I'm a complete neophyte to this technology, coming from the mechanical engineering side and therefore well aware of my ignorance about the basic chemistry involved. That said, one man's trash can be another's treasure, to wit; isn't tritium an ideal fuel for emerging nuclear fusion designs?
Corrosion in not stalling MSR startups. Some use online chemistry to keep the salts pure. Some target short vessel lifespans and intend to regularly replace them as a subscription service. Funding is the primary constraint. It impacts some MSR startups more than others (some have lots of funding!), but is always the most-cited constraint on rapid commercialization.
Okay, I'll bite; what is this magical moderator they speak of that will allow for a nearly order of magnitude decrease in core size for the same MW output?
I think the point is we don't know. I'm entirely open to the concept that this is possible, but also know that Transatomic Power seemed to think along similar lines and couldn't prove a non-graphite moderator offered what they thought it could. Someone has to test it, then they know. And after they know (good or bad) they'll probably talk about their moderator concept.
@@gordonmcdowell I think it is Heavy water. It's the only one that moderates strongly but allows low enough absorption that they can burn spent fuel without enrichment or reprocessing. Either that or some kind of deuteride that is a covalent compound. But all the other covalent compounds are degraded in high neutron fields, and they rearrange into compounds that are either volatile or form tarry substances with a different pka, so then you get acid/base reactions, and you get sludge at the bottom of the moderator tank. Daniel already ruled out Beryllides for toxicity reasons. Lithium compounds were ruled out because of tritium generation. The next atom that moderates well is carbon, but you can't really get any better carbon density than graphite, and they're avoiding graphite. And then everything after that is basically too high Z to moderate well enough without losing out in moderation ratio to plain old graphite. Now deuterides or heavy water will have pretty significant tritium problems. But. D2O -> T2O does not change the hydrogen balance in the overall system. Going from Lithium + n -> T + He you are transmuting an alkali metal to 2 different gases, plus the T will change your redox potential, causing corrosion (Assuming the Lithium is in a molten salt melt). Going from D2O -> T2O does not change your overall balance. There is established experience in CANDU reactors and research reactors using heavy water as moderator. There are established tritium scrubbers for heavy water systems as part of the CANDU supply chain. en.wikipedia.org/wiki/Neutron_moderator The alternative would be light water, but then the absorptions would force higher enrichments, which destroys the reactors "waste burning" potential.
@@MonMalthias The issue with heavy water is it is not effective enough for an 8 fold decrease in moderator size as the video claims. It would seem only protium could pull this off (and lots of it), but then, as you stated, you have issues with neutron absorption hurting economy. On a similar note, I don't think the D+n->T reaction is that big of a deal as the cross section at thermal is a fraction of a millibarn, also tritium is a weak beta emitter and has gotten a 'bad rap' as far as radioactive materials are concerned and isn't nearly as big a problem as some people let on.
It's another molten salt, one containing neutron moderating elements. Its quite easy actually, after this you just have a reactor that produces heat, so the pressure inside the reactor is very low, and doesn't require thick steel construction. For an even more aggressive example look up the Moltex reactor concept where the pressure in the reactor core is 1 bar.
After seeing a lot of recent info on what type of testing MSR companies are working on, it seems like the Oak Ridge experiment might have been incredibly irresponsible? They definitely weren’t able to computationally model neutron economy, fluid dynamics, etc.. With that said, where would we be today if funding would have continued from ~1960 to now.
It is one thing to model, and another thing to actually test it physically. I don't think ORNL was incredibly irresponsible - far from it. They had the AHR, the ARE and molten salt loop experiments to work off of. Did they need to know the behaviour of every fluid current and every neutron in the reactor? No, and I would argue that losing oneself in models, however useful, does not substitute for actually building it and testing it. Sure, emergent behaviours might spoil your day, but you learn from mistakes better than you do from optimising a computer simulation. And in the end, there was no radiation leak from the MSRE - something that could not be said for things like the HTR experiments, which did have nascent computer modelling to help them. Ironically it seems that the more unknowns and primitive tools were used, the more responsible the reactor experiment. Designing with slide rules forced ample margins to be left in the design - something that engineers with computer models can "optimise" away and maximise some other aspect.
Malthias I appreciate the response and agree with much of what you said, but it still seems to me there were many great uncertainties with the original experiment that still persist today. What experience could they have had dealing with molten radioactive fuel in an emergency situation? What could they have known about salts would spread through the environment, or potential volatile fission products being produced if the reactor vessel were to be breached? We still don’t know many of these things today so in hindsight I do agree it was a great learning experience- but it also could have ended a lot differently.
In abstract, the concern seems to make some sense. But when you look at the actual reactor and its activities, it was a teeny little thing, unpressurized, in a big concrete hole in the ground, that could only remain reactive by sitting happily in an intact reactor. They worked carefully and took things in sensible steps. I think they were plenty responsible.
Rick, they took conservative design approaches then, that’s how it was responsible. Their computer models were known to over or under predict certain quantities, essentially, and as long as you design on the right side, you’re safe. Point kinetics always over-estimates power spikes, if you are familiar with PKE.
They're moving ahead with plans, but reactor physics is relatively well understood today. So it makes sense to go directly from plans to energy-producing setup.
How much for one?
I'm a complete neophyte to this technology, coming from the mechanical engineering side and therefore well aware of my ignorance about the basic chemistry involved. That said, one man's trash can be another's treasure, to wit; isn't tritium an ideal fuel for emerging nuclear fusion designs?
Clears throat. Wipes off white-board. Straightens tie. Approaches microphone. "Yes."
So what, is the corrosion problem just unsolvable? It seems like all these projects stall in the same way.
Corrosion in not stalling MSR startups. Some use online chemistry to keep the salts pure. Some target short vessel lifespans and intend to regularly replace them as a subscription service. Funding is the primary constraint. It impacts some MSR startups more than others (some have lots of funding!), but is always the most-cited constraint on rapid commercialization.
@@gordonmcdowell ok thanks
@@gordonmcdowell and also molten fuel regulation
Okay, I'll bite; what is this magical moderator they speak of that will allow for a nearly order of magnitude decrease in core size for the same MW output?
I think the point is we don't know. I'm entirely open to the concept that this is possible, but also know that Transatomic Power seemed to think along similar lines and couldn't prove a non-graphite moderator offered what they thought it could. Someone has to test it, then they know. And after they know (good or bad) they'll probably talk about their moderator concept.
@@gordonmcdowell
I think it is Heavy water. It's the only one that moderates strongly but allows low enough absorption that they can burn spent fuel without enrichment or reprocessing.
Either that or some kind of deuteride that is a covalent compound. But all the other covalent compounds are degraded in high neutron fields, and they rearrange into compounds that are either volatile or form tarry substances with a different pka, so then you get acid/base reactions, and you get sludge at the bottom of the moderator tank.
Daniel already ruled out Beryllides for toxicity reasons. Lithium compounds were ruled out because of tritium generation. The next atom that moderates well is carbon, but you can't really get any better carbon density than graphite, and they're avoiding graphite. And then everything after that is basically too high Z to moderate well enough without losing out in moderation ratio to plain old graphite.
Now deuterides or heavy water will have pretty significant tritium problems. But. D2O -> T2O does not change the hydrogen balance in the overall system. Going from Lithium + n -> T + He you are transmuting an alkali metal to 2 different gases, plus the T will change your redox potential, causing corrosion (Assuming the Lithium is in a molten salt melt).
Going from D2O -> T2O does not change your overall balance. There is established experience in CANDU reactors and research reactors using heavy water as moderator. There are established tritium scrubbers for heavy water systems as part of the CANDU supply chain.
en.wikipedia.org/wiki/Neutron_moderator
The alternative would be light water, but then the absorptions would force higher enrichments, which destroys the reactors "waste burning" potential.
@@MonMalthias The issue with heavy water is it is not effective enough for an 8 fold decrease in moderator size as the video claims. It would seem only protium could pull this off (and lots of it), but then, as you stated, you have issues with neutron absorption hurting economy.
On a similar note, I don't think the D+n->T reaction is that big of a deal as the cross section at thermal is a fraction of a millibarn, also tritium is a weak beta emitter and has gotten a 'bad rap' as far as radioactive materials are concerned and isn't nearly as big a problem as some people let on.
@@gordonmcdowell Educated guess: molten heavy Sodium Hydroxide. (i.e Na OD).
It's another molten salt, one containing neutron moderating elements. Its quite easy actually, after this you just have a reactor that produces heat, so the pressure inside the reactor is very low, and doesn't require thick steel construction.
For an even more aggressive example look up the Moltex reactor concept where the pressure in the reactor core is 1 bar.
After seeing a lot of recent info on what type of testing MSR companies are working on, it seems like the Oak Ridge experiment might have been incredibly irresponsible? They definitely weren’t able to computationally model neutron economy, fluid dynamics, etc..
With that said, where would we be today if funding would have continued from ~1960 to now.
It is one thing to model, and another thing to actually test it physically. I don't think ORNL was incredibly irresponsible - far from it. They had the AHR, the ARE and molten salt loop experiments to work off of. Did they need to know the behaviour of every fluid current and every neutron in the reactor? No, and I would argue that losing oneself in models, however useful, does not substitute for actually building it and testing it. Sure, emergent behaviours might spoil your day, but you learn from mistakes better than you do from optimising a computer simulation. And in the end, there was no radiation leak from the MSRE - something that could not be said for things like the HTR experiments, which did have nascent computer modelling to help them.
Ironically it seems that the more unknowns and primitive tools were used, the more responsible the reactor experiment. Designing with slide rules forced ample margins to be left in the design - something that engineers with computer models can "optimise" away and maximise some other aspect.
Malthias I appreciate the response and agree with much of what you said, but it still seems to me there were many great uncertainties with the original experiment that still persist today.
What experience could they have had dealing with molten radioactive fuel in an emergency situation? What could they have known about salts would spread through the environment, or potential volatile fission products being produced if the reactor vessel were to be breached? We still don’t know many of these things today so in hindsight I do agree it was a great learning experience- but it also could have ended a lot differently.
In abstract, the concern seems to make some sense. But when you look at the actual reactor and its activities, it was a teeny little thing, unpressurized, in a big concrete hole in the ground, that could only remain reactive by sitting happily in an intact reactor. They worked carefully and took things in sensible steps. I think they were plenty responsible.
Rick, they took conservative design approaches then, that’s how it was responsible. Their computer models were known to over or under predict certain quantities, essentially, and as long as you design on the right side, you’re safe. Point kinetics always over-estimates power spikes, if you are familiar with PKE.
@@MonMalthias companies are working on now big conversation in Washington dc and pres trump going to look at the reg
It looks all they have is plans.
dft I am under the impression they are testing a patented moderator. Either it will work or it will not.
it’ll likely be stuff from accelerators, just look at the PhD thesis of the founders. the possibilities are in there.
They're moving ahead with plans, but reactor physics is relatively well understood today. So it makes sense to go directly from plans to energy-producing setup.
Partners in the east? Bye bye IP. 100%.
EdP IV 1) Not a very anonymous name ;) 2) yep!