Comment by lazide

Comment by lazide 6 hours ago

Thorium 232 is the thorium in the cycle yes. And all kinds of nonsense is correct for the daughter products. But in general, to actually use do anything with thorium you need excess neutrons.

Even the daughter uranium 233 only produces on average 2.48 neutrons per fission, so it’s very difficult even in a combined lifecycle process to have enough - thorium doesn’t produce uranium 233 immediately (takes almost 30 days), neutron capture with that low a ratio requires a LOT of thorium, which is going to mostly just suck up all neutrons and you won’t have any extra for addition uranium 233 fissions, etc.

It’s quite difficult (impossible?)to have actually work without a source of a large amount of additional neutrons.

JumpCrisscross 5 hours ago

> to actually use do anything with thorium you need excess neutrons

Unless 100% of those neutrons is being absorbed by the thorium, this means you'll have neutron flux at the boundary. Which, for a liquid moderator, means all the pipes and tanks and pumps.

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lazide 4 hours ago

It’s almost like there is a reason why it’s not commonly used despite all the hype.

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- hunterpayne 2 hours ago
  
  Sure, if you ignore all the parts of the neutron economy that make it possible to work. The part everyone missed in this discussion is that all of the numbers of neutrons (and their barns) aren't constants. Since the fuel is a fluid, you can use density and shape to improve the neutron economy in the reactor core. Basically, when the atoms are closer together, the economy improves. You can also use a better moderator like graphite since the basic design is safer and the rate of fission is just easier to control.
  And considering that people made these things work 60 years ago without modern computers, the idea that its impossible or needs 40 years of research seems pretty far fetched. What is left of the nuclear industry wants to build current designs like the AP1400. That is a great idea, but there are things you can do with a LFTR that you can't do with an AP1400. The biggest of them is making synthetic fuel. The other advantages are the amount of waste produced and the fact that you can make a LFTR into a waste burner consuming the spent fuel rods from a AP1400. The downside is you actually have to fix nuclear regulations to do this and getting politicians to do that has proved impossible.
  There are no technological barriers, this is entirely political.
  
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  JumpCrisscross an hour ago
  
  > What is left of the nuclear industry wants to build current designs like the AP1400
  That's just Westinghouse. There is a lot of research happening in small and medium-sized reactors.
  > There are no technological barriers, this is entirely political
  To thorium MSRs? The main barrier is economic.
  
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  lazide an hour ago
  
  Nah, it’s just hard and silly - without a lot of payoff. When there are plenty of easier options for most nations.
  That you’re even discussing graphite moderated (?!!) makes this pretty clear.
  
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  hunterpayne 4 minutes ago
  
  > That you’re even discussing graphite moderated (?!!) makes this pretty clear.
  And why would this be? Is graphite expensive? No it isn't. Also, we created a working one of these designed in the 1960's without computers. You seriously think this is hard compared to other types of engineering we do today?
  A LFTR can also do things that a PWR or BWR can't and has several major advantages. But since it uses pencil lead apparently we can't even try it.
  
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