Ingredients:
Instructions:
The hardest bit would be getting the fissionable material which is, to the detriment of potential nuclear terrorists worldwide, not readily available at your neighbourhood grocery store.
And a way not to kill yourself in the process. That's always an important one.
I think there's actually quite a bit more to it than having enough material and having it reach the critical mass. Safeguards against having it blow up before it reaches its target destination, a housing for the materials, a nice shiny bomb casing like they show in the movies, etc. There's a reason not everyone has their own nuclear weapon. (Except in certain parts of the former USSR, maybe.)
In any case, getting enough fissionables to build a gun-type bomb would be really, really hard. Getting enough to build an implosion weapon wouldn't be easy; plus, the technology required isn't trivial. It can be done; however, doing it in a backyard is stretching credibility unless that backyard has some pretty high-quality machine tools, electronic components and explosives experts in it with the facilities to handle and cast radioactive metal.
Finally, while it's true that low-level radioactives can be found in everyday life, none of these are suitable for fission or even decent contamination levels.
Note: niaporte noted, quite properly, that I had misidentified Little Boy's target as Nagasaki. It was, in fact, Hiroshima. My error.
The nodes above have discussed the implosion type rather throroughly, but nonetheless it operates on the principle that you propel a plutonium sphere into a beryllium-polonium core. This requires, however, a non-nuclear explosive.
The gun type bomb operates on the principle that one can send a uranium wedge into a larger uranium target thereby reaching critical mass. The uranium wedge would be projected by means of a conventional explosive ignited by a radio signal.
Again the principle behind each is relatively simple, create enough mass and density that the probability of neutrons from one nucleus impacting with another is high enough for a sustained chain reaction. In principle these are relatively simple, but they are also relatively low yield, with only a few kilotons. Apparently there are all sorts of ways to boost yield.
Its amazing what you can find from the internet and world book encyclopedia
As mentioned in previous writeups, there are two basic types of nuclear bombs:
The Little Boy design- Uranium 235 (U238 won't do) is formed into two parts that are brought together. This can be done as either a wedge into a sphere or a plug into a cylinder. By far the simplest design (though with a lower yield), this kind wasn't even tested before being dropped on Nagasaki, so confident were the designers of it's design. As mentioned above, however, the trick is to bring the two pieces fully together before the simple mechanical heat caused by the beginnings of a chain reaction blows the whole thing apart in a minor nuclear fizzle rather than a genuine nuclear explosion.
the Fat Man design- Plutonium formed into a spherical shell is imploded. The trick is that explosives aren't very good for forming things into dainty shapes. Generally something inside a spherical configuration of high explosives does indeed go inward, but not very precisely- bits of it tend to be ejected out, some areas are more compressed than others, all sorts of problems. The solution to this is to use different kinds of explosives in the outer shell. Like all materials, different explosives transmit force with different speeds. So high density explosives are packed in strategic locations throughout the shell that otherwise consists of lower density explosives. These high density nodes act as lense to focus the force on the center, so that instead of having these roughly interacting waves of force coming from every which way, the plutonium is instead hit by neatly focused force that pushes everything in to the center.
In both configurations, a neutron source is placed in the center of the configuration to ensure that the chain reaction actually starts. Chances are it would anyway, but why take the chance?
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