Call me naive if you will, but how does one go about smuggling such a weapon? I mean could this thing, in reality, but put in a suitcase?
Probably float it in on a barge or something.
No.
How about on a ship?
The Russian's had (have) one in the attic of their embassy in DC. They brought it in piece by piece in diplomatic pouches.
Probably hid it in drugs.
Yes. I even saw a diagram of a suitcase nuke in the regular media. The diagram was part of a briefing to the senate a few years ago. A diagram was also published on FR a few months ago.
I was on a B-52 crew for a few years, and in a later job I worked with ICBMs. I have spent a lot of time around nukes.
Even the nukes we put in planes and/or missiles are a lot smaller than most people think. They give off very little radiation and would be very hard to detect from more than a few feet away. If they were shielded by the lead aprons used in your dentist's office, they would be almost invisible to any possible detector.
A primitive radiological bomb is a completely different matter. These are simply regular bombs with radioactive material placed around the explosive. They do no more damage than a regular bomb, but they scatter the radioactive material at the same time. It would take a huge amount of radioactive material for this to really be dangerous, but even a small amount would be enough to scatter detectable amounts of radioactive material over a several block area. The psychological effect would be much larger than the actual damage or actual risk from radiation.
These bombs are very radioactive, and thus far easier to detect than an actual American or Russian nuke. As long as you do not care about your own health, they are extremely easy to make. It seems certain that the terrorists have this kind of weapon.
BTW: Having a stolen nuke and being able to set it off are far different things. Setting them off is very, very difficult without the proper activation code. Given enough time and an extra one to reverse engineer, you might be able to figure it out. However, even then it is not certain you could actually set it off.
Maybe not. But it probably could be placed in the hold of a ship and detonated in New York Harbor.
It would have a yield of less than 1 kiloton.
I've seen photos of our own suitcase nukes (called "Atomic Demolition Munition"). Ours weighed around 163 lbs and had a yield up to 1 kiloton. Do a search on google.com for that term if you want the cr*p scared out of you.
Something the size of a trunk is quite feasible technically. We had a whole series of threads discussing this back a few months ago, and the consensus was that it was indeed feasible to construct a nuclear device that would fit in something the size of a trunk. A little difficult to carry down the street, especially since it would weigh 70-150 lbs. But quite easy to carry even in a VW beetle. There is somewhat credible evidence in the public domain that the Soviets, at least, did actually produce some quantity of these. The US appears to have experimented with something like this, but it is uncertain whether such ever was or now is in our weapons inventory.
It is more questionable whether or not something the size of a suitcase is feasible. Theoretically possible, perhaps, but the problems involved tend to work against it being attempted.
Obtaining such a device is only the first challenge to a terrorist. The device's control systems may need to be re-engineered, something that a competent electrical engineer might be able to do. The device may or may not still have its fissile core, it may actually be easier to obtain a device on the black market with the fissile core removed. If no fissile core, then weapons-grade material must be obtained (much more difficult to do), and then properly processed and fabricated. The third piece that would evidently be an absolute necessity would be a small supply of fresh Tritium. These small devices absolutely must have a neutron generator to seed the chain reaction, and you must have fresh Tritium to do it. Very rare, very expensive, very difficult to obtain even on the black market.
The only likely scenario for OBL or anyone else to have an actual working device would be to obtain all three elements through separate transactions with different players. Not impossible, but very difficult to pull off.