I'm working on a story where in 1983 the world went to full on global war and all nuclear power plants blew up either under nuclear fire or by losing power.

I know about the general 30km exclusion zone in Chernobyl and I'm thinking maybe expanding a safe zone slightly around that where survivors for the next centuries avoid the area in fear of radiation, but I'm trying to work out how much of the exclusion zone I can expand with the subsequent wildfires spreading through the exclusion zones.

So really my question is: how much further can fires carry enough radiation to make a zone uninhabitable?

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    $\begingroup$ "how much further can fires carry enough radiation" - so you are specifically asking about spreading with the help of fire? $\endgroup$
    – Alexander
    Jul 28, 2021 at 21:11
  • $\begingroup$ This might be relevant : en.wikipedia.org/wiki/2020_Chernobyl_Exclusion_Zone_wildfires $\endgroup$
    – JonSG
    Jul 28, 2021 at 21:33
  • $\begingroup$ @JonSG yes things like that. It wasn't the first either. But provided there weren't any firefighters to combat that how bad could it get really? $\endgroup$
    – Nierninwa
    Jul 28, 2021 at 22:19
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    $\begingroup$ Specifically for Chernobyl, or for a more general "nuclear power plant"? Because with a number of plants, being on fire wouldn't necessarily spread nuclear contamination - it only did in Chernobyl's case because the graphite moderator could burn. $\endgroup$
    – jdunlop
    Jul 29, 2021 at 1:15
  • $\begingroup$ Are you asking about chernobyl specifically or also about warhead contamination? $\endgroup$
    – John
    Jul 29, 2021 at 1:17

2 Answers 2


The exclusion zone was an administrative decision, balancing risks and needs.

The spread of radiation was not really an issue at these ranges. Once you're over the horizon, at any rate. What matters is the spread of radioactive particles which are then carried on the skin, ingested, or breathed in. Do you know about plans to distribute Iodine in case of reactor accidents? That's to give people non-radioactive isotopes of iodine so that their body does not store the radioactive isotopes.

In an individual reactor accident, the fallout pattern will depend on the weather and the details of the accident. Did the radioactive particles get blown into the air or did they seep into the ground? In a general nuclear war, the fallout patterns of many bombs will create a crazy quilt of very radioactive and not quite so radioactive zones. 5 miles upwind from a reactor may well be safer than 50 miles downwind from a crater (safer, not safe).

  • $\begingroup$ I thought nuclear bombs did not create significant lasting radiation due to the fact that all the fissile material goes up in smoke contrary to the rods of spent uranium in power plants? I mean Hiroshima and Nagazaki aren't exclusion zones, but Fukushima and Chernobyl are. And sure not all of it is dangerous but people would develop superstitions and fear the places that make you sick $\endgroup$
    – Nierninwa
    Jul 29, 2021 at 8:12
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    $\begingroup$ @Nierninwa, there is no "lasting radiation." There are just lasting or non-lasting isotopes in the fallout or wreckage. Those can be from the original nuclear material or from previously non-radioactive materials which got irradiated. A ground burst draws more material into the explosion where it is irradiated, an air burst less so. $\endgroup$
    – o.m.
    Jul 29, 2021 at 10:06
  • $\begingroup$ @Nierninwa: the bombs dropped on Hiroshima & Nagasaki were just fission bombs. Most nuclear weapons these days are thermonuclear devices (hydrogen bombs) which are much more powerful & much more devastating. $\endgroup$
    – user81881
    Jul 29, 2021 at 10:41
  • $\begingroup$ @Fred And much cleaner, so the point about nukes not creating exclusion zones stands. $\endgroup$
    – Rekesoft
    Jul 29, 2021 at 12:09

This map shows the diffusion of radiation from Chernobyl.

enter image description here

As you can see it's all but regularly shaped, strongly influenced by the weather pattern immediately after the incident.

You can also compare it with the similar map produced for the nuclear test in USA

enter image description here

In your case you are adding fires to the scenario: meaning that hot air produced by the fair will lift radioactive dust and have it carried by the winds. Nevertheless the diffusion of that dust will not be uniform and might reach way further than one can think.

  • $\begingroup$ Yes but how far? Is there any evidence how far it can reach? Maybe from the fires in Chernobyl? $\endgroup$
    – Nierninwa
    Jul 30, 2021 at 10:26

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