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Centrifuge May Be Superseded by Laser Enrichment
An anonymous reader writes "Australian scientists have discovered, after a decade of tests, a new way to enrich uranium for use in power plants." From the article: "There are at present only two methods for sifting uranium atoms, or isotopes, to create the right mix. One, called diffusion, involves forcing uranium through filters. Being lighter, U-235 passes through more easily and is thus separated from its heavier counterpart. The second method, widely adopted in the 1970s, uses centrifuges to spin the heavier and lighter atoms apart. Both, said Dr Goldsworthy, are 'very crude. You have to repeat the process over and over,' consuming enormous amounts of electricity. The spinning method requires 'thousands and thousands of centrifuges'."
It's been around for over 20 years. What's new is that the Aussies appear to be commercialising it.
No problem : here you have an emissions comparison for all widespread methods and various pollutants
http://www.nei.org/index.asp?catnum=2&catid=260
According to Mordechai Vanunu, the Israeli nuclear whistle blower - as quoted by the Sunday Times - Israel had laser enrichment technology, in actual production use, at the early 1980s.
http://en.wikipedia.org/wiki/Mordechai_Vanunu
So - nothing new here, move along, move along.
However, it's a LONG way from lab benchtop enrichment experiments to a functioning enrichment plant. And once you get to that functioning enrichment plant, there's the question of whether or not it was economically justifiable to build in the first place. This is where the American effort "failed" - even on paper, it never made sense to pursue this technology because it was just too expensive. Sure, you need thousands of high-precision centrifuges to run an enrichment cascade. This was still cheaper than building a laser enrichment plant.
The designs for a uranium laser enrichment plant ON AN INDUSTRIAL SCALE are not for the fainthearted. YOu've got to have the uranium in a gaseous state. That means heating it so hot that not only do you have a pool of molten uranium, but it's BOILING. The laser is going through the HOT uranium "steam". The only material that can stand up to these temperatures is pure graphite. The design becomes like a series of rain gutters on a house that carries "more enriched" and "less enriched" streams of molten uranium back for reboiling. Somehow you've got to figure out a way of putting optical ports into this hellhole to fire the laser beams in. The laser beams themselves are a weird wavelength (green) and takes some really expensive gear to generate at all, much less with intense enough power to penetrate deeply into a fog of molten uranium. Doing all of this cheaply? Good luck.
And in the background overshadowing enrichment plant economics was and is the fact that nuclear power plants are still just too expensive a way to generate electricity (primarily due to regulatory costs) compared to coal and natural gas turbine plants. The expected boom in nuclear power plant construction forcast in the 1970s and early 1980s never materialized, mainly due to Thre Mile Island and Chernobyl, and so the need for new-fangled enrichment technology as a support industry never materialized with it either.
Right now the cheapest way to come up with fuel for a nuclear power plant is not laser enrichment or even centrifuge enrichment. It's diluting old Russian warheads, all 30,000 of them, down from 93% enriched uranium back to 3% uranium. This, along with all those Russian brides American men now have access to, are the REAL spoils of winning the Cold War.
"Oh, and it's not just the Jews that are to wear 'ribbons', it's chritians as well. Patch sewn onto clothing. Sounds familiar, doesn't it?"
Ya, it does sound familiar...
There is a third method that has been used on an industrial scale, which is to essentially build a huge mass spectrometer. Mass spectrometers are usually used to separate atoms into their isotopes for analysis but Ernest O. Lawrence proposed this for the Manhattan Project and the Y-12 separator at Oak Ridge, TN, built in 1941, yielded some useful results before being superseded by gaseous diffusion at the K-25 facility and later the S-50 thermal diffusion plant. Indeed the first 200 grams of fissile material delivered to Los Alamos came from the electromagnetic separator, more than a year before the diffusion separator started operation (the uranium bomb dropped on Hiroshima used about 64Kg)
If intelligent life is too complex to evolve on its own, who designed God?
If you read up on the Gen-4 reactor designs, you'll find that greenhouse gasses, non-proliferation, safety, and more efficient designs (a LWR reactor is rather wasteful on the scale of designs) have been taken into consideration. Rest assured that the new reactors being built in Florida, and all across the USA are being built with the best, safest technologies available.
Oh, and the thousands of centrifuges? That's just bad journalism. I don't know how lasers are cheaper at all (someone needs to actually write a decent article here), but for what it is worth, Nuclear Energy in the United States is cheaper than coal, but just barely.
Check out www.nukeworker.com and ask your questions there. Those guys know their Uranium from their belly buttons!
As far as I'm aware, fissile plutonium doesn't always come out of the process - it needs to be a specific type of reactor, with enriched fuel, to "breed" plutonium...
That's not true. In conventional nuclear reactors, the plutonium naturally produced is fissile, or at least a substantial proportion of it is. This gives rise to the "moderator coefficient of reactivity" in thermal reactors where an increase in moderator temperature brings about a proportional increase in the number of neutrons with the correct energy spectrum to cause fission in the plutonium. This is a form of neutron resonance.
This is why Magnox and AGR reactors are "positive feedback" systems.
When a Magnox reactor is new, there is no plutonium, so there is no plutonium fission, so for the first few months of operation, the reactor is negative feedback.
In AGRs, the moderator temperature is kept constant by running the cold coolant gas through the moderator prior to cooling the fuel, so AGRs are negative feedback (and hence stable) as long as the moderator temperature is kept constant, which is achieved by active safety systems.
PWRs, on the other hand, are light-water moderated. They are effectively under-moderated and are epi-thermal reactors. They are negative-feedback since any increase in the moderator temperature (water) causes it to expand, reducing its density and hence the amount of moderation. As long as you can keep pressurised water flowing around a PWR it is stable.
In a previous life I worked in Reactor Physics at a nuclear power station.
Stick Men
If a photon of precisely the right frequency (and therefore energy) hits an atom, two things happen:
(1) It gets absorbed, and transfers its momentum to the atom -- i.e., gives it a little push.
(2) One electron in the atom absorbs the photon's energy, exciting it to a higher energy level.
Then, after a random time interval, two more things happen:
(3) The electron drops back down to its old energy level.
(4) The atom emits a photon, carrying the energy given up by the electron, and the photon's momentum delivers another push to the atom.
But while the first push was in the direction of the laser beam, the second one is in a random direction -- so the affected atoms, statistically speaking, wind up with a net gain of momentum in the direction of the laser beam.
So far, the laser is basically just stirring the gas. Now you tune the frequency of the laser a little bit lower. The "average" atom sees the photons at the wrong frequency, and the photons just truck on by. But atoms that happen to be moving toward the laser see the photons Doppler-shifted up to just the right frequency and they receive a push away from it -- so their average speed is reduced. Ba-bing, ba-boom, the gas is colder.
Laser cooling, along with a couple of other techniques, made it possible to get the super-low temperature needed to isolate the Bose-Einstein Condensate which got the 2001 Nobel.
rj
Use of UF6 is the MLIS process, championed by Los Alamos. Use of atomic vapor is the AVLIS process, championed by Livermore. You would not believe the endless arguments that ensued during the 1980s over which was better. AVLIS won.