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Ore_Ele
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7/19/2011 12:56:46 PM
Posted: 5 years ago
A thread to talk about and ask question about... Pink Flamingo Soup. No, actually about nuclear power as an energy source. Personally, I've always leaned towards the PBR styles, but just recently, I've been growing fond TWR.
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Ore_Ele
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7/19/2011 12:59:06 PM
Posted: 5 years ago
For those not familiar with TWR (Traveling Wave Reactors), this is a good, relatively short, read.

http://www.technologyreview.com...

For PBR (Pebble Bed Reactors), wiki is pretty good.

http://en.wikipedia.org...
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Ore_Ele
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7/22/2011 4:03:27 PM
Posted: 5 years ago
At 7/22/2011 3:42:28 PM, Rockylightning wrote:
I'm not clear on whether we use plutonium, or uranium or hydrogen. (H-Bombs?) Or all of them?

For powerplants we only use Uranium (since we don't use breeders, we don't use plutonium).

Hydrogen is used in fusion (rather than breaking apart really large atoms, we are combining small atoms). That has not been perfected as a power source yet. Though test reactors are being made, and we'll have some non-commerical research reactors up in 2020. Actual power plants that produce large scale energy will not likely come until 2050 - 2080 (pending on how quickly we move forward).

The way a reactor currently works is...

1) We dig Uranium out of the ground. It is naturally 99.3% U238 and 0.7% U235.

2) Using centerfuges, we can collect the U235 (the kind that is used in powerplants and the bombs) and discard the U238.

3) The US only uses slow neutron reactors (called thermal reactors). When U235 is struck by a free neutron, it breaks in half, giving off two smaller atoms (nuclear waste), a ton of energy, and several more free neutrons to continue hitting other U235 atoms.

Now, we don't use pure U235, because the reaction would quickly grow out of control, so we mix it with some of the U238, which basically waters it down into a managable rate (usually around 10% or 15% U235).

Thermal reactors use the slow neutrons becauses they are better at breaking the U235 atoms. My old teacher told me that this is much like throwing a baseball at a glass window. A nice throw will shatter all the glass, but a really really fast throw will just puncture a hole through the window without breaking the entire thing (now holes are not being punched through the atom while it stays intact, but it works to demonstrat that fast moving things may be less effective at breaking their targets).

The U238 that is in the mix will sometimes catch a free neutron. Rather than breaking apart (because it is not fissile, on fissile material will break apart) it will turn into U239, which quickly decays into Pu239 (hello Plutonium). Slow moving neutrons are not very good at being absorbed, while fast moving are, but some is still converted.

4) When most of the U235 is spent, we remove the spent fuel rods. This rods are often full of the fissile material (the broken atoms, which form I131 or Cs135 or various others, which are all bad for health) some left over U238, and some Pu239 which formed.

5) Most places (not the US) take this waste and reprocess it. That means that they extract the left over U238 and Pu239 (and any U235 that was left) so that it can be re-used. This presents an issue, because you never know if the Pu239 is being pulled to be re-used (it can be used just fine by reactors) for the reactor, or pulled out to be turned into a bomb.

The US decided (back under Carter, I believe) that we would not reprocess, hoping that everyone would follow our example so that there would be no Pu239 out there in isolated forms (which make bad bad bombs). I don't believe that a single nation followed our lead (yet we still do it).
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Ore_Ele
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7/22/2011 4:06:58 PM
Posted: 5 years ago
The other type of reactor is the fast neutron reactor (just called fast neutron reactor, not sure why we gave one a special name, but not the other). The disadvantage is that fast neutrons are not as good at breaking the U235, so you need a higher concentration (about 20% U235), but the major plus is that they convert the U238 (which makes up about 80% of the fuel) into Pu239, and use that Pu239 while it is in the reactor, so they use their feul more completely.

Because they use faster neutrons, they are often more expensive, and require more safety standards (since their temp can grow faster into the danger zone).
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DirkBergurk
Posts: 32
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7/22/2011 9:48:54 PM
Posted: 5 years ago
At 7/19/2011 12:59:06 PM, Ore_Ele wrote:
For those not familiar with TWR (Traveling Wave Reactors), this is a good, relatively short, read.

http://www.technologyreview.com...

For PBR (Pebble Bed Reactors), wiki is pretty good.

http://en.wikipedia.org...

Very cool. I have never heard of a TWR before. I especially like the idea of never refueling, and I can only imagine utilities would love it more. Looks as if it is a fast reactor, so it will undoubtedly suffer the same obstacles as other fast reactors. I have never been fond of liquid sodium as a coolant particularly but it has its advantages. I think the quote, "theoretically could run for a couple of hundred years", is a bit misleading as it would never come close to running that long being limited by the materials of the vessel and likely other things. Hence theoretically, but still...

I have only recently looked into PBRs, and I am particularly intrigued by these designs (although they have obviously been around for some time). The strong passive safety feature would be an exceptional plus in today's climate after Fukushima, and they have the capability use a thorium cycle. I figure the biggest obstacle to PBRs is the fuel. Fortunately, the Very High Temperature Reactor (VHTR) group has been pushing long and hard for TRISO fuel for some time to be licesned by the NRC. So maybe, just maybe, we could see a pilot PBR in the US someday if it gets licensed.
DirkBergurk
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7/22/2011 9:55:54 PM
Posted: 5 years ago
At 7/22/2011 4:03:27 PM, Ore_Ele wrote:
For powerplants we only use Uranium (since we don't use breeders, we don't use plutonium).


I think it is worth mentioning that while the fuel in reactors starts as Uranium, in all reactors Pu is created in some amounts (in the manner you described later). In fact, by the time a typical LWR in the US reaches time for refueling, roughly 1/3 to 1/2 of its energy output is created by the fissioning of Pu. Also interesting to note that this is where the plutonium came from for the first nuclear weapons detonation.

Now, we don't use pure U235, because the reaction would quickly grow out of control, so we mix it with some of the U238, which basically waters it down into a managable rate (usually around 10% or 15% U235).


Typical U-235 enrichments usually don't exceed 5% for US reactors. In nuclear submarines, the enrichment can be as high as 90%.

5) Most places (not the US) take this waste and reprocess it. That means that they extract the left over U238 and Pu239 (and any U235 that was left) so that it can be re-used. This presents an issue, because you never know if the Pu239 is being pulled to be re-used (it can be used just fine by reactors) for the reactor, or pulled out to be turned into a bomb.


I believe there are a lot of alternatives and modifications to the PUREX (the stragety described above) reprocessing strategy that could be emplyed. Ones that would not separate the plutonium by itself. My personal favorite is UREX+, but there are others. I just wish the US would pursue them.

The US decided (back under Carter, I believe) that we would not reprocess, hoping that everyone would follow our example so that there would be no Pu239 out there in isolated forms (which make bad bad bombs). I don't believe that a single nation followed our lead (yet we still do it).

You are indeed correct that Carter issued a permanent ban on reprocessing (on bad advice in my opinion). However, Reagan lifted that ban in 1981. Unfortunately, there is such a stigma these days associated with reprocessing, nobody is willing to invest in it.

Very nice introductory explanation by the way.
Ore_Ele
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7/25/2011 11:25:06 AM
Posted: 5 years ago
At 7/22/2011 9:37:41 PM, Rockylightning wrote:
You made it pretty easy to understand.

Do you work in nuclear energy?

No I do not. I just study it like there is no tomorrow (actually, it is just out of personal interest, energy sources in general).
"Wanting Red Rhino Pill to have gender"
Ore_Ele
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7/25/2011 11:31:56 AM
Posted: 5 years ago
At 7/22/2011 9:48:54 PM, DirkBergurk wrote:
At 7/19/2011 12:59:06 PM, Ore_Ele wrote:
For those not familiar with TWR (Traveling Wave Reactors), this is a good, relatively short, read.

http://www.technologyreview.com...

For PBR (Pebble Bed Reactors), wiki is pretty good.

http://en.wikipedia.org...

Very cool. I have never heard of a TWR before. I especially like the idea of never refueling, and I can only imagine utilities would love it more. Looks as if it is a fast reactor, so it will undoubtedly suffer the same obstacles as other fast reactors. I have never been fond of liquid sodium as a coolant particularly but it has its advantages. I think the quote, "theoretically could run for a couple of hundred years", is a bit misleading as it would never come close to running that long being limited by the materials of the vessel and likely other things. Hence theoretically, but still...

Yes, they could design the fuel to not need to be refilled for a few hundred years, but the rest of the building would need to be. They would likely designed it to last maybe 10 - 15 years to start, then slowly get longer as they get better at building long last buildings.

And yes, they are all fast reactors for the breeding effect.


I have only recently looked into PBRs, and I am particularly intrigued by these designs (although they have obviously been around for some time). The strong passive safety feature would be an exceptional plus in today's climate after Fukushima, and they have the capability use a thorium cycle. I figure the biggest obstacle to PBRs is the fuel. Fortunately, the Very High Temperature Reactor (VHTR) group has been pushing long and hard for TRISO fuel for some time to be licesned by the NRC. So maybe, just maybe, we could see a pilot PBR in the US someday if it gets licensed.

Yes, the early PBRs had issues with the granite covering rubbing against each other while in the reactor, creating granite dust, which is very dangerous. They now coat them with a layer of silicon, so that there is no rubbing friction and dust being created. A live and learn development.

Sadly, PBRs have a bit of a bad rap as being difficult to maintain heat levels, since the pebbles are always moving, it is possible for them to develop pockets where it gets really really hot, and when they move, that pocket gets released. This was caused because at the time, they would be tossed into a pile with a small exit hole in the bottom. This is not really good, since there is no control to make sure that they leave the reactor in proper order. Now they do columns, where each one follows another directly, so there can be no stalling, no pockets, no getting out of order.
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Ore_Ele
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7/25/2011 11:41:19 AM
Posted: 5 years ago
At 7/22/2011 9:55:54 PM, DirkBergurk wrote:
At 7/22/2011 4:03:27 PM, Ore_Ele wrote:
For powerplants we only use Uranium (since we don't use breeders, we don't use plutonium).


I think it is worth mentioning that while the fuel in reactors starts as Uranium, in all reactors Pu is created in some amounts (in the manner you described later). In fact, by the time a typical LWR in the US reaches time for refueling, roughly 1/3 to 1/2 of its energy output is created by the fissioning of Pu. Also interesting to note that this is where the plutonium came from for the first nuclear weapons detonation.

That is true, while all reactors convert some degree of their U238 into the Pu239, the fast reactors do it more efficiently and with more intent on doing so.


Now, we don't use pure U235, because the reaction would quickly grow out of control, so we mix it with some of the U238, which basically waters it down into a managable rate (usually around 10% or 15% U235).


Typical U-235 enrichments usually don't exceed 5% for US reactors. In nuclear submarines, the enrichment can be as high as 90%.

5) Most places (not the US) take this waste and reprocess it. That means that they extract the left over U238 and Pu239 (and any U235 that was left) so that it can be re-used. This presents an issue, because you never know if the Pu239 is being pulled to be re-used (it can be used just fine by reactors) for the reactor, or pulled out to be turned into a bomb.


I believe there are a lot of alternatives and modifications to the PUREX (the stragety described above) reprocessing strategy that could be emplyed. Ones that would not separate the plutonium by itself. My personal favorite is UREX+, but there are others. I just wish the US would pursue them.

The US decided (back under Carter, I believe) that we would not reprocess, hoping that everyone would follow our example so that there would be no Pu239 out there in isolated forms (which make bad bad bombs). I don't believe that a single nation followed our lead (yet we still do it).

You are indeed correct that Carter issued a permanent ban on reprocessing (on bad advice in my opinion). However, Reagan lifted that ban in 1981. Unfortunately, there is such a stigma these days associated with reprocessing, nobody is willing to invest in it.

That is true that Reagan lifted the ban, but no one has started one up since (though one did start construction in 2005, fingers crossed).


Very nice introductory explanation by the way.

Thank you,
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Rockylightning
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7/26/2011 1:14:53 AM
Posted: 5 years ago
At 7/25/2011 11:25:06 AM, Ore_Ele wrote:
At 7/22/2011 9:37:41 PM, Rockylightning wrote:
You made it pretty easy to understand.

Do you work in nuclear energy?

No I do not. I just study it like there is no tomorrow (actually, it is just out of personal interest, energy sources in general).

If this is so I would recommend the movie "Countdown to Zero". Although it has a clear agenda, (not necessarily a bad thing) it outlines a lot of cool stuff dealing with the process of enriching Uranium. Turns out its why I knew what a centrifuge was and what state Uranium is purified at.
DirkBergurk
Posts: 32
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7/26/2011 9:50:14 AM
Posted: 5 years ago
At 7/25/2011 11:31:56 AM, Ore_Ele wrote:
At 7/22/2011 9:48:54 PM, DirkBergurk wrote:
Very cool. I have never heard of a TWR before. I especially like the idea of never refueling, and I can only imagine utilities would love it more. Looks as if it is a fast reactor, so it will undoubtedly suffer the same obstacles as other fast reactors. I have never been fond of liquid sodium as a coolant particularly but it has its advantages. I think the quote, "theoretically could run for a couple of hundred years", is a bit misleading as it would never come close to running that long being limited by the materials of the vessel and likely other things. Hence theoretically, but still...

Yes, they could design the fuel to not need to be refilled for a few hundred years, but the rest of the building would need to be. They would likely designed it to last maybe 10 - 15 years to start, then slowly get longer as they get better at building long last buildings.


Yes, that would be a much more realistic approach. As I mentioned earlier, materials would be the limiting factor in its lifetime because of the high neutron fluences the vessel would experience. Even on the thermal reactors in the US, one of the biggest factors in determining whether to extend the license of a reactor is the condition of the vessel as a result of the neutrons. With the fast spectrum of the TWR, it would certainly be of concern when thinking about such long lifetimes. I do believe one of national labs in the US has a experiment that is capable of determining the effect of fast neutron fluences over an extended period of time on materials, but the lab's name escapes me. There is a great need for more research on materials in this country (especially in the fusion field), but unfortunately it seems materials research is sexy enough to attract as much funding as other fields.

And yes, they are all fast reactors for the breeding effect.

Keep in mind that it is possible to breed in the thermal spectrum as well.

I think another interesting type of reactor is the SMR (small modular reactor). Although they are typically a standard design (i.e. LWR), they are more realistic for a power company to build since the cost of a single plant is not so expensive. Furthermore, a utility can customize the number of reactors it wants on site to meet the demands of that area. It also seems that Secretary Chu is behind the idea of pursing licenses of these types of reactors.

http://en.wikipedia.org...
DirkBergurk
Posts: 32
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7/26/2011 9:53:05 AM
Posted: 5 years ago
At 7/25/2011 11:25:06 AM, Ore_Ele wrote:
At 7/22/2011 9:37:41 PM, Rockylightning wrote:
You made it pretty easy to understand.

Do you work in nuclear energy?

No I do not. I just study it like there is no tomorrow (actually, it is just out of personal interest, energy sources in general).

I applaud you. Finding technical information on nuclear energy online is more difficult than a lot of other subjects.
Ore_Ele
Posts: 25,980
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7/26/2011 10:45:52 AM
Posted: 5 years ago
At 7/26/2011 9:53:05 AM, DirkBergurk wrote:
At 7/25/2011 11:25:06 AM, Ore_Ele wrote:
At 7/22/2011 9:37:41 PM, Rockylightning wrote:
You made it pretty easy to understand.

Do you work in nuclear energy?

No I do not. I just study it like there is no tomorrow (actually, it is just out of personal interest, energy sources in general).

I applaud you. Finding technical information on nuclear energy online is more difficult than a lot of other subjects.

Really? I find that nuclear energy information to be very well documented, though quite often the modern sources agenda driven (either www.nuclear_is_freedom.gagmewithaspoon or www.nuclear_rapes_the_homeless.IthinkImgonnahurl). But the engineering and the physics of it is well documented and mostly free of all that, and even in those, there is information if you know how to filter the agenda.
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Ore_Ele
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7/26/2011 10:46:19 AM
Posted: 5 years ago
Though that could be because I've looked into it a lot, and so know how to find what I'm looking for.
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DirkBergurk
Posts: 32
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7/26/2011 5:40:05 PM
Posted: 5 years ago
At 7/26/2011 9:50:14 AM, DirkBergurk wrote:
I do believe one of national labs in the US has a experiment that is capable of determining the effect of fast neutron fluences over an extended period of time on materials, but the lab's name escapes me.

I guess I was referring to the HFIR, but it seems it is operated for neutrons in the thermal spectrum. Surely there has to be something for fast neutron research.

http://neutrons.ornl.gov...
RoyLatham
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7/27/2011 5:20:55 PM
Posted: 5 years ago
A couple of things.

While Reagan lifted the ban on reprocessing, no commercial entity is going to take the political risk of investing in a plant that the government might shut down at any time. Keep in mind the Shoreham nuclear plant built by Long Island Lighting at a cost of billions and forced to close right before it started to operate. Getting a rational nuclear energy policy depends entirely on a major change the political climate. Voting against nuclear power is one of the test issues used to identify "progressives."

Nuclear weapons can be made of either uranium or plutonium, so the notion that restricting plutonium would have an effect is an odd one. North Korea claims to have both uranium and plutonium nukes. The idea that if the US doesn't recycle nuclear fuel that North Korea, Iran, or anyone else would be deterred is without a trace of logic.

Currently there are abut 40 countries that have technical capability to make nuclear weapons. The ones that want them are going ahead, first India and Pakistan, now North Korea and Iran, those who don't rely on the US nuclear umbrella. As soon as Iran demonstrates nuclear weapons, it is likely that Saudi Arabia and others will also develop them.

With fast breeder reactors, nuclear fuel supplies are stretched from about a 50 year supply to about 3000 years. Nuclear fuel is a relatively minor cost of nuclear power, so a significant increase in fuel price would have little effect on the price of electricity. the cost of coal about a third of the cost of generating electricity. For nuclear, fuel is about 3%. Capital costs dominate both. Disposing of the nuclear waste is a much larger cost (about 15%), but that isn't changed by the original fuel cost.
DirkBergurk
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7/27/2011 7:21:39 PM
Posted: 5 years ago
At 7/27/2011 5:20:55 PM, RoyLatham wrote:

Nuclear weapons can be made of either uranium or plutonium, so the notion that restricting plutonium would have an effect is an odd one.

I disagree. While the spent fuel that comes out of a nuclear reactor contains both uranium and plutonium, the uranium would need to be enriched to be used to build a bomb (which requires enormous infrastructure). However, a plutonium bomb can be built without any type of enrichment by using an implosion device. Thus, with some plutonium and an expert in explosives, a nuclear bomb could easily be built without large infrastructure. It is key to point out that the big concern from nuclear proliferation comes not from nation states but from terrorists.

North Korea claims to have both uranium and plutonium nukes.

While they may have claimed it, I seriously doubt North Korea has uranium nukes. From what I have read, the earlier stated theories that North Korea has the enrichment capabilities to build a uranium bomb were overplayed. The reactor they used to generate the plutonium to build their first bomb didn't even use enriched uranium from what I understand.

The idea that if the US doesn't recycle nuclear fuel that North Korea, Iran, or anyone else would be deterred is without a trace of logic.

As I described above, the concern is somebody getting their hands on plutonium because a bomb can easily be manufactured from that. Again, uranium not so much because it requires huge infrastructure to enrich it to the point of building a bomb. PUREX, the most commonly used form of reprocessing, separates plutonium by itself! If that was acquired by terrorists (however unlikely), the result could be disastrous.

That said, I am for nuclear reprocessing. We just need to do it responsibly.