low-background steel

Noun

 * 1) Steel with low inherent radiation levels, suitable for instruments and experiments highly sensitive to.
 * 2) Steel created before 1945, and not contaminated by radioisotopes originating from nuclear bomb tests and explosions, and other nuclear technology radioactivity releases
 * 1) Steel created before 1945, and not contaminated by radioisotopes originating from nuclear bomb tests and explosions, and other nuclear technology radioactivity releases