[HyperSane]

Reminds me of the way nuclear explosions contaminated all steel with radioactive fallout. For applications that require the lowest possible radiation levels they have to use steel created before the first nuclear bomb was detonated.

[kuhewa]

We use where bomb radiocarbon appears along the rings of a fish's earstones to validate ring-counting to age long-lived species.

[HyperSane]

We should detonate nukes at precise intervals like every 1, 5, or 10 years. Maybe with distinct radio-nuclide signatures.

[MereInterest]

That’s true, but it’s more the timescale that helps. There’s a decent amount of radioactive background produced by cosmic rays hitting the upper atmosphere, much of it as gaseous elements that are easily incorporated into steel while smelting. It isn’t harmful at that level, but you do need to wait a few decades for those to decay away.

World War Two is rather convenient in that respect, as there are large quantities of steel that were left to sit around for several decades after those ships sank.

It’s been a while since I’ve done low-background gamma-ray spectroscopy, but I believe there were some setups that went even further, using lead that had been smelted by the Romans. That way, any contamination present at the time of smelting would have a few thousand years to decay away.

[HyperSane]

Wikipedia says that for the lowest radiation levels high-purity copper is used.