Radioactive Warning Symbol - Meaning, History, and Safety Use #3770108 (License: Personal Use)

This image shows the internationally standardized radioactive warning symbol, known as the trefoil, consisting of three black blades arranged at 120-degree angles around a central circle on a bright yellow field. Adopted in 1946 at the University of California, Berkeley, it was formalized by ISO 361 and IAEA standards for use on containers, equipment, and facilities handling radioactive substances. Its high-contrast design ensures immediate recognition even from a distance or under poor lighting.

Used on nuclear facilities, medical radiology departments, transport containers for radioactive isotopes, and laboratory signage; matches user intent for safety education, regulatory compliance, emergency response training, or academic reference.