Donna Wells2 said:Quoting "Wikipedia"
"The radioactivity dispersed by the wind primarily impacted the health of residents in neighboring northern Belarus, but also affected the far northern regions of Ukraine and the southwestern areas of Russia, whose border was also in close proximity. The clouds of radioactive dust finally stalled over Scandinavia in the northern parts of Europe. Both direct and indirect consequences of radiation exposure were felt by up to 5 million people. Health problems for a large number of people persist to this day, and a particular issue remains the quality of environmental cleanup in the immediate vicinity of the nuclear power plant."
By the way, it took five days for the cloud to reach America... and it was much less intense than what happened in the USSR.
This isn't really the main point of our discussion, but I feel compelled to clarify because it seems many people are missing a fundamental distinction: a nuclear bomb and a nuclear power plant accident are two entirely different beasts.
With the former, the primary objective is a massive explosion designed to cause widespread devastation and, if possible, total annihilation within a specific radius; the actual amount of radioactivity released is, relatively speaking, quite small.
With the latter, an explosion does occur—it’s true—but it’s something else entirely (in the case of Chernobyl, it was essentially a steam explosion, let's not get bogged down in the technical minutiae), and while the explosion itself is relatively contained—only one person actually died directly from the blast at Chernobyl—the volume of radioactivity released is staggering because there is such a massive amount of radioactive material sitting right there in the reactor.
Chernobyl unleashed a mountain of radioactivity because the fire and the continuous release of particles into the atmosphere raged on for nearly two weeks. A nuclear bomb, particularly a tactical one, would have a much smaller impact in that regard, and the contamination would likely be localized.
However, you still have the issue of that local radioactive fallout, which wouldn't just vanish in a couple of weeks. If you are planning on sending your troops in after a tactical nuclear strike, I certainly wouldn't believe it could be done without some serious risk to them.