The issue with radiation in the steel is due to atoms in the air when the steel is being cast. They are mixed into the material when it's molten.
The steel being made before 1945 is what protects against radiation.
Storage at the bottom of a river just means that it hasn't been found and recycled or scrapped already. It would still be "low background" if it had been stored elsewhere, exposed to air or not. The exposed surface layer can always be cleaned off or ground away. But what permeates the material is there for a long time.
The steel being made before 1945 is what protects against radiation.
Storage at the bottom of a river just means that it hasn't been found and recycled or scrapped already. It would still be "low background" if it had been stored elsewhere, exposed to air or not. The exposed surface layer can always be cleaned off or ground away. But what permeates the material is there for a long time.