Radiation is a workplace hazard that eludes the sensing body, or seems to. After Chernobyl and Three Mile Island, Kai Erickson described radiation as “an invisible threat,” “the very embodiment of stealth and treachery.” The first generation of Canadian nuclear power workers, from their four decades of experience around reactors has a different sense of the matter. They describe a physical awareness of the morphology and topography of radiation, a cultivated bodily knowledge that informed their actions as they produced power. They describe a “feel and a touch for the plant,” framed in theoretical studies, made through attentiveness and alert expectation, honed by being out and about in the station, being its intimate, “listening to its very cries.” By their telling, “doesn't feel right” ceased to be a metaphor about their workplace circumstance, and through study and practice, became a bodily effect, a report from the somatic. Key to work safety for Canadian nuclear workers were close study of the theory of ionizing radiation, adeptness with both the instruments which made radiation apparent and the calculations that made the readings on dials into qualitatively and spatially distinctive workplace presences, and skill in choosing, donning, building, and removing physical barriers between their bodies and radiation fields. Through this knowledge and practice, Canadian nuclear workers came to embody the hazards of the job. This working knowledge of the insensible enabled them to be responsible for their own radiation protection and for the safety of those with whom they worked.