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Microbes for Bioremediation
The San Francisco Chronicle has a piece discussing current efforts to clean up nuclear waste sites with microbes. Current treatment procedures generally involve pumping out the contaminated groundwater, filtering it, and pumping it back, which is rather expensive.
I for one welcome our new microbe overlords!
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Is this the intro to another movie?
I can see it now: radioactive germs bite a kid and he turns into a super human spiderman/hulk thing.
Great.
is anybody else reminded of Zodiac? This may turn out to be that bad of a fiasco if rushed. I can only hope for the best.
why does the porridge bird lay his eggs in the air?
I can think of cooler stuff to do with microbes - like in restauraunts, have lots of microbes at the bottom of a special trash can to eat away grease (McDonalds would love that.)
Or even a microbe spray to degrease stuff; cool, huh? No more wiping down.
Also cool would be microbes in my toilet, to eat my shit (but not die.)
Of course, I do wonder what they'd do while they weren't eating shit or grease or whatever, but who cares about that, they're cool!
Sig & Below
Yuck Fou
But the real question is, how well does it work? Can this convert a nuclear waste zone into a habitable zone? This is great news for the environmentalists.
YAFIRL (Yet another Free iPods referral link)
it starts with the microbes 'consuming' uranium... ok, what does the microbe do with it? it's still radioactive and now your microbe is also!
then i get to the part where the microbe is taking water based uranium and making a solid form. ok.
don't you still have to dig this stuff up? wouldn't the 'solid' form break down after a while and still have the problem? and wouldn't the solid form still have the same amount of radioactivity?
it looks like it makes it easier to get it out of soil, but you still have to dig it up and process it out?
eric
The waste ate its way down into layers of saprolite, a claylike rock, so that more than 99 percent of it is deep in the soil, he said.
Maybe this technology could be put to other uses. for example, what if we used old nuclear waste for drilling deep within the earth. We could pour some in the hole, and then microbe it when it stopped being effective. lather, rinse, repeat.
1. Pour nuclear waste into ground making a really really deep hole.
2. Clean up hole with microbes.
3. ????
4. Profit!
Under capitalism man exploits man. Under communism it's the other way around.
They have GE Bacteria that will eat oil, to be used in oil spills. These however are not being used outside of labs, because of the consern of "What will happen when the the oil is gone? What are they going to do? Die, or find something else?" So I would think the same with will happen.
a mountain of radioactive and toxic dirt 2,000 times larger than Egypt's Great Pyramid at Giza.
That's all very well and good, but I want to know how many Libraries of Congress that is.
Nanotechnology will practicaly do the same thing in a much more efficient way. Imagine, the little robots could built a small city with nuclear waste. Take a few carbon atoms lying around and built some houses. Then build a nuclear plant. Use the depleated uranium to make rods. Use thoses rods in the nuclear plant to provide power to the freshly assembled houses. Tada! City in a Box (Tm)
YAFIRL (Yet another Free iPods referral link)
Skinner: Well, I was wrong. The lizards are a godsend.
Lisa: But isn't that a bit short-sighted? What happens when we're overrun by lizards?
Skinner: No problem. We simply release wave after wave of Chinese needle snakes. They'll wipe out the lizards.
Lisa: But aren't the snakes even worse?
Skinner: Yes, but we're prepared for that. We've lined up a fabulous type of gorilla that thrives on snake meat.
Lisa: But then we're stuck with gorillas!
Skinner: No, that's the beautiful part. When wintertime rolls around, the gorillas simply freeze to death.
There's a Mercedes gap too. I want one and can't afford one, but it's not government's job to do anything about it.
Nuclear energy IS clean. The cost (both in dollars and human years lost) of operating a coal-fired plant is less than that of a nuclear plant. Your fallacy is in seeing the mistakes committed decades ago by an inexperienced (by today's standards) industrial and scientific community. Applying the same sort logic that you use to the space program would suggest that 90% of all rockets never reach even reach an an altitude of one mile, since your logic includes failures encountered early in the history of the technology. Applying your logic to the computer industry suggests that there's a global market for maybe 5 computers (at one point in history, there WAS a market for only five computers).
Technology progresses; I'd think a slashdot geek would realize this. Nuclear energy technology is no different.
I'd also point out that if you exclude insanely stupid events like the detonation of nuclear bombs, more people in the USA die in a year from car accidents than have ever died world-wide from radiation exposure. Americans (or perhaps humans in general) do a really lousy job in assessing risk. And don't get me started on the tragedy of SUVs (sure, you're more safe in your SUV...it's because of conservation of momentum. Never mind the poor sod you run into, because youre life is obviously more valuable than his). Anyway...never let good science get in the way of politics and mob manipulation. We fear radiation and throw ourselves under the juggernaut of the oil industry.
I wonder how is it that the ionizing radiation doesn't manage to kill off these microbes before they can do their job? A typical gamma ray goes for 5 MeV, whereas a typical ionization energy is only at 15-20 eV. Interfering with chemical reactions necessary to life most definitely. Mutation and more likely outright killing of these organisms.
How do they survive?
Qu'on me donne six lignes écrites de la main du plus honnête homme, j'y trouverai de quoi le faire pendre.
The dispersal rate of airborne pollutants is much higher than the rate at which nuclear waste is dispersed. This means that after a short time the waste which is released from a fossil fuel power plant is reduced to neglible levels when considering pollutant ppm. Nuclear waste degrades much more slowly and cannot be effectively dispersed in the atmosphere.
You can bet that I am not in favor of the prolonged use of fossil fuels as a primary power source. However, this does not mean that I must automatically subscribe to nuclear power as a sustainable and safe method of power generation.
This actually has something in common with the Stephenson novel "Zodiac". Everyone should go read it. You can buy it here
Slow down a piece there cowboy. As its clearly stated in the article to which you refer, Oak Ridge was making military weapons. Also the waste was dumped into pits. This particular issue has *nothing* to do with waste planning at all. The ignorance about the material at the time and, probably, expediency led to such haphazard disposal. Not to mention the nitric acid.
As for your non-sequitur to 'anti-environmentalists', which by your tone i assume means anyone who would advocate nuclear power, All energy conversion technologies that use consumables have an output of something. I have seen a lot of knee jerking on nuclear, some valid, and a lot that isn't. You have to pick your poison if you want the juice for your internet.
Current treatment procedures generally involve pumping out the contaminated groundwater, filtering it, and pumping it back, which is rather expensive.
I want these guys to use whatever works the best. Microbes, filtering, shooting it off into the sun...
Really...this is one of the places where is has to be done right. Screw the expense.
Unfortunately, profits and stockholders will get in the way of doing it right.
OK, enough of the silly "Microbes will take over" and Frankenfood-inspired comments.
Having read the article, it seems like a good way to precipitate soluble U ions as U oxides, or complex uranyl compounds. It appears to offer a way to mitigate impacts upon human health and the environment by precipitating U ions traveling in ground water so they do not discharge to surface water or pumped by potable wells.
Bioremediation is nothing new. It works well with chlorinated solvents (PCE and TCE), especially in reduced, iron-rich ground water. The caveat for those compounds is, however, that they break down only so far, often leaving vinyl chloride -- a demonstrated carcinogen -- as the final step before there is not enough energy for them to survive by reductive dehalogenation. Basically, the microbes die becuase they do not have a source of "food."
The same goes for aerobic microbes, like these appear to be; they combine dissolved metals with oxygen to precipitate them. That gets even more expensive, because you have to maintain the proper redox level by introducing O2 with hydrogen peroxide or ozone. It's expensive and prone to mechanical failure or the vagaries of the subsurface.
These microbes may die out once their source of "food" depletes. However, the by-products should be assessed before they try to use this in a live environment, because sometimes the cure can be worse than the problem. There is also no economic analysis for this research, but it is likely way to early to determine how much it would cost to implement. It may be more reliable and cheaper to precipitate dissolved U by simply pumping a lot of oxygen into the ground water.
It is a widely held misconception that exposure to a radioactive substance will 'mutate' normal objects into some radioactive thing. This is almost exclusively untrue. The exception is when material are exposed over long periods to *hard* radiation you may have some amount of nuclear interaction with the decay products of the original substance. Flying off neutrons is what causes the fission chain reaction after all. However, Uranium nuclei are very large, and as they are naturally radioactive, unstable on their own. Also recall that atoms are mostly empty space, nuclear reactions in otherwise stable materials aren't terribly common.
I am not a nuclear physicist. But i can call a couple of friends if i need to:)
Well, I am a pool operator by trade, lifeguard by profession, and the ways to filter water ALWAYS contaminate. If they use sand filters, you get a lot of radioactive sand. If you use cartridge filters, you have alot of radioactive paper. Diatomaceous Earth filters are probably out of the question. There are probably others. I assume that by filtering, they are trying to transfer the radioactivity to the filter media. I don't know the specifics, but the process is either designed so that A) Environmentalists will quit their bitching about the immediate threat to the environment,or B) The filters can lose their dangerous radiation levels afetr a few days, so long term disposal is not an issue. I am pretty sure the filter plan just deals with the immediate threat that irradiated ground water is dangerous, but relies on careful, long-term storage for the objects doing the cleaning.
But yeah, I probably was wrong about it creating more waste water, although the water will never be *truly* clean again. Filters can't garuntee that. They can just specify a percent that leaves only a safe amount of radiation.
The story sounds like its using a method that the copper industry has been using for years, expect in this case with microbes that crave uranium instead if copper. They don't eat or destroy the uranium, just chemically transform it into insoluble forms that can be easily filtered out of groundwater.
Biological heap leaching is an inexpensive way to extract the metal from low-grade ores where copper is bound in a sulfide matrix. As the microbes chew up the ore, which has been treated with sulfuric acid to encourage them, the copper is released and concentrated in a solution that flows into a catch basin. The metal is extracted, and the acid solution is recycled.
Got that right. As long as the waste stream is managed well, it is much cleaner. Coal pumps enormous amounts of SO4 and NO3 into the air as acid precipitation and also offers plenty mercury and other hazardous metals. Unfortunately, it is also more expensive. Maintaining and disposing of that waste stream is tough, especially under the regulatory system. Even if there were some deregulation, it would not be cheap to manage the by-products. And don't forget: more Americans have died in Ted Kennedy's car than in radiation-related commercial nuclear energy generation accidents. It sounds like the owners of existing nuclear plants are planning to refurbish them rather than decommission. It appears it will be cheaper to upgrade ond operate the assets rather than maintain them as relics for which there is no disposal alternative.
I can appreciate where you are coming from. I don't think that all pro-nuke/anti-environment folks are out to wipe out humanity in some evil scheme (though you'd think that was all they were interested in).
Basically we are all in this boat together and we've got to do what we can to keep it afloat. So you and me, we're on the same side, we're just arguing over implementation details. It is a far cry from us arguing over whether the correct alternative energy source ought to be nuclear or otherwise to the neocon opinion that all is right with the world and environmental action need not be taken immediately.
In the end we need to weigh the risks, as you pointed out. I don't have the stomach for the risks posed by nuclear power, and so I will continue with the NIMBY (think globally, act locally) opinions that I've got. Too often this lack of weighing the risks of things carries over into other parts of our daily lives, whether it is something comples like choosing to fluoridate water supplies instead of trying to prevent cancer in population centers or something simpler like deciding between the simple but feature-lacking vi and the buggy but feature-laden Emacs.
The bacteria doesn't get rid of the radiation, just makes the radioactive slush insoluble so that they can collect it and deal with it with less cost. It's a great idea.
I'm just hoping that some genious comes up with a safe way to speed up the nuclear decomposition so that the material stabilizes into non-radioactive elements. That will be a breakthrough!
--==-- I've found Karma to be a relative thing... Ya know, the kind you invite to Christmas...
Pros:
Cons:
Could this be the cure to the first of the two cons?
I believe the gist of the article is that the bacteria are able to turn a SOLUABLE form of uranium into a NON_SOLUABLE form. Therefor it is less ilkely to be dissolved (or far much less of it) into the groundwater and migrate to potable (drinkable) water suplies. Or You could "wash" the soil and introduce the bacteria into the water and have them "filter it out" , thereby purifying the water. It's been done with petroleum eating bacteria on oil spills, so why not nuke wastes. I even remember way back when I was taking some bacterial engineering classes, that some bacteria were selective enough to distinguish different ISOTOPES of elements - not 100% selective and therefore probably not good enough for nuke purification schemes..
..........FULL STOP.
Where can I get some of this amazing bacteria? My bedroom had to be quarantined off two months ago when I attempted to see if I could use uranium to overclock my Pentium 2, and I forget what color the carpet is... *sniff*
...to deal with the nuculear waste products left behind by my roommates!
20 mil and I will! Learn Esperanto with 20M others.
There is a total revolution going on in all food production worldwide through the use of a class of microogranisms known as Purple Non-Sulfur Bacterias (PNSB's). The work was pioneered by a Japanese scientist who did research for 20 years to perfect a synergistic formula of different microogranisms that work together, including the PNSB's, lactic acid bacteria, and yeasts.
Almost all organic farms are now spraying soil with this solution. Additionally, people who raise animals are feeding it to their animals. Not just organic farmers, but even traditional mass production farms in the US because it lets them *totally eliminate anti-biotics and hormones* due the increased nutrition the microbes afford creates who consume them.
Human beings are actually supplementing with these as well. It is very popular in Japan and South Korea, and is becoming popular in America.
The PNSB's act as reducing agents, ie, antioxidants. So, the break things down by creating antioxidants that eliminate the material over time, as opposed to oxidizing bacteria that makes things putrify and rot. The reduction ability of the PNSB's is why the US military uses the same exact solution as the farmers and humans do, to break down toxic waste from weapons and nuclear power plants.
Have a look at:
http://www.rawpaleodiet.org/em/
http://www.antioxbew.com/
My DVD and Game Collection Tracking L
As I've learned from Saturday morning television, there has been an answer for this for years. You combine the power of the five rings to form Captain Planet, and he cleans up the nuclear waste and puts the perpetrators in jail. Sheesh, you'd think these so-called "intelligent" scientists could be bothered to turn on the TV every once in an while.
Radioactivity doesn't just go away... it is not a chemical reaction, but physical instability in the nucleus of the uranium.. This may chemically break down uranium... but still. the microbes will be exposed to toxic amounts of radiation (by human standards). This is what is dangerous about uranium... where as it may be toxic as a chemical it is also radioactively toxic. the microbes might be able to break it all down into uranite. but it seems they are only dealing w/ microbes as a way to chemcially treat stable uranium...
still doesn't solve the question of radioactive waste does it?
This was done before on a test site near the Hanford nuclear facility in Washington (state), US. Only with that, they used the population of microbes already in the area that needed methane in order to properly metabolize the contaminated elements. They pumped a continuous stream of methane into the ground to help the microbes thrive and do their job, and when finished simply turned it off and let them return to natural levels.
A simple control mechanism such as that, especially using elements already found in nature, will be far more acceptable to the general public (fed on many a recent techno-thriller) as well as the tin-foil-beanie crowd (though just barely).
Any spoon would be too big.
Oak ridge has tought us very many things, of those nuclear power is unclean is not one of them.
First, the ecology of the area is quite robust. A lot of wildlife - on the road into the lab deer are populated enough that nearly two are killed every week crossing the road, turkey's have become so overpopulated that they are opening the preservation up for hunting (previously only animals large enough to damage property were allowed to hunt), and Melton Hill lake is swimable and the fish are edible (above a certain point - though that point is for bacterial not nuclear).
Also Oak ridges issue, as stated in the article, is from the 40's and 50's when they thought that putting the waste in barrels at the bottom of a pond was good enough, or pouring stuff on the ground was good. As far as I know that is not standard practice today. This has to do with nuclear bomb production back in the early days, it's not even relevent to current weapons research (which is produces much worse waste than a power plant).
Oak Risge still produces some of the most radioactive stuff in the world (at the HFIR http://www.ornl.gov/hfir/hfirhome.html ) and does so qutie safely - I've looked in the holding tank at stuff glowing quite brightly (medical isotopes being produced) so it is definatly on going production.
Modern plants are quite efficient and do not produce near the waste that they used to - in fact, a large portion of thier material is recyclable back into the plant or into other useful materials. Coal is MUCH worse for the environment than nuclear power. Total impact - with materials cost, waste, and output - nuclear plants are one of, if not the best, solutions for power in all geographical areas.
------- Sorry about the spelling, I suffer from two problems. Dyslexia makes it difficult to spell well, lazy makes it
This story was on SF Gate 2 weeks ago and I submitted it that day. The weird thing is that my submission was and still is listed as accepted but the story was never posted. Now it finally shows up.
:)
Maybe the microbes had to chew through some bowel obstructions to allow the accepted stories to clear through.
~~~~~~~
"You are not remembered for doing what is expected of you." - Atul Chitnis
I'd be a little surprised if the concern with the uranium concentration is really the radiation; perhaps at the Oak Ridge, but almost certainly not at the mine tailings. If the concentration of non-refined U is so high radiation becomes a concern, you're more likely to die due to the fact uranium is poisonous in the same sense mercury and arsenic are poisonous. In any case, U isn't a good thing to have in the water supply.
As has already been stated, Oak Ridge was a VERY unique situation.... in Dr. Richard Feynman's The Pleasure of Finding Things Out, he recalls that Oak Ridge didn't even know what they were doing until well into the project, when Los Alamos got authorization to tell them.
Moreover, nuclear energy is clean... and I'm certainly not an anti-environmentalist. As long as it is handled properly, nuclear energy is a very safe and efficient (not to mention cool) method for producing electricity.
[Note: calling nuclear energy 'cool' greatly adds to my credibility]
Maybe if people stopped trying to generate a stigma around nuclear power plants we could spend our efforts making them safer and more efficient, rather than simply fighting for their existence. Unfortunately, the average Joe knows only three things about nuclear energy:
1. It makes bombs go boom
2. It's baaaaad and kills everyone
2. It's just like in the movies
Nuclear energy IS clean.
And don't forget that burning coal high in uranium can release into the atmosphere as much radiation every day as was released by the Three Mile Island leak. Just look to the big coal plant in central Utah for an example.
Visit Jonesblog and say hello.
>If Oak Ridge has taught us anything, it's that even the best laid plans can end up destroying the ecology of an area.
Extending this logic, sitting in a parked car on your driveway for your entire lifetime will mean that you will have at least 2 or 3 car accidents.
Perhaps you should read something about the world's safest nuclear reactors; reactors so safe there are no deaths as a direct cause of it being a nuclear reactor? Even the Sierra Club doesn't seem to have any serious dirt on this reactor, apart from weapons sales blunders. Search for it yourself!
Hmmmm, zero deaths vs. many. Hard to decide. Perhaps if I were anti-people it'd be easier. You aren't anti-people, are you?
If you could be told what you can see or read, then it follows that you could be told what to say or think - BoC
Same deal with antibiotics, or any other organism and the cruel cruel world. That's how life works -- more organisms are born they can survive, the ones with bad mutations don't survive under "normal" conditions, but when conditions change, normal and abnormal swap places, the ones that used to live die, and some of the ones that used to die now live.
Infuriate left and right
Right. You get a radioactive filter, and clean water. You can then box and bury the filter. Its difficult to box and bury a lake.
Both on the microbes themselves (who may mutate or develop into something quite different) and the containment of the microbes themselves? What happens if they escape into an uncontrolled environment (I'm thinking on the lines of the killer bees)? The problem is alternate _safe_ sources of energy not microbes to cleanup the mess. Why not put this much effort into wind/solar technology and eliminate the need for such stuff to begin with?
http://www.dtra.mil/news/fact/nw_hnforce.html
They were "airburst" nukes. That means that there isn't as much contaminated material as there would be if the fireball contacted the earth.
With an airburst, the contamination can be washed away. Even though this only moves the residual contamination to another area.
If this had been a groundburst, there would have been a lot more radiation contamination to clean up.
Groundwater is poluted by engine oil, petrol, and jp5 jet fuel leaking from storage tanks in all 50 states and every country on the globe.
/.
Hydrocarbon groundwater pollution is a much more widespread problem than soluable uranium. People with water wells 10 miles from Miami International Airport (MIA) can smell JP5 jet fuel in their well water. This is clear cut opportunity for bioremediation. People store and therefore leak hydrocarbons where they can and do use them.
As population and water needs rise, and supply dwindles, the US Federal Government has been forced to act. In the 1990's, to reduce the hydrocarbon pollution of groundwater, the US Government forced every gas station (petrol filling station) to dig up every storage tank and the soils surrounding the tank, and leave the dirt in piles to "off gas" the hydro carbons for months. And after off gassing, station owners had to replace the tanks with less leaky modern tanks.
Because water is essential for life, yet difficult to move economically, there will be increased border wars and politcal fights to control rivers and aquafers. We are watching a war for control of the oil rich country of Iraq. We will see similar fights and politcal disputes for control of rivers and dams on many international rivers. We will also see a marked rise in the trade of grain, one of the few water intensive commodities that can be traded economically.
All of this spells a golden opportunity for bioremediation of hydrocarbons, to help cities, farms, and countries to improve supply of potable water.
Mac refugee, paper MCSE, Linux wanna be
and first person to mention knoppix on
I've lived in Oak Ridge. Very nice area...very clean for Eastern Tennessee standards. Lots of trees, rivers, etc. Everything was very professional, and I never heard of any problems regarding radioactive waste. Heck, even their speed limit signs have kilometers per hour on them!
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In contrast, travel 10 miles outside of Oak Ridge back in the redneck hills, and you'll see all sorts of trash. Empty motor oil bottles, dead batteries, lighter fluid containers, etc, all sitting in the middle of streams. Seeing that, the *last* thing you'll ever think is "Did Oak Ridge dump a few pounds of radioactive waste in the ground?" Worst of all, these redneck towns still keep their speed limit signs in miles per hour!!!!
By the way, Oak Ridge National Labratory did a very nice study comparing the huge amounts of radioactive emissions from coal power plants compared to nuclear powered plants. Check it out here: http://www.ornl.gov/ORNLReview/rev26-34/text/colm
So do we end up with a bunch or radioactive microbes then? Now you can have nuclear+bioterrorism all rolled in one easy-to-deploy package!!!
The idea was that microbes consume the dissolved uranium (and other nasty elements) and excrete them as insoluble compounds. So the water is clean and you have a pile of solid waste much much smaller than the original volume. You could recycle that or dispose of it (at least more safely than the original method of pouring it into a hole in the ground and forgetting it).
Canadian reactors (Candus) do not use weapon grade plutonium and uranium, but they do produce (concentrate) it, like most reactors in most countries.
Other than the factual errors, youre post is correct :-). Differences in design of reactors can have a big impact of saftey. Any reactor being built today is probably incapable of a full meltdown.
"A language that doesn't affect the way you think about programming, is not worth knowing" - Alan Perlis
Canadian reactors can be used to burn weapons grade plutonium and uranium, if mixed in with their regular fuel (That is a simplification) During the Clinton administration, they wanted to do this to dispose of a bunch of US nukes, but as you say, nobody wanted it shipped anywhere near THEM. There is also the issue of security: A terrorist would LOVE to get his hands on some disassembled nuclear weapons.
But generally, plutonium is not burnt in Candu reactors. They usually run on unenriched uranium. This saves the environment because the enrichment process is very polluting, but it also means more plutonium in the waste. Less waste, but longer lasting.
Another environmentally friendly feature of a Candu reactor is that, rather than having carbon rods to absorb the neutrons and control the chain reacton, the reacton relies on a medium of heavy water, and is controlled that way. To shut down an American reactor, all of the control rods must be fully inserted. But if the reaction has progressed to far, this may not be enough. In a Candu reactor, it can be shut down by draining the heavy water from between the fuel rods. Without the medium to slow the neutrons, the reactron cannot progress. In the event of a catastrophic safety failure, where the system does NOT drain the reactor, the very act of overheating and rupturing the housing would drain the medium away (In theory, it hasn't happened yet, that I know of) thus stopping the reacton.
They are, however, water cooled, so you end up with thermal pollution of the lake you are on. But not radioactive pollution, since the water used to turn the turbines is a closed system, and the external water is only used to cool the steam, which is not sufficantly radioactive to contaminate the coolant water in any appreciable way, AFAIK.
ASCII stupid question, get a stupid ANSI
You said: "Canadian reactors use weapons grade plutonium and uranium, rather than whatever it is that other reactors use (which is how India and Pakistan got their hands on nuclear material -- from nuclear reactors bought from Canada). I remember there was a big fuss during the Clinton administration, because the plutonium and uranamium from a number of decomissioned nuclear weapons was going to be shipped to Canada, and people on both sides of the border weren't too keen on that."
Canadian reactors are not initially fueled with plutonium. They are just not highly enriched (where the fraction of the isotope U-235, which occurs 0.7% naturally, is increased). The consequence of this is that in order to have a self-sustaining chain reaction (criticality), the neutron flux must be higher. This is because the Candu reactor uses slow-fission which utilizes U-235 as a fuel and not U-238. In order for the core to remain critical (where on average one neutron from a fission event goes on to cause another fission vice being absorbed by another nucleus or escaping the boundary of the core) it has to be very large size and have a very high neutron flux (as compared to a more enriched core which could be smaller and have a lower neutron flux and stay critical).
One consequence of a core with a very high neutron flux is that U-238 can absorb a neutron (which is helped because the core utilizes slow fission unlike a nuclear bomb), become U-239, undergo 2 beta decays and form Pu-239. Pu-239 can also undergo fission like U-235 and be used as a fuel (odd numbered atomic mass numbers of very heavy elements will undergo slow fission but even numbers will not). This is one of the reasons why natural uranium and thorium (which would produce U-233) could potentially create more fuel over time in the reactor (as the U-235 is depleted). Since it is much easier to make a nuclear bomb from plutonium than the brute force method of seperating U-235 from natural uranium this is obviously a potential threat for nuclear weapons poliferation around the world if these reactors are sold.
You asked: "So -- as far as environmentally friendliness is concerned, how do the different types of reactors stack up?"
When you think about environmental friendliness there is short term safety (immediate event of casuality) and long term (groundwater and storage of waste) concerns.
In the short term the major concerns are preventing the reactor from breaking and spilling its fission fragments (which is the VERY highly radioactive waste in a reactor compared to everything else which is relatively lowly radioactive), and if it does break, by containing it. Preventing the reactor from breaking is pretty much controlled by good engineering practice of operating it and by competent design. If we've learned anything from the Chernobyl accident, the least of which is that *only* the people who are trained to operate and know the most about the reactor should be allowed to do any test (or any operation for that matter). Once management steps in and decides that they know how to operate the reactor better than the operators themselves, there is a serious problem. Containment is much simpler. You put up several barriers to prevent radioactive fission gasses from escaping. The final one, the most obvious one, is the cement dome that covers nuclear power plants. But other methods of containment are also useful, such as the pebble bed design where each fuel particle is encased in a ceramic sphere that can contain all fission product gases ever produced by that particle. In the worst case accident the particle will not melt or lose any of its ability to hold the gasses. Future reactors will be much safer due to designs like this (in fact the NRC has rated some as requiring "no evacuations under any accident condition", meaning that they don't think a meltdown can occur).
For long term concerns, continuous sampling and monitoring as well as storage of radioactive waste are the concerns. As long as there is
Suddenly, the hairy finger of a familiar monkey tapped me on the shoulder. It was time.--G. T.
What those who speak in praise of the city haven't mentioned is that the swan pond that I'm looking at is surrounded by a fence, that you can't fish anywhere downstream of the labs for miles and miles, and that there are still barrels of STUFF that we don't even know exist buried around the countryside. Sure, on the surface things are fine, but that's because the heavy metals have long since sunken into the earth.
It's not like the situation hasn't gotten infinitely better since the initial mismanagement of the lab (alluded to by a previous poster and by Richard Feynmann's 'The Pleasure of Finding Things Out'). We built an onsite waste management facility, as part of the cleanup led by Bechtel Jacobs. It was a step in the right direction for the lab, as it allows us not only to repair damage already done, but to prevent causing further harm to the environment as research on radioactive materials continues. (side note: we prefer the term 'rare isotope'... It doesn't scare the populace). The cleanup process was not painless, as this proposal by Bechtel Jacobs (the company leading the multi-billion dollar effort) and article from the Knoxville News-Sentinel indicate. We're nearly done, though. Occasionally something surprises us, but the situation's better than it was.
So, on to the article at last... These microbes don't have a huge utility value here, but they have great potential. Chernobyl, anyone? If there's another uncontained meltdown, these little buggers can be deployed almost immediately (via aerosol spray delivered in an overfly by crop dusters) to begin to counteract the fatal seep of irradiated cadmium and contaminated nickel. It's not of use now, but it's a valuable tool to have in our box.
while (!sleep){
sheep++;
}
Well, I think this Slashdot headline is a little misleading, it makes it sound like these microbes are somehow removing radioactive material, which is obviously impossible. You can't change one elemental isotope into another one with any chemical reaction (which means no biological reaction either)
What they're doing is changing one molecule involving uranium (which is water soluble) into another molecule involving uranium (which isn't). Everything stays just as radioactive, but not dissolved in water.
ReadThe ReflectionEngine, a cyberpunk style n