(I initially wrote this in the comment section, but it’s important enough that I’ll post it as an article)

There are several factors about radiation that are generally unknown, so I’ll elaborate.
First, one needs to understand that human body, and other animals and plants that evolved here on Earth, have a built-in mechanism for dealing with radiation damage. If not, they wouldn’t have lasted very long, since radiation is a way of life here. My dosimeter “clicks” frequently enough that I had to turn off sound, and every click means that its small, coin-sized sensor has been hit by a high-energy photon. This means that every piece of our body that is the size of that small sensor gets hit with the same frequency, which means that we are getting constantly pierced by gamma rays. Obviously, this level of radiation is not a problem since our bodies can deal with it. So, how do they deal with it? Gamma rays basically eject electrons from atoms, which in case of atoms that share an electron in their highest orbital means that the molecular bond is broken. I think the cells know how to fix minor damage of this kind, but if it gets too much, something in the cell’s chemistry changes sufficiently that the immune cells recognize it as damaged/foreign, and start attacking it. The cell then dies and its content is disposed as any other waste.
This gives us three corollaries: first, that cancer should never happen if the immune response is healthy, which means that cancer is basically disease of the immune system, which does not perform its normal function of recognizing and attacking damaged cells. The second corollary is that radiation sickness is basically a state when the body is overwhelmed by garbage disposal from all the damaged/destroyed cells. This is why acute radiation damage is so dangerous, and why it’s a rule of the thumb: if enough cells die to overwhelm your kidneys, liver and other organs, you die. If not, you just get very sick during the garbage disposal phase, which, incidentally, is the same thing one suffers when they take antibiotics that are very effective against bacteria: all the garbage from the dead bacteria overwhelms the body. If the antibiotics don’t work, you won’t feel anything at all. The third corollary is that body will deal with radiation damage in a matter of days and weeks; basically, everything that is damaged will be killed off and disposed, except if your immune system is suppressed, in which case you will get cancer. Also, one should absolutely never have sex during this phase, because that’s when the genetically damaged children get conceived. After the body had the time to purge the damaged cells, it’s safe. The disclaimer is that this is empirical data obtained from irradiated men. I don’t know irradiated women handle the damaged ova, because it’s the men who statistically got irradiated and thus were unfortunate enough to provide me with a statistical sample.
Also, and this is not really recognized by science at this point, but I have the empirical data from Chernobyl, the initial burst of high radiation is absolutely deadly, and does exactly what you would expect. However, the long-term elevated doses of radiation seem to be more-less harmless, and this is a shocking datapoint, because there are carp merrily swimming in the super-radioactive lake near the exploded reactor, and they are fine. They are radioactive as all fuck, to the point that their bones make the Geiger-counter scream, but eagles that are supposed to be highly sensitive to the accumulation of heavy metals on top of the food chain are also fine; they eat radioactive carp from the radioactive lake and they are fine. The wolves, also the top of the food chain, are similarly fine, and they have a very healthy population there. Old people who refused to evacuate from the exclusion zone eat radioactive cheese and milk from their radioactive cows, and they are all fine. For the animals, the radioactive exclusion zone is heaven on Earth. As for the mutations, that’s another funny thing – there aren’t any. Radiation doesn’t increase the speed of mutation, because the mutated DNA is recognized as damaged, and is routinely destroyed by the immune system. There was an evolutionary preference for black frogs over the normal ones, because apparently melanin stops gamma rays the same way it stops UV light, and increases survival rate; since those frogs live in the super-radioactive lake, the initial deadly radiation probably preferentially killed the low-melanin frogs. The corollary of this is that one should hide from the initial strong radiation immediately and effectively, but later on the body seems to adapt to the higher amounts of ionizing radiation and is able to cope even with the doses that would be expected to be deadly.
Cancer is actually the least of the problems; cataract, sterility and lethal stress are much more probable, because the population from Chernobyl exclusion zone showed that almost all elderly people who evacuated quickly died from stress-related conditions, while those who remained had no issues whatsoever and lived to very old age. Also, among the highly-irradiated engineers in the station itself the main causes of death are myocardial and cerebral infarctions; I would guess that radiation damages the inner linings of their blood vessels, which likely promotes clotting. That’s the weird thing – nobody seems to get cancer from radiation. However, stress will really fuck you up, especially if you believe all the hype about radiation and if you have to evacuate from your home and basically restart your life.