In France, the first industrial-scale nuclear reactors were built by the French Atomic Energy Commission at Marcoule during the fifties. Most of the staff who were recruited at the time knew nothing about such risks, and their inexperience made it difficult to protect them. In response, the Radiation Protection Service (SPR) developed a worker education programme. Its implementation drew upon the artistic talents of Jacques Castan, a draftsman of the SPR. This study highlights its contribution to worker education and showcases how its illustrations have captured the imaginary of the radiation protection. The focus on a series of posters dedicated to dosimetry devices identifies three elements—anxiety, anthropomorphism, sublimation—which represent an ambiguous relationship to radioactive risk. Such ambiguity can be compared to Girard’s definition of the “sacred”.