I don’t know about Chernobyl specifically, but so-called low background steel from before 1945 is harvested specifically for use in radiation sensing applications. See https://en.wikipedia.org/wiki/Low-background_steel

I think most of the radionuclide contamination comes from Cold War atmospheric nuclear testing.

Some low background steel is recovered from sunken battleships!

On a related note - the day the German fleet (which went on to be scuttled at Scapa Flow and to become a source of that low-background steel) must have been quite an incredible sight - possibly one of the largest collection of warships ever (40 battleships, there were only 7 at the Normandy Landings):

https://www.bbc.co.uk/news/magazine-30128199

Yes, this is it, thank you for providing the source, it was an interesting read.

It was from atmospheric testing of nuclear weapons in general, but the last atmospheric nuclear test was conducted in 1980, leaving Chernobyl as the last event to disperse significant nuclear material into the atmosphere. Though, I think the bulk of the radionuclides have decayed enough that there's no longer a need to salvage old WW1 battleships for their low radiation steel. Specifically, the two major "medium-lived fission concerns," caesium-137 and strontium-90 have a ~30 year half-life.

That has to do with atmospheric nuclear weapons testing, not Chernobyl. You can still see some weapons testing isotopes in a 24-hour background count on a high-purity Germanium radiation detector.