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LostCosmonaut

Random Nuclear Stuff

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Not sure why anyone would want to compress uranium. Not sure at all.

 

Also, I just noticed yesterday that the sequence of names for elements 92-94 follows the order of planets in the solar system. I feel kind of dumb for just realizing that now.

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Isentropic processes are pretty much entirely theoretical (basically it's a perfectly reversible process that takes place infinitely slowly) and are more energy efficient because they don't create any entropy. Shock compression means "compress it really fast really hard" (like with explosives).

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Unstart beat me to it; shock compression creates buttloads of entropy, which is part of why wave drag is such a bitch.

 

So, I have this idea that part of the reason shaped charges got way better during the Cold War is that a bunch of money and energy had been dumped into studying the rheological acceleration of metals by explosives.  'Cause reasons.

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Oooh man. Here we go again. Ok so I'm a nuclear engineer (specializing in advanced reactor design). Thorium nuclear fuel is really cool for a lot of reasons. But there are a lot of clarifications I like to make when discussions about this stuff come up. I find that the Thorium Evangelical Internet Community spreads a lot of questionable information while advertising their fuel. I get it... they're trying to rebrand nuclear energy to get away from the negative implications. Maybe they're right to. But in my opinion, nuclear energy is what's awesome and Thorium is but one of many options that we have that are totally sweet.

The thing I want you all to know is that there are literally thousands of nuclear reactor design options based on different combinations of coolant (water, gas, sodium, salt, CO2, lead, etc.), fuel form (uranium oxide, uranium metal, thorium oxide, thorium metal, thorium nitride, TRISO, pebble bed, aqueous, molten salt, etc. etc.), power level (small modular, large, medium), and about a dozen other parameters. We really only have 1 kind in commercial operation (uranium oxide fueled, pressurized water cooled reactors) and it has a lot of disadvantages over some of the other possibilities.

Among all these options, there are a whole bunch of combinations that give performance far superior to the traditional reactors in terms of cost, safety, proliferation, waste, and sustainability. Thorium-based ideas are among them, but Thorium isn't some new thing held back by conspiracy.

The key advantage of Thorium over all other things is that it uniquely allows you to make a breeder reactor in a thermal neutron spectrum. This advantage is subtle and fairly minor compared to the advantages that it shares with uranium fuel in advanced reactors. Anyway, this video brings up two of the clarifications I like to mention:

Clarification 1: Lots of reactor concepts operate at low coolant pressure and can be passively safe The first part of this video discusses why high pressure coolant is a problem in decay heat removal. This is true! But, there's nothing Thorium-specific about the ability to operate with low-pressure coolant. That's a function of which coolant you choose (not fuel).

For instance, sodium-cooled fast reactors operate at low pressure and the sodium-cooled EBR-II reactor in Idaho was the first and only reactor to demonstrate the ability to survive unprotected transients (meaning the control rods didn't even go in!!) This is incredible safety and is great.

Other reactors that can do passive decay heat removal include: Salt-cooled, solid fueled reactors like the FHR Lead-cooled reactors Lots of other Molten Salt Reactors, including Uranium-fueled ones (The Thorium-fueled MSR is just one kind of MSR).

Clarification 2: FYI, there are also non-Thorium breeder reactors Kirk says this at 2:51: "We could use thorium about 200 more efficiently than we're using uranium now"Ugh. This statement is technically accurate. But it's totally misleading in this context. Any breeder reactor can get ~200x more energy out of its fuel, whether it's Uranium-Plutonium in a fast breeder reactor or Thorium-Uranium in a thermal molten salt reactor (MSR). So nuclear power is awesome! In the USA, the Dept. of Energy spent like infinity money trying to commercialize a uranium-plutonium breeder reactor that eventually got canceled. Using any kind of breeder reactors, we will not be running out of Uranium or Thorium any time soon.

I've argued these points and others a bunch of times. I've even published a Thorium Myths page on my webpage. I even made
when one guy and myself argued 90 comments deep into a thread. I think I did fairly well but if you want to check it out here's the link to that thread and the subredditdrama discussion about it. I just really wish these folks would promote advanced nuclear in general instead of just focusing on one aspect of it. Maybe I'm just complaining about a reality of marketing.

EDIT: expanded acronyms

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A bit more from that guy:

 

Ok so I'm a nuclear engineer (specializing in advanced reactor design). Thorium nuclear fuel is really cool for a lot of reasons. But there are a lot of clarifications I like to make when discussions about this stuff come up. I find that the Thorium Evangelical Internet Community spreads a lot of questionable information while advertising their fuel. I get it... they're trying to rebrand nuclear energy to get away from the negative implications. Maybe they're right to. But in my opinion, nuclear energy is what's awesome and Thorium is but one of many options that we have that are totally sweet.

The thing I want you all to know is that there are literally thousands of nuclear reactor design options based on different combinations of coolant (water, gas, sodium, salt, CO2, lead, etc.), fuel form (uranium oxide, uranium metal, thorium oxide, thorium metal, thorium nitride, TRISO, pebble bed, aqueous, molten salt, etc. etc.), power level (small modular, large, medium), and about a dozen other parameters. We really only have 1 kind in commercial operation (uranium oxide fueled, pressurized water cooled reactors) and it has a lot of disadvantages over some of the other possibilities. Among all these options, there are a whole bunch of combinations that give performance far superior to the traditional reactors in terms of cost, safety, proliferation, waste, and sustainability. Thorium-based ideas are among them, but Thorium isn't some new thing held back by conspiracy.

The key advantage of Thorium over all other things is that it uniquely allows you to make a breeder reactor in a thermal neutron spectrum. This advantage is subtle and fairly minor compared to the advantages that it shares with uranium fuel in advanced reactors.

Anyway, this video brings up two of the clarifications I like to mention:

Clarification 1: Lots of reactor concepts operate at low coolant pressure and can be passively safe

The first part of this video discusses why high pressure coolant is a problem in decay heat removal. This is true! But, there's nothing Thorium-specific about the ability to operate with low-pressure coolant. That's a function of which coolant you choose (not fuel). For instance, sodium-cooled fast reactors operate at low pressure and the sodium-cooled EBR-II reactor in Idaho was the first and only reactor to demonstrate the ability to survive unprotected transients (meaning the control rods didn't even go in!!) This is incredible safety and is great. Other reactors that can do passive decay heat removal include:

  • Salt-cooled, solid fueled reactors like the FHR
  • Lead-cooled reactors
  • Lots of other Molten Salt Reactors, including Uranium-fueled ones (The Thorium-fueled MSR is just one kind of MSR).

Clarification 2: FYI, there are also non-Thorium breeder reactors

Kirk says this at 2:51:

"We could use thorium about 200 more efficiently than we're using uranium now"

Ugh. This statement is technically accurate. But it's totally misleading in this context. Any breeder reactor can get ~200x more energy out of its fuel, whether it's Uranium-Plutonium in a fast breeder reactor or Thorium-Uranium in a thermal molten salt reactor (MSR). So nuclear power is awesome! In the USA, the Dept. of Energy spent like infinity money trying to commercialize a uranium-plutonium breeder reactor that eventually got canceled.

Using any kind of breeder reactors, we will not be running out of Uranium or Thorium any time soon.

I've argued these points and others a bunch of times. I've even published a Thorium Myths page on my webpage. I even made /r/subredditdrama when one guy and myself argued 90 comments deep into a thread. I think I did fairly well but if you want to check it out here's the link to that thread and the subredditdrama discussion about it.

I just really wish these folks would promote advanced nuclear in general instead of just focusing on one aspect of it. Maybe I'm just complaining about a reality of marketing.

 

His Website please add to the list of websites.

 

Awesome page on Thorium.

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Eta curves for various fissile actinides:

 

6w8q7Sy.jpg

 

 

Edit:  Right, forgot.  For those of you who aren't Unstart, eta (η) is the neutron multiplication factor of the fissile fuel.  This is the number of neutrons produced per neutron absorbed by fuel elements.  If η > 2, fuel breeding is possible.  However, to exceed certain parasitic losses of neutrons and to get the breeding done this century, η should ideally be quite a bit higher than 2.

 

As can be seen, for the thermal neutron energy range (.025 eV or so), η for U-233 is favorably high.

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