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I love electricity. And I love Nuclear energy. But I hate using NE to boil water to make electricity.
Why can't we make a beam of charged particles...beta, alpha for example? They could create a magnetic field, that could be used to induce current in some copper wire.
Remember me on the patent!
Seriously, isn't there some possible way to transduce nuclear energy into electrical that is better than steam?
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The heat from nuclear reactions can be used to generate electricity directly by means of a thermocouple, as in the RTGs used to power our deep space probes. That eliminates the intermediate mechanical steps of a steam engine and a dynamo. Whether or not that makes a "better" generator depends on the needs of the task at hand.Originally Posted by Procyan
The RTG has no moving parts and is maintenance free, which is ideal for use in a spacecraft where under a kilowatt of low voltage direct current meets its needs. I do not know how efficient it is compared with using the same amount of heat to power a steam engine turning a dynamo. Even if this efficiency or possible lack thereof is not an issue, I would be concerned with the need to generate thousands of kilowatts of commercial juice at high enough voltage for transmission over practical transmission lines. I would be interested in hearing from electrical engineers on this one.
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As I suspect this will be more of a general discussion, rather than a simple answer to a question, I've moved the thread from Q&A to S&T.
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I'm not an electrical engineer, but my understanding is that the efficiency is not great for an RTG or similar device, and the materials are expensive. Steam generation and steam turbines are very well understood technologies, work very well, and seem to have very high reliability. I also suspect that RTGs do not generate high voltages, which are needed for transmission. They also would generate DC power, but I don't know if that is an issue.
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I am not a nuclear physicist, but I suspect there are a few snags. Like, the charged particles will want to join up with their opposite numbers ASAP. Like, it would take more energy to produce the magnetic fields that focus the beam than we could produce as electricity. Like, a radiation source strong enough to produce a usable amount of electricity in this manner would be very dangerous.
Come to that, beta particles are electrons. Why can't we just feed them into the wires? Probably because there simply aren't enough of them being produced.
I suspect that if there were some more direct way to produce electricity from a nuclear source, someone would have thought of it already and we'd all be driving around in Ford Nucleons.
Fred
"For shame, gentlemen, pack your evidence a little better against another time."
-- John Dryden, "The Vindication of The Duke of Guise" 1684
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I've just realized something shameful. I don't know what nuclear energy is. Except gamma rays, those are electromagnetic, no problem. But a "ray" of helium nuclei is what, kinetic bowling balls? I know any fast moving charged particle emits radiation, so I guess thats the real energy release? when they discharge sufficient energy, then what, do they become regular old ions and electrons?? Pretty bad I know.
Last edited by Procyan; 2011-Mar-14 at 03:51 AM. Reason: atrocious grammar even for me!
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We have some regulars who are better qualified than I , but perhaps they are holding back as they don't want to dilute even slightly their favorite nuke, which they hope will soon be funded. Worse, I am somewhat anti nuke, but I will kick this off anyway. I think of a few alternatives to steam, but I think they are inferior to steam in efficiency, watts per cubic meter and watts per initial dollar:
The charge on the ionized particles is electricity, so it can be collected by separating the positive ions from the negative ions with a magnetic field. Most of the energy is the velocity of these particle, so the collector plates need to be water cooled so we make steam with the kinetic energy which much exceeds the charge energy. Perhaps we gained a bit by doing both charge collection and steam. An extremely tiny example of charge collection is a typical smoke detector. The charge collection is reduced by the smoke/the reduction triggers the alarm which is powered by a 9 volt battery. I suppose the 9 volt battery could also be charged by the collected electrons, but this has not been done as far as I know.
Another nuclear generator is the RTG = radioisotope thermal generator which is about 1% efficient with dissimilar metals = thermocouples or 10% efficient with PN junctions = semiconductor. Steam is 30% efficient, more with combined cycle. Likely more practical is for the PN junctions to cool the waste heat of a boiling water power plant, be it nuclear, solar or fossil fuel.
Some pilot plants have been built for the third method heating helium instead of steam to turn turbines = not much different than steam except we have a limited supply of helium and preventing helium leaks is very difficult. Neil
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That ray of helium nuclei you're talking about is often referred to as alpha particles, and yes, a simplified way of looking at them is as bowling balls. The energy is kinetic and transfers through bouncing into their surroundings, so their energy becomes heat by making other atoms move faster as the alpha particles slow down.
Beta particles (electrons) do the same bouncing around until they slow down.
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Reductionist and proud of it.
Being ignorant is not so much a shame, as being unwilling to learn. Benjamin Franklin
Chase after the truth like all hell and you'll free yourself, even though you never touch its coat tails. Clarence Darrow
A person who won't read has no advantage over one who can't read. Mark Twain
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Thanks I get it. Neil are you saying that there ARE some radical new transduction designs in the offing? I hope so!
So, some direct electricity generation is possible by separating helium nuclei from beta electrons But the kinetc energy is greater and that is used to boil water (or via Seebeck effect in RTGs). That makes sense. The thing that bothers me is that 30 percent efficiency. I know...tough muffins. Still there should be some nano-wind mills that catch that kinetic energy or something. Come on this is 2011! "Scotty, I need more juice. Put all the nano momentum-suckers on line!"
Neil, I hope you become pro nuke. I really am concerned that the Japanese experience will get spun towards the negative with respect to NE when it appears to be developing into a success story. Also I have confidence that the Japanese are in control at the root of it. It would be so un-Japanese not to be.
BTW, if anyone could show that solar/wind etc alt energy was anywhere near as good as nuke then i would be for that. you see, my first love is juice and she is forever my main squeeze. Whatever way makes the most juice is the right way. Actually I'd bet that like most of us, you to0 are a juice hound whether you can admit it or not. Oh I could give it up if I wanted to, really I could.
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I see the regulars did not hold back until I finished my post. I suppose 5 million PN juctions in series will produce a million volts for a HVDC = high voltage direct current powerline which is what we should be doing anyway for distances over 1000 kilometers.
Yes regular old ions after they loose most of their speed/ In a metal collector they become holes and electrons so we need separate collectors for the positive and negative ions.
Yes the radiation source to produce gigawatts would be very dangerous and other snags are likely, but super conductors can produce poweful magnetic fields for decades after the inital energy gets them started, except the radiation would likely degrade the super conductors in months instead of decades. Neil
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Solar/wind are also quite good, but at other things than nuclear is good at. What's really needed is combining all the different technologies to solve all the different requirements of power generation rather than trying to find a single solution for everything.
One of the weaknesses of nuclear is that it's rather bad at changing output power levels fast, which means there's an upper limit to how much production capacity it makes sense to cover by nuclear before it becomes too difficult to follow changes in consumption.
This is somewhat analogous to wind power, where the problem of having too much is not being able to compensate for changes in power generation.
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Reductionist and proud of it.
Being ignorant is not so much a shame, as being unwilling to learn. Benjamin Franklin
Chase after the truth like all hell and you'll free yourself, even though you never touch its coat tails. Clarence Darrow
A person who won't read has no advantage over one who can't read. Mark Twain
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This exciting stuff. Super conductors! Regarding degradation... if the radiation gets transduced through the magnetic fields, then the superconductors would be protected wouldn't they? And HVDC for long distance. I take it the key is the HV? Else why do we use AC at all?
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Neutron activation might be a problem.
Et tu BAUT? Quantum mutatus ab illo.
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Hi Procyan: I do like the thorium breeder reactor which can extract most of the energy left in those used fuel rods we have stored at more than half of the world's nuclear power plants. Also the thorium is more abundant than uranium, so we have enough for thousands of years, instead of hundreds of years. Some detractors claim only a few decades, if we build lots of uranium reactors.
My issue is we need to do something that looks smart in the USA, quick about the import of foreign oil, or USA is likely to collapse economically and take the rest of the world back to the dark ages with us. The president appointed a committee = a decade is likely before we have consensus on which designs of nuke to mass produce. That thorium reactor does have some unresolved issues such as the molten thorium fluoride, plus there are likely a hundred other details that are debatable. I'm far from an expert so my opinions are the one's that sound most convincing. There is another committee on the USA power grid: I'm not sure they are even considering HVDC, even though it has worked well in several countries. Wikipedia has a decent article titled HVDC. USA has the world's best wind corridor in West Texas and the states to the north, but we need HVDC, as few people live in the wind corridor. The wind farms already built are hurting for lack of customers for the electricity they are making. Solar in New Mexico has the same problem = not enough customers. Solar is half as good in Florida where I live and wind turbines near useless, partly because Florida has lots of tall trees and hurricanes.
As Ara Pacis typed, the neutrons will not be deflected, so some are likely to hit the super conductor.
It has only been the last two decades that step up and step down of DC voltages has been reasonably inexpensive. The high voltage DC would generally be converted to 3 phase ac for local distribution as medium size transformers are cheaper. The big very high voltage transformers are a national security problem, if terrorists destroy a few hundred of them as that is about the world's total annual production of big high voltage transformers. Short term partly constructed HVDC power lines could be cannibalized to repair damaged components in existing HVDC power lines. We could however do a pilot program of DC for homes and businesses. It would likely have few disadvantages compared to AC. Neil
Last edited by neilzero; 2011-Mar-14 at 06:31 AM.
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Let's change this to neutron activation WILL be a problem.
Some of the silicon atoms will absorb a neutron, which will step the 30Si up to 31Si which decays to 31P, which means it becomes more n-doped over time in a neutron flux.
This is (or at least has been) used commercially for doping the base wafers for IC's.
__________________________________________________
Reductionist and proud of it.
Being ignorant is not so much a shame, as being unwilling to learn. Benjamin Franklin
Chase after the truth like all hell and you'll free yourself, even though you never touch its coat tails. Clarence Darrow
A person who won't read has no advantage over one who can't read. Mark Twain
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Ara/Henrick, I think I'm following, Neutrons, being neutral, won't be attenuated by any form of transduction, so they will blast into the superconding material transforming si into p...consequence = ohms = no more superC. Ermm, Boron sponges? What do I know?
Just how close are we to a superconducting pilot plant?
The problem with alt energy is akin to alt medicine. Folks get lulled into the feeling that there are some nice comfy options. Especially if those options involve help from mother nature. I live near a great beautiful wind farm. I think they are lovely and I love the juice they make. Gosh the people here complain about them though...not natural. We're clean and green here. The Kiwis most certainly are not having any nukes here. We can smell the uranium on your breath. Eeek. But the DARK AGES you say? Not me. Been sitting on these piles for years, may as well get some use of them. As Francesca put it, "I was just going to have some iced tea and split some atoms."
I was in NY during the 70's energy shortage. I remember when OPEC flexed. Some people said this is a new kind of war, that America must win. FFD to 2011...Now she needs something smart and quick? Can't change the past. Change the future? I hope so.
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Making juices with nukes? We could call it Juke™.
Scaling up an RTG is frought with difficulty. RTGs require good radiative capability to avoid overheating. The bigger you scale the RTG, the more problem this causes. If you make it so big you can't passively cool it, then you're in trouble because RTGs can't be turned off.
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There is an overview of various forms of atomic battery here: http://en.wikipedia.org/wiki/Atomic_battery
I doubt these can be scaled up to power station scale. But maybe there could be one in every home...
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If the present situation has altered my opinions, it is to make me think more carefully about being too frivolous with applications. My earlier talk about putting nuclear reactors in planes and cars was always a little facetious, but there was an element of serious ambition to it. I'm now reminded to respect the awesome power of fission. My opinion is strengthened that we can do that however.
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If I were contemplating a thermionic generator in the many megawatts range, it would not be with the Pu238 canisters of the small spacecraft units. It would be with the same reactors that are used to power the steam engines we use now. They are powered up or down as needed.
In a thought experiment we could connect thousands of thermocouples in series to get the desired high voltage. That does not necessarily mean it would be anywhere near as efficient as a steam engine. In addition it would be direct current, which requires some elaborate electrodynamic gymnastics to step the voltage up our down. This is done with simple transformers with the AC that conventional dynamos generate naturally.
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With the stuff going on with the power plants in Japan, you do have to wonder why some form of thermionic generator isn't built into the walls of the containment vessels to power emergency cooling systems.....
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In theory, a fission fragment reactor could offer the benefits you hope for. However, we don't know a way to do it. There are numerous design challenges.
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Why?
I've seen this sentiment stated before, but never backed by much more than "it's old", and a vague idea that "there should be something better". Steam works, and it works quite well. A liquid/gas phase change makes an effective way to convert thermal power to mechanical power on very large scales. Water is well suited to that process and its use has been highly refined over time.
Thermoelectric techniques tend to have abysmal efficiencies. AMTEC could achieve similar efficiencies, but it's unclear if it'd scale up as well, and what its advantages might be. As mentioned, aside from the issues of figuring out how to build one, fission fragment reactors could be used in a direct conversion system, but are probably only applicable to spacecraft...otherwise, what do you do with the unstable fission products swinging through your magnetic fields? And the neutrons would waste a good deal of energy as heat, as well as causing the other problems mentioned.
What's so terrible about steam?
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Hmmm, I wonder if you could take two fission fragment streams and orient them so that they turn a dynamo...
Et tu BAUT? Quantum mutatus ab illo.
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Are you familiar with steampunk?
Et tu BAUT? Quantum mutatus ab illo.
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