This is an excellent example of innovative and voluntary compliance. Steel mills can run into problems if they receive radium-contaminated pipes as scrap. Petroleum deposits in the U.S. contain radium, a naturally occurring radioactive element. As the petroleum flows through pipelines, radium deposits onto the lining of the pipes. Sometimes significant levels of radium can be detected in the scale.
Mills also receive unmarked radioactive gages.
Gages containing radioactive materials are used in many industrial and household applications. Many smoke detectors have gages containing americium-241, an isotope not readily detected by traditional monitors. If steel mills don't identify these contaminants, the smelting can cause contamination of the steel and radioactive releases into the environment. The problem affects steel mills and scrap yards alike. In either of these scenarios, the public loses.