Steel made after 1945 is slightly radioactive, forcing scientists to salvage metal from WWII shipwrecks for sensitive equipment.

The primary contaminant in modern steel is Cobalt-60, a radioactive isotope released during the Trinity nuclear test in 1945 and subsequent atmospheric testing during the Cold War. Steel production involves the Bessemer process or basic oxygen steelmaking, both of which force large volumes of atmospheric air into the molten metal. This process traps radionuclides within the steel's molecular structure, making the metal itself emit low levels of radiation.For most applications, this radioactivity is negligible and poses no health risk to humans. However, for highly sensitive instruments like Geiger counters, medical whole-body counters, and dark matter detectors, even this tiny amount of background radiation creates 'noise' that drowns out the signals scientists are trying to measure. This has created a high demand for 'low-background steel' which was manufactured before the first atomic blast.The most famous source for this rare material is the German High Seas Fleet, which was scuttled at Scapa Flow in Scotland in 1919. Over 50 ships were sunk, providing a massive reservoir of pristine, pre-atomic steel that has been shielded by the ocean for decades. Salvage operations have recovered thousands of tons of this metal to build components for NASA satellites and deep-sea sensors.As atmospheric radiation levels have declined since the Partial Nuclear Test Ban Treaty of 1963, the necessity for salvaged steel is slowly decreasing. Modern steel plants can now use specialized techniques to reduce contamination, but the steel from WWII-era shipwrecks remains the gold standard for purity. These sunken vessels serve as a finite and historical resource for the most advanced scientific research in the world.