Reply to: Interesting fact about making a nuke from New Scientist

[zeitghost]

Complete and utter b’locks. A reaction can only take place if compression is from all direction, hence why timing is the key to making a bomb. Korea is currently only get 10% of the yield because it can bot get the timing right.

Wrong!

With enriched uranium, you can achieve fission just by using a gun device.

I suspect that dropping the 2nd lump from 6 feet probably does not qualify for this definition (coz it's likely to fizzle because the lump is not travelling fast enough).

And this remarkable object achieves criticality with 54kg of 93.7% HEU.

https://en.wikipedia.org/wiki/Godiva...e-scrammed.jpg

Without generating 10kT.

[bogeyman]

Complete and utter b’locks. A reaction can only take place if compression is from all direction, hence why timing is the key to making a bomb. Korea is currently only get 10% of the yield because it can bot get the timing right.

Surely that's not entirely accurate.

If you use small masses of fissile material then, yes, timing and high energy inputs, and symmetry are critical to get a runaway reaction.

If you use fecking big chunks of the stuff (which is really desperate to go critical anyway) then it doesn't take much finesse to lob them together using any old explosives (or even gravity as the article suggests) and get a huge nuclear bang.

Hard to see how anyone would come across such large amounts of enriched Uranium etc. tho.

[_V_]

Complete and utter b’locks. A reaction can only take place if compression is from all direction, hence why timing is the key to making a bomb. Korea is currently only get 10% of the yield because it can bot get the timing right.

From the New Scientist article:

The POGO report also argues that improvising a nuclear bomb using Y-12's highly enriched uranium would be a relatively easy task for terrorists on site. Simply dropping one 45-kilogram lump onto another from about 1.8 metres could create a 10-kiloton explosion, it says, killing or injuring up to 60,000 people. The prospect, however, is dismissed as "fanciful" by the DoE's National Nuclear Security Administration. "There are better odds that an asteroid would hit Oak Ridge," says an NNSA spokesman. "The facility is well prepared to defeat a terrorist attack."

Still Bollocks?

[threaded]

I heard they had altered the composition of ammonium nitrate to prevent it going pop

Yeah, they mix in some aluminium powder and it makes a wonderful weedkiller, especially against daisys. Doesn't go 'pop', more of a 'whump'.

[Troll]

He also says that he’s got shed loads of ammonium nitrate that nobody wants anymore.

I heard they had altered the composition of ammonium nitrate to prevent it going pop

[Buffoon]

Bloody typical! I thought I’d have a go at this. So bright and early this morning I got myself down to B&Q to get stuff to try and make one myself for bonfire night. Can’t get any plutonium anywhere. Apparently there has been a bit of a rush on the stuff recently. I got talking to the manager. He said that just the other week everyone wanted hydrogen peroxide and acetone, but the fashion for that has gone and everyone wants plutonium these days. He also says that he’s got shed loads of ammonium nitrate that nobody wants anymore.

[hattra]

Excellent !! Now that I know what I'm looking for and in what quantities, I'm off down the garden shed to experiment.
I'll keep y'all updated as to how things progress.
I might just call it SKA for short.

More toadstool-clouds than mushroom clouds in your case, I suppose

[Toad]

Excellent !! Now that I know what I'm looking for and in what quantities, I'm off down the garden shed to experiment.
I'll keep y'all updated as to how things progress.
I might just call it SKA for short.

[hattra]

It just shows how reliable memory is. I though I might have that 2 kg figure wrong, so I decided to look up critical masses - they are 15 kg for uranium-233, 50kg for uranium-235, and 9kg for plutonium, and, so two 45kg lumps of 100% pure u-235 are feasible. though I wouldn't like to be anywhere near them!

[hattra]

IIRC from "A" level physics all those years ago, the critical mass for uranium is much smaller than 45 kg - I think its around 1.5 - 2 kg, at which point you get a chain reaction occurring that releases huge quantities of radiation (certainly rapidly lethal to anyone nearby) and a great deal of heat.

I suspect a 45kg lump of enriched uranium might be impossible to achieve - I think it might well catch fire and burn from its internally generated heat.

There was a scene in "The Edge of Darkness" where the crazy american officer pulls two 1 kg lumps of uranium out of his briefcase at a conference, and at the end of his speech, puts them together in front of everybody - they were climbing over each other to get out

There was an american university student who designed a bomb for his degree thesis about 15-20 years ago. His design cost about $5000 to build and would have produced a yield, from memory, of about 15 kilotons. Mind you, to keep it cheap, he had to use a lot of concrete, so the whole thing weighed about two tons

[Troll]

It took a seriously long time to produce enough bomb grade enriched uranium 235 to make the Hiroshima bomb.

Using an enormous diffusion plant, centrifuges and calutrons, they just about had enough to make it go pop by August 45.

Ahh but that was the second device to go pop

[scooterscot]

I agree with Paddy. A sphere 100% pure with suitable force from all directions would allow full release of the energy available. An equally spaced circumference of surrounding explosives would achieve this.

[AtW]

And you need an urchin or similar to start it all off.

Looks like you know too much about nuclear weapons. Please prepare your suitcase with documents and bare necessities for a rendition flight - don't forget to take a towel with you too...

[Paddy]

If terrorists get hold of two 45Kg lumps of enriched Uranium (there are tons of the stuff in Russia and USA with minimal security) and drop one lump on the other from a height of 1.8 metres, they would explode with a yield of 10 K tons.

Not exactly a difficult task once you have the enriched Uranium.

Complete and utter b’locks. A reaction can only take place if compression is from all direction, hence why timing is the key to making a bomb. Korea is currently only get 10% of the yield because it can bot get the timing right.

[zeitghost]

It took a seriously long time to produce enough bomb grade enriched uranium 235 to make the Hiroshima bomb.

Using an enormous diffusion plant, centrifuges and calutrons, they just about had enough to make it go pop by August 45.

I have a feeling in my water that you'd get an extremely large fizzle if you just dropped the one onto the other.

The original weapon was a gun device in order to get the two lumps together fast enough that it wouldn't fizzle, but would go pop properly.

The reason that you can achieve criticallity with so much less plutonium is that you have to use spherical compression or the thing will fizzle anyway.

And you need an urchin or similar to start it all off.