Thorium power, how is it going in the US?

[ehj666]

I know what Carnot efficiency is an that only applies to thermal processes. A antenna is not.


I guess you could do a tongue in cheek estimation with the color temperature of the sunlight (6500K) and the temperature of the solar cell lets say 300K for gods sake. Now you do the math...

The nantenna efficiency is both theoretical and specious in its calculation. See:
http://en.wikipedia.org/wiki/Nantenna#Advantages_of_nantennas

R. L. Bailey claims that nantennas are not limited by Carnot efficiency, whereas photovoltaics are. However, he does not provide any argument for this claim. Furthermore, when the same assumptions used to obtain the 85% theoretical efficiency for nantennas are applied to single junction solar cells, the theoretical efficiency of single junction solar cells is also greater than 85%.

However the efficiency of energy conversion is not the problem, the problem is the energy density one starts with. That amount is a maximum of about 100 watts per square foot. No matter what you do with it, you will not get any more due to an even more basic law of thermodynamics, conservation of energy, otherwise known as the no free lunch law.

Averaged out to 24 hours per day, 365 days per year actual yield would be no better than 25 watts per sq. ft. Cloud cover knocks it down even more. Every time its form is changed conversion inefficiencies knock it down still more.

In the end it will be energy density and convenience which determine the winners and losers, and solar in most cases performs poorly by both measures.

[ElectricMucus]

I dare you of actually doing the math of your electrical energy consumption vs the amount of energy actually received for a full stack of solar panels.

You won't be able to run a large bitcoin mining operation or grow lots of pot but it will let you drive things like lights, your pc, tv. hifi. dishwasher, washing machine and even a AC if your house is insulated enough.
All that for effective zero space requirement. Or do you have a rooftop garden or something.

Granted not everybody lives in an owned home may people live in apartments that's why we still need other forms of generating electricity. But claiming that you can't power a house with rooftop solar is nonsense. The reason this is so ridiculous is that the sun is earths sole power source.

[TheBitcoinChemist]

Meh. I'm still holding out for Andrea Rossi and his LENR progress in those "e-cat" modules.

Even if Thorium gains popularity as a fuel in fission reactors, you still have to deal with actinide wastes, induced radioactivity from hard gamma rays, and all those other difficulties. And it's not even fissionable by itself anyway, so you still need uranium or plutonium as a source of neutrons. It's no panacea by any stretch of the imagination.

Gamma rays do not 'induce' radioactivity, only neutron capture does that.  And no, you don't need uranium or plutonium.  One can make a primary neutron source with a spalation excelerator, such as in an energy amp reactor design; or from an Alpha emitter and a sheet of aluminum, as the 'nuclear boy scout' did in the 90's.

[TheBitcoinChemist]

Thorium might solve some issues, but its also less economical and it doesn't exist yet :s

Where do you guys come up with this stuff?  Thorium fuel cycles are much more economical than a uranium fuel cycle, the only advantage that uranium had in the start was the desire of the DOD to create weapons fuel, and now because all of the nuclear industry is setup to process and handle uranium.  And yes, the tech has been known for decades, so it does "exist" even if it's not used.

[justusranvier]

you still have to deal with actinide wastes

If you'd take the time to browse the Wikipedia page on LFTR you might discover that some of your assumptions about it may not be accurate.

[TheBitcoinChemist]

I have no problem with any of the arguments of why thorium reactors would be better than uranium ones. Including that they can be safer.

I even recognize that they could be built self regulating. (But again see my ramblings about Carnot efficiency of why this is not practical for steam generating designs)

I just maintain that the claim that they can not melt down because the reaction itself is temperature limited is bullshit.

Well, I heard about a German reactor design a while ago where small pieces of fuel are housed inside tough graphite "rocks" that are then stacked like apples inside a large gas chamber. Gas gets heated as it passes between the rocks and it then powers the usual heat-exchanger set-up. The idea was that it's self-regulating and would sit at a stable temperature even if no gas was passing through.

Yes, that's a pebble bed reactor.  But his complaint about generation of consumer electricity is valid, the goal of making a inherently safe pebble bed core and one of efficiently producing power are at odds with each other.  However, a pebble bed style reactor, with each pebble encased into steel & corrosion resistant casings, would be ideal for lower level process heating or centralized apartment block heating.  Israel could make the desert bloom with a pebble bed reactor intended to de-salinate & pump seawater.  Russia & Canada could diverte many tons of natural gas and heat oil to other productive uses, even power generation.  This is the primary design use of the CANDU reactors that I mentioned, and the USSR had been using smaller (and notablely safer) reactors as downtown municipal heating systems in many of their more northern cities for a long time.

[TheBitcoinChemist]

you still have to deal with actinide wastes

If you'd take the time to browse the Wikipedia page on LFTR you might discover that some of your assumptions about it may not be accurate.

Correct, the greater issue with the spent fuel in uranium fueled civilian reactors is that the fuel isn't permitted to be concetrated greater than 20%, and the reactions are unsustainable once U235 drops below 3-5% depending upon the reactor design.  The rest of the core is mostly U238, and some is transmutted into plutonium.  It's the plutonium that has the long & hot half life, not the actinide wastes, and a thorium reactor doesn't produce plutonium.  A thorium reactor does produce U233, but it's 'burned' in the normal running process of the reactor so there is never much buildup there.  Also, since nearly 100% of the core is breedable fuel, a given core can stay in the reactor for much longer.  Therefore, not only are the actinide hazards reduced simply because of the time they spend safely sequestered in the reactor itself (and their much shorter half lives) but they also tend to be reduced due to ongoing neutron capture transmuttation.

[justusranvier]

and a thorium reactor doesn't produce plutonium.

That's not exactly true. There will be some plutonium produced but it won't accumulate in large quantities.

Everything the online reprocessing doesn't remove stays in the fuel salt until it either fissions, decays or get transmuted into something that either fissions or decays. Transuranics will be present in small quantities but once the removal rate matches the production rate they will stay at that equilibrium concentration until the reactor is shut down. Presumably the fuel salt would be reused in the replacement reactor so there is never a need to put transuranics in long term storage.

[TheBitcoinChemist]

and a thorium reactor doesn't produce plutonium.

That's not exactly true. There will be some plutonium produced but it won't accumulate in large quantities.

Everything the online reprocessing doesn't remove stays in the fuel salt until it either fissions, decays or get transmuted into something that either fissions or decays. Transuranics will be present in small quantities but once the removal rate matches the production rate they will stay at that equilibrium concentration until the reactor is shut down. Presumably the fuel salt would be reused in the replacement reactor so there is never a need to put transuranics in long term storage.

Oh, I see.  You're talking about a molten salt reactor.  While I agree that a 'meltdown' is meaningless in this context, I'm not sure that I would agree that a molten salt reactor is a good idea.  Deliberately keeping a neutron emmittor in a liquid state is just asking for problems, in my opinion.

[myrkul]

Deliberately keeping a neutron emitter in a liquid state is just asking for problems, in my opinion.

Granted, I'm not a nuclear engineer, but I have it on good authority that it actually solves several problems.

vv like those vv

[justusranvier]

Deliberately keeping a neutron emmittor in a liquid state is just asking for problems, in my opinion.

Right, because surrounding the neutron emitters by flammable metals and a convienient source of hydrogen gas is a much better idea than storing it in chemically and radiologically stable salts.

[Realpra]

Where do you guys come up with this stuff?  Thorium fuel cycles are much more economical than a uranium fuel cycle, the only advantage that uranium had in the start was the desire of the DOD to create weapons fuel, and now because all of the nuclear industry is setup to process and handle uranium.  And yes, the tech has been known for decades, so it does "exist" even if it's not used.

I was told that.

So clarify for me:
1. Thorium reactors could be built TODAY using the old 50ies blueprints (no research needed).
2. These thorium reactors would generate MORE J/$ compared to uranium reactors.

Yes?

See otherwise wind turbines already fulfill both of these requirements - competitive with coal, no radioactive waste, killing fewer birds than our windows and doesn't take up farm land like solar.

During the Fukushima meltdown only one wind turbine out of ALL the thousands they had fell down - hurting absolutely no one.

Maybe its because you are american and GE has been blocking progress with stolen patents over there, but a real wind turbine is huge, advanced and effective.

[myrkul]

Maybe its because you are american and GE has been blocking progress with stolen patents over there, but a real wind turbine is huge, advanced and effective.

... at slicing birds to bits while applying a braking force to the earth. Also really poor at generating power where there are chaotic winds, such as inside the city, where power generation is most efficient, because that's where it's needed.

Tiny little thorium reactor in your back yard, powers the whole building.

[ElectricMucus]

Were you guys exposed to 50s futurist brochures or something? 

Maybe its because you are american and GE has been blocking progress with stolen patents over there, but a real wind turbine is huge, advanced and effective.

... at slicing birds to bits while applying a braking force to the earth. Also really poor at generating power where there are chaotic winds, such as inside the city, where power generation is most efficient, because that's where it's needed.

Tiny little thorium reactor in your back yard, powers the whole building.

Hello is this HomeThorium support? yes!

During this nights storm my Plum-tree fell over and hit my power module. After I let my dog out this morning it came back with the eyes bleeding!!!
Is the neutron source exposed? What do you mean that can't happen? No I won't leave the house....
You gonna help me!!!

[myrkul]

Hello is this HomeThorium support? yes!

During this nights storm my Plum-tree fell over and hit my power module. After I let my dog out this morning it came back with the eyes bleeding!!!
Is the neutron source exposed? What do you mean that can't happen? No I won't leave the house....
You gonna help me!!!

You understand that thorium is safe to hold in your hand, right? An accident such as you describe will be quite dangerous... for a few hours, while the fast stuff burns off, but then will be relatively easy to clean up. Imagine a similar situation with a traditional nuclear plant. Dude wouldn't be there to make the phone call, nor would his neighbors, or theirs...

[myrkul]

It's not the thorium, or the uranium that poses any kind of danger in nuclear reactors. It's all the other crap that gets created from fission and decay. The older the fuel, the more hazardous it gets. And the plum tree would have to get past metres of concrete and lead shielding, even if the reactor is the size of a spraycan.

Do a little reading on the thorium fuel cycle. Most of that "other stuff" that gets created is gone quick. Don't get me wrong, while it's there, it's hideously dangerous, but because of that, it's gone quickly. Perhaps hours was hyperbole, but so was the plum tree. In even a tiny reactor, there's going to (need to) be significant amounts of shielding. Plum tree wouldn't do jack but crack the plastic cover. But in the event that (something) does crack the shielding, I'd rather it be a LFTR than a BWR. A radioactive puddle of goo that quickly solidifies is much easier to handle than a (formerly highly pressurized) radioactive cloud of steam. (and let's not forget all that hydrogen)

[ElectricMucus]

Well my point is i don't think it's wise to have lots of tiny reactors everywhere. There is just so much that can go wrong and no matter what eventually some accident will happen when they are cracked open.
Yes eventually thorium reactors could be as safe as batteries but it will be a long time till that happens, and somehow I doubt it.

And lets say that does happen what after a decade? What to do with em? They gonna be everywhere some of them will end up in a landfill and don't tell me that won't rise the average dosage of ionizing radiation and inhaled active particles.

[myrkul]

And lets say that does happen what after a decade? What to do with em? They gonna be everywhere some of them will end up in a landfill and don't tell me that won't rise the average dosage of ionizing radiation and inhaled active particles.

Like this?: http://news.nationalgeographic.com/news/2010/07/photogalleries/100708-radioactive-nuclear-waste-science-salt-mine-dump-pictures-asse-ii-germany/

Yeah, no. Look up what the thorium fuel cycle's end states are.

The thorium cycle could use the stuff in that mine (well, most of it) as fuel.

[ElectricMucus]

I think I haven't made that clear enough: With nuclear power in hands of the general public there will be some people who do not obey the necessary steps to implement clean waste disposal.

The scenario we are talking about are reactors small enough you can carry around, like the size of a coffee machine with the corresponding additional machinery in the range of a refrigerator to a shipping container. While that would be very cool in terms of decentralized power it will also mean that there are new kinds of environmental threats associated with it.
The critique is not about the principal versatility of such a system but of how the current society would deal with it.

Even with very rigorous fines some people would still dispose their spent reactor in the woods, some lake, etc... And that can have dire consequences.
I realize that such a reactor would have less impact that lets say a spent fuel rod, you don't see those in the hands of people with complete disregard of consequences.

[mobodick]

You have no idea of what you are talking about. There is simply no need for higher energy density than the sun already provides. The amount of energy received on the roof of the typical family home is enough to power it. And yes they will become almost 100% efficient. Lookup nantennas and weep.

The energy density of the sun is irrelevant, what matters is how much of it reaches the Earth's surface. The day time peak is roughly 1000
watts per square meter at the average latitude of the US, or approximately 100 watts per square foot in old currency. The best solar panels currently are only about 20%  efficient and it will be very difficult to get past 30% or so.  For the reason why, you need to understand the Carnot limit, see:
http://en.wikipedia.org/wiki/Carnot's_theorem_(thermodynamics)

Well, here's wikipedia right back at you!

http://en.wikipedia.org/wiki/Multijunction_solar_cell
This type of cells have a theoretical maximum efficiency around 90%..
So the only real limit now is economics.
Thing is, even with your calculated lower yield you still have enough roofspace on a house to cover a family.
But with time these high yield PVs will be widely available for a low enough price.
And like with bitcoin people will be 'mining' electricity.