Let's say you need to make a very sensitive tool to detect radiation. Maybe you need to use it for medical purposes, detecting specific isotopes as they move through a human body. Or perhaps it's for the tools to detect radiation to prevent dirty bombs and nuclear smuggling. Wherever your radiation is, if you want super accurate measurements of it, you have to make your tools out of low-background steel, and that's hard to get.
Here's the problem with new steel: It's made in a radioactive environment. The very air we breathe contains little molecules leftover from the approximately 2,000 nuclear tests conducted since 1945. Irradiated coral from Bikini Atoll tests, snow melted by the Tsar Bomba, and air particles in the wrong spots during the development of the Genie air-to-air rocket are all still radioactive.
It's not enough to be a big threat to life around the world, but disasters like those at Chernobyl and Three Mile Island have created background radiation in the atmosphere that will last for centuries. And making steel requires that air is passed through molten steel. If that air has any radioactive molecules in it, which it often does, then the steel will be slightly radioactive.
That doesn't make it useless for detecting radiation. But any radiation in the steel makes the resulting device less sensitive. It's like if you're trying to listen for a distant sound while a band plays. The louder and closer the band is, the harder it will be for you to hear a distant or faint sound. A radiation detection device with radioactive steel in it will never be able to detect radiation that's beneath the threshold its own components put out.
But steel can last. And any steel manufactured before the first nuclear tests in July 1945 is filled with low-background radiation steel. Basically, since it has much fewer radioactive particles in it, it can detect radiation at much lower levels. So, if you need to run a radioactive dye through a medical patient, you can use a much lower level of radiation if the detector is made with low-background steel.
Same with scientific and law enforcement instruments.
But how to get low-background steel today? If you mine ore now, melt it down, and mix it with limestone, you'll be most of the way through making low-background steel. But you also have to pass air through it. And the only air available has radiation in it.
So, instead, you could go find steel manufactured before 1945. Preferably steel that wasn't exposed to the air during the testing or in the years immediately afterward.
You read the headline. You know where this is going.
Sunken warships have literally tens of thousands of tons of steel in them, and the water has shielded them from radiation for decades.
So, with the consent of governments, some warships have their steel removed. It's done carefully both to prevent contaminating the metal as well as to avoid disturbing the dead. And it's not just steel. A British warship from before the Revolution had a large amount of lead that is now maintained by the University of Chicago.
It's even been suggested that some illegal salvage efforts were conducted by black market outfits looking to make millions by stealing entire ships off the ocean floor. And at least two British ships lost in World War II have disappeared, though some researchers think it was more likely straight steel salvage. It doesn't appear the thieves had the wherewithal to properly protect the salvage from modern radiation, so it was probably sold as normal scrap.
So the thieves disturbed the grave of thousands of sailors and contaminated tens of thousands of tons of rare low-background steel.
And some artifacts from long before World War II are now being used for scientific experiments. Historians and scientists have a tense tug of war when it comes to lead from ancient Chinese and Roman sites and wrecks.