On the very first day (well, arguably) of the Russian invasion of Ukraine, Russian forces took control of the Chernobyl Nuclear Power Plant and ghost city, as well as Pripyat.
I fail to see how is this so strategic for a first-day goal. Is it only their proximity to Kiev and the border to friendly Belarus? Is there nuclear material that can be reused by Russia? Is there anything else still useful in the cities?
This one's pretty simple. Look at where Chernobyl is relative to a map of Ukraine:
It is directly on the shortest possible route from areas friendly to Russia (that is, Belarus) and Kyiv. If you want to capture the Capital and Ukrainian leaders, the fastest route is through the Chernobyl area.
As to concerns about Radioactivity, it's not dangerous on a short or medium term scale anywhere outside of the actual reactor facility and waste storage areas. If the Russian troops set up camp and started farming, or foraging for food in the forests long-term, they might have some health consequences, but there's no concern for military operations.
As early as January, the NYT was reporting that Ukraine was deploying additional troops to the region due to its strategic location:
[T]he shortest route from Russia to Ukraine’s capital, Kyiv, is from the north. And it passes through the isolated zone around the Chernobyl power plant, where the meltdown of a reactor in 1986 caused the worst nuclear disaster in history.
In one of the incongruities of war, that makes Chernobyl an area that Ukraine thinks it needs to defend, forcing its military to deploy security forces into the eerie and still radioactive forest, where they carry both weapons and equipment to detect radiation exposure.
In addition to sitting in the middle of the shortest route to Kyiv, it also holds a river crossing.
After reports of clashes at the site, this question was put to Dr Jack Watling, a research fellow for land warfare at the Royal United Services Institute on BBC Radio 4’s PM program at around 17:39:-
Interviewer: In the last few minutes it’s been reported that the Chernobyl power plant, captured by Russian forces, I don’t understand - it’s not a working power plant is it? Or, what would be the point of getting the Chernobyl power plant - but it does seem something has been going on there this afternoon.
Watling: I mean it’s fairly standard practice that if you’re taking over a country you take over all the critical national infrastructure, and Chernobyl has both symbolic relevance but also you can start playing dirty tricks in terms of, you know, claiming that, I don’t know, the Ukrainians are conducting artillery against it and these kind of things. So you know, you want to seize areas that are symbolically valuable and areas that are valuable from a services point of view, and the Russians will try and do that.
Radio Free Europe, meanwhile, cites an unnamed Russian security source, saying that “Russia wants to control the Chernobyl nuclear reactor to signal to NATO not to interfere militarily”. They also quote Deputy Interior Minister Anton Heraschenko acknowledging the devastation that could occur if the site is damaged:
If as a result of the occupiers' artillery strikes the nuclear waste storage facility is destroyed, the radioactive dust may cover the territories of Ukraine, Belarus and the EU countries
This suggests that the site may have strategic relevance as a forward base that Ukrainian troops dare not attack with artillery fire.
Today's escalation of the conflict is largely about convincing people of the Russian view: that Ukraine should be controlled by Russia.
Controlling the Chernobyl Nuclear Power Plant is one of the better thought-out parts of that. The idea will be to say that Russia is in control of this dangerous place, which would be a threat to much of Europe if it were damaged. This allows Russia to be portrayed as selflessly assuming responsibility, with the (false) subtext that the Ukrainian government was not being responsible. The only people this is likely to be effective on are the Russian population, and people who outsource their political thinking to Donald Trump, but the latter group are significant in American politics.
It was also an easy place to take and to hold, because the Ukrainians would not be fool enough to fight for it, given the potential consequences of using heavy weapons there. It also means that should the Russians start to do badly in the conflict, they have a threat to employ against Ukraine, which would have to live with the consequences of any breach of the containment.
Apart from its strategic significance, mentioned by others, Chernobyl has symbolic importance as a site that is known worldwide and keeps inspiring concerns and investment from abroad. Refusing western collaboration in securing the site or claiming the necessity of such a collaboration can be a useful bargaining pawn in future negotiations.
Strategic significance of the site is not surprizing - power plants are built to be both secure from an outside attack, but also being able to supply with electricity large regions - that is the plant is likely at the geographic point, from which many important population or industrial centers can be easily accessed (at least easily enough for constant surveillance of the high tension line).
