Thomas wrote:blatham wrote: And it's not irrational for folks to make decisions which place greater emphasis on prudence (even if the cold numbers advise they will be better off in 9 out of 10 instances).
I'm not saying it's irrational. Nuclear accidents have killed a few people of every profession while coal mine accidents have killed a lot of coal miners. Why bother with dying coal miners if I ain't one of them? You're right, it's perfectly rational for me to oppose nuclear energy and support coal. It's just not a position I have a lot of respect for.
I am unpersuaded by the point about prudence you have made in this context. It is prudent to avoid deaths from coal; it is just as prudent to avoid deaths from uranium and plutonium; and coal is the energy source that is killing more people. So in my opinion, most people who favor coal over nuclear energy are less prudent than those with the opposite preference. They are just more prudent about risks that affect
themselves than about risks that only affect others.
But what if you had an uncle living in Bhopal, thomas?
It really seems like the classic indictment of a teenager's risk-taking. They don't know how bad it can be until it happens to them, though it might be too late.
The real question here is, How do you evaluate alternatives, all of which involve some adverse side effects, in situations in which we must make a choice?
The issue becomes clear whern one compares alternatives with generally known adverse side effects. Mortality at Bophal was an order of magnitude worse than Chernyobyl. The Three Mile Island event took no lives and the subsequent analysis was that there is a 40% likelihood of one additional case of Lukemia in the exposed population during the 40 year period after the event. Public health data does not reveal any effect at all. In general, on a probalistic basis, the public risk due to a standard nuclear powerplant over its 50 year life is about equal to that of a busy traffic intersection over just a couple of yearts. There is truly no comparison here, but the fact is we quietly accept road intersections but exhibit great outrage over a nuclear powerplant.
As Thomas has noted, there are measurable adverse effects on the public health due to the mining and burning of coal (which in the U.S. accounts for about half of our electrical power), and these effexts exceed, by a wide margin, those associated with the equivalent amount of nuclear power. One would think that - even ignoring the potential for atmospheric warming which is a fashionable fear these days - the choice for nuclear power would be an easy one. It is not, and that illustrates the irrationality of the public debate on these issues.
imo what has not (never ?) been figured into the equation is the question of eventual disposal of nuclear waste . it's all being buried quite nicely right now. from what i understand , those "burial sites " cannot be considered safe in eternity . so what happens down the road to those burial sites ?(one of the major sites is pretty close to toronto and he great lakes - not exactly a safe "burial site" imo).
what i find rather disturbing is , that science has not been able to come up with a safe disposal method (but i'm not a scientist - so what do i know).
btw i recent article in "business week" stated that coal-burning power plants are now operating in the united states in a "close loop system" that elimanates polluting exhaust gases , and since much of the coal now comes from surface mining , mining disasters should be pretty rare ? hbg
georgeob1 wrote:The real question here is, How do you evaluate alternatives, all of which involve some adverse side effects, in situations in which we must make a choice?
quite right george.
we could use reason logic science technology and mathematics
or split open and examine the entrails of some poor animal
or not exacly split open, but go for our own gut instincts
or flip a coin
or pray
or give up.
I have no doubt we should re-evaluate the benefits of human sacrifice, especially those who dangle crystals.
blatham wrote:How do you calculate suffering?
By observing, through natural experiments, people's willingness to bear it. I don't know what the results are for suffering, but there is an ample "value of life" literature that measures how highly people value their lives, judging by their willingness to risk it. Their results vary broadly, but $5 million approximates the average result. Steve Landsburg describes the Methodology in
this Slate article.
blatham wrote:There's the classic case of GM knowing that some percentage of a particular auto would burst into flames in a rear end collision, and they could calculate the probabilities of how much they would have to pay in damages resulting from suits related to those deaths and mutilations. The calculation found that these costs were likely to be less than the cost related to recall and repair. So they let the folks burn.
I don't remember such a case at GM. Is it possible you are talking about the
Ford Pinto? I agree their engineering decision was unethical -- and the methodology Landsburg describes would have agreed with you too. The problem is that Ford used a value for the value of a life that was a fraction of the experimental result from the "value of life" literature. They used $200,000 in 1970, corresponding to about $900,000 today.
But apart from using the wrong number, I have no problem with their methodology. What course of action would you suggest instead, and why do you think it is better than Ford's would have been if they had used the correct value?
blatham wrote: But what if you had an uncle living in Bhopal, thomas?
After the fact, I would be very angry at Union Carbide, as you might expect. Before the fact, my uncle may well not have lived to be killed in the explosion if Union Carbide's chemical plant hadn't saved him from the back-breaking toil of manual labor in the fields of India. I did not research the pertinent facts about the Bhopal accident, and it is possible that researching them would make me agree with you. But it is just as possible that I might conclude this deadly risk was a lesser evil than the other.
blatham wrote:It really seems like the classic indictment of a teenager's risk-taking. They don't know how bad it can be until it happens to them, though it might be too late.
Everyone has their favorite precedent. As for myself, your fears remind me of some medical experts in Germany during the 1830s. They warned people to stay away from a hazardous new technology called "the railroad". Hazardous, because speeds as high as 40 were probably hazardous to the passengers' health, especially since nobody had ever measured the stress on the human body at speeds as high as 40 mph.
hamburger wrote:from what i understand , those "burial sites " cannot be considered safe in eternity . so what happens down the road to those burial sites ?
Hamburger: Did you read
georgeob1's overview of nuclear waste and how to dispose of it?
It may well be that those burial sites cannot be considered safe in eternity. But I doubt that's the appropriate standard to require. Radioactive waste that radiates 'for eternity' only radiates very weakly, or else it run out of radiation to emit much sooner. As George points out, the stuff that emits very dangerous levels of radiation has a half-life of years, maybe decades. It does not have a half-life of centuries or even millenia.
The earth itself isn't safe for eternity. If I recall correctly the probability that the earth will be hit by an asteroid of several kilometers diameter (enough to wipe out life) sometime over the next 400,000 years is about 10 percent. (This issue came up in the debate over the geostability of the Yucca Mountain Repository in the context of a dispute over whether the confidence with which the 400,000 year geostability of that site was assured to one part in ten thousand or one hundred thousand. )
georgeob1 wrote:Is the Americium fissionable in a fast neutron process?
Yes.
It is also fissionable in an epithermal neutron process, which is sort if between "fast" and "slow". (That is relevant for molten salt reactors.)
There is also a proposed system where a particle accelerator creates a huge flux of thermal neutrons, which keep building onto a nucleus until it turns into something with a short half life and splits spontaneously. This is supposed to produce power in excess of what it takes to run the accelerator.
georgeob1 wrote:Are there any operational (as opposed to experimental plants) fast neutron reactors in operation anywhere?
There is one in Russia (Beloyarsk unit 3).
There was another one in Kazakhstan that closed in 1999. It had run for 27 years.
The Russians are building another one (Beloyarsk unit 4).
Thomas wrote:georgeob1 wrote: Not true. There are a host of long-lived nuclides produced by fission that are not themselves suitable as fuel in a secondary process.
While Oralloy did say "nuclear" rectors, perhaps what he meant was a different sort of devices that made their way through the press a couple of months ago. These devices are basically long-lived batteries. They exploit the fact that radioactive materials are usually a few degrees warmer than their surroundings. They use some radioactive, non-fissionable element (Radium? not sure), plug it into a heat pump or Peltier element, and generate electricity with it, usually for some kind of spy equipment that has to work autonomously. I don't want to put words in Oralloy's mouth, but maybe that's what he means.
No, what I meant is what you might call a "fast breeder reactor".
Thomas wrote:I tried to find the percentage of radioactive waste that is actually liquid, but didn't succeed. Do you have a figure, George?
I don't know the percentage, but the liquid in question is what would be left after the spent fuel was processed to remove some of the more valuable isotopes.
If we plan to extract all the fissionable isotopes for use as fuel, all of the currently-solid spent reactor fuel will have to end up as liquid.
Steve (as 41oo) wrote:>Vitrification (turning into glass) was heralded as the answer for high level nuclear waste. But as far as I'm aware its never really worked very well. The spent fuel rods from the reactor are basically dissolved in nitric acid and from that solution the plutonium and any other fissile materials they might be interested in is separated by chemical means. This of course leaves behind a very unpleasant concentrated radioactive soup. This is where vitrification was going to render it relatively harmless, but as far as I am aware most of the high level waste is still in liquid form...although thats just a guess.
I know most of the liquid waste hasn't been vitrified yet, but I hadn't heard that there was any problem with the vitrification process.
My concern about vitrification is whether it is easily reversible if we decide we want some of those isotopes in the future.
blatham wrote:Foolish boys. One can fear the consequences of global warming and also fear the consequences of another nuclear plant catastrophe.
If the plant is properly designed, there is no risk of a Chernobyl-like incident.
georgeob1 wrote:However there are some serious control issues in the physics of plant design. Most of the world's nuclear plants are water cooled and moderated using thermal neutrons to initiate fission of U-235. I believe the latest designs are gas-cooled variants with improved fuel cladding, permitting much higher operating temperatures and higher Carnot efficiencies.
There are a number of modernized water-cooled reactors and high-temperature gas-cooled reactors that are available:
http://www.uic.com.au/nip16.htm
And five of the six future reactor technologies that are being developed are capable of fast or epithermal neutron speeds:
Google search: nuclear "generation iv"
I had discounted fast breeder reactors, a decades old technology, but one which I doubt would ever gain approval due to the proliferation problem. Given that we haven't licensed a nuclear powerplant for over 20 years, I am very skeptical of any new technology getting more than tentative or experimental approval. I am also skeptical about new fuel nuclides. Many, such as Americium, present serious, largely unexplored metallurgical problems for cladding materials, not to mention the cost of handling them. Fuel reprocessing in the U.S. for commercial plants is against the law, thanks to Jimmy Carter.
There are however a number of incremental improvements on already approved gas cooled designs that offer both safety (no cold water accident potential) and efficiency (higher operating temperatures) gains that will make them attractive for the risk capital required to build and license them. Even with the most conservative approach, it is virtually impossible to accurately forecast how long it will take to get a license. The sad examples of Shoreham in Long Island, Rancho Seco in California (and WPPS in the Northwest) have effectively deterred any investment in these technologies or in new plants for two decades. That won't change easily.
I'm not sure if the following two statements are entirely consistent. If they aren't could you perhaps resolve this, oralloy and georgeob1? You seem both have evidently investigated this much more carefully than I have.
oralloy wrote:I don't know the percentage, but the liquid in question is what would be left after the spent fuel was processed to remove some of the more valuable isotopes.
If we plan to extract all the fissionable isotopes for use as fuel, all of the currently-solid spent reactor fuel will have to end up as liquid.
In Post 1729298, georgeob1 wrote:Generally the economics of disposal strongly favor concentrating the waste by separating the innocuous components from the radioactive ones. This usually means separating the solid component from any waste generated in liquid form. The principal liquid wastes generated are cleaning solvents and, in the case of fuel reprocessing plants, the nitric acid solution into which the spent fuel is dissolved and from which plutonium and other useful nuclides are precipitated. This latter is one of the principal legacy problems at the Hanford Washington site where it was simply stored in large buried tanks and with little control of just what went in them.
If, as George says, "the economics of disposal strongly favor concentrating the waste", wouldn't it be economical to distill the nitric acid away and recover the spent fuel dissolved in it? In that case, the spent fuel would not "end up as liquid", as oralloy put it.
I would also like more explanation on those points.
But there is a more fundamental point about nuclear power which has hampered its development right from the start. The plain fact is that the mother and father of nuclear power is nuclear weapons. Right from the start it was obvious that a nuclear pile (reactor) would produce large amounts of useful heat energy. But thats not the reason they were built. They were built to produce plutonium for weapons, the heat was just wasted. Of course later designs utilised the heat and called themselves nuclear power stations. But the early ones were not really power stations at all, they were plutonium plants. But now we dont want the byproduct of uranium fission, we actually want the energy it generates. There is a chance in my view that the lastest reactor designs coupled and a more realistic (and healthier) view about what nuclear power is all about i.e producing large amounts of zero carbon emission energy offers the chance of a fresh start. Necessity is the mother of invention. During WW2 we needed plutonium. Now we need clean energy. I'm sure nuclear power will play a significant role in that.
Regarding both climate change and nuclear power, this really should be the last word
http://www.guardian.co.uk/nuclear/article/0,2763,1668592,00.html
from the Guardian article...the
UK's chief scientic advisor to the government (please note those credentials) says
Quote:Even a year ago climate change was still reported as a controversial issue. Was the world really warming? If so, was it just a natural change, or could it truly be attributed to human activities? There were just enough gaps in the scientific arguments to give climate sceptics room to manoeuvre. But since then every one of the sceptics' arguments has been shot down by new findings. The scientists who warned of impending climate change have been vindicated (though the consequences are likely to be so serious that I imagine all of them would rather have been proved wrong)
oralloy wrote:blatham wrote:Foolish boys. One can fear the consequences of global warming and also fear the consequences of another nuclear plant catastrophe.
If the plant is properly designed, there is no risk of a Chernobyl-like incident.
An optimistic take on the perfection of humans. But if your point is that liklihoods of big bad things happening are very small, I don't have any information to argue against you.
blatham wrote: oralloy wrote:If the plant is properly designed, there is no risk of a Chernobyl-like incident.
An optimistic take on the perfection of humans.
I think it's rather an optimistic take on the kind of reactor designs that is likely to be implemented under democratic institutions. Chernobyl reflects a failure of dictatorial government secrecy more than one of nuclear energy. Did you follow the story of the chemical hazard in China two weeks ago? It is chemical, not nuclear, but like Chernobyl the hazard was created by a government with no incentive to get things right, and every incentive and power to shut people up for complaining about it beforehand, and reporting about the accident realistically after it happened.
First Steve's points -- It would be interesting to review a selection of the Guardian's anti nuclear stories and editorials over the past few decades in juxtaposition to the cited piece by "Sir David King". One can be bemused by the lack of shame exhibited by such self-important, authoritarian sources (the Guardian) when, after decades of being dead wrong, they announce their new "discovery", but the discerning reader should not be deceived. It was also interesting that Sir David devoted about 20% of his article to defending himself from the expected criticisms from his real constituency - the loonie "Greens". I was quite amused by the bone he chose to throw them: while he favors government subsidies for wind, wave, and solar power, and government mandates for the design of vehicles and appliances, he stedfastly opposed government subsidies for nuclear power. What lofty moral principles are evident here ! What a principled public figure - incorruptable and unwilling to bend in the slightest to public fantasy! What crap !
Second - Thomas' point and questions. It may be useful here to distinguish between the waste generated by nuclear power stations and the processes by which fissionable fuel is produced, concentrated and assembled in forms suitable for new or refuelled reactors. An operating plant discharges small quantities of reactor coolant (water), which, as I noted earlier, is quite harmless after suspended corrosion products are removed by ion exchange annd carbon filtration, These plants also produce relatively small quantities of spent carbon and the variious resins used in the ion exchangers. As fuel elements are replaced more or less continuously in commercial plants (and just once in the life of the ship in Navy plants), high level waste consisting of the spent fuel rods and their metallic cladding is generated. These have been "temporarily" stored in pools, generally on or near the plant from which they came for over twenty-five years. On a few occasiuons through neglect corrosion has exposed the fuel in rods stored in this manner. This contaminates the water in the pools with a highly radioactive sludge. Since the water is a very effective shield, this generally presents no problem (as long as the pool doesn't leak). However it requires a fairly expensive process for cleaning the water and isolating the long-lived nuclides that have entered it - more or less like the processes used to clean the relatively harmless spent coolant from the reactors.
Finally these plants produce a relatively much larger quantity of very slightly contaminated clothing, tools, etc. : articles whose low replacement cost makes cleaning them - or even measuring the amount and type oif contamination in them to select out the (large) harmless fraction - an impractical option. They are treated as low level wastes and buried in landfills in the deserts of Utah. These constitute, by far, the greates volume of waste generated by these plants.
When major plant components are removed and replaced any contaminated surfaces are cleaned with mild acids and solvents to remove and concentrate their surface contamination. The structural steels and various alloys (lots of Monel and Inconel) remaining are generally treated as low level waste (which is a shame, because their contamination levels are generally very low). When the plant is finally shut down this process is repeated on a much larger scale, and involving more heavily contaminated components, particularly the massive reactor vessels. In all of this liquid wastes are indeed treated as Thomas suggests.
The proiduction and separation of fisdsionable fuels involves use of liquid acids and corrosive gases which present their own problems.. The enriched uranium is processed and stored in gaseous form -- Uranium hexaflouride. (The U.S. has thousands of tons of it stored at various locations in Ohio, Kentucky, and Tennissee.) The production of plutonium for weapons iinvolves dissolving the spent fuel matrix entire in concentrated nitric acid and then selectively precipitating out the desired nuclides or chemical constituents. The resulting waste is a concentrated nitric acid solution containing high-level actinide wastes in a mixture with the various additives used as precipitants.
In the early days of our weapons programs we were in a hurry and our early processes weren't particularly efficient. There are, at the Hanford Washington site, about 250 large (million gallon) buried tanks still holding these wastes after 50 years. Radiation levels limit intrusions to robotic devices, and the passage of time has yielded odd mixtures and colloidal suspensions in the tanks, some of which generate a good deal of heat. It's an expensive chemical and actinide graveyard, but it is stable and not mobile. We produced and separated well over a hundred tons of plutonium in this manner, and don't need any more.
Plutonium stocks do need periodic reprocessing to remove the decay products, particularly Americium, which alter its physical properties and, because Americium emits a very high energy photon, adds considerably to the hazards of handling it (plutonium is an alpha emitter, requiring very little shielding during manufacture). This reprocessing is done on a much smaller scale than the original manufacture, and the treatment of liquid wastes in it is far better than what was done 40 years ago. Britain, France, Russia, and the U.S. operate fairly large scale reprocessing oiperations along these lines. The new reactor designs suggested by Oralloy would require larger scale operations of this type to produce and separate the new fuels required for their operation.
