My takeaways:

1. Blowing off all those atomic bombs during the nuclear age after WWII till 1980 caused a lot of radioactive isotopes to be in the atmosphere.
2. The steel making process uses oxygen from the atmosphere pre 1945 steel is made with minimal isotopes.
3. This low background steel is needed to detect very low levels of radiation. Especially needed for labs and testing for scientific reasons.
4. Since the atmosphere is constantly exposed to radiation the only place on earth to get low background steel is deep in the sea. This whole ship wreckages have become a black market hot bed.

This episode reminds me about the sand black market which I posted about.

Learning about the raw materials needed for the built environment is fascinating!