I saw a short story about this somewhere on the internet the other day but I still didn’t get the point…Why are the Chinese, and presumably others, taking steel from the sunken Prince of Wales and Repulse? It seems as it has something to do with nuclear testing, or something?

https://en.m.wikipedia.org/wiki/Low-background_steel

Low-background steel, also known as pre-war steel and pre-atomic steel, is any steel produced prior to the detonation of the first nuclear bombs in the 1940s and 1950s. Typically obtained from ships (either as part of regular scrapping or shipwrecks) and other steel artifacts of this era, it is often used for modern particle detectors because more modern steel is contaminated with traces of nuclear fallout.

uhh, what?

Modern production steel is mildly radioactive due to traces of radioactive isotopes present in the air used to smelt the steel, due to all the various nuclear detonations on Earth since 1945.

This new radioactive steel makes certain types of finely tuned scientific/medical instruments give false readings, so these kind of instruments have to be made from old steel that was produced in the pre-nuclear age and therefore doesn't have this inherent contamination.

The best source for large quantities this old steel is old shipwrecks from the early 20th century (namely WW1 and WW2-era warships), so folks dive down to shipwrecks and cut old steel out of them to reuse.

This is sometimes done legally, like steel recovered with permission from the German Navy fleet that was scuttled off the coast of Scotland after the end of WW1.

But China has recently been accused - and actually caught in the act - of illegally scavenging old steel from ships that were sunk during WW2 in the Java Sea and South China Sea for their own use in making these types of instruments.

It's not only that they're looting steel that doesn't belong to them, but they're also desecrating Allied war graves by doing so.