>>2500787Actually the Swedes were the first ones to find out that something happened. On the 28th at the Forsmark Nuclear Power Plant some workers from the morning shift going in the plant were refused entry at the automatic radiation detection gates. Because the gates have detected, that they've already received the maximum daily allowed dose (of radiation).
At first they thought that something was off with their plant, but later they found out that the plant was safe and the radiation comes form a reactor incident, probably from Eastern Europe (Lithuania, Belarus or Ukraine). It took some 12 hours to figure out which plant it actually comes from.
This was a widely reported fact at the eve of the 28th (by the BBC) so the US knew basically 2 days later.
Fun fact: at the time all eastern block countries had recalled all radiation dosimeters (personal dosimeters, geiger counters, etc.) from the scientists and locked them up. And is some countries authorities began to give preschoolers and elementary schoolers iodine tablets. This of course considerably raised suspicion that something went terribly wrong with some reactor. By the 29th the eastern block countries' media also began reporting on the incident. Dismissing it as a minor malfunction. But the genie was already out of the bottle, so they had to come clean in about a week. About the time the first bodies began dropping.