Really strong sources of radioactivity that made their way out of controlled areas don't create a sudden spike of headache.
It depends on the radioactivity level. At some level it leads to such effects. At some radiation level it leads to immediate feeling - a metallic taste in the mouth, nausea. But usually such exposure level leads to serious damage and death within 1-2 month or even week.
And such effects may not necessarily occur from direct contact with the radiation source. It’s quite possible that a nearby incident could have caused a powerful burst of neutron radiation. Such accidents usually happen at facilities dealing with radioactive materials. However, you might not even be aware that such a facility is located near you. Such facilities are usually secret, so you cannot be sure that your location is safe.
A relatively safe distance to avoid a lethal dose is about several kilometers. Are you sure that there is no secret facility in that range from you?
Such accidents have frequently occurred in the past at facilities dealing with highly radioactive materials. You can find official reports about it. And usually, this happened with highly qualified and trained personnel. Someone from the staff might have accidentally forgotten and placed a piece of plutonium in the wrong container, or some detail was overlooked in the process of handling radioactive materials, leading to an accident. Therefore, saying that such things are impossible is not realistic - anything can happen.
Even if you are certain that you are safe, there have been real cases where scrap metal hunters dismantled biological shielding from
RITEG containers. In one case, an unshielded piece of highly radioactive isotope was thrown into a trash bin at a bus stop. According to reports, the radiation level at the stop was around 200 Roentgens per hour... and ordinary, unsuspecting people were on that bus stop.
That there are "hidden" nuclear accidents in the world is absolute propaganda bullshit. There are lots of independent radiation monitoring networks in the world, they all would detect a large power plant blowing up and no one can hide it. Not even the USSR could do that 1986, and it´s well known they´ve tried to...
The assertion that "hidden" nuclear accidents are absolute propaganda bullshit overlooks several critical factors. Even though there are many independent radiation monitoring networks worldwide that can detect significant events, detection alone does not guarantee that the information will be publicly disclosed. In practice, information about nuclear incidents can be kept secret due to various reasons.
Governments, especially during times of crisis or war, may choose to withhold information to avoid public panic or to protect national security. Historical examples, such as the Soviet Union's response to the Chernobyl disaster, demonstrate that even significant nuclear accidents can be kept from the public eye for a time. The Soviet Union attempted to suppress information about Chernobyl, despite the presence of radiation monitoring networks.
International monitoring organizations may also be subject to censorship, particularly in extreme situations like the onset of a nuclear war. In such scenarios, no information about the radiation situation might be published at all, just because it could reveal the effects of a nuclear strike to adversaries.
Accurate public disclosure could provide strategic insights to opponents, potentially affecting military planning and response. No rational entity would publicize the real outcomes of a nuclear attack, as this could prompt further nuclear strikes if the initial attack was deemed insufficiently effective, or inform the enemy about the effectiveness, influencing future military strategies.
Given that we are in a situation where a global nuclear war could start at any moment due to corruption, greed, and the ambitions of certain politicians, it would be very naive to expect that anyone will provide detailed information about the radiation situation if something serious were to occur.