This doesn't jive with my current understand of proposed designs for LFTRs, which include passive safety and basically guarantee there can be no catastrophic meltdown event. This article seems to...
When it comes to new reactors, although some next-generation designs offer potential safety benefits relative to current reactors, they could be operated in either thorium-uranium or uranium-plutonium fuel cycles. Consequently, the benefits are a function of the inherent safety in the next-generation designs, not the utilization of thorium.
This doesn't jive with my current understand of proposed designs for LFTRs, which include passive safety and basically guarantee there can be no catastrophic meltdown event. This article seems to be using very precise language to 'fact-check' and then summarizing or paraphrasing to support its own facts, which is a weird pattern.
The short version is the author of the article doesn't understand nuclear decay chains. Thorium and Uranium have very different chains, and the Thorium chain is vastly superior in every way,...
The short version is the author of the article doesn't understand nuclear decay chains. Thorium and Uranium have very different chains, and the Thorium chain is vastly superior in every way, producing much (relatively) safer byproducts. Only an idiot or a madman would run these reactors on Uranium unless they are trying to burn up old Uranium waste from existing reactors.
Existing Plutonium is wonderful if you can get it, since it'll jump-start Thorium reactors. They do need seed fuel until the Thorium reaction becomes self-sustaining and produces its own fuel. Great way to get rid of decommissioned warhead material.
You are right about the core design, though. Molten salts are a way to perform nuclear chemistry safely, and the safety systems will work just fine to that end no matter the fuel.
and building a power plant with a thorium reactor is no cheaper than building a power plant with a uranium reactor.
This is just pure bullshit and coming from a professor no less, that's disappointing. Since you can throw out the entire pressurized water bullshit, the cost of a plant craters until it fits in a shipping container and can be made on an assembly line. This article is a hit piece, not real science.
When you ask existing nuclear engineers these questions, they answer from the existing body of knowledge and are universally uninformed on this topic. This is not surprising since until about five years ago, nothing at all about thorium or molten salt was taught to people completing a PhD track in nuclear engineering. They just don't know the science because it's not part of our university system. In fact the only thing they have in common is graphite moderators to slow down the neutrons. It's like comparing a car to a jet because they both have wheels.
The whole point of thorium molten salt is to dispose of the paradigm these folks have lived with and worked on for decades. It's not surprising, but it is illustrative of the uphill battle thorium has had to fight against the existing industry just to be taken seriously.
I'll keep linking the same answer I give in every thorium thread. Expert information presented by the most knowledgeable person in the field. You might also enjoy the ridiculous number of...
I don't know if the specific information you're interested in is covered in them, but I saw these linked to elsewhere and they seem good (and are written by a reactor physicist with a Ph.D. in...
I don't know if the specific information you're interested in is covered in them, but I saw these linked to elsewhere and they seem good (and are written by a reactor physicist with a Ph.D. in nuclear engineering):
I'm basically one of those people who now derails threads by recommending Tildes-centric ideas, so I'll jump in here on a complete tangent: There are certainly threads where I feel like dedicated...
I'm basically one of those people who now derails threads by recommending Tildes-centric ideas, so I'll jump in here on a complete tangent:
There are certainly threads where I feel like dedicated first party support—i.e. from Tildes—for citations attached to a comment, would be a monumental help in establishing credibility and quality discussion. Even if it was a simple list of displayed sources with enriched metadata, it doesn't have to be perfect on first attempt.
Obviously, this is not something needed for every thread, but having the ability to turn on, or enable citation support in some specific threads would be helpful. It's clear that internet discourse is broken, and I don't know if Deimos has publicly commented on whether it's the goal for Tildes to attempt to fix that (probably not), but this would be a positive step, IMO.
Tildes, functionally, should be more than just a Reddit clone.
If someone wants to add citations to a comment, I feel like they can already do it easily by just adding links, either at the relevant places in the comment or just at the bottom. What would a...
If someone wants to add citations to a comment, I feel like they can already do it easily by just adding links, either at the relevant places in the comment or just at the bottom. What would a dedicated feature do differently or better?
@cfabbro too, if there's something specific you were thinking of.
I was thinking more along the lines of potentially being able to add citations to other people's comments and to threads/topics, but I don't know if that's what @emdash was specifically referring...
I was thinking more along the lines of potentially being able to add citations to other people's comments and to threads/topics, but I don't know if that's what @emdash was specifically referring to.
I also think having an official citation system would encourage people to actually cite their sources more often, which could help improve the level of discourse here. I don't think it's a game changer, or strictly necessary in every thread/topic (which is why the toggle is a good idea, IMO), but I think it could be an improvement over just relying on markdown, especially in certain, more formal, academically minded groups (e.g. ~science, ~humanities) and topics/threads.
Another potential benefit to it could be the ability to automatically scrape some metadata on the source and include that in the citation. And another could also be formatting related; An official system could support a more formal structure to citations, like those used in bibliographies or on wikis, rather than just your standard hyperlinks on chunks of text within the comment.
Adding citations to other comments is also a good idea, IMO. But for me, @Deimos, it's the encouragement and explicit support that such a feature would provide that is the primary selling point....
Adding citations to other comments is also a good idea, IMO. But for me, @Deimos, it's the encouragement and explicit support that such a feature would provide that is the primary selling point. If you promote a feature, people will use it, and be aware of it as a general thing as part of the community. It makes it a first class citizen of Tildes and raises the bar of expected quality when a citable thread is created.
As I said, it doesn't have to be some stodgy "you must format your citations in this format, and provide exact references for each claim you make", but some kind of freeform community-based citation gathering tool that can attach to comments seems like a novel and interesting idea that might be worth exploring?
It looks like there's actually a footnotes extension already included in GitHub's commonmark that just needs to be enabled (and isn't currently for Tildes). It's not included in the spec and there...
It looks like there's actually a footnotes extension already included in GitHub's commonmark that just needs to be enabled (and isn't currently for Tildes).
It's not included in the spec and there doesn't really seem to be any formal documentation, but it looks like it probably works close to how other markdown footnotes do. There's a little section in their testing file here that shows how you can write some footnotes and the output it expects: https://github.com/github/cmark-gfm/blob/master/test/extensions.txt#L645
So yeah, it looks like I should just be able to enable that (and I don't really see any reason not to).
Oooh, I really like that idea. Added to Gitlab: https://gitlab.com/tildes/tildes/issues/618
There are certainly threads where I feel like dedicated first party support—i.e. from Tildes—for citations attached to a comment, would be a monumental help in establishing credibility and quality discussion.
having the ability to turn on, or enable citation support in some specific threads would be helpful.
I read through the thread you linked (or, what was still available of it), and I see what you're getting at. However, I feel like the sentiment quoted right here goes much too far. I have a few...
I just kinda accept that this is a fuzzy concept that I won't ever know enough to have an opinion on, and avoid it like the plague.
I read through the thread you linked (or, what was still available of it), and I see what you're getting at. However, I feel like the sentiment quoted right here goes much too far.
I have a few reasons for this belief. First, sometimes partial or vague knowledge is still useful or important, as long as it is accurate (even if it is not sufficiently precise). There are a lot of topics that are deeply complicated, but which have general rules that help people navigate the day-to-day. Algebra can get complicated and unintuitive, but my high school understanding of it has been deeply enriching to my life, even if I could not sufficiently explain it at a PhD level. However, you seem to be talking about stuff at the bleeding edge of research, yet, even there it can be useful to have a vague grasp. For instance, the reproducibility crisis affecting psychology and the other social sciences. Do I have a Ph.D. in social science or experimental design? No. But, understanding that a large amount of relatively new research is overturning a lot of my conventionally held wisdom tips me off that I should remain skeptical of a lot of that conventional advice until the expert community comes to a new consensus. Following that new research leaves me more informed, even if I am not in an intellectual position to create novel research in the field myself.
Second, living in a democracy, it is our duty to make decisions on a plethora of topics, some deeply complicated. Science can answer questions like, "What is the probability distribution of deaths in the event of a reactor meltdown?", but it cannot answer questions like, "Is that an appropriate risk given the economic benefits? Will the people be okay with this trade off?". That second set of questions can only be answered in a political process that also cites deep and complicated research from an entirely different field (economics), but must gain approval from the masses for political legitimacy. Those questions should not only be answered by the very few people who have PhDs in both nuclear physics and nuclear economics. Sure, it is very important for experts to give us the facts and to contextualize those facts as neutrally as possible, but we shouldn't avoid having an opinion like the plague! Foreign policy is complicated, U.S. involvement in Syria is complicated, much less the rest of the Middle East. Experts must be consulted. But change can only occur if there is political will for it, and that means entrusting the lay people to have opinions.
Third, if we don't trust anyone but experts to engage with the experts, we leave them entirely to self-regulation. While in some places this can make sense, it can also lead to deeply troubling political outcomes. For instance, the methodology you espouse is essentially the same reasoning that leads to regulatory capture. ISPs understand the intricacies of being an ISP much better than anyone else, so an ex-Verizon executive should run the FCC. Only someone deeply engrossed in the fossil fuel industry is qualified to understand its supply chains and motivations, so someone from that industry should be put in charge of regulating it. Barbers know who the best barbers are, so people should be required to be licensed before they can cut hair for money (!!). The list goes on, but my point is that when left unchecked by the rest of society, a small group (even of highly educated people) is liable to swerve from common sense towards corruption. I am not saying that modern science is currently this way, but if we are sufficiently convinced that we shouldn't even try to understand why they believe certain things without formal degrees, it is an inevitable outcome.
Finally, in the conversation you cite, you argue that what we should do is evaluate the credibility of our sources, and then choose whether to believe them or not1. By asking Amarok to provide sources, we can engage in exactly that evaluation. Is Amarok getting his information primarily from Berkeley, as in that first link, or some sketchy site? Are they representing one side of an issue that is legitimately controversial in its field, or are they repeating fringe theories? These questions can be evaluated by examining their citations, even if we don't try and interpret the primary sources ourselves. Ideally, Amarok is acting as a tertiary or even a quaternary source, and so citing quality secondary and tertiary sources can make their claims more credible.
Ultimately what I'm saying is this: yes, these topics are complicated, and yes, as lay people, we should not presume to have knowledge equivalent to experts. But, the solution is not to run in the opposite direction and plug our ears to big issues, but to continue to struggle with these issues and temper our confidence to be in line with our learning.
An aside: this too seems like a skill that requires ever more specialization to master. In fact, it is not uncommon to hear arguments that journalists are themselves these experts, but that leaves a remaining question: which journalists do you trust to find which scientists to trust to find which research to trust?
Asking purely as an amateur, can you explain why graphite moderators would be desirable for modern thorium reactors, given Wigner Effect, and the safety risks that graphite piles and moderators...
Asking purely as an amateur, can you explain why graphite moderators would be desirable for modern thorium reactors, given Wigner Effect, and the safety risks that graphite piles and moderators have posed, historically?
Reactor graphite (PDF warning) is relatively reactive, oxidizable, and easily contaminated. Though there's a long history of use, it's well-studied, and most of the operating safety risks can be mitigated through reactor design, graphite is still a hellish hazard if it releases combustible CO or directly ignites during a reactor meltdown.
The simple version is that you've got to slow down your neutrons enough so that they can be captured by the fuel to generate more reactions, and you have to do it in a truly hellish environment....
The simple version is that you've got to slow down your neutrons enough so that they can be captured by the fuel to generate more reactions, and you have to do it in a truly hellish environment. Graphite is cheap and tough and great at slowing down neutrons passing through it, so barring someone developing another method (and I've never even seen that talked about) the graphite is here to stay.
Look on the bright side. Since molten salt reactors have no mechanism that can result in a meltdown, it eliminates the risk of the reactor blowing that stuff all over the landscape.
The worst scenario I can think of (such as intentionally blowing up a MSR core with a bomb) would drop the graphite into the drain tank along with the molten salts and some amount of nuclear reactivity would continue around the graphite.
Probably not enough to sustain a reaction for long, though. The physical geometry of the core is crucial to producing the surplus neutrons and capturing them to burn the fuel and transmute the thorium around the core. It's barely above break-even when it's optimal. Any loss of salt geometry is going to stall the reactor.
So, worst case, you have a hell of a hot mess in the drain tank. Most of the salt is solid after a brief cooling period, some around the graphite may still be reacting and hot enough to remain liquid. It won't be able to go critical and burn its way out of there, though. Big designs use several meters of concrete for the tank walls and foundations. It'll just sit and sizzle until someone cleans it up. The graphite would probably melt its way to the floor of the tank and end up sitting atop the concrete. It'd lose half the neutrons to the floor right there and that's game over for the reaction.
Decommissioning and cleaning up these salts is a dangerous, expensive job, too. They let the salts at oak ridge for the first MSR in the 60s sit in the tank too long (a couple of years) and ended up with a multimillion dollar cleanup job.
Overall, although existing and new nuclear reactors may indeed be part of a long-term carbon-free energy mix in the United States, the public has good reason to be skeptical that thorium can or should play any role in the future.
This doesn't jive with my current understand of proposed designs for LFTRs, which include passive safety and basically guarantee there can be no catastrophic meltdown event. This article seems to be using very precise language to 'fact-check' and then summarizing or paraphrasing to support its own facts, which is a weird pattern.
The short version is the author of the article doesn't understand nuclear decay chains. Thorium and Uranium have very different chains, and the Thorium chain is vastly superior in every way, producing much (relatively) safer byproducts. Only an idiot or a madman would run these reactors on Uranium unless they are trying to burn up old Uranium waste from existing reactors.
Existing Plutonium is wonderful if you can get it, since it'll jump-start Thorium reactors. They do need seed fuel until the Thorium reaction becomes self-sustaining and produces its own fuel. Great way to get rid of decommissioned warhead material.
You are right about the core design, though. Molten salts are a way to perform nuclear chemistry safely, and the safety systems will work just fine to that end no matter the fuel.
This is just pure bullshit and coming from a professor no less, that's disappointing. Since you can throw out the entire pressurized water bullshit, the cost of a plant craters until it fits in a shipping container and can be made on an assembly line. This article is a hit piece, not real science.
When you ask existing nuclear engineers these questions, they answer from the existing body of knowledge and are universally uninformed on this topic. This is not surprising since until about five years ago, nothing at all about thorium or molten salt was taught to people completing a PhD track in nuclear engineering. They just don't know the science because it's not part of our university system. In fact the only thing they have in common is graphite moderators to slow down the neutrons. It's like comparing a car to a jet because they both have wheels.
The whole point of thorium molten salt is to dispose of the paradigm these folks have lived with and worked on for decades. It's not surprising, but it is illustrative of the uphill battle thorium has had to fight against the existing industry just to be taken seriously.
I'll keep linking the same answer I give in every thorium thread. Expert information presented by the most knowledgeable person in the field.
You might also enjoy the ridiculous number of citations and studies in this reddit thread.
I don't know if the specific information you're interested in is covered in them, but I saw these linked to elsewhere and they seem good (and are written by a reactor physicist with a Ph.D. in nuclear engineering):
I'm basically one of those people who now derails threads by recommending Tildes-centric ideas, so I'll jump in here on a complete tangent:
There are certainly threads where I feel like dedicated first party support—i.e. from Tildes—for citations attached to a comment, would be a monumental help in establishing credibility and quality discussion. Even if it was a simple list of displayed sources with enriched metadata, it doesn't have to be perfect on first attempt.
Obviously, this is not something needed for every thread, but having the ability to turn on, or enable citation support in some specific threads would be helpful. It's clear that internet discourse is broken, and I don't know if Deimos has publicly commented on whether it's the goal for Tildes to attempt to fix that (probably not), but this would be a positive step, IMO.
Tildes, functionally, should be more than just a Reddit clone.
If someone wants to add citations to a comment, I feel like they can already do it easily by just adding links, either at the relevant places in the comment or just at the bottom. What would a dedicated feature do differently or better?
@cfabbro too, if there's something specific you were thinking of.
I think perhaps what they are after is some kind of 'citation requested' label. Some way to indicate you'd like the author to provide more details.
That is not what I was referring to (see my reply), but would also be a great feature! :) Added to gitlab:
https://gitlab.com/tildes/tildes/issues/619
I was thinking more along the lines of potentially being able to add citations to other people's comments and to threads/topics, but I don't know if that's what @emdash was specifically referring to.
I also think having an official citation system would encourage people to actually cite their sources more often, which could help improve the level of discourse here. I don't think it's a game changer, or strictly necessary in every thread/topic (which is why the toggle is a good idea, IMO), but I think it could be an improvement over just relying on markdown, especially in certain, more formal, academically minded groups (e.g. ~science, ~humanities) and topics/threads.
Another potential benefit to it could be the ability to automatically scrape some metadata on the source and include that in the citation. And another could also be formatting related; An official system could support a more formal structure to citations, like those used in bibliographies or on wikis, rather than just your standard hyperlinks on chunks of text within the comment.
Adding citations to other comments is also a good idea, IMO. But for me, @Deimos, it's the encouragement and explicit support that such a feature would provide that is the primary selling point. If you promote a feature, people will use it, and be aware of it as a general thing as part of the community. It makes it a first class citizen of Tildes and raises the bar of expected quality when a citable thread is created.
As I said, it doesn't have to be some stodgy "you must format your citations in this format, and provide exact references for each claim you make", but some kind of freeform community-based citation gathering tool that can attach to comments seems like a novel and interesting idea that might be worth exploring?
It looks like there's actually a footnotes extension already included in GitHub's commonmark that just needs to be enabled (and isn't currently for Tildes).
It's not included in the spec and there doesn't really seem to be any formal documentation, but it looks like it probably works close to how other markdown footnotes do. There's a little section in their testing file here that shows how you can write some footnotes and the output it expects: https://github.com/github/cmark-gfm/blob/master/test/extensions.txt#L645
So yeah, it looks like I should just be able to enable that (and I don't really see any reason not to).
Oooh, I really like that idea. Added to Gitlab:
https://gitlab.com/tildes/tildes/issues/618
I read through the thread you linked (or, what was still available of it), and I see what you're getting at. However, I feel like the sentiment quoted right here goes much too far.
I have a few reasons for this belief. First, sometimes partial or vague knowledge is still useful or important, as long as it is accurate (even if it is not sufficiently precise). There are a lot of topics that are deeply complicated, but which have general rules that help people navigate the day-to-day. Algebra can get complicated and unintuitive, but my high school understanding of it has been deeply enriching to my life, even if I could not sufficiently explain it at a PhD level. However, you seem to be talking about stuff at the bleeding edge of research, yet, even there it can be useful to have a vague grasp. For instance, the reproducibility crisis affecting psychology and the other social sciences. Do I have a Ph.D. in social science or experimental design? No. But, understanding that a large amount of relatively new research is overturning a lot of my conventionally held wisdom tips me off that I should remain skeptical of a lot of that conventional advice until the expert community comes to a new consensus. Following that new research leaves me more informed, even if I am not in an intellectual position to create novel research in the field myself.
Second, living in a democracy, it is our duty to make decisions on a plethora of topics, some deeply complicated. Science can answer questions like, "What is the probability distribution of deaths in the event of a reactor meltdown?", but it cannot answer questions like, "Is that an appropriate risk given the economic benefits? Will the people be okay with this trade off?". That second set of questions can only be answered in a political process that also cites deep and complicated research from an entirely different field (economics), but must gain approval from the masses for political legitimacy. Those questions should not only be answered by the very few people who have PhDs in both nuclear physics and nuclear economics. Sure, it is very important for experts to give us the facts and to contextualize those facts as neutrally as possible, but we shouldn't avoid having an opinion like the plague! Foreign policy is complicated, U.S. involvement in Syria is complicated, much less the rest of the Middle East. Experts must be consulted. But change can only occur if there is political will for it, and that means entrusting the lay people to have opinions.
Third, if we don't trust anyone but experts to engage with the experts, we leave them entirely to self-regulation. While in some places this can make sense, it can also lead to deeply troubling political outcomes. For instance, the methodology you espouse is essentially the same reasoning that leads to regulatory capture. ISPs understand the intricacies of being an ISP much better than anyone else, so an ex-Verizon executive should run the FCC. Only someone deeply engrossed in the fossil fuel industry is qualified to understand its supply chains and motivations, so someone from that industry should be put in charge of regulating it. Barbers know who the best barbers are, so people should be required to be licensed before they can cut hair for money (!!). The list goes on, but my point is that when left unchecked by the rest of society, a small group (even of highly educated people) is liable to swerve from common sense towards corruption. I am not saying that modern science is currently this way, but if we are sufficiently convinced that we shouldn't even try to understand why they believe certain things without formal degrees, it is an inevitable outcome.
Finally, in the conversation you cite, you argue that what we should do is evaluate the credibility of our sources, and then choose whether to believe them or not1. By asking Amarok to provide sources, we can engage in exactly that evaluation. Is Amarok getting his information primarily from Berkeley, as in that first link, or some sketchy site? Are they representing one side of an issue that is legitimately controversial in its field, or are they repeating fringe theories? These questions can be evaluated by examining their citations, even if we don't try and interpret the primary sources ourselves. Ideally, Amarok is acting as a tertiary or even a quaternary source, and so citing quality secondary and tertiary sources can make their claims more credible.
Ultimately what I'm saying is this: yes, these topics are complicated, and yes, as lay people, we should not presume to have knowledge equivalent to experts. But, the solution is not to run in the opposite direction and plug our ears to big issues, but to continue to struggle with these issues and temper our confidence to be in line with our learning.
Asking purely as an amateur, can you explain why graphite moderators would be desirable for modern thorium reactors, given Wigner Effect, and the safety risks that graphite piles and moderators have posed, historically?
Reactor graphite (PDF warning) is relatively reactive, oxidizable, and easily contaminated. Though there's a long history of use, it's well-studied, and most of the operating safety risks can be mitigated through reactor design, graphite is still a hellish hazard if it releases combustible CO or directly ignites during a reactor meltdown.
The simple version is that you've got to slow down your neutrons enough so that they can be captured by the fuel to generate more reactions, and you have to do it in a truly hellish environment. Graphite is cheap and tough and great at slowing down neutrons passing through it, so barring someone developing another method (and I've never even seen that talked about) the graphite is here to stay.
Look on the bright side. Since molten salt reactors have no mechanism that can result in a meltdown, it eliminates the risk of the reactor blowing that stuff all over the landscape.
The worst scenario I can think of (such as intentionally blowing up a MSR core with a bomb) would drop the graphite into the drain tank along with the molten salts and some amount of nuclear reactivity would continue around the graphite.
Probably not enough to sustain a reaction for long, though. The physical geometry of the core is crucial to producing the surplus neutrons and capturing them to burn the fuel and transmute the thorium around the core. It's barely above break-even when it's optimal. Any loss of salt geometry is going to stall the reactor.
So, worst case, you have a hell of a hot mess in the drain tank. Most of the salt is solid after a brief cooling period, some around the graphite may still be reacting and hot enough to remain liquid. It won't be able to go critical and burn its way out of there, though. Big designs use several meters of concrete for the tank walls and foundations. It'll just sit and sizzle until someone cleans it up. The graphite would probably melt its way to the floor of the tank and end up sitting atop the concrete. It'd lose half the neutrons to the floor right there and that's game over for the reaction.
Decommissioning and cleaning up these salts is a dangerous, expensive job, too. They let the salts at oak ridge for the first MSR in the 60s sit in the tank too long (a couple of years) and ended up with a multimillion dollar cleanup job.
From the article: