I tried asking physicists about how much damage can be done by a nuclear power plant in the hands of a bad actor. I wanted to write it into the plot of a story/game I was dreaming up.

The response was ultimately: "way less than you'd think."

https://physics.stackexchange.com/questions/501180/how-can-i...

You asked specifically about water contamination. Water isn’t the most destructive method of spreading radioactive fallout. A massive explosion under an exposed core would do far more damage by spreading fallout through the air.

Like how much more? 100x, 1000x?

I'd say much worse than that. The total fuel release from Chernobyl was only 1.5 - 3.5%, but radiation was detected hundreds of miles away - in the Scottish Highlands for example. The west learned about the accident from Geiger counters in Sweden.

The explosive force of the steam that would have erupted underneath the already exposed reactor is, without a doubt highly debatable. But suppose it only ejected 30% of total fuel - about 20x what happened in Chernobyl. Chernobyl's exclusion zone is - today - about 1000 square miles. Would it have to be 20x that? I don't know. Would very much depend on the weather probably.

The wikipedia article on the disaster is a pretty good introduction to the topic.

https://en.wikipedia.org/wiki/Chernobyl_disaster#Spread_of_r...

To put some numbers in perspective: the punchline was that you could contaminate 3 million liters of water. That sounds like a lot, but that's roughly how much NYC consumes in a minute.

>Chernobyl very nearly was that serious.

No it wasn't. At no point did Chernobyl threaten to make 'much of Europe and the Middle East' uninhabitable for hundreds of years. About the worst that could have happened with Chernobyl happened. There just wasn't enough radioactive material in the reactor to have that big of an impact at that scale, and saying this does not invalidate the regional devastation that it did cause.

No, it actually could've been much worse: https://www.businessinsider.com/chernobyl-volunteers-divers-...

I don't think so. I'm trying to find some sources, and it seems like all the clickbait articles reference a book by some guy named Andrew Leatherbarrow, "Chernobyl 01:23:40" (and Leatherbarrow is just some guy without any particular expertise). I can't find any justification for why there was a chance that millions would have died and half of Europe was almost rendered uninhabitable. It smells like clickbait bullshit.

I actually agree with you that the article sounds click-baity, unfortunately, HBO has made it so much harder to get good information regarding Chernobyl on the Internet nowadays[0].

Just one of four reactors "melted down". I'm no expert, but I imagine the worst possible is all four reactors literally exploding simultaneously, or one after the other in a rapid chain reaction, or something like that.

[0]: https://www.forbes.com/sites/michaelshellenberger/2019/05/09...

No, nearly all the uranium was contained at Chernobyl. If it had melted down a little faster it could have hit a flooded basement before it was drained. The steam explosion would have distributed uranium dust over potentially thousands of miles.

Do you have a source for the likelihood of that, as well as the likelihood of it rendering those thousands of miles uninhabitable?

I think this theory has been mostly debunked, ironically because it pretty much happened in multiple reactors at fukashima without that disastrous result.

There was no core breach at all in Fukushima.

It didn't fully breach the concrete floor, but it breached the pressure vessels in at least 2 reactors and fell into a "basement" of pooled water, without the catastrophic stream explosion hypothesized for Chernobyl.