The process is a little like getting a ball of HEU, removing the core as you would an apple's, bolting the pitted end to the muzzle of an artillery gun, then firing the core back into its center.
To do this, your metallurgist needs to cast the enriched uranium into the requisite shapes. Uranium melts at around 2,069 degrees Fahrenheit (that's 1,132 Centigrade for terrorists still clinging to the metric), so don't skimp on a good furnace—you can find one used on eBay for around $50,000.
Once you've fired up the furnace and softened your HEU into a workable goo, shoot it over to the lathe for shaping (but don't spill any on the carpet).
If you've never used a lathe, any high school machine shop teacher can show you the ropes, although he's likely to ask questions about what you're building. If one of your terrorist friends can work a Jedi mind trick, now's the time.
While you mold your subcritical masses, send somebody out to cop the surplus artillery gun. Recoilless army rifles are widely available in the U.S., but they usually come disassembled, so plan on some wrenching. If you're more manager than mechanic, any hobbyist can refurbish a recoilless rifle for just a few grand.
Get your electrical team off the XBOX and have them craft some circuitry for all your timing, arming, and detonating needs. Ideally, this thing triggers remotely, as anything within a half-mile of the blast will be instantly vaporized, with complete and utter destruction reaching a mile outside its hypocenter. Massive fires and radioactive fallout will claim everything within five miles, so if your target's Times Square, get across the bridge to Jersey.
Of course, if you're the suicidal terrorist type, like all 19 of the 9/11 hijackers, setting this thing off is about as easy as pulling the trigger on your homemade rig. If you can fire an artillery round and pish paw sublimation, you can decimate a beloved world city.
And there you have it, your very own nuke. It's about nine feet long—bigger than a breadbox, but the perfect size to ride coach in a white panel van—so feel free to take it on the road. Preferably someplace far away from civilization, where you can get down to vaporizing yourself, your terrorist buds, and all your worst-laid plans.
If any of this sounds alarmingly easy, you're right—and it's only one scenario where proliferation bites the world in its badonkadonk.
But like any avoidable event—from 9/11 to the Gulf oil spill—an ounce of prevention will buy a ton of cure.
The first step? Stop believing nuclear weapons are too big of an issue to tackle.
While nine nations have nukes, 184 countries signed onto the Nuclear Non-Proliferation Treaty (NPT) have refused to develop the bomb. If you're feeling like nukes are an issue beyond your means, remember that the vast majority of the world has already stood up to the weapon of most destruction.
That doesn't mean the work's done. Three countries—Israel, India and Pakistan—have refused to sign the NPT and continue to expand their nuclear arsenals. If we ever hope to see an end to nukes, we have to get these naysayers involved. To take part in some serious Israeli-IndoPak arm-twisting, sign up for Global Zero.
If you don't want to see a gun assembler in your neighborhood, locking down nuclear materials is a must. The lands of the former Soviet Union may be a little loosey-goosey, but so are civilian stockpiles across the rest of the nuclear-powered planet.