Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: Geezer on 20/12/2010 02:59:35
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There has been some discussion about disposing of nuclear waste that is a byproduct of fission reactors by launching it into the Sun.
What does the energy balance look like? If we were to do this, would we expend more, or less energy than the energy we obtained from the reactor?
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Dear Geezer, Multiple rockets to the sun must overcome the 30 kilometers per second speed with loads of tens of thousands of tons. They would have to do it with gravitational assist from the Earth and Venus, taking years per voyage. I really wouldn't want thousands of those rockets up there on near collision courses with the Earth.
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Also, what about a launch failure. The best scheme I have heard about for the nuclear waste problem has been promoted by James Hanson (global warming guy) and others. There are several new nuclear reactor types that are being studied that are referred to as Generation 4 if anybody wants to research this. There is a pretty good nontechnical piece on Wikipedia. Some of these reactors can run on the waste from the older reactors and the final products have half lives in the hundreds of years instead of the multiple thousands of years of the current waste. So, if the reactors can be made safe they could actually use up the waste while generating electricity. I don't know enough about this to comment further. Check it out.
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Thanks William and Steve!
I'm sure there are many potential issues, and there are probably many alternatives to such a scheme, but I thought it would be interesting to try to understand if there was even a net energy gain associated with it. If the net energy gain is negative, then it's probably not even worth considering.
In it's most simplistic form, the question concerns energy versus the mass required to obtain that energy. That's why I posted it in the Physics forum.
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I cannot understand the obsession with the waste from fission reactors, coal fired power stations dump far more radioactivity into the environment and the deaths caused by coal mining are at least a thousand times as many as those caused by nuclear power station mishaps.
The present arrangements for storing nuclear waste are adequate and the only barriers for long term underground storage are only political.
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I cannot understand the obsession with the waste from fission reactors, coal fired power stations dump far more radioactivity into the environment and the deaths caused by coal mining are at least a thousand times as many as those caused by nuclear power station mishaps.
The present arrangements for storing nuclear waste are adequate and the only barriers for long term underground storage are only political.
I confess my question had a "slightly" political overtone. If the energy cost of dumping the byproducts into the Sun is small, why would we not do it?
So, (physicists) what's the energy balance?
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Here's a thought: What would be the longterm effect of dropping it (lightly encased) into the deepest parts of the worlds oceans?
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Here's a thought: What would be the longterm effect of dropping it (lightly encased) into the deepest parts of the worlds oceans?
Although not precisely an answer to your question, there has been some research carried out into the dumping at sea - in the 50's and early 60's the US dumped drums containing radioactive materials at a couple of deepwater sites. In the 70's there was some investigation of the "2800m" site which is approximately 200km off the east coast. The drums dumped there were mainly intact and the geochemistry of the sediment was investigated to see if the cation exchange capacity of the clay minerals in the sediment would be sufficient to lock up any leaks. I understand that the conclusion was that it might work, but the sedimentation rate was too low to cover the drums.
As a consequence there was some research into the possibillity of dumping drums into "turbidty currents" that run down the continental slope at 60mph, thus encasing the waste into turbidite depoists. However, these are too unpredicatble.
However, I guess the biggest obstacle to such dumping would be international treaty - it was banned by the London Convention in 1993...
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Geezer, I am pretty sure there is much more energy made by power plants than would be expended by any number of waste disposal schemes, including launching into the sun, but the energy balance is not important. What is important is the cost. The real cost of current nuclear reactors is already so high that increasing this is unacceptable (and they told us it would be too cheap to meter).
Peppercorn, there was a plan to explore putting the waste in the bottom of subduction zones so they would be carried down into the mantle. I don't know what happened with this idea, but I suspect that concern for the already highly stressed ocean ecology might have had something to do with it.
Steve
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Here's a thought: What would be the longterm effect of dropping it (lightly encased) into the deepest parts of the worlds oceans?
Oi! Start your own thread, matey! [;D]
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Geezer, I am pretty sure there is much more energy made by power plants than would be expended by any number of waste disposal schemes, including launching into the sun, but the energy balance is not important. What is important is the cost. The real cost of current nuclear reactors is already so high that increasing this is unacceptable (and they told us it would be too cheap to meter).
Steve,
It must take quite a bit of energy to send something to the Sun. Perhaps someone has data?
The "cost" of nuclear energy should really factor in the cost of safe disposal of the waste it produces, and burning it in the Sun strikes me as a very good long term solution compared with all the sequestration methods that many people object to.
Nuclear energy is expensive, but I really don't think we have an alternative. BTW, France seems to be doing just fine with its reactors.
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Geezer:
I just checked up on what Space X, a private launch enterprise in the US, is up to. They are talking about dropping launch costs per pound from $4,000 to $1,300 ($8,800/kg to $2,900/kg) and this is just to low earth orbit. Because spent uranium is heavy and spreading a bunch of radioactive material all over the landscape with the occasional launch failure, out of the thousands that would be required, you might rethink this idea.
Using standard reactor design peak uranium will be here in 20 years. The only way to build many more reactor and have a continuing fuel supply is to build breeders, and these are the ones that create weapons grade material. France has a mess that they probably won't continue, check out the cost overruns of their latest in Finland and on their own soil. There are plenty of less dangerous and less dirty power sources available that will be less expensive in the long run.
Steve
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Steve,
It may indeed be a lousy idea, but I'd still like to understand the energy consumed versus the energy produced. That alone may be sufficient to shoot it down in flames.
I have my own opinions about the need for nuclear energy, but that's probably a debate that we should have in a different thread.
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Here's a thought: What would be the longterm effect of dropping it (lightly encased) into the deepest parts of the worlds oceans?
Oi! Start your own thread, matey! [;D]
I thought about a pre-emptive apology when I wrote that and I realise now that it was a 'failing' not to include it! [:-X]
Peppercorn, there was a plan to explore putting the waste in the bottom of subduction zones so they would be carried down into the mantle. I don't know what happened with this idea, but I suspect that concern for the already highly stressed ocean ecology might have had something to do with it.
Deep enough it should have no effect on ecology I would have thought. (Although answer quietly lest Geezer notices)...
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Peppercorn:
I suspect that the deep ocean currents could spread a variety of chemicals that might form if a container were breached. I was going to use small type to be quiet, but ....
Steve
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The Shrinkomatic is nigh!
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Steve,
I like the idea of 'folding' waste back into the Earth's innards - makes me think of making cake mixture [:D]
The Shrinkomatic is nigh!
Nnnnnnnnnnoooooooooooooooooooo!!
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The Nuke Plants use about 10% of the power in the Fuel Rods.
It is like filling your tank with gas.
Using 1 gallon.
Dumping the rest
And filling up again.
WE NEED TO START RECYCLING THE FUEL RODS
And, no, making them into toxic bullets doesn't count as recycling.
Once that is started, that should cut the waste stream by 10 fold, and hopefully get rid of some of the most long-lived isotopes.
Burying in the ocean sounds like a very bad idea. Do we have anything that would hold up to the elements for 100,000 years? Vitrify it first?
Rather than being dependent on the sedimentary rate, one should just decide how deep of a hole is desired, and bury it.
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The Nuke Plants use about 10% of the power in the Fuel Rods.
It is like filling your tank with gas.
Using 1 gallon.
Dumping the rest
And filling up again.
WE NEED TO START RECYCLING THE FUEL RODS
And, no, making them into toxic bullets doesn't count as recycling.
Once that is started, that should cut the waste stream by 10 fold, and hopefully get rid of some of the most long-lived isotopes.
Burying in the ocean sounds like a very bad idea. Do we have anything that would hold up to the elements for 100,000 years? Vitrify it first?
Rather than being dependent on the sedimentary rate, one should just decide how deep of a hole is desired, and bury it.
Thanks Clifford. Now, if we could just get back to answering my actual question...... [::)]
(Sheesh! - It's worse than herding a flock of cats.)
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Yes let's get back to the original idea...
It's a terrible one!
Right. New topic!(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fwww.messentools.com%2Fimages%2Femoticones%2Fhumor%2Fwww.MessenTools.com-Humor-jijiiji.gif&hash=eb4c99ae263d32c2f942a4a27e8e5666)
I think the main problem is it's bloody heavy stuff and there's more than a fading chance of a problem a launch.
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Yes let's get back to the original idea...
It's a terrible one!
Right. New topic!(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fwww.messentools.com%2Fimages%2Femoticones%2Fhumor%2Fwww.MessenTools.com-Humor-jijiiji.gif&hash=eb4c99ae263d32c2f942a4a27e8e5666)
I think the main problem is it's bloody heavy stuff and there's more than a fading chance of a problem a launch.
Look buster - there's only room for one anecdotal physicist around here.
Yes, there could be a launch problem, but you're just using that as an excuse for not doing the math.
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Okay. Fair enough! Now where did I put that slide rule .... *goes off to route in drawers*....
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Surely it can't be so difficult to work this out.
How about we determine the amount of work done to elevate a mass far enough above the Earth's surface that it starts to fall towards the Sun, rather than back to Earth? No orbits or fancy trajectories required.
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Bodies don't start to fall towards the Sun they retain the orbital energy associated with their orbit around the Sun that has to be removed in some way.
There is no friction in their environment they have to be imparted with an acceleration of 30M/s from some source.
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Bodies don't start to fall towards the Sun they retain the orbital energy associated with their orbit around the Sun that has to be removed in some way.
There is no friction in their environment they have to be imparted with an acceleration of 30M/s from some source.
Ah! Good point. So we'd have to include the work required to achieve that deceleration of the mass, or it would just stay remain in orbit around the Sun.
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Sorry about heading astray,
But I do believe before shooting stuff into space, it needs to be reduced to the absolute minimum amount possible. Pull out all the fissionable isotopes and the non-radioactive "Rare Earth Elements". Then consider if there are enough long-lived isotopes left to justify the program.
As far as orbital insertion.
Isn't there a number of different approach angles.
If one aims dead center for the sun, it should plow straight in without worrying about a decaying orbit. One just needs to aim right.
I certainly don't want a proliferation of radioactive space junk in unstable orbits around any object in our solar system. [xx(]
2 Major Shuttle Accidents should serve as a reminder of the dangers of a space program.
Wikipedia has a list of Space Accidents, although I'm not sure if non-fatal accidents are listed.
http://en.wikipedia.org/wiki/Space_accidents_and_incidents
If the Shuttle Challenger had been carrying a few tons of nuclear waste, it could have been a disaster of epic proportions with waste both airborne and scattered through the Atlantic.
Certainly there are multiple nuclear waste streams. There are enormous amounts of low level waste. I was on a project that was digging up and shipping about 10 railcars full of low level waste a day to southern Idaho. And anything that touches it becomes low level waste too. The only thing that would be at all economical to "export" to space would be the high level waste, and even that would necessarily need to be reprocessed which might eliminate the problem.
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Yes, but how much energy would it take to get rid of the stuff? If it takes more energy to get rid of it than the energy energy it produced in the first place, it would not only be dangerous, but pointless.
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How about some numbers.
For the Saturn V
3,039,000 kg total loaded weight (I think). Oxygen, Hydrogen, Aluminum, whatever (about 90% fuel, 10% being structure).
45,000 kg payload to Trans Lunar Injection. I assume a bit more for a longer voyage, for example towards Venus.
http://en.wikipedia.org/wiki/Saturn_V
Anyway, that gives about a 1:100 payload/rocket mass ratio.
If very little of the rocket is recovered, then one can consider essentially everything in it as "fuel".
Ok, let's look at energy from Uranium:
1 ton of Uranium gives about 7.4 x 1016 Joules.
1 ton of Coal gives about 3.2 x 1010 Joules.
http://www.phy.syr.edu/courses/modules/ENERGY/ENERGY_POLICY/tables.html
It takes about 300 kwh of electricity per pound of metal aluminum produced.
1 kWh = 3600000 J
Or, about 1 x 109 Joules/pound aluminum.
(oops, on the order of 100 lbs coal / pound of aluminum, I think [:-\])
So, Uranium gives about 2 x 106 times as much energy as coal, or 2,000,000 times as much energy than coal.
So...
If it took 1000 tons of coal to blast 1 ton of uranium into space (production costs and etc). You would still have a net energy surplus from using the Uranium. But the actual value would quickly dwindle if you considered all the refining costs & etc.
Keep in mind that all fission byproducts are not the same.
As I mentioned, in the USA, only about 10% of the "new" nuclear fuel is burnt, and 90% remains.
According to Wikipedia, there are about 7 "Long-Lived" Nuclear waste isotopes with half-lives ranging from 200,000 years to 15 Million years, accounting for about 20% of the fission waste products.
http://en.wikipedia.org/wiki/Fission_product
Another 12% of the waste has half-lives of less than 90 years, and could likely be effectively managed on earth.
It would take more time than I have tonight to look at the entire decay chains of every product, what is fissionable, percentages, and etc.
Anyway, so, if effectively separated, and reburnt, only about 20% of the original reactants would need to be disposed of in a "permanent" storage facility, and we would get about 10x the energy out that we are currently recovering.
It is still probably not economic as far as dollars and cents to ship this waste to space, but it certainly could be done.
Perhaps summing it up, it would take on the order of 0.1% of the energy produced to ship the high level, long life radioactive waste up into space.
There are discussions online of using other types of (pie in the sky) accelerators other than conventional rockets to make it more cost effective in the future.
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Yeahh!!
Numbers are good. Thanks Clifford.
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Does anyone know how much work would be required to lift 1 kg to L1 (Lagrangian point 1)? I understand it's around 1.5 million kilometers out.
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60 megajoules
calculated by myself, from escape velocity 11 km/s, might be 10% off
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from escape velocity 11 km/s, might be 10% off
Are you sure? L1 is at a much greater height than the orbit for escape velocity.
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Heh, Then we could try to arrange them to pulsate too, and now and then explode :) "Hey, can you see us?" sort of. I know, it's not that much energy maybe but still, it should beat the fourth of July if you're close enough. and then we have all those colors 'strontium' and stuff :)
But seriously, if you really want to create nuclear waste I would suggest we put it in our city's, glassed in or whatever method we might find work. That would ensure that we never lost sight of them, and no, I'm not joking. That way we all would be deeply involved in keeping them from 'leaking'.