Following the shock of the 1954 thermonuclear weapon test at Bikini Atoll, Japanese scientists rallied to study the effects of low levels of radiation on life. Given the challenge of generalizing experimental results based on the particularities of different test organisms, research methods, and environments in Japan, geneticists grappled with how to extract reliably universal knowledge about the effects of low doses of radiation. This article aims to sort out the relationship between the 1954 event and subsequent low-dose radiation experiments in Japan, which contributed unevenly to an international corpus of knowledge, including knowledge used to set international radiation safety standards. By analyzing a key documentary source from the popular genetics magazine Iden, the author examines how scientists investigated a biological notion of “repair” or “restoration” during this period of frustration and anger about nuclear fallout. Japanese research of that time can now be understood as having accommodated an antithesis to the linear no-threshold (LNT) model. Today’s biomedical scientists dealing with the 2011 nuclear power plant disaster in Fukushima have inherited the problem of reconciling “event” and “experiment” that postwar Japanese researchers studying low-dose radiation effects grappled with previously. The genba concept is used to compare and theorize how anticipation of new scientific knowledge mediates the epistemic space that forms in response to a radiation event well beyond discussions that assign responsibility about what or who releases, studies, or interprets potentially harmful, negligible, or beneficial radioisotopes in Japan.