"U-235 and plutonium are neutron emitters. Put enough of either one together and you get a chain reaction. You do not have to have an initiator to make this happen."
While true, those statements do not lead to intuitive conclusions. For instance, building a nuclear weapon WITHOUT an initiator is FAR more difficult than building one WITH an initiator. The fact is counter-intuitive to the surface logic.
Moreover, getting a "chain reaction" is a fine way to generate heat and radioactivity, but it is a far cry from generating the super-criticality needed for an explosion.
Furthermore, simply trying to put more and more U-235 or Plutonium together in one mass will lead to a fizzle far more times than it will lead to an explosion due to the neutrons firing at the wrong time as the material comes toward close contact with each other. The technical hurdle involved with the precise timing of the necessary neutron emissions is a non-trivial endeavor, the solution to which is contained in the initiator/trigger.
And that's how you will find that EVERY nuclear weapon is made, with an initiator/trigger (and certainly how every small "backpack" nuke is made, as small size presents even more daunting technical hurdles).
Well, the radioactive materials (contained even in your own link that you posted onto this thread) inside initiators/triggers decay. Polonium's half-life (as posted above) is about 138 days, for instance.
But wait, there's still more: not only do the initiators have a finite life-span, but the electronics that are exposed to the radioactive materials inside the bomb likewise degrade.
Thus, even a FULLY WORKING, ARMED nuclear weapon requires frequent specialized maintenance. Without it, the weapon soon deteriorates into little more than a poisonous dirty bomb.
But the urban myth of the "hidden cold war nukes" makes for great tabloid journalism. What could be scarier than the thought that spies are selling atomic weapons that are already pre-positioned in our own back yards?! Quick, everybody run for the hills, the Sky is Falling!
Your argument is that it is simpler to make a bomb if a source of high neutron emissions is included in the design. By definition, anything that emits a high number of neutrons will have a short half-life, and may damage the electronics around it (depending on how the neutrons are absorbed).
None of that is in dispute. You can post all you want about half lives, but it is, and will continue to be, irrelevant.
The first relevant point is: CAN you make a bomb without a "trigger" and with a multi-year shelf life. The answer is YES.
The second relevant point is: DID the Russians do so?
If the Russians built such weapons, the question then becomes: Are some MISSING? And, if so, where are they?
It is completely legitimate to contend the Russians never built these weapons, or that, if they did, they are not missing. It is not legitimate to contend that they COULD NOT have built such weapons because it is impossible to do so. It is most definitely possible to do so, and anyone with your research ability must certainly realize this.
BTW: I freely admit the difficulties involved. Furthermore, I'll give you even more ammunition: The U.S. has experimented with small yield weapons, and found that very small yields tend to be much harder to make go bang (fizzles, etc.). That is why I do not think any of the third world punks we are fighting could have done it.
Note to the various patriotic lurkers: The fact that we have done these experiments is unclassified. I do not give out classified information, or information potentially harmful to the U.S. No need for flames about my patriotism.
BTW2: The third world punks we are fighting have access to Pakistan's demonstrated nuke technology. They CAN make a functional bomb if they can get the materials. It WOULD be small enough to fit into a missile warhead (but probably NOT into briefcase).
A weapon such as this could be placed on a ship and detonated in a U.S. harbor. Our best defense against this type of attack is good intelligence.
BTW3: We are NOT able to find/track a shielded nuke by satellite (another common misconception). We CAN spot neutron emissions with the right equipment if we are close enough (the exact range is classified, thankfully). A conventional geiger counter does NOT detect neutron emissions (as I suspect you know).
The primary satellite technology used to find Russian nukes was/is ground penetrating radar. It enables us to find missile silos, not the warheads themselves. It does not work well in all soil/ground conditions.
CONCLUSION: Go ahead and argue that we face no threat from pre-positioned nukes (we both hope we don't, but neither of us knows). But argue your point from legitimate grounds.