[MP-Ryan]

The sad thing is that I work with a bunch of very environmentally-conscious people, and the large majority of them cannot grasp the information contained in that fairly simple graphic.  Instead, whenever I scoff in the general direction of wind/solar and say nuclear!, they immediately say Chernobyl!, and now, Fukushima!.

The problem is that anyone with a little bit of science physics/chemistry background knows full well that nuclear is the best general option for stable and reliable energy.  But the rest of the population, that outvotes us by crazy margins, doesn't.  And damned if I've ever seen that elusive beast, the credible-scientist-turned-effective-federal-politician.

TL;DR:  Energy policy sucks because the general population is ignorant and believes the fear-mongering.

[666maslo666]

The Xe 135 poisoning in the Chernobyl reactor was holding down the power of the #4 reactor and it made it difficult for the inexperienced operators to get a handle on the power level of the reactor. They were in a state of confusion because the position of the control rods didn't have the expected effects on the power level of the reactor. That, plus the fact that they knew almost nothing about the test they were supposed to be doing, led to the ridiculously unsafe operating condition of the #4 reactor.

Ok I see where you're coming from now.  Although I still maintain it's not holding down or delaying the power, what it WOULD do is change the estimated critical position of the control rods.  Xenon production is just a fact of nuclear reactors though.  It's easily compensated for, and it decays away on its own.  Manually stripping it out would do very little for you.  I don't recall specifically the operators not compensating for xenon.  If that really happened, the russian operating procedures/training were flat out wrong, and I'm amazed they were able to operate at all.  Or the operators had the biggest "woops" in history if they just forgot.

And yeah, we could use the U/Pu fuels if the hippies would quit getting their panties in a bunch over it. The Th fuel cycle produces fewer long-lived transuranic waste products, though, and since the liquid fuel is essentially self-refuelling, it results in less storage. I agree with you in that there's really no pressing need to switch to the Th fuel cycle, but at some point, the nuclear industry and people that are capable of thinking rationally are going to have to essentially shove nuclear power down the throats of the Fox News controlled sheep and there will be a lot less bile if we can increase safety and decrease waste production. None of the waste storage would be a concern if everyone would just listen to me and make a railgun capable of escape velocity that fires the waste into the sun, though. 

I agree that eventually thorium fuel will become important (economically if not actual need due to lack of other fuel), but I think it's a very long way off.  And I think it's progressing at just about the perfect rate.  We already have alternatives like MOX and reprocessed fuel closer to implementation right now.  I'm not sure what to make of the Fox News comment.  Conservatives are generally far more accepting of nuclear power than liberals*.  Safety and waste aren't even problems NOW, we just need people to stop saying they are.  Even if we DON'T reprocess, we aren't in danger of running out of room for waste anytime soon, with or without a repository. 

*generalization

About the two-fluid molten salt design: it burns U 233 in the core and the secondary loop has Th to absorb neutrons and be transmuted into U 233 by way of Pa 233. The only chemical processing involves removing the Pa 233 from the second loop by fluorination and holding it while it decays into U 233. The major design difficulty is that the plumbing is made of graphite because it absorbs neutrons and doesn't dissolve in the salts, but it has a tendency to expand and become brittle. Obviously, that's not a great property for a pipe to have. The single fluid design has both the U 233 fuel and the Th in the same loop, but the processing is MUCH more complicated. I prefer the two-fluid design because I believe we have the materials science necessary to find piping materials that will be able to absorb neutrons, operate and the necessary temperatures, and not dissolve in the salts. You're correct in the assertion that the MSRs that have been operated were prototypes - they were also very old. We can do this now. If not, there are plenty of other more conventional designs in the works, too.

I'm still not wrapping my head around this.  Are we talking about MOVING fuel here?    And why on earth do we WANT piping to absorb neutrons?  Do you mean scatter?  Is the piping being used as a moderator?  I'd love to take a look at this design if you have a link or something.
Engineering issues aside, I also have doubts about the desirability of a liquid metal plant from an operating standpoint.  Foremost, the necessity of keeping the coolant melted in a shutdown condition.  I don't know how pumping of liquid metals works, but I have to imagine it's a *****.  Likewise for the maintenance of the plant components.  I don't know if sodium activates off the top of my head, and I'm feeling too lazy to look it up right now, but it DOES tend to explode does it not?  A pipe rupture accident would be a whole new level of "oh ****."  LOCAs are bad enough without the leaking coolant exploding 

You're not coming across as an ass at all, for the record.

thanks, that's good to know.

I believe you are misunderstanding TwentyPercentCooler. He is not talking about liquid metal reactors (sodium, lead..), but molten SALT reactors (ionic compound), such as LFTR (liquid fluoride thorium reactor), where both primary coolant and fuel itself is in the form of a molten salt (no solid fuel, no reactive metal). Google "Kirk Sorensen" or "Flibe Energy". There is a difference between reactive molten metal and inert molten salt, and between solid fueled only liquid salt cooled MSRs and actual liquid fueled liquid salt cooled MSRs (LFTR)

This is the technology that will save humanity:
http://thoriumremix.com/2011/

[Cyborg17]

The real problem with this discussion is that neither Klaustrophobia or TwentyPercentCooler posted a source.  It's a good idea to post sources on information in specialized fields.

These quotes from the second link are pretty exciting:

 "This is because they [molten salts] are already in their most stable chemical form. Their properties do not change even under intense radiation, unlike all solid forms of nuclear fuel."

"LFTR addresses this issue by using a form of nuclear fuel (liquid-fluoride salts of thorium) that allow complete extraction of nuclear energy from the fuel."

[Aardwolf]

The easier solution is to use LED lightning...

True but off-topic

[jr2]

The easier solution is to use LED lightning...

True but off-topic

Use both FTW, now back to the topic..

[666maslo666]

The real problem with this discussion is that neither Klaustrophobia or TwentyPercentCooler posted a source.  It's a good idea to post sources on information in specialized fields.

These quotes from the second link are pretty exciting:

 "This is because they [molten salts] are already in their most stable chemical form. Their properties do not change even under intense radiation, unlike all solid forms of nuclear fuel."

"LFTR addresses this issue by using a form of nuclear fuel (liquid-fluoride salts of thorium) that allow complete extraction of nuclear energy from the fuel."

Yes, thats why LFTR is so safe - the radioactive fuel is in the form of inert molten thorium fluoride salt. And I especially like the "freeze plug" passive safety solution - overheating automatically causes the fuel salt to drain into subcritical storage tank.

http://en.wikipedia.org/wiki/Molten_salt_reactor#Safety

- Molten fluoride salts are mechanically and chemically stable at sea-level pressures at intense heats and radioactivity. There is no way they can burn, degrade or explode.
- There is no high pressure steam or water in the core, just low-pressure molten salt. Since the core is not pressurised, it cannot explode.
- Fluoride combines ionically with almost any transmutation product. This is an MSFR's first level of containment. It is especially good at containing biologically active "salt loving" wastes such as Cesium 137.
- Given an accident beyond the design basis for the multiple levels of containment, dispersion into a biome is difficult. The salts do not burn in air or water, and the fluoride salts of the radioactive actinides and fission products are generally not soluble in water or air.
- Molten-fuel reactors can be made to have passive nuclear safety: Tested fuel-salt mixtures have negative reactivity coefficients, so that they decrease power generation as they get too hot.
- Because the fuel and the coolant are the same fluid, a loss of coolant removes fuel from the reactor and thus terminates the nuclear reaction.
- Most MSFRs include a freeze plug at the bottom that has to be actively cooled, usually by a small electric fan. If the cooling fails, say because of a power failure, the fan stops, the fuel in the plug melts, and the fuel drains to a subcritical storage facility, totally stopping the reactor.

And compared to standard once-through uranium cycle, thorium breeder cycle produces very little waste, which is also shortlived: 1GW ordinary uranium-fueled LWR plant produces 35 t of waste in one year, which requires 10 000s of years to reach safe radioactivity levels. In comparison, 1 GW LFTR plant would produce only 170 kg of waste in one year, and this waste becomes safe after just 300 years of storage.

[Cyborg17]

It sounds like someone got the cheat codes for life. 

[General Battuta]

The real problem with this discussion is that neither Klaustrophobia or TwentyPercentCooler posted a source.  It's a good idea to post sources on information in specialized fields.

While I can't speak for 20%CHILL our friend Klaus does work in the nuclear field and while this doesn't make him omniscient it certainly lends an air of listen the **** up

[Cyborg17]

It doesn't matter where he works, what they both said are based only on what they both said, so that it's going to be an argument that lasts until someone decides to stop arguing.  What's the point in that?  And if it was a misunderstanding, like maslo thinks, then posting a source would probably clear everything up.

[perihelion]

As someone who has had this exact discussion with Klaustrophobia before, he knows the difference between a liquid metal reactor and a liquid salt reactor.  It is not a subtle difference.

And anyone who thinks that liquid salt is "inert" is daft.  High temperature halogen chemistry deserves its own graduate degree.  It can wreak holy hell on most structural materials.  Thus the aforementioned "plumbing problem."

[666maslo666]

And anyone who thinks that liquid salt is "inert" is daft.  High temperature halogen chemistry deserves its own graduate degree.  It can wreak holy hell on most structural materials.  Thus the aforementioned "plumbing problem."

Fluoride salts are indeed very chemically stable and there are a number of well proven combinations of fluoride salt and certain metal alloys usually nickel based superalloys. While they sound exotic you can buy most of them quite readily. Hastelloy N (especially with small amounts of Ti or Nb) is the most promising option, it performs extremely well with fluoride salts, at 700C and perhaps a bit more it will last a very long time and has extremely low corrosion rates. No engineering breakthroughs are required to make working fluoride salt based molten salt reactor, it has been done twice before, both very successful test programs, one running literally for years at Oak Ridge National Laboratory (ORNL).

http://en.wikipedia.org/wiki/Molten-Salt_Reactor_Experiment
http://en.wikipedia.org/wiki/Hastelloy

Materials science has progressed immensely in the last decades, and I am sure resistance to hot fluoride salts would not be a problem, when it was not a problem in the sixties.

[TwentyPercentCooler]

I hope nobody thought we were actually arguing, I thought it was a nice discussion.

And yes, to absolutely clear up any confusion, I was referring to a reactor in which the fuel is kept in the form of fluoride salts, more specifically, uranium tetrafluoride in the main loop. The problem with the plumbing is that whatever it's made of must have the capacity to absorb neutrons and must not be dissolved in the salt. Back when these reactors were proposed, around 50 years ago, graphite was the only option we had. And it just didn't work well enough, because it had the tendency to expand and become brittle and the graphite pipes were leaking. There are several proposed options now that take advantage of the last 50 years' worth of materials engineering and I think we could find something without insurmountable difficulty. Another thing to keep in mind is that while the salts themselves are very much inert, any loose fluorine tends to form hydrofluoric acid.

And yes, the fuel is moving, and as one poster already mentioned, in the event of a failure, it melts a plug in the primary loop and falls into tanks with subcritical volume, safe and ready to be pumped back in to the primary loop once the reactor is repaired. This kind of resiliency alone, in my opinion, is worth finding a solution to the problem of the pipes. We've all just recently seen the some of the problems with solid fuel rods at Fukushima. The Th fuel cycle produces less waste and the waste has a much shorter half-life, owing to the general absence of transuranics.

Anyway, I didn't link sources because first of all, I'm doing almost all of this from memory. I'm not some kind of supergenius, I'm just very interested in this sort of thing, hence why I said "This is my can o' worms" at the beginning of the thread. Some of you guys know programming, I don't. Some of you guys do modeling and texturing, which I'm mostly useless at. But I saw this thread and got excited because I like talking about it. I'm shooting for a PhD in nuclear physics, so this isn't armchair science. Also, really, if anyone's interested, you have access to the same internet that I do. 

[Klaustrophobia]

Yeah, I was wrong and thought you were talking about liquid metal coolant reactors.  Other than the aforementioned discussion with perihelion that I vaguely remember, I have honestly never heard of the one you are talking about.  Until I've done some reading, I'll not comment on it other than to say the idea of a liquid, moving fuel is ... I'm not sure how to phrase this... worrying?  I guess I'm naturally skeptic of things I don't understand.

As for my source, I've never really understood this board's rabid obsession with demanding one.  Can't people have ideas, reasoning, and conclusions of their own?  In any case, my source for this matter is 4 years of study at university.  Sorry, I can't link to that.  I asked for a source from 20 because I was confused and wanted to see this design if possible.

20%, if you don't mind my asking, where are you in the pipeline for the PhD?  Research isn't my thing, so I was done after the B.S.  I'd rather design/build/operate than do theory that won't be implemented for years. 

[MP-Ryan]

As for my source, I've never really understood this board's rabid obsession with demanding one.

It's the result of people like Liberator, High Max, Trashman, et al spouting bull**** with no grounding in fact and getting called on it.  The people correcting them got tired of lecturing and finally just demanded sourcing.  Those who were unable to provide it and yet continued the bull**** claims were eventually Monkey'd or banned.

Most people have the decency not to demand sourcing from people who actually know what the hell they're talking about.  That said, I've only been asked for sourcing a handful of times despite posting some pretty obscure information, so people really SHOULD be willing to ask for it more often.

[TwentyPercentCooler]

Yeah, I was wrong and thought you were talking about liquid metal coolant reactors.  Other than the aforementioned discussion with perihelion that I vaguely remember, I have honestly never heard of the one you are talking about.  Until I've done some reading, I'll not comment on it other than to say the idea of a liquid, moving fuel is ... I'm not sure how to phrase this... worrying?  I guess I'm naturally skeptic of things I don't understand.

As for my source, I've never really understood this board's rabid obsession with demanding one.  Can't people have ideas, reasoning, and conclusions of their own?  In any case, my source for this matter is 4 years of study at university.  Sorry, I can't link to that.  I asked for a source from 20 because I was confused and wanted to see this design if possible.

20%, if you don't mind my asking, where are you in the pipeline for the PhD?  Research isn't my thing, so I was done after the B.S.  I'd rather design/build/operate than do theory that won't be implemented for years.

I'm still a young, bright-eyed 4 year uni student at the moment.

http://nuclear.inl.gov/gen4/msr.shtml has a pretty good schematic of a two-fluid reactor. The fuel salt is ²³³UF₄, the coolant salt is ²³²ThF₄ (I think) that gets transmuted to ²³³U by way of ²³³Pa.

That advantages of having a liquid fuel, as far as I can see, is that you don't have to worry about steam voids or a loss of coolant causing a meltdown of solid fuel. Plus, it's possible to process out neutron poisons if one was so inclined and thus the actual parameters of operation can be effectively simplified. Basically, the difficulty is frontloaded: materials science and halogen chemistry go into the design, but the actual operation would be less involved, comparatively. One of the reasons the Chernobyl accidents happened, as I touched on before, was that the main operator of the graveyard shift not only wasn't familiar with the procedures of the test, he was also inexperienced. Just from looking at the timeline of the events, it looks to me like he wasn't exactly familiar with the operation of the RBMK design, because he seemed to be confused by the actions of neutron poisons in the core and the differences that they were causing between the expected effects of control rod positioning and the actual effects.

http://www.gen-4.org/Technology/systems/msr.htm is a short article by itself but has a very extensive list of sources, if you're interested.

[Klaustrophobia]

I'm still a young, bright-eyed 4 year uni student at the moment.

enjoy it.  they'll beat that out of you soon enough.  some last longer than others, but ALL are close to dropping out by the end   my class started at 47.  we graduated 20.

what school?

[TwentyPercentCooler]

I'm still a young, bright-eyed 4 year uni student at the moment.

enjoy it.  they'll beat that out of you soon enough.  some last longer than others, but ALL are close to dropping out by the end   my class started at 47.  we graduated 20.

what school?

North Carolina State. I'd like to get my PhD at a different school, but I wasn't the most sensible person in high school, so I sort of narrowed my own options for a BS and it doesn't make much sense to move somewhere else just for a graduate program. Oh well, I'm perfectly happy. No chance of dropping out, I'm tenacious. Or criminally stubborn. Take your pick. 

Read up on the molten salt designs (assuming you have time) and let's see if we can't get another convert.

[Klaustrophobia]

no ****?  that's where i graduated!  do i know you IRL?????   

tell Dr. Doster his favorite student says hi.  and take NE 235.  trust me on this.  sophmore year is best, junior works too.

[Mongoose]

Man, wish I'd had that option at my school.  Maybe then I could be doing something, instead of sitting here jobless a few years removed from a physics degree I wound up intensely disliking by the end.

[666maslo666]

http://energyfromthorium.com/ - this is a great site about thorium energy and LFTR reactor design, it also has a really comprehensive resource and research paper repository and an active discussion forum with members from Flibe Energy.