quote:However while it is possible I misread it I am highly doubtful...
Blayne, Asimov was -- he's been dead for a few decades, now -- a self-avowed polymath, meaning he wasn't an expert at much. In fact, many specialists even in his own day complained at great length about the things they believed he got wrong in his non-fiction (and his fiction).
A case of Science Marches On, many of the times he included science in his fiction he cant be helped if what he wrote happened to be cutting edge at the time he wrote.
However he WAS a Professor in Chemistry which was his Phd so its not like he never specialized in something.
Blayne, Isaac Asimov was in fact a professor of biochemistry at the Boston University school of medicine. He was however essentially inactive as a scientist after 1958 when he turned to writing science fiction full time. While his science fiction was cutting edge, his science never really was. That isn't a criticism. His popular science articles for the most part very accurate even though they do not represent original scientific contributions on his part.
I have looked through indexes of Asimov's essays on nuclear power. He wrote several articles on nuclear fusion in the 1970s, nothing more recent. Unless the indexes are incomplete, he never wrote about nuclear fission, the process which uses Uranium fuel. Since I don't know which specific article you read, I can check to see whether Asimov actually talked about Uranium reserves, perhaps you could provide a more specific reference? Regardless of what was in the article, the estimate that we have enough Uranium to last 100,000 is inconsistent with what experts in the area were saying even in the 1970s. I have enough respect for Asimov to think the mistake is more likely in your understanding rather than his work but I could be wrong.
Currently, it is estimated that "proven" Uranium reserves are sufficient to last ~60 years at current levels of consumption. The most optimistic estimates are that undiscovered reserves (excluding sea water) will last between 200 - 600 years at current levels of consumption. Right now, ~15% of the global electricity comes from nuclear fission. In order to make a significant reduction in greenhouse emissions, that we would need at least 5 times that much nuclear power, possibly more if we are considering using electricity rather than fossil fuels for transportation. That would exhaust the "proven" reserves in a little more than a decade and even the optimistic estimates of reserves yet to be discovered in a little more than a century. While a number of technologies have been proposed that would increase the amount of available nuclear fuel (breeder reactors, thorium reactors, and fusion reactors for example) none of those technologies are currently viable. They are still in the research and development phase. We can't start building power plants with these technologies in the near future, we can't even guarantee that we will every be able to safely and economically use these technologies.
I agree that it is foolish in the current crisis to ignore nuclear power. Its equally foolish to believe that nuclear power is the panacea that will solve the entire problem. The numbers just don't add up. The same thing is true for solar, wind, hydropower, and every other alternative being explored. No one technology is going to save us.
Posts: 12591 | Registered: Jan 2000
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quote:I'm not sure what I've done to offend you but lately you seem to jump in to every debate in which I'm involved for apparently no reason but to insult me.
I'm not doing it to insult you. I'm doing it to warn you that you're being pompous and irascible and damaging the very causes you're trying to advocate for.
I'm sorry Tom, but its gone way beyond that. You single me out even in discussions where my opponents are equally pompous and irascible. It feels like you are following me around with the mission of reprimanding me when you think I've overstepped some line of civility. Its a very condescending and arrogant thing to do and whether you consciously intend it as an insult or not, it is insulting.
Posts: 12591 | Registered: Jan 2000
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quote:You single me out even in discussions where my opponents are equally pompous and irascible.
Because I think more highly of you than I do of them, and regard your pompous irascibility as something temporary, which can be corrected.
If you are insulted by the fact that I perceive you to have a vulnerability in this regard, I'm sorry. That doesn't mean, however, that I'm wrong.
Posts: 37449 | Registered: May 1999
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posted
Rabbit: yes, there is a minimum energy required based on concentration, but there's a step you missed: showing that the concentration is so low that the amount of energy available from the uranium is lower than the amount required to extract it.
Funnily enough, others have done the math, and it is feasible (especially if you're already doing part of the process for another reason, anyways).
Additionally, an extraction process can be economically efficient even if it requires more energy to get uranium out than is retrieved from it. To see why this is true, consider the example of carnivores, which eat large numbers of herbivores. For instance, if we could create a fish that sequesters uranium in somewhat higher concentrations in itself, then release the fish in the ocean and harvest their offspring, a large amount of energy involved in extraction would be transmitted directly and through the food chain from the sun to the fish. Thus, while the total energy required to extract the uranium from the water would be much greater than the energy of the uranium (since that process is very inefficient), we wouldn't have to have generated the energy in the first place; we'd be taking it from another source of energy we couldn't harness otherwise, in exchange for getting the energy we actually can use.
Posts: 15770 | Registered: Dec 2001
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Blayne Bradley
unregistered
posted
quote:Originally posted by The Rabbit:
quote:Originally posted by Blayne Bradley:
quote:Originally posted by TomDavidson:
quote:However while it is possible I misread it I am highly doubtful...
Blayne, Asimov was -- he's been dead for a few decades, now -- a self-avowed polymath, meaning he wasn't an expert at much. In fact, many specialists even in his own day complained at great length about the things they believed he got wrong in his non-fiction (and his fiction).
A case of Science Marches On, many of the times he included science in his fiction he cant be helped if what he wrote happened to be cutting edge at the time he wrote.
However he WAS a Professor in Chemistry which was his Phd so its not like he never specialized in something.
Blayne, Isaac Asimov was in fact a professor of biochemistry at the Boston University school of medicine. He was however essentially inactive as a scientist after 1958 when he turned to writing science fiction full time. While his science fiction was cutting edge, his science never really was. That isn't a criticism. His popular science articles for the most part very accurate even though they do not represent original scientific contributions on his part.
I have looked through indexes of Asimov's essays on nuclear power. He wrote several articles on nuclear fusion in the 1970s, nothing more recent. Unless the indexes are incomplete, he never wrote about nuclear fission, the process which uses Uranium fuel. Since I don't know which specific article you read, I can check to see whether Asimov actually talked about Uranium reserves, perhaps you could provide a more specific reference? Regardless of what was in the article, the estimate that we have enough Uranium to last 100,000 is inconsistent with what experts in the area were saying even in the 1970s. I have enough respect for Asimov to think the mistake is more likely in your understanding rather than his work but I could be wrong.
Currently, it is estimated that "proven" Uranium reserves are sufficient to last ~60 years at current levels of consumption. The most optimistic estimates are that undiscovered reserves (excluding sea water) will last between 200 - 600 years at current levels of consumption. Right now, ~15% of the global electricity comes from nuclear fission. In order to make a significant reduction in greenhouse emissions, that we would need at least 5 times that much nuclear power, possibly more if we are considering using electricity rather than fossil fuels for transportation. That would exhaust the "proven" reserves in a little more than a decade and even the optimistic estimates of reserves yet to be discovered in a little more than a century. While a number of technologies have been proposed that would increase the amount of available nuclear fuel (breeder reactors, thorium reactors, and fusion reactors for example) none of those technologies are currently viable. They are still in the research and development phase. We can't start building power plants with these technologies in the near future, we can't even guarantee that we will every be able to safely and economically use these technologies.
I agree that it is foolish in the current crisis to ignore nuclear power. Its equally foolish to believe that nuclear power is the panacea that will solve the entire problem. The numbers just don't add up. The same thing is true for solar, wind, hydropower, and every other alternative being explored. No one technology is going to save us.
I'm pretty sure he was active as a scientist past the 1950's if we include his full time teaching position as him also being active as a scientist.
The article was included in one of his popular science anthologies, I think one of the other articles included also had his article on Judo Arguments against Intelligent Design and an article on Skewes Number.
As I said, the article is about nuclear fusion but the first one third was about nuclear fission.
A nitpick he wrote an article in the late 80's on Tritium.
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quote:I'm pretty sure he was active as a scientist past the 1950's if we include his full time teaching position as him also being active as a scientist.
According to wikipedia, he didn't not teach full time after 1958. Wikipedia could be wrong about that I guess, but it is consistent with information from other sources.
Posts: 12591 | Registered: Jan 2000
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quote:Originally posted by The Rabbit: I left because I needed to finish a couple of projects. I'm back for a day or two to reward myself for having completed the first of those.
quote:You single me out even in discussions where my opponents are equally pompous and irascible.
Because I think more highly of you than I do of them, and regard your pompous irascibility as something temporary, which can be corrected.
That's not unlike something you said to me recently, and I find it a little heavy handed, especially since you've been talking to me in much the same way (on and off) for years.
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quote:Originally posted by The Rabbit: The laws of thermodynamics are something of a bummer. I've heard them summarized this way. First Law: The best you can do is break even. Second Law: you can only break even at absolute zero. Third Law: you can never get to absolute zero.
Heh.
I think Bill Bryson quoted somebody else as saying: 1. You can't win. 2. You can't break even. 3. You can't get out of the game.
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quote:That's not unlike something you said to me recently, and I find it a little heavy handed, especially since you've been talking to me in much the same way (on and off) for years.
Oh, I'm not denying it's heavy-handed.
Posts: 37449 | Registered: May 1999
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quote:Originally posted by Orincoro: I think Bill Bryson quoted somebody else as saying: 1. You can't win. 2. You can't break even. 3. You can't get out of the game.
That's always been my favorite version. (And Google reminds me that it's usually attributed to C.P. Snow.)
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quote:That's not unlike something you said to me recently, and I find it a little heavy handed, especially since you've been talking to me in much the same way (on and off) for years.
Oh, I'm not denying it's heavy-handed.
It's not just heavy handed, its pompous and condescending. I'm surprised that you don't see the irony in what your doing.
Posts: 12591 | Registered: Jan 2000
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posted
While it does come off as pompous and condescending, Tom does have a point. I can understand why you adopt the tone that you often do when it comes to this topic, but I don't think that it is often helpful.
You wouldn't deny, would you, that there is a certain arrogance to statements like "if you think that is not correct, you do not accurately understand thermodynamics"? Fugu's a bright guy. You know him, or if you don't, you should, given how long both of you have been involved in this community. Generally, when he says something, it's worth paying attention to. I certainly don't always agree with him, but I pretty much always give the things that he says consideration. If you're going to argue with him, it's a mistake not to; chances are, what he's said is considered, and backed up by something solid, as it was in this instance.
What would have been wrong with saying something along the lines of "Fugu, that goes counter to my understanding of the second law of thermodynamics" and then going on to explain why? What does the contemptuous tone you adopted when addressing him serve?
Posts: 16059 | Registered: Aug 2000
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quote:Originally posted by fugu13: Rabbit: yes, there is a minimum energy required based on concentration, but there's a step you missed: showing that the concentration is so low that the amount of energy available from the uranium is lower than the amount required to extract it.
Funnily enough, others have done the math, and it is feasible (especially if you're already doing part of the process for another reason, anyways).
Interestingly, I could find anything in those reference about the minimum energy of separation.
I think the problem here is that we are mixing two different issues. It is possible to purify some Uranium from sea water using less energy than can be obtained from the fission reaction. My objection is to those who calculate the total amount of Uranium available in sea water and claim that is all potentially usable Uranium. It isn't. I've done the calculations and it simply isn't possible to recover any significant fraction of the Uranium in sea water in an energy efficient manner.
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posted
I make the minor assumption that a journal-full of nuclear scientists aren't overlooking a well-known limitation taught to undergraduates.
I'm not sure what you mean by "significant fraction". If even .1% of the uranium in seawater could be extracted with moderate efficiency, that would be a huge source of additional energy. Could you provide your calculations? A quick back-of-the-envelope approximation is fine. I note that this is also a weaker statement than your original one, which professed that it was impossible for all seawater:
quote:the laws of thermodynamics dictate that no technology ever will exist that would allow us to do that for less energy than we could get from the Uranium
Also, see the rest of my post: even if it cannot be done without more energy put in than is taken out, that does not mean it is a bad idea. It is only required that the energy over the amount made available is not energy we could otherwise harness for useful work.
Posts: 15770 | Registered: Dec 2001
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quote:The concentration of uranium in ocean water is about 3 parts per billion (Uranium Information Center, 1999). From Eq. (3), the minimum work required to separate one atom of uranium from seawater is about 0.5 eV. This energy is minute as compared with the energy release from nuclear fission of about 200 MeV. Thus, the separation process could be exceedingly inefficient and yet still yield a large net energy gain in fission energy technologies.
He also mentions that this seems to already be in range for at least one process (on commercial scales).
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posted
While I think The Rabbit's tone wasn't necessary (and, yeah, she was off on some of the nuclear stuff, at least as far as I understand the industry), I understand her frustration in dealing with some of the misinformation out there.
For example, a coworker of mine just emailed our group this lovely piece he received from some industry list he's on. (He consults on the private side of environmental energy, I'm on the public side with the EPA Clean Air Division as our main client. I think I'll let them know that they shouldn't label CO2 a pollutant.)
quote:Why would labeling CO2 as a pollutant be such a catastrophic decision?
Claims that CO2 is a pollutant are a myth and are absolutely false. In fact, lowering levels of carbon dioxide would actually inhibit plant growth and food production. What we see happening in Washington right now is the replacement of politics for science in conversations about CO2.
Earth and it's inhabitants need more, not less, CO2.
More CO2 means:
More Plant Growth Plants need less water More food per acre More robust habitats and ecosystems CO2 is Earth's greatest airborne fertilizer. Without it - No Life On Earth!
P.S. Their site is amazing. AMAZING!
Posts: 2409 | Registered: Sep 2003
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posted
Wow, I had no idea that Obama's EPA was trying to end all life on earth.
Now I'm totally against the EPA!
You have to, well maybe not admire or respect, but at least be impressed by the brazenness of that kind of hatchet job. I sort of have a tiny problem with labeling CO2 as "pollutant," at least as far as any traditional thoughts as to what a pollutant is, but for regulatory purposes, it's a necessity. An email like that however would be hilarious if I didn't think that a lot of people would actually take it seriously.
Posts: 21898 | Registered: Nov 2004
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quote:Originally posted by fugu13: Ah ha, here's someone who has run the calculation.
The key quotation:
quote:The concentration of uranium in ocean water is about 3 parts per billion (Uranium Information Center, 1999). From Eq. (3), the minimum work required to separate one atom of uranium from seawater is about 0.5 eV. This energy is minute as compared with the energy release from nuclear fission of about 200 MeV. Thus, the separation process could be exceedingly inefficient and yet still yield a large net energy gain in fission energy technologies.
He also mentions that this seems to already be in range for at least one process (on commercial scales).
What he calculated is the energy required to remove one atom Uranium atom from seawater. What I have calculated in the past is the minimum energy required to remove all the Uranium from 1 mole of seawater.
Its been sometime but the calculation goes something like this. The minimum work = RTlna, assuming a temperature of 273 K (0°C) and 3 ppb by weight Uranium which is 0.7% U235, that gives 68 kJ per mole of water which translates to 440 GeV per atom of U235 recovered.
(edited to add that I didn't this calculation by the seat of my pants, its been some time since I've been through this in more detail and I can't guarantee I haven't made some fundamental mistake).
I believe the difference between his calculation and mine is that I am looking the energy required per atom to recover all the Uranium from seawater and he is looking at the energy/per atom to recover a negligible fraction of the Uranium in seawater.
My objection is when his number is used along with the total amount of Uranium in seawater as though combined they represent a reasonable estimate of accessible reserves. They don't. If my original statement made it seem that I was claiming that no net energy could be obtained from any Uranium in seawater, it was not intended to do so.
I haven't found anyone who has estimated how much Uranium could be recovered from seawater at the break even point and I don't really have the time to do that myself.
My original point, however, that Nuclear energy can't be seen as a panacea for our energy/climate problems stands. Based on the Nuclear industries own estimates of proven reserves that are accessible using existing technology, we have 60 years of nuclear fuel at current levels of consumption. Exploration and improved technologies are likely to significantly increase that number, but very unlikely to change the over all picture which is that we can't meet our energy demands with nuclear power alone over the long term. Nuclear energy isn't a panacea.
[ October 13, 2009, 07:07 PM: Message edited by: The Rabbit ]
Posts: 12591 | Registered: Jan 2000
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quote:Originally posted by Jhai: While I think The Rabbit's tone wasn't necessary (and, yeah, she was off on some of the nuclear stuff, at least as far as I understand the industry), I understand her frustration in dealing with some of the misinformation out there.
For example, a coworker of mine just emailed our group this lovely piece he received from some industry list he's on. (He consults on the private side of environmental energy, I'm on the public side with the EPA Clean Air Division as our main client. I think I'll let them know that they shouldn't label CO2 a pollutant.)
quote:Why would labeling CO2 as a pollutant be such a catastrophic decision?
Claims that CO2 is a pollutant are a myth and are absolutely false. In fact, lowering levels of carbon dioxide would actually inhibit plant growth and food production. What we see happening in Washington right now is the replacement of politics for science in conversations about CO2.
Earth and it's inhabitants need more, not less, CO2.
More CO2 means:
More Plant Growth Plants need less water More food per acre More robust habitats and ecosystems CO2 is Earth's greatest airborne fertilizer. Without it - No Life On Earth!
P.S. Their site is amazing. AMAZING!
The really facinating thing about this claim is, that like many of the climate change deniers arguments, it isn't something that has been overlooked. Its known as CO2 fertilization and it does in fact happen in green house situations. The hypothesis that it will happen in nature and offset the green house effect has been investigated by several researchers using both model calculations and controlled experiments and the answer is -- No. The hypothesis is wrong.
In the real world, CO2 is only one of many nutrients plants require to grow. CO2 fertilization only works in green houses because you can also increase the concentration of all the other nutrients plants needs. But in the real world, CO2 is very rarely the limiting nutrient for plant growth. In the oceans, where a very large fraction of photosynthesis occurs, the limiting nutrient is usually iron. On land, its typically water, nitrogen, phosphorus and potassium which is why irrigation and artificial fertilizers have been so successful in increasing farm productivity.
The bottom line is, that the scientific method has been used to test this hypothesis and proved it is invalid.
Which highlights what constitutes "good science" and why what's coming from climate change deniers is so bad. Good science requires more than generating plausible hypotheses, it requires testing those hypotheses with rigorous experiments. The real scientists who are studying climate change didn't just take this hypothesis and throw it out because it didn't support their case. That's what they would have done if the accusations that they are doing bad politically motivated science were true. No they took this hypothesis and subjected it to rigorous experiments, and unfortunately for all of us it turns out to be wrong.
The climate change deniers on the other hand, do exactly the opposite. They take hypotheses like these and because they fit their political motives they not only fail to test the hypotheses themselves, they also ignore the results of all the studies which show the hypothesis is wrong.
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quote:Originally posted by Orincoro: I think Bill Bryson quoted somebody else as saying: 1. You can't win. 2. You can't break even. 3. You can't get out of the game.
That's always been my favorite version. (And Google reminds me that it's usually attributed to C.P. Snow.)
Its clever, but not really all that accurate, particularly for the 3rd law.
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quote:What I have calculated in the past is the minimum energy required to remove all the Uranium from 1 mole of seawater.
Its been sometime but the calculation goes something like this. The minimum work = RTlna, assuming a temperature of 273 K (0°C) and 3 ppb by weight Uranium which is 0.7% U235, that gives 68 kJ per mole of water which translates to 440 GeV per atom of U235 recovered.
Question from an utter layman:
How does it change the results if you're only trying to recover, say, 75% of the U235 in the water, rather than all?
Posts: 2907 | Registered: Nov 2005
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posted
Fugu13, when you speak of removing uranium from sea water, are you talking about the U-238 isotope, which is the most common and cannot be used to produce a fission reaction, or the U-235 or U-237 isotopes, which are fissionable and present in much smaller amounts?
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