What is this about centerfuges?

Consider the speeds and masses involved, the exotic alloys required, the balancing, the bearings, the gas-tight seals, all big problems.

If they're fast reactors, then what's the graphite for ? They're either thermally moderated, or they're a mixed mode. Power reactors (and keeping the reactor operating) uses thermal neutrons, but if it's operated as a "dual use" reactor then the fast flux is still appreciable and is used for breeding.

The USA uses light-water PWR's because Rickover's Navy bankrolled the development costs. Then the monopoly advantage steamrollered the rest of the world. The British designs went their own way for a couple of generations, but couldn't hold their own beyond the '70s. Only the French really have an indigenous nuke design industry remaining - everyone else is limited to license-building US designs, if they're lucky.

You're confusing temperature and void coeffcients. Temperature isn't a problem - the thing is massive, it only heats up slowly. The real gotcha is where water is used as a coolant - boiling can be rapid (especially with a sudden loss of pressure), and changes the reactivity in a way that the control system can't cope with.

What does Wigner energy have to do with a positive temperature coefficient ?

Windscale isn't in Scotland.

No relation at all.

Chernobyl was a stack of failures on top of each other. Bad operations, and a design that simply couldn't have a "small" accident. But it's far-fetched to draw major comparisons between it and either the Windscale air-cooled piles or the Windscale Pu-producing Magnoxes.

And by that fallacious argument, "Iraq was within reach of nuclear weapons, they just needed to get some fissiles"

FFS - Half of Usenet is within reach of nukes if someone hands them enough HEU.

The US, China and Pakistan went for uranium weapons first, but this is somewhat unusual. I doubt if a "rogue state" would try it now, as U enrichment plant is harder to hide than a reactor.

Yes. The obvious sources describe this in detail.

-- Smert' spamionam

They may be ideal for breading Pu-239, but to the best of my knowledge the graphite is a moderator and that makes them a slow-neutron reactor.

Do you have a cite describing them as fast-neutron reactors?

I think we've crossed the line with this thread to inappropriate.

What kind of uranium is needed for a dirty bomb?

Windscale 1 was a _low_ temperature air cooled graphite pile. Chernobyl was a _high_ temperature water cooled graphite pile. The Wigner energy gets released from the graphite crystaline matrix at about 250 C. Wigner energy was not implicated in the Chernobyl event, although it could be of relevance during decommissioning (only to the extent that the graphite needs to be annealed in a non oxidising atmosphere.

My -/2d worth

Mark Rand RTFM

Uranium isn't particularly good for a dirty bomb, you ideally want some isotopes that have a half-life of under a few years, and some nasty decay mode that will cause big biological effects.

Ground up spent fuel rods are good, as are some hospital radiological sources. It's really hard to make a dirty bomb that will cause large numbers of casualties. Oone that will cost many tens of millions to cleanup, and kill a few is much easier.

Just add a layer of cobalt round the plutonium and visit the site of the explosion a couple of thousand years afterwards.

No kind. Uranium has a long half life, that means it isn't very radioactive. For high enough activity to be scary, you need a material with a short half life, and if it is bioaccumulated, so much the better.

Gary

You need some of either uranium or plutonium in a dirty bomb -- no-one is scared of californium

If that's anything like Administratium, I'd be damned scared of it..!

Tim

-- "That's for the courts to decide." - Homer Simpson Website @