HOWTO Build a Nuclear Device

[Tim May]

On Saturday, November 17, 2001, at 12:37 AM, baptista at pccf.net wrote:

>
>
> On Sat, 17 Nov 2001, Tim May wrote:
>
>> I'd guess that the "tall pipe" version is the most buildable of the
>> basement nukes. (In a nutshell: a tall drainpipe, perhaps 40 feet tall.
>> Set up in an apartment building, warehouse, etc. At the base the pipe 
>> is
>> reinforced with copious amounts of concrete. The subcritical masses are
>> at opposite ends of the pipe. The mass on top is piled on with several
>> hundred pounds of ballast, to "tamp" the early critical mass action. To
>> explode the bomb, drop the mass from the top of the pipe. The critical
>> mass is briefly contained by the concrete collar around the pipe and 
>> the
>> inertial mass above. Is it enough to produce a real chain reaction?
>> Well, it's all relative. Still, not very efficient.)
>
> I very much doubt terrorist would build an efficient bomb.  Non of what 
> we
> discussed is effcient.  Your pipe idea is a very interesting example.  
> But
> I think the point is made that harm can be done.  Even if the mass does
> not go critical - it still means a few city blocks that will be
> inconvenienced from the resulting radiation.  You pipe certainly would 
> not
> go boom - but it would leave a mess of radioactivity in the area.

The idea _is_ for it to detonate, not just have a severe thermal 
excursion!

The total "radioactivity" in a critical mass of fissionables is actually 
not all that great. (Not something I'd want in my backyard, and sure to 
produce panic, but not all that significant.) The point of a bomb is to 
get a _lot_ of those radioisotopes fissioning in a much shorter amount 
of time than usual. Without that chain reaction, the radioisotopes are 
just decaying at their normal very, very slow rate. (The reason uranium 
is so radioactively benign is that it's half life is several billion 
years for the most common isotope and pretty close to that for the U-235 
form...the reason we still find both in nature, of course.)

For the oft-discussed "radiological bomb" there is no need for U-235. In 
fact, shorter half-lived stuff like cesium-137 and even spent fuel rods 
would be better.

Personally, this is much _less_  worrisome than biological weapons.

If radioisotopes are spread over a few city blocks, for example, they 
can be cleaned up in various ways. Easy to detect with a Geiger counter 
(or scintillation counter), easy to vacuum up with HEPA filter units, 
all sorts of foaming agents and hoses and the whole decontamination 
apparatus. And if the Geiger counter is silent, it's all gone.

A radiological bomb would result in an evacuation, and the usual panic 
by the sheeple who are afraid of atoms, but the cleanup would be 
straightforward.

(Chernobyl was what it was because many tons, even hundreds of tons, of 
fuel rods were vaporized and/or burned.  Not many terrorists could 
arrange for the vaporization/combustion of this much material.)


--Tim May
"As my father told me long ago, the objective is not to convince someone
  with your arguments but to provide the arguments with which he later
  convinces himself." -- David Friedman