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Disposing Of Nuclear Waste As Nuclear Fuel
Saige writes "Nuclear waste has been a contentious issue, recently culminating with fights in the government over Yucca Mountain in Nevada as a proposed storage site. Well, perhaps there's a better way to deal with nuclear waste -by using it in nuclear reactors. A nuclear scientist at the University of Maryland, has come up with CAESAR, a reactor that runs not on the standard U-235, but on U-238. U-238 makes up most of the fuel rods in current reactors, but doesn't contribute to the reaction, and ends up currently as waste." The Yahoo! story linked from this article doesn't seem to open, but here's a story at The Economist.
...and the link is already slashdotted
ymmv
So. What exactly does the U-238 become after all this? Also, how could the steam be used if these things are reacting, thus producing heat? Wouldn't the steam be affected by the extreme heat?
I'm not trying to sound ignorant, I just know nothing of nuclear physics.
*everything* is Orwellian to cats.
Damnit! I accidentally left the wrong link in the original paragraph. I meant to include the Economist link, but I was submitting this to Plastic.com and Slashdot both, and managed to cut and paste the wrong part from Plastic here... *sigh*
If anyone cares, the link to Plastic wasn't what was intended and can be safely ignored.
"You know your god is man-made when he hates all the same people you do."
(caveat - I haven't had time to read the article yet, so I'm spouting off without much backing to my opinions, except that I live near Rocky Flats...)
Isn't the real "nuclear waste problem" not just the fuel rods, but the kilotons of contaminated building materials, protective clothing, screwdrivers, air ducts, semi-trailer trucks, topsoil, reactor coolant, baseball caps, human remains...
I'm sure this is a great advance for many reasons, but it's barely gonna scratch the surface of how to deal with contaminated material - or am I wrong?
Perfectly Normal Industries
I think the really interesting thing here is that the reactor cannot be used as a breeder. That would make it an excellent candidate to require nations like North Korea to switch to. (If you think that's the way to go. NK is VERY energy poor now that the Russians no longer send oil. 60 Minutes did an excellent piece on them last night.)
All reactors IIRC produce some plutonium, from bombarded U-238 (virtually all Pu is manmade). Breeders produce a lot. The "waste" which is U-235 depleted but plutonium enriched must be further processed to produce weapons-grade material. For 25 years we have banned reprocessing even to the level needed for use as fuel because of the concern is could be stolen and further enriched. Some countries like France and Japan disagree and do reprocess. The scare in Japan last week illustrates the risk. Most people here would agree there' no such thing as perfect security, esp. with the universal hazards of corruption, accident, and incompetence.
Even if the thieves were unable to purify the material, it would make excellent "dirty bomb" material. Pu is not especially radioactive, absent heavy chain reaction, but it is very toxic and dangerous to ingest or inhale where it might lodge and expose sensitive tissue to prolonged damage.
It's a shame nuclear policy is so constrained by weapons issues.
U 238 absorbs nucleons (can't rememebr whether it's neutrons or Alpha particles) and transforms into plutonium. The plutonium is then used as fuel. Isn't the problem with refining 235 out of the 238 that 238 is a neutron absorber so it limits the reaction?
There have been a few test reactors - notably at Douneray in scotland and an experiment in Japan.
Has this guy come up with a hitherto unknown reaction for power generation? Or does nobody on Slashdot remember their basic nuclear physics.
Apologies.....
If they are going to use Radioactive waste as an energy source, more power to them.
This is a great idea, but thanks to the morons in washington, reprocessing spent nuclear fuel to recover useful fuel like plutonium has been illegal in the U.S. since the 1970's because they're paranoid that reprocesses plutonium could fall into the wrong hands and result in nuclear proliferation. So instead, instead of reprocessing the waste and thereby getting many times more energy out of the same amount of mined uranium, they store all that stuff underground. Personally, I think if we recycled the damn stuff it would be less likely to fall into the hands of terrorists because there wouldn't be so much nuclear waste crap everywhere. Which do you think is going to be more heavily guarded: a buried nuclear waste dump or a plutonium reprocessing facility. The U.S. law against reprocessing is idiotic and terribly wasteful.
Repeal the DMCA!
The dark side of all this is, of course, that a lowered cost of entry makes it just that much easier for "nuclear club" wannabe countries to produce plutonium for less benign applications. The author of the Economist article notes that countries could seal their CAESAR reactors (thus, I assume, burning the created plutonium for power alongside the U238) "to show that their nuclear intentions were entirely peaceful." Yeah, right. I'm sure Saddam Hussein and Kim Jong would be perfectly content to have their CAESARs crank out power, with nary a thought to the goodies sealed therein.
Yet another two-edged sword, but a damned intriguing one.
Life is like surrealism: if you have to have it explained to you, you can't afford it.
Our policy doesn't look so idiotic after what happened in Japan last week, with North Korea right in their back yard and well-known for its infiltration missions. In the U.S. we may feel more secure, but we've had plenty of nasty surprises in the last few years.
... I think our policy is debatable but not idiotic.
Stolen reprocessed plutonium would be very useful for a dirty bomb. It would have to be enriched before making a bomb, but it would be a headstart and obviate a nucleare reactor to make the Pu.
I don't think the problem is that we're overflowing in nuclear waste. The problem is we've had so much trouble confronting where exactly to put the stuff because of political opposition. Countries like Japan and France have far less oil, and this desperation makes the nuclear power sacrifices less daunting.
Old nuclear fuel is sequestered in ceramics and buried. There is not that much need to guard it. Nuclear fuel grade uranium is only 2-3% enriched U-235 to begin with, so its a -long- way from being particularly useful. Old weapons-grade Pu is mixed with material like U-238 to make it useless. With Iraq or N. Korea, the big challenge they face is not getting material, but purifying it.
So
IANANP (...Nuclear Physicist), but it sounds like this reactor would be an extremely poor candidate for breeding plutonium. To sustain any reaction, it needs the moderation carefully tuned so that the neutrons fission U-238. That doesn't sound very compatible with neutrons moderated to be absorbed by U-238 (thus breeding it into Pu-239).
It's easy to make up & spread cool- and credible-sounding stuff. Finding & checking hard facts is hard work.
At any rate, Fermi's reactor in Chicago (the first) used natural uranium (almost all U-238) as fuel. There wasn't any other choice. Enrichening U-238 to higher quantities of U-235 is a really big deal. Natural uranium contains only about one half of one percent U-235. Fermi's design used highly purified graphite in a honeycomb pattern as the moderator. The Russians, before they got the plans for our reactor, looked at a U-238 design that used heavy water as the moderator (the Germans were going that way, too). Anyway, as this guy has shown, it's all about finding the correct moderator in the right configuration.
On the first point, I made the mistake of semi-quoting the article. You're right, but I think the writer reasonably meant to indicate this one offered substantial advantages for monitors; perhaps use as a breeder becomes impractical. Someone else already complained about this.
:)
On the second, there is a natural reactor in Africa that years ago produced some plutonium. I included "virtually" to avoid nitpickers who know this, but forgot about the nitpickers who do not.
The pu.org site has other interesting info about, guess what, Pu.
Haven't you heard? We've already solved the nuclear waste problem. We just form it into weapons and dump it on soon-to-be third world contries like Iraq.
Although, I haven't yet found any good information on how much Pu is left at Aklo. But it's also the case that there's trace amounts of Pu to be found--some is generated from spontaneous fissioning of U-238 with subsequent reabsorption of a neutron.
Fission products are lighter nuclei which result from the fission of heavier ones. Some fission products are themselves radioactive, some are not. Pretty much all of them are useless as nuclear fuel.
Radiolysis is the radiation-induced breakdown of chemical compounds. A gamma ray or a fast neutron has more than enough energy to smash a water molecule apart, and this process will produce free radicals such as hydrogen and hydroxyl ions. If those radicals get together, you can get products such as hydrogen gas and hydrogen peroxide, and hydrogen peroxide decomposes pretty quickly to oxygen and water again.
You'd be better off reading an intro on the web, but I hope this whets your appetite for more learning.
Scientists restrict study to entire physical universe; creationist
This is all-important for making a bomb. U-235 has a half-life of around 700 million years, and making a bomb with it is easy: squeeze together a prompt-supercritical mass, and wait a few milliseconds. Pu-239 is tricky, because its half-life is only about 25000 years and you have very little time to get it into a prompt-supercritical configuration before a spontaneous fission starts the reaction going. If the reaction starts too soon, the bomb blows itself apart into a sub-critical configuration before releasing much energy and all you have is a fizzle. Now imagine dealing with a substantial fraction of Pu-240 (half-life 6564 years or Pu-241 (half-life 14 years).
Bomb-grade material is made in special reactors which allow the fuel to be irradiated relatively briefly at a low level, and then removed and processed to remove the plutonium. This is specifically to avoid the production of enough higher isotopes of plutonium to be a problem. The stuff coming out of a power reactor after a full fuel cycle is dirty as hell, but amateur proliferators are not going to be able to make a serious bomb (as opposed to dirty weapon) out of it. This is why we had few objections to building pressurized-water reactors for North Korea; they are essentially proliferation-proof.
I doubt that it's quite that simple. The real problem is that the plant required to refine fuel-grade Pu from spent power reactor fuel uses the exact same chemical processes as the plant which refines bomb-grade Pu from depleted uranium rods held briefly in a neutron flux for transmutation purposes. If you have a world full of people reprocessing it would be very hard to put a finger on the ones who are making weapons, so the US decided we had enough uranium to put the kibosh on all reprocessing just to set a good example.I think we should have gone with the Integral Fast Reactor, but it seems to have succumbed to the fundamentalist anti-nukes (who probably couldn't figure out that there are medical and explosive grades of nitroglycerine either...).
Scientists restrict study to entire physical universe; creationist
There are ways to get energy directly from fission of U-238, but they require very fast neutrons such as are created in a deuterium-tritium fusion reaction.
Then the Canadians must be smarter than the Russians, because the Canadians actually did it.Scientists restrict study to entire physical universe; creationist
IANANP but ...
It seems that this design not only allows the complete removal of the whole enriching process, and the elimination of a good percentage of nuclear waste, but it seems safer too.
The fission is only sustainable when the neutrons are just the right speed, which in turn can only happen when the steam is at just the right density. If anything goes wrong (e.g. steam escapes, etc.) the density changes and the whole chain reaction fissles pretty much to a halt.
However when a good percentage of the U-238 has formed Pu-239, would this level of control still hold? (Thinking that Pu-239 undergoes fission with a wider range of neutron energies.)
If the terrorists had the facilities to enrich plutonium, they might just as well mine their own uranium ore and enrich that instead of going to the trouble of sending in a lot of commandos to attempt to steal some plutonium.
Repeal the DMCA!
Thanks, that's interesting. Of course, it conflicts with a lot of what I've read, but a lot of what I've read conflicts, too. :)
My understanding from many sources is that a breeder can produce material of 20-30% Pu. Yes, it "can breed more fissionable fuel than it burns" but that new fuel is (as I understand it) exactly the Pu-239 we fear. All Pu comes from reactors, anyway, it's just a question of technique, esp. removing the material after a brief bombardment by appropriate-speed neutrons.
Bombarded Pu-rich reactor fuel is not the only problem, there's also the fuel-grade Pu after reprocessing. I've seen a couple of accounts of fuel-grade Pu bombs detonated, and I assume if one had the facilities to purify the fuel it would be even easier.
There are serious technical hurdles to engineering the actual bomb, but here we want to deny them even the fuel. Plenty of countries have surmounted the techincal end, anyway, such as Pakistan. Even a sloppy detonation would be bad enough. BTW, I'm not thinking about terrorists, unless they somehow stole a complete weapon. They'd take the surer low-tech path of a dirty bomb or flying a plane into a building, etc. Terrorists with nukes are a Hollywood thing for now.
On policy, here is a rather different account of why we don't reprocess -- economics. According to this account, Reagan vacated the Carter order in 1981. Truth?
So does this have any advantages (political or technical) over the Integral Fast Reactor?
Couldn't we just compost the nuclear waste? ;-)
...a fission reaction can be sustained with only U-238. But there is something serious wrong with some terms here. The name CAESAR says this nuclear reactor is environmentally friendly. I ain't buying it. If you have nuclear power, you make neutrons and you make radioactive crap. End of story. No human institution has existed as long as this waste will be need to be watched and no one has figured out a way to pay for that watch. Our great-grandchildren are going to hate us for the crap we will leave for them.
And then it was the damn Pentagon that renamed U-238, DU for "depleted uranium" as if uranium with out U-235 is complete safe. This has been proved time and time again, that it is not. U-238 is a dangerous substance and needs to be respects.
No fission reactor is safe enough to exist in our biosphere. Let the entire chain of uranium and plutonium economy be banned from several A.U. of earth orbit!
And the neutrons which caused the U-238 to fission did not come from the U-238, but from the D-T fusion reaction. This is why I'm skeptical about this U-238 reactor; I have no information to indicate that the neutron spectrum emitted by fissioning U-238 is capable of sustaining a chain reaction at all.
Scientists restrict study to entire physical universe; creationist
IAANP, and from what I can tell from the article, the design looks similar in concept to the boiling water CANDU, which didn't quite live up to its promise.
There are a couple of problems with steam-moderated designs:
The first problem is a polite way of saying there may be reactor stability issues. If CAESAR uses super-heated steam this may be less of an issue, but otherwise the ratio of steam to liquid in the cooling circuit is a function of pressure and temperature in ways that can create problems if there is an unexpected excursion.
The second problem is a major issue, especially when coupled with the long-term affects of radiation on materials. Intense neutron bombardment is a good way to introduce defects in metallic lattices. Defects are a good place for corrosion, cracking and other bad things to start. Ergo, the odds of a sealed reactor lasting for more than a decade or so are not good. Retubing of reactors is an ongoing maintenance problem even in conventional designs.
Nuclear power is an option that we may in the end decide we have to go with, and it's good that advanced reactor designs continue to get consideration, but the engineering challenges are still severe and the proliferation potential is large.
--Tom
Blasphemy is a human right. Blasphemophobia kills.
Here's the U of Maryland page on the CAESAR project.
http://www.caesar.umd.edu/
Death Before Decaf
In a reactor, the by-products would be ( probably automatically ) chemically seperated from the gas maybe as a solid ( idunno what substituting a barium/krypton/thorium/whatever in a UF6 molecule would yield: hopefully not fluorine gas but prolly Krypton+Fluorine is not a molecule. Maybe Krypton will decay into something more reactive fast enough to take up the excess flourine or maybe one of the other byproducts will be able to do it.)
In a rocket, why couldn't you just shoot the ( superhot ) crap out the ass end?
Eat at Joe's.
Separating plutonium from U238 in spent reactor fuel is much easier. Plutonium and uranium are different chemical elements and can be separated by chemical processes. It's not something you can do in your kitchen, but atom bomb designer Ted Taylor, in John McPhee's excellent book The Curve of Binding Energy, compares its difficulty to that of building, say, a large scale drug lab.
We know perfectly well that criminal organizations manage enough chemical engineering to produce refined heroin and cocaine by tens of tons even without any governments supporting or protecting them. Separating Pu from U in quantities of only a few kilograms, as an official project of the local rogue government, appears quite achievable in the face of that knowledge.
Yes, Pu from U is relatively easy. One of the sources said it can be done with nitric acid using a machine about the size of a refrigerator. If you're not worried about safety, it's a lot easier.
Isotopes are a different problem, and I didn't make this clear. Pu isotopes have different fission properties. For a weapons, the Pu-239 alone is desirable; the other isotopes, particularly Pu-240, tend to spew neutrons that cause pre-ignition of the reaction, resulting is a "dirty" nuclear explosion and inefficient conversion of plutonium. Non-Pu-239 isotopes also make the material harder to handle because of spontaneous decay.
A commercial reactor, esp. light-water, produces a significant proportion of the "undesirable" isotopes. Separating isotopes, as with U, is a lot of work; it's better just to produce the Pu right in the first place, that is, get the right reactor in the right configuration, and run it correctly for the purpose. But if you're a hard-up tinpot dictator and can settle for a 1-kt boom, or at least poison a water supply, and your real goal is to extort aid or concessions from other countries, then several kilos of dirty Pu will tide you over.
I'd like to know what kind of efficiency the Indian and Pakistani bombs have. I read somewhere that the device to approach 100% fission would be a very large H-bomb, and so the small "neutron bomb" of the 80's was pitched misleadingly.
I'd almost be inclined to let the most determined of the bastards get some spent fuel and try. The most likely outcome is that they'd kill a lot of their people from the radiation without producing anything useful (to them), whether their aim was a nuclear explosive or just a "dirty bomb". Their activities would not be that easy to hide; gamma detectors, xenon sniffers and such would make them much easier to find than people making anthrax or VX.
Use neutron irradiation to breed thorium-232 into uranium-233, then separate chemically. Bingo, you've got a highly purified fissionable isotope (but another bugger of a problem with short half-lives, not terribly much better than plutonium). If that uranium comes from a thorium breeder, you can do both.BTW, I got a nuclear physicist to weigh in on the plausibility of the parent article. He says that it pins his bogosity meter (my words, not his).
Scientists restrict study to entire physical universe; creationist
I'd take the CCNR stuff with a grain of salt; they are an advocacy organization. Going through their main web page, I find a lot of stuff which practically screams "NO NUKES!", such as opposition to any site selection for disposal of nuclear waste.
Scientists restrict study to entire physical universe; creationist
is probably enough to get a fusion bomb lit. It took a comparatively long time for the US and USSR to make fusion bombs because it wasn't clear at first that it was even possible. But China and apparently Pakistan got fusion bombs working pretty quickly.
I don't represent that page as the gold standard, but do notice it is headed:
~ excerpted from the US Department of Energy Publication ~
Nonproliferation and Arms Control Assessment
of Weapons-Usable Fissile Material Storage
and Excess Plutonium Disposition Alternatives
It's an excerpt of a Lawrence Livermore publication, and believe me *they* ("the bomb factory") are not anti-nuclear. Anyway, what it says is in accord with what I've read elsewhere, and the critical bit of data is the feasibility of a fuel-grade Pu detonation, that is, the proliferation risk.
A few thousand years is how long the pyramids have been standing there.
In a Google search I find entries for a Pakistani boosted uranium device, but nothing for a fusion bomb. Using tritium to create neutrons increases the fission yield of uranium, but it's not fusion.
Scientists restrict study to entire physical universe; creationist
This vaporware has a vastly greater chance of taking suckers for their money than the IFR.
- The excerpt was chosen specifically to misrepresent the tenor of the whole report; it wouldn't be the first time selective quoting has been used to re-write the truth.
- The excerpt may be accurately quoted, but the report might be put out there as bait. Nobody but a proliferator is actually going to try this, and the more effort a proliferator wastes on something which can't work, the better.
Just a note from a confirmed cynic.Scientists restrict study to entire physical universe; creationist