What is this about centerfuges?

They go very, very, very fast, and are a significant challenge to make.

What are you going to do about radiation-caused embrittlement?

There is a general description in Frederic Forsyth's spy novel "The Fist of God"

"Basically you put the feedstock into a thing called a certifuge which spins so fast the whole process has to be done in a vacuum or the bearings would turn to jelly. Slowly the heavier isotopes, the ones you want are drawn to the outer wall of the centrifuge and bled off. What's left is a little bit purer than when you started. Just a little bit. You have to do it over and over again, thousands of hours, just to get a wafer of bomb-grade uranium the size of a postage stamp. [...] These centrifuges... to save time we link them in series, called cascades. But you need thousands of centrifuges to make up a cascade." "The Fist of God" © 1994 by Bantam Books

I don't know how accurate that description is, but Forsyth is usually pretty careful about his research.

As they become brittle replace them. Still not rocket science. I still don't understand the fuss.

Pete.

That is pretty much my understanding of the process. It is large scale but not particularly difficult from a machinists perspective.

Pete.

Not an issue if you are enriching uranium from ore. A physics genius ought to know that (:

I don't see what all the fuss is about nuclear wepons anyway. It's just like those old civil war tintypes in the 1800s, it's just that instead of using film they use people.

Nothing ? It's not a problem.

Enriched uranium isn't especially radioactive. It's at an unhealthy level for critters, but it's far from the levels to cause a materials problem.

Why not a warehouse full of calutrons?

The whole isotope separation route is silliness to me. Much easier to make Pu in a reactor and chemically separate it from the U.

I guess that makes sense. And I guess it's why I'm not called "MaterialsScienceGenius".

Well...wouldn't you need to enrich the uranium to run the reactor from in the first place?

Getting weapons grade Pu from a reactor is also quite complicated. You have to extract the Pu and seperate it very often. If you don't you'll wind up with too much of the wrong isotope of Pu, and that will make it un-usable for making weapons. That is why most weapons grade plutonium is made in graphite-core reactors (easier to pull rods in and out). These reactors are actually inherently unstable (the graphite core as a mediator has a positive temperature coefficient....look no further than Chernobyl for an example).

Should also keep in mind that Uranium weapons are much easier to make than Plutonium ones (assuming you already had the material for each). If you wanted the quickest route to making a weapon (and be sure it would work), it'd be easier to start with Uranium. (BTW, does anyone know what India and Pakistan used in their first weapons...?)

Todd

A common misconception. No.

A reactor will run just fine on unenriched uranium. As a matter of fact, there have been at least 1, possibly 2 naturally occuring reactors in geological formations rich with uranium ore.

Ahh...now that you mention it, I do remember reading about one of those natural reactors. I still say it isn't a cakewalk to get weapons-grade Pu from a reactor though.

Todd

No, and enriching uranium is easy anyway. What's hard is enriching it to a high level.

Getting a working reactor needs a balance of reactivity from your fuel and absorption in the moderator. If your fuel is "weak", then your moderator choices are restricted - but still possible. Two moderators that work with natural uranium are heavy water (the Canadian CANDU reactor) or very pure carbon (Fermi's first pile, the British Magnox or the North Korean designs). If you enrich it a little, then you could go for a light-water PWR.

Was that pun intentional?

Regards,

Boris Mohar

Got Knock? - see: Viatrack Printed Circuit Designs

Ontario

Thankfully true. I've been out to the Hanford Reservation in Washington a few times, including working right next to the original chemical separation building. Despite some serious over- designing, the scale of the process is awesome.

I remember reading about this too. It's true that there was nobody around to enrich the uranium, I understand that it was so long ago that the uranium was already richer. Let me get my textbook out here.

"Both U235 and U238 are radioactive, with half-lives of 7.04e8 y and

44.7e8 y, respectively. Thus the half-life of the readily fissionable U235 is about 6.4 times shorter than that of U238. Becuase U235 decays faster, there was more of it, relative to U238, in the past. Two billion years ago, in fact, this abundance was not 0.72%, as it is now, but 3.8%. This abundance happens to be just about the abundance to which natural uranium is artificially enriched to serve as fuel in modern power reactors."

(Halliday and Resnick, Fifth Edition Extended, page 1106.)

I was not aware that the U in the naturally occuring reactors was effectively enriched.

Nonetheless, the Hanford production reactors used uranium metal reduced from unenriched uranium ore.