend a lot of time (and research money) to either rule out each corner case, or to develop foolproof mitigants. When people say that this or that reactor design is inherently safe, they are talking about first order effects. When the NRC goes into all the details, things always get a bit more complex. Edit: by the way, nuclear fission reactors can be supercritical (all current commercial ones), or subcritical (those need an external source of neutrons or protons, such as an accelerator). Only subcritical reactors [3] can be truly pasively safe. There are concepts of subcritical reactors that use Thorium as a fuel, but that's not what China is trying here. China is trying a classical Thorium reactor, where Thorium is used to breed fissile Uranium (not the classical U-235, but rather the isotopes U-232 and U-233), and that Uranium in turn proceeds to undergo the (supercritical) fission chain reaction. [1] https://www.nrc.gov/docs/ML2002/ML20023A318.html https://www.nrc.gov/docs/ML2002/ML20023A318.html [2] https://www.nrc.gov/docs/ML2023/ML20231A598.pdf https://www.nrc.gov/docs/ML2023/ML20231A598.pdf [3] https://en.wikipedia.org/wiki/Subcritical_reactor https://en.wikipedia.org/wiki/Subcritical_reactor

pfdietz 5y ago

Here's a useful slide deck from ORNL (2017): https://gain.inl.gov/SiteAssets/MoltenSaltReactor/Module2-OverviewofMSRTechnologyandConceptsML17331B114.pdf https://gain.inl.gov/SiteAssets/MoltenSaltReactor/Module2-Ov... Note page 23! Almost all the 137Cs ends up outside of the core, due to sparging of precursors. "Over 40% of [fission products] leave core" Lots of other issues, particularly with radiation damage and corrosion of reactor structural elements. Unlike in a solid fuel reactor, there is fission going on right at the boundary of the salt. In a LWR, there is a layer of water between the fuel and the reactor structure to provide shielding. There will be non-fuel components of a MSR that are not lifetime components, but will have to be swapped out due to degradation. Some MSR designs are proposing to just swap out the entire reactor vessel because of this.